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AnaPhy ni Ma'am E > Cell membranes > Flashcards

Cell membranes Flashcards

1
Q

cell membrane disorder

A

 Familial hypercholesterolemia
 Hereditary Spherocytosis
 Acute Pancreatitis
 Cancer metastasis
 Cystic Fibrosis

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2
Q

characteristics of cell membrane

A
  • asymmetric
  • viscous and plastic
  • dynamic
  • thermodynamically stable and metabolically active
  • noncovalent assemblies
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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

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4
Q

 Presence of villi, gap junctions, tight junction
- properties that have proteins and do not have proteins

A

regional asymmetry

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5
Q
  • marker to recognize
  • outer part of cell membrane
A

oligosaccharide

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6
Q

highly concentrated location where proteins are located

A

lipid rafts

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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

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8
Q

the two major body compartments

A

intracellular and extracellular fluid compartments

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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

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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

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11
Q

what are the composition of cell membrane?

A

lipids, proteins, carbohydrates

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12
Q

provides the basic structures of
biological membranes

A

lipids

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13
Q

perform most of the membrane’s
specific tasks

A

proteins

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14
Q

major membrane lipids

A

phospholipids, glycosphingolipids, sterols

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15
Q

glycerol backbone, 2 fatty acids in ester and phosphorylated alcohol (ethanolamine, choline, serine, glycerol or inositol)

A

phosphoglycerides

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16
Q

fatty acid attached by an amide link to amino acid of sphingosine

A

ceramide

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17
Q

it has sphingosine backbone
-  Hydroxyl group of sphingosine is esterified
to phosphorylcholine
- it is prominent in myelin sheath

A

sphingomyelin

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18
Q

what are the two parts of glycosphingolipids?

A

cerebrosides and gangliosides

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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

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20
Q

Simplest phosphoglyceride is ____________

A

phosphatidic acid

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21
Q
  • Sugar-containing lipids built on a backbone of ceramide
     Include the cerebrosides (galactosyl- and
    glucosylceramide) and the gangliosides
A

glycosphingolipids

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22
Q

functions of membrane proteins

A

 Enzymes
 Pumps, channels, carriers
 Antigens
 Receptors
 structural proteins

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23
Q

2 types of membrane proteins

A

Integral and peripheral proteins

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24
Q

 Interact extensively with
phospholipids
 Require detergents for solubilization
 Are amphipathic, globular and spans
the bilayer

A

integral proteins

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25
Q

 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

A

Peripheral proteins

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26
Q

 occur in association with lipids or proteins :
glycolipids or glycoproteins
 mostly found on the external membrane surface

A

carbohydrates

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27
Q

 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”

A

Fluid mosaic model

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28
Q

who invented the fluid mosaic model?

A

Singer and Nicolson (1972)

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29
Q

factors affecting membrane fluidity

A

Lipid composition, temperature

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30
Q
  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
A

lipid composition

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31
Q

temperature at which structure undergoes transition from ordered to disordered state

A

transition temperature (Tm)

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32
Q

high temperatures = membrane fluidity
_______________
 low temperatures = hydrophobic side
chains become aligned = stiff structure

A

increases

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33
Q

 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

A

micelles

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34
Q

formed micelles assist in the
digestion and absorption of fat

A

bile acids

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35
Q
  • 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
A

liposomes

36
Q
  • 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
A

caveola

37
Q

 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

A

signal transduction

38
Q
A
39
Q

receptors can be found:

A

cell surface and intercellularly (cytoplasm or nucleus)

40
Q

Cell membrane transport systems are very important because :

A
  1. The cell membrane is SELECTIVE
  2. Cell membrane RECEIVES AND TRANSMITS
    SIGNALS from other cells
41
Q

what are the transport system?

A

uniport and cotransport

42
Q

moves ONE TYPE of substance
bidirectionally
1. Ex: Glucose transporters (GLUT)

A

uniport

43
Q

two types of cotransport

A

symport and antiport

44
Q

moves TWO solutes in the SAME
DIRECTION
Ex: SGLT1 and SGLT2

A

symport

45
Q

moves TWO solutes in OPPOSITE
DIRECTIONS
Ex : 3Na+-1Ca++ antiporter

A

antiport

46
Q

factors affecting simple diffusion

A
  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
Q

 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

A

Aquaporins

48
Q

 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”

A

Ion channels

49
Q

what are the two ion channel gating?

A

voltage gating and ligand gating

50
Q

 channels open or close in response to changes in membrane potential

A

voltage gating

51
Q

a specific molecule or chemical binds to a
receptor which opens the channel

A

ligand gating

52
Q

carrier is exposed to high
concentrations of solute

A

pong state

52
Q

carrier is exposed to a lower
concentration of solute

A

ping state

53
Q

factors affecting facilitated diffusion

A
  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
Q
  • 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
A

osmosis

55
Q

 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

A

osmotic pressure

56
Q

 Is a nonselective process
 Uptake of a solute thru small vesicle
formation is proportionate to its
concentration in the ECF
 Is an active process

A

fluid-phase pinocytosis

57
Q

 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

A

receptor- mediated/ absorptive pinocytosis

58
Q

ingest a large volume of their cell
membrane through this process

A

macrophages

59
Q

 located below the apical surface of epithelial
cells
 prevents the diffusion of macromolecules
between them
 composed of proteins occludin, claudins
 sites of paracellular transport

A

tight junctions

60
Q

 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

A

gap junctions

61
Q

3 fates of molecules released thru exocytosis :

A
  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
Q
  • muscular tissue of heart
  • pump deoxygenated and oxygenated blood
A

myocardium

63
Q
  • the difference in potential between the interior and exterior of the cell due to differences in ion concentration
A

membrane potential

64
Q
  • 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)
A

resting membrane potential

65
Q

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

A

potassium equilibrium potential (PEP)

66
Q

Requirements for establishing a RMP

A
  • The relative permeability of the cell membrane
  • presence of gradient
67
Q
  • force needed to cancel out a concentration gradient
  • equal and opposite the force of concentration
A

nernst potential

68
Q
  • describes equilibrium potential for any ion species
  • electrical potential necessary to balance a given ionic concentration gradient
A

nernst equation

69
Q
  • 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
A

action potential

70
Q

a level of stimulation to establish
- potential that would be able to trigger an action potential

A

Threshold potential

71
Q
  • local potential that failed to elicit an action potential
  • it will be reaching first before reaching resting membrane potential
A

Subthreshold potential

72
Q

electrical energy that/ from moving

A

electrical potential

73
Q

membrane is very permeable to Na+

A

depolarization

74
Q

membrane is very permeable to K+

A

repolarization

75
Q

Stages of action potential

A
  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
Q

time period from generating action potential to resting

A

refractory period

77
Q
  • 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
A

absolute refractory period

78
Q
  • 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
A

relative refractory period

79
Q
  • changes in cell’s membrane potential that are restricted or confined to relatively small regions of the plasm membrane
  • travels by short distance
A

graded potential

80
Q

two types of strength of currents

A

Temporal summation and spatial summation

81
Q
  • 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
A

Temporal summation

82
Q
  • several stimuli, even in different spots are applied at the same time
  • also elicits a stronger response
A

spatial summation

83
Q

Types of graded potential

A
  • excitatory postsynaptic potential (EPSP)
  • inhibitory postsynaptic potential (IPSP)
84
Q
  • makes the cell more vulnerable to stimuli
  • it goes near the threshold but not strong enough to achieve it
  • decrease membrane potential
A

excitatory postsynaptic potential (EPSP)

85
Q
  • makes the cell less vulnerable to stimuli
  • due to increased negativity beyond the RMP
A

inhibitory postsynaptic potential (IPSP)

AnaPhy ni Ma'am E (5 decks)

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