Cell Ultrastructure 2013 Reading Notes (1)

CORE TOPIC 1: CELLULAR FUNCTIONS - ULTRASTRUCTURE OF CELLS

ContentDetailed structure of typical animal and plant cells, as seen under the electron microscope.Outline functions of organelles in plant and animal cells.

Learning Outcomes:Candidates should be able to:

1. Describe and interpret drawings and photographs of typical animal and plant cells as seen under the electron microscope, recognising the following membrane systems and organelles: rough and smooth endoplasmic reticulum, Golgi body, mitochondria, ribosomes, lysosomes, chloroplasts, cell surface membrane, nuclear envelope, centrioles, nucleus and nucleolus.(Knowledge of the principles of TEM and SEM are not required.) (For practical assessment, students may be required to operate a light microscope, mount slides and use a graticule.)

2. Outline the functions of the membrane systems and organelles listed in (1).

REFERENCES:

1. Raven et al (2011) Biology (9th Edition) – Chapter 42. Campbell, Reece (2012) Biology (9th Edition) – Chapter 63. R. Soper (1997) Biological Science 1 (3rd Edition) – Chapter 54. R. Soper (1997) Biological Science 2 (3rd Edition) – Chapter 13

VIRUSES AS AN EXCEPTION TO THE CELL THEORY

Viruses are much smaller than bacteria and cannot be seen using a light microscope. They range in size from about 20 nm to 400 nm and do not have a cellular structure, so they are described as akaryotic. They are intracellular parasites of plants, animals and bacteria, totally dependent on their host cells. The only characteristic they have in common with other living organisms is that they can reproduce once they are inside their host’s cells. Viruses do not respire, feed, excrete, move, grow or respond to stimuli. They disrupt the normal activities of cells, often with harmful effects on the host organism, so they are associated with disease.

A virus consists of: A core of nucleic acid A protein coat, or capsid

The nucleic acid may be: A double-stranded DNA, as in Herpes simplex, which causes cold sores Single-stranded DNA, as in Parvovirus, which causes gastroenteritis Single-stranded RNA, as in the influenza virus and the human immuno-deficiency virus (HIV)

TAMPINES JUNIOR COLLEGE/ BIOLOGY LECTURE JC 1 2013Lecture Notes Prepared by Mrs. Gay Guay Kim (January 2013)

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What are the characteristics of eukaryotic and prokaryotic cells?

There are two major groups of cellular organisms: Prokaryotes and Eukaryotes.

PROKARYOTES (pro, before; karyon, nucleus) lack true nuclei i.e. the genetic material (DNA) is not enclosed by nuclear membranes, and lies free in the cytoplasm.e.g. Bacteria.

EUKARYOTES (eu, true) are more complex and are characterised by a true nucleus with the genetic material being enclosed by the nuclear envelope.e.g. Protoctists, fungi, green plants, animals.

A TYPICAL PROKARYOTIC CELL

Table of detailed differences between prokaryotic and eukaryotic cellsProkaryotic cells Eukaryotic cells

Mostly small cells ranging in size from 1 to 10 µm Cells bigger, can be up to 400, typically 10 to 150 µm

Rigid cell wall containing murein present Cell walls when present contain cellulose (green plants) or chitin (fungi)

No true nucleus True nuclei present surrounded by nuclear envelope

Circular DNA; no true chromosomes Linear DNA with associated proteins forming true chromosomes

No nucleolus Nucleolus present

No endoplasmic reticulum Endoplasmic reticulum present with associated Golgi apparatus, lysosomes and vacuoles

Smaller (70S) ribosomes Larger (80S) ribosomes

No membrane-bound organellesLack mitochondria, mesosomes in some bacteria for respiration; lack chloroplasts, photosynthetic membranes (thylakoids) in photosynthetic bacteria

Many membrane-bound organelles: Chloroplast with lamellae in photosynthetic organisms;Mitochondria for aerobic respiration

Flagella when present lack microtubules Flagella have 9+2 arrangement of microtubules


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SIMILARITIESBoth prokaryotic and eukaryotic cells have: a cell surface membrane cytoplasm DNA ribosomes

DIFFERENCESProkaryotic cells do not have: a nucleus surrounded by a nuclear

envelope mitochondria endoplasmic reticulum and Golgi

apparatus chloroplasts a cytoskeleton of microtubules and

microfilaments


Compare and contrast the structure of typical animal and plant cells.

FUNDAMENTAL STRUCTURAL DIFFERENCES BETWEEN PLANT AND ANIMAL CELLS

PLANT CELLS ANIMAL CELLS

Tough, slightly elastic cellulose cell wall present (in addition to the cell membrane).

Pits and plasmodesmata present in the cell wall.

Middle lamella present - join cell walls of adjacent cells.

Plastids, e.g. chloroplast and leucoplasts, present in large numbers.

Mature cells normally have a large single, central vacuole filled with cell sap.

Tonoplast present around vacuole.

Cytoplasm normally confined to a thin layer at the edge of the cell.

Nucleus at edge of the cell.

Lysosomes not normally present.

Centrioles absent in higher plants.

Cilia and flagella absent in higher plants.

Starch grains used for storage.

Cell wall absent - only a membrane surrounds the cell.

No cell wall and therefore no pits or plasmodesmata.

Middle lamella absent - cells are joined by intercellular cement.

Plastids absent.

Vacuoles, e.g. contractile vacuoles, if present, are small and scattered throughout the cell.

Tonoplast absent.

Cytoplasm present throughout the cell.

Nucleus anywhere in the cell but often central.

Lysosomes almost always present.

Centrioles present.

Cilia or flagella often present.

Glycogen granules used for storage.

What are the structures and functions of the various cell organelles?

Questions for consideration:

1. What are the detailed structures and functions of the various membrane systems and organelles of the cell?

2. What are the advantages of compartmentalizing the cell?


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Is the nucleus the cell’s genetic control center?

NUCLEUS

Found in all eukaryotic cells. Common exceptions are mature phloem sieve tube elements and mature RBC of mammals. Normally cells contain only one nucleus. Exception: Paramecium sp. where 2 nuclei are present. Largest of cell organelles. Seen easily with a light microscope.

STRUCTURE:

Spherical to ovoid in shape. N.B. WBC – lobed nucleus About 10 m in diameter and 20 m in length.

Liver Cell (TEM x9,400). This image is copyright Dennis Kunkel at www.DennisKunkel.com, used with permission.


Nucleus, showing internal structure and relationship with the ER

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http://www.denniskunkel.com/


Nuclear membrane Nuclear envelope composed of two membranes Outer membrane is continuous with the endoplasmic reticulum and like the ER may be covered

with ribosomes engaged in protein synthesis.

Between the 2 membranes of the nuclear envelope is a perinuclear space about 20 nm wide.

Nuclear pores Nuclear envelope is perforated by nuclear pores. N.B. Nuclear pores allow exchange of substances between the nucleus and the cytoplasm. The pore is a definite structure formed by fusion of the outer and inner membranes of the envelope. This controls the passage of molecules through the pore. The pore may occupy up to 15% of the membrane’s surface area. Each pore is approximately 50 nm

in diameter.

CHECKPOINT:

Question: What substances are exchanged between the nucleus and the cytoplasm?

Answer:

Nucleoplasm Within the nucleus is a gel-like matrix called nucleoplasm (or nuclear sap). Nucleoplasm contains chromatin and one or more nucleoli. It contains a variety of chemical

substances such as ions, proteins and nucleotides.

Chromatin

Chromatin is composed mainly of coils of DNA bound to basic proteins called histones. Chromatin : ‘coloured material’ During nuclear division, chromatin condenses into more tightly coiled threads called chromosomes. During interphase (the period between nuclear divisions) it becomes more dispersed. However, some remains tightly coiled and continues to stain intensely. This is called

heterochromatin and is seen as dark patches. The remaining loosely coiled chromatin is located towards the centre of the nucleus and is called

euchromatin.


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Nucleolus Conspicuous rounded structure within the nucleus One or more nucleoli may be present within a nucleus Contains large amounts of DNA, RNA and proteins The function is to manufacture ribosomal RNA.

Nucleolar organisers are portions of DNA where portions of several different chromosomes meet.

FUNCTION:

1. Controls the cell activities. This is because it contains the genetic information in the form of DNA.2. Involved in cell division. Moreover, the DNA is capable of replication (duplication) and this can be followed by nuclear division

thus ensuring that the daughter nuclei also contain DNA. Nuclear division is the basis of cell replication and hence reproduction.

3. Protein synthesis. Nucleic acids provide the genetic code for protein synthesis at the ribosomes.

4. Nucleolus manufactures ribosomes.

CONCEPT MAP OF THE NUCLEUS:


partially permeable

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Which cell organelles are related through the endomembrane system?

ENDOPLASMIC RETICULUM ( ER )

STRUCTURE:

Consists of flattened, membrane-bound sacs called cisternae. Complex system of membranes running through the cytoplasm of all eukaryotic cells. Continuous with the nuclear membrane.

2 types :

RIBOSOMES Consists of a small subunit and a large subunit Ribosomes are found freely floating in the cytosol or attached to the endoplasmic reticulum Site of protein synthesis

MICROSOMES

Small membrane-bound sacs. Formed during the homogenisation procedure. Rough ER is broken into small pieces and they reseal into vesicles. i.e. microsomes Microsomes do not exist as such in intact cells.

FUNCTIONS :

The main functions of the ER are :1. To partition the cytoplasm thus allowing metabolic reactions to be separated.2. To provide a relatively large surface area for the sites of metabolic reactions.3. To act as a transport system for conveying materials from the inside to the outside of the cell.

Functions of the rough ER:TAMPINES JUNIOR COLLEGE/ BIOLOGY LECTURE JC 1 2013Lecture Notes Prepared by Mrs. Gay Guay Kim (January 2013)

ER

Rough ERCovered with ribosomes, sheet-like

sheSheet-like

Smooth ERRibosomes are absent, more tubular

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1. Transport of proteins that are synthesised by ribosomes on its surface. The proteins are for:

o Secretion out of the cell e.g. digestive enzymes, hormone insulin E.g. very prominent in enzyme secreting cells such as those of the pancreas.

o Targeted for insertion into the plasma membrane

The protein is transported through the cisternal space, where:o The proteins fold into their tertiary conformation.o The proteins are usually being extensively modified (e.g. phosphorylation or

glycosylation) during the route.

Common route for protein transport:

Rough ER Golgi apparatus Plasma membrane

Storage bodies/ Lysosomes

2. Rough ER contains enzymes on its membrane that synthesise phospholipids from precursors in the cytosol; these can be transported to and fuse with the plasma membrane for growth of the cell.

Functions of the smooth ER:

1. Site of lipid synthesis e.g. membrane phospholipids, steroid hormones Prominent in steroid secreting cells such as the interstitial cells of the testes, adrenal cortex and

epithelial cells of the intestines.

Epithelial cells of the intestines make lipids from fatty acids and glycerol absorbed from the gut and pass them on to the Golgi apparatus for export.

2. Detoxification of drugs and poisons In the liver (rich in smooth ER), the enzymes of the smooth ER carry out detoxification.

e.g. alcohol, penicillin

3. Site of carbohydrate synthesis

4. Smooth ER is used to store Ca2+ Keeps the cytoplasmic level low, allowing Ca2+ to be used as a signalling molecule.

e.g. in muscle cells, Ca2+ is used to trigger muscle contraction

GOLGI APPARATUS ( GOLGI BODY )TAMPINES JUNIOR COLLEGE/ BIOLOGY LECTURE JC 1 2013Lecture Notes Prepared by Mrs. Gay Guay Kim (January 2013)

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STRUCTURE:

Consists of a stack of flattened, membrane-bound sacs called cisternae, together with a system of associated vesicles called Golgi vesicles.

In plant cells, a number of separate stacks called dictyosomes are found.In animal cells, a single larger stack is more usual.

At the convex ‘forming’ or ‘cis’ face, new cisternae are constantly formed by fusion of vesicles that are probably derived from buds of the smooth ER.

At the concave ‘maturing’ or ‘trans’ face, cisternae break up into vesicles. Some vesicles become lysosomes.

FUNCTIONS :

1. Transport and chemically modify the materials contained within it. Prominent in secretory cells.

glycoproteins - in the Golgi body, COH is added to protein coming from the rough ER. Mucus - typical glycoprotein Zymogen - inactive form of several enzymes Synthesis of cell wall materials Lipid transport

2. Sorts and targets completed materials to different parts of the cell/ for secretion out of the cell.

3. Formation of lysosomes.

4. Vesicles budded off from the Golgi apparatus that move to fuse with the plasma membrane help to replace membrane previously lost through endocytosis.

LYSOSOMES


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lysis: splitting soma: body

STRUCTURE:

Usually spherical, 0.2 - 0.5 m in diameter. Bound by a single membrane. Sacs. Containing hydrolytic (digestive) enzymes e.g. proteases, lipases.

Enzyme contents are synthesised on the rough ER and transported via vesicles to the Golgi apparatus for further processing.The processed enzymes bud off from the trans face of the Golgi apparatus to form lysosomes.

Contents are acidic and the enzymes have a low optimum pH.

N.B. THE ENZYMES HAVE TO BE KEPT APART FROM THE REST OF THE CELL OR THEY WOULD DESTROY IT.

TYPES:

1. Primary lysosomes - enzymes are synthesised on rough ER and transported to the Golgi apparatus. Golgi vesicles containing the processed enzymes later bud off and are called primary lysosomes.

2. Secondary lysosomes - primary lysosomes may fuse with vacuoles formed by endocytosis (infolding of the plasma membrane) to form secondary lysosomes.

PEROXISOMES OR MICROBODIES Spherical. 0.3 - 1.5 m in diameter. Bound by single membrane. Derived from the ER. Presence of the enzyme catalase which catalyses the decomposition of H2O2 to water and oxygen. Examples : glyoxysomes, leaf peroxisomes, non-specialised peroxisomes.


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FUNCTION:

1. Digestion of materials

Materials digested may be made in the cell or taken into the cell from the outside.

Examples:

Materials may be taken in for food, as in the Amoeba. Therefore the secondary lysosome may also be called a food vacuole. The products of digestion are absorbed and assimilated by the cytoplasm of the cell. The secondary lysosome is now called a residual body. They may migrate to the plasma membrane and egest their contents. In certain cells, the residual bodies are stored. (e.g. heart muscle and liver cells).

Foreign particles such as the bacteria are engulfed by phagocytes (e.g. WBC and macrophages). These are then destroyed with the help of lysosomal enzymes.

Nb. Lysosomes are abundant in cells exhibiting phagocytic activity.

In the thyroid gland, cells take up thyroglobulin. Thyroglobulin is then partially hydrolysed to produce the active hormone thyroxine before the

lysosome fuses with the plasma membrane, thus secreting the hormone into the blood.

2. Autophagy

The removal of unwanted structures within the cell. The unwanted structures are first enclosed by a single membrane and this structure then fuses

with the primary lysosome to form a secondary lysosome, the autophagic vacuole, in which the unwanted material is digested.

3. Release of enzymes outside the cell.

4. Autolysis Autolysis is the self-destruction of a cell by release of the contents of lysosomes within the cell. For this reason, lysosomes are sometimes called ‘suicide bags’. Autolysis is a normal event in some differentiation processes and may occur throughout a tissue. E.g. During metamorphosis, the tadpole tail is resorbed. It may also occur after cells die.


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Which are the energy-converting organelles?

MITOCHONDRIA HARVEST CHEMICAL ENERGY FROM FOOD

STRUCTURE:

Spiral, spherical, elongate, rod-shaped, cup-shaped and even branched. Usually larger in active cells than in less active ones. Enclosed by a double membrane, each a phospholipid bilayer. Outer and inner membrane is separated by the intermembrane space. Outer membrane is smooth. Inner membrane is highly folded to form numerous cristae (singular: crista) Cristae project into the semi-fluid matrix, containing ribosomes, circular DNA and various enzymes

involved in aerobic respiration. Negative staining which stain the space around the structures themselves indicate the presence of

elementary particles on the matrix side of the inner membrane. Each particle consists of a headpiece, stalk and base.

Photographs suggest that the particles stick out from the membrane into the matrix. However, it is generally recognised that this is an artefact (structure or feature produced by the technique used and not occurring naturally) and that probably the particles are tucked into the membrane.

Mitochondria are able to change shape, and some are able to move to areas in the cell where a lot of activity is taking place. Other mitochondria assume a more fixed position e.g. as in insect flight muscles.

FUNCTION:

Site of aerobic respiration. Carry out metabolic processes that generate ATP (adenosine triphosphate) from ADP (adenosine

diphosphate) and inorganic phosphate ions by extracting energy from sugars, fats and other fuels with the help of oxygen.

Cells, which are metabolically very active, contain large numbers of mitochondria e.g. insect flight muscles, companion cells of phloem, tubule cells of kidney nephrons, liver cells.

Annotated diagram on MitochondrionTAMPINES JUNIOR COLLEGE/ BIOLOGY LECTURE JC 1 2013Lecture Notes Prepared by Mrs. Gay Guay Kim (January 2013)

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CHLOROPLASTS CONVERT SOLAR ENERGY TO CHEMICAL ENERGY


MITOCHONDRIAL DNA, RNA & RIBOSOMES Allow synthesis of its own protein,

enzymes; Also for the replication of

mitochondria

OUTER MEMBRANE Partially permeable; Permeable to oxygen,

pyruvate, ATP

STALKED PARTICLES ATP synthase link the phosphorylation of ADP

to ETC

INNER MEMBRANE Partially permeable; allows CO2 out Contain e- carriers of linear

sequences; Electrons can flow easily from one

carrier to another during oxidative phosphorylation

CRISTAE Many infolding that increase surface

area to hold more electron carriers; ATP synthase for more ATP

production

MATRIX With enzymes controlling Krebs Cycle,

link reaction and fatty acid oxidation

INTERMEMBRANE SPACE H+ accumulate as a temporary energy

store before it is used for ATP formation

STRUCTURE: Biconvex in section and circular in surface view. Surrounded by two membranes that form the chloroplast envelope. The space between the double membrane is known as the

intermembrane space. Contains chlorophyll. Chlorophyll is located on a system of membranes. System consists of many flattened fluid filled sacs called thylakoids or

lamellae which form stacks called grana (singular: granum) at intervals, with lamellae (intergranal lamellae) between the grana.

Fluid within the chloroplast is known as stroma. Stroma contains circular DNA, ribosomes, enzymes and sometimes

starch grains, lipid globules

FUNCTION: Site of photosynthesis.

Membrane system: site of light reactionStroma: site of dark reaction.

ATP synthase

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Which are the organelles that form the cell’s internal skeleton/ or are related to movement?


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CENTRIOLES

STRUCTURE:

FUNCTION:

Play a role in nuclear division in animal cells. Centrosome divides and a pair of centrioles moves to opposite poles of the cell where they help to

organize the formation of spindle fibres.

Microtubule-organising centers Pericentriolar material surrounding the centrioles in the centrosome Contains ring-shaped structures composed of tubulin Can nucleate the assembly of microtubules in animal cells

Centrosome of plants and fungi lack centrioles, but still contain microtubule-organising centers.

In motile cells, centrioles divide to produce basal bodies from which flagella and cilia develop. Cilia and flagella contain a characteristic “9 + 2 “arrangement of microtubules.

CYTOSKELETON


A pair of cylindrical, rod-like structures Long axes of centrioles are at right angles to each other. Each centriole contains nine triplets of microtubules

arranged in a ring. Found within a region known as the centrosome. Located close to the nucleus. During cell division, the centrioles replicate and

move to opposite ends of the cell. Found in animal cells and lower plant cells but absent

in higher plant cells.

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Structure and Function:

A network of protein fibres extending throughout the cytoplasm. Provides structural support, giving a cell its shape Controls cell movement e.g. white blood cell carrying out phagocytosis, movement by amoeba,

muscle cell contraction. Provides anchorage for organelles and directs their movement within the cell (e.g. movement of

vesicles from the ER to the Golgi apparatus)

Consists of: o Microtubuleso Microfilamentso Intermediate filaments

What is the other non-membranous cytoplasmic inclusion?


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RIBOSOMES

STRUCTURE: Minute organelles. Diameter: about 20 nm. Found in large numbers throughout the cytoplasm of living cells, both eukaryotic and prokaryotic. Each ribosome consists of 2 subunits, one large and one small. Made of approximately equal mass of RNA (called ribosomal RNA i.e. rRNA) and protein

2 basic types: 70S - found in prokaryotes 80S - found in eukaryotes

2 populations: Free ribosomes ER-bound ribosomes

May also occur as clusters of 2,3,4 or 5 ribosomes called polysomes or polyribosomes.

FUNCTIONS: Ribosomes are sites of protein synthesis.

Protein synthesis is under the control of the genetic code. ER-bound ribosomes make proteins that are secreted at the cell surface. Free ribosomes make proteins for use inside the cell.

What is the cytoplasmic ground substance?


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CYTOPLASMIC GROUND SUBSTANCE

Aqueous ground substance containing cell organelles and other inclusions. CYTOSOL: soluble part of the cytoplasm. 90% water. Forms a solution that contains all the fundamental biochemicals of life. Site of metabolic pathways. “CYTOPLASMIC STREAMING “ - active mass movement of cytoplasm.

What are the structures characteristic of plant cells?

The cells of higher plants contain all the organelles found in the animal cell with the exception of centrioles.

They also possess extra structures.

CELL WALLS

Relatively rigid wall. Secreted by the living cell. i.e. protoplasm.

TYPES:

1. Primary wall - wall laid down during cell division of plants.2. Secondary wall - primary wall that has undergone thickening.

STRUCTURE:

1. PRIMARY WALL


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The primary wall consists of: Cellulose microfibrils Matrix - Made of complex polysaccharides e.g. pectins, hemicelluloses

NB. 60 - 70% of the mass of cell walls is usually water. Water can move freely through the free space in the cell wall.

2. SECONDARY WALL

Sometimes the primary wall remains as the only wall e.g. leaf mesophyll cells. Extra layers of cellulose are laid down on the inside surface of the primary wall. Extensive lignification. e.g. xylem vessel, sclerenchyma.

NB. Middle lamella holds neighbouring cell walls together. Composed of sticky, gel-like magnesium and calcium pectates.

FUNCTIONS:

1. Mechanical strength and skeletal support.2. Allow development of turgidity when water enters the cell by osmosis.3. Limits and helps to control cell growth and shape.4. The system of interconnected cell walls (apoplasm) is the major pathway of movement for water and

dissolved mineral salts. NB. Symplasm: system of connected protoplasm.5. Cuticle (waxy cutin) on exposed epidermal surfaces reduces water loss and risk of infection.6. Walls of xylem vessels, tracheids and sieve tubes are adapted for long-distance translocation of

materials.7. The cell walls of root endodermal cells are impregnated with suberin forming a barrier to water

movement.8. Some walls are modified as food reserves.9. The cell walls of transfer cells develop an increased surface area.

PLASMODESMATA

Living connections that pass between neighbouring plant cells through very fine pores in adjacent walls.

VACUOLES

STRUCTURE:

Plant cells have a large, central vacuole surrounded by a membrane called the tonoplast. TAMPINES JUNIOR COLLEGE/ BIOLOGY LECTURE JC 1 2013Lecture Notes Prepared by Mrs. Gay Guay Kim (January 2013)

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Fluid found in the vacuole is called the cell sap i.e. concentrated solution of mineral salts, sugars, organic acids, oxygen, carbon dioxide, pigments and some waste products.

FUNCTIONS:

1. Osmotic uptake of water. Water usually enters the concentrated cell sap by osmosis. Important in cell expansion during cell growth, as well as in the normal water relations of plants.

2. Contains pigments in solution called anthocyans, e.g. anthocyanins3. Contains hydrolytic enzymes.4. Contains waste and certain secondary products of metabolism. e.g. crystals of calcium oxalate,

alkaloids, tannins, latex5. Some of the dissolved substances act as food reserves.

PLASTIDS

Plastids are organelles found only in plant cells. They are surrounded by two membranes.

TYPES:

1. Chloroplasts2. Chromoplasts3. Leucoplasts

How are the eukaryotic organelles classified under four functional categories?

EUKARYOTIC ORGANELLES AND THEIR FUNCTIONS


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General Function: Manufacture

Nucleus DNA synthesis; RNA synthesis; assembly of ribosomal subunits (in nucleoli)

Ribosomes Polypeptide (protein) synthesis

Rough ER Synthesis of membrane proteins, secretory proteins, and hydrolytic enzymes;Formation of transport vesicles

Smooth ER Lipid synthesis;Carbohydrate metabolism in liver cells;Detoxification in liver cells;Calcium ion storage;

Golgi apparatus Modification, temporary storage, and transport of macromolecules;Formation of lysosomes and transport vesicles.

General Function: Breakdown

Lysosomes (in animal cells and some protista)

Digestion of nutrients, bacteria, and damaged organelles;Destruction of certain cells during embryonic development.

Peroxisomes Diverse metabolic processes, with breakdown of hydrogen peroxide by-product

Vacuoles Digestion (like lysosomes);Storage of chemicals;Cell enlargement; Water balance.

General Function: Energy Processing

Chloroplasts(in plants and some protista)

Conversion of light energy to chemical energy of sugars

Mitochondria Conversion of chemical energy of food to chemical energy of ATP

General Functions: Support, Movement, and Communication Between Cells

Cytoskeleton (including cilia, flagella and centrioles in animal cells)

Maintenance of cell shape;Anchorage for organelles;Movement of organelles within cells;Cell movement;Mechanical transmission of signals from exterior of cell to interior

Cell walls (in plants, fungi and some protests)

Maintenance of cell shape and skeletal support;Surface protection;Binding of cells in tissues;

Extracellular matrix(in animals)

Binding of cells in tissues;Surface protection;Regulation of cellular activities;

Cell junctions Communication between cells;Binding of cells in tissues;


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Cell Ultrastructure 2013 Reading Notes (1)

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