A-Level Bio A1 - Animal cell functions

Cell membrane

• formed of phospholipid bilayer

• resistant to water

• holds cell together

• selectively permeable barrier

Cytoplasm

• made up of a liquid called cytosol

• all organelles are held within it

Nucleus

• largest organelle in eukaryotic cells

• surrounded by its own membrane - nuclear envelope

• site of DNA replication

• contains nucleolus, which makes ribosomes

• DNA exists as chromatin

• controls all activities of the cell

Mitochondria

• site of aerobic respiration

• provides energy

• more active cells will have greater number of mitochondria

• inner membrane forms cristae

• ATP is produced

ER

• series of membrane folds that connect to nuclear envelope

• space between folds are fluid

• Smooth ER synthesises and processes lipids

• Rough ER is studded with ribosomes and processes proteins

Golgi apparatus

• appears as flattened sacs which produces vesicles

• all substances produced by smooth and rough ER are processed through the Golgi body

Ribosomes (80S)

• floats free in cytoplasm

• attached to ER

• site where proteins are synthesised

Lysosomes

• small round organelles

• contains digestive enzymes which needs to be separated

• digestive enzymes digest invading cells or destroy the cell

• destroying cell = apoptosis

Vesicles

• found in plant and animal cells

• made at Golgi apparatus

• found at the centre of the cell

• membrane-bound sac for transport & storage

Centrioles

• hollow fibres made of microtubules

• 2 centrioles at right angles form a centrosome

• organisms spindle fibres during cell division

• NOT found in flowering plants and fungi

Cillia

• hair-like projections made from microtubules

• allows movement of substances over cell surface