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630: Medical Physiology > Cellular Physiology (Part 1) > Flashcards

Cellular Physiology (Part 1) Flashcards

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USMLE® Step 1 flashcards
1
Q

Total body water accounts for how much of total body weight?

A

50-70%

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2
Q

Low body fat = ___ total body water

High body fat = ___ total body water

A

high

low

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3
Q

Do males or females tend to have less body water and why?

A

Females, because they have a higher percentage of adipose tissue

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4
Q

Total body water is distributed between what 2 major body fluid compartments?

A

intracellular fluid and extracellular fluid

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5
Q

ICF is contained within the cells and constitutes how much of total body water?

A

2/3

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6
Q

ECF is outside the cells and constitutes how much of total body water?

A

1/3

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7
Q

The ECF is further divided into what 2 compartments?

A
  • plasma

- interstitial fluid

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8
Q

What is plasma?

A

the fluid circulating in the blood vessels

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9
Q

What is interstitial fluid?

A

the fluid that actually bathes the cells

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10
Q

Which constitutes a larger percentage of the ECF, plasma or interstitial fluid?

A

the interstitial fluid

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11
Q

What separates the ICF and ECF?

What separates the plasma and interstitial fluid?

A

cell membrane

capillary wall

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12
Q

What is the major difference between the plasma and interstitial fluid?

A

Because the capillary wall is impermeable to large molecules, the interstitial fluid does not contain any proteins, whereas the plasma does

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13
Q

One mole is 6 x 10 ^__ molecules of a substance

A

23

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14
Q

Amounts of a solute are expressed in what?

Concentrations of solutes are expressed in what?

A

moles, equivalents, or osmoles

moles per liter, equivalents per liter, or osmoles per liter (in biological solutions use milli-)

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15
Q

An equivalent is used to describe the amount of what?

A

charged (ionized) solute

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16
Q

one millimole is 1/___ moles

A

1000

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17
Q

What is an osmole?

A

The number of particles into which a solute dissociates in solution

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18
Q

How do you calculate an equivalent?

A

multiply the number of moles of the solute by its valence (number of electrons an ion can attach to)

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19
Q

What is osmolality?

A

The concentration of particles in solution expressed as osmoles per kilogram

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20
Q

What is osmolarity?

A

The concentration of particles in solution expressed as osmoles per liter

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21
Q

If a solute dissociates into more than one particle in solution, then its osmolarity equals what?

A

the molarity multiplied by the number of particles in solution

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22
Q

If a solute does not dissociate in solution then its osmolarity is equal to what?

A

its molarity

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23
Q

As the concentration of H+ increases, then pH _____, and as the concentration of H+ decreases, pH _____.

A

decreases

increases

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24
Q

pH is used to express the concentration of what ion?

A

hydrogen (H+)

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25
Q

What is the principle of macroscopic electroneutrality?

A

each compartment must have the same concentration of positive and negative charges

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26
Q

What is normal body pH?

A

7.4

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27
Q

What is the major cation and 2 balancing anions in the ECF?

A

cation: sodium (Na+)
anions: chloride (Cl-) and bicarbonate (HCO3-)

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28
Q

Cations are ____ charged

Anions are _____ charges

A

positively

negatively

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29
Q

Is the ICF or ECF more acidic (lower pH)?

A

ICF

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30
Q

What are the 2 major cations and 2 balancing anions in the ICF?

A

cations: potassium (K+) and magnesium (Mg+)
anions: proteins and organic phosphates

31
Q

Why are there more positive ions in the plasma, rather than in the interstitial fluid?

A

To accommodate for the negative charge of the proteins

32
Q

Even though there is remarkable differences in individual solute concentrations, the osmolarity is the same in ICF and ECF, why?

A

Because water flows freely across the cell membranes any differences in osmolarity that occur between the two are quickly dissipated

33
Q

cell membranes are composed of what 2 things?

A

lipids and proteins

34
Q

Describe the structure of the phospholipid component of cell membranes

A

Phospholipids consist of a hydrophilic glycerol backbone that line up against the water and a hydrophobic fatty acid chain that point inwards towards one another. This creates a lipid bilayer

35
Q

What are the 2 types of proteins in the cell membrane? Describe the difference between the two.

A
  • integral proteins span the whole cell membrane and are bound strongly to it
  • peripheral proteins are attached by way of simple bonds and are easily disrupted from the cell membrane
36
Q

Describe downhill transport

A

Substances are transported down an electrochemical gradient by way of diffusion and requires no input of metabolic energy

37
Q

Describe uphill transport

A

Substances are transported against an electrochemical gradient by way of active transport which requires an input of metabolic energy

38
Q

What are the 3 features of carrier-mediated transport?

A
  • Saturation
  • Stereospecificity
  • Competition
39
Q

Describe how saturation plays a role in carrier-mediated transport

A

Because carrier proteins have a limited number of binding sites for a solute, at low concentrations many binding sites are available, and the rate of transport increases steeply as the concentration increases. But at high solute concentrations, the available binding sites become scarce and the rate of transport levels off.

40
Q

What is the point called when all of the binding sites are occupied (saturated)?

A

transport maximum (Tm)

41
Q

Describe the concept of stereospecificity for carrier-mediated transport

A

The binding sites for solutes on the transport proteins are specific to certain isomers

42
Q

Describe the concept of competition of carrier-mediated binding sites

A

Although he binding sites for transported solutes are quite specific, they may recognize, bind, and even transport chemically related solutes which makes them unavailable

43
Q

Simple diffusion occurs as a result of what?

A

the random thermal movement of molecules

44
Q

Net diffusion or flow depends of what 5 things?

A
  • Size of the concentration gradient
  • Surface area available for diffusion
  • Thickness of the membrane
  • Partition coefficient
  • Diffusion coefficient
45
Q

In reference to the concentration gradient, surface area, and membrane thickness, what will increase the rate of diffusion?

A

The higher the concentration gradient, the greater the net diffusion
The greater the surface area the higher the rate of diffusion
The thinner the cell membrane, the higher the rate of diffusion

46
Q

How is facilitated diffusion similar to simple diffusion and carrier-mediated transport?

A

Same as simple diffusion in that it does not require the input of metabolic energy.
Same as carrier-mediated transport in that it uses a membrane carrier and exhibits saturation, stereospecificity, and competition.

47
Q

Which is faster simple or facilitated diffusion? Explain why.

A

Facilitated is faster at levels of low concentration because of the function of the carrier.
Simple diffusion is faster at levels of high concentration because the carriers are saturated which slows down facilitated diffusion whereas simple will proceed as long as there a concentration gradient

48
Q

In primary active transport, solutes are moved from an area of ___ concentration to an area of ___ concentration. Therefore, is energy required?

A

low
high

Yes, metabolic energy in the form of ATP must be provided

49
Q

What is an example of primary active transport system present in all cell membranes?

A

Na+ - K+ ATPase (Na+ - K+ pump)

50
Q

What ions are pumped into and out of the cell by way of the sodium-potassium pump?

A

3 Na+ ions are pumped out and 2 K+ ions are pumped in

51
Q

Because more positive charge is pumped out of the cell than is pumped in, the process of primary active transport by means of the sodium-potassium pump is called what?

A

electrogenic

52
Q

What are the 2 states in which the sodium-potassium pump exist?

A

In the E1 state and in the E2 state

53
Q

In the E1 state the binding sites of Na+ and L+ face the ___cellular fluid and the enzyme has a high affinity for ___.

A

intracellular

sodium

54
Q

In the E2 state the binding sites of Na+ and L+ face the ___cellular fluid and the enzyme has a high affinity for ___.

A

extracellular

potassium

55
Q

What is the difference between primary and secondary active transport?

A

In primary the transportation of one solute is through the direct use of ATP. In secondary the transport of two or more solutes is through an indirect use o ATP

56
Q

Describe how secondary active transport indirectly uses ATP as fuel

A

One of the solutes (usually Na+) moves downhill and the other solute moves uphill. The downhill movement of Na+ indirectly provides ATP for the uphill movement of the other solute

57
Q

What are the 2 types of secondary active transport?

A
  • cotransport

- countertransport

58
Q

Describe cotransport and countertransport

A

If all solutes are transported in the same direction across the cell membrane it is called cotransport
If all solutes are transported in the opposite direction across the cell membrane it is called countertrasnport

59
Q

What is osmosis?

A

The flow of water across a semipermeable membrane because of its differences in solute concentration

60
Q

The difference between osmosis and diffusion is that diffusion occurs because of a concentration difference of water, while osmosis occurs because of what?

A

a pressure difference

61
Q

What is the osmolarity of a solution?

A

its concentration of osmotically active particles

62
Q

How do you calculate osmolarity?

A

Osmolarity = the # of particles per mole in solution (g) x the concentration of particles (C)

63
Q

If 2 solutions have the same calculated osmolarity they are called what?

A

isosmotic

64
Q

If you have a solution has a higher osmolarity than another the higher one is considered hyp__osmotic whereas the lower solution is considered hyp__osmotic

A

hyperosmotic

hypoosomotic

65
Q

What are ion channels?

A

Integral membrane proteins that, when open, permit the passage of certain ions.

66
Q

____ ion channels allow only a ions with specific characteristics to move through them.

A

Selective

67
Q

Selective ion channels that are lined with negative charges typically permit the passage of ____, and those lined with positive changes permit the passage of ____.

A

cations

anions

68
Q

What are the 2 types of ion channels that are controlled by gates?

A
  • Voltage-gated ion channels

- Ligand-gated ion channels

69
Q

Describe voltage-gated ion channels

A

These types of ion channels open or close based on the changes in the membrane potential

70
Q

Describe Ligand-gated ion channels

A

These types of ion channels open or close when a certain molecule (“ligand”) attaches to the ion channel

71
Q

What is a diffusion potential?

A

The potential difference generated across a membrane when a charged solute (an ion) diffuses down its concentration gradient

72
Q

What is equilibrium potential?

A

the diffusion potential that exactly balances or opposes the tendency for diffusion down the concentration difference

73
Q

What equation is used to calculate the equilibrium potential for an ion at a given concentration difference across a membrane?

A

Nernst

630: Medical Physiology (24 decks)

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