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Y1 IMS > Membranes > Flashcards

Membranes Flashcards

1
Q

What is a lipid raft

A

A section of the lipid membrane where the average composition of a patch of the membrane is different from the bulk composition
Rich in cholesterol

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2
Q

How can lipids move in a membrane

A 
Lateral diffusion (easily)
Rotation ( easily)
Transverse diffusion (difficult)
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3
Q

What do translocase enzymes do

A

They enable the transverse diffusion of the same type of lipids

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4
Q

What do scrambalase enzymes do

A

They enable the transverse diffusion of the any type of lipids

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5
Q

Why is apoptosis triggered

A

Cell are not useful and are using unnecessary resources
or
Cells realise that they are infected

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6
Q

What is the process of apoptosis

A

cell shrinkage and DNA fragmentation -> membrane blebbing -> apoptotic bodies -> phagocytosis of apoptotic bodies

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7
Q

What is dementia

A

An umbrella term describing a serious deterioration in mental functions such as memory, language, orientation and judgement

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8
Q

What are the main symptoms of Alzheimer’s disease

A 
Amnesia
Aphasia
Agnosia
Apraxia
Visuospatial difficulties
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9
Q

What causes Alzheimers disease

A

Neurons malfunction and die in the brain

Senile plaques of amylase B

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10
Q

What are the treatments of the symptoms of Alzheimers

A

Cholinesterase inhibitors

NMDA receptor antagonist

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11
Q

What are the three types of membrane proteins

A

Integral (intrinsic) membrane protein
Lipid-linked membrane protein
Peripheral (extrinsic) membrane proteins

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12
Q

What are integral membrane proteins

A

Span the membrane with single or multiple transmembrane (TM) segments
Interact with fatty acid chains
TM regions made of hydrophobic side chains

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13
Q

What are lipid-linked membrane proteins

A

Proteins which contain covalently attached fatty acids that bind the protein to the membrane

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14
Q

What are peripheral membrane proteins

A

Do not interact with hydrophobic core of bilayer
Interact with lipid head-groups or other proteins
Readily removed by high salt solution
Soluble in aqueous solution

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15
Q

What are examples of peripheral membrane proteins

A

cytoskeletal proteins
spectrin
actin

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16
Q

What are glycoproteins and glycolipids and where are they found

A

Carbohydrates attached to proteins and lipids

Extracellular face of membrane

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17
Q

What are the function of membrane carbohydrates

A

Stability of proteins

Intercellular recognition

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18
Q

What are the symptoms of cholera

A

Severe diarrhoea

Vomiting

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19
Q

What is the virulence factor of cholera

A

Cholera toxin

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20
Q

How is cholera treated

A

Oral rehydration therapy of water salts and glucose

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21
Q

What is a pure lipid bilayer permeable to

A

Only H2O, small hydrophobic molecules and small uncharged molecules

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22
Q

What is passive transport and what are the two types

A

Transport which does not require energy
Simple diffusion
Facilitated diffusion

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23
Q

What is active transport and what are the two types

A

Transport which requires energy as moving molecules against conc gradient
ATP driven
Ion driven

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24
Q

What is simple diffusion

A

No metabolic energy needed
Small molecules
No specificity
Rate of diffusion proportional to concentration gradient

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25
Q

What is facilitated diffusion

A 
No energy required 
Occurs down conc gradient
Depends on integral membrane proteins
Proteins are specific
Similar kinetics to enzymes (dependent on temp, pH, saturable, inhibitable)
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26
Q

What are ionophore

A

Ion carrier
Antibiotic produced by bacteria to kill competing bacteria
Free transport of ions discharges ion gradients of target cell
Two types:
Carrier and channel-forming

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27
Q

What are ion channels

A 
Rapid and gated passage of anions and cations
Highly selective
Ions flow down conc gradient
Osmotic balance maintaining 
Signal transduction
Nerve impulses
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28
Q

What glucose transport facilitated diffusion

A

Transport of glucose into erythrocytes

Glucose transporter integral membrane protein GLUT1

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29
Q

How is the glucose conc gradient maintained

A

Hexokinase modifies glucose by adding a phosphate to make glucose-6-phosphate

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30
Q

What are aquaporins

A

Water channel proteins required for the bulk flow of water across cell membranes

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31
Q

How does the the Na+/K+ gradient work

A

High [K+], low [Na+] in cell
Controls cell volume
Makes nerve and muscle cells electrically excitable
Facilitates ion-driven active transports of amino acids and sugars
Maintained by Na+/K+ATPase

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32
Q

How does Na+/K+ATPase work

A

Pumps 3 Na+ ions out and 2 K+ ions into the cell
Polarises the cell membrane
ATP hydrolysis induces conformational changes, allowing pumping of Na+ and K+ against conc gradients
Coupled system

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33
Q

What is ion-driven active transport

A

Movement of molecule is coupled to ion movement

34
Q

What are the two types of ion driven active transport

A

symport

antiport

35
Q

What are cardiac glycosides

A

Used in congestive heart failure
Plant steroids
Inhibit Na+/K+ATPase
Therefore decreases Na+ gradient across membrane
So increases conc Ca2+ inside cell
Enhances strength of contraction of heart muscle

36
Q

What are the characteristics of intestinal epithelial cells

A

Line the lumen of small intestine
Large surface area for absorption
Absorb nutrients from digested food
Transfer nutrients into the blood

37
Q

How is glucose moved from intestinal lumen to blood

A

Glucose moves into intestinal epithelial cell by Na+/glucose symport transporter -> moves out of cell into blood via GLUT2 glucose transporter

38
Q

What is exocytosis and what are the two types

A

Secretion of molecules out of the cell
Constitutive: in all cells for secretory proteins
Regulated: in specialised cells when signalled by Ca2+

39
Q

What is endocytosis and what are the three types

A

Taking up of molecules into the cell
Phagocytosis: ingestion of large particles by specialised cells
Pinocytosis: uptake of fluid by all cells
Receptor-mediated endocytosis: molecules bound to receptors are taken up into the cells

40
Q

What are the phagocytes and where are they found

A

macrophages, neutrophils and dendritic cells

In the immune system

41
Q

What are the types of intercellular signalling

A

Paracrine: nearby target cell
Endocrine: transported round blood stream to far away target cell
Autocrine: own target
Neuronal: stimulus detected, converted to electrical signal, released as chemical signal to target cell
Juxtacrine: Physical association of two cells by membrane bound molecules

42
Q

What are the types of extracellular signalling molecules

A 
Hormones
Neuro transmitters
Growth factors
Cytokines
Gasotransmitters
43
Q

What are the types of receptors

A

Ligans-gated
G Protein Coupled Receptor
Kinase-linked
Nuclear hormone

44
Q

Why do cells communicate

A

To regulate development and organisation into tissues
Control their growth and division
Co-ordinate their functions

45
Q

How can cell communication go wrong

A 
Signal is lost
Signal is no longer sent
Target ignores signal
Signal doesn't reach the target
Too much signal
Multiple breakdowns
46
Q

How can cells communicate

A

Remote signalling by secreted molecules

Contact signalling by plasma membrane bound molecules or contact signalling via gap junctions

47
Q

What are the functions of hormones

A 
Regulate: 
Body's energy needs,
Protein and nucleic acid metabolism,
Mineral and electrolyte metabolism,
Synthesis and release of hormones
Activity is regulated by positive and negative feedback
48
Q

Why are there different receptor subtypes

A

To allow different cell to respond differently to the same hormone

49
Q

What is the process of the Renin-angiotensin system

A

Decrease in renal perfusion causes release of RENIN -> This cleaves ANGIOTENSINOGEN in liver to ANGIOTENSIN I -> ANGIOTENSIN I is converted to ANGIOTENSIN II by enzyme ACE -> This causes the effects which together increase blood pressure -> feedback loop

50
Q

What are the strategies devised to control RAS activity

A

Inhibit renin release and/or activity
ACE inhibitors
AT1 receptor antagonists
Aldosterone receptor antagonists

51
Q

What is the life cycle of a neurotransmitter

A 
Synthesis
Storage
Release
Receptor activation
Neurotransmitter inactivation
52
Q

How do drug act on neurotransmitters

A

At any stage in the neurotransmitters life cycle to modulate their action

53
Q

What are the two types of depression

A

Unipolar

Bipolar

54
Q

What causes depression

A

Functional deficit of monoaminergic (noradrenaline, dopamine, serotonin) transmission

55
Q

What are the treatment options for depression

A 
Monoamine reuptake inhibitors
Monoamine oxidase inhibitors 
Miscellaneous "atypical" antidepressants
Electroconvulsive therapy
Mood stabilising drugs
56
Q

What is signal transduction responsible for

A

Regulating almost every aspect of physiological function at the cellular level

57
Q

What is hierarchy of signal transduction

A

Things happen in a certain order
1st messenger -> receptor -> conformational change -> activates G protein -> Effector enzyme -> 2nd messenger -> protein kinases -> target proteins -> cellular response

58
Q

How many transmembrane domains do GCRPs have

A

7

59
Q

What is the amplification of signal

A

Single molecule signal has a large effect inside the cell

60
Q

What are the three sites of signal amplification

A

G-protein
Effector enzyme
Protein Kinase

61
Q

What is the function G-proteins

A

Hydrolyse GTP -> GDP

62
Q

What are the two groups of G-proteins

A

Receptor associated: heterotrimeric

Small GTPase: monomeric

63
Q

What are the three alpa G protein subunits

A

Linked to specificity of signalling
Gia
Gsa
Gqa

64
Q

What is a 2nd messenger

A

A short-acting intracellular molecular that is rapidly formed or released as a result of receptor activation

65
Q

What are the 5 common 2nd messengers

A 
cyclic AMP
cyclic GMP
Diacylglycerol
Inositol 1,4,5-triphosphate
Intracellular calcium
66
Q

What are the three amino acid residues which can be phosphorylated

A

Serine
Threonine
Tyrosine

67
Q

What are the functions of lipids

A 
Energy storage
Major components of cell membranes
Required to solubilise fat soluble vitamins
Biosynthetic precursors
Signalling molecules
68
Q

How is fat transported

A

By a carrier to form a lipoprotein which are particles in plasma

69
Q

What are the four main classifications of lipoproteins

A

VLDL (very low density lipids)
LDL (Low density lipids)
HDL (high density lipids) Chylomicrons

70
Q

What do chylomicrons do

A

transport dietary fats from intestines to tissues

71
Q

What do VLDL do

A

transport lipids made in the liver to the peripheral tissues

72
Q

What do LDL do

A

Provide cholesterol for peripheral tissues

Main carrier of cholesterol

73
Q

What do HDL do

A

Transport cholesterol to liver from peripheral tissues

74
Q

What determines the function of each lipoprotein

A

the specific protein strands embedded in the surface of lipoprotein

75
Q

What are the major classes of apolipoproteins

A

ApoA
ApoB
ApoC
ApoE

76
Q

What is the result of mutations affecting LDL receptors

A

Cells cannot take up LDL
Circulating LDL in plasma increase so excess cholesterol is deposited in the arteries leading to enhanced risk of developing atherosclerosis

77
Q

How does an atherosclerotic plaque develop

A

Normal artery -> fatty streak -> fibrous plaque -> advanced plaque

78
Q

What is the cholesterol-sythetic pathway

A

HMG-CoA -> Mevalomate -> IPP -> FPP -> Squalene -> Cholesterol

79
Q

How is the cholesterol-sythetic pathway regulated

A

HMG-CoA reductase

80
Q

What two organs control blood cholesterol levels

A

Liver

Intestine

81
Q

How is hypercholesterolaemia controlled pharmacologically

A

Statins: prevent cholesterol synthesis in the liver
Cholesterol absorption inhibitors: prevent uptake from the intestine
Fibrates: reduce triglycerides and increase HDL

Y1 IMS (9 decks)

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