Facilitative and Secondary Active transport Links to Glucose Homeostasis Flashcards Preview

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Flashcards in Facilitative and Secondary Active transport Links to Glucose Homeostasis Deck (65)
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1
Q

Name the 2 different ways to achieve diffusion?

A

Bilayer or channel

2
Q

Define “primary active transport”?

A

Use of ATP to transport a solute against its concentration gradient.

3
Q

Define “secondary active transport”?

A

Symport. Use of the energy retrieved from a solute going with its concentration gradient as the energy source for a solute going against its.

4
Q

Define “symport”?

A

The solutes are going in the same direction

5
Q

Define “antiport”?

A

The solutes are getting transported in different directions

6
Q

Why is glucose oxidation important?

A

Represents a major source of energy in mammalian cells.

7
Q

Why is it important for the glucose oxidation to get into the cells?

A

In order to utilise the energy from it

8
Q

Name the two different classes of glucose carriers that is important in transferring glucose across the plasma membrane?

A
  1. Sodium-coupled glucose transporters 2. Facilitative glucose transporters
9
Q

Where is the sodium- dependent glucose cotransporter expressed?

A

In absorptive/reabsorptive epithelia such as intestine and kidney.

10
Q

Define the characteristics of the sodium-coupled glucose transporters?

A

Glucose transport occurs actively against its concentration gradient by coupling glucose uptake with that of sodium.

11
Q

Why do cells need energy?

A

In order to maintain basic function.

12
Q

Give an example of a primary active transporter that brings in glucose into the cell?

A

GLUT

13
Q

Give an example of a secondary active transporter that brings in glucose into the cell?

A

SGLT. (sodium-glucose linked transporter) Brings in sodium and glucose.

14
Q

The important of the sodium-potassium pump when thinking of glucose homeostasis?

A

It actively removes sodium from the cell (therefore making the concentration of sodium low in the cell). This is important as the SGLT brings it in.

15
Q

Define “stoichiometry”?

A

Sodium coupling ratio. eg. 2 Na: 1 Glucose for SGLT

16
Q

Give an example of a tertiary active transporter that brings glucose into the cell?

A

Proton coupled active transporter (H+)

17
Q

What is the equilibrium ratio for co-transported solute?

A

[S]I/[S]O = ([Na]O/[Na]i) ^n . (e^-FE/RT)^n*. =Chemical gradient x electrical gradient

18
Q

What does the “n” stand for in the equilibrium ratio for co-transported solute?

A

Coupling ratio

19
Q

What does the “ * “ stand for in the equilibrium ratio for co-transported solute?

A

Charge of the ion. ie. Na^2+ : therefore *= 2

20
Q

What is the names given to the two members of the SGLT family?

A
  1. SGLT1 2. SGLT2
21
Q

SGLT1 characteristics?

A

High affinity. 2 sodium: 1 glucose. seen in the intestines

22
Q

SGLT2 characteristics?

A

Low affinity. 1 sodium: 1 glucose. Seen in the kidneys

23
Q

Name the three types of secondary active transporters: symporters?

A
  1. SGLT family 2. Ion coupled transporters of amino acids 3. NKCC
24
Q

How many common amino acids are there that can be used in the ion-coupled transporters of AA?

A

20 AAs

25
Q

What are the three variables that determine the amino acids transporter that is selected for a specific amino acid substrate?

A
  1. Charge 2. Size 3. Structure
26
Q

Define the “GAT family”?

A

Family of sodium chloride coupled transporters

27
Q

Name the two groups of member in the GAT family?

A
  1. GAT 1-3 (for GABA) 2. GLY1-2 (for glycine)
28
Q

What is the role of the GAT family?

A

Roles in inhibitory neurotransmission

29
Q

Define “hetero-exchange”?

A

Its when two different solutes are coupled in the active transport

30
Q

Define “tertiary active transporter”

A

Use of the energy retrieved by secondary transport as the source of energy to transport new solutes.

31
Q

Name the primary, secondary and tertiary active transport used to transport amino acids (Gln, Leu)?

A

Primary: Sodium pump Secondary: System A Tertiary: System L

32
Q

NKCC cotransporters properties?

A

1 Na: 1 K: 2 Cl: all solutes come into the cell-> water removed Inhibition by bumetanide > piretanide > furosemide: promotes water loss from the body.

33
Q

NKCC cotransporter functions?

A

Cotransport in epithelial NaCl absorption Promotes water loss from cell Cell volume regulation Modulation of neurotransmission

34
Q

Name the two types of secondary active transporters: anti porters?

A
  1. Na/H exchangers (NHE1-5) 2. Na/Ca exchange (NCX1)
35
Q

What are the 3 functions of the Na/H exchangers?

A
  1. Epithelial absorption and secretion 2. Cell volume regulation 3. pH regulation
36
Q

How many members are in the Na/H exchanger family?

A

NHE 1->5

37
Q

What does each member do as a function?

A

NHE 2->4 : Epithelial absorption and secretion NHE1: Cell volume regulation NHE 1,5: pH regulation

38
Q

How does the Na/H exchanger regulate pH? Additionally what pH?

A

The activity reacts to low pH levels. ie. if there is a lot of acidic inside the cell there is a need to remove it therefore the activity increases.

39
Q

What is use to regulate high pH?

A

Cl/HCO3 antiporter. Activity increases at high pH to reduce the pH to normal. Works beside Na/H exchanger.

40
Q

What modulates the NHE1 activity?

A

By phosphorylation.

41
Q

How does the NHE 1 function as a cell volume regulator?

A

The ubiquitous NHE1 translocates ions that change the pH and cell volume- regulating cell proliferation and migration.

42
Q

How does the NHE1 help in cytoskeletal assembly and cell shape determination?

A

NHE1 binds directly to ERM proteins and acts as a membrane anchor which is critical for these assemblies.

43
Q

Name the 3 properties of the sodium/ calcium exchanger?

A
  1. Na inwards/ Ca outwards usual, notably in cardiac muscle. 2. Contributes to keeping cell calcium conc low. 3. 3 Na: 1 Ca
44
Q

Ouabain use during a heart failure?

A

Reduces calcium gradient. Cell calcium increases due to reduced NXC1 activity. Increases contractile force.

45
Q

How many transmembrane domains are there in the SGLT?

A

13 transmembrane domains

46
Q

Where abouts in the body is SGLT1 found?

A

In the intestines.

47
Q

Where in the body is SGLT2 found?

A

In the kidneys

48
Q

Describe how the SGL transporter actually works?

A

See AS2

49
Q

Describe the 5 properties of the facilitative glucose transporters?

A
  1. Integral membrane proteins. 2. Present on the surface of all cell membranes. 3. Transport glucose down a concentration gradient. 4. Energy independent. 5. Can operate bi-directionally
50
Q

How does GLUT1 work?

A

51
Q

Name the 3 properties of the facilitative GLUT family?

A
  1. 13 functional facilitated hexose carriers 2. Saturable, stereoselective 3. 12 Transmembrane domains.
52
Q

What part of the facilitative GLUT is important for different antibodies to bind?

A

Unique last 20 AAs which determine what antibodies binds.

53
Q

How many classes of GLUTs are there?

A
  1. Class 1, 2 and 3
54
Q

Define the properties of Class 1 GLUT and the different members in it?

A

Comprises the well-characterised glucose transporters. High affinity: GLUT 1, 3, 4 Low affinity: GLUT 2

55
Q

Define the properties of Class 2 GLUT and the different members in it?

A

Very low affinity for glucose (transport fructose). GLUT 5, 7, 9, 11. HMIT1

56
Q

Define the properties of Class 3 GLUT and the different members in it?

A

GLUT 6, 8, 10, 12

57
Q

Characteristics of GLUT 1?

A

House keeping sugar transporter. Widely expressed.

58
Q

Characteristics of GLUT 2?

A

Low affinity glucose transporter. Will never be saturated. Role in sensing glucose concentrations in islets.

59
Q

Characteristics of GLUT 3?

A

Important in the foetus. High affinity. Ensures the foetus has enough glucose. Important in the brain also as the brain can metabolise fatty acids therefore needs glucose.

60
Q

Characteristics of GLUT 4?

A

Important in insulin targeting tissues ie. skeletal, cardiac muscle and adipose tissue.

61
Q

What are the Km values for each of the GLUTS?

A

62
Q

How does GLUT2 affect the islets in the pancreas?

A

When there is a high level of glucose outside the GLUT2 brings in glucose. Undergoes glycolysis producing ATP. This opens the ATP sensitive K channel causing a depolarisation inside the cell. In turn, opening the calcium channel (sensitive to voltage). This increase in calcium stimulates exocytosis of the vesicles containing insulin.

63
Q

What is the GLUT4 responsible for?

A

Mediating insulin-sensitive glucose transport Important for facilitating peripheral glucose disposal after a meal when blood glucose is high

64
Q

What does cytochalasin B do?

A

Specifically binds to facilitative glucose transporters in a non-competitive manner. Inhibits cell division

65
Q

GLUT 4 expression after a meal?

A

Insulin is produced straight after a meal. Stimulates the movement of GLUT4 from the inner membrane to the plasma membrane and therefore facilitative transport of glucose into the cell. Found in fat cell as well as muscle.