Membrane proteins and carbohydrates

Question 1

What are membrane proteins required for

Answer 1

• movement of metabolites

- signalling

Question 2

What are the three types of membrane proteins

Answer 2

• integral (intrinsic) proteins
• lipid-linked proteins
• peripheral (extrinsic) proteins

Question 3

Describe integral proteins

Answer 3

• single or multiple transmembrane

- interact with fatty acid chains in hydrophobic interior

Question 4

What are transmembrane regions made up of

Answer 4

• amino acids

- hydrophobic chains

Question 5

How are integral proteins extracted

Answer 5

• disturbing membrane with organic solvents

Question 6

Give two examples of integral proteins

Answer 6

• glycophorin A

- bacteriorhodopsin

Question 7

Describe glycophorin A

Answer 7

• single TM
• asymmetrically oriented
• glycosylated

Question 8

Describe becteriorhodopsin

Answer 8

• multiple TMs
• 20-30 aas in a-helix —> cross the 45A thick membrane
• short loops on sides of membrane

Question 9

Describe lipid-linked proteins

Answer 9

• covalently linked to lipid

- lipid inserted in membrane

Question 10

Give examples of lipid-linked proteins

Answer 10

• prion
• viral
• signalling
• insulin

Question 11

Describe peripheral proteins

Answer 11

• no interaction with hydrophobic core
• interact with lipid headgroups
• soluble in aqueous solution

Question 12

How are peripheral proteins removed

Answer 12

High salt soln

Question 13

Give examples of peripheral proteins

Answer 13

Cytoskeletal proteins

Question 14

Give examples of cytoskeletal proteins

Answer 14

• spectrins
• ankyrin
• actin
• band 4.1

Question 15

What do spectrins do

Answer 15

Form 200nm long filaments

Question 16

What do ankyrin do

Answer 16

Bridges spectrins and band 3 proteins

Question 17

What do actin do

Answer 17

Joins spectrin filaments

Question 18

What do band 4.1 do

Answer 18

Stabilises spectrin-actin interaction

Question 19

What happens if peripheral proteins are removed from RBCs

Answer 19

• lose rigid shape

- proteins become mobile

Question 20

What is the function of cytoskeleton proteins

Answer 20

• maintain shape & rigidity

- restrict lateral motion on integral proteins

Question 21

What causes spherocytosis & elliptocytosis

Answer 21

• mutations in genes encoding spectrin and ankyrin
• abnormally shared erythrocytes
• degraded more rapidly —> spleen action

Question 22

What do spherocytosis & elliptocytosis cause

Answer 22

Anaemia

Question 23

What causes AD symptoms

Answer 23

• brain nerve cells dying
• connections between nerve cells degenerating
• loss of part of brain dealing with memory

Question 24

What are the clinical features of AD

Answer 24

• amnesia
• aphasia
• agnosia
• apraxia
• visuopatial difficulties
• functional impairment
• mood disorders
• psychosis
• personality change

Question 25

What causes AD

Answer 25

Neurone malfunction

Question 26

What are the types of drugs used to treat AD

Answer 26

- cholinesterase inhibitors - NMDA receptor antagonist - anti-psychotic drugs

Question 27

Name cholinesterase inhibitors

Answer 27

- aricept - exelon - Reminyl

Question 28

Name NMDA receptor antagonist

Answer 28

Ebixa

Question 29

What do AD drugs do

Answer 29

Relieve symptoms, not cure

Question 30

What does cholesterol cause in heart diseased ppl

Answer 30

Increased no. of amyloid plaques

Question 31

What does cholesterol cause in heart diseased ppl

Answer 31

Increased no. of amyloid plaques

Question 32

Describe relationship between cholesterol and AD

Answer 32

- Apolipoprotein E4 (cholesterol transport) more abundant in AD

Question 33

Describe relationship between statins & AD

Answer 33

- ppl with statins —> 70% lower AD cases

Question 34

What do statins do

Answer 34

- lower Ab production | - alter cholesterol content —> more fluid

Question 35

What do statins don’t do

Answer 35

Slow progression in AD patients

Question 36

What is Ab believed to contribute to

Answer 36

- aggregation | - development of AD

Question 37

What do O-linked glycoproteins contain

Answer 37

Carbohydrate attached to serine/threonine

Question 38

What do N-linked glycoproteins contain

Answer 38

Carbohydrate attached to asparagine amino acid (anything that’s not proline)

Question 39

What is the function of carbohydrates

Answer 39

- stabilise proteins - intercellular recognition Eg blood antigens

Question 40

What is the function of carbohydrates

Answer 40

- stabilise proteins - intercellular recognition Eg blood antigens

Question 41

How are O,A & B antigens recognised

Answer 41

- O: no extra sugar - A: N-acetyl-galactosamine - B: Galactose