biological membranes

Question 1

Explain how cell surface membranes contribute to the process of cell signalling (4)

Answer 1

release of signal molecule by, exocytosis / secretion
proteins / glycoproteins / glycolipids, act as / have, receptors
idea that: receptor / signal, is specific ;
idea that: shape of receptor and signal are complementary ;
idea that: attachment of signal molecule causes change
(inside cell / on cell surface) ;
cell surface membrane allows entry of some signal molecules

Question 2

Cells contain a large number of membrane-bound vesicles. Many of these vesicles transport substances between organelles.

(i) Outline how the vesicles are moved from one organelle to another.

Answer 2

cytoskeleton / microtubule / microfilament ;
provide, pathways / tracks, (for movement) ;
(vesicle) moves along, microfilaments / microtubule ;
microtubules, extended / broken down ;
uses, ATP / (metabolic) energy ;

Question 3

Explain why plant cells do not burst when they are left in pure water (2)

Answer 3

cell wall ;
provides strength / withstands (internal) pressure /
prevents cell membrane over expanding /
exerts pressure potential

strong cell wall = 2 marks