PREPARED BY:

Ahmad Ikmal ‘Akif bin Abdul Khalil

4 UTM

2.1 CELL STRUCTURE AND FUNCTION

Living organisms are made of basic units called cells.

Living component of a cell is called protoplasm which is consists of cytoplasm and nucleus.

The protoplasm is surrounded by a thin layer of plasma membrane.

Both animal and plant cells have these components.

PLANT CELLS ANIMAL CELLS

CELL MEMBRANE CELL WALL

•The membrane at the surface which encloses the content of a cell-plasma membrane.

•It regulates the movement of substances into and out of the cytoplasm.

• Rigid outer layer that surrounds the plasma membrane of plant cells.

• Functions :

1. gives shape to a plant cell

2. provides mechanical support for plant cell

3. Protects the plant cell from rupturing due to the excessive intake of water.

CYTOPLASM NUCLEUS

•The region between the nucleus and the plasma membrane.

•Contains organic and inorganic substances and acts as a medium for biochemical reactions in cell.

•Function : provides substances obtained from the external environment to the organelles.

•Appears as large,dense,spherical organelle enclosed by a nuclear membrane.

•Contains nucleoplasm and dark spherical structure called nucleolus.

•Function : controls all the activities which take place in the cell.

VACUOLE MITOCHONDRIA

•A fluid-filled sac which surrounded by tonoplast.

•The fluid contained in a vacuole-cell sap

•Function : acts as a storage place in a cell.

•The cell sap in a vacuole supports herbaceous plants.

•Appear in electron micrographs

•Involved in cellular respiration- releases energy when food substances such as glucose are broken down with the help of enzymes present in the mitochondria.

RIBOSOME ENDOPLASMIC RETICULUM

• Compact spherical organelles found attached to the surface of rough endoplasmic reticulum.

• Functions :

1. Synthesis protein

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

•Two types of emdoplasmic reticulum:

Rough endoplasmic reticulum –transports proteins made by the ribosomes

Smooth endoplasmic reticulum – the site of important metabolic reactions,including synthesis of lipids and detoxification of drugs and poisons.

GOLGI APPARATUS LYSOSOMES

•Consists of a stack of flattened membranous sacs

•Function : processing, packaging and transporting centre of carbohydrates, proteins, phospholipids and glycoproteins.

•Are membrane-bound sacs that contain hydrolytic enzymes.

•These enzymes digest or break down complex organic molecules such as proteins and nucleic acids.

•Also digest bacteria by breaking down the bacteria cell wall.

CENTRIOLES CHLOROPLAST

•Are a pair of small cylindrical structures located just outside the nucleus.

•Are composed of a complex arrangement of microtubules.

•Typically lens-shaped

•Chloroplasts contain the green pigment which is called chlorophyll.

•Chlorophyll traps sunlight and converts light energy into chemical energy during photosynthesis.

COMPARISON BETWEEN THE STRUCTURE OF ANIMAL AND PLANT CELLS

SIMILARITIES

ANIMAL CELLS PLANT CELLS

Nucleus Present Present

Cytoplasmic streaming

Present Present

Ribosomes Present Present

DIFFERENCES

ANIMAL CELLS PLANT CELLS

Chloroplast Animal cells don't have chloroplasts

Plant cells have chloroplasts

Plasma Membrane Yes; only cell membrane Yes; cell wall and a cell membrane

Centrioles Always present Only present in lower plant forms

Lysosomes Lysosomes occur in cytoplasm

Lysosomes usually not evident.

Vacuole One or more small vacuoles (much smaller than plant cells).

One, large central vacuole taking up 90% of cell volume.

Shape Round Rectangular

Cell wall None Yes

TYPES OF CELLS FUNCTIONS ORGANELLES FOUND ABUNDANTLY IN THE SPECIFIC CELLS

SPERM CELLS

Require large amounts of energy to propel towards the uterus and Fallopian tube during fertilisation

Mitochondrion

FLIGHT MUSCLE CELLS IN INSECTS AND

BIRDS

Contract and relax to enable movements and flight

Mitochondrion

CELLS IN THE MERISTEMS

To enable cells in the meristem divided by mitosis process

Mitochondrion

MESOPHYLL PALISADE CELLS

Absorb sunlight during photosynthesis Chloroplasts

RELATING THE DENSITY OF CERTAIN ORGANELLES WITH THE FUNCTIONS OF SPECIFIC CELLS