Membrane Structure & Synthesis

Question 1

How many membranes are there in the body?

Answer 1

Multiple different types of biological membranes with varying compositions and functions

Question 2

Which part of the phospholipid is hydrophobic?

Answer 2

The tails - composed of the fatty acid chains

Question 3

What significant structure do phospholipids form?

Answer 3

lipid Bi layers (membranes)

Question 4

What causes the asymmetry of membranes?

Answer 4

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

Question 5

What are the different components of a lipid molecule?

Answer 5

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

Question 6

How can we describe the fluid nature of membranes?

Answer 6

Dynamic and flexible

Question 7

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

Answer 7

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

Question 8

What is Spur Cell anemia?

Answer 8

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

Question 9

What are the two movement types in a membrane?

Answer 9

1. Lateral

2. Transverse

Question 10

What is apoptosis?

Answer 10

Programmed cell death

Question 11

How does a highly saturated membrane affect fluidity?

Answer 11

Molecules pack closer together
Decrease fluidity
Increase rigidity

Question 12

What facilitates the transverse movement of newly synthesised membrane?

Answer 12

ABC transport proteins (enzymes)

Question 13

Where is the new membrane formed?

Answer 13

Formed from the ER to the golgi

Question 14

What is transverse movement in the membrane?

Answer 14

Movement across the membrane (flipping to the other side)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

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

Answer 17

Transverse movement

Question 18

List the common features of biological membranes

Answer 18

• Asymmetrical
• Fluid
• Bi layers
• Electrically polarised
• Specific protein functions

Question 19

Why is lateral movement so rapid?

Answer 19

Due to diffusion being a passive process

Question 20

Why are phospholipids described as being amphipathic?

Answer 20

They are both hydrophilic and hydrophobic

Question 21

What are lipid anchored proteins?

Answer 21

Membrane proteins covalently linked to a lipid

e.g. glycerophosphatidylinositol

Question 22

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

Answer 22

Membrane is synthesised on the the cytosilic membrane only

Causes a bowed shape - deformation

Question 23

What is phosphotidylserine ?

Answer 23

A phospholipid involved in apoptosis

Question 24

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

Answer 24

membrane carbohydrates form 2% of cell weight

Question 25

What factors affect the membrane fluidity?

Answer 25

Temperature Degree of saturation Fatty acid length Cholesterol content

Question 26

Where are new membrane synthesising enzymes found ?

Answer 26

Cytosilic surface of golgi apparatus

Question 27

What is the purpose of apoptosis?

Answer 27

Allows body to turnover cells without inducing inflammatory response

Question 28

Which membrane movement type is faster?

Answer 28

Lateral movement

Question 29

Where are membrane carbohydrates found on the membrane?

Answer 29

Facing away from the cytosol

Question 30

Where do the hydrophilic heads on the membrane face?

Answer 30

Extracellular surface

Question 31

Where are peripheral membrane proteins found on the membrane?

Answer 31

Located on extracellular (cytosolic) side

Question 32

What components can we expect in biological membranes?

Answer 32

- Phospholipids - Cholesterol - Glycolipids (not all membranes contain all 3)

Question 33

What facilitates movement in the membrane?

Answer 33

Enzymes

Question 34

Describe what the structure of peripheral membrane proteins is like

Answer 34

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

Question 35

How does an increase in temperature affect membrane fluidity?

Answer 35

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

Question 36

Give examples of some membranes present in the body

Answer 36

Nuclear membrane Plasma membrane Mitochondrial membrane

Question 37

Explain what is meant by lateral membrane movement

Answer 37

Along the plane of the membrane

Question 38

How do the phospholipids arrange in bi layers?

Answer 38

They readily form bi molecular sheets in aqueous media

Question 39

How is fluid is the membrane when unsaturated?

Answer 39

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

Question 40

What are 3 types of ABC enzyme proteins?

Answer 40

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

Question 41

What other molecules do membrane carbohydrates associate with?

Answer 41

Both lipids and proteins

Question 42

Describe the structural features of integral membrane proteins

Answer 42

" 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

Question 43

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

Answer 43

Cholesterol maintains membrane stability (decreases fluidity)

Question 44

Outline how apoptosis occurs in cells

Answer 44

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

Question 45

What is the role of membrane carbohydrates?

Answer 45

Allow cells to interact with each other and the extracellular membrane

Question 46

What effect does cholesterol have on the membrane?

Answer 46

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

Question 47

What is the significance of ABC enzyme proteins?

Answer 47

They are crucial in establishing membrane asymmetry

Question 48

Name the different proteins present in a membrane

Answer 48

Integral membrane proteins Peripheral membrane proteins Lipid anchored proteins

Question 49

Why is the membrane described as fluid mosaic?

Answer 49

Fluid - components able to move around | Mosaic - composed of many different Proteins

Question 50

How is apoptosis initiated?

Answer 50

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

Question 51

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

Answer 51

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

Question 52

Why is transverse movement slow?

Answer 52

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