2.1 Cell Structure And Cell Ion

2.0 CELL STRUCTURE AND ORGANISATION

2.1 Cell Structure and Function  Cell

– the basic unit of living thing  Living component of a cell is called the protoplasm  Protoplasm consist of the cytoplasm and the nucleus and surrounded by a plasma membrane  The cytoplasm contains organelles

 The

organelles consist of a) nucleus b) mitochondria c) chloroplasts d) vacuoles e) ribosomes f) lysosomes g) golgi apparatus h) endoplasmic reticulum i) centrioles

Exercise 1.

Draw a plant and an animal cell.

The Cellular Components Of Animal And Plant Cell And Their Functions a) Cell membrane - general terms that refers to any membrane found within a cell - the cell surface membrane which encloses the content of the cell is called the plasma membrane - made of proteins and lipids - form a boundary which separates the content of a cell from outer environment - semi-permeable and act as a selective barrier - regulates the movement of substances into and out of the cytoplasm

b) Cell wall - only can be found in plant cell - a rigid outer layer that surrounds the plasma membrane - composed of cellulose, a tough and fibrous carbohydrate - permeable to all fluids - provide mechanical support - give shape - protect plant cell from rupturing

c) Nucleus - largest organelle in the cell - consist of 3 main component i) Nuclear envelope – separates the nucleus content from the cytoplasm ii) Chromatin – carries the genetic material (DNA –deoxyribonucleic acid) iii) Nucleolus – darker and dense region - carry genetic information which determines the characteristics and function of a cell - controls all the activities which take place in the cell

d) Vacuole - a fluid-filled sac, surrounded by tonoplast (semi-permeable membrane) - the fluid inside the vacuole is called cell sap - act as a storage place in a cell - contains water, organic acids, sugars, amino acids, mineral salts, waste substance, pigments and metabolic by-product - in freshwater organism (Paramecium sp.) have contractile vacuole to regulate water balance - support herbaceous plants from wilting easily

e) Mitochondria - singular-mitochondrion - the site of cellular respiration which release energy when food substances (glucose) are broken down by enzymes in the mitocondria - energy is released in the form of ATP (adenosine triphosphate) which can be readily used by cells

f) Endoplasmic Reticulum (ER) - consist of a network of folded membranes forming interconnected tubules/sac in the cytoplasm - the membranes are continuous with the nuclear membrane

- 2 forms (i) Rough ER – the outer surface cover with ribosomes - transports proteins (enclosed in vesicles) made by the ribosomes can be transported from one part of the cell to another

(ii) Smooth ER – smooth outer surface, lack of ribosomes - the site of important metabolic reactions (synthesis of lipids and detoxification of drugs and poison)

g) Ribosomes - compact, spherical organelles found attached on the surface of rough ER or suspended freely in the cytoplasm - consist of two sub-unit, one small and one large, each comprises a type of ribonucleic acid (RNA) and protein - site of protein synthesis - use information carried by the chromosome to make protein

h) Golgi apparatus - consist of a stack of flattened membranous sacs - new membrane is continuously added to one end and buds of as vesicles at the other end - function as a processing, packaging and transporting centre of carbohydrates, proteins, phospholipids and glycoprotein

i)

Lysosomes - membrane bound sac that contain hydrochloric acid that digest and break down complex organic molecule (protein, lipids, polysaccharides and nucleic acid) - eliminate damage or worn out organelles and help the cell renew itself - can fuse with food vacuoles, digest the content and the breakdown product pass into cytoplasm and become the cell nutrient

j) Centrioles - small cylindrical structure that occur in pairs located just outside the nucleus - composed of complex arrangement of microtubules - not present in plant cell - form spindle microtubules during cell division

k) Chloroplast - typically lens-shaped - membranous structure contain green pigment chlorophyll - chlorophyll captures the energy of sunlight and converts light energy into chemical energy during photosynthesis

Exercise 1. Complete this table: Cellular components 1. Nucleus 2. Mitochondria 3. Golgi apparatus 4. Lysosomes

Functions

Answer Cellular components 1. Nucleus

2. Mitochondria

3. Golgi apparatus

4. Lysosomes

Function • Controls the activities of a cell • contains DNA which determine the characteristics of a cell and its metabolic reaction • the site of cellular respiration which releases energy in the form of ATP • a processing, packaging and transport centre of carbohydrates, proteins and glycoproteins •as a digestive compartments

2.2 Comparison between the structure of animal and plant cells 

Differences between animal and plant cells

Structure/ characteristic Shape Cell wall Chloroplast Vacuoles Food storage Centrioles

Animal cells

Plant cells

Answer Structure/ characteristic

Animal cells

Plant cells

Shape

Do not have a fixed shape.

Have a fixed shape.

Cell wall

Do not have cell walls.

Have cell walls.

Chloroplast

Do not have chloroplasts.

Have chloroplast

Vacuoles

Usually small and numerous ,filled with food or water.

Have a large central vacuole.

Food storage

Carbohydrate is stored in the form of glycogen.

Carbohydrate is stored in the form of starch.

Centrioles

Have

Do not have

 The

similarities between animal and plant

cells

Both have a nucleus, cytoplasm, a plasma membrane, Golgi apparatus, mitochondria, endoplasmic reticulum and ribosomes.

The Density of Organelles in Specific Cells  Different

cells in the body perform different

functions  The density/abundance of certain organelles found in a cell is related to the specific function  The density of organelles in specific cells.doc