Biology Form 4 Chapter 2 Notes

8/10/2019 Biology Form 4 Chapter 2 Notes

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Cell Structure and

Function


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All living things are made up of basic units

called cells.

Cells vary in shape, sizes and content

depending on their function.

A light microscopeis usually used to

help us observe microscopic cells.


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The living component of a cell is called

protoplasm.

Protoplasm = cytoplasm + nucleus

Protoplasm surrounded by plasma

membrane.

Plant cells have an outer boundary called

the cell wall.


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Animal cell

Plant cell


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Cell Parts and Structures

With electron microscopes, scientists are able to seethe cellular components of a cell in greater detail.

The cytoplasm contains structures called organelles.

Organelles perform specific function which enable the

cell to function as a unit of life.


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Animalcell


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P

lantcell


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Controls cellular

activities.

Nucleus membrane

controls inflow and

outflowof material to

and from nucleus

Nucleolus acts as site

of ribosome

construction. Chromosome carries

hereditary information.


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Acts as a mediumwhere biochemical

reactions and most

living processes

occur within the cell.

Provides the

organelles with

substances obtainedfrom external

environment.


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Separates the content

of the cell from its

external environment.

Regulates the

movement of

substances enteringand leaving the cell.

Allows the exchange

of nutrients,

respiratory gases and

wastes products

between the cell and

its environment.


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Chlorophyll captures theenergy of sunlightand

converts light energy into

chemical energy duringphotosynthesis.

The green pigment of

chlorophyllgives plantstheir colour.


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Stores chemicals

such as organicacids, sugar, amino

acids, mineral salts,

oxygen, carbondioxideand so on.

Regulates water

balance in plantcells.


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Maintains the shape of plant cells.

Provides mechanical strength and supporttoplant cells.

Protectsplants cells from ruptur ing due to the

movement of excess water into the cells.


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Forms a network of

transportation within

the cell.

Rough endoplasmic reticulum

(has ribosomes attached to itssurface)

Transports protein which is

synthesized in ribosomes.

Smooth endoplasmic reticulum

(does not have ribosome attach toits surface)

Transports and

synthesized fat and

glyserol


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Site of proteins synthesis.

They are either bound to the

endoplasmic reticulum or lie free in

the cytoplasm.


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The sites of cellular

respiration. Principle site of

energy production.

Energy generated orreleased in the form

of ATP (adenosine

triphosphate).


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Functions as a processing, packaging

and transport centreof carbohydrates,

proteins and glycoproteins.

These materials will be membrane-bound

and secrete through vesicles.


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As a digestive

compartments.

In certain unicellularorganisms, lysosomes

fuse with food vacuoles

and dispense their

enzymes into thesevacuoles to digest the

contents of the vacuoles

Lysosomes


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Comparison of

an Animal Cell

& a Plant Cell


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Both has nucleus, cytoplasm,

mitochondrion, ribosome, cell

membrane, rough endoplasmic

reticulum, smooth endoplasmic

recticulum and Golgi apparatus

Similarities

Animal Cell Plant Cell


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Animal Cell Plant CellDifferences

Do not have fixed shape Shape Have a fixed shape

Do not have cell walls Cell walls Have cell walls

Do not have vacuoles. If

present, vacuoles are usuallysmall and numerous

Vacuoles Have a large centralvacuole

Do not have chloroplasts ChloroplastsAll green plants have

chloroplast which contain

chlorophyll

Have centrioles centrioles Do not have centrioles

Carbohydrate is stored in the

form of glycogen Food storage

Carbohydrate is stored in

the form of starch


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The Density ofOrganelles in

Spesific Cells


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The number of organelles in each cell varies

according to type of organism and nature of the

cell.

For example,

more active cellswill possess more

mitochondriathan less active cells.

Abundant chloroplastsare found in the

palisade mesophyllcells than other parts of

the leaves.


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Require energy to propel through the uterus

towards the Fallopian tubes, so that

fertilisation can take place.

Sperm cells

High density of ______


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Contract and relax to

enable movement and

flight

Muscle cells


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Require large amounts of energy

during active cell division to produce

new cells

Cells in meristems



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Mesophyll palisade cells

Absorb sunlight during photosynthesis


Biology Form 4 Chapter 2 Notes

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