Biology revision

Cell

a basic unit of life

Cell Wall

structure : a rigid outer layer of the cell that is made up of cellulose
function : gives the cell a fixed shape and protect it from injuries

Chloroplast

structure : oval structure
function : contains chlorophyll to trap light which is essential for photosynthesis

Cell membrane

structure : partially permeable
function : to control the movement of substances in and out of the substances

Cytoplasm

structure : a jell-like fluid where most cellular activities take place
function : contains many organelles which perform specific jobs inside the cell

Nucleus

structure : enclosed by a nuclear membrane, contains genetic information in form of chromosomes
function : control cellular activities such as growth and repair of the cell and responsible for cell division

Ribosomes

structure : small round structures which either attached to RER or move freely inside the cytoplasm
function : synthesise protein in the cell

Mitochondria

structure : small oval shaped organelle
function : where aerobic respiration occurs in the mitochondria synthesise energy

Vacuole

structure : large central, permanent in plant cell and many small, temporary in animal cell
function : store substances within the cell

Smooth endoplasmic reticulum

structure : does not have ribosomes attached to its membrane and more tubular than SER
function : to synthesise substances such as fats and steroids and converts harmful substances into harmless substances through detoxification

RER

structure : a network of flattened spaces lined with a membrane
function : to transport synthesised proteins by ribosomes to golgi body

golgi body

structure : shaped like a disc and contains a stack of flattened spaces surrounded by membrane
function : chemically modified substances made by ER, stores and packages these substances into vesicles for secretion out of the cell

How is DNA organised inside the cell ?

• A small segem