Chp 4 Transp. of Subst through Cell Membrane

Question 1

Extracellular fluid contains a large amount of _____ but only a small amount of ______

Answer 1

sodium (Na+)

potassium (K+)

Question 2

Intracellular fluid contains a large amount of ____but only a small amount of _______

Answer 2

Potassium (K+)

Sodium (Na+)

Question 3

T or F
-Extracellular fluid contains a large amount of chloride ions, whereas the intracellular fluid contains very little of these ions

Answer 3

True

Question 4

T or F
The concentrations of _____and ____ in the intracellular fluid are considerably greater than those in the extracellular fluid.

Answer 4

phosphates
proteins
True

Question 5

______ _____ ___ ______ their molecular structures interrupt the continuity of the lipid bilayer, constituting an alternative pathway through the cell membrane. Many of these penetrating proteins can function as _____ _______

Answer 5

1. Protein molecules in the membrane

2. Transport protein

Question 6

What are channel proteins

Answer 6

Proteins which have watery spaces all the way through the molecule and allow free movement of water and selected Ions or molecules

Question 7

define Carrier Proteins

Answer 7

bind with molecules or ions that are to be
transported, and conformational changes in the protein molecules then move the substances through the interstices of the protein to the other side of the membrane.

Question 8

Transport through the cell membrane, either directly through the lipid bilayer or through the proteins, occurs via one of two basic processes.
Name 2 processes

Answer 8

diffusion or active transport.

Question 9

define Diffusion

What type of ENERGY causes diffusion

Answer 9

• random molecular movement of substances molecule by molecule, either through inter- molecular spaces in the membrane or in combination with a carrier protein.
• Normal KINETIC motion of matter

Question 10

Define Active Transport

What type of ENERGY allows for Active Transport

Answer 10

active transport 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.
-Requires additional source of energy besides Kinetic energy

Question 11

define Diffusion

Answer 11

Continual movement of molecules among one another in Liquids or in gases is called Diffusion

Question 12

Diffusion through cell membrane is divided into two subtypes:
Name each

Answer 12

1. Simple diffusion

2. facilitated diffusion

Question 13

Define Simple diffusion

Answer 13

Simple diffusion means that kinetic movement of molecules or ions occurs through a membrane opening or through intermolecular spaces without any interaction with carrier proteins in the membrane

Question 14

How is the rate of diffusion is determined?

Answer 14

By the amount of:

1. substance available,
2. the velocity of kinetic motion,
3. the number and size of openings in the membrane through which the molecules or ions can move.

Question 15

define Facilitated Diffusion

Answer 15

Facilitated diffusion requires interaction of a carrier protein.

Question 16

Simple diffusion can occur through the cell membrane by two pathways:
Name these pathways

Answer 16

(1) through the interstices of the lipid bilayer if the diffusing substance is lipid soluble
(2) through watery channels that penetrate all the way through some of the large transport proteins

Question 17

What important factor determines how rapidly a substance diffuses through the lipid bilayer?
Provide Ex of high lipid solubility molecules

Answer 17

The lipid solubility of the substance, which can dissolve directly in the lipid bilayer and diffuse through the cell membrane in the same manner that diffusion of water solutes occurs in a watery solution.

Ex: the lipid solubilities of:
oxygen, nitrogen, carbon dioxide, alcohol

Question 18

Many of the body’s cell membranes contain protein “pores” called ______that selectively permit_____ _____ _____ _____ .

Answer 18

• aquaporins

- rapid passage of water through the membrane

Question 19

The protein channels are distinguished by what two important characteristics:

Answer 19

(1) They are often selectively permeable to certain substances
(2) many of the channels can be opened or closed by gates that are regulated by electrical signals (voltage-gated channels) or chemicals that bind to the channel proteins (ligand-gated channels).

Question 20

Many of the protein channels are highly selective for transport of one or more specific ions or molecules.
What characteristics of the channels play a role in such selectivity?

Answer 20

1. Its diameter,
2. its shape
3. the nature of the electrical charges
4. chemical bonds along its inside surfaces.

Question 21

What is considered to be one of the most important protein channels?
Its diameter equates to ?

Answer 21

1. Sodium Channel

2. (.3 to .5 nanometer in diameter)

Question 22

What is the most important character of the Sodium Channel?

Answer 22

1. The inner surfaces of this channel are lined with amino acids that are strongly negatively charged

Question 23

The strong negative charge located at the inner surface of the sodium Channels can do what ?

Answer 23

These strong negative charges can pull small dehydrated sodium ions into these channels, actually pulling the sodium ions away from their hydrating water molecules

Question 24

How is the Ion permeability controlled ?

Answer 24

Gating of protein channels provides the means of controlling ion permeability off the channels.

Question 25

The opening and closing of gates are controlled in two principal ways: Name each

Answer 25

1. Voltage gating

2. Chemical (ligand) gating

Question 26

Describe Volage gating

Answer 26

Strong (Neg) charge on the inside of the cell membrane causes the the outside sodium gates to remain tightly closed
Once (Neg) charge are lost gates open allowing sodium to pass inward through the sodium pores.
Note: the Opening of the gates is partly responsible for terminating the action
potenial.

Question 27

Describe Chemical Gating

Answer 27

Some protein channel gates are opened by the binding of a chemical substance (a ligand) with the protein, which causes a conformational or chemical bonding change in the protein molecule that opens or closes the gate.

Question 28

One of the most important instances of chemical gating is what?

Answer 28

the effect of acetylcholine on the so-called acetyl- choline channel.

Question 29

What effect does acetylcholine have on chemical gating

Answer 29

Acetylcholine opens the gate of this channel, providing a negatively charged pore about 0.65 nanometer in diameter that allows uncharged molecules or positive ions smaller than this diam- eter to pass through.

Question 30

Chemical Gating: why is acetylcholine effect on the acetylcholine channel so important?

Answer 30

exceedingly important for the transmission of nerve signals from one nerve cell to another and from nerve cells to muscle cells to cause muscle contraction (

Question 31

Facilitated diffusion is also called _____ _____ _____because a substance transported in this manner diffuses through the membrane with the help of a specific carrier protein.

Answer 31

carrier-mediated diffusion

Meaning: the carrier facilitates diffusion of the substance to the other side.

Question 32

What is the major difference between Simple and Facilitated diffusion

Answer 32

1. Simple diffusion= as the concentration of the diffusing substance increases, the rate of simple diffusion continues to increase proportionately,
2. Facilitated diffusion, the rate of diffusion cannot rise greater than the Vmax level.

Question 33

Provide ex: of a substance the cross cell membrane through Facilitated diffusion

Answer 33

Glucose, galactose, fructose
(GLUT) transport
Most of Amino Acids

Question 34

What is the principal mechanism by which insulin controls glucose use in the body and what is activated by insulin to increase rate of FD

Answer 34

Transporter 4 (GLUT4) 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.

Question 35

Nernst equation:

Answer 35

Nernst equation:
EMF (in millivolts) = ±61log C1 /C2
EMF= electromotive force (voltage) between concentration side 1 and concentration side 2 of the membrane

Question 36

The rate of net diffusion into the cell has to be proportional to What?
Provide the Net diffusion Equation:

Answer 36

it has to be proportional to the concentration on the outside minus the concentration on the inside:
Net diffusion Equation: Net diffusion∝(Co −Ci)

Question 37

Explain: a) what happens once electrical Potential is applied across the membrane.
B) what has to to take place in order for the net diffusion to occur form left to right ?

Answer 37

A) As electrical potential is applied across the membrane, the electrical charges of the ions cause them to move through the membrane even though no concentration difference exists to cause movement.
B) the concentration of negative ions is the same on both sides of the membrane but a positive charge has been applied to the right side of the membrane and a negative charge has been applied to the left, creating an electrical gradient across the membrane. The positive charge attracts the negative ions, whereas the negative charge repels positive. Therefore Net Diffusion takes place from L to R

Question 38

Why is the Nernst Equation important?

Answer 38

important in understanding the transmission of nerve impulses

Question 39

At times there is a considerable pressure difference which develops between the two sides of a diffusible membrane.

Provide an example of where this pressure difference occurs?

Answer 39

1) at the blood capillary membrane in all tissues of the body.

Question 40

What is the pressure difference INSIDE and OUTSIDE of the CAPILLARY?

Answer 40

The pressure is about 20 mm Hg greater inside the capillary than outside.

Question 41

There is a Pressure Difference Across the two sides of diffusible Membrane. Explain the meaning of Pressure.

Answer 41

Pressure actually means the sum of all the forces of the different molecules striking a unit surface area at a given instant.

Question 42

What is the most abundant substance that diffuses through the cell membrane

Answer 42

Water, ordinarily diffuses in each direction through the red blood cell membrane per second to equal about 100 times the volume of the cell itself.

Question 43

Under certain conditions, a “concentration difference for water” can develop across a membrane.. what happens when this occurs?

Answer 43

then the net movement of water occurs across the cell membrane, causing the cell to either swell or shrink…depending on the direction of water movement.

Question 44

define osmotic pressure?

Answer 44

The amount of pressure required to stop osmosis

Question 45

T or F:
The osmotic pressure exerted by particles in a solution, whether they are molecules or ions, is determined by the number of particles per unit volume of fluid, not by the mass of the particles

Answer 45

True

Question 46

T or F:
The osmotic pressure exerted by particles in a solution, whether they are molecules or ions, is determined by the by mass of the particles and not the number of particles per unit volume of fluid

Answer 46

False

Question 47

Smaller particles move at a Higher Velocities in such a way that their average “Kinetic Energies” (k) is determined by what equation?

Answer 47

k = mv(2) /2

Question 48

What factor determines the osmotic pressure of a solution?

Answer 48

Is the concentration of the solution in terms of number of particles (which is the same as its molar concentration if it is a nondissociated molecule), not in terms of mass of the solute.

Question 49

To express the concentration of a solution in terms of numbers of particles, the unit called the _____ is used in place of grams.

Answer 49

Osmole

Question 50

1 osmole is equal to what? . Thus, 180 grams of glucose, which is 1 gram molecular weight of glucose, is equal to _____ _____of glucose because glucose does not dissociate into ions.

Answer 50

1) . 1 gram molecular weight of osmotically active solute

2) 1 osmole

Question 51

If a solute dissociates into 2 ions, 1 gram molecular weight of the solute will become ______ ______ because the number of osmotically active particles is now as ____ __ _____ as in the case for the nondissociated solute.

Answer 51

1) 2 osmoles

2) twice as great

Question 52

Define Osmolarity?

Answer 52

Osmolarity is the osmolar concentration expressed as osmoles per “liter of solution” rather than osmoles per kilogram of water.

Question 53

Define Osmolality?

Answer 53

“Osmoles” per kilogram of water

Question 54

T or F:
it is far more practical to measure “osmolarity” than “osmolality”, measuring osmolarity is the usual practice in almost all physiological studies.

Answer 54

True

Question 55

When a cell membrane moves molecules or ions “uphill” against a concentration gradient (or “uphill” against an electrical or pressure gradient), the process is called ______ ______

Answer 55

active transport.

Question 56

Name some Examples of Different substances that are actively transported through at least some cell membranes?

Answer 56

sodium, potassium, calcium, iron, hydrogen, chloride, iodide, and urate ions, several different sugars, and most of the amino acids.

Question 57

Active transport is divided into what?

Answer 57

two types: primary active transport and secondary active transport

Question 58

What happens in Primary Active Transport?

Answer 58

In “primary active transport” the energy is derived directly from breakdown of adenosine triphosphate (ATP) or some other high-energy phosphate compound.

Question 59

What happens in Secondary Active Transport?

Answer 59

The “secondary active transport” , the energy is derived secondarily from energy that has been stored in the form of “ionic concentration differences” of secondary molecular or ionic substances between the two sides of a cell membrane…created originally by PAT

Question 60

What does the Transport depend on….in order to penetrate through the cell membrane?

Answer 60

carrier proteins

Question 61

What happens during Primary Active Transport?

Answer 61

Sodium-Potassium Pump Transports Sodium Ions Out of Cells and Potassium Ions Into Cells

Question 62

Why is Sodium-Potassium Pump so important?

Answer 62

This pump is responsible for maintaining the sodium and potassium concentration differences across the cell membrane, as well as for establishing a negative electrical Voltage inside the Cells.

Question 63

What are the basic physical components of the “Carrier Protein” that of the Na+ -K+ pump?

Answer 63

The carrier protein is a complex of two “separate globular proteins”:

1) larger one called the α subunit (molecular weight of about 100,000)
2) smaller one called the β subunit, molecular weight 55,000.

Question 64

Note: function of the smaller protein is not known (except that it might anchor the protein complex in the lipid membrane).
The larger protein has three specific features that are important for the functioning of the pump: NAME THEM

Answer 64

1. It has three binding sites for sodium ions on the portion of the protein that protrudes to the inside of the cell.
2. It has two binding sites for potassium ions on the outside.
3. The inside portion of this protein near the sodium binding sites has adenosine triphosphatase (ATPase) activity.

Question 65

1) Haw many and which ions bind on the outside of the carrier protein?
2) How many and which ions bind on the inside,

Answer 65

1) 2 -K+Potassium ions

2) 3 Na+ sodium ions

Question 66

What activates the ATPase function of the protein?

Answer 66

When two potassium ions bind on the outside of the carrier protein and three sodium ions bind on the inside, the ATPase function of the protein becomes activated.

Question 67

Activation of the ATPase function leads what?

Answer 67

To cleavage of one molecule of ATP, splitting it to adenosine diphosphate (ADP) and liberating a high-energy phosphate bond of energy.

Question 68

What happens once Activation of the ATPase function leads to cleavage of one molecule of ATP, splitting it to adenosine diphosphate (ADP) and liberating a high-energy phosphate bond of energy?

Answer 68

This liberated energy is then believed to cause a chemical and conformational change in the protein carrier molecule, extruding the three sodium ions to the outside and the two potassium ions to the inside.

Question 69

T or F

Na+-K+ ATPase pump run in reverse?

Answer 69

True

Question 70

One of the most important functions of the Na+-K+ pump is?

Answer 70

Is to control the volume of each cell. Without function of this pump, most cells of the body would swell until they burst

Question 71

the membrane is far less permeable to ____ ____ than it is to ____ ____, and thus once the sodium ions are on the outside, they have a strong tendency to stay there. This process thus represents a net loss of ions out of the cell, which initiates what?

Answer 71

1) (Na+) sodium ions
2) (K+ ) potassium ions
3) osmosis of water out of the cell as well.

Question 72

What happens If a cell begins to swell?

Answer 72

Na+-K+ pump is automatically activated, moving still more ions to the exterior and carrying water with them

Question 73

Why is the NaK pump also known as “Electrogenic”?

Answer 73

because it creates an electrical potential across the cell membrane.
Explination: moving 3 Na out and 2K in of the cell, creates positivity outside the cell but results in a deficit of positive ions inside the cell; that is, it causes negativity on the inside

Question 74

What is a basic requirement in nerve and muscle fibers for transmitting nerve and muscle signals.

Answer 74

electrical potential

Question 75

What is another important Primary Active Transport mechanism?

Answer 75

Calcium Pump

Question 76

define Cytosol:

Answer 76

The cytosol, also known as intracellular fluid (ICF) or cytoplasmic matrix, or groundplasm, is the liquid found inside cells. It is separated into compartments by membranes.

Question 77

Primary active transport of hydrogen ions is important at two places in the body:

Answer 77

(1) in the gastric glands of the stomach

(2) in the late distal tubules and cortical collecting ducts of the kidneys.

Question 78

Discuss the mechanism of the gastric glands of the stomach:

Answer 78

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.
At the secretory ends of the gastric gland parietal cells, the hydrogen ion concentra- tion is increased as much as a million-fold and then is released into the stomach along with chloride ions to form hydrochloric acid.

Question 79

Discuss the mechanism of the renal tubules

Answer 79

In the renal tubules, special intercalated cells found in the late distal tubules and cortical collecting ducts also transport hydrogen ions by primary active transport.
In this case, large amounts of hydrogen ions are secreted from the blood into the urine for the purpose of elimi- nating excess hydrogen ions from the body fluids. The hydrogen ions can be secreted into the urine against a concentration gradient of about 900-fold.

Question 80

Sodium ions are transported out of cells by which Transport?

Answer 80

primary active transport

Question 81

Explain the phenomenon, so called Co-transport and name its form of Transport?

Answer 81

1) Co-transport= excess sodium outside the cell membrane is always attempting to diffuse to the interior. Under appropriate conditions, this diffusion energy of sodium can pull other substances along with the sodium through the cell membrane.
2) co-transport, is one form of secondary active transport.

Question 82

Glucose and many amino acids are transported into most cells against large concentration gradients: through which mechanism ?

Answer 82

the mechanism of this action is entirely by “co-transport”

Question 83

Name a special property of transport carrier protein

Answer 83

1) the transport carrier protein has two binding sites on its exterior side, one for sodium and one for glucose
The concentration of Na ions is high on outside and Low on inside which provides energy for the transport.
2) Special property of transport Protein is that a conformational change to allow sodium movement inside will not occur until a glucose molecule as also attached. Both are transported into the cell at the same time

Question 84

Sodium-glucose co-transporters are especially important mechanisms in transporting what?

Answer 84

glucose across renal and intestinal epithelial cells

Question 85

Sodium co-transport of glucose and amino acids occurs especially through the epithelial cells of What?

Answer 85

the intestinal tract and the renal tubules of the kidneys to promote absorption of these substances into the blood

Question 86

Sodium-hydrogen counter-transport occurs in several tissues. An especially important example is in?

Answer 86

the proximal tubules of the kidneys, where sodium ions move from the lumen of the tubule to the interior of the tubular cell while hydrogen ions are counter-transported into the tubule lumen.