Structure

Function

1. Plasma membrane

Protects; prevents entry of harmful substances, holds cell together; transport of metabolites, cell to cell recognition and communication; involved in immune responses hormonal action and conduction of action potentials

2. Cytoplasmic organelles

a) Endoplasmic reticulum (ER)

Rough ER, protein synthesis smooth ER, steroid and lipid synthesis

b) Ribosomes

Terminal stages of protein synthesis

c) Golgi complex or apparatus

Stores, modifies and packages secretions; manufactures polysaccharides

d) Mitochondria

'Powerhouse of the cell, terminal stages of aerobic respiration, synthesis ATP

e) Pinocytotic vesicles

Uptake of dissolved materials

f) Lysosomes

"Disposal units, contain hydrolytic enzymes which digest materials; intracellular breakdown (autolysis)

g) Centrioles

During cell division they separate and move to from the poles of the nuclear spindle

h) Microtubules

Movement and support, e.g. beating of sperm tailor cilia; movement of chromosomes in cell division.

i) Microfilaments

Movement and support e.g. general floating motion of cytoplasm (cytoplasmic streaming), contraction of muscle fibres, microvilli

3. Nucleus

a) Nuclear membrane

Pores serve as transport channels

b) Nucleoli

Site of synthesis of RNA and DNA

c) Chromosomal material

(chromatin)

The information required to synthesise proteins is coded in the DNA. The DNA is copied into "messenger" RNA molecules. These pass into the cytoplasm where the protein synthesis takes place