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IMS 1 > S7- membranes > Flashcards

S7- membranes Flashcards

1
Q

functions of cell membranes include:

A
  1. functional barrier- compartmentalization of cells
  2. provide cells with energy (chemical and charge gradients ie: electron transport chain)
  3. organise and regulate enzymes
  4. facilitate signal transduction
  5. supply substances for biosynthesis and for signalling molecules
  6. protein recruitment platfom
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2
Q

3 main lipids that make up cell membrane are:

A
  1. glycerophospholipids (phospholipids)
  2. Sphingolipids
  3. sterols
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3
Q

most lipids are…(have hydrophillic/ head and hydrophobic/ tail regions)

A

amphipathic

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4
Q

fatty acids can be…or…
cis double bonds make…
trans double bonds make…

A

saturated lipid tails= no double bonds- chain is relatively straight
unsaturated= 1+ double bonds- 2 types

cis= 30 degree kink/ twist
trans= doesnt affect structure/ straight

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5
Q

glycerophospholipids have 3 parts:

fatty acid linkage is called…

A
  1. head group (phosphate+ alcohol)
  2. glycerol backbone (triol= each OH group is numbered 1-3)
  3. acyl chains/ 2 fatty acid chains

Ester/ acyl (OH from glycerol and fatty acid form H2O- esterification)

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6
Q

sn-1 fatty acid (on first OH of glycerol) is usually…
Sn-2 fatty acid is usually…

A

saturated or monounsaturated
monounsaturated or polyunsaturated

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7
Q

the basic structure of the membrane glycerophospholipids is called…

the rest of the phospholipids are derived from it, the phosphate group is further…

A

phosphatidic acid/ phosphatidate

esterified tot he hydroxyl group of one of several acohols (serine S, choline C, glycerol G, ethanolanime E, inositol I)

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8
Q

the anionic phospholipid are…and they have a net…

A

PS, PI, PG, CL (cardiolipin)—> they have more O- then positive charges (NH3+)
negatie charge

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9
Q

zwitterionic phospholipids have…

A

zero charges

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10
Q

PS and PE contain reactive…that can participate in…

A

Amines
hydrogen bonding

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11
Q

PI, PC, and CL are relatively…which affects their…

A

bulky
packing

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12
Q

some phospholipids are…specific
Ie: PG and CL are only found in the…

A

organelle
mitochondria

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13
Q

sphingolipids are built on 3 parts:

A

sphingoid base backbone, N-acyl (fatty acid) chain, head group (phosphate and another molecule attched to backbone)

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14
Q

N-acyl chains of phospholipids tend to be more…and…in sphingolipids than in glycerophospholipids

A

saturated
longer

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15
Q

N-acyl chain is attched via…in sphingolipids and the other amide group has the ability to form…(to allow interaction with cholesterol or polar parts of protein)

A

amide linkage
H bonds

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16
Q

the most common sphingolipid is…and it has a…head group

A

sphingomyelin
phosphocoline

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17
Q

glycosphingolipids have different…as head groups and are found exclusively in the…of the membrane and make around…% of that layer

A

oligosaccharides
outer lealflet of the membrane
5%

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18
Q

glycosphingolipids are exposed at surface membranes because it has an important role in…and allows membranes to act as….for certain chemicals

A

Cell-cell adhesion
recognition sites

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19
Q

sterols structure has…

A

4 fused rings (tetracyclic), hydroxyl group on A ring and a hydrocarbon tail (attached to last ring)

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20
Q

…is the most common sterol in animals
….is found in yeast and fungi
….and…are found in plants

A

Cholesterol
ergosterol
Sitosterol and stigmasterol

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21
Q

the size and shape of cholesterol allows it to…
its presence increases…and decreases…

A

interact with pockets in membrane proteins
thickness, packing, compressibility
mobility/ flexibility of lipids and proteins

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22
Q

in water, lipids bury their… in the interior and expose their….to water
They create a…or..shape

A

hydrophobic tails
hydropholic heads
Bilayer or micelles

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23
Q

3 types of membrane curvature are:

A
  1. cylindrical lipids= flat membrane (PC, PS)
  2. conical lipids= negative curvature (PE, acid)
  3. inverted-conical= positive curvature (PI)
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24
Q

membrane curvature is determined by…
negative curvature leads to…properties which might rpomote processes that involve…

A

relative sixe of head group and hydrophobic tails of lipids
Bilayer-disrupting
generation of non-bilayer membrane intermediates such a fusion

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25
Q

lipid asymmetry is…
-phosphatidylserine translocates to the…which cell undergoes apoptosis to act as…to macrophages to…

A

functionally important
extracellular monolayer
signal
come and digest it

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26
Q

glycolipids are oriented towards the…for cell-cell adhesion
second messengers in signalling pathways are oriented towards…

A

exterior of cell
the interior of cell

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27
Q

lipids in bilayer move with 3 different movements:

A
  1. Rotational: spinning of lipids around its axis (doesnt alter its position but affects interaction with neighbouring cells)
  2. lateral: neighbouring lipids exchange places= allows to change position within a bilayer leaflet
  3. Transverse: exchange of molecules between leaflets (move across bilayer) by transverse diffusion or mediated by proteins (unidirectional or bidirectional)
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28
Q

protein-mediated transverse lipid translocation may need…
some proteins are non-specific while other only translocate..

A

energy input (ATP)
specific lipids

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29
Q

3 types of proteins that translocate membrane lipids:

A
  1. P-types flippase: need ATP+ carry out inward movement of lipids+ specific
  2. ABC flippase: need ATP+ carry out outward movement of lipids+ specific
  3. scramblase: no ATP+ bidirectional, non-specific+ Ca2+ dependent
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30
Q

the fluid mosaic model emphazises the…
the bilayer is fluid due to…
it is mosaic because…

A

fluidity of the bulk of lipids allowing random diffusion
lateral mobility of lipids and some proteins
proteins are scattered across it

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31
Q

there is some…organisation in membranes
The concept of membrane….or…which are enriched in…and…
proteins are either exculded or included in the raft regions

A

lateral
domain or rafts
Cholesterol and sphingomyelin

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32
Q

lipid rafts are expected to be different in their…

A

lipid composition, lifetimes and sizes

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33
Q

3 types of membrane proteins are:

A
  1. integral (intrinsic)
  2. Lipid-linked
  3. peripheral (extrinsic)
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34
Q

5 functions of integral membrane proteins:

A
  1. trasnport (move molecules by changing shape)
  2. enzymatic activity (electron transport/ metabolism of phospholipids and sterols)
  3. signal transduction (after ligand/ molecule binding)
  4. Cell-cell interactions (glycoproteins= short-lived cell interaction)
  5. attachment to cytoskeleton or the extracellular matrix
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35
Q

integral proteins can be non-covalently bound to… in cell’s cytoskeleton
this can regulate cell…or stabilise…
they can also bind to extracellular matrix which facilitates…

A

proteins
Shape
protein position in the membrane
cell-cell adhesion

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36
Q

4 examples of integral proteins:

A
  1. Glycophorin A (1st integral protein to be sequenced)
  2. bacterio-rhodopsin (1st integral protein whose structure was determined)
  3. glucose transporter (GLUT)
  4. ion channels
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37
Q

GLUT is found in nealry all cells and is abundant in…
the membrane spanning region is composed of…
glucose binds to…surface site and causes a…
glucose is released at the…side of the membrane into the…

A

cell lining the small intestine
12 a-helicases
outer
confrontational change (of shape)
inner
internal aqueous solution

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38
Q

Bacterio-rhodopsin has….helices with short loops on…
it has…amino acids in an…
it is made of multiple transmembrane…packed in a bundle

A

7 transmembrane
either side of the membrane
20-30
alpha helix
Domains

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39
Q

ion channels do not require…changes unlike…
there is a…variety of channels and they are…
channels can open in response to…(6 things)

A

large confrontational
transporters
wide
selective

ligand binding, electric potential, pH, temperature, pressure, lipids

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40
Q

perioheral membrane proteins bind to…
they interact with…lipid headgroups or…or both
they also interact with…chains

A

surface of the membrane
anionic
charged groups on proteins (ie:integral proteins)
hydrophobic lipid acyl

41
Q

Lipid-linked membrane proteins are…linked to a lipid which is..in the membrane
different proteins use…for attachments

A

covalently
inserted
different lipids

42
Q

2 ways peripheral proteins can bind to the membrane

A
  1. lipid linked
  2. positively charged surfaces (to anionic lipids)
43
Q

often proteins bind to…lipid chain as one is not sufficient for binding
Myristoyl (lipid) groups are connected to…
Palmitoyl (lipid) groups are…linked to…or…

A

more than one
glycine residue
covalently, cystine or serine residues

44
Q

mutations of myristoyl and palmitoyl sides result in…
glycosylphosphatidylinositol (GPI) anchor is a…

A

loss of binding pf pertipheral proteins
Post-translational modification that anchors a modified protein in the outer leaflet of the cell memebrane

45
Q

carbohydrates in the cell membrane are attached to:
they are located in…face of membrane

A
  1. Lipids: glycolipids
  2. Proteins: glycoproteins
    Extracellular
46
Q

glycoproteins are important because they:
2 types of glycoproteins:

A
  • stabalise proteins
  • cell-cell recognition
    1. O-linked (linked to oxygen atom in side chain of serine or threonine)- 2-5 sugars= short
    2. N-linked (linked to amide nitrogen in side chain of asparagine amino acid)- large branched structure as many as 30-40 sugar residues
47
Q

an asparagine residue can accept an…of it is part of an….sequence

A

Oligosaccharide
Asn-X-Ser or Ash-X-Thr (X is any residue)

48
Q

small molecules can cross cell membrane through:

A
  1. passive diffusion (simple or facilitated)
  2. active transport (ATP/ ion driven)
49
Q

Macromolecules can cross cell membrane through:

A
  1. exocytosis (organised/ constitutive/ regulated)
  2. endocytosis (phagocytosis/ Receptor-mediated/ pinocytosis)
50
Q

membranes are..and maintain a…environment
internal organelles often have different….to..

A

selectively permeable
constant internal
different environment to cytosol (ie: lysosomes= pH less than 5)

51
Q

simple diffusion includes diffusion of…

A

Gases and hydrophobic molecules and small polar molecules

52
Q

facilitated diffusion depends on…
the proteins are…and depend on…

A

integral membrane proteins (carriers, permeates, channels, transporters)
specific
temp, pH, saturable, inhibitable

53
Q

2 facilitated diffusion carrier examples:

A
  1. ionophore= ion carrier (produced by bacteria as antibitics against other competing bacteria= to ds=ischarge ion gradient of target cell)
  2. ion channels= rapid and gated passage of anions and cations and highly selective
54
Q

ion channels are essential for:

A
  1. maintaining osmotic balance
  2. signal transduction
  3. nerve impulses
55
Q

2 types of ionophores: (both integral proteins)

A
  1. carrier= ie: valinomycin - specific to K+ ions
  2. Channel-forming= ie: gramicidin A - monocovalent cations ie: Na+ and K+
56
Q

different families of ion channels include:

A
  1. voltage-gated (Ca2+/ Na+/ K+)
  2. Non selective cation channel
  3. Ca2+ activated K+ channels
57
Q

2 specific exaplmes of facilitated diffusion:

A
  1. glucose transporter (GLUT)= into and from blood
  2. Aquaporine= transmembrane protein that filtrate, absorb and secrete fluids
58
Q

3 trypes of integral protein transporters for active transport:

A
  1. uniport= one specific molecule + one direction
  2. symport= 2 molecules in SAME direction (one direction)
  3. antiport= cotransporter ie: Na+/H+ and pH regulation= 2 molecules in 2 directions
59
Q

ATP driven active transport transports against…
and need energy through…

A

Conc or electrochemical gradient
ATP hydrolysis

60
Q

ion driven active transport uses the energy stored in the…
secondary active transporter that transport of a molecule is coupled to the…

A

electrochemical gradient
movement of an ion

61
Q

movement of molecule in ion driven active transport is coupled with…
example of symport:
example of antiport:

A

Na+ or H+ movement
Na+/ glucose transporter
Na+/ Ca2+ exchange

62
Q

exocytosis is:
1. Constitutive:
2. Regulated:

A
  • all cells, secreted proteins and plasma membranes

-specialised cells (neuronal, pancreatic), Ca2+ dependent= ie: in nerve terminal

63
Q

3 types of endocytosis and their examples:

A
  1. phagocytosis= ingestion of large particles (bacteria/ debris) by specialised cells
  2. Pinocytosis= uptake of fluids “cell drinking”
  3. receptor-mediated= cholesterol/ LDL-R
64
Q

phagocytes are found in…
Examples:
steps in engulfing:

A

immune system
Macrophages, neutrophils, dendritic cells
1. pseudopodia (temporary arm-like structure that wraps around the pathogen)
2. pathogen in vacuole + lysosome joins
3. phagolysosome forms
4. antigen presentation

65
Q

receptor-mediated endocytosis is good for contracting…of macromolecules
it is selective and it involves…

A

low levels
Clathrin-coated pits and vesicles

66
Q

steps in receptor-mediated endocytosis:

Example:

A
  1. ligand binds to receptor
  2. coated vesicle forms (ligand and recpeotr together) + endosome joins= fuse together
  3. lysosomes join+ lysosomal degradation occurs
  4. receptors recycled

cholesterol uptake by LDL receptor (can be exploited by viruses to gain entry to cells)

67
Q

how do GLUT transporters work:

A
  1. 3 Na+ out from epithelial cell into blood and 2 K+ in (high Na+/ low K+ in blood)
  2. low Na+ conc inside cell and high K+ inside cell
  3. 2Na+ and glucose from lumen (high Na+) into cell (symporter driven by high extracellular Na+)
  4. glucose uniporter (GLUT2) facilitates glucose transport from cell into blood
68
Q

Aquaporins/ water channel proteins are requied for…
it is called:
it is a…and aabundant in erythrocytes, kidney cells

A

Bulk flow of water actoss cell membranes (singular water molecules dont need it)
28 kDa, 6 transmembrane alpha-helices
Tetramer with 4 pores

69
Q

Na-K-ATPase transporter is…
high K+ and low Na+ in cell=…
it helps:

A

ATP driven
Na+/K+ gradient (maintained by Na+/K+ ATPase)

  1. control cell volume
  2. makes nerve and muscle cells electrically excitable
  3. Facilitates ion-driven active transport if amino acids and sugars
70
Q

Na+/K+ transporter pumps…which…the cell membrane
ATP hysrolysis includes…to pump the ions against their conc gradient
…system: ATP is not hydrolysed unless…

A

3 Na+ out and 2 K+ in
polarises (+ on outside= important for pathogen protection)
confrontational changes
coupled system
Na+ and K+ are transported and vice versa

71
Q

cardiac glycosides/ cardiotonic steroids (are now replaced by…)
they are used in…
they are made of…steroids
the inhibit…which…

A

ACE inhibitors and diuretics
congestive heart failure (heart fails to pump blood around body)
plant
inhibits Na+/K+ ATPase
-increase Na+ conc in cell and decrease it across membrane
-decrease Ca2+-Na+ exchange
-increase Ca2+ conc in cell
-enhance strength of contraction of heart muscle

72
Q

oral rehydration therapy is…
it increases…pressure in..cells
it is used in…to treat…

A

a type of fluid replacement used to prevent and treat dehydration
osmotic pressure
epithelial cells
developing countries to treat cholera, diarrhoea etc

73
Q

oral solution given as rehydration therapy contains…
Glucose uptake is dependant on…

A

water, glucose, Na+, k+
Na+ (therefore both are included in the solution)

74
Q

Cholera:
- symptoms
- prevalence
- cause
- treatment

A
  • severe diarrhoea, vomiting
  • 3-5 mill causes a year/ more than 100,000 deaths
  • vibrio cholerae bacteria in contaminated water and food/ virulence factor= cholera toxin
  • oral rehydration (water, salts, glucose)
75
Q

cell signalling is a process of cellular…
it allows cells to:

A

communication
- regulate development and organise into tissues
-control their growth and development
-co-ordinate functions
-respond to their environment

76
Q

most drugs work by targeting…of cell signalling
this is important to understand:

A

one step
-efficacity
-interactions
-specificity (side effects)

77
Q

4 types of extracellular signalling:

A
  1. autocrine: a cell targets itself
  2. Endocrine: a cell tagets a DISTANT cell through circulation/ blood
  3. juxtacrine: cell targets a neighbouring cell via direct contact (ligand, receptor, GAP junction)
  4. Paracrine: a cell targets a neighbouring cell
78
Q

Autocrine signalling is….in most cancer cells because it is involved in signal…
2 types:

A

dysregulated
signal amplification (+ve feedback)/ attenuation (-ve feedback)
Self-stimulation and trans-activation (need another molecule to be added to help activation)

79
Q

example of endocrine signaling (most hormones)….
example of paracrine:
examples of juxtacrine:

A

glycemia (conc of sugar/ glucose in blood)
synapric
antigen presentation and cardiac contraction

80
Q

extracellular signalling cells are…
for example:

A

1st messengers
growth factors, neurotransmitter, hormones (endo/ para), cytokins

81
Q

4 main classes of receptors:

A
  1. Ligand gated ion channel
  2. G-protein coupled receptor (GPCR)
  3. Kinase-linked
  4. Nuclear receptor (inside cell- while the pther three are on membrane)
82
Q

ligand gated recepors are also called:
they open and close…
example:
other examples: GABA, GlyR, 5-HTR

A

ionotropic receptors
very fast= 2mlsec

nicotinic acetylcholine receptor (nAChR)= Na+ in and K+ out = depolarisation
at neuromuscular junction= muscle contraction

83
Q

GPCR is also known as…
it is the largest family of receptors
it is…than ligand linked
it is coupled to….

A

metabotropic (2nd messenger couples) or 7 transmembrane spanning (7TM) receptors
slower
Intracellular G protein (3 subunits)= activated when ligand binds to receptor= bind with GDP

84
Q

examples of GPCR: (variety of stimuli: light/ hormones/ neurotransmitter)

A

adrenoreceptors
(Muscarinic Ach and angiotensin II= other 2 examples)

85
Q

kinase-linked receptors are…receptors
they use…to add…group to substrate
it is a large and heterogenous group, has…transmembrane domain
mostly function as…
Kinase ligand and dimerisation leads to…

A

catalytic
kinase, phosphate
One
dimers
phosphorylation

86
Q

examples of kinase-linked receptors:

A
  1. catalytic (hormones/ GF)= autophosphorylation (insulin receptor)
  2. non-catalytic (cytokines)= IL-2, IL6
87
Q

Nuclear hormone receptors are…receptors
it is a…structure
they regulate…transcription

A

intracellular (in sytosol or nucleus)= ligand activated transcription factors
monomeric (seperate ligand and DNA binding domains)
Gene

88
Q

2 examples of nuclear receptors:

A
  1. Steroid hormones
  2. thyroid hormones
89
Q

signal transduction is when…

A

extracellular signals are converted into intracellular signals

90
Q

example of cell transduction: (adrenaline)

A

terget cell= liver or skeletal muscle
recpetor= beta-adrenergic receptor
Response= break down of energy reserves (glycogen) to glucose

91
Q

steps in cell transduction:

A
  1. 1st messenger (ligand)
  2. bond with GPCR
  3. G protein activated
  4. effector enzyme (adenylyl cyclase)= ATP
  5. 2nd messenger= cAMP
  6. protein kinase A= adds phosphate to protein
  7. terget protein (phosphorylated protein
  8. cellular response
92
Q

2nd messengers are….
they have a…increase in conc after stimulation
they need to be…
some can also be…

A

short-lived signalling
Quick
transient (temporary)
primary messengers depending on hierarchy of events (orderly manner)

93
Q

4 classes of 2nd messengers:

A
  1. cyclic nucleotides (cGMP, cAMP)
  2. membrane lipid derivatives (DAG)
  3. Ca2+
  4. Gas (nitric oxide, CO)
94
Q

circulating molecules conc ned to remain…so receiving cell…the signal

A

low
amplifies
1st messenger-> several activated target protein

95
Q

pathway for signal transduction are…and…

A

specific and complex

96
Q

main types of lipids in the body are:

A
  1. triglycerides
  2. Cholesterol
  3. phospholipids
  4. steroids
97
Q

lipoproteins transport…
they share a…structure but different ratios of…
they are classified according to…

A

insolube cholesterol and triglyceride in blood plasma
General
Protein:lipids
density and chemical properties

98
Q

4 types of lipoproteins

A
  1. chylomicrons (biggest) (VLDL and their catabolic remnants)= produced in intestine
  2. VLDL= produced in liver
  3. LDL=
  4. HDL (smallest)
99
Q
A

IMS 1 (14 decks)

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