Membrane proteins and carbohydrates Flashcards
What are membrane proteins required for
- movement of metabolites
- signalling
What are the three types of membrane proteins
- integral (intrinsic) proteins
- lipid-linked proteins
- peripheral (extrinsic) proteins
Describe integral proteins
- single or multiple transmembrane
- interact with fatty acid chains in hydrophobic interior
What are transmembrane regions made up of
- amino acids
- hydrophobic chains
How are integral proteins extracted
- disturbing membrane with organic solvents
Give two examples of integral proteins
- glycophorin A
- bacteriorhodopsin
Describe glycophorin A
- single TM
- asymmetrically oriented
- glycosylated
Describe becteriorhodopsin
- multiple TMs
- 20-30 aas in a-helix —> cross the 45A thick membrane
- short loops on sides of membrane
Describe lipid-linked proteins
- covalently linked to lipid
- lipid inserted in membrane
Give examples of lipid-linked proteins
- prion
- viral
- signalling
- insulin
Describe peripheral proteins
- no interaction with hydrophobic core
- interact with lipid headgroups
- soluble in aqueous solution
How are peripheral proteins removed
High salt soln
Give examples of peripheral proteins
Cytoskeletal proteins
Give examples of cytoskeletal proteins
- spectrins
- ankyrin
- actin
- band 4.1
What do spectrins do
Form 200nm long filaments
What do ankyrin do
Bridges spectrins and band 3 proteins
What do actin do
Joins spectrin filaments
What do band 4.1 do
Stabilises spectrin-actin interaction
What happens if peripheral proteins are removed from RBCs
- lose rigid shape
- proteins become mobile
What is the function of cytoskeleton proteins
- maintain shape & rigidity
- restrict lateral motion on integral proteins
What causes spherocytosis & elliptocytosis
- mutations in genes encoding spectrin and ankyrin
- abnormally shared erythrocytes
- degraded more rapidly —> spleen action
What do spherocytosis & elliptocytosis cause
Anaemia
What causes AD symptoms
- brain nerve cells dying
- connections between nerve cells degenerating
- loss of part of brain dealing with memory
What are the clinical features of AD
- amnesia
- aphasia
- agnosia
- apraxia
- visuopatial difficulties
- functional impairment
- mood disorders
- psychosis
- personality change
What causes AD
Neurone malfunction
What are the types of drugs used to treat AD
- cholinesterase inhibitors
- NMDA receptor antagonist
- anti-psychotic drugs
Name cholinesterase inhibitors
- aricept
- exelon
- Reminyl
Name NMDA receptor antagonist
Ebixa
What do AD drugs do
Relieve symptoms, not cure
What does cholesterol cause in heart diseased ppl
Increased no. of amyloid plaques
What does cholesterol cause in heart diseased ppl
Increased no. of amyloid plaques
Describe relationship between cholesterol and AD
- Apolipoprotein E4 (cholesterol transport) more abundant in AD
Describe relationship between statins & AD
- ppl with statins —> 70% lower AD cases
What do statins do
- lower Ab production
- alter cholesterol content —> more fluid
What do statins don’t do
Slow progression in AD patients
What is Ab believed to contribute to
- aggregation
- development of AD
What do O-linked glycoproteins contain
Carbohydrate attached to serine/threonine
What do N-linked glycoproteins contain
Carbohydrate attached to asparagine amino acid (anything that’s not proline)
What is the function of carbohydrates
- stabilise proteins
- intercellular recognition
Eg blood antigens
What is the function of carbohydrates
- stabilise proteins
- intercellular recognition
Eg blood antigens
How are O,A & B antigens recognised
- O: no extra sugar
- A: N-acetyl-galactosamine
- B: Galactose
