Cellular Physiology (Chapters 1, 2, 4, 25, & 31) Flashcards

Question

What is the major difference between active transport & diffusion?

Answer 1

Diffusion does NOT require extra energy - energy for this process is through normal kinetic motion of matter Active transport DOEs require an additional source of energy besides kinetic energy

Answer 2

The movement of all molecules and ions in the body fluids that consists of greater motion at a greater temperature so that more intermolecular interactions occur

Answer 3

Kinetic movement of molecules or ions occurs through a membrane opening or through intermolecular spaces without any interaction with carrier proteins in the membrane

Answer 4

The rate is determined by the 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

Answer 5

If a substance is lipid soluble (O2, N2, CO2, alcohol, etc) then it can diffuse directly through the lipid bilayer If more lipid soluble the substance is, the faster it can diffuse through If a substance is not lipid soluble but still smaller enough it can diffuse through large transport proteins Aquaporins: selectively permit passage of water through the membrane As substances get larger, their ability to diffuse falls off (ex. Urea is bigger than H2O and its penetration is drastically less)

Answer 6

Requires interaction of a carrier protein that aids passage of the molecules or ions through the membrane by binding chemically with them and shuttling them through the membrane

Answer 7

Protein pores and channels allow various substances in and out of the cell membrane however the diameter and electrical charge of a pore permit selectivity of certain molecules

Answer 8

Ex: The potassium channel permits passage of K+ ions across the cell membrane about 1000 times more readily than Na The ability of K+ to pass through but not Na+ which has a slightly smaller diameter can be explained by the structure of the protein

Answer 9

Tetrameric structure: consists of four identical protein subunits surrounding a central pore with pore loops that form a narrow selectivity filter lined with carbonyl oxygens

Answer 10

When hydrated potassium ions enter the selectivity filter, they interact with the carbonyl oxygens and shed most of their bound water molecules, permitting the dehydrated potassium ions to pass through the channel. The carbonyl oxygens are too far apart, however, to enable them to interact closely with the smaller sodium ions, which are therefore effectively excluded by the selectivity filter from passing through the pore

Answer 11

Inner surface of channel is lined with amino acids that are strongly negatively charged and can pull small dehydrated sodium ions into these channels therefore pulling the ions away from their hydrating water molecules

Answer 12

Gatelike extensions of the transport protein molecule which can close or open by conformational change of the shape of the protein molecule itself

Answer 13

Molecular conformation of gate responds to the electrical potential across the cell membrane

Answer 14

If charge is strongly negative on inside the outside sodium gates will remain shut because this is the desired charge across the membrane but if the inside suddenly loses charge then the gates would open to allow Na+ into the cell K+ channels are located closer to the inside of the membrane while Na+ channels are located closer to the outside of the membrane Opening K+ channels are responsible for terminating an action potential

Answer 15

Binding of a ligand causes a conformational change that opens or closes the gate Ex. Acetylcholine Channel: binding of Ach opens this channel

Answer 16

Channels conduct current in an all or nothing fashion At one specific voltage potential, a channel may be closed all the time whereas at another voltage potential a channel may be open all the time At in between voltages, gates tend to snap open and closed intermittently resulting in average current flow somewhere between the minimum and maximum

Answer 17

Substance diffuses through the membrane with the help of a specific carrier protein

Answer 18

Glucose and amino acids uses this type of diffusion and GLUT4 is the glucose transporter sensitive to changes in insulin level

Answer 19

Simple diffusion increases proportionately with the concentration of the diffusing substance, but in facilitated diffusion the rate of diffusion approaches a maximum, called Vmax, as the concentration of the diffusing substance increases

Answer 20

In facilitated diffusion the molecule to be transported is bound and the carrier protein undergoes a conformational change so the pore now opens to the opposite side of the membrane. Because the binding force of the receptor is weak, the thermal motion of the attached molecule causes it to break away and be released on the opposite side of the membrane. The rate at which molecules can be transported by this mechanism can never be greater than the rate at which the carrier protein molecule can undergo change back and forth between its two states

Answer 21

Net movement of water caused by concentration difference across a membrane – water moves towards the higher concentration of solute

Answer 22

The amount of pressure required to stop osmosis Number of particles (molar concentration) per unit volume of fluid not by the mass of the particles and this is because each particle in a solution regardless of its mass exerts on average the same amount of pressure against the membrane Particles that are bigger often have a slower velocity and vice versa

Answer 23

The osmolar concentration expressed as osmoles per kilogram of water/solvent rather than solution

Answer 24

The osmolar concentration expressed as osmoles per liter of solution rather than water

Answer 25

The body is not only made up of water

Answer 26

Used to express the concentration of solution in terms of numbers of particles

Answer 27

If a substance such as NaCl can completely dissociate into ions then 1 gram in molecular weight would equal 2 osmole because it can fully dissolve into two different ions whereas glucose cannot dissolve into ions so the same molecular weight of glucose would be equal to 1 osmole

Answer 28

300 milliosmoles per kilogram of water

Answer 29

1 osmole per liter will cause 19,300 mm g osmotic pressure in solution however in reality it may be lower than the calculated value because many ions in solution are highly attracted to one another and therefore do not fully dissociate to create full osmotic pressure potential

Answer 30

When a cell membrane moves molecules or ions “uphill” against a concentration gradient requiring an energy source

Answer 31

The logarithm of the degree of substance concentration Ex: 100-fold concentration requires twice as much energy as 10-fold concentration

Answer 32

Energy needed is derived directly from breakdown of ATP or other high-energy phosphate compound Sodium-potassium pump, calcium pump, hydrogen pump

Answer 33

Sodium-Potassium Pump: pumps Na+ out of cell while pumping K+ inside of the cell to maintain the negative electrical voltage across the membrane Larger subunit is alpha and smaller subunit is beta (unknown function) When three Na+ bind on inside and two K+ bind on outside then ATPase cleaves ATP causing conformational change leading to exchange of ions against concentration gradient This reaction can also happen in the other direction generating ATP depending on the needs of the cell

Answer 34

Three specific functions of the larger subunit: 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

Answer 35

Protective against cell volume causing swelling because since there are a large amount of negatively charged proteins and other organic compounds that cannot escape the cell, these compounds will attract positive ions which will cause osmosis into the cell so Na+-K+ pump will prevent this by readjusting the ion concentrations

Answer 36

Calcium Pump: maintains the low concentration of calcium ions in the intracellular space One calcium pump pumps calcium out of the cell The other calcium pump pumps calcium into an intercellular vesicular organelle such as the sarcoplasmic reticulum Both pumps have same ATPase activity as Na+-K+ pump

Answer 37

Hydrogen Pump: by same mechanism transports H+ at cortical collecting ducts in kidneys for excretion in urine to eliminate excess

Answer 38

Two types: cotransport or counter transport energy is derived secondarily from energy that has been stored in the form of ionic concentration differences across a cell membrane created originally by primary active transport

Answer 39

Sodium-glucose co-transport: Note that the transport carrier protein has two binding sites on its exterior side, one for sodium and one for glucose. Also, the concentration of sodium ions is high on the outside and low inside, which provides energy for the transport. A special property of the transport protein is that a conformational change to allow sodium movement to the interior will not occur until a glucose molecule also attaches. When they both become attached, the conformational change takes place, and the sodium and glucose are transported to the inside of the cell at the same time

Answer 40

This is important in intestinal tract and renal tubules in kidneys

Answer 41

Sodium-Calcium Counter-Transport: This is different because transport is occurring in opposite directions. Sodium ion binds to the carrier protein where it projects to the exterior surface of the membrane, while the calcium to be counter-transported binds to the interior projection of the carrier protein. Once both have become bound, a conformational change occurs, and energy released by the action of the sodium ion moving to the interior causes the calcium to move to the exterior

Answer 42

Highly variable and must be carefully matched by equal output of water from body to prevent body fluid volumes from increasing or decreasing Ex: Water can be ingested or can be synthesized in the body (~2100ml/day) by oxidation of carbohydrates (~200ml/day)

Answer 43

Through skin (not sweating) Through the respiratory tract Sweat Feces Kidneys

Answer 44

Sweat -> depending on physical activity & environmental temperature

Answer 45

As air enters it becomes saturated with water and therefore this water is lost when respiration occurs through lungs More in cold weather

Answer 46

Minimized by cholesterol-filled cornified layer of skin but if this is compromised such as with burns loss can increase up to 10-fold or 3-5 L/day

Answer 47

Water loss by the kidneys which are the most important means of controlling balance between input and output of both water and electrolytes

Answer 48

Total body water is about 60% body weight but as person grows older this percentage decreases likely due to increase in body weight being fat In women water is about 50% body weight because they have more fat than men In newborns water is about 70 to 75% of body weight

Answer 49

~28-42 liters of fluid or 40% of total body weight Different mixture of constituents but relatively similar between cells

Answer 50

~14 liters of fluid or 20% of total body weight

Answer 51

Interstitial Fluid: ~11liters of fluid Plasma: ~ 3 liters of fluid; noncellular part of the blood that exchanges substances continuously with the interstitial fluid through pores in capillary membranes (permeable to most things except protein) therefore plasma and interstitial fluids are constantly mixing and have same concentration except for proteins which have a higher concentration in the plasma

Answer 52

contain intracellular and extracellular fluid (~5 liters of fluid or 7% of body weight) About 60% of blood is plasma and 40% is red blood cells

Answer 53

Fraction of the blood composed of red blood cells True hematocrit is only about 96% of measured because when centrifuged a small amount remains trapped among RBCs

Answer 54

Plasma: 142 Intracellular: 14

Answer 55

Plasma: 7.4 Intracellular: 6.0-7.4

Answer 56

Plasma: 4.2 Intracellular: 140

Answer 57

Plasma: 1.3 Intracellular: 0

Answer 58

Plasma: 24 Intracellular: 10

Answer 59

Plasma: 5.6 Intracellular: -

Answer 60

Plasma: 106 Intracellular: 4

Answer 61

The volume of a fluid compartment in the body can be measured by placing an indicator substance in the compartment, allowing it to disperse evenly throughout the compartment's fluid, and then analyzing the extent to which the substance becomes diluted

Answer 62

All one needs to know for this calculation is (1) the total amount of substance injected into the chamber (numerator) and (2) the concentration of the fluid in the chamber after the substance has been dispersed (denominator) The requirements for this calculation to work are (1) the indicator disperses evenly throughout the compartment (2) the indicator disperses only in the department being measured (3) the indicator is not metabolized or excreted

Answer 63

1. Total Body Water: Antipyrine is a soluble lipid and can rapidly penetrate cell membranes and distribute itself uniformly between intracellular and extracellular compartments 2. Extracellular Fluid: can use any of several substances that disperse in the plasma and interstitial fluid but do not permeate the cell membrane 1. Radioactive sodium may diffuse into cells in small amounts so using this indicator is measuring the “sodium space” or “inulin space” rather than true extracellular fluid volume 3. Intracellular Fluid: this compartment cannot be measured directly but can be calculate (equation in chart) 4. Plasma Volume: must use a substance that does not readily penetrate capillary membranes but remains in vascular system after injection 5. Blood Volume: can be measured in hematocrit is known (equation in chart) or RBCs can be labelled with radioactive substance 6. Interstitial Fluid: this compartment cannot be measured directly but can be calculate (equation in chart)

Answer 64

Most of the time these calculations are pretty similar on body fluids, but it makes more sense to us OSMOLARITY because body fluids consist of more than just water

Answer 65

There is about a 1 mOsm/L difference between the total osmolarity of the plasma and intracellular fluids and this is due to osmotic effect of the plasma proteins causing greater pressure in the capillaries and therefore the plasma

Answer 66

Depends on the concentration of impermeant solutes and refer to whether solutions will cause a change in cell volume Measure of the osmotic pressure gradient because this value is only characterized by the solutes that cannot cross the membrane

Answer 67

Does not depend on whether solutes can or cannot pass the membrane; considers the total concentration of solutes Measure of the total solute concentration Transfer of fluid across the cell membrane occurs so rapidly that any difference in osmolarity is usually corrected within minutes

Answer 68

The cells will not shrink or swell because the water concentration in intracellular and extracellular fluids is equal and the solutes cannot enter or leave the cell Ex. 0.9% sodium chloride solution or 5% glucose solution are important in medicine because they can be infused in the blood without danger of upsetting osmotic equilibrium between intracellular and extracellular fluids

Answer 69

Solution has lower concentration of impermeant solutes than the solution it is placed in: water diffuses in and cell swells

Answer 70

Solution has higher concentration of impermeant solutes than the solution it is placed in; water diffuses out and cell shrinks

Answer 71

Solutions with osmolarity the same as the cell

Answer 72

Solution that has higher osmolarity than the normal extracellular fluid the cell is used to

Answer 73

Solution that has lower osmolarity than the normal extracellular fluid the cell is used to

Answer 74

Short term water moves into cell, long term cell swells and may burst

Answer 75

Short term water moves out of cell, long term cell shrinks and shrivels

Answer 76

Generally substances will become equal in two compartments over time (initially there may be net water flux)

Answer 77

When saline and glucose solutions are injected into IV they are adjusted to isotonicity so that osmotic equilibrium of body fluids is not disturbed Ex. If an individual is dehydrated they likely have a hypertonic state in their extracellular fluid due to lack of water so if 5% glucose is injected then this isotonic solution increases the extracellular fluid volume without disrupting solute concentrations

Answer 78

Would likely cause movement of water out of cells and into extracellular space Would be use for treatment of condition causing cellular swelling

Answer 79

Would likely cause movement of water from extracellular space into cells Would be used for treatment of condition causes cellular shrinking

Answer 80

With addition of isotonic NaCl you see increase in volume of extracellular fluid but no change in osmolarity With addition of hypotonic NaCl you see decrease of osmolarity in extracellular fluid as well as movement of fluid into cells With addition of hypertonic NaCl you see increase in osmolarity in extracellular fluid as well as movement of fluid out of cells and into extracellular space

Answer 81

Swelling: loss of sodium concentration in extracellular fluid causes movement of water into cells Can be caused by dehydration states or overhydration states (anything that results in loss of sodium or gain of water in extracellular space) dehydration, diarrhea, vomiting, retention of water, or overuse of diuretics that inhibit the ability of the kidneys to conserve sodium This loss of sodium inside cells can cause cellular swelling that can cause neurological symptoms and can lead to brain damage or possibly death With acute hyponatremia there is diffusion of H2O into cells but with chronic hyponatremia the swelling is attenuated by the transport of solutes from the cell Treatment = hypertonic solutions: cannot be added too quickly because this may outpace the brain's ability to recapture lost solutes and cause demyelination (less than 10-12 mmol/L in 24 hours and less than 18 mmol/L in 48 hours) This treatment would cause the water that moved into the cells and caused brain swelling to slowly move back towards the hypertonic solution in extracellular fluid space

Answer 82

Shrinkage: increased sodium concentration in extracellular space causes movement of water out of cells Can be caused by dehydration states or overhydration states (anything that results in gain of sodium or loss of water in extracellular space) Can be caused by inability to secrete antidiuretic hormone which is needed for kidneys to conserve water or simply dehydration Excessive secretion of aldosterone can cause overhydration which can also cause hypernatremia This condition is much less common than hyponatremia because it promotes intense thirst and stimulates secretion of antidiuretic hormone and both protect against this happening Treatment = hypoosmotic solutions: slowly because body has natural defense mechanisms that protect the cells from changes in volume

Answer 83

Intracellular Edema: caused by hyponatremia, depression of metabolic systems of tissues, or lack of nutrition to the cells Ex. Loss of blood flow to tissue then ion pumps stop working Inflammation typically increases cell membrane permeability allowing sodium and other ions to diffuse into interior of cell causes subsequent osmosis of water into cells

Answer 84

Extracellular Edema: caused by abnormal leakage of fluid from plasma to interstitial spaces across the capillaries or failure of the lymphatics to return fluid from the interstitium back to the blood (lymphedema) Lymphedema: can be caused by increased capillary pressure (kidney or heart failure), decreased plasma proteins (burns or liver disease), increased capillary permeability (infection or vitamin deficiency), blockage of venous return (surgery or cancer)

Cellular Physiology (Chapters 1, 2, 4, 25, & 31) Flashcards

(114 cards)