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Principle of 

biology

Chapter one(Cells and tissues)

Level Definition  Examples

in plants

 Examples in

animals

Cell It’s the structural 

and functional 

unit of the body

 Palisade

cells

 Liver cell 

Tissue A group of similar 

cells working together to

 perform a shared 

 function

 Xylem ,

 phloem

 Nervous

tissue ,muscular 

tissue

Organ A group of 

different tissues

working together 

to perform a

specific function

leaf , root Heart ,

stomach

 Syste

m

 A group of 

different organs

working together 

to perform a body

 function

 Root 

system

 Digestive

system and 

respiratory

system

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Word Definition

Organelle It’s a living structure in a cell such as vacuole,

nucleus, chloroplast.

Cell

specialization

(modification)

It means a change in shape or structure or both,

to be adapted to carry out a particular function.

Cell physiology It’s the studying of cell function and different

organelles.

Structure Properties FunctionNuclues Contains DNA • Control activities of 

the cell and cell

division.

• Carries the inherited

information.

Cytoplasm Contains protein and

water• Keep the cell alive

because all chemical

reaction take place

inside it.Chloroplast Contains chlorophyl • Absorb light energy

and convert it to

chemical energy

during photosynthesis

process.

Cell

membrane

Made of carbohydrate ,

proteins , lipids and is

semi-permeable .

• protect the cell.

• Stop the cell contents

from escaping.

• Control the passage of 

substance in and out of 

the cell.

Cell wall Made of cellulose and is

fully permeable (dead).• Support , protect and

shape the cell.

• It allows the freely

movement of different

substances .

Chromosomes Contains protein unitand DNA and is found•

Carries all genes , eachgene is responsible for

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in nucleus . a certain character.

Lysosome Contains hydrolytic

enzymes• Digest non-function

organelles.

Mitochondria Present in the form of spherical rod-like.

• Source of energy

Vacuole Contains a fluid and

surrounded by a

membrane

• Regulates absorption

of water by osmosis .

• Helps in storage .

  Differences between plant and animal cell

Plant cell Animal cell

Has cell wall Has no cell wall

Has cell sap vacoule Has no or temproray

vacuole

Has chloroplast Has no chloroplast

Usually contains

stored starch

Usually contains stored

glycogen

Has small and lateralnuclues

Has one or largecentralized nuclues

 

Similarities in both plant and animal cell :- 

1. Cell membrane

2. Mitochondria

3. Cytoplasm

4.Nuclues

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Plant cell:

1. new cell about to divide.

2. the nucleus divides first, a new cell wall

develops to separate the two cells.

3. the cytoplasm makes celluolseon each side of the

new cell wall.

4. the vacuole join up to form one vacuole ,the

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 Animal cell :-

1. New cell about to divide .

2. The nucleus divides first.

3. The nucleus gets separated and the

cytoplasm pinches between the nucleus.

4. Two cells are formed , one become adapted

(specialized) and the other one will divide

again.

How can you make tissue culture then

mention its function?

Tissue culture is made by separating the cells by means of 

enzymes then making it grow and divide in dishes containing 

nutrient solution. It is used to study cells and cell division.

Adaptation of cells:-

• Nerve cells:they are very long about to coduct

electrical impulses to or from the brain

• Ciliated cells:they contain cilia to move mucus and 

dusts.

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• Root hair cells:large in number and has a finger

like projection to increase surface area of 

absorbing water and minerals. Contains a lot of 

mitochondria for production of energy requiredto absorb mineral by active transport. Contains a

large concentrated sap vacuole to absorb water by

osmosis.

• Xylem vessels:xylem vessels (dead tissues) have

lignified cells to rise water up by capillary action.

• Phloem tubes:phloem tubes (living tubes) to carryfood from leaf to all parts of plant.

• Red blood cells:has no nucleus and has biconcave

shape and has haemoglobin to carry oxygen.

• White blood cells.has nucleus and is specialized

for engulfing harmful bacteria.

Magnification = Length of image

Length of object

 Note: that human has no haploid nucleus but

diploid nucleus

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Here are some questions from paper one :-

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O level Biology 1

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O level Biology 1

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O level Biology 1

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O level Biology 1

Mohamed Amr