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Physiology Exam 2 > Membrane Transport & The Membrane Potential > Flashcards

Membrane Transport & The Membrane Potential Flashcards

1
Q

__ of our water is within cells in the intracellular component.

A

2/3 (67%)

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2
Q

__ of our water is within cells in the extracellular component.

A

1/3 (33%)

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3
Q

What is extracellular fluid made of?

A
  • Blood plasma: 20%
  • Tissue fluid (interstitial fluid with extracellular matrix): 4/5
  • Lymph
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4
Q

What is the extracellular matrix made of?

A

Consists of connective tissue (protein fibers collagen and elastin), as well as a gel-like ground substance

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5
Q

What is collagen?

A
  • Connective tissue fiber; about 15 kinds
  • In basal lamina
  • Binds to carbohydrates on plasma membrane, the matrix of connective tissue (proteoglycans and glycoproteins; play a role in cell recognition)
  • Binds ET to CT
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6
Q

What is elastin?

A

Connective tissue fiber that plays a big role in anchoring the cell to extracellular

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7
Q

What is ground substance?

A

Highly functional, complex organization of molecules chemically linked to the extracellular protein fibers of collagen and elastin

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8
Q

What is in the hydrated gel of the ground substance?

A

Contains glycoproteins and proteoglycans, composed primarily of polysaccharides and have a high content of bound water molecules

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9
Q

What are integrins?

A 
A class of glycoproteins that extend from the cytoskeleton within a cell, through its plasma membrane, and into the extracellular matrix, glue between cells and extracellular matrix
-relays signals between these compartments
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10
Q

What is the plasma cell membrane selectively permeable to?

A
  • Generally NOT permeable to proteins and nucleic acids

- SELECTIVELY permeable to ions, nutrients and waste

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11
Q

T or F: The plasma cell membrane is a biological interface between the two compartments.

A

TRUE

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12
Q

What does the plasma membrane contain that allows it to function as the site of chemical reactions?

A
  • Enzymes are located in it
  • Receptors: can bond to molecular signals and function in cell recognition
  • Transporter molecules
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13
Q

What do recognition factors allow for?

A

Cellular adhesion

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14
Q

What is carrier mediated transport?

A

Facilitated diffusion and active transport

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15
Q

What is non-carrier mediated transport?

A

Diffusion, osmosis and bulk flow (pressure gradients)

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16
Q

What is vesicle mediated transport?

A

Exocytosis and endocytosis (pinocytosis/phagocytosis)

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17
Q

What is passive transport?

A

The net movement of molecules and ions across a membrane from higher to lower concentration (down its concentration gradient); does not require metabolic energy

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18
Q

What is active transport?

A

The net movement of molecules and ions across a membrane from the region of lower to the region of higher concentration (against a concentration gradient), USES metabolic energy and involves specific carriers

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19
Q

What is diffusion?

A

Random molecular motion

  • Molecules/ions are in constant state of random motion due to their thermal energy
  • Eliminates a concentration gradient and distributes the molecules uniformly
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20
Q

When does diffusion occur?

A

If there is a concentration difference across the membrane and the membrane is permeable to the diffusing substance

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21
Q

What is the cell membrane permeable to?

A

Non-polar molecules (O2)
Lipid soluble molecules (steroids)
Small polar covalent bonds (CO2)
H2O (small size, lack charge)

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22
Q

What is the cell membrane impermeable to?

A

Large polar molecules (glucose)

Charged inorganic ions (Na+)

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23
Q

What 4 things affect the rate of diffusion?

A

1) Magnitude of concentration gradient - driving force of diffusion
2) Permeability of the membrane - neuronal cell membrane is 20x more permeable to K+ than Na+
3) Temperature - higher temp, faster diffusion rate
4) Surface area of the membrane - microvilli increase surface area (20-30x more)

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24
Q

What is osmosis?

A

Net diffusion of H2O across a selectively permeable membrane (water will always travel from high to low concentration of water/to where there is more solute)

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25
What are the 2 requirements for osmosis to occur?
1) Concentration difference of a solute on the 2 sides of the selectively permeable membrane 2) Membrane must be impermeable to the solute
26
What are osmotically active solutes?
Solutes that cannot pass freely through the membrane (Na+)
27
If you have a selectively permeable membrane between 2 solutes (solute 1 = 180 g/L glucose and solute 2= 360 g/L glucose) at what concentration will equilibrium be reached?
(360 + 180)/2 = 270 g/L glucose
28
For those 2 solutes (180 g/L glucose and 360 g/L), once equilibrium is reached what fraction of the volume will be in solute 1? Solute 2?
M1 V1 = M2 V2 Solute 1 = (M1/M2) = 180/270 = 2/3x Solute 2 = (M1/M2) = 360/270 = 4/3x
29
What is osmotic pressure?
Force required to stop osmosis | -Indicates how strongly the solution "draws" H20 into it by osmosis
30
What is osmolality?
The concentration of a solution expressed as the total number of solute particles per kilogram
31
What is molarity?
The number of moles per liter of solution
32
What is molality?
The number of moles of solute per kilogram of solvent
33
What is the plasma osmolality?
300 mOsm/L
34
What is the effect of ionization on osmotic pressure?
NaCl ionized when dissolved in H2O forms 1 mole of Na+ and 1 mole of Cl- ; thus has a concentration of 2 Osm
35
What is the osmolality of a 0.9% NaCl solution?
0.9 g NaCl/100 mL = 9 g/1000 mL = 9 g/1 L = 9 g/1 kg mol = mass/GFM = 9 g/58.5 g/mol = 0.154 mol (1000) = 154 mmol m = moles/kg = 0.154 mol/1 kg = 154 mmol --> dissociates into 154 mmol and 154 mmol --> 308 osmosm total
36
What is the osmolality of a 5% glucose solution?
5 g/100 mL = 50 g/1000 mL = 50 g/1 kg mol = mass/GFM = 50 g/180 g/mol = 0.28 mol = 280 mmol 0.28 moles/1 kg = 280 Osm total (glucose does not dissociate in H20)
37
What is tonicity?
The effect of a solution on the osmotic movement of H2O
38
What is isotonic?
Equal tension to plasma | -RBCs will NOT gain or lose H2O
39
What is hypotonic?
Osmotically active solutes in a lower osmolality and osmotic pressure than plasma -RBC will hemolyse (cell grows)
40
What is hypertonic?
Osmotically active solutes in a higher osmolality and osmotic pressure than plasma -RBC will crenate (cell shrinks)
41
How is plasma osmolality maintained?
Osmoreceptors stimulate hypothalamus -> ADH release and thirst is increased
42
What happens if a person is dehydrated?
The blood volume decreases meaning the plasma osmolality increases --> this is detected by the hypothalamus --> sends signals to posterior pituitary to secrete ADH (that goes to the kidneys and increases water retention) and sends signals to increase thirst (that increases water intake)
43
What is carrier-mediated transport?
Transport across cell membrane by protein carriers
44
What are some characteristics of protein carriers?
- Specificity: interact with specific molecule only - Competition: molecules with similar chemical structures compete for carrier site - Saturation: carrier sites filled
45
What is transport maximum (Tm)? How does competition affect it?
At Tm carriers have become saturated (zero order kinetics); if molecules X and Y compete for the same carrier Tm is lowered
46
Why would glucose show up in the urine?
Tm has been reached
47
What is facilitated diffusion?
Passive transport (ATP not needed); powered by the thermal energy of the diffusing molecules and involves net transport from the side of higher to the side of lower concentration
48
What is active transport?
Requires ATP; movement of molecules and ions against their concentration gradients (low -> high) -2 types: primary and secondary
49
What is primary active transport?
ATP directly required for the function of the carriers - Molecule or ion binds to carrier site - Binding stimulates phosphorylation (breakdown of ATP) - Conformational change moves molecule to other side of membrane
50
What is the Na+/K+ ATP-ase pump?
Carrier protein that is also an ATP enzyme that converts ATP to ADP and Pi -2 K+ in and 3 Na+ out
51
What 7 steps happen in the Na+/K+ ATP-ase pump?
1) 3 Na+ ions and ATP bind to carrier protein 2) ATP breaks into ADP and Pi and releases energy 3) Carrier protein changes shape and Na+ are transported across membrane 4) Na+ diffuse away from carrier protein 5) 2 K+ ions bind to carrier protein 6) Phosphate is released 7) Carrier protein changes shape, transporting K+ across cell membrane and K+ diffuse away from carrier protein. The carrier protein can again bind to Na+ and ATP
52
What is secondary active transport?
Coupled transport, does not require ATP directly ; energy needed for uphill movement obtained from downhill transport of Na+
53
What is cotransport (symport)?
Secondary active transport; molecule or ion moving in the same direction
54
What is countertransport (antiport)?
Secondary active transport; molecule or ion is moved in the opposite direction
55
What is SGLT?
Sodium Glucose Lag Transporter (co-transport) - sodium goes from high -> low - glucose goes from low -> high
56
Glucose transport is an example of what type of transport?
Co-transport, primary active transport and facilitated diffusion
57
What is bulk transport?
Many large molecules are moved at the same time | -exocytosis and endocytosis
58
What is the membrane potential?
- Proteins and phosphates are negatively charged at normal cellular pH - These anions attract positively charged cations that can diffuse through the membrane pores - Membrane more permeable to K+ than Na+ - Na+/K+ ATP-ase pump 3 Na+ out for 2 K+ in - All contribute to unequal charge across the membrane
59
What effect do the fixed anions have on the distribution of cations?
Membrane is negatively charged inside --> attraction for positive ions --> creates an electrochemical gradient (electrical attraction and certain amount of build up of ions) -The Na+/K+ pumps help facilitate the electrochemical gradient
60
What is the equilibrium potential?
Theoretical voltage produced across the membrane if only 1 ion could diffuse through the membrane
61
What is the potential difference?
Magnitude of difference in charge on the 2 sides of the membrane -potential difference of -90 mV if K+ were the only diffusible ion
62
What is the NERST equation?
Membrane potential that would exactly balance the diffusion gradient and prevent the net movement of a particular ion - Equilibrium potential for K+ = -90 mV - Equilibrium potential for Na+ = +65 mV
63
Calculate the NERST equation for K+
Electron motive force = E = -nRT log (Ci/Co) E = -61 log (155/5) E = -90 mV
64
Calculate the NERST equation for Na+
``` E = -61 log (10/145) E = + 65 mV ```
65
What is the resting membrane potential?
The resting membrane potential is less than Ek because some Na+ can also enter the cell --> the slow rate of Na+ efflux is accompanied by slow rate of K+ influx = -65 mV

Physiology Exam 2 (4 decks)

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