Download - CHAPTER 2 : CELL STRUCTURE AND FUNCTIONS...Eukaryotic cell : Cell that has genetic material that is enclosed by nuclear membrane. E.g. of eukaryotic cell : animal cell, plant cell

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BIOLOGY STUDENTS COMPANION RESOURCES

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BIO SCORE

CHAPTER 2 : CELL STRUCTURE AND FUNCTIONS

SUBTOPIC : 2.1 Prokaryotic and eukaryotic cells

LEARNING OUTCOMES: a) State the three principles of cell theory.

b) Explain the structures of prokaryotic and eukaryotic cells.

c) Illustrate and compare the structures of prokaryotic and eukaryotic cells (plant

and animal cells).

.

MAIN IDEAS/

KEY POINT EXPLANATION NOTES

a) State the

three principles

of cell theory.

▪ All living things are composed of cells (All organisms are composed of one

or more cells).

▪ Cells are the structural and functional unit of life.

▪ All cells come from pre-existing cells by division.

b) Explain the

structures of

prokaryotic

and eukaryotic

cells.

▪ Pro : before, early, primitive, first

▪ Karyon : nucleus

▪ Prokaryotic cell : Cell that has genetic material that is not enclosed by

nuclear membrane.

▪ e.g. of prokaryotic cell: bacteria

Explanation

about structure

of bacteria

(Circular) DNA • Is found in a single and coiled chromosome.

• Not associate with histone protein.

• Not enclosed in a nucleus (lies freely in cytoplasm).

• Located in a nucleoid region.

Plasmid • Small, double-stranded circular DNA

• Containing extra genes / provide genetic

informations for certain activities of cell

Shape • Spherical (cocci)

• Rod-shaped (bacilli)

• Spiral

Glycocalyx /

Capsule • Outside of / external to cell wall

• Made up of polysaccharide and protein

• Protect against immune system of host cell

Cell membrane • Membrane and other structures that surround and

protect the cytoplasm

• Main components are phospholipid bilayer and

embedded proteins

• Control the flow of materials into and out of cell

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MAIN IDEAS/


Explanation

about structure

of bacteria

Cell wall • Made up of peptidoglycan

• Provide structural support and maintain shape of the

bacterial cell

Cytoplasm • Semifluid (water-based) solution

• Composed of water and organic molecules

• Enclosed by plasma membrane

Fimbria (sin.);

Fimbriae (pl.) • Fine, hair-like bristles that present in multiple

numbers

• Help bacterial cell in adhesion to host cell or other

bacterial cell

Pilus (sin.);

Pili (pl.) • Bristle-like structures that present single or in pairs

• Longer than fimbria

• Help in adhesion to another bacterial cell during the

transfer of DNA (sex / conjugation pilus)

Flagellum (sin.);

Flagella (pl.) • Long fibers / structures that protrude from the

surface of the bacteria cell

• Mainly for locomotion / movement / motility

Ribosome • Tiny particle compose of RNA and protein

• Site of protein synthesis

Mesosome • Irregular fold in plasma membrane

• Site of cellular respiration

Structure of bacterial cell

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MAIN IDEAS/


Different shape of bacterial cell

Structure of flagella, fimbriae and pilus

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MAIN IDEAS/


Eukaryotic cells

▪ Eu : true

▪ Karyon : nucleus

▪ Eukaryotic cell : Cell that has genetic material that is enclosed by nuclear

membrane.

▪ E.g. of eukaryotic cell : animal cell, plant cell

Explanation

about structures

of eukaryotic

cells

▪ Have membrane-bounded nucleus

▪ Nuclear envelope / membrane enclose the nucleus (separating its contents

from the cytoplasm)

▪ Genetic material is linear DNA that is associated with histone protein

▪ Has membrane-bounded organelles

▪ There are two classes of organelles :

1) Endomembrane system : organelles that communicate with one another via

small vesicles or membrane channels

2) Energy related organelles such as mitochondria, chloroplasts

DNA associate with histone protein

Structure of an animal cell

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MAIN IDEAS/


Structure of a plant cell

c) Illustrate and

compare the

structures of

prokaryotic

and eukaryotic

cells (plant

and animal

cells).

Illustration of

prokaryotic cell

(e.g. bacterial

cell)

Structure of a prokaryotic cell

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Illustration of

eukaryotic cells

Structure of eukaryotic cells

Comparison

between

prokaryotic and

eukaryotic cells

***Refer to similarities and differences

Similarities :

- Both cells are surrounded by plasma membrane

- Both cells have DNA as genetic material

- Both cells have cytoplasm, ribosome, smooth and rough ER, mitochondria,

nucleus, nucleolus

Plant cell

Animal cell

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Comparison

between

prokaryotic and

eukaryotic cells

Differences between prokaryotic and eukaryotic cells

Features /

characteristics

Prokaryotic cells Eukaryotic cells

Cell division

Binary fission with no

spindle formation

By mitosis or meiosis or

both with spindle fiber

formation

Cell walls

Composed of

peptidoglycan

Animal cell has no cell wall,

plant cell has cellulose cell

wall and cell wall of fungi

composed of chitin

Membrane-

bounded

organelles

Absent in prokaryotic

cells Present in eukaryotic cells

Ribosome

Has small size (70S)

ribosome

Has large size (80S)

ribosome; Small size (70S)

ribosome present in

organelles

Genetic

materials

Circular DNA lies freely

in cytoplasm.

DNA not associate with

histone protein.

Linear DNA located in

double membrane-bounded

nucleus.

DNA associate with histone

protein.

Flagella

Simple flagella lack of

'9+2' microtubule

arrangement

Complex flagella with '9+2'

microtubule arrangement

Plasmid Present in some bacteria Absent in eukaryotic cell

Cellular

respiration

Site of cellular respiration

is mesosome

Site of cellular respiration is

mitochondrion

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BIO SCORE

CHAPTER 2 : CELL STRUCTURES AND FUNCTIONS

SUBTOPIC : 2.2 Structures and functions: Cell membrane and organelles

LEARNING OUTCOMES:

a) Show the detailed structures of typical plant and animal cells and state the organelles present.

b) Explain the structures and functions of the following organelles : nucleus, rough endoplasmic

reticulum, smooth endoplasmic reticulum, Golgi body, lysosome, ribosome, mitochondria,

chloroplast and centriole.

c) Show the structure of plasma membrane based on Fluid Mosaic Model.

d) Explain the structure of the plasma membrane and the functions of each of its components.

MAIN IDEAS/


a) Show the detailed

structures of

typical plant and

animal cells and

state the

organelles

present.

Detailed structures

of typical plant and

animal cells

Animal cells seen under light compound microscope

Plant cells seen under light compound microscope

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MAIN IDEAS/


Detailed structures

of typical plant and

animal cells

Animal cells seen under electron microscope

Plant cells seen under electron microscope

Organelles present in

plant and animal

cells

Organelles in animal cell

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MAIN IDEAS/


Organelles present in

plant and animal

cells

Organelles in plant cell

b) Explain the

structures and

functions of the

following

organelles :

nucleus, rough

endoplasmic

reticulum,

smooth

endoplasmic

reticulum, Golgi

body, lysosome,

ribosome,

mitochondria,

chloroplast and

centriole.

Organelle :

▪ Structures that suspended within cytosol and perform specific

functions inside cell.

▪ Can be divided into membranous organelles and non-membranous

organelles

Membranous

organelles

Non-membranous

organelles

Nucleus

Chloroplast

Mitochondria

Rough ER

Smooth ER

Golgi apparatus

Lysosome

Ribosome

Centriole

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Explanation on the

structures and

functions of

organelles

Organelles Structures Functions

Nucleus ▪ Spherical or oval in shape

▪ Double membrane nuclear

envelope enclose the nucleus

and separate it from cytoplasm.

▪ Has outer membrane that is

continuous with endoplasmic

reticulum and also has inner

membrane

▪ Inner part of nucleus is

nucleoplasm which is semifluid

medium containing chromatin,

nucleotides, mineral ions,

enzymes and nucleolus

▪ Surface of nuclear membrane

has nuclear pore that regulate the

entry and exit of molecules e.g.

protein, RNA from nucleus.

▪ Nucleolus is small dense

spherical body within nucleus

that consist of RNA and protein

• Store genetic

information /

genes of a cell :

contain

chromatins /

chromosomes

in nucleoplasm

• Control

production of

RNA and

proteins in cell

• Control all

activities of cell

by regulating

synthesis of

proteins and

enzymes

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Explanation on the

structures and

functions of

organelles

Rough

endoplasmic

reticulum (ER)

▪ Consist of network of

membranous flattened

sacs called cisternae

▪ Membrane of ER

separate the ER

lumen @ cavity /

cisternal space from

the cytosol

▪ Membrane of rough

ER is continuous with

the outer membrane

of nucleus

▪ There are ribosomes

on outer surface of

the rough ER

membrane

⚫ Synthesis secretory

proteins (e.g.

hormone)

- polypeptides

synthesized by

ribosomes are

transported to

ER lumen

- inside ER

lumen, the

polypeptides

are modified by

enzymes (add

carbohydrate

chain to the

protein

forming

glycoprotein)

⚫ Involve in

intracellular

transport of

proteins (the

glycoprotein is

packaged inside

transport vesicle and

the vesicle is carried

to Golgi body)

Smooth ER ▪ Consist of network of

membranous tubules

called cisternae

▪ Membrane of ER

separate the ER

lumen @ cavity /

cisternal space from

the cytosol

▪ Lack of ribosomes on

outer surface of the

smooth ER membrane

⚫ Site of lipid

synthesis

⚫ Breakdown of

stored glycogen to

glucose in liver

⚫ Store calcium ions

in sarcoplasmic

reticulum of skeletal

muscle

⚫ Detoxify drugs and

poison in liver

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Explanation on the

structures and

functions of

organelles

Golgi

apparatus /

body

▪ Consist of a group of

flattened membranous sacs

called cisternae

▪ Each cisterna has lumen

▪ Has two sides : cis face and

trans face

▪ Cis face is usually located

near the ER and receive

transport vesicles from ER

▪ Trans face bud off transport

vesicles containing specific

products to be carried to

other locations inside cell or

to plasma membrane for

secretion

▪ Modify,

packaging and

sorting of

protein

• Cis face

receive

transport

vesicles

from ER

• Products of

ER are

modified

during

their transit

from cis face

to trans face

of Golgi body

• Trans face

package the

modified

products in

transport

vesicles and

sort the

vesicles

to be

transported

out of Golgi

body

▪ Form lysosome

▪ Form

polysaccharide

s e.g. pectin in

Golgi body of

plant cells

which then

incorporated

with cellulose

into cell walls

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MAIN IDEAS/

KEY POINT

EXPLANATION NOTES

Explanation on the

structures and

functions of

organelles

Lysosome ▪ Spherical in shape

▪ Single-membrane

bounded organelle

▪ Produced by Golgi

apparatus

▪ Contains hydrolytic

enzymes

3) Involve in

intracellular food

digestion

(phagocytosis)

4) Involve in

autophagy

(digestion of old

@ worn out

organelles)

5) Involve in

autolysis

(digestion of old

@ damaged cells

results in apoptosis

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Ribosome ▪ Not bounded by

membrane

▪ Are complexes made of

ribosomal RNA (rRNA)

and protein

▪ Consist of two subunits

: large subunit and

small subunit

▪ Can be found as free

ribosomes (suspended

in cytosol) and bound

ribosomes (attach to

rough ER)

⚫ Site of protein

synthesis

- most of the

proteins made by

free

ribosomes function

within cytosol

- bound ribosomes

make proteins

that

are inserted into

membranes, for

packaging within

organelle e.g.

lysosome or

secretory proteins

Mitochondria ▪ Rod-shaped

▪ Double membrane-

bounded organelle :

- smooth outer

membrane

- highly folded inner

membrane forming

cristae

▪ Cristae is highly folded to

increase the surface area

of inner membrane thus

increasing the efficiency

of energy / ATP

production

▪ Intermembrane space is

the narrow region between

outer and inner

⚫ Site of cellular

respiration /

energy @ ATP

production

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membranes

▪ Mitochondrial matrix

containing enzymes, DNA

and ribosomes is enclosed

by the inner membrane

Chloroplast ▪ Double membrane-bounded

organelle

▪ Outer and inner membrane is

separated by very narrow

intermembrane space

▪ Inside chloroplast is another

membranous system in the form

of flattened, interconnected sacs

called thylakoids

▪ Stack of thylakoids are called

granum

▪ Thylakoid membrane contain

photosynthetic pigments e.g.

chlorophyll

▪ Fluid outside thylakoid is

stroma which contain enzymes,

DNA and ribosomes

▪ Site of photo-

synthesis

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MAIN IDEAS/


Explanation on the

structures and

functions of

organelles

Endomembrane System:

• Components of endomembrane system includes the nuclear envelope,

endoplasmic reticulum, Golgi apparatus, lysosome, various kinds of

vesicles, vacuoles and plasma membrane.

• The system carries out variety of tasks in the cell, including synthesis of

proteins, transport of proteins into membranes and organelles or

out of the cell, metabolism and movement of lipids and

detoxification of poisons.

• The membranes of this system are related either through direct physical

continuity or by formation of vesicles (membranous sacs).

Centriole ▪ In animal cells,

microtubules grow out

from centrosome (region

that is located near the

nucleus)

▪ Within the centrosome of

animal cells, is a pair of

centrioles

▪ Each centriole is

composed of nine sets of

triplet microtubules

arrange in a ring

⚫ May help

to organize

the spindle

fibre

during

mitosis and

meiosis in

animal

cells

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c) Show the

structure of

plasma

membrane based

on Fluid Mosaic

Model.

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d) Explain the

structure of plasma

membrane and

functions of each of

its components

▪ Fluid Mosaic model is proposed by Singer and Nicolson

▪ Fluid because phospholipids and proteins are able to move laterally /

side by side in the phospholipids bilayer

▪ Mosaic because arrangement of different proteins partially or fully

embedded or attached to the phospholipids bilayer

▪ Two main components of plasma membrane are phospholipids and

proteins

▪ Phospholipids are amphipathic molecules that means have both

hydrophobic and hydrophilic regions

- hydrophilic head

- hydrophobic tail

▪ Importance of hydrophobic regions in plasma membrane :

- allow the cell membrane to be selectively permeable

- allow movement of lipid soluble molecules

- reduce loss of water from inside cell

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MAIN IDEAS/


Explanation on the

structure of plasma

membrane and


its components

▪ Cholesterol are found in plasma membrane of animal cells between the

tails of phospholipids

▪ Function of cholesterol is to regulate fluidity of membrane under the

influence of temperature

- reducing fluidity of membrane / membrane less fluid at warm

/higher temperature

- membrane more fluid at lower temperature

▪ Two types of membrane proteins :

- intrinsic @ integral protein (either fully or partially embedded

in phospholipids bilayer)

- peripheral @ extrinsic protein (attach to phospholipids

bilayer)

▪ Functions of membrane proteins :

- as transport protein

- as enzymes

Channel

protein

Carrier protein

(for passive

transport)

Carrier protein

(for active

transport)

Has specific active site that binds with specific substrate during enzymatic reactions

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MAIN IDEAS/


Explanation on the

structure of plasma

membrane and

functions of each of its

components

- involve in signal transduction / as cell surface receptor

- as intercellular joining / involve in cell adhesion

- as cell surface identity marker or involve in cell

recognition

- provide attachment site for cytoskeleton and

extracellular matrix

Act as receptor that has

specific binding site for

signaling molecule e.g.

hormone

Membrane proteins of neighboring cells are joined together forming tissue e.g. epithelial cells

Helps to maintain cell

shape and

to stabilize location of

certain membrane

proteins

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MAIN IDEAS/


Explanation on the

structure of plasma

membrane and


its components

▪ Carbohydrate chains attach to protein forming glycoprotein

(e.g. variation in carbohydrate chain of glycoproteins on the

surface of RBC contribute to the 4 human blood types A, B,

AB and O)

▪ Carbohydrate chains attach to lipid forming glycolipid

▪ Importance of membrane carbohydrates in cell-cell

recognition :

- sorting of cells into tissues and organs in animal embryo

- basis for rejection of foreign @ non-self tissue by immune

system (e.g. MHC marker)

- enable cell recognize other cell by binding to molecules

containing carbohydrates on extracellular surface of plasma

membrane

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BIOLOGY SCORE

CHAPTER 2: CELL STRUCTURE AND FUNCTIONS SUBTOPIC : 2.3 Cells are grouped into tissues (animal tissues)

LEARNING OUTCOMES : (a) Describe the types of animal cells & tissues.

(b) Explain the following types of animal cells and tissues:

(i) Epithelial cells, nerve cell, muscle cells and connective tissue.

MAIN IDEAS/


a) Describe the

types of animal

cells & tissues.

▪ A group of similar cells and their intercellular substance joined together to

perform a specific function.

Four basic types according to their function and structure:

▪ Epithelial tissues

▪ Nervous tissues

▪ Muscle tissues

▪ Connective tissues

b) Explain the

types of animal

cells and

tissues:

A. Epithelial

tissues

▪ Characteristics:

- Consists of cells arranged in continuous sheets, in single or multiple layer.

- Closely packed and held tightly together by many cell junction.

- Has little intercellular space.

- Avascular (without blood vessels).

- Has a free surface.

- Has microvilli (intestine) and cilia (trachea).

- Rest on basement membrane.

- Covers a body surface (epidermis).

- Line inner body cavity, tubes and blood vessels.

- Cover the thoracic and abdominal organ.

- Also found in gland.

▪ General functions:

- Secretion

- Absorption

- Protect external and internal body surfaces from microbes, chemical,

dehydration and friction.

▪ Classification:

• Based on shape and number of cell layers.

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MAIN IDEAS/


Types of

Epithelium

Tissue

Types of Epithelial Tissue:

▪ Simple Squamous

▪ Simple Cuboidal

▪ Simple Columnar

▪ Stratified Squamous

Types Structure Distribution Function

Simple

squamous

• A single

layer of

flattened

cells with

disc-shaped.

• Central

nuclei.

• Air sacs of

lungs

• Glomerular

capsule of

Kidney

• Lines of heart

• Blood vessels

• Allow passage of materials

by diffusion and filtration

where protection is not

important.

Simple

cuboidal

• Single layer

of cube-

shaped

cells.

• Large &

spherical

central

nuclei.

• Thicker

than simple

squamous.

• Kidney tubule

• Ovary surface

& testes

• Ducts and

secretory

portions of

small gland

• Secretion of hormone or

saliva. (Salivary & Thyroid

gland.)

• Absorption (Reabsorption

of molecules by Proximal

Convoluted tubule in

kidney.)

Simple

columnar

• Single layer

of

rectangular/

tall cells.

• Nuclei

(round or

oval) near

base of

cells.

• Goblet cells

& cells with

microvilli &

cilia.

• Gallbladder

• Duct of gland

• Lines the

gastrointestinal

tract

• Uterine tube

• Bronchi.

• Secretion of enzymes,

mucus and other

substances.

• Ciliated type propels

mucus or reproductive cells

by ciliary action

• Absorbing nutrients.

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Types Structure Distribution Function

Stratified

squamous

• Several

layers cells

&

regenerates

rapidly.

• Cuboidal to

columnar

shape in

deep layers.

• Squamous

cells form

the apical

layer.

• Outer skin

• Anus

• Vagina

• linings of the

mouth

• oesophagus.

• Protects underlying

tissues in areas subjected

to abrasion.

• New cells formed to

replace cell that are

sloughed off.

B. Nervous

tissues

▪ Made up of neuron and neuroglia (supporting cells).

▪ Neurons consist of:

- dendrite

- cell body

- axon

▪ Axon

- Single extension of cytoplasm.

- Function: conducts impulse away from the cell body.

▪ Dendrite

- Highly branched extensions.

- Function: conduct signals toward the cell body.

-

▪ Node of Ranvier

- Small uncovered parts of axon between the myelin

sheath.

- Function: Site for accelerating impulse transmission.

▪ Myelin sheath

- Layer of fatty material (surround the axons).

- Produce by Schwann cell.

- Function: Protects axons and provide

electrical insulation.

▪ Neuroglia

- Supports and nourish the neurons.

- Example: Schwann cell

▪ Distribution: Brain, spinal cord and nerves.

▪ Function: to transmit impulse.

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MAIN IDEAS/


C. Muscle

tissues

▪ Structures:

- Muscles are responsible for all types of body movement

- Composed of muscle fibers (cell)

▪ Types:

- Skeletal Muscle

- Smooth Muscle

- Cardiac Muscle

▪ Skeletal Muscle

- Consists of several bundles of muscle fibers (cell)

- Muscle fibers consist of myofibrils

- Most are attached by tendons to bone.

- Muscle Fibers (cell): Striated (banding), Cylindrical and long,

Multinucleate, Sarcolemma (plasma membrane)

- Myofibril: Bundle of myofilaments – Actin (Thin Filament) and Myosin

(Thick Filament)

▪ Smooth Muscle

- Lack striation

- Spindle-shaped cells

- Single nucleus

- Involuntary control

- Functions: Propel substances of objects (foodstuff) along internal

passageways

- Location: Wall of internal organs (digestive tract) or hollow organs

▪ Cardiac Muscle

- Has striations

- Single nucleus

- Branched and interconnected

- Joined to another muscle cell at an intercalated disc.

- Involuntary control

- Function: As it contracted, it propels blood into the circulation

- Location: the walls of heart

-

Skeletal Muscle Smooth Muscle Cardiac Muscle

Tubular shape Spindle shape Elongate shape

Striated Non-striated Striated

Multinucleated Uninucleated Uninucleated

No intercalated disc No intercalated disc Has intercalated disc

Voluntary control Involuntary control Involuntary control

No branch No branch Branched

Attached to tendons of

bone

Wall of digestive tract Wall of heart

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D. Connective

tissues

1. Compact

Bones

▪ Animal tissue that functions mainly to bind and support other tissues, having

a sparse population of cells scattered through an extracellular matrix.

▪ Functions:

- Provide support, strength and flexibility.

- Transport of material.

- Store energy.

- Defend body against pathogens.

▪ Compact Bones

- Consists of Haversian System or Osteon.

- Forms the external layer of all bones.

- Matrix:

- Hard and rigid with collagen fibres.

- Contains water and impregnated with calcium carbonate and calcium

phosphate.

- Each Havesian System consist of:

- Lamella: Irregular cylinder with layer of matrix.

- Havesian Canal: Contain artery, vein, lymph and nerve fibers.

- Lacunae: Contains osteocytes.

- Canaliculi: contain cytoplasmic strands.

- connect to lacunae to each other and to a central canal.

- transport material to and from blood vessels in the Havesian

Canal.

- Central canal/ Havesian Canal: serves as a passageway for blood

vessels and nerves.

- Volkman Canal: connect the Havesian canals to each other.

- Bones cell:

- Osteoblasts (Bone forming cell): Deposit a matrix of collagen.

- Osteocytes: Non-dividing and inactive bone cells.

- Osteoclasts: Reabsorb the matrix.

-

- Functions of compact bones:

- Skeleton give a body

shape and support.

- Protect internal

organs.

- Attached to

skeletal

muscles

for movement.

- Blood cell production

(bone marrow).

- Reservoir for

calcium

and phosphorus.

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MAIN IDEAS/


2. Hyaline

Cartilage

Structure of compact bone

Structure of hyaline cartilage

▪ Hyaline Cartilage

- Extracellular Matrix:

- Collagenous fiber embedded in chondroitin sulphate

- Hyaline Cartilage Cells:

- Chondroblast: immature cells

- Secrete matrix: chondroitin sulphate and collagen

- Chondrocytes: mature cells

- Maintaining the matrix

- Located in lacunae

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MAIN IDEAS/


3. Blood

- Distribution:

- Nose, ears and caps on the ends of some bones.

- Function of hyaline cartilage:

- Provides smooth surfaces for movement at joints, as well as flexibility

and support

- Supporting trachea and bronchial tube

- Acting as shock absorbers between vertebrates

▪ Blood

- Extracellular Matrix:

- Plasma (water, salts and dissolved proteins)

-

- Cells

- Erythrocytes

- Leukocytes

- Platelets

Erythrocytes: red blood cells

- Biconcave disc-shape

- Lack of nuclei

- Thinner in the center than at its edge

- Contain haemoglobin, enzyme and inorganic ions

- Function: Transport oxygen, carbon dioxide, nutrients and waste

Leukocytes: white blood cells

- Larger than erythrocytes

- Spherical in shape

- Have nucleus and organelles

- Two types:

- Granulocytes: Granular cytoplasm

and lobed nuclei

- Agranulocytes: Clear cytoplasm and

nuclei not lobed

- Function: Responsible for antibody

production and other specific defense against pathogens

- Lymphocyte B: Produce antibody

- Neutrophils and Monocytes: Engulf foreign substances

Platelets

- Fragments of cells broken off from large cells in the bone marrow

- No nuclei

- Function:

- Blood clotting

- Repair gaps in the wall of blood vessel

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MAIN IDEAS/


Blood cells organization

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BIO SCORE

CHAPTER 2: CELL STRUCTURE AND FUNCTIONS SUBTOPIC : 2.3 Cells are grouped into tissues (plant tissues)

LEARNING OUTCOMES : (a) Describe the types of plants cells & tissues.

(b) Explain the following types of plants cells and tissues:

(ii) Meristem, Parenchyma, Collenchyma, Sclerenchyma, Xylem and Phloem.

MAIN IDEAS/


(a) Describe

the types of

plants cells &

tissues.

▪ Meristematic tissue

▪ Permanent tissue

- Ground tissue

- Vascular tissue

- Dermal tissue

(b) Explain the

following types

of plants cells

and tissues:

1. Meristem

tissues

▪ Meristem Tissue: Undifferentiated embryonic tissue in the active growth

regions of plants

▪ Location: Shoot tips and Root tips

▪ Structure:

- Cells are small and isodiametric

- Have large nucleus

- Have dense cytoplasm and few organelles

- Closely packed

- Have thin primary cell wall

- Cell actively divided

▪ Function: Differentiate to form specialized function

▪ Types and Function:

Types Function

Apical meristem

- Elongate shoots and roots.

- Produce primary plant body.

Lateral meristem

- Add thickness to woody plants (increase girth).

- Produce secondary plant body.

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Types of meristematic tissues

2. Ground

tissues

Types Parenchyma Collenchyma Sclerenchyma

Structure - shape: isodiametric

- thin primary wall

- thin and flexible

- contain cellulose,

hemicellulose and

pectin

- permeable to

water and permit

passage of solutes

- have large central

vacuole

- nucleus and

- shape: polygonal

- primary wall

- thicker than

parenchyma

- contain

cellulose,

hemicellulose

and pectin

- thickening occur

at the corners of

the walls

- pits are present in

- Dead at maturity

- Tough and thick

secondary cell

walls

impregnated

with lignin

- No intercellular

air spaces

- Pits are present in

the walls

- Lack living

protoplasts when

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cytoplasm pushed

to the periphery

- cell are loosely

packed together

- many large

intercellular air

space

- no secondary wall

- Perform most of

metabolic functions

of the plant

(photosynthesis)

- Synthesizing and

storing various

organic products

(starch and water)

- Intercellular air

spaces permit

gaseous exchange

the wall

they mature

- Various shape

and size

- Two types:

- Fiber

- Sclereids

- Structure of

Fiber:

- Long and

slender

- Group together

in strands

- Tapering ends

- Very tiny

cavity in the

center of the

cell

- Structure of

Sclereid:

- Shorter than

fiber

- Irregular in

shape

- Thick wall

- Lignified

secondary wall

Parenchyma Collenchyma Sclerenchyma

Distribution - Cortex of stem

- Cortex of roots

- Mesophyll

- Pulp of fruit

- Endosperm of

seed

- Outer regions of

cortex

- Below the

epidermis of

leaves, petioles

and soft stems of

dicot plant

- Leaf veins

- Young stem

Fiber:

- Below the

epidermis of

stem or roots

- Around

vascular bundle

Sclereid:

- Stem, leaves

and seeds

- Fruits (pears

and guava)

Function - Photosynthesis.

- Gaseous

Exchange and

buoyancy for

aquatic plants

(Intercellular air

spaces).

- Packing tissues

- Supporting tissue:

provide the

herbaceous plant

with mechanical

strength and

flexibility.

- Provide much of

support for stem

Fiber:

- Acts as

supporting

tissue.

Sclereid:

- Protective

tissue: gives

strength and

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(around vascular

tissues).

- Food storage

- Secretion (Sugary

nectar, hormones,

enzymes and

tannins).

in which

secondary

growth has not

taken place.

- Photosynthesis:

some

collenchyma

contain

chloroplast

support to the

plant structure

or organ.

3. Vascular

Tissue

▪ Involves in transport of materials around the plant body.

▪ Two types:

- Xylem: Vessel Elements and Tracheid

- Phloem: Sieve tube and Companion cell

Types Structure Function

Xylem

Vessel

element

- Secondary wall: lignin

- Ends open and connect to one

another to form long pipes

- Dead cells with hollow lumen

- More water can flow with less

friction

Transport water

and dissolved

minerals from

the roots to the

leaves

Tracheid

- Thick lignified

- Lumen: small and hollow when

mature

- Tapering end wall

- Lots of pits: allow water to move

to another tracheid also

surrounding living cells

Types Structure Function

Phloem

Sieve tube

- Consist of sieve elements (sieve

cells) joined together to form a

long tube.

- End walls are perforated forming

sieve plates with sieve pores.

- Cells are alive, with thin cellulose

walls and protoplasm.

Transport

organic material

(photosynthesis)

from one part of

the plant to

another.

Companion

cell

- Located beside the sieve tube.

- Have a nucleus, dense cytoplasm

with small vacuoles.

- Metabolically active (have

mitochondria and ribosomes).

- Linked to sieve elements by

numerous plasmodesmata.

Provide ATP for

active transport

during

transportation of

organic

material.

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Xylem

Vessel element Tracheid

Phloem

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BIO SCORE

CHAPTER 2: CELL STRUCTURE AND FUNCTION SUBTOPIC : 2.4 Cell Transport

LEARNING OUTCOMES : (a) Overview the various transport mechanisms across the membrane.

(b) Explain the various transport mechanism across the membrane

(i) Passive transport: Simple diffusion, facilitated diffusion and osmosis.

(ii) Active transport: Sodium-potassium pump and Bulk transport

(Endocytosis and Exocytosis)

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Transport

Across

Membrane

▪ Process to move substances across the cell membrane (plasma membrane) are

essential to the life of the cell.

▪ Example: Gaseous exchange

▪ Plasma membrane regulates the passage of molecules into and out of the cell.

- Enable a cell to control substances and how much of each enters or leaves

the cell

- It allows the cell to maintain a difference between its internal

environment and extracellular fluid.

- It supplies the cell with nutrients, removes wastes and maintains volume

and pH.

▪ Plasma membrane is selectively permeable.

- Only allow some material to pass.

- Inhibits passage of other materials.

Passive

transport

▪ Diffusion of solute across membrane.

▪ From high concentration region to low concentration region.

▪ Does not require energy/ ATP.

▪ Down concentration gradient.

▪ Until equilibrium is achieved.

▪ 3 types:

- simple diffusion

- facilitated diffusion

- osmosis

Simple diffusion

▪ Diffusion of solute directly through phospholipid bilayer to move across a

plasma membrane.

▪ Example of solutes/molecules are lipid soluble molecule, oxygen gas, carbon

dioxide.

Facilitated

diffusion

▪ Carrier-assisted diffusion of molecules across a cell membrane through

specific channels from a region of higher concentration to lower

concentration.

▪ Help/aid by carrier protein and channel proteins

▪ The process is driven by concentration gradient

▪ Does not require energy/ ATP

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▪ Example of molecules are glucose, fructose, amino acids, some vitamins, urea

▪ Carrier protein:

- bind to molecule and change their shape to move specific molecules in or

out of the cell

- example: glucose

▪ Channel protein:

- have a tunnel that allow movement of ions or charge molecules to move

in or out of the cell

- example: sodium ion or chloride ion

Comparison

between

simple diffusion

and

facilitated

diffusion

Simple diffusion Facilitated diffusion

Through the phospholipid bilayer Through the transport protein (carrier

or channel protein)

Happens to the small and non-polar

particles

Happens to large and polar particles

Movement of molecules occur down the concentration gradient

Not require energy

Osmosis ▪ The movement / diffusion of water across a

selectively permeable membrane from area of higher water potential to area

of lower water potential.

▪ Water potential: ψ (psi)

▪ Water molecules move from hypotonic

solution to hypertonic solution until solution are isotonic.

Concept of

water potential

▪ Water potential is free energy / potential energy of water.

▪ The tendency of water molecules to enter or leave from the solution by

osmosis.

▪ Unit of water potential is kilopascal (kPa)

▪ Components of water potential:

- solute potential

- pressure potential

▪ Formula of water potential:

Ψ = Ψp + Ψs

Water potential = pressure potential + solute potential

▪ Solute potential:

- A measure of the change in water potential of the system due to the

presence of solute molecules.

- usually negative value.

▪ Pressure potential:

- The component of water potential due to the hydrostatic pressure that is

exerted on water in a cell.

- usually positive value.

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▪ What happen to animal cell and plant cell in different tonicity of solution?

Active transport ▪ The movement of molecules / ions from a region of lower concentration

region to a region of higher concentration region// against concentration

gradient

▪ Require energy in the form of ATP

▪ Require transport / carrier / pump protein

▪ Example is Sodium-potassium pump

Active transport

(Sodium-

potassium

pump)

▪ Concentration of sodium ions (Na+) is higher outside of the cell; meanwhile

concentration of potassium (K+) ions is higher inside of the cell.

▪ For each cycle, Sodium- potassium pump transport THREE intracellular Na+

out of the cell and TWO extracellular K+ into the cell.

▪ Involve phosphorylation; the addition of phosphate group; which cause the

changes in conformation of protein.

Mechanisms /

steps in sodium

potassium pump

▪ 3 intracellular Na+ bind to specific site on carrier / pump protein

▪ The binding stimulates phosphorylation of carrier protein by ATP

▪ The phosphorylation causes the protein to change its conformation

▪ Causing expel of Na+ to the outside of cell.

▪ 2 extracellular K+ bind to specific site on carrier protein

▪ The binding triggers release of phosphate group from carrier protein

▪ Loss of phosphate restore original conformation of carrier protein

▪ K+ is released into the cell

▪ The cycle is repeated.

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Sodium-Potassium Pump

Bulk transport

▪ Transport materials that are too large

▪ Materials are transported across membrane via vesicles

▪ Types:

1. Endocytosis: Cellular uptake of biological molecules and particulate

matter via formation of vesicles from the plasma membrane.

2. Exocytosis: The cellular secretion of biological molecules by the fusion

of vesicles containing them with the plasma membrane.

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Endocytosis:

▪ Types of Endocytosis: Phagocytosis and Pinocytosis

Phagocytosis Pinocytosis

Large solid particles, such as food ad

bacteria are brought inside the cell by

invagination (an infolding of the cell

membrane)

Liquids or dissolved materials are

taken in via a small vesicle

‘cell eating’ ‘cell drinking’

Uptake of large solid particle Uptake of small liquid droplet

Eg: Engulfing bacteria by the

macrophage

Eg: Taking in of dissolved solutes

by absorptive cells in kidney and

intestines

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