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Physiology > Lecture 9 Membrane Transport > Flashcards

Lecture 9 Membrane Transport Flashcards

1
Q

Permeability

A

ability of a substance to pass through a membrane

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2
Q

What is permeability determined by?

A

the phospholipid bilayer

membrane transport proteins

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3
Q

Molecular size

A

smaller molecules are more permeable

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4
Q

Lipid solubility

A

non-polar molecules are lipid soluble meaning they are more permeable (ex: fatty acids)

polar molecules and ions are less permeable or impermeable (ex: H2O)

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5
Q

Membrane transport proteins

A

help ions and molar molecules to pass through

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6
Q

Highly permeable

A

02 & C02
Fatty acids
steroids
H20 (variable: pores)

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7
Q

less permeable

A

Na+, K+, Cl- (via channels)

glucose, a.a’s (via carriers)

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8
Q

Impermeable

A

proteins (except via vesicles)
ATP
DNA, RNA

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9
Q

Passive Transport

A

does not require energy
substances move down gradient
Simple diffusion, osmosis, diffusion through channels, facilitated diffusion

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10
Q

Active Transport

A

requires energy
transport against gradient
primary active transport, secondary active transport, transport via vesicles (endocytosis, exocytosis)

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11
Q

Protein mediated transport

A

diffusion through channels, facilitated diffusion, primary active transport, secondary active transport

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12
Q

Simple Diffusion

A

results from random molecular motion
net movement from high concentration to low concentration
Fick’s Law of diffusion

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13
Q

Fick’s Law of diffusion

A

gives the rate of diffusion
Rate=P A (Cout-Cin) / X
rate is proportional to permeability (P), surface area (A), concentration gradient (Cout-Cin)
inversely proportional to diffusion distance or membrane thickness (x)

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14
Q

Osmosis

A

passive movement of water across a membrane due to solute concentration difference
permeable to H20 but impermeable to solutes
primary mechanism for H20 transport across membranes
H20 ,moves from dilute to concentrated solution (solutes suck water)

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15
Q

Osmolarity

A

total concentration of all solutes in a solution
1 Osm = 1 mole of solutes per liter

Non-ionic solutes and salts

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16
Q

Non-ionic solutes

A

osmolarity = concentration

e.g. 1 M glucose = 1 Osm = 1,000 mOsm

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17
Q

Salts

A

ionize in H20

1M NaCl -> 1M Na+ + 1M Cl- = 2 Osm

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18
Q

Osmotic pressure

A

driving force for osmosis
depends on difference in total solute concentration
negative pressure pills water from dilute to concentrated solution

19
Q

Tonicity

A

effect of an extracellular solution on cell volume, due to H20 movement by osmosis

20
Q

Hypertonic
Hypotonic
Isotonic

A

hypo - H20 moves in cell expands
hyper - H20 moves out cell shrinks
Iso- no net movement of H20 cell volume stays constant

21
Q

Diffusion through Channels

A

Ion channels are protein passageways for ions through the membrane
most channels are selective for certain ions
ions diffuse down electrochemical gradients
channels may be ungated or gated

22
Q

Aquaporins

A

water channels found in most cell membranes

23
Q

Electrochemical gradient

A

combination of concentration and electrical gradients
can act in same direction ( Na+)
or in opposite direction (K+)

24
Q

Facilitated Diffusion

A

carrier proteins mediate diffusion of certain polar molecules across the membrane
down concentration gradient, no energy required
each carrier is specific to particular molecules
saturation- rate limited by number of carrier proteins in the membrane

25
Q

GLUT proteins

A

Facilitated Diffusion

family of glucose transporters, present in many call membranes
most body cells take up glucose by FD using GLUT proteins

26
Q

GLUT4

A

activated by insulin
is the insulin dependent glucose carrier of skeletal muscle, adipose tissue, liver, and connective tissue
Insulin promotes insertion of GLUT4 into the membrane -> glucose uptake via FD

27
Q

Primary Active Transport

A

pumps are transport proteins that use energy from ATP directly
transport ions “uphill” against electrochemical gradients

28
Q

Na+/K+ Pump

A

Transports Na+ OUT and K+ IN
maintains ionic composition of ICF and ECF
K+ and Na+ gradients are the basis of electrical properties of cells
Na+ gradient provides potential energy for transport of other molecules
Na+/K+ pump activity is stimulated by THYROID hormones

29
Q

Other active transport pumps

A

Ca2+ -ATPase in muscles

H+ - ATPase in stomach

30
Q

Secondary Active transport

A

uses potential energy stored in IONIC gradients to move other molecules
transport protein couples “downhill” flow of an ion to uphill transport of another molecule

31
Q

Cotransport

A

SAT

movement of both molecules in the same direction

32
Q

countertransport

A

SAT

movement in opposite directions

33
Q

SGLT

A

SAT
is a Na+-glucose cotransporter in the small intestine and kidney epithelium
moves glucose against its gradient from the lumen into the epithelial cell
uses energy contained in the Na+ gradient

34
Q

Endocytosis

A

phagocytosis

pinocytosis

35
Q

Exocytosis

A

secretion of products out of the cell (mucus, neurotransmitters, hormones)
also functions for insertion of molecules into the plasma membrane (lipids, proteins)

36
Q

Epithelial Transport

A

From lumen to ICF to ECF

37
Q

Apical membrane

A

faces lumen

microvilli increase surface area (ficks law)

38
Q

Basolateral membrane

A

faces ECF, attached to basement membrane

contains Na+/K+ pumps

39
Q

Tight Junctions

A

join epithelial cells, near apical surface, prevent fluid leakage between cells

40
Q

Transepithelial Transport

A

NaCl, glucose and H20 in the small intestines and kidneys

41
Q

NaCl

transepithelial transport

A

apical membrane: Na+ enters via diffusion through channels
basolateral membrane: primary active transport (Na+/K+ pump) moves Na+ out to ECF
Cl- follows Na+ passively by diffusion through channels

42
Q

Glucose

transepithelial transport

A

apical membrane: secondary active transport - cotransport with Na+ (SGLT)
basolateral membrane: faciliated diffusion of glucose out to ECF (GLUT)

43
Q

Water

Transepithelial transport

A

moves by osmosis across apical and basolateral membranes; follows solute movement
pumping of Na+ to ECF between cells promotes H20 movement by osmosis

Physiology (33 decks)

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