FoM:L3- Biomembranes

Question 1

What are amphiphatic phospholipids?

Answer 1

• phospholipids that have a polar and non-polar region
• form membranes that define exterior edges of animal cells and divide organelles into compartments

Question 2

Describe the structure of a phospholipid in detail…

Answer 2

• 2 OH groups in glycerol are linked to fatty acids, 3rd is phosphorylated
• phosphate is further linked to a small, polar, alcohol head group (phosphatidyl…choline, serine, ethanolamine, inositol)

Question 3

What are the 2 faces of a membrane called?

Answer 3

cytosolic and exoplasmic

Question 4

Describe the 2 faces of membranes

Answer 4

• asymmetrical in lipid composition
• cell damage can cause deviation from these asymmetries

Question 5

Give an example of a specific phospholipid in mitochondria

Answer 5

cardiolipin - greater insulation

Question 6

What are flippases?

Answer 6

enzymes that can move phospholipids around, to mark the cell for apoptosis

Question 7

What is the inner leaflet mostly made of?

Answer 7

sphinomyelin and phosphatidylcholine

Question 8

What is the outer leaflet made of?

Answer 8

phosphatidylinositol, phosphatidylserine and phosphatidylethanolamine

Question 9

What are sphingolipids?

Answer 9

• contain sphingosine instead of glycerol

Question 10

What are glycolipids?

Answer 10

• carbohydrates combined with simple lipids (glucose and galactose)
• for example blood group antigens

Question 11

How does the liquid crystalline phase relate to lipids?

Answer 11

• lipids contain fatty acids; saturated or unsaturated
• saturated are more compact; membrane less fluid
• unsaturated are less compact; membrane is more fluid

Question 12

What does: 22:6n-3 mean?

Answer 12

• 22 C atoms
• 6 double bonds
• location of first double bond

Question 13

Why do we need membrane flexibility?

Answer 13

• membranes need to change shape to perform their function
• movement to allow changes in the shape of proteins (eg rhodopsin)
• physical movement of cells (phagocytosis)

Question 14

What are lipid rafts?

Answer 14

lipid-dense areas with high amounts of cholesterol making them more structured and rigid. Involved in signalling

Question 15

What receptors are lipids directly involved with?

Answer 15

• G protein coupled receptors
• Nuclear receptors

Question 16

What is a property of lipids that allows them to function?

Answer 16

• easily metabolised
• allows fluidity in membrane
• bilayer formation
• form lipid rafts

Question 17

What is endocytosis?

Answer 17

substance moving into a cell without it having to pass through the membrane

Question 18

Outline the process of endocytosis

Answer 18

membrane folds inwards and takes in extracellular substances in a small sphere - vesicle

Question 19

What is receptor mediated endocytosis?

Answer 19

• specific endocytosis
• selective uptake of larger molecules (e.g. LDL)

Question 20

What is pinocytosis?

Answer 20

non-selective uptake of fluids and solutes in vesicles

Question 21

What does receptor mediated endocytosis form?

Answer 21

coated pits

Question 22

What is exocytosis?

Answer 22

contents of the cell vesicle are released to the exterior through the fusion of the vesicle with the cell membrane

Question 23

What is Chédiak–Higashi syndrome?

Answer 23

• rare autosomal recessive disorder
• mutation of a lysosomal trafficking regulator protein
• decrease in phagocytosis

Question 24

What is CEDNIK syndrome?

Answer 24

• rare congenital condition - failure of intracellular vesicle fusion
• abnormal deposition of
  epidermal lipids and proteases

Question 25

What are the 3 types of membrane proteins?

Answer 25

• integral
• peripheral
• transmembrane

Question 26

What are integral membrane proteins?

Answer 26

• in the lipid bilayer
• Transport

Question 27

What are peripheral membrane proteins?

Answer 27

• not embedded in bilayer
• support
• transport
• cell signalling