Membrane structure and function II

Question 1

What way can lipid soluble molecules move?

Answer 1

Lipid soluble molecule can move either way through the membrane

Question 2

What is the movement of lipid soluble molecules dependant on?

Answer 2

Movement of these molecules is dependant on their concentration

Question 3

What is passive diffusion driven by?

Answer 3

Driven by concentration gradient

Question 4

What is active transport driven by?

Answer 4

Driven by hydrolysis of ATP

Question 5

What is an antiporter?

Answer 5

Antiporter transport 2 molecules in opposite direction

Question 6

What is a symporter?

Answer 6

Symporter transport 2 molecules in the same direction

Question 7

Passive transport with and without a carrier

Answer 7

Passive transport without a carrier is much slower compared to transport with a carrier.

Question 8

What do different tissues have?

Answer 8

Different tissues have different glucose transporters

Question 9

How are glucose transporters mediated?

Answer 9

Carrier mediated

Question 10

What direction is glucose movement?

Answer 10

Bi-directional

Question 11

How is glucose transported?

Answer 11

1. Conformational change in the carrier protein shape resulting in transportation
2. Glucose can now fit in the binding site
3. Carrier protein changes shape again and this causes the release of glucose through the other side of the membrane
4. Glucose is phosphorylated to maintain the glucose concentration gradient
   a. This allows the cell to take in glucose continuously

Question 12

Why is glucose phosphorylated and what is formed?

Answer 12

Glucose is phosphorylated to form G6P because there are more G6P transport proteins

Question 13

What is Kt?

Answer 13

Kt is the measure of affinity of the transporter of the substrate

Question 14

What does a low Kt mean?

Answer 14

It means a high affinity

Question 15

Where is Glut 4L primarily found?

Answer 15

Primarily found in adipocytes and skeletal muscles

Question 16

What are Glut 4L stimulated by?

Answer 16

Stimulated by insulin

Question 17

What do cells usually have a reserve of?

Answer 17

Have a reserve of transporters

Question 18

How can glucose uptake be increased?

Answer 18

Increased by increasing the number of transporters

Question 19

What does active transport require?

Answer 19

Requires an integral membrane protein

Question 20

How is the concentration gradient of an ion maintained in active transport?

Answer 20

Ion concentration gradient maintained by ATP

Question 21

What is foxglove used to treat?

Answer 21

Used to treat dropsy(Congested heart disease)

Question 22

What is the active ingredient in foxglove?

Answer 22

Active ingredient is digitalis(Cardiotonic steroid)

Question 23

What does digitalis do?

Answer 23

Inhibits the Na+/K+ ATPase pump

Question 24

Why is intracellular Na+ required?

Answer 24

Intracellular Na+ is required for correct regulation of the contraction of the heart

Question 25

What does Ca2+ determine in the heart?

Answer 25

Ca2+ determine the strength of the contraction of the heart

Question 26

What are SGLT-1 and 2?

Answer 26

They’re both glucose transporters

Question 27

What gene is SGLT-1 and 2 members of?

Answer 27

Members of the SLC5A gene

Question 28

What do the SGLT-1 and 2 use energy from?

Answer 28

Use energy from the Na+ gradient created by the ATPase pump to transport glucose across apical membrane

Question 29

What is used to treat type 2 diabetes?

Answer 29

SGLT2 inhibitors, like glifiozins

Question 30

What ingredients does oral rehydration therapy contain?

Answer 30

8 teaspoons of sugar, 1 teaspoon of salt and 1 litre of water

Question 31

What is oral rehydration therapy used for?

Answer 31

Oral rehydration contains both sodium and glucose

Used to treat severe dehydration

Question 32

How does oral rehydration therapy work?

Answer 32

• SGLT1 transports glucose and sodium across the cell membrane
• Hundreds of water molecules move into epithelial cell for each cycle of transport
• This can achieve rehydration

Question 33

What do membranes act?

Answer 33

Act as partially permeable membranes

Question 34

What is ATP production dependant on?

Answer 34

ATP production is dependant on the properties of membranes

Question 35

What is cystic fibrosis a disease of?

Answer 35

Cystic fibrosis is a disease of transport across membranes

Question 36

What does compartmentalisation do?

Answer 36

Separates reactions

Question 37

What does compartmentalisation enable?

Answer 37

Enables the local environment to be regulated for instance, pH

Question 38

What does compartmentalisation bring together?

Answer 38

Brings reactants together

Question 39

What do proteins have which target them?

Answer 39

Proteins have particular signal sequences which target them to specific organelles

Question 40

Where is Lysosomal hydrolase synthesised and transported?

Answer 40

Lysosomal hydrolase is synthesised in the ER and transported to Golgi where mannose is added forming Mannose 6 phosphate

Question 41

What does mannose do to the protein?

Answer 41

Mannose directs the protein to the lysosomes

Question 42

What does M6P do to its receptor?

Answer 42

Mannose 6 phosphate binds to its receptor

Question 43

What happens once protein reaches the lysosome?

Answer 43

Reaches lysosome where it fuses and hydrolyses

Question 44

What is I cell disease caused by?

Answer 44

Caused by the deficiency of GIcNAc phosphotransferase which phosphorylates mannose residues

Question 45

What does is mean when there is a deficiency of GIcNAc phosphotransferase?

Answer 45

This means proteins cannot be marked and are excreted out the cell

Question 46

What does this eventually lead to?

Answer 46

Lysosomes unable to function and results in a build up of substances within the lysosome which it’s unable to degrade.