Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochemistry > Week 9 - Membrane Transport Pt II > Flashcards

Week 9 - Membrane Transport Pt II Flashcards

1
Q

What does K ion channel coming of?

A

4 subunits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does each subunit comprise of?

A

M1 and M2 helixes joined by a P (pore) segment consisting of a short helix and non helical portion that lines the channel through which ions pass

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does a portion of each P segment contain?

A

Conserved pentapeptide (GYGVT) whose residues kind the selectivity filter that screen for K+ ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does the selectivity filter contain?

A

4 rings of carbonyl O atoms and one ring of threonyl O atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why is the diameter of ring large enough?

A

8 O atoms can coordinate a single K ion, replacing it’s normal water of hydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Voltage-gated channels

A

Conformation depends on the difference in ionic charge on two sides of membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Ligand gated channels

A

Conformation depends on binding of a ligand to channel

ACH binds on outside and CAMP binds on inside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mechano-gated channels

A

Conformation depends on mechanical forces applied to membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are voltage-gated K+ channel from Eukaryotes known as?

A

Kv channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the structure of KV channel?

A

Four identical/ homologous subunit

Each subunit: 6 transmembrane alpha helices

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are 2 functionally distinct domain of KV channel?

A

Pore domain

Voltage sensing domain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is pore domain?

A

Helices S5, S6 and P segment homologous to helices M1, M2 and P segment in Kcsa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is voltage sensing domain?

A

Consist of helices S1 to S4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How many subunits do all channels have?

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Prokaryotic channel

A

4 subunits and 2 helices each=8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the role of transmembrane portion?

A

Voltage gating?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the role of cytoplasmic portion?

A

Regulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does amino acid sequence of S4 helix show?

A

A number of positively charged amino acid residues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does S4 segment show?

A

A series of positively charged amino acids (Lysine and arginine) and every 2 residues, +ve side chain going down

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Where does helix face when there’s an active membrane potential?

A

Cytoplasmic

More negative inside cell than outside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is S4 rotates?

A

Positive residues face electronegative area in cytosol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

When does helix face outside of cell?

A

Losing negative charge on inside

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is transfixed to open channel?

A

Structural change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does moving S4 helix transducer?

A

Movement of two helices (S4-S5) that forms channel for opening and closing of channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What connects the voltage sensing and pore domain?
S4-S5 linker helix
26
What is the inner surface of channel below pore domain lined by?
S6 helix
27
Resting condition, negative potential
S4 helix exposed to cytoplasm | Channel closed
28
Depolarisation
S4 helix exposed to the outside of cell | Channel open
29
Once the channel is open, how many K+ ions can pass through per second?
10 million K+ ions
30
What is the conformational states of Kv channel?
Rest Open Inactivated
31
Conformational state: rest
Membrane potential is there | Pore is closed
32
Conformational state: open
Depolarising membrane | Flux of sodium
33
Conformational change: inactivated
Milliseconds after K+ channel shut down
34
Why do we need so many voltage gated K+ channel?
Depending on the charges on the S4 helix, it will rotate channel at higher potentials/lower potentials Channel to detect subtle changes in membrane potential (differentiate to transduce lots of signals) Switched on and off through: phosphorylation, PTM etc
35
What requires a facultative transporter to cross Membranes?
Large or hydrophilic substances
36
What is facilitative diffusion?
``` Passive Specific Saturable Regulated Much slower than ion channels ```
37
Faciliative transporters can move how much solute molecules per second across the membrane?
Hundred to thousands
38
What is a gradient favouring the continued diffusion of glucose into the cell maintained by?
Phosphorylating the sugar after it enters the cytoplasm | Lowers the intracellular glucose concentration
39
Transport
1. Glucose binds to transporter 2. Transporter changes shape 3. After binding, active site now exposed to cytosolic side 4. Transport
40
Recovery
Active site closed to cytosol
41
How many glucose transporters in human body?
5
42
Which glucose transporter is most important?
GLUT 4
43
Why is hexokinase phosphorylation?
Concentration gradient to drive glucose in
44
What happens when you eat a lot of sugar?
Pancreas produces insulin
45
Vesicles full of GLUT4 transporters on surface of cells
Vesicular fusion | Glucose import from bloodstream to cells (skeletal muscle and adipocytes)
46
Where are transporters present?
Membrane of cytoplasmic vesicles
47
What is nitrate central in?
Nitrogen metabolism
48
How is nitrite rapidly removed from the cell?
Channels | Transporters
49
What do assimilatory enzymes do?
Reduce nitrite to ammonium it dinitrogen
50
What is the structure of Nark?
Positively charged substrate-translocation pathway lacking protonable residues
51
What does Nark function as?
Nitrate/nitrite exchanger | Protons are unlikely to be co-transported
52
How does Nark exchange nitrate for nitrite by?
Rocker switch mechanism | Facilitated by: inter-domain hydrogen bond networks
53
Active Transport
Energetically unfavourable so needs to be coupled to a favourable reaction
54
What does active transport do?
``` Maintain gradients for: Potassium Sodium Calcium Other ions across cell membrane ```
55
Active transport
Couples the movement of substances against gradients to ATP hydrolysis
56
What is the ratio of Na+ : K+ pumped?
3:2 | The Na+/K+ ATPase is electrogenic
57
What is ATPase?
P-type pump | Phosphorylation causes change in structure and affinity that allow transport against gradients
58
Where is Na+/K+ ATPase found only in?
Animals
59
What does hydrolysing ATP give?
Structural change in ATPase protein
60
Define electrogenic?
Producing a change in the electrical potential of a cell
61
What does Na+/K+ ATPase have high affinity for?
Na+ in the cytoplasm | K+ in the extracellular space
62
What does Na+/K+ ATPase have lower affinity for?
Na+ in the extracellular space | K+ in the cytoplasm
63
E1 —> E2
Phosphorylated and release ADP
64
E2 —> E1
Dephosphorylated and binds ATP
65
Where does sodium ions bind protein?
Inside of membrane
66
When ATP is hydrolysed andphosphate transferred to protein what does it allow?
Sodium ions to be expelled to external space
67
What happens to the phosphate group when potassium ions bind to the protein
Subsequently lost
68
Where is cation binding site located?
Deep within transmembrane domain | Consist of 10 membrane spanning helices
69
What does V-type pump actively transport?
Hydrogen ions across the walls of cytoplasmic organelles and vacuoles
70
Where does V type pump occur?
Membrane that line: Lysosomes Secretory granule Plant cell vacoules
71
V type pump in the plasma membrane of kidney tubules
Maintain body’s acid-base balance by secreting protons into forming urine
72
What is active transport coupled to?
Existing ion gradient
73
What is symport?
Pump gradient up on inside Move sodium with other compounds to create smaller gradients of other molecules The molecules will travel in same direction in relation to each other
74
What is antiport?
Integral membrane transport protein that simultaneously transport two different molecules in opposite directions
75
Sodium glucose transporter
High sodium concentration outside | Low concentration of glucose
76
What is secondary transport?
The use of energy stored in an ionic gradient

Biochemistry (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions