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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
What is facilitated diffusion
``` 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) ```
26
What are ionophore
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
27
What are ion channels
``` Rapid and gated passage of anions and cations Highly selective Ions flow down conc gradient Osmotic balance maintaining Signal transduction Nerve impulses ```
28
What glucose transport facilitated diffusion
Transport of glucose into erythrocytes | Glucose transporter integral membrane protein GLUT1
29
How is the glucose conc gradient maintained
Hexokinase modifies glucose by adding a phosphate to make glucose-6-phosphate
30
What are aquaporins
Water channel proteins required for the bulk flow of water across cell membranes
31
How does the the Na+/K+ gradient work
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
32
How does Na+/K+ATPase work
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
33
What is ion-driven active transport
Movement of molecule is coupled to ion movement
34
What are the two types of ion driven active transport
symport | antiport
35
What are cardiac glycosides
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
What are the characteristics of intestinal epithelial cells
Line the lumen of small intestine Large surface area for absorption Absorb nutrients from digested food Transfer nutrients into the blood
37
How is glucose moved from intestinal lumen to blood
Glucose moves into intestinal epithelial cell by Na+/glucose symport transporter -> moves out of cell into blood via GLUT2 glucose transporter
38
What is exocytosis and what are the two types
Secretion of molecules out of the cell Constitutive: in all cells for secretory proteins Regulated: in specialised cells when signalled by Ca2+
39
What is endocytosis and what are the three types
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
What are the phagocytes and where are they found
macrophages, neutrophils and dendritic cells | In the immune system
41
What are the types of intercellular signalling
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
What are the types of extracellular signalling molecules
``` Hormones Neuro transmitters Growth factors Cytokines Gasotransmitters ```
43
What are the types of receptors
Ligans-gated G Protein Coupled Receptor Kinase-linked Nuclear hormone
44
Why do cells communicate
To regulate development and organisation into tissues Control their growth and division Co-ordinate their functions
45
How can cell communication go wrong
``` Signal is lost Signal is no longer sent Target ignores signal Signal doesn't reach the target Too much signal Multiple breakdowns ```
46
How can cells communicate
Remote signalling by secreted molecules | Contact signalling by plasma membrane bound molecules or contact signalling via gap junctions
47
What are the functions of hormones
``` 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
Why are there different receptor subtypes
To allow different cell to respond differently to the same hormone
49
What is the process of the Renin-angiotensin system
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
What are the strategies devised to control RAS activity
Inhibit renin release and/or activity ACE inhibitors AT1 receptor antagonists Aldosterone receptor antagonists
51
What is the life cycle of a neurotransmitter
``` Synthesis Storage Release Receptor activation Neurotransmitter inactivation ```
52
How do drug act on neurotransmitters
At any stage in the neurotransmitters life cycle to modulate their action
53
What are the two types of depression
Unipolar | Bipolar
54
What causes depression
Functional deficit of monoaminergic (noradrenaline, dopamine, serotonin) transmission
55
What are the treatment options for depression
``` Monoamine reuptake inhibitors Monoamine oxidase inhibitors Miscellaneous "atypical" antidepressants Electroconvulsive therapy Mood stabilising drugs ```
56
What is signal transduction responsible for
Regulating almost every aspect of physiological function at the cellular level
57
What is hierarchy of signal transduction
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
How many transmembrane domains do GCRPs have
7
59
What is the amplification of signal
Single molecule signal has a large effect inside the cell
60
What are the three sites of signal amplification
G-protein Effector enzyme Protein Kinase
61
What is the function G-proteins
Hydrolyse GTP -> GDP
62
What are the two groups of G-proteins
Receptor associated: heterotrimeric | Small GTPase: monomeric
63
What are the three alpa G protein subunits
Linked to specificity of signalling Gia Gsa Gqa
64
What is a 2nd messenger
A short-acting intracellular molecular that is rapidly formed or released as a result of receptor activation
65
What are the 5 common 2nd messengers
``` cyclic AMP cyclic GMP Diacylglycerol Inositol 1,4,5-triphosphate Intracellular calcium ```
66
What are the three amino acid residues which can be phosphorylated
Serine Threonine Tyrosine
67
What are the functions of lipids
``` Energy storage Major components of cell membranes Required to solubilise fat soluble vitamins Biosynthetic precursors Signalling molecules ```
68
How is fat transported
By a carrier to form a lipoprotein which are particles in plasma
69
What are the four main classifications of lipoproteins
VLDL (very low density lipids) LDL (Low density lipids) HDL (high density lipids) Chylomicrons
70
What do chylomicrons do
transport dietary fats from intestines to tissues
71
What do VLDL do
transport lipids made in the liver to the peripheral tissues
72
What do LDL do
Provide cholesterol for peripheral tissues | Main carrier of cholesterol
73
What do HDL do
Transport cholesterol to liver from peripheral tissues
74
What determines the function of each lipoprotein
the specific protein strands embedded in the surface of lipoprotein
75
What are the major classes of apolipoproteins
ApoA ApoB ApoC ApoE
76
What is the result of mutations affecting LDL receptors
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
How does an atherosclerotic plaque develop
Normal artery -> fatty streak -> fibrous plaque -> advanced plaque
78
What is the cholesterol-sythetic pathway
HMG-CoA -> Mevalomate -> IPP -> FPP -> Squalene -> Cholesterol
79
How is the cholesterol-sythetic pathway regulated
HMG-CoA reductase
80
What two organs control blood cholesterol levels
Liver | Intestine
81
How is hypercholesterolaemia controlled pharmacologically
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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