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GUYTON > Chapter 4: Transport of Substances Through Cell Membranes > Flashcards

Chapter 4: Transport of Substances Through Cell Membranes Flashcards

1
Q

These are proteins found in the lipid bilayer of the cell membrane that have watery spaces all the way through the molecule and allow free movement of water, as well as selected ions or molecules

A

channel proteins

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2
Q

These are proteins found in the lipid bilayer of the cell membrane that bind with molecules and ions that are to be transported, and conformational changes in the protein molecules then move substances through the interstices of the protein to the other side of the membrane.

A

carrier proteins

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3
Q

This means the random molecular movement of substances molecule by molecule, either through intermolecular spaces in the membrane or in combination with a carrier protein.

A

diffusion

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4
Q

What is the energy that causes diffusion?

A

energy of the normal kinetic motion of matter

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5
Q

This means movement of ions or other substances across the membrane in combination with a carrier protein in such a way that the carrier protein causes the substance to move against an energy gradient, such as from a low-concentration state to a high-concentration state.

A

Active transport

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6
Q

According to physicists, this refers to the motion of particles

A

heat

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7
Q

The continual movement of molecules among one another in liquids or gases is called:

A

diffusion

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8
Q

What is the type of diffusion wherein the kinetic movement of molecules or ions occurs through a membrane opening or through intermolecular spaces without interaction with carrier proteins in the membrane?

A

simple diffusion

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9
Q

In simple diffusion, the rate of diffusion is determined by:

A

amount of substance available, the velocity of kinetic motion, and the number and sizes of openings in the membrane through which the molecules or ions can move

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10
Q

This type of diffusion requires interaction of a carrier protein

A

facilitated diffusion

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11
Q

In facilitated diffusion, which structures aids the passage of molecules or ions through the membrane by binding chemically with them and shuttling them through the membrane in this form?

A

carrier proteins

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12
Q

What are the 2 pathways by which simple diffusion can occur

A
  1. through the interstices of the lipid bilayer

2. through water channels

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13
Q

This is an important factor for determining how rapidly a substance diffuses through the lipid bilayer

A

lipid solubility

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14
Q

These are highly specialized protein pores that selectively permit rapid passage of water through the cell membrane

A

aquaporins

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15
Q

What regulates the opening and closing of protein channels?

A

gates

  • *voltage-gated channels = electrical signals
  • *ligand-gated channels = chemical signals`
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16
Q

What is the structure of potassium channels?

A

tetrameric structure: 4 identical protein subunits with a central pore

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17
Q

What forms the selectivity filter at the top of the potassium channel pore?

A

pore loops

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18
Q

What molecules line the walls of the selectivity filter of potassium channels that allow interaction of potassium ions causing them to shed their bound water molecules, permitting the dehydrated potassium ions to pass through the pore?

A

carbonyl oxygens

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19
Q

How many transmembrane helices does 1 subunit of a potassium channel have?

A

2 transmembrane helices

**The structure of a potassium channel is composed of four subunits, each with two transmembrane helices

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20
Q

What is the diameter of a sodium channel?

A

0.3 to 0.5 nanometer

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21
Q

This is the narrowest part of the sodium channel’s pore

A

selectivity filter

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22
Q

What lines the walls of the selectivity filter of sodium channels?

A

strongly negatively charged amino acid residues

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23
Q

What is the diameter of the pore of Acetylcholine-gated channel?

A

0.65 nanometer

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24
Q

Where is the location of gates of voltage-gated sodium channels?
A. Inside of the cell membrane
B. Outside of the cell membrane

A

B. Outside of the cell membrane

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25
Q

Where is the location of the gates of voltage-gated potassium channels?
A. Inside of the cell membrane
B. Outside of the cell membrane

A

A. Inside the cell membrane

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26
Q

This is the fashion by which the channel conducts current; that is, the gate of the channel snaps open and the snaps closed, with each open state lasting for only a fraction

A

all-or-none fashion

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27
Q

This is the method used for recording ion current flow through single protein channels

A

Patch Clamp Method

28
Q

What is the other name for facilitated diffusion?

A

carrier-mediated diffusion

29
Q

This is the maximum rate of diffusion that occurs in facilitated diffusion

A

Vmax

30
Q

As the concentration of the diffusing substance increases, the rate of simple diffusion continues to increase proportionately but, in the case of facilitated diffusion, the rate of diffusion cannot rise higher than that the ______ level

A

Vmax

31
Q

This is the family of membrane proteins that transports glucose molecules.

A

GLUT

32
Q

What type of membrane transport is utilized by glucose and most of the amino acids?

A

facilitated diffusion

33
Q

This glucose transporter is activated by insulin, which can increase the rate of facilitated diffusion of glucose as much as 10- to 20-fold in insulin-sensitive tissues.

A

GLUT4

**This is the principal mechanism whereby insulin controls glucose use in the body

34
Q

What are the 3 factors that affect net rate of diffusion?

A
  1. Concentration difference
  2. Electrical potential difference
  3. Pressure difference
35
Q

The net diffusion rate is proportional to the ____________ of a substance across a membrane

A

concentration difference

Net diffusion ∝ (Co − Ci)

36
Q

This is the formula that will determine the ELECTRICAL DIFFERENCE that will balance a given CONCENTRATION DIFFERENCE of UNIVALENT ions.

A

Nernst equation

EMF (in mV) = ±61 log (C1/C2)
*in which EMF is the electromotive force (voltage) between side 1 and side 2 of the membrane, C1 is the concentration on side 1, and C2 is the concentration on side 2.

37
Q

The pressure in many capillaries is about ______ greater inside than outside.

A

20 mmHg

38
Q

This refers to the sum of all forces of the different molecules striking a unit surface area at a given instant

A

pressure

39
Q

This is the process of net movement of water caused by a concentration difference of water

A

osmosis

40
Q

This is the amount of pressure required to stop osmosis

A

osmotic pressure

41
Q

What determines the osmotic pressure exerted by particles in a solution?

A

Number of particles (Molar concentration: for nondissociated molecule)

**NOT THE MASS: The reason for this is that each particle in a solution, regardless of its mass, exerts, on average, the same amount of pressure against the membrane

42
Q

This is the unit used to express the concentration of a solution in terms of numbers of particles

A

osmole

43
Q

What is the normal osmolality of the extracellular and intracellular fluids?

A

300 milliosmoles per kilogram of water

44
Q

1 milliosmole per liter concentration is equivalent to _______ osmotic pressure

A

19.3 mmHg

45
Q

On average, the actual osmotic pressure of the body fluids is about ____ times the calculated value

A

0.93 times

**1 milliosmole per liter concentration is equivalent to 19.3 mm Hg osmotic pressure. Multiplying this value by the 300-milliosmolar concentration of the body fluids gives a total calculated osmotic pressure of the body fluids of 5790 mm Hg. The measured value for this, however, averages only about 5500 mm Hg. The reason for this difference is that many ions in the body fluids, such as sodium and chloride ions, are highly attracted to one another; consequently, they cannot move entirely unrestrained in the fluids and create their full osmotic pressure potential.

46
Q

This refers to the osmolar concentration expressed as osmoles per liter of solution rather than osmoles per kilogram of water

A

osmolality

47
Q

This is the process of moving molecules or ions uphill against a concentration gradient (uphill against an electrical or pressure gradient)

A

active transport

48
Q

This type of transport derives energy directly from the breakdown of adenosine triphosphate or some other high-energy phosphate compound

A

primary active transport

49
Q

This type of transport derives energy from the ionic concentration differences of secondary molecular or ionic substance between the two sides of a cell membrane

A

secondary active transport

50
Q

What forms the carrier protein of the Na+-K+ pump?

A

2 globular proteins:

  • alpha subunit (larger; 100,000 molecular weight)
  • beta subunit (smaller; 55,00o molecular weight)
51
Q

Which subunit of the Na+-K+ pump carrier protein anchors the protein complex in the lipid membrane?

A

beta subunit

52
Q

Which binding sites of the Sodium-Potassium pump protrudes to the inside of the cell?

A

Three binding sites for sodium ions

53
Q

Which binding sites of the Sodium-Potassium pump protrudes to the outside of the cell?

A

Two binding sites for potassium ions

54
Q

Which portion of the sodium-potassium pump has adenosine triphosphate activity?

A

inside portion near the sodium ion binding sites

55
Q

True or False:
The phosphorylated form of the Na+-K+ pump can either donate its phosphate to ADP to produce ATP or use the energy to change its conformation and pump Na+ out of the cell and K+ into the cell.

A

True

56
Q 
One of the most important functions of the Na+-K+ pump is to control the cell volume. Without function of this pump, most cells of the body would:
A. Swell
B. Shrink
C. Remain the same
D. Charged
A

A. Swell

57
Q

The Na+-K+ pump is said to be __________ because it creates an electrical potential across the cell membrane

A

electrogenic

58
Q

What type of transport is utilized by cells and some of its organelles to move calcium ions?

A

Primary active transport: Calcium pump

**One, which is in the cell membrane, pumps calcium to the outside of the cell. The other pumps calcium ions into one or more of the intracellular vesicular organelles of the cell, such as the sarcoplasmic reticulum of muscle cells and the mitochondria in all cells.

59
Q

Which parts of the body requires the primary active transport of hydrogen ion?

A

Gastric glands of the stomach

Distal tubule and Collecting ducts of the kidneys

60
Q

Which cells of the body have the most potent primary active mechanism for the transport of hydrogen ions of any part of the body?

A

parietal cells of the in the gastric glands

**In the gastric glands, the deep-lying parietal cells have the most potent primary active mechanism for transporting hydrogen ions of any part of the body. This mechanism is the basis for secreting hydrochloric acid in stomach digestive secretions.

61
Q

The hydrogen ions released by the parietal cells of the stomach is accompanied by which ions?

A

chloride ions to form HCl

62
Q

Which cells of the renal tubules also transport hydrogen ions by primary active transport?

A

intercalated cells

63
Q

Give the formula in determining the amount of energy required to transport a substance actively through a membrane.

A

Energy (in cal per osmole) = 1400 log (C1/C2)

64
Q

Which ions of the sodium-calcium counter-transport moves into the cell?

A

Sodium

65
Q

Which portion of the renal tubule has sodium-hydrogen counter-transport proteins?

A

proximal tubule

GUYTON (20 decks)

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