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PHGY 209 > 2. Transport Mechanisms > Flashcards

2. Transport Mechanisms Flashcards

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1
Q

Cell membrane less permeable to

A
  • larger molecules
  • charged molecules
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2
Q

Cell membrane highly permeable to

A
  • water
  • lipid soluble substances
  • dissolved gases
  • small uncharged molecules
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3
Q

Cell membrane impermeable to

A

very large molecules

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4
Q

Phospholipid bilayer components (4)

A
  • cholesterol
  • integral proteins
  • peripheral proteins
  • glycocalyx
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5
Q

cholesterol function

A

maintains membrane fluidity

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6
Q

glycocalyx function (2)

A
  • contributes to cell-cell recognition, communication, adhesion and protection
  • helps control vascular permeability
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7
Q

integral proteins

A

transmembrane: cross the the membrane

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8
Q

peripheral proteins

A

mostly on cytoplasmic side

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9
Q

functions of plasma membrane proteins (6)

A
  • selective transport
  • enzymatic activity
  • cell surface receptor
  • cell surface identity marker
  • cell adhesion
  • attachment to cytoskeleton
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10
Q

Passive transport mechanisms (3)

A
  • diffusion
  • facilitated diffusion
  • osmosis
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11
Q

Active transport mechanisms (3)

A
  • primary active transport
  • secondary active transport
  • pino/phagocytosis
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12
Q

Diffusion definition

A

movement of molecules down a concentration gradient

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13
Q

diffusion equilibrium, net flux =

A

net flux = 0

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14
Q

Fick’s Law of Diffusion (formula)

A

J = PA(C0 - Ci)

J = flux
P = permeability constant
A = surface area
C0 - Ci = concentration gradient

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15
Q

factors affecting diffusion (6)

A
  • mass of molecule
  • concentration gradient
  • lipid solubility
  • electrical charge
  • ion channels
  • membrane carriers
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16
Q

Diffusion is effective over long distances, True/False?

A

False

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17
Q

ion channel

A

transmembrane protein that show ion selectivity

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18
Q

electrochemical gradient

A

simultaneous existence of electrical and concentration gradient for a particular ion

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19
Q

gating

A

conformational changes that open/close iron channels

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20
Q

3 gating ways:

A
  • ligand gated = compound binds to channel
  • voltage gated
  • mechanically gated = stress
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21
Q

current flow through ion channels depends on: (3)

A
  • channel conductance
  • channel open time
  • frequency of channel opening
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22
Q

Facilitated diffusion (def)

A

use of carriers to transport molecules down concentration gradient

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23
Q

Is facilitated diffusion active or passive?

A

passive

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24
Q

carrier/transporter is an

A

integral membrane protein

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25
facilitated diffusion affected by: (4)
- solute concentration - affinity of transporter for solute - number of transporters - rate of transporter conformational change
26
3 characteristics of mediated transports
- specificity - saturation - competition
27
Transport maximum (Tm)
when all binding sites on all transporters are occupied
28
steps for facilitated diffusion (4)
- solute binds transporter - transporter changes configuration - solute delivered to other side of membrane - transporter resumes its original configuration
29
active transport
use of carriers to transport molecules against a concentration gradient using ATP
30
primary active transport
- involves hydrolysis of ATP by a carrier - phosphorylation of carrier changes conformation of carrier and its solute binding affinity
31
example of primary active transport
Na+/K+ pump (ATPase): - ATP binds to pump: 3Na+ bind to carrier - phosphorylation: Na+ released outside membrane - 2K+ binds to carrier - dephosphorylation: K+ released inside membrane
32
secondary active transport
uses energy stored of electrochemical gradient to move both Na+ and the transported solute against the solute molecule's concentration gradient
33
secondary active transport: glucose example
1. Na+ binds to transporter outside the cell, allowing glucose to bind to the same carrier 2. change in configuration: transporter delivers Na+ and glucose into cell 3. transporter reverts to its original configuration 4. Na+ removed from cell by ATPase
34
secondary active transport mechanisms (2)
- symport/cotransport - antiport/counterport
35
symport/cotransport
solute transported in same direction as Na+ -> HCO3, amino acid, glucose
36
antiport/counterport/exchange
solute transported in opposite direction to Na+ -> H+, Ca2+
37
endocytosis/exocytosis
active transport mechanisms involving participation of cell membrane itself
38
3 types of endocytosis
- pinocytosis - phagocytosis - receptor-mediated endocytosis
39
endocytosis
cell membrane invaginates and pinches off to form a vesicle
40
pinocytosis - cell drinking
- non-specific and constitutive 1. endocytotic vesicle engulfs extracellular fluid 2. vesicles travel into cytoplasm and fuse with other vesicles
41
phagocytosis - cell eating
- specific and triggered 1. extensions of cell membrane (pseudopodia) fold around a particle to engulf it 2. pseudopodia fuse to form large vesicles that pinch off the membrane 3. created phagosome migrates to and fuses with lysosomes 4. phagosome content destroyed
42
receptor-mediated endocytosis
molecules in extracellular fluid bind with high affinity to specific protein receptors on plasma membrane
43
2 types of receptor-mediated endocytosis
- clathrin-dependent - potocytosis
44
clathrin-dependent receptor-mediated endocytosis (process)
1. ligand binds receptors on cell which undergoes conformational change 2. adaptor proteins link the ligand-receptor to clathrin, leading to aggregation go ligand-bound receptors 3. clathrin-coated pit formed and invaginates to form clathrin-coded vesicle 4. vesicle pinches off, shedding its clathrin coat 5. receptors and clathrin protein recycled back to cell membrane
45
example of clathrin dependent
low density lipoproteins (LDL) --> recognised by PM LDL receptors
46
potocytosis receptor-mediated endocytosis
- process by which molecules are sequestered and transported by tiny vesicles (caveolae) - caveolae are clathrin independent: can deliver contents directly into organelles - implicated in uptake of smaller molecules (lower Mr)
47
exocytosis
process of moving material from inside the cell to outside
48
2 types of exocytosis
- constitutive - regulated
49
constitutive exocytosis
- continual and non-regulated functions: -replace plasma membrane - deliver membrane proteins to cell membrane - getting rid of substances from cell
50
regulated exocytosis
- triggered by extracellular signals and the increase of systolic Ca2+ - secretes hormones, digestive enzymes and neurotransmitters
51
osmosis
net diffusion of water across a semipermeable membrane
52
aquaporins
facilitate osmosis by forming water permeable channels
53
osmotic pressure
pressure required to prevent the movement of water across a semi-permeable membrane
54
osmotic pressure =
difference in hydrostatic pressures of 2 solutions
55
osmotic pressure is proportional to...
the number of particles in solution per unit volume
56
osmolarity (osm)
total solute concentration of a solution
57
1 osm =
1 mol of solute particles = 1 osm/l
58
isosmotic
solutions which have the same osmolarity as normal extracellular solution = 300mOsm
59
hyposmotic
solutions which have an osmolarity < 300mOsm
60
hyperosmotic
solutions which have an osmolarity > 300mOsm
61
non-penetrating
particles unable to cross membrane --> Na+
62
isotonic
solution has concentration of non penetrating solute particles = 300mOsm -> no net shift
63
hypotonic
solution has concentration of non penetrating solute particles < 300mOsm -> water will enter cell: cell swelling
64
hypertonic
solution has concentration of non penetrating solute particles > 300mOsm -> water will leave cell: cell shrinking
65
capillary transport mechanisms (3)
- Diffusion (across membrane or through pores) - Transcytosis - Bulk flow
66
transcytosis
exchangeable proteins are moved across by vesicular transport through endocytosis (to lumen side), then exocytosis (to instertital side)
67
bulk flow
distributes extracellular fluid volume between plasma and ISF -> magnitude is proportional to hydrostatic pressure difference between plasma and ISF
68
Capillary wall allows protein-free plasma to move from capillaries to ISF. True/False?
True

PHGY 209 (8 decks)

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