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Flashcards in Membrane Structure & Synthesis Deck (52)
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1
Q

How many membranes are there in the body?

A

Multiple different types of biological membranes with varying compositions and functions

2
Q

Which part of the phospholipid is hydrophobic?

A

The tails - composed of the fatty acid chains

3
Q

What significant structure do phospholipids form?

A

lipid Bi layers (membranes)

4
Q

What causes the asymmetry of membranes?

A

The outside of the cell has a different composition to the inside

5
Q

What are the different components of a lipid molecule?

A
  • Polar head
  • Choline, serine, ethanolamine, inositol
  • Phosphate
  • Glycerol
  • Fatty acid chains
6
Q

How can we describe the fluid nature of membranes?

A

Dynamic and flexible

7
Q

Why does a slight temperature change not alter the membrane fluidity?

A

The composition of membranes are adapted to withstand a large range of temperatures

8
Q

What is Spur Cell anemia?

A

When the plasma membranes of erythrocytes has up to 65% more cholesterol than normal

9
Q

What are the two movement types in a membrane?

A
  1. Lateral

2. Transverse

10
Q

What is apoptosis?

A

Programmed cell death

11
Q

How does a highly saturated membrane affect fluidity?

A

Molecules pack closer together
Decrease fluidity
Increase rigidity

12
Q

What facilitates the transverse movement of newly synthesised membrane?

A

ABC transport proteins (enzymes)

13
Q

Where is the new membrane formed?

A

Formed from the ER to the golgi

14
Q

What is transverse movement in the membrane?

A

Movement across the membrane (flipping to the other side)

15
Q

What is the consequence of spur cell anemia on red blood cells?

A

RBC membrane is very rigid
so rbc can no longer morph to fit through small pores (e.g. capillaries)
Less able to function as successful rbc, due to increased cholesterol levels

16
Q

What would a temperature decrease do to the fluidity of the membrane?

A

Energy associated with phospholipids decreases
Causes molecules to move closer together
Decreases membrane fluidity

17
Q

What type of movement is required in newly synthesising membrane in order to make it structurally correct?

A

Transverse movement

18
Q

List the common features of biological membranes

A
  • Asymmetrical
  • Fluid
  • Bi layers
  • Electrically polarised
  • Specific protein functions
19
Q

Why is lateral movement so rapid?

A

Due to diffusion being a passive process

20
Q

Why are phospholipids described as being amphipathic?

A

They are both hydrophilic and hydrophobic

21
Q

What are lipid anchored proteins?

A

Membrane proteins covalently linked to a lipid

e.g. glycerophosphatidylinositol

22
Q

Why does the synthesis of new membrane cause the membrane shape to be deformed?

A

Membrane is synthesised on the the cytosilic membrane only

Causes a bowed shape - deformation

23
Q

What is phosphotidylserine ?

A

A phospholipid involved in apoptosis

24
Q

How much of the % cell weight is comprised of membrane carbohydrates?

A

membrane carbohydrates form 2% of cell weight

25
Q

What factors affect the membrane fluidity?

A

Temperature
Degree of saturation
Fatty acid length
Cholesterol content

26
Q

Where are new membrane synthesising enzymes found ?

A

Cytosilic surface of golgi apparatus

27
Q

What is the purpose of apoptosis?

A

Allows body to turnover cells without inducing inflammatory response

28
Q

Which membrane movement type is faster?

A

Lateral movement

29
Q

Where are membrane carbohydrates found on the membrane?

A

Facing away from the cytosol

30
Q

Where do the hydrophilic heads on the membrane face?

A

Extracellular surface

31
Q

Where are peripheral membrane proteins found on the membrane?

A

Located on extracellular (cytosolic) side

32
Q

What components can we expect in biological membranes?

A
  • Phospholipids
  • Cholesterol
  • Glycolipids

(not all membranes contain all 3)

33
Q

What facilitates movement in the membrane?

A

Enzymes

34
Q

Describe what the structure of peripheral membrane proteins is like

A
  • non covalent bonds
  • loosely associated with membrane - easier to extract
  • lipids and proteins can bind
35
Q

How does an increase in temperature affect membrane fluidity?

A

Energy associated with phospholipids increases
Molecules able to move apart
Increases fluidity

36
Q

Give examples of some membranes present in the body

A

Nuclear membrane
Plasma membrane
Mitochondrial membrane

37
Q

Explain what is meant by lateral membrane movement

A

Along the plane of the membrane

38
Q

How do the phospholipids arrange in bi layers?

A

They readily form bi molecular sheets in aqueous media

39
Q

How is fluid is the membrane when unsaturated?

A

Molecules can’t pack as closely together due to C=C double bonds
so increases fluidity
less rigidity

40
Q

What are 3 types of ABC enzyme proteins?

A

Floppase - Moves phospholipids from cytosilic to luminal side (inner -> outer surface), using ATP

Flippase - Moves phospholipids from outer to inner leaflet, using ATP

Synthase - Bidirectional movement of phospholipids, passive

41
Q

What other molecules do membrane carbohydrates associate with?

A

Both lipids and proteins

42
Q

Describe the structural features of integral membrane proteins

A

” ɒ helical transmembrane region

  • strong non covalent bonds
  • interlinked with membrane - difficult to extract
  • Pass through membrane once or multiple times
  • Hydrophobic side chains present on outer surface
43
Q

What is the advantage of cholesterol at high temperatures in the membrane?

A

Cholesterol maintains membrane stability (decreases fluidity)

44
Q

Outline how apoptosis occurs in cells

A
  1. Phosphatidylserine transversely transported to outer surface
  2. Causes cells to round up and form nodules
  3. Cells blister and burst
45
Q

What is the role of membrane carbohydrates?

A

Allow cells to interact with each other and the extracellular membrane

46
Q

What effect does cholesterol have on the membrane?

A

OH group forms H bonds between the phospholipid hydrophobic tails
Disrupting the interactions between the fatty acid chains
Prevents strong bonding in chains
Increases fluidity - esp. at low temp

47
Q

What is the significance of ABC enzyme proteins?

A

They are crucial in establishing membrane asymmetry

48
Q

Name the different proteins present in a membrane

A

Integral membrane proteins
Peripheral membrane proteins
Lipid anchored proteins

49
Q

Why is the membrane described as fluid mosaic?

A

Fluid - components able to move around

Mosaic - composed of many different Proteins

50
Q

How is apoptosis initiated?

A

The movement of phosphotidylserine from inner to outer surface signals to cells apoptosis will occur

51
Q

What would an increase in fatty acid length do to membrane fluidity?

A

More interactions and bonds form between chains
Fluidity would decrease
Increase rigidity

52
Q

Why is transverse movement slow?

A

Relatively significant amount of energy required to move a polar molecule through a hydrophobic region to opposite side of membrane