Cell as unit of life

Jasmin

1

4 ideas of cell theory:y All living organisms are made up of one or

more cells. y New cells are formed by the division of preexisting cells. y Cells contain genetic material of organism which is passed from parent to daughter cells. y All metabolic reactions take place within cellsJasmin 2

Cell as a unit of lifeCELL THEORY A cell is a basic unit of life. Virtually all organisms consist of cells and cell products. This generalization is called CELL THEORY. The cell theory-credited to the European biologist: a) Mathias Schleiden b) Theodor Scwann in 1838-1855Jasmin 3

2 types of cells:1) Prokaryotic cells 2) Eukaryotic cells

Prokaryotic cellsy y

y

Bacteria and cynobacteria Prokaryote is derived from a greek word pro : before karyon: nucleus Signifying the absence of true nucleus in the cell meaning (DNA) in the cytoplasm, is not contained in a nuclear membrane or naked circular DNA, which is characteristic of prokaryotic cells,

Jasmin

4

Jasmin

5

Jasmin

6

Characteristics of prokaryotic cellsy Nucleoid- region where the cells DNA is located (not enclosed by a y

y y y y y

y

membrane). The cell has a single circular chromosomes in the form of a ring of deoxyribonucleic acid(DNA) in the cytoplasm, not contained in a nuclear membrane. Cells contain ribosomes (site of protein synthesis) Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance. The cell lacks of mitochondria, chloroplast and complex structured flagella. The cell has a wall of distinct composition containing the molecules of polysaccharide cross-linked by-chains of amino acids called: peptidoglycan - gives strength and perform the same function as cellulose. The cells are extremely small(1-10 um) in diameter.Jasmin 7

y The cell membrane of bacteria is a selectively permeable barrier between the inside and outside of the cell. y The cell membrane is invaginated to form mesosomes- site of respiration. Mesosomes are rosette-like clusters of folds in the plasma membrane, protruding toward the interior of the cell. y These structures are important in the performance of the aerobic parts of aerobic cellular respiration. y A key part of this process requires a lot of membrane surface, and mesosomes greatly increase the membrane surface of the cell. y Thylakoids are found only in photosynthetic prokaryotic cells, such as the cells of blue-green algae and the purple photosynthetic bacteria. y Photosynthesis is a vital function which requires a lot of membrane surface, and the long, thin thylakoid surfaces provide that area.Jasmin 8

y Tubular or flattened thylakoids containing chlorophyll and other pigment are present in the cytoplasm of photosynthetic bacteria. y umerous pili cover the surface of some bacteria. y They are fine threads of the protein. y Some of them may help the bacterium to stick to a solid surface. y Some bacteria have flagella which are used for locomotion. y Cells enclosed by jellylike outer coating- capsules (found in bacteria) y The capsule is composed of rather amorphous polysaccharide material similar to mucous. y This material is hygroscopic, meaning that it has a great capacity to retain water.Jasmin 9

Jasmin

10

eukaryotic celly 2 types of eukaryotic cells:

1) plant cell 2)animal cell y Plant, animal, fungi i.e. the majority of living things y The name derives from: eu =true/good karyon=nucleus

Jasmin

11

eukaryotic animal cell

Jasmin

12

Eukaryotic animal celly Animal cell contains protoplasm(nucleus & cytoplasm)

surrounded by a thin plasma membrane. y Cytoplasm contains variety of organelles such as mitochondria suspended in the cytosol (semi fluid medium) y The most prominent organelle is nucleus- containing chromosomes.

Jasmin

13

Jasmin

14

EUKARYOTIC PLANT CELL

Jasmin

15

eukaryotic plant celly The plant cell is surrounded by a fully permeable

external cell wall- made of cellulose, other polysaccharide & protein. y Its also surrounded by a plasma membrane (on the inside of the cell wall) & contains a nucleus, ribosomes, ER, Golgi apparatus & microtubules. y The plant cells also contain chloroplast which carry out photosynthesis. y Cytoplasm, organelles and nucleus are usually pushed to the periphery due to the presence of large central vacuole.Jasmin 16

Jasmin

17

The differences betweenProkaryotic Cell(Bacteria, cynobacteria)1) Extremely small -usually between 0.5-10 um in diameter. 1) 2)

Eukaryotic Cell(green plants, fungi)Larger cell -usually between 10-100 um in diameter. - Nucleus with distinct bounding membrane perforated by nuclear pore -DNA in linear chomosomes and combined with protein histones

2) -Nucleus absent - Circular DNA helix in cytoplasm - DNA not supported with basic protein histones 3)Cell wall present containing peptidoglycan 4) -Few organelles. - No membrane-bounded organelle such as mitochondria & chloroplast. 5) Ribosomes- smaller (70s) 6) Some cells have simple flagella without microtubules.Jasmin

3) Cell wall contain cellulose 4) - Many organelles. - presence of double membrane-bounded organelles such as nucleus, mitochondria & chloroplast in plant and algae. 5) Ribosomes- larger(80s) 6) Some cells have complex cillia and flagella with 9+2 arrangements of microtubules.18

Some eukaryotic cells have complex cillia and flagella with 9+2 arrangements of microtubules.

DNA combined with protein histones in chromosomeJasmin

Ribosomes

19

Differences betweenAnimal cell 1) No cellulose cell wall, only plasma membrane and irregular in shape 2)No plasmodesmata & pit. 3) No chloroplast 4)Small temporary vacuole 5) Centriole and lysosome present 6)Carbohydrate storage in form of glycogen granules 7)Some have cilia and flagella 8) Smaller in size ( 20um diameter) Plant cell 1) Have rigid cell wall & plasma membrane and regular in shape 2) Plasmodesmata and pit present in cell wall. 3) Presence of chloroplast 4) Large permanent central vacuole 5) Centriole and lysosome not present 6)Carbohydrate storage in form of starch granules 7)No cilia and flagella 8)Larger in size ( 50 um in diameter)

Jasmin

20

Levels of Structural Organization:Chemical Level - atomic and molecular level Cellular level - smallest living unit of the body Tissue level Group of cells and the materials surrounding them that work together on one task. 4 basic tissue types: epithelium, muscle, connective tissue, and nerve Organ level - consists of two or more types of primary tissues that function together to perform a particular function or functions or a no. of different tissues working together as a functional unit. Example: Stomach Inside of stomach lined with epithelial tissue Wall of stomach contains smooth muscle Nervous tissue in stomach controls muscle contraction and gland secretion Connective tissue binds all the above tissues together System - collection of related organs with a common function, sometimes an organ is part of more than one system Jasmin 21 Organismic level - one living individual

LEVELS OF ORGANIZATION

Jasmin

22

MAJOR LEVELS OF ORGANIZATION IN LIVING ORGANISMS

Jasmin

23

PLANT TISSUEyPlant tissue are divided into 2

main groups:y y

a) meristematic tissues b) permanent tissuesJasmin 24

Jasmin

25

Meristematic Tissues (Meristems)y Nature Meristematic tissues are composed of cells that divide y y y y y y

continuously. The cells are spherical, oval, polygonal or rectangular . The cell wall is thin and made up of cellulose. The cells are closely arranged without inter-cellular spaces. Cytoplasm is abundant and nuclei are large. Vacuoles are absent and if present, very few. Occurrence Found in growing tips of root and shoot Found in the vascular cambium of dicot trees just beneath the bark. They are responsible for the increase in diameter of the stem. Function The main function of meristematic tissue is to continuously form a number of new cells and help in growth.Jasmin 26

MERISTEMATIC CELL

MERISTEM CELLS

Jasmin

MATURED PLANT CELL

27

Jasmin

28

Jasmin

29

Jasmin

30

Permanent tissue

Jasmin

31

Jasmin

32

Jasmin

33

Permanent tissuey y It is the main/ ground tissue in the plant body, occurring in almost all regions. y Living cells. y These cells are usually spherical or oval in shape. Sometimes the cells may be elongated. y Very rarely, the cells become irregular in shape. y They are usually loosely arranged with prominent intercellular spaces. y Have thin wall containing cellulose, hemicellulose and pectin. y If they contain chlorophyll they are known as chlorenchymaJasmin 34

Parenchyma

.

Every cell has a large vacuole in the centre y A prominent nucleus is seen situated just above the vacuole. y Parenchyma is commonly described as a simple, living, storage tissue.y

Jasmin

35

Modification of parenchymay Parenchyma tissues can be modified to form speciallised cell to carry out

specific function. y These cell e.g. epidermis, mesophyll, endodermis and pericycle.epidermis One cell thick and cover the whole plant body. Fn: protection of inner tissue Column shaped cell( palisade ) or isodiametric cell (spongy) containing chloroplast to carry out photosynthesis a layer of single cells (having casparian strip that is impervious to water) that surround vascular cylinder in roots and stem Fn; to control amount of water moving through it into vascular cylinder. A layer of parenchyma cell found in root found between endodermis and vascular cylinder. Fn: produce root branches and root cambium

mesophyll

endodermis

pericycle

Jasmin

36

Modification of parenchyma

Jasmin

37

Pericycle is a layer of parenchyma cell found in root found between endodermis and vascular cylinder. Fn: produce root branches and root cambium

Jasmin

38

COLLENCHYMA The cells are elongated and are circular, oval or polygonal in cross-section Cell wall is unevenly thickened with cellulose at the corners Nucleus is present and hence the tissue is living Vacuoles are small Intercellular spaces are generally absent

Jasmin

39

y Found in herbaceous plant under the skin i.e. below

Occurrence of collenchyma

the epidermis in dicot stems, midrib of leaves and leaf petiole. y Provide mechanical support to herbaceous plant stems and leaves. y Being extensible, these cells readily adapt themselves to the rapid elongation of the stemJasmin 40

There are 2 types of sclerenchyma: y 1) sclerenchyma fibres y 2) sclereid( stone cells)y Sclerenchyma fibre y Nature The cells are long, narrow, thick and lignified, usually pointed at both y y y y

ends ( tapering end) The cell secondary wall is evenly thickened with lignin and sometimes is so thick that the cell cavity or lumen is absent Nucleus is absent and hence the tissue is made up of dead cells They have simple, often oblique pits in the walls The middle lamella i.e. the wall between adjacent cells is conspicuous coconut, their length varying from 1 mm to 550 mm. and elasticity to the plant body.Jasmin

y Occurrence Found abundantly in stems of plants like hemp, jute and y Function Gives mechanical support to the plant by giving rigidity, flexibility

41

y Sclereidsy These are special sclerenchymatous cells found y y y y y

in the cortex, pith, phloem, hard seeds, nuts and stony fruits. The flesh of pear and guava are sometimes gritty due to the presence of sclereids. These cells are thick walled, hard and strongly lignified. They are isodiametric, polyhedral, slightly elongated or irregular in shape. Simple branching pits are present. function : is to give firmness and hardness to the part concern.Jasmin 42

Jasmin

43

Jasmin

44

Complex Tissuesy Complex tissues are made up of more than one type of

cells and they work together as a unit. y They transport water, salt and prepared food material to various parts of the plant body. y Complex tissues are of two types: 1)Xylem 2)Phloem Xylem and phloem are also called vascular tissues and together they constitute the vascular bundles.Jasmin

45

VASCULAR TISSUES

Jasmin

46

Jasmin

47

Xylemy Xylem or wood is a conducting tissue and is composed

of elements of different kinds. y They are: 1) Tracheids 2) Vessels 3) Xylem parenchyma 4) Xylem sclerenchyma

Jasmin

48

Components of xylem tissueXylem Fibres y They are represented by the dead sclerenchyma fibers that are found in between the vessels and the tracheids. y They are meant for providing mechanical support to the essential elements. Xylem Parenchyma y This is the only living component in the xylem tissue. y It is represented by groups of parenchyma cells that are found in between the vessels and the fibers. They are meant for storage of reserve food.Jasmin 49

XYLEM

PHLOEM

Jasmin

50

Tracheidy They are found abundantly in pteridophytes, y y y y

gymnosperms and primitive angiosperms. In these groups of plants, the tracheids represent the most active water conducting elements. In advanced angiosperms, the tracheids are found restricted to leaf margin and leaf tip. The tracheids are elongated, dead cells, with tapering ends. They are characterised by the presence of a thick cell wall consisting of primary wall and a secondary wall.Jasmin 51

y The primary wall is composed of cellulose where as the secondary wall is made up of lignin. y There is a spacious lumen that extends throughout the length of the tracheid. y In some cases, due to the deposition of lignin, the primary wall develops numerous concave depressions called pits. y When pits are present, the tracheid is described as pitted and when pits are absent, it is described as simple tracheid.Jasmin 52

Jasmin

53

Xylem vesselsy They are the most active water conducting elements in y y y y y

y

y

all higher angiosperms. The vessels are found arranged parallel to each other, extending from one end of the plant body to another. The vessels are long cylindrical dead cells when mature. The diameter of vessel is bigger than tracheid Cell wall of vessels consists of a primary wall and a secondary wall. The primary wall is made up of cellulose where as the secondary wall is made up of lignin. There is a spacious lumen that extends throughout the length of the vessels The deposition of lignin in the secondary wall is not always uniform. As a result, the xylem vessels exhibit different types of secondary thickenings. On this basis, xylem vessels can be distinguished into five types.Jasmin 54

Types of Xylemy Xylem can be distinguished into two types namely 1) Primary xylem 2) Secondary xylem Primary Xylem Primary xylem is the xylem that is formed during normal growth. It is a derivative of primary meristem

In the primary xylem, two types of xylem vessels can be distinguished, namely a) protoxylem and b)metaxylem.Jasmin 55

y Protoxylem is the first formed vessels to develop just behind the apical meristem. y In protoxylem vessels lignin is deposited in ring form to form annular vessels or in spirals to form spiral vessels y Annular and spiral can be stretched to provide support during elongation and growth or young stem & roots. y When growth proceeds new vessels are formed metaxylem. y Metaxylem have wider lumen and it cannot be stretched but can transport more water. y 3 form of metaxylem: a) scalariform b) reticulate c) pitted.Jasmin 56

XYLEM VESSELS CAN BE DISTINGUISHED INTO FIVE TYPES ACCORDING TO THEIR THICKENINGS. B.Annular vessels in which the secondary thickening is in the form of rings placed more or less at equal distance from each other. y C.Spiral vessels in which the secondary thickenings are present in the form of a helix or coil. y D.Scalariform vessels in which the secondary thickenings appear in the form of cross bands resembling the steps of a ladder. y E .Reticulate vessels in which the secondary thickenings are irregular and appear in the form of a network. y F and G.Pitted vessels in which the secondary thickenings result in the formation of depressions on the primary wall called pits.Jasmin 57

The cellulose cell walls of xylem vessels are greatly thickened with lignin, forming various patterns of lignification. The early protoxylem shows annular (rings) or spiral lignification. Metaxylem, which matures after the stem has finished elongating, shows pitted or reticulate lignification, with walls mostly lignified except for pits or irregular areas of unthickened wall. Both annular and reticulate patterns of lignification are clearly visible in these images.

Jasmin

58

y Differences between protoxylem and metaxylem

Jasmin

59

Secondary Xylem y Secondary xylem is the xylem that is formed during secondary growth. It is derivative of secondary meristem. It is a characteristic feature of only dicots. y Secondary xylem is commonly known as wood. It is of commercial importance since it is extensively used in the manufacturing of doors, windows and furniture.

Jasmin

60

phloemy

Phloem is a complex tissue composed of 4 different cells: a) sieve tube b) companion cell c) sclerenchyma fibre d) phloem parenchyma cell

Jasmin

61

Jasmin

62

Jasmin

63

Jasmin

64

Sieve Tubesy

They represent the most active food conducting elements in the phloem tissue. The sieve tubes are found arranged parallel to one another from one end of the plant body to another.p l a t e .

Each sieve tube is formed by a series of hollow, cylindrical cells called sieve tube cells arranged one above the other. The sieve cells are separated from each other by horizontal perforated plates called sieve plates. The sieve cells communicate with each other through the sieve plates. Each sieve cell has a thin cell wall, which is composed of only cellulose. The cell cytoplasm forms a number of projections called cytoplasmic thread or strands extending towards the sieve plate. The nucleus is absent.Jasmin 65

Differences between xylem& phloem

Jasmin

66

y Animal tissue can be divided into 4 main group based on their structures:

Animal tissues

Jasmin

67

Jasmin

68

Jasmin

69

Epithelial tissuey Epithelial tissue (epithelium) is the simplest. y It is a vascular tissue and develops from all the three primary germ layers. y Epithelial cells are almost compactly arranged and have abundant cytoplasm

with prominent nucleus. y It form the external surface of the body and cover inner surfaces of organs. y Epithelium can be distinguished into: 1)simple, 2)stratified 3)pseudostratified

y Simple epithelium consists of a single layer of cells on a basement membrane. y It is further distinguished into:

a) squamous, b)cuboidal, c) columnar d)glandularJasmin 70

Jasmin

71

Diferrent types of simple epithelial tissue & stratified tissue

Jasmin

72

Jasmin

73

Stratified epithelium has more than one layer of cells on a basement membrane. It can be further differentiated into : y 1)stratified squamous, y 2)stratified cuboidal, y 3)stratified columnar Pseudostratified epithelium has a single layer of cells on a basement membrane giving a false appearance of many layers

Jasmin

74

Structure and function of epithelial celltype Simple epithelium a) Simple squamos epithelium Thin flattened with central nucleus .arranged as single layer. Polygonal in shape Lining of blood vessel, air sacs of lungs, Bowmans capsule n loop of Henle Exchange of material through diffusion. Protect underlying tissue structure location function

b)Simple cuboidal epithelium

Single layer. Cuboidal in shape. Nucleus located in centre. Some have microvilli on upper surface for absorptionJasmin

Lining of many duct eg. Salivary n pancreatic duct, proximal n distal convoluted tubules n thyroid

Secretion & absorption

75

c)

Simple columnar epithelium

Columnar in shape. Oval nucleus located at the base. The free end of cell surface has microvilli. It is associated with goblet cell which secrete mucus Consist of one layer of cell with all attached to the basement membrane. Not all cell have free surface. Appeared as multilayered. Apical surface may have ciliaJasmin

Lining of digestive tract, upper part of respiratory tract, uterus & oviduct

Secrete mucus, digestive juices , Absorption, Protection , Movement of mucus.

d)Pseudo stratified epithelium

Lining trachea, bronchus and nasal passages

Cilia on apical surface move fluid to pharynx for swallowing. Goblet cell secrete mucus to trap dust and also act as lubricant76

Stratified epithelium a) Stratified squamos epithelium Made up of many layers The cell attached to basement membrane form germinative layer that give rise to new cell through mitosis Consist 2 to 3 layers of cells. Outer skin, mouth anus & vagina. The outer layer of skin often subjected to abration so it become thick & consist of dead cells. Sweat duct Protective layer

b)Stratified cuboidal epithelium

Transport.

Jasmin

77

Stratified columnar epithelium

Consist of 3 to 4 layers of cells. Cells can be modified in shape under condition

Salivary duct , lining the inner surface of urethra.

transport

Jasmin

78

Glandular epitheliumy Contains secretory cells y Example is goblet cells which secrete

mucus. y Multicellular glands contain specialised secretory cells y There are 2 types of glands: 1) exocrine gland 2) endocrine glands

Exocrine glands y secrete their products onto a free epithelial surface, typically through a duct (tube). y E.g.: salivary glands, digestive glands, sweat glands & sebaceous glands.Jasmin 79

Endocrine glandsy Endocrine glands lack ducts. y These glands release their products, called hormone, into the interstitial fluid

(tissues fluid) or blood; hormones may be transported to other parts of the body by the circulatory system.

Jasmin

80

y Protection Epithelial cells of the skin protect underlying tissue from mechanical injury, harmful chemicals, invading bacteria and from excessive loss of water. y Sensation Sensory stimuli penetrate specialised epithelial cells. Specialised epithelial tissue containing sensory nerve endings is found in the skin, eyes, ears, nose and on the tongue. y Secretion In glands, epithelial tissue is specialised to secrete specific chemical substances such as enzymes, hormones and lubricating fluids. y Absorption Certain epithelial cells lining the small intestine absorb nutrients from the digestion of food.Jasmin 81

Overall Functions of Epithelial Tissue

Sweat is also excreted from the body by epithelial cells in the sweat glands.

Specialised epithelial tissue containing sensory nerve endings is found in the skinJasmin 82

Epithelial tissues in the kidney excrete waste products from the body and reabsorb needed materials from the urine. Sweat is also excreted from the body by epithelial cells in the sweat glands. y Diffusion Simple epithelium promotes the diffusion of gases, liquids and nutrients. Because they form such a thin lining, they are ideal for the diffusion of gases (eg. walls of capillaries and lungs). y Cleaning Ciliated epithelium assists in removing dust particles and foreign bodies which have entered the air passages. y Reduces Friction The smooth, tightly-interlocking, epithelial cells that line the circulatory system reduce friction between the blood and the walls of the blood vessels.y Excretion

Jasmin

83

Simple epithelium promotes the diffusion of gases, liquids and nutrients. Because they form such a thin lining, they are ideal for the diffusion of gases

Jasmin

Ciliated epithelium assists in removing dust particles and foreign bodies which have entered the air passages.

84

ervous tissuey It is a highly specialised animal tissue that exhibits two unique y y y y y y

properties 1) irritability (capacity to respond to the stimulus) and 2)conductivity (capacity to transfer the response from one region to another). The nervous tissue is composed of two types of cell called: A) neurons B) neuroglial cells. Neurons are also known as nerve cells. They represent the structural and functional units of the nervous tissue. Neuroglial cells are unspecialised supporting cells which nourish the neurones.

Jasmin

85

3 different types of neuronesNeurones lying entirely within the CNS that connects a sensory to a motor neurone neuron. 2)Afferent Neurones -Also known as sensory neurones, that carry impulse towards the CNS. 3)Efferent Neurones - These nerve cells are also known as motor neurone carry signals or impulse from the CNS to the cells in the effector organ such as muscle. 1) Interneurones -

Jasmin

86

Motor neurone

Sensory neurone

Jasmin

87

NEUROGLIA CELLS

Jasmin

88

Structure of neurone a) A neurone has cell body which contain nucleus and other organelles. b) It has extensions called 1) dendrites that receive incoming impulse 2) axons usually longer than dendrites that convey impulse to other neurones

Axon is surrounded by plasma membrane and contains axoplasma. Some axon are covered by myelin sheath formed by Schwann cell The small uncovered parts between the schwann cells are Jasmin called nodes of Ranvier

89

Muscle tissuey Muscle is a very specialized tissue that has both the ability to contract and the ability to conduct electrical impulses. y Muscles are classified both functionally as either : y 1) voluntary

2) involuntary and structurally as either striated or smooth. From this, there emerges three types of muscles: a) smooth involuntary (smooth) muscle, b)striated voluntary (skeletal) muscle c)striated involuntary (cardiac) muscle.

Jasmin

90

Jasmin

91

Jasmin

92

Smooth muscley y y y y y

y

These are smooth, involuntary muscles. Each muscle fibre is a long, narrow, spindle shaped tapering cell. The cell is uninucleate. Delicate threads called myofibrils run longitudinally through the cell. These muscles are found in the walls of the alimentary canal, and internal organs. Unstriated muscles cause slow and prolonged contractions, which are involuntary i.e. not under the control of the will. In the alimentary canal they cause movement of the food and in the blood vessels they help the blood to flow. Jasmin

93

Skeletal muscley Muscle fibers are y y y y y

y

multinucleated, with the nuclei located just under the plasma membrane. Most of the cell is occupied by striated, thread-like myofibrils. Within each myofibril there are dense Z lines. A sarcomere (or muscle functional unit) extends from Z line to Z line. Each sarcomere has thick and thin filaments. The thick filaments are made of myosin and occupy the center of each sarcomere. Thin filaments are made of actin and anchor Jasmin Z line. to the

94

Jasmin

95

Jasmin

96

Cardiac muscleCardiac muscles are extensively present in the heart. They show characteristics of both striated and unstriated muscles. They are composed of non-tapering cells with faint cross-striations. Each cell contains one or two nuclei. The cells are cylindrical and branched. The function of the cardiac muscle is to rhythmically contract and relax throughout life without fatigue and to pump the blood and distribute it to the various parts of the body.Jasmin 97

Differences between 3 types of muscleskeletal location Attached to bones cardiac Wall of heart smooth Wall of stomach, intestine, blood vessels involuntary absent Elongated, spindled shape and tapered at the end one centre slow

Types of control striation Shape of fibers

voluntary present Elongated and cylindrical

involuntary present Elongated, cylindrical and branched forming network . 1 or 2 centre intermediate

No of nucleus per cell Position of nuclei Speed of contraction

multinucleated periphery Most rapid

Jasmin

98

Jasmin

99

adipose

Dense fibrous connective tissue

Loose connective tissue

Connective tissue

haemopoietic

s eletal

cartilage

bone bloodJasmin

plasma100

Jasmin

101

Connective tissuey Made up of variety

of cell embedded in a large amount of intracellular matrix and fibers y It protects , support the body and internal organs

Jasmin

102

Cartilagey Cartilage is a type of connective tissue which is

tough, semi-transparent, elastic ,flexible and is surrounded by fibrous tissue called perichondrium.

y The matrix of cartilage is called chondrin which

contain ground substance consisting mainly of glyco-protein material, called chondroitin sulphate. y The matrix is also composed of collagenous fibers and/or elastin fibers.Jasmin 103

The cartilage contains speciallised cells called chondrocytes which lie scattered in the matrix . Their precursors, are known as chondroblasts . They are small cells with an oval nucleus found in small chambers or cavity called lacunae. The cells are grouped into small clusters in groups of 2 or 4 or 8.

chondroblasts .

chondrin

lacunae.

Jasmin

104

y Cartilage is avascular (contains no

y

y y y

y

blood vessels) and nutrient diffused through the matrix to nourish the chondrocytes. Thus, compared to other connective tissues, cartilage grows and repairs more slowly. Cartilage serves several functions, including 1) providing a framework for deposition of bone tissue. 2) supplying smooth surfaces for the movement of articulating bones. Cartilage is found in many places in the body including the joints, the rib cage, the ear, the nose, thebronchial Jasmin tubes and between intervertebral discs.

105

y Cartilage is classified in three types:

1) hyaline cartilage 2) fibrocartilage/ white fibrous cartilage, 3) elastic cartilage, which differ in the relative amounts of these three main components.

Jasmin

106

3 Types of cartilageHyaline cartilageis a rather hard, translucent material rich in collagen and glycoprotein material. It covers the end of bone to form the smooth articular surface of joints. It is also found in the nose, the larynx and between the ribs and the sternum..Jasmin 107

yFibrocartilagey Fibrocartilage is

characterized by a dense network of collagen. y It is a white, very tough material that provides high tensile strength and support. y It contains more collagen and less glycoprotein material than in hyaline cartilage. y It is present in areas most subject to frequent stress like intervertebral discs. Jasmin

108

ELASTIC CARTILAGE,

Elastic cartilage contains large amounts of elastic fibers (elastin) scattered throughout the matrix. It is stiff yet elastic, and is important to prevent tubular structures from collapsing. Elastic cartilage is found in the pinna of the ear, in tubular structures such as the auditory (Eustachian) tubes, in the epiglottis.Jasmin 109

Elastic cartilage

y Bone is a hard and rigid tissue

bone

which is covered by a layer of dense connective tissue called periosteum. y Bone consists of: 1)living cells called osteoblast (bone-forming cells) which secrete the organic components of the bone matrix or ground substance called osteoid. 2)Bone matrix(osteoid) is impregnated with organic salts such as calcium hydroxyapatite crystals(70%) and of 30% collagen and glycoprotein. 3)In addition to this, the matrix contain numerous collagenous fibres. Collagen fibres together with the bone cells constitute the organic (living) matter in bone tissue.Jasmin 110

Mature compact bone is lamellar, or layered, in structure. The bone is arranged in concentric layers or concentric rings (lamellae) of matrix, around central canals, forming structural units called osteons. The osteon consists of a central canal called the haversian canal, which contain the blood supply for nourishing the osteocytes which are the bone cells that function in maintaining bone. Osteocytes are located in spaces called lacunae between the rings of matrix. Volkmann canalsJasmin

haversian canal,

111

Jasmin

112

y The lacunae are connected

with each other and with Haversian canals by means of delicate canaliculi, which allow passage of nutrient substances from the bloodstream to the osteocytes. y In compact bone, the Haversian systems are packed tightly together to form what appears to be a solid mass. y Volkmann canals interconnect the blood vessels in the Haversian canals of adjacent osteon.Jasmin 113

Jasmin

114

Jasmin

115

Osteoclasts. Osteoclasts (bone breakers) are cells, which reabsorb bone. They are large multinucleated cells, which vary in size and in the number of nuclei they possess. Osteoclasts appear to release lysosomal acid hydrolases, which alter the polymerization of the ground substances, resulting in the breakdown of bone. Parathyroid hormone increases the number and activity of osteoclasts and elevates the blood calcium level.Jasmin 116

FUNCTION OF BONEy Support. y y y

y y

The skeleton, which consists mainly of bone tissue, forms a supportive framework, giving rigidity to the body. Locomotion The bone tissue forms a system of levers to which the voluntary muscles are attached. Protection It serves to protect the soft and delicate organs of the body such as the skull protects the brain. Manufacturing of Blood Cells. Red blood cells are manufactured in the red bone marrow, which is situated in the spongy tissue at the ends of long bones. Homeostasis. Bone plays a part in homeostasis because it helps to maintain a constant level of calcium in the blood. Shape: The overall shape of our bodies is mostly due to our skeletons. e.g.your skeleton determines if you are short or tall by how long your bones are .Jasmin 117

bloody In human the total circulating blood volume is

about 8% of body weight . y Blood is a connective tissue containing 45% blood cells suspended in a fluid called plasma.

Jasmin

118

Jasmin

119

Blood plasmay Blood plasma is the liquid component of blood, in which the blood cells are suspended. y It makes up about 55% of total blood volume. y It is composed of mostly water (90% by volume), and contains a)dissolved proteins, b)glucose, c)clotting factors, d)mineral ions, e)hormones and f)carbon dioxide (plasma being the main medium for excretory product transportation).Jasmin 120

Blood cellsleucocytes granulocytes neutrophils basophils eosinophils erythrocytes platelets

agranulocytes lymphocytes monocytes

Jasmin

121

Jasmin

122

Erythrocytes/ red blood cellsy Red blood cells are the most common type of blood cell

which function in delivering oxygen to the body tissues via the blood. Each red blood cells are filled with 250 millions molecules of hemoglobin, a biomolecule that can bind to oxygen. They take up oxygen in the lungs and release it to the respiring tissue. The blood's red color is due to the color of hemoglobin. In humans, red blood cells develop in the bone marrow. Red blood cell is a flexible biconcave disks, lack a cell nucleus, live for about 120 days. Red blood cells are also known as RBCs, red blood corpuscles

Jasmin

123

Each red blood cells are filled with 250 millions molecules of hemoglobin, where each haemoglobin can bind to 4 molecules of oxygen.

Jasmin

124

Jasmin

125

Neutrophils. The mature neutrophil is about twice the size of the red blood cell. The lobulated nucleus usually have three to five lobes. fn. It acts as phagocytes.

Jasmin

126

Eosinophils (acidophils).The eosinophil usually has a two-lobed nucleus and contain granules . Fn: helps to control allergic responses by secreting enzymes histaminase to which destroy histamine or inactivate histamine that promote an extreme inflammatory response, characterized by local blood vessel dilation, cytokine release, and recruitment of leukocytes. Allergy refers to the bodys hypersensitivity to certain environmental conditions. It is an exaggerated response of the immune system to substances that cause no harm in most individuals. In this case the body is defending itself against a harmless substance, so this false alarm causes irritation at the site of Jasmin occurrence.

127

Basophils have large irregularly shaped, pale staining nuclei. The granules are of variable number Fn: secrete histamine which is involved in allergic responses n secrete heparin to prevent blood clot. Lymphocytes. Lymphocytes may measure 7-8 m (slightly larger than erythrocyte). They have a relatively large, spherical nucleus Fn: responsible for specific immune system. Eg. lymphocytes produce antibodies to destroy antigen. Basophils.

Monocytes. The three most useful diagnostic features of these cells include their dull grey-blue cytoplasm, diameter (16 - 20 m), and their distinctive horseshoe or kidney shaped nucleus. The nuclei are rarely spherical. Fn: known as macrophage and are phagocytic cells.

Jasmin

128

plateletsy Platelets, or thrombocytes, are y y

y y y

small, irregularly shaped anuclear cells, 2-4m in diameter, The average life span of a platelet is between 8 and 12 days. Platelets circulate in the blood of mammals and are involved in the formation of blood clots. Platelets have no nucleus. If the number of platelets is too low, excessive bleeding can occur; However, if the number of platelets is too high, blood clots can form (thrombosis), these can block blood vessels, and may cause a stroke and/or a heart attack.Jasmin 129

y

1.Transports:

Function of blood

Dissolved gases (e.g. oxygen, carbon dioxide); Waste products of metabolism (e.g. water, urea); Hormones; Enzymes; Nutrients (such as glucose, amino acids, micro-nutrients (vitamins & minerals), fatty acids, glycerol); Plasma proteins (associated with defence, such as blood-clotting and anti-bodies); Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes'). y 2.Maintains Body Temperaturey 3.Controls pH The pH of blood must remain in the range 6.8 to 7.4, otherwise it

begins to damage cells.

Jasmin

130

y 4.Removes toxins from the body The kidneys filter all of the blood in the body (approx. 8 pints), 36 times every 24 hours. Toxins removed from the blood by the kidneys leave the body in the urine. (Toxins also leave the body in the form of sweat.) y 5.Regulation of Body Fluid Electrolytes Excess salt is removed from the body in urine. y 6.Protective function Neutrophils and monocytes engulf antigen. Lymphocytes produce antibodies to destroy pathogens.

Jasmin

131

2. Cell structure and functionJasmin 132

Cell Wally Cell wall is an extracellular structure of plant cells that distinguishes them from animal cells. y The plant cell wall protects the plant cell and gives plant cells a very defined shape besides preventing excessive uptake of water.. y The cell wall is composed of cellulose fiber called microfibrils and embedded in matrix known as pectate and hemicellulose.Jasmin

133

Jasmin

134

y In new cells the cell wall is thin and not very rigid. This allows the young cell to grow. y This first cell wall of these growing cells is called the primary cell wall. y When the cell is fully grown, it may retain its primary wall, sometimes thickening it, or it may deposit new layers of a different material, called the secondary cell wall. y The secondary cell wall is deposited between plasma membrane and the primary wall. y It is often deposited in several laminated layers . y The secondary cell wall has a strong and durable matrix that affords the cell protection and Jasmin support.

135

The middle lamella is a pectin layer ( containing calcium and magnesium pectate) which cements the cell walls of two adjoining cells together or glue adjacent cell together . Plants need this to give them stability. Pits is a fine pore in the lignified walls which allow transport of materials between 2 plant cell through plasmodesmata.Plasmodesmata are intercellular cytoplasmic bridges linking 2 neighbouring cells to facilitate communication and transport of materials between plant cells. ...

Jasmin

136

Jasmin

137

FUNCTION OF CELL WALLTHE CELL WALL :1) protect the plant cell and give mechanical support. 2) maintain its shape 3) prevent the cell from bursting by preventing excessive uptake of water. 4)the strong walls help to hold the plant upright against force of gravity.

Jasmin

138

cell membraneAll cells are covered by a thin cell surface membrane. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix to help group cells together in the formation of tissues. The cell membrane is selectively permeable and able to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival. The movement of substances across the membrane can be either passive, occurring without the input of cellular energy, or active, requiring the cell to expend energy in moving it.Jasmin 139

FLUID MOSAIC MODEL MEMBRANE

Jasmin

140

The cell membrane is described as fluid mosaic model . This model is conceived by S.J. Singer and Garth Nicolson in 1972 to describe the structural features of cell membranes. The plasma membrane is described to be fluid because of its component such as lipids and membrane proteins move laterally or sideways throughout the membrane. That means the membrane is not solid, but is like a fluid'. The membrane is also described as mosaic because of the scattered arrangement of protein molecules in the phospholipid bilayer that gives the appearance of a mosaic pattern. Membrane is 7 nm thick.Jasmin 141

Component of cell membrane: 1) phospholipid bilayer 2) protein 3) cholesterol The cell membrane consists primarily of a thin layer of amphipathic phospholipids which spontaneously arrange so that their polar, hydrophilic heads are towards outer surface and the non polar, hydrophobic tails towards the inner surface. This forms a continuous, spherical lipid bilayer.Jasmin 142

The arrangement of hydrophilic heads and hydrophobic tails of the phospholipid bilayer prevent polar solutes (e.g. amino acids, nucleic acids, carbohydrates, proteins, and ions) from diffusing across the membrane, but generally allows for the passive diffusion of hydrophobic molecules. This affords the cell the ability to control the movement of these substances via transmembrane protein complexes such as pores and gates.

Jasmin

143

Protein found in the membrane falls under 2 categories: a) peripheral/ extrinsic protein b) integral intrinsic protein

Some of the proteins are found at the periphery of the lipid layer.These are the extrinsic proteins. These proteins are not at all embedded in the phospholipid bilayer.y Some of the protein molecules are found partially

or totally embedded in the phospholipid matrix. y Those are the intrinsic or integral proteins, which represent nearly 70% of the membrane proteins. These proteins cannot be extracted.Jasmin

144

Jasmin

145

Some of the integral proteins have very large molecules that extend throughout the phospholipid matrix, projecting out on both surfaces. These proteins are called tunnel proteins , pore or transmembrane proteins. They are believed to have channels for the passage of water soluble substances.Jasmin 146

FUNCTION OF PROTEIN IN MEMBRANEThe proteins present in the membrane may function as carriers or receptors or enzymes.

Jasmin

147

y Transport y A protein that span a membrane may provide a

hydrophylic channel across the membrane that is selective for a particular solute. y Enzymatic activity y A protein built into the membrane may be an enzyme with active site exposed to substances in adjacent solution. In some cases several enzymes acts as a team to carry out sequential steps of metabolic pathway. y Signal transduction y A membrane may have protein (receptor) that have a binding site that fits the shape of a chemical messenger such as hormone.Jasmin 148

y Cell- cell recognition. y Some glycoprotein serve as identification tags

that are specifically recognized by membrane protein of other cells. y Intercellular joining y Membrane protein of adjacent cells may hook together in various kinds of junctions such as tight junction. y Attachment of cytoskeleton and extracellular matrix. y Microfilament of cytoskeleton may be bound to protein membrane that helps to maintain the cell shape.Jasmin 149

There are three types of transport proteins in the cell membrane 1) channel proteins which form an aqueous channel, 2) passive transport carrier proteins which bind to specific solute molecules. 3)active transport carrier proteins which bind to specific molecules but move with the expenditure of energy.Jasmin 150

cholesteroly Cholesterol in the phosphoplipid bilayer makes it

stronger and more flexible . y Increase in temperature cause the cholesterol molecules to increase fluidity of membrane and promote movement of substance across the membrane. y At moderate warm temperature, the cholesterol molecules reduce free movement of phospholipid molecules and make the membrane less fluid. y At low temperature cholesterol molecules prevent the close packing of phospholipid molecules and slow solidification of the membrane. Finally when it is cool the phospholipid settle into a closely packed arrangementJasmin the membrane solidifies. and 151

Jasmin

152

Function of membraneThe plasma membrane forms a protective covering around the cell to maintain its size and shape. In addition, it is also responsible for the interactions that occur between the cell and its environment. Plasma membrane is described as a semipermeable or selectively permeable membrane since it allows only particles of a particular size, shape, texture and chemical composition to pass through. : 1) small molecules such as oxygen , carbon dioxide and hydrophobic molecules diffuse through phospholipid bilayer down concentration gradient. 2) protein channels and carrier move polar ions , molecules eg. Glucose and amino acid across membrane by facilitated diffusion. 3)protein pump actively transport substances against a concentration gradient across the membrane.

Jasmin

153

cytoplasmIt consists of :1) Cytosol contains various components: a)90% of water and solutes such as sugar, amino acid , enzymes, fatty acid ,nucleotides ,ATP, and dissolved gases. b)large molecules eg. protein which form colliod. 2)Cytoskeleton made up of microfilament and microtubules which form the providing support to the cell and are involved in cell motility. Organelles are structures in cell which are suspended in the cytosol and that carry out specialised function eg nucleus, mitochondria and chloroplast.Jasmin 154

CYTOSKELETON:Jasmin 155

Jasmin

156

y

Nucleus

organelles

y Nucleus is the most conspicuous and the largest organelle in the y y

y y y y

cell. The nucleus is a highly specialized organelle that serves as the information and administrative center of the cell. This organelle stores the cell's hereditary material, or DNA, and it coordinates the cell's activities, which include intermediary metabolism, growth, protein synthesis, and reproduction (cell division). Most cells have a single nucleus and hence they are described as uninucleate. Some cells have two nuclei (binucleate) while a few may be even multinucleate. A nucleus generally occurs in all eukaryotic cells. However, a nucleus may be absent in some mature cells. Mammalian RBC and sieve tube cells in plants are enucleate (without a nucleus at maturity).Jasmin

157

Jasmin

158

y Nucleus is bounded by a double-layered membrane, the nuclear envelope

which , separates contents of the nucleus from the cellular cytoplasm. y The envelope is perforated with holes called nuclear pores that allow specific types and sizes of molecules to pass back and forth between the nucleus and the cytoplasm. y The pores are fully permeable to small molecules up to the size of the smallest proteins, but form a barrier keeping most large molecules out of the nucleus.Jasmin 159

y The nuclear membrane also encloses a clear fluid matrix called nucleoplasm or karyolymph. y The nuclear envelope encloses a fine network of thread-like structures, called chromatin network that contain DNA and histones arranged in a specific manner. y The chromatin condenses to form distinct structures called chromosomes at the time of cell division. y The nucleus also shows a round body called nucleolus in between the chromatin network. y Nucleolus is a membrane-less organelle within the nucleus that manufactures ribosomes. y Substances from cytoplasm enter the nucleus freely and may influence the DNA and at the same time the DNA of the nucleus has its own influence on the activities inside the cytoplasm.Jasmin 160

Function of nucleus The nucleus of a cell generally serves the following functions : Nucleus is considered as the controlling centre of the cell. Nucleus maintains the cell and brings about its growth by directing

the synthesis of structural proteins. Nucleus regulates the metabolic processes in the cell by directing the synthesis of functional proteins such as enzymes. Nucleus contains the genetic information necessary for reproduction, development and metabolism of the organism as a whole. Nucleus distributes the genetic material equally through the process of replication. Nucleus is involved in the formation of ribosomes.

Jasmin

161

Endoplasmic reticulum

Jasmin

162

y Endoplasmic Reticulum y It is a system of highly branching

y

y y

y

membranes, which almost fills the space inside the cell membrane. Some of the branches of endoplasmic reticulum are connected to the plasma membrane while some of them are connected to the nuclear membrane. Two types of endoplasmic reticulum : A) Smooth endoplasmic reticulum (SER) in which the surface of the tubules lacks granules. B)Rough endoplasmic reticulum with ribosomes on outer surface.Jasmin

163

Smooth endoplasmic reticulumy Smooth endoplasmic reticulum consists of tubules and vesicles that branch forming a network. . y The network of smooth endoplasmic reticulum allows increased surface area for the action or storage of key enzymes and the products of these enzymes. y In the case of smooth endoplasmic reticulum in muscle cells, the vesicles and tubules serve as a store of calcium which is released as one step in the contraction process. y Calcium pumps serve to move the calcium. Jasmin

164

y

FUNCTION OF SMOOTH ENDOPLASMIC RETICULUMSynthesis of lipids and steroids, metabolism of carbohydrates, Store and regulate calcium concentration, detoxify drug and making them more soluble and easier to flush from the body. attachment of receptors on cell membrane proteins,

y y y y

y

Jasmin

165

y ROUGH ENDOPLASMIC RETICULUM y RER consists of an interconnected system of

membrane bound flattened sac called cisternae y The surface of the rough endoplasmic reticulum (RER) is studded with ribosomes giving it a "rough" appearance (hence its name) y The membrane of the RER is continuous with the outer layer of the nuclear envelope. y Although there is no continuous membrane between the RER and the Golgi apparatus, transport vesicles shuttle proteins between these two compartments. y The RER works in concert with the Golgi complex to send proteins to their proper destinations.Jasmin 166

Jasmin

167

yGeneral function of Endoplasmic

reticulum

y It provides intracellular transportation of materials inside the cell. eg. polypeptide chain synthesized on the surface of ribosomes are modified to form glycoprotein by addition of short polysaccharide chain and transported to Golgi apparatus. y Transport vesicle containing modified protein are budded off from RER and are transported to Golgi apparatus. y It forms an internal supporting framework for the cell, called cytoskeleton. y SER provides surface for the synthesis of lipids while RER provides surface for the synthesis of proteins and carbohydrates. y It provides a pathway for the distribution of nuclear material from one cell to another. y Being highly coiled in nature, it provides an increased surface area for various enzyme catalyzed reactions.Jasmin 168

Differences betweenSER RER

Tubular in shape and has smooth appearance

A system of flattened membrane bounded sac and has granular appearance due to presence of ribosome.

Site of phospholipid and fatty Site of protein synthesis acid metabolism. Detoxify harmful chemicals Provides intercellular transportation . Involved in transport of protein to golgi apparatus.Jasmin 169

y Golgi Complexy Golgi complex appears as a central stack of flattened inter communicating sacs called cisternae in a parallel arrangement along with tubules and vesicles. y The cisternae are continuously being formed at cis- face and bud off as vesicles at the trans face of the stack. y In animals Golgi complex is abundant in secretory cells and cells that are rapidly dividing eg. pancreatic cells, goblet cells , cell in the testis and ovaries.Jasmin 170

Function of Golgi apparatus .y Golgi apparatus receives vesicle from ER , stores and modifies

the protein through glycosylation by adding sugar molecules or short carbohydrate chain to form glycoprotein.

y The main function of Golgi complex is to take part in secretion.

Secretory vesicles produced by Golgi apparatus contain zymogen(eg. Pepsinogen, trypsinogen) hormones and neurotransmitter. y They release their content to the cell s exterior by exocytosis process. y Fusion of Golgi vesicle with the cell surface membrane maintains the membrane which is used to form phagocytic vacuoles and pinocytic vesicles. y It is also known to be involved in the formation of lysosomes.Jasmin 171

Jasmin

172

Jasmin

173

Jasmin

Proteins that need to to be transported out of the cell are synthesized on the surface of the endoplasmic reticulum (ER). At the ER membrane, proteins are inserted through (or into) the membrane via a pore called the translocon. Short carbohydrate chain are added to them to produce glycoproteins, and they are then moved to cis face of the Golgi apparatus in transport vesicles that bud from the ER membrane. 174

Within the Golgi, the protein may be modified further. Sugars are covalently attached in a process called glycosylation, and indeed many different modification steps take place there. Most of these "translocated" proteins are dispatched from the trans face of the Golgi apparatus in transport vesicles that move through the cytoplasm and then fuse with the plasma membrane releasing the protein to the outside of the cell. Examples of secretory proteins are collagen, insulin, and digestive enzymes of the stomach and intestine. then be dispatched from the trans face in a new transport vesicle. Like secretory proteins and some other proteins, proteins destined for lysosomes are made on ribosomes bound to the RER and move through the endomembrane system. In this case the lysosomal protein-containing vesicle that buds from the trans face of the Golgi apparatus is the lysosome Jasmin 175 itself.

lysosomey Lysosomes are tiny, spherical y y y y

y

sac-like structures evenly distributed in the cytoplasm. The membrane that surrounds a lysosome, encloses a variety of hydrolytic enzymes. This membrane prevents the enzymes from reaching cytoplasm. The substance that is to be hydrolyzed has to enter a lysosome. Lysosome are seen practically in all animal cells with the exceptions like mature mammalian RBC. Largely, they are absent in plant cells.Jasmin 176

Jasmin

177

Function of lysosomeThe lysosomes are involved in several lytic processes in the cell such as: 1) It brings about digestion of useful organic substances taken in by the cell by endocytosis process. This process is known as intracellular digestion or heterophagy or phagocytosis. 2) At times the lysosomal enzymes are capable of destroying the entire cell. Lysosomes are commonly described as suicide bags or time bombs of the cell. This process is called autolysis. E.g in metamorphosis of frog. 3) The old and worn out organelles of cells are destroyed in a process called autophagy. The component molecules are made available for the formation of new cells. Jasmin 178

Jasmin

179

Ribosomesy Ribosomes are granule-like structures found in both prokaryotic and y y y y y y

eukaryotic cells. They are found distributed all over the cytoplasm. In a eukaryotic cell ribosomes occur freely in the cytoplasm or attached to the surface of branches of endoplasmic reticulum (RER), or in the matrix of organelles like mitochondria and chloroplasts. It is also found attached to the nuclear membrane and inside the nucleolus. Ribosomes are of two types 70s type and 80s type. 70s ribosomes are found in prokaryotic cells while 80s ribosomes are found in eukaryotic cells.

Jasmin

180

y S stands for swedberg unit, which is a measure of

particle size related to the speed at which the particles settle when subjected to centrifugation (S=1x10-13second). y Each ribosome consists of two sub units that is 1)small subunit 2)large subunit. y The sub units occur separately in the cytoplasm and join to form a ribosome particle only at the time of protein synthesis. y The 70s ribosome has two sub units of 30s and 50s y The 80s ribosome has two subunits of 60s and 40s.Jasmin 181

Composition of ribosomeRibosome consists of 50% ribosomal RNA and 50% protein

Jasmin

182

Function of ribosome y Site of protein synthesisRibosome contain binding site for mRNA and tRNA molecules. The ribosome moves along the mRNA strand to translate the genetic code on mRNA and thus synthesised polypeptide chain. y The protein produced by ribosomes on RER are transported to Golgi apparatus to be processed into digestive enzymes or hormone to be exported out by exocytosis process . y Free lying ribosome in cytoplasm synthesis protein and enzyme for intracellular use.Jasmin 183

Jasmin

184

Mitochondriay Each mitochondrion is bound by a double

membrane. y The outer membrane is smooth while the inner membrane is thrown into numerous folds called cristae. y Thus, the surface area of inner membrane is much higher than that of outer membrane. The cristae bear numerous, minute, regularly spaced particles called stalked particles or oxysomes. y There may be any where between 100,000 to 1,000,000 stalk particle in a single mitochondrion! y The stalk particle enclose enzymes that are involved in the release of ATP molecules from the oxidation of glucose.Jasmin 185

Jasmin

186

y The rest of the inner membrane contains some

coenzymes that are involved in this process. y The inner membrane encloses a matrix, which is rich in proteins, lipids, ribosomes, RNA and one or two circular DNA molecules. y The number of mitochondria in a cell varies considerably and depends on the nature of the cell. y Cells with very high-energy requirements possess very large number of mitochondria. y A human liver cell for example may have more than 1000 mitochondria. y So also the flight muscle cells in insects. y Mitochondria are absent in the mature human RBC.Jasmin 187

Jasmin

188

Jasmin

189

FUNCTION OF MITOCHONDRIAy Mitochondria represent the

sites of aerobic respiration in a cell. y They use molecular oxygen to oxidize glucose into carbon dioxide and water. y Oxidation releases energy in the form of molecules of adenosine triphosphate (ATP), which are stored in mitochondria and released in the cell. Hence, mitochondria are described as minute powerhouses of the cell.Jasmin 190

Plastidy One of the most widely recognized and important

characteristics of plants is their ability to carry out photosynthesis, i.e. to make their own food by converting light energy into chemical energy. y This process occurs in almost all plant species and is carried out in specialized organelles known as chloroplasts. y All of the green structures in plants, including stems and unripened fruit, contain chloroplasts, but the majority of photosynthesis activity in most plants occurs in the leaves.Jasmin 191

y On the average, the chloroplast density on the surface

of a leaf is about one-half million per square millimeter. y Chloroplasts are one of several different types of plastids, which is plant cell organelles that are involved in energy storage and the synthesis of metabolic materials. Other plastids are: y The colorless leucoplasts, for instance, are involved in the synthesis of starch, oils, and proteins. y Yellow-to-red colored chromoplasts manufacture carotenoids, y The green colored chloroplasts contain the pigments chlorophyll a and chlorophyll b, which are able to absorb the light energy needed for photosynthesis to occur. Jasmin 192

Jasmin

193

Chloroplast y Chloroplast is enclosedin a double membrane y ( inner and outer membrane) y The area between the two layers that make up the membrane is called the intermembrane space. y The outer layer of the double membrane is much more permeable than the inner layer, which features a number of embedded membrane Jasmin transport proteins.

194

Jasmin

195

Jasmin

196

y Enclosed by the chloroplast membrane is the stroma, a semi-fluid y y y y

material that contains dissolved enzymes and comprises most of the chloroplast's volume. In higher plants the internal membranes (lamella) forms stacks of closed hollow disks called thylakoids, and inside is the thylakoid space or lumen. The photosynthetic reaction takes place on the thylakoid membrane. A stack of thylakoids is called a granum (plural: grana). Chloroplasts also possess their own genomes that is the chloroplast DNA and special ribosomes and RNAsJasmin 197

Function of chloroplasty Site of photosynthesis. y The grana and thylakoid membrane provide large surface area for chlorophyll and accessory pigment to be located to trap light energy and carry out production of ATP and NADPH. y The stroma contains enzymes to carry out light dependant reaction

( calvin cycle) and production of high energy organic molecules eg. sugar molecules.Jasmin 198

y Under the electron microscope the

y y y y

y

centrioles appear as two short, hollow, cylinders usually lying at right angles to each other. Each centriole is made up of nine microtubule triplets, which lie evenly spaced in a ring. There are no microtubules in the center (9+0 arrangement). The centrioles appear as two, darkly staining granules, usually above the nucleus in animal cells. They are generally absent in plant cells, except in motile cells. The centrioles lie in a small mass of specialised cytoplasm called centrosphere. It distinctly lacks other cell organelles. The centrioles and the centrosphere are together described as centrosome. Jasmin

Centrioles

199

y Centrioles are involved

in organizing the spindle fibres and astral rays during cell division in animal cells. y They provide basal bodies from which arise cilia and flagella.

Jasmin

200

Vacuoley

is a membranbound [tonoplast] sac that plays roles in intracellular digestion and the release of cellular waste products.

In animal cells, vacuoles are generally small. y Young plants usually have many vacuoles which fuse together to form one large central vacuoles which play a role in maintaining turgor (pressure). Due to this the nucleus and cytoplasm are pushed to the cell periphery.

Jasmin

201

y When a plant is well-watered, water collects in cell vacuoles producing turgidity y With insufficient water, turgor pressure in the vacuole is reduced and the plant wilts or plasmolysed. y Vacuoles accumulate toxic wastes: or a range of nitrogenous wastes. y The tonoplast (vacuole membrane) holds transport proteins, mostly active-transport carriers for one way accumulation of toxics into the vacuolar spaces. y As plant cells age.. onset of death is usually associated with tonoplast leakage & breakdown.

Jasmin

202

Function of vacuoley In plants the vacuole functions to store food

substances e.g. sugars, amino acids and mineral ions. y The concentrated cell sap causes water to enter by osmosis and the cell become turgid. Turgidity of plant cells help to control cell shape and volume, gives support to herbaceous plants and plays a role in enlargement and growth of young plant cells. y Vacuoles of some cell e.g. petals of flowers contain coloured pigments to attract insects for pollination.Jasmin 203

y Vacuoles in leaves accumulate some waste

product e.g. tannins and are removed when the leaves fall. y Food vacuoles formed by endocytosis enable bulk intake of large food particles. y Contractile vacuole in unicellular organisms e.g. Amoeba, Paramecium, regulated water content in the cell.

Jasmin

204

Jasmin

205