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Biochemistry 2 > Lipid membrane and solute transport > Flashcards

Lipid membrane and solute transport Flashcards

1
Q

Why the membrane is called mosaic?

A

Because it consists of different kinds of molecules

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2
Q

The integral proteins are called like that because

A

They are embedded in the membrane. They can pass through the lipid bilayer or only on one side

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3
Q

Example of integral proteins

A

Receptors ( GPCRs)

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4
Q

Why do detergents are needed to detach the integral proteins form the membrane?

A

Because they are strongly associated with it

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5
Q

What does amphitropic protein mean

A

Having an affinity for both lipid and aqueous environments. Thus, if needed they can detach from the membrane and play its role in the aqueous environment

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6
Q

What do you need to make amphitropic proteins detach from the membrane?

A

Some kind of enzyme ( phospholipase C) or postranslational modification (phosphorylation)

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7
Q

What is GPI?

A

Glycosylphosphatidyllinositol

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8
Q

An example of GPI linked protein

A

Phosphatases

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9
Q

Different organelles within the cell have different ____

A

Cell wall components ( the ratio of components)

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10
Q

Inner and outer cell membrane ___ each other

A

Differ from each other

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11
Q

What molecules are involved in cell signaling in the cell membrane

A

phosphatidyllinositol

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12
Q

Most of phosphatidyllinositol is inside/outside of the cell

A

inside

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13
Q

Phosphatidylserine is usually maintained

A

Inside of the cell

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14
Q

When Phosphatidylserine flips to the outer membrane, then

A

It signals for apoptosis or blood clot

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15
Q

Acyl groups in the bilayer affect

A

Flexibility

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16
Q

There are two states of the bilayer

A

Ordered state(Lo) and disordered state(Ld). It is a range of temperatures rather than points

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17
Q

The transition from Lo->Ld of side chains is a result of

A

Heat that produces thermal motion in side chains. The more temperature it is exposed to, the more disordered the side chains will be.

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18
Q

What increases order in the bilayer

A

Saturation of FA
Uniform length of FA
Sterol content can decrease or increase order

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19
Q

How do cells regulate the membrane

A

FA content ( increase Saturated FA at higher temperatures)

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20
Q

Ordered state is more ___, and disordered is more ___

A

Rigid

Flexible

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21
Q

uncatalyzed lipid movement ( what direction)

A

Lateral diffusion

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22
Q

three catalyzed transbilayer translocation

A

flippase (from outer to inside)
Floppase ( form inside to outside)
Scramblase ( moves lipids in either direction, toward equilibrium)

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23
Q

what enzymes perform flippase and floppase

A

Flippase- P-type ATPase
Floppase- ABC transporter
With the use of ATP

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24
Q

What holds protein in the bilayer

A

Cytoskeleton

Lipid rafts

25
Q

Sphingolipids give __ to the bilayer

A

Order, thus more rigid.

Sphingolipids give order to an area, not flexible within the region, but as a whole free to move

26
Q

Lipid rafts contain specific___

A

Double or triply acylated proteins

27
Q

6 things for two membranes to fuse

A
  • triggering signal
  • recognize each other
  • close apposition
  • local disruption of bilayer
  • hemifusion
  • fusion proteins
28
Q

All neurotransmitters are stored in ___

A

Vesicles

29
Q

Four types of proteins that are involves in fusion at synapse

A

T-SNARE
V-SNARE
Q-SNARE(SNAP-25)
NSF (N-ethylmaleimide-sensitive fusion factor)

30
Q

What does T-SNARE do

A

They are assembled on the target membrane. At this pont of time the cell should know at what part of the exon( because it is huge) it will secret the neurotransmitters. This is done by them

31
Q

What does V-SNARE do

A

It recognizes the vesicle that should be emptied out. It is assembled on the vesicle site

32
Q

What do Q-SNARE do

A

They help T-SNARE and V-SNARE to come together

They are induced by Ca

33
Q

The stages in fusion of the vesicle with neurotransmitter

A

1) The vesicle has V-SNARE and the plasma membrane has T-SNARE. SNAP-25 helps this two to come together
2) V and T bind to each other and start to zip, thus they are brought closer to each other
3) When the vesicles are brought close enough to each other, hemifusion occurs between outer leaflets
4) Hemifusion-> full fusion. Now the vesicle can open up, because it is part of the membrane

34
Q

What does NSF do

A

They disassemble the proteins that were bound to each other, the SNARE complex

35
Q

Three glucose transporters that are studied a lot

A

Glut 1
Glut 2
Glut 4

36
Q

Glut 1,2 and 4 belong to what kind of transporters

A

Passive, do not need energy, down the concentration gradient

37
Q

Glut 4 is regulated by what mechanism

A

RTK and PIP3 and PKB

38
Q

How GLUT 4 is regulated

A

Amount of transporter presented in the cell membrane by RTK
thus regulating how much glucose is available for glucose transport. The more transporters are available, the more glucose goes from outside to inside. If no RTK signal, transporters are stored in the cell in vesicles

39
Q

What is diabetes mellitus ( biochemically)

A

Lack of signal transduction of RTK, thus less transporters come form the inside to the outside-> less glucose uptake

40
Q

Respiration is what kind of transport

A

Facilitated passive transport

41
Q

Explain what happen in erythrocyte when it comes to respiring tissue

A

CO2 diffuses through the membrane inside the erythrocyte. CO2+H2O->HCO3-+H+
HCO3- is thrown outside the membrane and CL- is taken in by a cotransporter(antiporter)

42
Q

What is the enzyme for conversion of CO2 to HCO3-

A

carbonic anhydrase

43
Q

What happens in lungs

A

The same reaction as in erythrocyte but in reverse.

Cl- is given off, HCO3- is taken, converted to CO2 and given to lungs

44
Q

Two types of active transporters

A

Primary active transport

Secondary active transport

45
Q

Explain the difference between primary active transport and secondary active transport

A

Primary- with the use of ATP, the molecule is transported across the concentration gradient
Secondary- an artificial gradient of one molecule is created by pumping it across the gradient, to allow another protein to use this gradient to transport another molecule symporter)

46
Q

An active transport: symport example and antiport example

A

Symport: Na+ glucose, Na+ AA in intestinal epithelium
Antiport:Na+K+ATPase,Na+H= pumps in kidney

47
Q

What type of ATPases in used in mitochondria

A

F type

48
Q

Explain ABC transporters

A

When ATP is boiund to the cassette, the transporter is opened outward, when ADP- inward, when the molecule comes there is a change in conformation, because of ATP\ADP

49
Q

RBCs comparing to the stem cell does not have

A

Nucleus and mitochondria

50
Q

As RBCs do not have mitochondria what does it mean for them

A

They cannot produce energy and they rely only on glycolysis

51
Q

Tissue repair requires____

A

Energy and biosynthesis precursors

52
Q

Neurons depend more on ___

A

Glucose

53
Q

Cardiac myocytes (muscles int he heart) depend more on ___

A

FAs

54
Q

Where can the regulation be inserted in the cell

A
  1. Extracellular signals
  2. Transcription regulation (a-TF phosphorylation/dephosphorylation,b-TF interactions)
  3. mRNA stability (degradation)
    - miRNA)
  4. mRNA translation
  5. Protein half-life (stability)
  6. Enzyme localization
  7. Changes of levels of substrate( the more substrate- the more active the enzyme)
  8. Enzyme binding “allosteric effectors”
  9. Covalent modification
  10. Interaction with regulatory protein
55
Q

The longer mRNA is maintained within the cell- the longer it is going to be ___

A

Translated, the more protein produced

56
Q

What are cyclins

A

Proteins involved in cell cycle- cell division, their half-life is very short

57
Q

Mitochondrial enzymes are only functional

A

In mitochondria

58
Q

Pathways in opposite directions are not favored ___. For example

A

At the same time

Glycolysis and Gluconeogenesis

Biochemistry 2 (17 decks)

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