Cell structure - Membrane Compartments

Question 1

What is the cell membrane composed of?

Answer 1

Lipids and proteins

Question 2

What are used as signalling molecules?

Answer 2

protein receptors

lipids as signalling molecules

Question 3

Why does compartmentalisation occur?

Answer 3

• permits specialisation

- increases surface area

Question 4

What are the two classes of transport proteins?

Answer 4

channels and transporters

Question 5

How do transporters work?

Answer 5

-undergo a conformational change that alternatively expose solute binding sites on each side of the membrane

Question 6

What factors influence transport?

Answer 6

solute concentration and charge

Question 7

What is the mechanism of glucose transport?

Answer 7

• transporter alternates between inward open and outward open states via an occluded intermediate
• binding of Na+ and glucose is co-operative
• if it opens inwards, Na+ dissociates due to the low concentration, enhancing the release of glucose

Question 8

What are the three major classes of plasma membrane receptors?

Answer 8

• those involved in rapid synaptic signalling between nerve cells and other electrically excitable cells
• indirectly regulate the activity of a separate enzyme or an ion channel
• function as enzymes or enzymes or associate directly with the enzymes they activate

Question 9

What is phosphatidyl inositol?

Answer 9

a lipid signalling molecule

Question 10

How does phosphatidyl inositol act as a lipid signalling molecule?

Answer 10

• PI can undergo rapid cycle;es of phosphorylation and dephospho rylation at the 3, 4 and 5 positions in the inositol group
• these create docking sites for proteins involved in processes such as vesicle trafficking between membrane compartments
• This recruits specific intracellular signalling proteins to the plasma membrane in response to extracellular signals

Question 11

How do lipids act as signalling molecules?

Answer 11

Act as signalling molecules themselves or generate secondary signalling molecules

eg. Phosolipase C signals and releases DAG which activates PKC

Question 12

What are raft domains?

Answer 12

Domains caused by lipid bilayers where by tight junctions can restrict membrane molecules to a particular domain

Question 13

What is the role of the cortical cytoskeleton and their filaments?

Answer 13

Gives membranes mechanical strength

Divides the membrane into smaller domains by their filaments

These domains are called corrals

Question 14

What are the 3 main classes of protein membrane receptors?

Answer 14

Ionotropic
G-protein coupled receptors
Enzyme coupled receptors