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Chapter 2: Cell Structure and Cell Organisation

2.1 Cell Structure and Function

1. Living organisms are made of basic units called cells.

2. Cytoplasm contains structures called organelles.

3. Organelles perform specific functions which enable the cell to function as a unit of life.

Cellular components of animal and plant cells.

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Cell membrane1. Made of proteins and phospholipids.

2. Forms a boundary which separates the content of a cell from the outer environment.3. Plasma membrane is semi permeable and acts as a selective barrier.

4. Function: Regulates the movement of substances into and out of the cytoplasm.

Cell wall1. Rigid outer layer that surround the plasma membrane of plant cells.

2. Composed of cellulose.

3. Permeable to all fluids because it has tiny pores that allow substances to move freely into

and out of the cell.

4. Function: a) Gives shape to a plant cell and provides mechanical support.

b) Protects the plant from rupturing due to the excessive intake of water.

Cytoplasm

1. Region between the nucleus and the plasma membrane.

2. Consists of a jelly-like matrix in which organelles are suspended.3. Contains organic and inorganic substances.

4. Function: a) Acts as a medium for biochemical reactions in the cell.b) Provides substances obtained from the external environment to the

organelles.

Nucleus1. Enclosed by a nuclear membrane.

2. Chromatin is contained within the nucleoplasm.

3. Chromosomes carry genetic information which determines the characteristics and

functions of a cell.

4. Function: Controls all the activities which take place in the cell.

Vacuole

1. Fluid filled sac which is surrounded by tonoplast, a semi-permeable membrane.

2. The fluid contained in a vacuole is called cell sap.

3. Function: Acts as a storage place in a cell.

4. The cell sap contains water, organic acids, sugars, amino acids, mineral salts, waste

susbstances, pigments and metabolic by-products.

5. The cell sap in a vacuole supports herbaceous plants so that they do not wilt easily.

Mitochondria

1. Small spherical or cylindrical-shaped organelle.2. Involved in cellular respiration.

Ribosomes1. Compact spherical organelles found attached to the surface of rough endoplasmicreticulum or suspended freely in the cytoplasm.

2. Consists of two subunits, one small and one large, each of which comprises a type of

ribonucleic acid (RNA) and protein.

3. Function: Site of synthesis of proteins.

4. Use information carried by the chromosomes to make these proteins.

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