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PHOL1001 > Topic 1 - Cellular Physiology > Flashcards

Topic 1 - Cellular Physiology Flashcards

1
Q

Gases such as oxygen and carbon dioxide cross the plasma membrane by active transport.

A

False

Gases are very lipid soluble and readily pass through the lipid bilayer. They diffuse down their concentration gradient by passive transport.

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2
Q

Gases such as oxygen and carbon dioxide cross the plasma membrane by passive diffusion through the lipid bilayer

A

True

Gases are very lipid soluble and readily pass through the lipid bilayer. They diffuse down their concentration gradient by passive transport.

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3
Q

Gases such as oxygen and carbon dioxide cross the plasma membrane by passive diffusion through a specific carrier protein.

A

False

Gases are very lipid soluble and readily pass through the lipid bilayer. They diffuse down their concentration gradient by passive transport.

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4
Q

Ions can cross the plasma membrane by diffusion through the lipid bilayer.

A

False

Unlike gases, ions and other polar molecules cannot diffuse through the lipid bilayer but cross the plasma membrane via channel proteins or are transported from one side of the membrane to the other by carrier proteins.

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5
Q

Ions can cross the plasma membrane by diffusion through channel proteins.

A

True

Unlike gases, ions and other polar molecules cannot diffuse through the lipid bilayer but cross the plasma membrane via channel proteins or are transported from one side of the membrane to the other by carrier proteins.

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6
Q

Ions can cross the plasma membrane by binding to specific carrier proteins.

A

Ions can cross the plasma membrane by binding to specific carrier proteins. True

Unlike gases, ions and other polar molecules cannot diffuse through the lipid bilayer but cross the plasma membrane via channel proteins or are transported from one side of the membrane to the other by carrier proteins.

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7
Q

A substance can be accumulated against it electrochemical gradient by active transport.

A

A substance can be accumulated against it electrochemical gradient by active transport. True

For any substance to be accumulated against its electrochemical gradient energy must be expended. In active transport this provided either by the hydrolysis of ATP ( e.g. the sodium pump) or by coupling the movement of one substance against its electrochemical gradient to the movement of another down its electrochemical gradient. This is secondary active transport. The sodium dependent uptake of glucose by enterocytes is one example.

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8
Q

A substance can be accumulated against it electrochemical gradient by facilitated diffusion.

A

False

For any substance to be accumulated against its electrochemical gradient energy must be expended. In active transport this provided either by the hydrolysis of ATP ( e.g. the sodium pump) or by coupling the movement of one substance against its electrochemical gradient to the movement of another down its electrochemical gradient. This is secondary active transport. The sodium dependent uptake of glucose by enterocytes is one example.

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9
Q

A substance can be accumulated against it electrochemical gradient by ion channels.

A

False

For any substance to be accumulated against its electrochemical gradient energy must be expended. In active transport this provided either by the hydrolysis of ATP ( e.g. the sodium pump) or by coupling the movement of one substance against its electrochemical gradient to the movement of another down its electrochemical gradient. This is secondary active transport. The sodium dependent uptake of glucose by enterocytes is one example.

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10
Q

A substance can be accumulated against it electrochemical gradient by a symport.

A

True

For any substance to be accumulated against its electrochemical gradient energy must be expended. In active transport this provided either by the hydrolysis of ATP ( e.g. the sodium pump) or by coupling the movement of one substance against its electrochemical gradient to the movement of another down its electrochemical gradient. This is secondary active transport. The sodium dependent uptake of glucose by enterocytes is one example.

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11
Q

The principal intracellular cation is Na+

A

False

Na+ is the principal EXTRACELLULAR cation and K+ is the principal INTRACELLULAR cation. Cl- is the principal extracellular ANION.

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12
Q

The principal intracellular cation is Cl-

A

False

Na+ is the principal EXTRACELLULAR cation and K+ is the principal INTRACELLULAR cation. Cl- is the principal extracellular ANION.

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13
Q

The principal intracellular cation is Ca2+

A

False

Na+ is the principal EXTRACELLULAR cation and K+ is the principal INTRACELLULAR cation. Cl- is the principal extracellular ANION.

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14
Q

The principal intracellular cation is K+

A

True

Na+ is the principal EXTRACELLULAR cation and K+ is the principal INTRACELLULAR cation. Cl- is the principal extracellular ANION.

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15
Q

The sodium pump is an example of active transport

A

True

The sodium pump is an example of ATP driven active transport. Na+/Ca+ exchange and Na+/H+ exchange are examples of secondary active transport. In these cases the energy is provided by this sodium gradient generated by the sodium pump.

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16
Q

The Cl-/HCO3- is an example of active transport

A

False

The sodium pump is an example of ATP driven active transport. Na+/Ca+ exchange and Na+/H+ exchange are examples of secondary active transport. In these cases the energy is provided by this sodium gradient generated by the sodium pump.

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17
Q

The Na+/Ca2+ is an example of active transport

A

True

The sodium pump is an example of ATP driven active transport. Na+/Ca+ exchange and Na+/H+ exchange are examples of secondary active transport. In these cases the energy is provided by this sodium gradient generated by the sodium pump.

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18
Q

The Na+ linked glucose uptake by the enterocytes is an example of active transport

A

True

The sodium pump is an example of ATP driven active transport. Na+/Ca+ exchange and Na+/H+ exchange are examples of secondary active transport. In these cases the energy is provided by this sodium gradient generated by the sodium pump.

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19
Q

The Na+/H+ exchange is an example of active transport

A

True

The sodium pump is an example of ATP driven active transport. Na+/Ca+ exchange and Na+/H+ exchange are examples of secondary active transport. In these cases the energy is provided by this sodium gradient generated by the sodium pump.

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20
Q

The sodium pump exchanges intracellular Na+ extracellular K+.

A

True

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21
Q

The sodium pump requires ATP.

A

True

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22
Q

The sodium pump directly links sodium efflux with potassium influx.

A

True

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23
Q

The sodium pump is an ion channel.

A

The sodium pump is an ion channel. False - The sodium pump is a carrier protein not an ion channel.

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24
Q

The sodium pump can be inhibited by metabolic poisons.

A

True

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25
Q

The sodium pump is important for maintaining a constant cell volume.

A

True

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26
Q

The resting membrane potential of the muscle fibre is close to 0mV.

A

False

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27
Q

The resting membrane potential of the muscle fibre is close to -90mV.

A

True

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28
Q

The resting membrane potential of the muscle fibre is close to +50mV.

A

False

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29
Q

The resting membrane potential of the muscle fibre is close to the K+ equilibrium potential.

A

True

The resting membrane potential is determined by the K+ gradient because there are many more open K+ channels than Na+ channels. Consequently the resting membrane potential is close to the K+ equilibrium constant.

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30
Q

The resting membrane potential is mainly determined by the K+ gradient.

A

True

The resting membrane potential is determined by the K+ gradient because there are many more open K+ channels than Na+ channels. Consequently the resting membrane potential is close to the K+ equilibrium constant.

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31
Q

The resting membrane potential is mainly determined by the Na+ gradient.

A

False

The resting membrane potential is determined by the K+ gradient because there are many more open K+ channels than Na+ channels. Consequently the resting membrane potential is close to the K+ equilibrium constant.

32
Q

The resting membrane potential is mainly determined by the Ca2+ gradient.

A

False

The resting membrane potential is determined by the K+ gradient because there are many more open K+ channels than Na+ channels. Consequently the resting membrane potential is close to the K+ equilibrium constant.

33
Q

Secretion always involves membrane vesicles.

A

False

Lipid-soluble molecules like the steroids and prostaglandins are secreted as they are synthesised and pass across the lipid bilayer. Vesicle-mediated secretion is called exocytosis.

34
Q

Secretion may be triggered by a rise is intracellular Ca2+.

A

True

Lipid-soluble molecules like the steroids and prostaglandins are secreted as they are synthesised and pass across the lipid bilayer. Vesicle-mediated secretion is called exocytosis.

35
Q

Secretion provides a means of inserting proteins into the plasma membrane.

A

True

Lipid-soluble molecules like the steroids and prostaglandins are secreted as they are synthesised and pass across the lipid bilayer. Vesicle-mediated secretion is called exocytosis.

36
Q

Endocytosis is used by cells to ingest bacteria and cell debris.

A

False

Cells take up large proteins from the extracellular fluid by receptor mediated endocytosis. Bacteria and cell debris are taken up by phagocytosis.

37
Q

Endocytosis is used by cells to retrieve elements of the plasma membrane after exocytosis.

A

True

Cells take up large proteins from the extracellular fluid by receptor mediated endocytosis. Bacteria and cell debris are taken up by phagocytosis.

38
Q

Endocytosis is used by cells to take up large molecules from the extracellular space.

A

True

Cells take up large proteins from the extracellular fluid by receptor mediated endocytosis. Bacteria and cell debris are taken up by phagocytosis.

39
Q

Hormones are chemical signals that are secreted into the blood.

A

True

Hormones are secreted by endocrine glands into the blood stream to act on cells at a distance. Paracrine signals act locally.

40
Q

Hormones can influence the behavior of many different cell types.

A

True

Hormones are secreted by endocrine glands into the blood stream to act on cells at a distance. Paracrine signals act locally.

41
Q

Hormones act only on neighbouring cells.

A

False

Hormones are secreted by endocrine glands into the blood stream to act on cells at a distance. Paracrine signals act locally.

42
Q

Hormones are secreted by specialized glands.

A

True

Hormones are secreted by endocrine glands into the blood stream to act on cells at a distance. Paracrine signals act locally.

43
Q

NO is released by one type of cell specifically to regulate the activity of others.

A

True

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

44
Q

Prostaglandins is released by one type of cell specifically to regulate the activity of others.

A

True

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

45
Q

Insulin is released by one type of cell specifically to regulate the activity of others.

A

True

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

46
Q

Adrenaline is released by one type of cell specifically to regulate the activity of others.

A

True

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

47
Q

Ca2+ is released by one type of cell specifically to regulate the activity of others.

A

False

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

48
Q

cAMP is released by one type of cell specifically to regulate the activity of others.

A

True

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

49
Q

Glucose is released by one type of cell specifically to regulate the activity of others.

A

False

NO and prostaglandins are paracrine signaling molecules. Insulin and adrenaline are hormones. Ca2+ and cyclic AMP are both intracellular mediators but cyclic AMP can spread from cell to cell via gap junctions. Glucose is a substrate for metabolism.

50
Q

Receptors are always proteins.

A

True

Many receptors are membrane proteins but some are intracellular proteins (e.g. steroid hormone receptors). Receptors may directly activate ion channels but some receptors are protein kinases that are activated when they bind their ligand. Many receptors activate G proteins and thereby modulate the levels of second messengers.

51
Q

Receptors are always located in the plasma membrane.

A

False

Many receptors are membrane proteins but some are intracellular proteins (e.g. steroid hormone receptors). Receptors may directly activate ion channels but some receptors are protein kinases that are activated when they bind their ligand. Many receptors activate G proteins and thereby modulate the levels of second messengers.

52
Q

Receptors may be membrane-bound enzymes.

A

True

Many receptors are membrane proteins but some are intracellular proteins (e.g. steroid hormone receptors). Receptors may directly activate ion channels but some receptors are protein kinases that are activated when they bind their ligand. Many receptors activate G proteins and thereby modulate the levels of second messengers.

53
Q

Receptors can activate second-messenger cascades via G proteins.

A

True

Many receptors are membrane proteins but some are intracellular proteins (e.g. steroid hormone receptors). Receptors may directly activate ion channels but some receptors are protein kinases that are activated when they bind their ligand. Many receptors activate G proteins and thereby modulate the levels of second messengers.

54
Q

The plasma membrane can generate action potentials in excitable cells.

A

True

Depends on voltage-controlled ion channels

55
Q

The plasma membrane may burst in hypertonic extracellular solution.

A

False

In a hypotonic solution, the extracellular fluid has a lower osmolarity than the fluid inside the cell; water enters the cell causing it to burst.

In a hypertonic solution, the extracellular fluid has a higher osmolarity than the fluid inside the cell; water leaves the cell.

56
Q

The plasma membrane may contain carbohydrates which confer ion permeability.

A

False

57
Q

The plasma membrane is made up of a lipid core sandwiched between 2 layers of protein.

A

False

58
Q

The plasma membrane is freely permeable to hydrophobic molecules.

A

False

59
Q

Diffusion of a substance across the cell membrane is an active process.

A

False

60
Q

Diffusion of a substance across the cell membrane decreases in rate at higher temperatures.

A

False

Increases in rate

61
Q

Diffusion of a substance across the cell membrane is generally faster for polar than non-polar molecules of similar molecular weight.

A

False

62
Q

Diffusion of a substance across the cell membrane may require a carrier molecule.

A

True

63
Q

Diffusion of a substance across the cell membrane is independent of the concentration gradient across the membrane.

A

False

64
Q

Body water can be divided into that within the cells the intracellular water and that which lies outside the cells, the extracellular water. The extracellular water is further subdivided into the plasma and the interstitial water (see Figure 1). The interstitial water lies outside the blood vessels and bathes the cells. In addition, a small percentage of body water is found in the lymphatic fluid.

A

-

65
Q

Body water contains many different substances in solution and the solutes and water of the space outside the cells is called the extracellular or interstitial fluid while that inside the cells is the intracellular fluid. The intracellular fluid is separated from the extracellular fluid by the plasma membrane of the individual cells which is composed of lipids (fats) and has a non-polar core. Consequently, polar molecules cannot readily cross from the extracellular fluid to the intracellular fluid

A

-

66
Q

The space between the cells (the interstitium) consists of connective tissue, chiefly collagen, and proteoglycan filaments together with an ultrafiltrate of plasma. The water of the interstitial fluid hydrates the proteoglycan filaments to form a gel (much like a thin jelly) and in normal tissues there is very little free flowing fluid. This is an important adaptation that prevents the free flow of fluid to the lower regions of the body under the influence of gravity. Exchange of water and solutes between the cells and the tissue fluid occurs through diffusion while exchange between the interstitial fluid and the capillaries or lymphatics also occurs by bulk flow (i.e. the physical movement of fluid).

A

-

67
Q

The amount of water in each fluid compartment can be determined by the dilution of specific markers. For a marker to permit the accurate measurement of the volume of a particular compartment it must be evenly distributed throughout that compartment and it should be physiologically inert (i.e. it should not be metabolized or alter any physiological variable). The plasma volume can be estimated from the dilution of the dye Evans Blue which does not pass across the capillary endothelium into the interstitial space.

A

-

68
Q

To determine the total body water a known amount of radioactive water (3H2O) or deuterium oxide (2H2O) is injected and sufficient time allowed for the label to distribute throughout the body. A
sample of blood is taken and the amount of label in each ml measured. Measurement of the extracellular fluid volume requires a substance that freely passes between the circulation and the interstitial fluid but does not enter the cells. These requirements are met by inulin and by mannitol. The volume of the intracellular fluid is simply the difference between the total body water and the volume of the extracellular fluid.

A

-

69
Q

Total Body Water = Extracellular fluid + Intracellular fluid Extracellular fluid = Plasma + interstitial water

A

-

70
Q

Diffusion:

When a substance (the solute) is dissolved in a solvent such as water it forms a solution. When in solution, the individual solute molecules become dispersed within the solvent and are free to move in a random way. In an aqueous solution, the molecules of both water and solute are in continuous random motion with frequent collisions between them. This process leads to diffusion, the random dispersion of molecules in solution. There is a tendency for a solute to diffuse from a region of high concentration to one of a lower concentration (i.e. down its concentration gradient).

A

-

71
Q

Diffusion:

The rate of diffusion in a solvent depends on temperature (it is faster at higher temperatures), the magnitude of the concentration gradient and the area over which diffusion can occur. In general, large molecules diffuse more slowly than small ones. The molecular characteristics of the solute and solvent also affect the rate of diffusion. These characteristics are reflected in a physical constant known as the diffusion coefficient.

A

-

72
Q

The osmotic pressure of the body fluids:

When an aqueous solution is separated from pure water by a membrane that is permeable to water but not to the solute, water moves across the membrane into the solution by a process known as osmosis. This movement can be opposed by applying a hydrostatic pressure to the solution. The pressure that is just sufficient to prevent the uptake of water is known as the osmotic pressure of the solution. The osmotic pressure of a solution is expressed as the osmolality and is related to the number of particles present per kg of solution independent of their chemical nature.

A

-

73
Q

The tonicity of solutions:

Although lipid membranes are hydrophobic, they are more permeable to water than they are to ions so that the osmolality of the intracellular fluid is the same as that of the extracellular fluid (i.e. the two fluids have an osmolality of about 290 mosmol kg-1 and are iso-osmotic). If the osmotic pressure in one compartment is higher than the other, water will move from the region of low osmotic pressure to that of the higher osmotic pressure until the two become equalised.

A

-

74
Q

The tonicity of solutions (2):

If a suspension of mammalian cells is placed in a solution of sodium chloride that had an osmolality of 260 mosmol kg-1 they would swell as water was drawn into the cells to equalise the osmotic pressure across the cell membrane. This concentration of sodium chloride is said to be hypotonic with respect to the cells. Conversely, if the cells were placed in a solution of sodium chloride that had an osmolality of 320 mosmol kg-1 they would shrink as water was drawn from the cells. In this case the fluid would be hypertonic. Cells placed in a solution of 0.9% sodium chloride in water (i.e. 0.9 g sodium chloride in 100 ml of water) neither swell nor shrink. This concentration has an osmolality ≈ 290 mosmol kg-1 and is said to be isotonic with the cells.

A

-

75
Q

Filtration:

When a fluid passes through a permeable membrane, it leaves behind those particles that are larger in diameter than the pores of the membrane. This process is filtration and is driven by the pressure gradient between the two sides of the membrane. When filtration separates large solutes, such as proteins, from small ones, such as glucose and inorganic ions (Na+, K+, Cl- etc.), the process is called ultrafiltration.

A

-

76
Q

Filtration (2):

The walls of the capillaries are not normally permeable to plasma proteins (e.g. albumin) but are permeable to small solutes. The pumping action of the heart causes a pressure gradient across the walls of the capillaries so tending to force fluid from the capillaries into the interstitial space. This process occurs in all vascular beds but is particularly important in the glomerular capillaries of the kidney which filter large volumes of plasma each day.

A

-

77
Q

The composition of the intracellular and extracellular fluids is very different:

Chemical analysis has shown that the composition of the intracellular fluid is very different to that of the extracellular fluid (see Table). It is rich in potassium ions (K+) but relatively poor in both sodium ions (Na+) and chloride ions (Cl-). It is also rich in proteins (enzymes and structural proteins) and the small organic molecules that are involved in metabolism and signalling (amino acids, ATP, fatty acids etc.).

A

-

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