Chapter 2 : Cell Structure and Cell Organisation

Unicellular – A single cell performs all the basic life process. Example: Amoeba sp., Paramecium sp.,

Multi cellular – An organism consists of more than one cell. Each group of cell specialized to carry our life processes. Example: Homo sapien (human), animals and plants. It has five levels of organisation

Cells: basic units of structure and function.
Example: Red blood cells and xylem vessel cells.

Tissues: made up of cells with similar in structure and function.
Example: Epithelial tissues and vascular tissues.

Organs: made up of tissues that perform a specific function.
Example: Heart and flower.

System: two of more organs that perform a specific function.
Example: Digestive system and root system.

Organisms: whole living thing that carry out all the basic life processes.
Example: Human and durian tree.

Cell Organisation (Unicellular) in Amoeba sp. (lives in freshwater ponds) and Paramecium sp. (lives in soil and moist area)

1. Cell structure

Amoeba sp.: plasma membrane, food vacuole, contractile vacuole, pseudopodia, nucleus, ectoplasm, endoplasm.

Paramecium sp.: food vacuole, posterior contractile vacuole, cytostome, gullet, oral groove, cilia, macronucleus, micronucleus, anterior contractile vacuole.

2. Locomotion

Amoeba sp.: Pseudopodium (false foot) helps it to move forward slowly and it is known as amoeboid movement.

Paramecium sp.: Hair-like cilia to beat against water. It beats its cilia backwards diagonally (swim forward) and it rotates on its axis. It beats its cilia forward (swim backwards).

3. Feeding

Amoeba sp.: Omnivore. Eat bacteria, plant cells, algae and other microscopic organisms.

Entrapment – extend pseudopodium.

Engulfment – engulf tiny food (phagocytosis) with its pseudopodia.

Digestion – food enclosed in food vacuole

Absorption – enzyme digests the bacteria

Egesting – expel indigestible material.

~Paramecium sp.: Eat bacteria, organic material and other microscopic organisms.

Sweeping – movement of cilia. Food moves along the oral groove into the gullet and cytostome.

Digestion – food vacuole circulates round the cell.

Elimination – undigested food is eliminated at the anal pore.

4. Reproduction

Amoeba sp.: two types of reproduction.

Binary Fission – nucleus divides (favourable condition) and then follows by division of cytoplasm. Two daughter cells are formed (mitotic division).

Spore Formation – spores form (bad condition) and germinate into new amoeba under favourable condition.

Paramecium sp.: two types of reproduction.

Binary Fission – micronucleus undergoes mitosis (favourable condition). Macronucleus begins to elongation and form two. Cell content divide and two daughter cells are formed.

Conjugation (Sexual reproduction) – two same species parent paramecia exchange genetic material of their micronuclei. Each parent divides and forms four daughter cells.

5. Osmoregulation

Amoeba sp.: water moves into the cell by osmosis and prevention of bursting, it has a contractile vacuole.

Paramecium sp.: water moves into the cell by osmosis and prevention of bursting, it has two contractile vacuoles.

6. Respiration

Amoeba sp. and Paramecium sp. (both): exchange gases throughout the whole cell membrane

7. Excretion

Amoeba sp. and Paramecium sp. (both): waste products are ammonia and carbon dioxide by diffusion. Solid waste in paramecium is expelled through its anal pore.

Cell Organisation (Multicellular) in Human

Cells: Epithelial cells, muscle cells, white blood cells, red blood cells, sperm, nerve cells.

Tissues: Epithelial tissue, smooth muscle tissue, connective tissue, skeletal tissue, nerve tissue.

Organs: Stomach, heart, kidney, lung, liver.

Systems: Circulatory system, respiratory system, digestive system, excretory system, muscular system, lymphatic system, integumentary system, skeletal system, nervous system, endocrine system, reproductive system.

Organisms: Human.

Cell Organisation in Plant

Cells: Parenchyma cells, collenchyma cells, sclerenchyma cells, epidermal cells.

Tissues: Epidermal tissue, meristem tissue, vascular tissue.
Organs: Leaf organ, flower organ, stem organ, root organ.

Systems: Shoot system, root system.

Organisms: Plant.

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