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ICPP > Lecture 1 - Membrane Bilayer Structure > Flashcards

Lecture 1 - Membrane Bilayer Structure Flashcards

1
Q

What are the major functions of biological membranes?

A

Highly selective permeable barrier
Controls enclosed electrochemical environment
COMMUNICATION
Generating signals in response to stimuli

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2
Q

How are membranes involved in communication?

A

Recognition
Signalling
Adhesion proteins
Immune surveillance

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3
Q

How would you describe the structure of a cell membrane generally?

A

A dynamic fluid phospholipid bilayer with proteins and additional structures

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4
Q

What is meant by membranes being heterogenous within and between cells?

A

The structure and therefore undying function of membranes are different based on the cells/organelles function

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5
Q

What types of molecules are cell membranes made up of?

A

Lipids
Proteins
Carbohydrates

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6
Q

What is a major component of the cell membrane?

A

Water
Membranes are hydrated structures

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7
Q

What is the role of water in hydrating membranes?

A

It interacts with the charged/polar regions
This stabilises the lipid head regions of the bilayer

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8
Q

What are the 3 types of lipids that can compromise cell membranes?

A

Phospholipids
Glycolipids
Cholesterol

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9
Q

What is the difference between saturated and unsaturated phospholipids making up the cell membrane?

A

Saturated have single C-C bonds in the fatty acid chains

Unsaturated have some C=C bonds in the fatty acid chains

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10
Q

What are the 2 structural forms of unsaturated phospholipids?

A

Cis
Trans

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11
Q

What is the structure of a Cis phospholipid?

A

One of the fatty acid chains is kinked at the point of the double bond

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12
Q

Which is the structure of a trans phospholipid?

A

Double C=C bond where the fatty acid chains are straight

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13
Q

What is the name of a type of glycolipid?

A

Ganglioside

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14
Q

What does Amphipathic mean?

A

One part of the molecule is hydrophilic
One part of the molecule is hydrophobic

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15
Q

What is amphipathic about the cell membrane?

A

The polar (hydrophilic) heads
The non polar (hydrophobic) fatty acid chains of the bilayer

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16
Q

What is a Micelle?

A

3D sphere of phospholipids

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17
Q

What is the main type of phospholipid that makes up the cell membrane?

A

Glycerophospholipids

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18
Q

What is the structure of a Glycerophospholipid?

A

Polar phosphate group = hydrophilic head

Glycerol backbone

Fatty acid chains (hydrophobic tail)

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19
Q

What property of glycerol in a phospholipid allows the polar phosphate head and hydrophobic fatty acid tails to swivel?

A

The single bonds in glycerol

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20
Q

What is esterification?

A

An acid group being added to an alcohol group

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21
Q

Which group of fatty acid chains can interact with water?

A

-C=O (acyl group)

22
Q

What are 2 common polar head groups that can be found attached to the phosphate group?

A

Choline
Inositol

23
Q

What type of molecule is sphingomyelin?

A

Phospholipid

24
Q

What is different between a sphingomyelin molecule and a glycerophospholipid?

A

Sphingomyelin does not have a glycerol backbone, it has a Sphingosine molecule instead

25
Q

What process does sphingomyelin have a key role in?

A

Lipid raft formation

26
Q

What are the 2 types of glycolipids?

A

Cerebrosides
Gangliosides

27
Q

What is special about glycolipids structurally?

A

No glycerol backbone (sphingosine)
No phosphate group

28
Q

Where are cerebrosides and gangliosides mainly found?

A

CNS/PNS

29
Q

On the membrane, where are sphingomyelin and glycolipids found?

A

On the outer face of the membrane

30
Q

What is the structure/properties of cholesterol?

A

Amphipathic
Hydrophilic -OH head
Hydrophobic 4 planar carbon rings and short fatty acid tail

31
Q

What is the key membrane function of cholesterol?

A

Regulates membrane fluidity and stability by enhancing/extending temerature range that the membrane is thermodynamically stable

Lipid raft formation

31
Q

What is the key membrane function of cholesterol?

A

Regulates membrane fluidity and stability by enhancing/extending temerature range that the membrane is thermodynamically stable

Lipid raft formation

32
Q

What is membrane fluidity?

A

The property of the cell membrane that allows it to adapt its shape and movement to different conditions

33
Q

What happens when the cell membrane is too fluid?

A

There is a loss of molecular organisation needed for membrane/protein function

34
Q

What happens when the membrane is not fluid enough and is gel like?

A

It restricts and constrains the mobility of proteins and restricts the ability for diffusion to take place

35
Q

What is the main Physical factor affecting membrane fluidity, name another factor?

A

Temperature
Molecular mass of phospholipid

36
Q

What are the ways that individual phospholipid molecules move?

A

Individual chain bond Flexion/vibration (wobbly bob)

Fast axial rotation (whole lipid spins on head)

Fast lateral diffusion (lipid moves randomly through bilayer

Protrusion (Bobbing up and down)

Flip-flop

37
Q

How is vibration/movement of phospholipid molecules affected by temperature and molecular mass?

A

Higher temp = higher vibration
Higher molecular mass = less vibration

38
Q

How do cell membrane bilayers behave that have saturated phospholipids at 37ºC?

A

Fluid behaviour

39
Q

How does adding unsaturated phospholipid to a membrane bilayer affect its fluidity?

A

Decreases the temperature by which the membrane changes form a gel to fluid state

INCREASES FLUIDITY

40
Q

How does adding unsaturated phospholipids to cell membrane increase its fluidity?

A

Due to the cis C=C bond with kink
Less dense packing of fatty acid tails

41
Q

At high temperatures, what type of movement of phospholipids happens too much causing the structural integrity of the membrane to become too disordered?

A

Increased bond chain Flexion/vibration

42
Q

What does cholesterol due to the range of fluidity?

A

Increases range by making membrane fluid at lower temperatures

43
Q

How does cholesterol stabilise the membrane at higher temperatures?

A

-OH polar group of cholesterol binds to acyl group of phospholipid head

Rigid carbon rings limits movement of fatty acid tails

44
Q

How does cholesterol increase the fluidity of the membrane at low temperatures?

A

Interferes with crystalline packing of the fatty acid chainns

45
Q

How is water important in the structure of the membrane?

A

It dynamically interacts with the membrane

46
Q

What is a lipid raft?

A

Areas of organised/specialised distribution of lipids in cell membranes

47
Q

What molecules are increased in numbers in lipid rafts?

A

Cholesterol
Sphingomyelin
Glycolipids

48
Q

What is the role of lipid rafts?

A

Role in stabilising and organising proteins
Domains for receptors and signalling molecules

49
Q

What is the importance of the membrane fluid and flexible?

A

Protein function
Able to transmit force throughout cell structures

50
Q

Why is it important for forces to be distribute throughout the whole body?

A

Excessive force that is localised can cause damage

ICPP (23 decks)

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