2.5 Biological Membranes

Question 1

How is a concentration gradient built up?

Answer 1

Active transport moves moleculea of a substance across the partially permeable membrane against the concentration gradient. Ions diffuse back to other side but at a slower rate hence theres a concentration gradient

Question 2

Why are compartmentalised cells more efficient?

Answer 2

They are seperwted from the cytoplasm so have higher concentration of reactants and dont interfere with other metabolic processes in the cytoplasm

Question 3

Give the functions of the 4 proteins found in a plasma membrane

Answer 3

Glycoprotein
Specific receptors on cell surface used to recognise cell as self or foreign

Channel protein
Large charged proteins (such as water)
Diffusion and osmosis

Carrier proteins
Certain molecules which are actively pumped using 2k+ and 3Na+ and ATP (facilitated diffusion)

Peripheral protein
Cell signalling, can detach and reattach anywhere on membrane

Question 4

Give 3 functions of the plasma cell membrane

Answer 4

Protects cell from environment

Maintaains internal environment which is different to external

Controls what substances come in and out of the cell