Biology Form4 Chapter2 Cell Strucuture and Organisation

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• To state the necessity for cell specialisation in multicellular organisms as compared to unicellular organisms

• To describe cell specialisation in multicellular organisms

• To describe cell organisation in the formation of tissues, organs & systems in multicellular organisms.

CELL ORGANISATION• Organisms are divided into 2 : unicellular

organisms & multicellular organisms• Unicellular organisms :- single-cell organisms

such as Amoeba sp. & Paramecium sp.• Each cell is able to carry out all the functions of

life independently.• Multicellular organisms :- larger organisms

with more than one cell• Need many different types of cells to carry out

all the different functions of life• Each cell has to change in shape & form during

cell specialisation to become specific cells in order to perform different functions


• Simple organisms consisting of only one cell each

• Able to carry out all living processes in order to survive

• Examples : Amoeba and Paramecium (protozoa)

Membrane : respiration – gaseous exchange by simple diffusion. CO2 & any dissolved diffuses out into the water

Cytoplasm : clear on the outside (ectoplasm) & grainy on the inside (endoplasm)

Contractile vacuole : water continually enters by osmosis. Contractile vacuole swells up full expels the water from the cell = osmoregulation

Amoeba sp.Live in water, including water in the soil.Have no fixed shape.

Movement : form a pseudopodium (‘false-foot’) – extension of cytoplasm.

Reproduction : Binary fission – when it has grown to certain size, its nucleus divides to form two daughter nuclei then the cytoplasm divides and two daughter Amoeba are formed. Under adverse conditions such as during a drought, its divides by spore formation.

Feeding : phagocytosis – pseudopodium moves round a food particle and takes it into its cytoplasm where it forms a food vacuole. Enzymes are added to digest the food. Any waste is left behind as it moves away.

Membrane : respiration – gaseous exchange by simple diffusion. CO2 & any dissolved diffuses out into the water

Contractile vacuole : water continually enters by osmosis. Contractile vacuole swells up full moves to the side of the membrane expels the water from the cell = osmoregulation. Alternate.

Cilia : tiny hairs that cover the whole surface

Oral groove : leads food to gullet

Paramecium sp.

Lives in stagnant water containing decaying plant material. Have fixed shape, like a slipper.

Movement : rhythmic beating of the water by the cilia (rows of tiny hair) propels the Paramecium along. If it encounters to an obstacle, it stops, backs up, turn 30o then moves off. (Avoiding reaction)

Feeding : the cilia around the oral groove brush the food down to the gullet. A food vacuole formed. Enzymes are added to digest it and the nutrient diffuse into the food cytoplasm. Waste is released through a weak spot in the membrane called the anal pore.


•Through binary fission.

•Also can reproduce sexually by conjugation.

• Two individual come together and exchange parts of their nuclei. They then separate and each can later divides to give four new cells.



•Organisms that have more than one cell

•More complex than unicellular organisms

•Need many different types of cells to carry out their life process.

•Achieved through cell specialisation and cell organisation.



• Achieved through the process of DIFFERENTIATION where the cells begin to change in shape and form as they grow.

• The cell acquire special structures and become specialised cells.

• Each type of cell performs only one specific function. This is known as division of labour.

• Through these, different functions in the body can be performed at the same time and can be carried out smoothly and efficiently.

CELL•Basic units of life in all organisms.•The structural features of cells

are related to their functions.•Cells undergo differentiation to

acquire special structures and become specialised cells with specific functions.

Examples of animal cell

Red blood cells

Nerve cells

Muscle cells

Sperm cells

Examples of plant cells

Guard cell

TISSUES• A group of similar cells that work together

to perform a specific function• Four main types of animal tissues :

epithelial tissues, nervous tissues, muscle tissues & connective tissues.

Mnemonic (EN.MyC)• The four main types of plant tissues :

epidermis tissue, meristem tissue, vascular tissue & ground tissue

MNEMONIC EM..VideoGames!

Types of animal cell

Characteristics Functions

Epithelial tissues •Consist of epithelial cells arranged in a continuous layer

•Cover the body surface or line the cavities within the body•Protect the underlying cells from mechanical injuries•Absorb food and water by diffusion•Form secretory gland

Nervous tissues •Consist of nerve cells called neuron•Found in brain and spinal cord

•Send & receive impulses to coordinate the activities of the body

Muscle tissues •Consisting of muscle cells which can contract to perform work•3 types : smooth muscle, skeletal muscle & cardiac muscle

•Cause body movement by means of contraction

Connective tissues •Consist of elastic & non-elastic fibre•Blood, adipose tissues, cartilage & bone.

•Join together body structures, as well as protect, hold and support the cell in the body•Can store & transport material

Types of plant tissues

Characteristic Functions

Epidermis tissue

•Consisting of one layer of cells•Examples : epidermis of leaves, stems & roots

•Covers the entire surface of the plant•Protect underlying tissues from physical damage & infection•Reduces water loss•Epidermal cells of leaf differentiate to become guard cells while those at the root, become root hair cells.

Meristem tissue •Consists if undifferentiated cells which are able to divide•Occurs at the tip of roots & shoots & in the cambium of stems & roots

•Produces new cells by cell division

Vascular tissue •Consists of xylem tissues & phloem tissues

•Transport water & mineral salts from roots to the stems & leaves by xylem tissues•Transport dissolved nutrients such as glucose from the leaves to the roots & stems by phloem tissues•Xylems tissues provide support to the plants

Ground tissue •Consists of parenchyma mesophyll tissues, collenchyma & sclerenchyma tissues

•Produces food by photosynthesis & stores food produced•Provides support & strengthens the plant


• A group of different tissues that work together to perform a specific function

• Examples of organs in animal: heart, kidneys, lungs, skin & stomach.

• Examples of organs in plant : leaves, stems, roots & flowers.

• Certain organ perform more than one function.

SYSTEMS• Several organs which work together to

carry out a specific function• The human body has twelve different

systems• All the system work together to form an

organism• Flowering plant has two main systems :

root system, shoot system


• Integumentary

• Circulatory

• Endocrine

• Lymphatic

• Nervous

• Digestive

• Muscular• Excretory• Skeletal• Respiratory• Reproductive




conditions imposed on the organism such as the physical and chemical factors in its surroundings.

• INTERNAL ENVIRONMENT : the conditions created inside the organism by its own metabolism, its reactions to external changes and other activities

• EXTRACELLULAR FLUID : the fluid that bathing the cells, provides the medium in which they have to live

• HOMEOSTASIS : the process to regulate the physical & chemical factors in the internal environment so that it is always constant & at its optimal condition for the cells to function efficiently (the maintenance of the internal environment of a living organism at a constant normal level or between narrow limits).

INTERNAL ENVIRONMENT of MULTICELLULAR ORGANISM• A multicellular organism consists of all the

different organ systems, each specialised to carry out certain functions.

• They work together as an integrated & coordinated unit.

• To stay alive, the cells in a multicellular organism must remain bathed in a FLUID that offers nutrients & carries away metabolic wastes.

• The combined contributions of individual cells, organs & organ systems help maintain the STABLE INTERNAL ENVIRONMENT required for individual cell survival.

• Any increase in the value of a physical or chemical factor will trigger the homeostatic mechanism to bring it back to normal (negative feedback mechanism)


blood pressure & osmotic pressure

• CHEMICAL FACTORS – salt & sugar content & pH value.


• Body temperature MNEMONICS Cu, Mau Ikut Nenek Enggak?• Blood glucose level MNEMONIC Dahi Engkau Cantik!• Blood pHMNEMONIC Roti Canai Enak• Concentration of oxygen & carbon dioxide in the

bloodMNEMONIC RaCuN• Osmotic pressure of bloodMNEMONIC ENCEk


• To regulates & maintains human body temperature at 37oC.

• Body temperature rises Thermoreceptors (NS) detect contol centre in hypothalamus activates effectors (blood vessel & sweat gland) blood vessel dilate near the surface of the body increase the heat loss sweat gland produce more sweat to low the body temperature through evaporation BT restored to normal