Cell Membranes

Question 1

What are the three main components of a phospholipid?

Answer 1

Acyl groups
Phosphate group
Head group
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Question 2

Name and describe the different charges of phospholipids

Answer 2

Anionic phospholipids have a net negative charge
Zwitterionic have zero charge

Question 3

What are the three types of phospholipid?

Answer 3

Glycerophospholipids
Sphingolipids
Sterols

Question 4

What are the key functions of cell membranes?

Answer 4

• Provide a functional barrier
• Provide cells with energy
• Organise and regulate enzyme activities
• Facilitate signal transduction
• Supply substrates for biosynthesis and for signalling molecules

Question 5

What are the two types of tail of glycerophospholipids?

Answer 5

The sn-1 fatty acid (usually saturated)
The sn-2 fatty acid (usually mono/poly-saturated)

Question 6

What are the main structural components of a sphingolipid?

Answer 6

Sphingoid base backbone
Head group
N-Acyl chain
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Question 7

What type of membrane lipid is important in cell to cell adhesion?

Answer 7

Glycosphingolipids

Question 8

Where are glycosphingolipids exclusively found?

Answer 8

In the outer leaflet of the membrane

Question 9

What do glycosphingolipids have in place of a head?

Answer 9

Different oligosaccharides

Question 10

What is the structure of sterols?

Answer 10

Hydroxyl group and hydrocarbon tail
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Question 11

Where are the following sterols found?
-cholesterol
-ergosterol
-sitosterol and stigmasterol

Answer 11

Cholesterol = animals
Ergosterol = fungi and yeast
Sitosterol and stigmasterol = plants

Question 12

What factors affect the shape of the lipid?

Answer 12

relative size of head group and hydrophobic tails

Question 13

What are the three types of lipid movement in membranes and how do they work?

Answer 13

Rotational - when lipids spin around their axis, not changing position but interacting differently

Lateral - neighbouring lipids exchange spaces

Transverse - exchange of lipids between leaflets, sometimes requires ATP

Question 14

What are membrane rafts?

Answer 14

In eukaryotic plasma membrane there are domains with lots of cholesterol and sphingomyelin making them more rigid

Question 15

What are the three different classes of membrane proteins?

Answer 15

Integral (intrinsic)
Lipid-linked
Peripheral (extrinsic)

Question 16

What are the roles of integral membrane proteins?

Answer 16

Transport
Enzymatic activity
Signal transduction
Cell-cell interactions
Attachment to the cytoskeleton or extracellular matrix

Question 17

What molecule is this?..
- found in nearly all cells
- composed of 12 a helices
- undergoes conformational change causing transport across membrane

Answer 17

GLUT (glucose transporter)

Question 18

What things can cause integral channel proteins to open?

Answer 18

Ligand binding
electric potential
pH
Temperature
Pressure
Lipids

Question 19

What is the role of carbohydrates in cell membranes?

Answer 19

Stabilisation of proteins
Cell-cell recognition

Question 20

What causes Alzheimer’s disease?

Answer 20

Nerves cells in the brain die causing the connections between cells to degenerate
Loss of memory is usually the first presenting symptom

Question 21

What will you find in the brain of an Alzheimer’s patient during a postmortem?

Answer 21

Full of senile-plaques made of amyloid-beta peptide

Question 22

What is hereditary spherocytosis?

Answer 22

Loss of cohesion between the plasma membrane and skeleton as a result of defective anchoring
Cell shape changes to spherocytes

Question 23

What is the most common cause of hereditary spherocytosis?

Answer 23

Anaemias
Deficiencies in ankyrin, spectrin, band 3

Question 24

What are the main types of lipids in the body?

Answer 24

Triglycerides
Cholesterol
Phospholipids
Steroids

Question 25

What are the functions of lipids?

Answer 25

Energy storage
Major components of membranes
Signalling molecules
Solubisung fat soluble vitamins
Bio synthetic precursors

Question 26

Where does cholesterol come from?

Answer 26

From diet or synthesised in the liver

Question 27

What is the role of lipoproteins?

Answer 27

Transporting lipids in the plasma

Question 28

Describe the structure of lipoproteins?

Answer 28

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Question 29

What determines the function of lipoproteins?

Answer 29

Apolipoproteins - Specific protein strands embedded in the surface of lipoproteins

Question 30

What is the function of the following lipoproteins? INSERT PIC

Answer 30

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Question 31

What does lipid + apolipoprotein =

Answer 31

Lipoprotein

Question 32

What are the different classes of apolipoproteins?

Answer 32

ApoA - present in HDL
ApoB - recognises apoB/E receptors, facilitates LDL uptake
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Question 33

Where is the synthesis of apolipoproteins regulates?

Answer 33

By dietary fat intake
By hormones/drugs in the liver

Question 34

Describe the structure of LDL

Answer 34

ApoB wraps round the circumference
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Question 35

Describe the structure of HDL

Question 36

Why is HDL considered good cholesterol?

Answer 36

ApoB prevents it from being oxidised

Question 37

What pH is a lysosome?

Answer 37

<5

Question 38

What are the two types of both passive and active transport of small molecules?

Answer 38

Passive - simple and faciliated diffusion
Active - ATP driven and ion driven

Question 39

What type of transport is this?
- no metabolic energy required
- small molecules
- no specificity
- rate of diffusion proportional to concentration gradient

Answer 39

Simple diffusion

Question 40

What type of transport is this?
- occurs down a concentration gradient
- no energy required
- depends on integral membrane proteins
- proteins are specific
- similar kinetics to enzymes

Answer 40

Facilitated diffusion