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CHAPTER 2 :CELL STRUCTURE & CELLORGANISATION

2.1 Cell Structure & Function2.2 Cell Organisation


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2.1 CELL STRUCTURE &FUNCTION

Learning Outcomes :1. Draw & label an animal cell and a plant cell

2. Identify the cellular components of an animal

cell & a plant cell

3. State the functions of the cellular components

in an animal and a plant cell

4. Compare & contrast an animal cell with a plant

cell

5. Relate the density of certain organelles with

the functions of specific cells.


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HISTORYRobert Hooke (1665) was first

discovered the cell structure of

plantHe examined fine slices of cork

with a primitive microscope

He saw many box-like structures ,then he called cells, from Latin forlittle rooms.


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THE CELL THEORY

(Schleiden M & Schwann T) All living organisms are made up of one or

more cells

New cells are formed by the division ofpre-existing cells

Cells contain genetic material of an

organism which is passed from the parentcells to daughter cells

Cells are the basic unit of structure &function in living things


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ORGANELLES specialised

structures which are eachsurrounded by its own membrane &perform specific function


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PLASMAMEMBRANE

Thin, semi-permeable

Made of protein, lipid Controls the

movement ofsubstances in and outof the cell

Non-organelle


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CYTOPLASM Jelly-like substance

that contains water &mineral salts

Contains organellesand food such ascarbohydrates(glucose)

Medium for metabolic

reactions Supplies the

substances requiredby organelles

Non-organelle


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CELL WALL Thick layer outside

the plasma membrane

Made up of cellulose,fully permeable

Maintains the shapeof the plant cells

Provides mechanicalsupport

Non-organelle


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NUCLEUS Spherical shape with

double membrane

Contains nucleolus,

chromosomes,nucleoplasm & nuclearmembrane

Controls & regulates

all the activities of cell Contain the heredity

factors responsible forthe traits


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RIBOSOME Small particles

consisting of RNA

Exists freely in the

cytoplasm or on the

surface of the

endoplasmicreticulum

Synthesis of protein


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ENDOPLASMIC RETICULUM

A system of membrane-enclosed tubules closelypacked together andcontinuous with the nuclearmembrane

RER has ribosome, SERdoes not have

Transport system forprotein & lipids within thecell

RER transport protein toother part of cell

SER stimulates thesynthesis of lipids &cholesterol & transport

within the cell


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GOLGI APPARATUS Vacuolar region surrounded

by a complex meshwork ofvesicles budding off at its end

Received protein & lipids fromER & modify them to form

specific secretion such asenzymes & hormones

Pack the secretions formedinto secreting vesicles &

transport them to plasma

membrane to be secreted Controls the secretory activity

of cells

Formation of lysosomes


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VACUOLE Filled with cell sap,

surrounded by semi-permeablemembrane called thetonoplast

Contain water, sugar

& dissolved minerals Maintain turgidity of

cells in plants


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MITOCHONDRIA Rod-shape with a

double membrane

Outer membrane is

smooth, innermembrane is folded toform cristae

Known as power-house of the cell

Releases energy as itis the site for aerobicrespiration


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CHLOROPLAST Disc-shape organelle

with a doublemembrane

Consist of an orderlyarrangement of granawithin the stroma.Granum containschlorophyll

Site of photosynthesis Trapped light energy

and change it intochemical energy


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LYSOSOMES

Membrane-boundvesicles found in animalcells

Contain enzymes whichcontrol breakdown ofprotein & lipids

Contain enzymes thatdigest aged or defectivecell components or

materials taken in by thecell from itsenvironments such asfood particles orbacteria.


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CENTRIOLES

A pair of smallcylindricalstructures(microtubules)

Form spindlefibre for celldivision


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COMPARE & CONTRAST

ANIMAL CELL SIMILARITIES PLANT CELL

A plasma membrane surrounding the

cytoplasm

Both contain nucleus & cytoplasm

Both contain organelles such as mitochondria,

ER, Golgi apparatus & ribosomes


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ANIMAL CELL DIFFERENCES PLANT CELL

Smaller than plant cell SIZE Larger than animal cell

Irregular shape SHAPE Often regular in shape

Absent CELL WALL Present

Absent CHLOROPLAST Present

No large vacuoles. If

present, small &

numerous.

VACUOLES Large central vacuolefilled with cell sap

In a form of glycogen in

liver & muscle tissues

FOOD STORAGE In a form of starch

Present CENTRIOLES Absent

Some animal cell have

cilia or flagella

CILIA & FLAGELLA Absent

RELATIONSHIP BETWEEN THE


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RELATIONSHIP BETWEEN THE

STRUCTURE OF AN ANIMAL CELL & A

PLANT CELL


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The number of specific organelles in a cell

varies on the type of cell and its function.

Active cellmany mitochondria to provide

enough energy for its activities. Eg. : sperm

cells, flight muscle cell (insects & birds)

Cell in meristems of plant shoot & root

Green plantsmore chloroplasts to carry out

photosynthesis such as palisade mesophyll cells

and spongy mesophyll cells, also guard cells.


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EXERCISE 2.1

1. What are the organelle structures of a

cell?

2. What are the functions of each structuredescribe above?


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