Membrane Structure And Func 2

Question 1

What is membrane funtion dependent on?

Answer 1

Structure

Question 2

What are the functions of a membrane?

Answer 2

Transport - Diffusion and Active
Intracellular compartmentalisation
Cell-cell recognition

Question 3

Major func of plasma membrane?

Answer 3

Barrier
Transport
Signal transduction

Question 4

Major func of inner mitochondrial membrane?

Answer 4

Energy transduction

Question 5

Major func of outer mitochondrial membrane?

Answer 5

Barrier

Question 6

Func of memb of rER?

Answer 6

Translation protein processing

Question 7

Func of memb or sER?

Answer 7

Synthesis of complex lipids

Question 8

Golgi membrane function?

Answer 8

Post translational modification, processing for secretion

Question 9

Nuclear membrane func?

Answer 9

Attachment of chromatin

Question 10

Lysosome membrane function?

Answer 10

Hydrolytic enzymes

Question 11

Peroxisome membrane function?

Answer 11

Fatty acid oxidation

Question 12

Explain the chemical composition of membranes? give some examples

Answer 12

Usually roughly 50% protein and 50% lipid, with a small part of carbohydrate (eg below 10%) like erythrocyte plasma membrane and hepatocyte plasma membrane

• Exceptions are the myelin - 18% protein, 79% lipid and 3% carb
• Inner mitochondrial membrane - 75% protein, 23% lipid and 2% carbohydrate

Question 13

Explain simple diffusion.

Answer 13

Lipid soluble molecules can move either way through the membrane. Movement of these molecules is dependent on their concentration.

Question 14

Is passive transport carrier mediated or non mediated?

Answer 14

can be both - A can diffuse on its own, or can use a carrier or channel protein.

Question 15

Is active transport carrier mediated or non mediated?

Answer 15

It is carrier mediated, uses carrier proteins

Question 16

Membrane co-transport - what is a symporter?

Answer 16

An integral membrane protein that is involved in the transport of many differing types of molecule across the plasma membrane.

Question 17

Antiporter?

Answer 17

Also called exchanger or counter-transporter, its a co-transporter and integral membrane protein that is involved in the secondary active transport of two or more different molecules or ions across a phospholipid bilayer such as the plasma membrane in two different directions.

Question 18

When is diffusion faster?

Answer 18

When it is carrier mediated.

Question 19

Glucose transport is…

Answer 19

Carrier Mediated

Question 20

What glucose transporter is located in all mammalian tissues, what is the Kt and function?

Answer 20

GLUT1 and GLUT3
Kt is 1mM
for basal glucose uptake

Question 21

Which glucose transporter is in the liver and pancreatic beta cells? Kt? and function

Answer 21

GLUT2
Kt is 15-20mM
In the pancreas plays a role in the regulation of insulin
In the liver, removes excess glucose from the blood

Question 22

Glucose transporter in the muscle and fat cells, Kt and function?

Answer 22

GLUT4,
Kt is 5mM
Amount in muscle plasma increases with endurance training

Question 23

Glucose transporter in the small intestine, Kt and function?

Answer 23

Primarily a fructose transporter

Question 24

Explain the membrane transport of glucose 6 phosphate

Answer 24

-Conformational changes result in transport
-Driven by concentration gradient
-Bidirectional
Gradient maintained by phosphorylation.

Question 25

Kinetics of glucose transport is similar to…

Answer 25

Enzyme kinetics. Exhibit saturation type kinetics, they can be regulated

Question 26

How can glucose uptake be increased?

Answer 26

By increasing the number of transporters, eg GLUT 4 - adipocytes and skeletal muscles, stimulated by insulin.

Question 27

Discuss the active transport of Sodium ions.

Answer 27

• Conc of Na ions outside the cell is 143mM
• Concentration inside the cell is 14mM
• But there is no free movement, as active transport is selective and requires an integral membrane protein.
• Na electrochemical gradient requires energy in the form of ATP to be established

Question 28

Foxglove - explain the Digitalis Cardiotonic steroid.

Answer 28

Inhibits the sodium potassium pump, thus causing the sodium potassium pump to be affected. The calcium ion concentration increases, and this increases the strength of contraction.

Question 29

Sodium dependent glucose transporters?

Answer 29

SGLUT-1 and 2

• Na and glucose symporter
• or sodium potassium pump

Question 30

What does re-hydration therapy do?

Answer 30

Targets the co-transport of glucose and sodium

Question 31

Which transport protein is associated with cystic fibrosis?

Answer 31

The cystic fibrosis trans membrane conductance regulator. Chloride ions, osmosis, abnormally thick mucus. 1 in 20 Caucasians are carriers of a single deletion at position 508. Individuals that carry the deletion in both copies of the gene produce a protein that fails to insert into the membrane.

Question 32

What is compartmentalization?

Answer 32

It separates reactions, enabling the local environment to be regulated (eg. pH). It brings reactants together

Question 33

How do proteins get to the correct compartment? An example?

Answer 33

They have signal sequences that target them to specific organelles. Mannose 6-phosphate targets enzymes made in the golgi to the lysosome, during I cell disease.

Question 34

What is involved in cell recognition?

Answer 34

Membrane Carbohydrates. Like blood antigens are recognised by glycolipids, lyphocyte traffiking selectins are detected by glycol-proteins.