Cell membranes Flashcards
(86 cards)
1
Q
cell membrane disorder
A
Familial hypercholesterolemia
Hereditary Spherocytosis
Acute Pancreatitis
Cancer metastasis
Cystic Fibrosis
2
Q
characteristics of cell membrane
A
- asymmetric
- viscous and plastic
- dynamic
- thermodynamically stable and metabolically active
- noncovalent assemblies
3
Q
Irregular distribution of proteins
External location of carbohydrates
Specific enzymes exhibit specificity of location
Phospholipids (choline containing are external while amino acid containing are in the inner leaflet)*
A
inside-out asymmetry
4
Q
Presence of villi, gap junctions, tight junction
- properties that have proteins and do not have proteins
A
regional asymmetry
5
Q
- marker to recognize
- outer part of cell membrane
A
oligosaccharide
6
Q
highly concentrated location where proteins are located
A
lipid rafts
7
Q
functions of cell membranes
A
Permits cell individuality
Has selective permeability
Important for cell to cell interaction and
adhesion
Important in transmembrane signaling
Form specialized compartments ie., for
organelles
Localize enzymes
Integral elements in excitation-response
coupling
8
Q
the two major body compartments
A
intracellular and extracellular fluid compartments
9
Q
Contains 2/3 of body water
Provides environment for the cell to :
Synthesize, store and utilize
energy
Repair itself
Replicate
Perform special functions
A
Intracellular fluid compartments
10
Q
Contains 1/3 of total body water
distributed between PLASMA and
INTERSTITIAL FLUID compartments
Is a delivery system of nutrients, ions,
oxygen and hormones to cells
Removes waste products from the cells
A
extracellular fluid compartments
11
Q
what are the composition of cell membrane?
A
lipids, proteins, carbohydrates
12
Q
provides the basic structures of
biological membranes
A
lipids
13
Q
perform most of the membrane’s
specific tasks
A
proteins
14
Q
major membrane lipids
A
phospholipids, glycosphingolipids, sterols
15
Q
glycerol backbone, 2 fatty acids in ester and phosphorylated alcohol (ethanolamine, choline, serine, glycerol or inositol)
A
phosphoglycerides
16
Q
fatty acid attached by an amide link to amino acid of sphingosine
A
ceramide
17
Q
it has sphingosine backbone
- Hydroxyl group of sphingosine is esterified
to phosphorylcholine
- it is prominent in myelin sheath
A
sphingomyelin
18
Q
what are the two parts of glycosphingolipids?
A
cerebrosides and gangliosides
19
Q
- most common sterol in membranes
- intercalates among phospholipids in the cell
membrane
Is also amphipathic with its hydroxyl group lying at the aqueous surface
“moderator molecule”
A
cholesterol
20
Q
Simplest phosphoglyceride is ____________
A
phosphatidic acid
21
Q
- Sugar-containing lipids built on a backbone of ceramide
Include the cerebrosides (galactosyl- and
glucosylceramide) and the gangliosides
A
glycosphingolipids
22
Q
functions of membrane proteins
A
Enzymes
Pumps, channels, carriers
Antigens
Receptors
structural proteins
23
Q
2 types of membrane proteins
A
Integral and peripheral proteins
24
Q
Interact extensively with
phospholipids
Require detergents for solubilization
Are amphipathic, globular and spans
the bilayer
A
integral proteins
25
Do not interact directly with
phospholipids
Weakly bound to hydrophilic
regions of integral proteins on one
side of the membrane
Ex : RBC cystoskeletal proteins
Ankyrin is bound to integral protein
Band 3 Spectrin is in turn bound to
Ankyrin
Peripheral proteins
26
occur in association with lipids or proteins :
glycolipids or glycoproteins
mostly found on the external membrane surface
carbohydrates
27
universally accepted description of membrane structure
“icebergs” (proteins) floating in a “sea” of
phospholipids
membranes undergo phasic changes from stiff (gel or crystalline) to fluid state
both lipids and proteins undergo "rapid
redistribution" in the plane of the membrane
"lateral diffusion"
Fluid mosaic model
28
who invented the fluid mosaic model?
Singer and Nicolson (1972)
29
factors affecting membrane fluidity
Lipid composition, temperature
30
1. longer and more saturated fatty acid chains
exhibit higher transition temperature
2. unsaturated cis bonds tend to increase
membrane fluidity
3. presence of cholesterol the moderator molecule
lipid composition
31
temperature at which structure undergoes transition from ordered to disordered state
transition temperature (Tm)
32
high temperatures = membrane fluidity
_______________
low temperatures = hydrophobic side
chains become aligned = stiff structure
increases
33
small aggregates of amphipathic
molecules forming a monolayer with :
hydrophobic regions
hydrophilic regions
arrangement of different regions depends
on the chemical environment where the
micelle is situated
micelles
34
formed micelles assist in the
digestion and absorption of fat
bile acids
35
- artificial membranes
- are vesicles surrounded by a lipid bilayer
consists of phospholipids that are of natural or synthetic origin
lipid content can be varied allowing for
examination of varying lipid composition
on certain functions (ie., transport)
in the study of factors that affect protein
and enzyme function
may be used for specific drug delivery
and gene therapy
liposomes
36
- areas of the exoplasmic leaflet of the lipid bilayer enriched in cholesterol, sphingolipids and proteins
- clusters elements of the signal transduction
pathways and enhances their activity
caveola
37
biochemical signals from hormones,
neurotransmitters bind to receptors in the cell
membrane
transmits information to the cytoplasm via these membranes through the generation of signaling molecules : cyclic nucleotides, calcium, diacylglycerol and phosphoinositides
signal transduction
38
39
receptors can be found:
cell surface and intercellularly (cytoplasm or nucleus)
40
Cell membrane transport systems are very important because :
1. The cell membrane is SELECTIVE
2. Cell membrane RECEIVES AND TRANSMITS
SIGNALS from other cells
41
what are the transport system?
uniport and cotransport
42
moves ONE TYPE of substance
bidirectionally
1. Ex: Glucose transporters (GLUT)
uniport
43
two types of cotransport
symport and antiport
44
moves TWO solutes in the SAME
DIRECTION
Ex: SGLT1 and SGLT2
symport
45
moves TWO solutes in OPPOSITE
DIRECTIONS
Ex : 3Na+-1Ca++ antiporter
antiport
46
factors affecting simple diffusion
1. concentration gradient across membrane
2. electrical potential across membrane
3. permeability coefficient of the substance to the membrane, lipid solubility
4. pressure difference across membrane
5. thickness of membrane
6. temperature
7. distance
8. number of channels
47
water channels found in certain cells : RBC, distal tubules and collecting ducts of renal nephrons
are tetrameric membrane proteins
5 distinct aquaporins : AP-1 to AP-5
mutation in AP-2 causes Diabetes Insipidus
Aquaporins
48
are for water soluble substances /ions
permeability depends upon size, extent of
hydration and charge density of the ion
specific channels for each ion
activity of some channels are regulated by
neurotransmitters or can be..
“gated”
Ion channels
49
what are the two ion channel gating?
voltage gating and ligand gating
50
channels open or close in response to changes in membrane potential
voltage gating
51
a specific molecule or chemical binds to a
receptor which opens the channel
ligand gating
52
carrier is exposed to high
concentrations of solute
pong state
52
carrier is exposed to a lower
concentration of solute
ping state
53
factors affecting facilitated diffusion
1. concentration gradient across membrane
2. amount of carrier available *
3. rapidity of solute-carrier interaction
4. rapidity of conformational change for both the loaded and unloaded carrier
5. presence of certain hormones : Insulin, GH and glucocorticoids
54
- Is the net flow of solvent across a
semipermeable membrane from an area of
LOWER SOLUTE CONCENTRATION to an area of HIGHER SOLUTE CONCENTRATION
is due to a semipermeable membrane that only allows the solvent to pass
affected by osmotic pressure
osmosis
55
Is the minimum pressure required to negate or reverse osmosis.
force or pressure is applied on the side of the membrane with higher solute concentration to push the solvent back to the area with low solute concentration
osmotic pressure
56
Is a nonselective process
Uptake of a solute thru small vesicle
formation is proportionate to its
concentration in the ECF
Is an active process
fluid-phase pinocytosis
57
is a receptor-mediated selective process for the uptake of macromolecules
high affinity receptors permit selective
concentration of ligands from the medium
involves CLATHRIN-coated pits
Ex : LDL receptors
may be a mechanism through which certain
viruses enter the cell
receptor- mediated/ absorptive pinocytosis
58
ingest a large volume of their cell
membrane through this process
macrophages
59
located below the apical surface of epithelial
cells
prevents the diffusion of macromolecules
between them
composed of proteins occludin, claudins
sites of paracellular transport
tight junctions
60
are low resistance connections between cells
functional unit of the gap junction is the
connexon
Aligned connexons of 2 adjacent cells form a
channel
allow for the movement of ions and small
molecules between cells
Couples adjacent cells electrically
gap junctions
61
3 fates of molecules released thru exocytosis :
1. attach to cell surface to become peripheral
proteins (Ex: antigens)
2. may become part of extracellular matrix
(Collagen, GAGs)
3. may enter ECF and signal other cells
(hormones)
62
- muscular tissue of heart
- pump deoxygenated and oxygenated blood
myocardium
63
- the difference in potential between the interior and exterior of the cell due to differences in ion concentration
membrane potential
64
- steady transmembrane potential of a cell that is not producing an electrical signal
- magnitude of the force that occurs when cells are not excited or not in the process of transferring information to other cells (resting phase)
resting membrane potential
65
K+ has the ability to dictate the predominant charge in the cell when at rest, unlike Na+
- the resting potential of the cell hold steady unless there are changes in electric current around the cell
potassium equilibrium potential (PEP)
66
Requirements for establishing a RMP
- The relative permeability of the cell membrane
- presence of gradient
67
- force needed to cancel out a concentration gradient
- equal and opposite the force of concentration
nernst potential
68
- describes equilibrium potential for any ion species
- electrical potential necessary to balance a given ionic concentration gradient
nernst equation
69
- when you reach cell membrane's threshold
- long distances can travel
- can maintain its size and shape as it moves down the axon
- all or none response
action potential
70
a level of stimulation to establish
- potential that would be able to trigger an action potential
Threshold potential
71
- local potential that failed to elicit an action potential
- it will be reaching first before reaching resting membrane potential
Subthreshold potential
72
electrical energy that/ from moving
electrical potential
73
membrane is very permeable to Na+
depolarization
74
membrane is very permeable to K+
repolarization
75
Stages of action potential
1. Na+ channels open and there is massive influx of Na+ into the cell (depolarization)
2. Na+ further depolarizes the cell, opens up more Na+ channels
3. increase in K+ and decrease Na+ concentration (repolarization)
4. Resting membrane potential is restored upon the closing of Na+ and K+ channels
76
time period from generating action potential to resting
refractory period
77
- cell cannot be excited regardless of strength of the stimulus
- occurs due to the active state of the inactivation gates
- how fast cell can process information
absolute refractory period
78
- an action potential can still be generated
- not all Na+ channels participated in the previous action potential
- some channels that recovered can be activated by stronger stimulus
relative refractory period
79
- changes in cell's membrane potential that are restricted or confined to relatively small regions of the plasm membrane
- travels by short distance
graded potential
80
two types of strength of currents
Temporal summation and spatial summation
81
- several stimuli applied at different time intervals are added up
- stimulus is added before resting
- additive which results in a stronger response and increased frequency stimuli
Temporal summation
82
- several stimuli, even in different spots are applied at the same time
- also elicits a stronger response
spatial summation
83
Types of graded potential
- excitatory postsynaptic potential (EPSP)
- inhibitory postsynaptic potential (IPSP)
84
- makes the cell more vulnerable to stimuli
- it goes near the threshold but not strong enough to achieve it
- decrease membrane potential
excitatory postsynaptic potential (EPSP)
85
- makes the cell less vulnerable to stimuli
- due to increased negativity beyond the RMP
inhibitory postsynaptic potential (IPSP)
