Cellular physiology

Question 1

18958 – Gap junctions of cells
A. are spanned by corresponding connexons
B. characteristically surround apical margins of epithelial cells
C. endow tissues with stability and strength
D. maintain cell polarity
E. are made up of ridges from adjacent cells

Answer 1

A
Ganong 19th ed. Ch 1 Page: 16

Question 2

22349 – The equilibrium potential across a membrane for any particular ion exists when
1: the concentration of that ion is the same on both sides of the membrane
2: the membrane is completely impermeable to the ion
3: the potential difference across the membrane is zero
4: there is no net passive movement of the ion across the membrane

Answer 2

FFFT
Guyton 7th Ed. Chapter: 10 Page: 101-104 Ganong 13th Ed. Chapter: 1 Page: 22-26

Question 3

21343 – The sodium pump in the cell membrane is inhibited by
1: decreased ATP production
2: a low intracellular potassium
3: cardiac glycosides
4: aldosterone

Answer 3

TFTF
Guyton 7th ed/Ganong 11th ed. CHAPTER: 9, 26/1, 20 PAGE: 97-98, 309/19-20/308

Question 4

22109 – With regard to energy metabolism
1: ATP is the most important source of energy for cellular metabolism
2: more ATP is formed when glycogen is metabolized to pyruvate than when glucose is metabolized to pyruvate
3: phosphocreatine is used to resynthesize ATP during exercise
4: phosphocreatine is the most abundant source of high energy phosphate bands

Answer 4

TTTT
Guyton 8th ed. Page: 790

Question 5

1698 – High-energy phosphate compounds include
1: cyclic adenosine monophosphate
2: glucose 6 phosphate
3: dihydronicotinamide adenosine dinucleotide (NADH2)
4: phosphocreatine

Answer 5

FFFT
Ganong 13th Ed. Ch. 3 P. 54 Ch. 17 P. 243

Question 6

21683 – Concerning biological oxidations
1: phosphorylcreatine synthesis takes place during anaerobic glycolysis
2: oxidative deamination takes place in the liver
3: the liver is the major site of urea formation
4: free fatty acids are oxidized in muscle and heart

Answer 6

FTTT
Ganong 20th Edition, Ch 3, pages 70, 71.

Question 7

23179 – If extracellular K+ concentration is reduced to 3.0 mmol/1
1: K+ will diffuse out of the cell
2: the cell membrane will become less negative on the inside
3: H+ will diffuse into the cell
4: K+ will be actively transported out of the cell

Answer 7

TFTF
Guyton 7th ed. CHAPTER: 35 PAGE: 421

Question 8

22949 – Intercellular communciation via chemical messengers that bind to receptors are typical of
1: neural communication
2: endocrine communication
3: paracrine communication
4: keratine communication

Answer 8

TTTF
Ganong 11th ed. CHAPTER: 1 PAGE: 25-26

Question 9

20553 – S. Bicarbonate is the most important buffer in the extra-cellular fluid BECAUSE R. buffers work most effectively near their pK

Answer 9

S is true, R is true but not a valid explanation of S
Guyton 9th ed. Page: 389
pK of phosphate = 6.8 - good buffer
pK of bicarbonate = 6.1 - not ideal, but works with CO2 by respiration

Question 10

20421 – S. Scurvy is associated with blood vessel fragility BECAUSE R. ascorbic acid is an essential cofactor for the synthesis of collagen

Answer 10

S is true, R is true and a valid explanation of S
Guyton 8th ed. Page: 785

Question 11

12530 – The most important buffer base in the extracellular fluid is
A. plasma protein
B. phosphate
C. bicarbonate
D. haemoglobin
E. lactate

Answer 11

C
here are three important buffer systems within the body. The phosphate buffer system has a pK of 6.8: ie near to plasma pH and therefore is an ideal buffer. However, phosphate concentration is quite low compared to bicarbonate concentration (B false). Proteins are effective buffers because many of the constituent amino acids have pKs close to physiological pH. However, most of the protein buffering capacity is intracellular (A false). The bicarbonate system has a pK of 6.1 which is far from ideal for buffering at pH 7.4. However, the two components of the buffer system can be individually regulated: CO2 by respiration and HCO - by the kidney. This dual regulation makes the bicarbonate system the most important for the extracellular fluid (C true).

Question 12

12919 – Filtration of a substance through the capillary basement membrane depends on
1: the molecular size of the substance
2: the protein-bound plasma concentration of the substance
3: the electrical charge on the surface of the substance
4: the positive charge of the endothelium and basement membrane of the capillary

Answer 12

TFTF
The glomerular membrane has two important features which determine whether a substance will be filtered through it: (i) pores of approximately 8 nm in diameter; and (ii) glycosylated proteins with a strong negative charge lining the pores. Thus an absolute size limit of 8 nm exists for substances to be filtered (A true). In addition substances slightly smaller than this but bearing a negative charge will
be prevented from passing through by electrostatic repulsion (C true). An example of the latter is albumin, which has a molecular diameter of approximately 6 nm but is filtered to a very small degree because of its negative charge. Protein is not filtered because of its size and charge (B and D false). The basement membrane is negatively charged.
Comments: This question is asking about factors influencing filtration, not the amount of a substance that is filtered.

Question 13

24189 – Nitric oxide
1: is synthesised from arginine
2: activates adenyl cyclase by binding to the heme group
3: crosses cell membranes readily
4: is also known as EDRF

Answer 13

TFTT
Ganong 18th ed. Chapter: 4 Page: 105

Question 14

22339 – In the cell membrane
1: of nerve and muscle the resting membrane potential is -70 to -90mV
2: potassium permeability is greater than sodium permeability
3: insulin causes an increase in resting membrane potential (hyperpolarization)
4: a decrease in resting membrane potential (depolarization)would result from a decrease in ECF sodium concentration

Answer 14

TTTF
Ganong 13th ed. CHAPTER: 1, 19 PAGE: 22-26, 286

Question 15

21288 – Osmosis may be described as the diffusion across a semipermeable membrane of
1: ionic solutes
2: water
3: solutes
4: solvent

Answer 15

FTFT
Ganong 13th Ed. Ch. 1 P. 6

Question 16

19306 – Which of the following statements about Na+ - K+ activated adenosine triphosphatase is correct?
A. this enzyme exchanges 2 Na+ ions for 3 K+ ions
B. the activity of this enzyme leads to depolarization of the cell
C. the activity of this enzyme increases when the intra-cellular Na+ concentration rises
D. the enzyme is made up of one alpha and two beta subunits
E. the drug ouabain binds to the enzyme at an intracellular site

Answer 16

C
Ganong 13th Ed. Chapter: 1 Page: 23

Question 17

0397 – S. Intracellular oedema may occur in areas where local blood flow is depressed BECAUSE R. inadequate oxygenation depresses cell membrane ionic pumps and allows sodium to leak into cells

Answer 17

S is true, R is true and a valid explanation of S
Guyton 8th ed. Page: 281

Question 18

14918 – S: Vasodilatation, hypovolaemia and oedema are prominent features of anaphylaxis because R: the antigen antibody reaction in
anaphylaxis releases 5-hydroxytryptamine which causes increased capillary permeability and widespread vasodilatation

Answer 18

S is true and R is false
Refer to Ganong, 19th Ed, Ch 33, page 610

Question 19

23534 – Which of the following hormones stimulate(s) adenylate cyclase?
1: Glucagon
2: Cortisol
3: Vasopressin
4: Calmodulin

Answer 19

TFTF
Ganong CHAPTER: 11 PAGE: 26

Question 20

15513 – Basophils contain
1: histamine
2: thromboxanes
3: heparin
4: lymphokine

Answer 20

TFTF
Refer to Ganong, 19th Ed, Ch 27, page 494

Question 21

22334 – Fundamental properties of the plasma membrane include
1: semipermeable nature
2: preferential permeability to lipid-soluble substances
3: low surface tension
4: high electrical resistance

Answer 21

TTTT

Question 22

23799 – A striated muscle fibre
1: develops from a single myoblast
2: contains numerous nuclei which are usually peripherally located
3: contains intercalated discs
4: has only one motor end plate

Answer 22

FTFT
Wheater, E.R. PAGE: 82, 105

Question 23

12813 – Concerning biological oxidations
1: loss of electrons may occur from a substance which is oxidized
2: the energy content of acetyl CoA is greater than that of acetic acid
3: one end product of the flavoprotein cytochrome system is water
4: conversion of NADH2 to NAD is associated with oxidative phosphorylation

Answer 23

TTTT
Oxidation is a chemical reaction resulting either in the combination of a substance with oxygen or in the loss of hydrogen or of electrons (A true). Oxidative phosphorylation is the production of ATP coupled to an oxidation reaction. Therefore, the conversion of NADH2 to NAD, which is an oxidative reaction, if coupled with the conversion of ADP to ATP, is an oxidative phosphorylation (D true). Coenzyme
A (CoA) is a high energy thioester. Reduced CoA (HS-CoA) can oxidise acetic acid to acetyl CoA, giving acetyl CoA a much higher energy content than acetic acid (B true). The flavoprotein cytochrome system (respiratory chain) of oxidative phosphorylation, is coupled with the oxidation of NADH and generates 3 moles of ATP and in the final step with oxidation of cytochrome a2 is coupled with the conversion of O2 to H2O (C true).

Question 24

20655 – S. Down regulation occurs when a hormone is present in excess of the number of available receptor sites BECAUSE R. the presence of a receptor-hormone complex gradually induces an increase in the number of active receptors

Answer 24

S is true and R is false
Ganong 19th Ed. CHAPTER: 1 PAGE: 35

Question 25

21918 – With regards to capillary membranes
1: different tissues may have greatly differing permeabilities
2: water is the molecule which most readily crosses capillary membranes
3: liver capillaries are readily permeable to plasma proteins
4: pores in the membranes are the sole means by which molecules can pass into interstitial fluid

Answer 25

TFTF
Guyton 7th ed. Chapter: 30 Page: 350-351

Question 26

20679 – S. Anaerobic metabolism produces less ATP per molecule of glucose than aerobic metabolism BECAUSE R. glycolysis of glucose to pyruvate does not produce ATP

Answer 26

Sis true and R is false

Question 27

20685 – S. Energy derived from fat supplies most of the needs for the peripheral tissues BECAUSE R. fat is readily converted to carbohydrate involving the reaction of acetyl CoA to pyruvate

Answer 27

S is true and R is false

Question 28

20979 – S. Intracellular Ca2+ is not necessary for muscle contraction BECAUSE R. Ca2+ is released from ATP during formation of the actin myosin complex

Answer 28

both S and R and false
Ganong 13th ed. CHAPTER: 3 PAGE: 50-53

Question 29

15147 – Cell membranes are practically impermeable to
1: Ca2+
2: Urea
3: H2O
4: organic anions

Answer 29

FFFT
Refer to Ganong, 19th Ed, Ch 1, page 26 and following

Question 30

13319 – Na+-K+ activated adenosine triphosphatase
A. exchanges two Na+ ions for three K+ ions
B. activity leads to depolarisation of the cell
C. activity increases when the intracellular Na+ concentration rises
D. is made up of one alpha and two beta subunits
E. is bound to the drug ouabain at an intracellular site

Answer 30

C
Sodium, potassium activated adenosine triphosphatase transports three Na+ out of the cell for each two K+ it transports in (A false). Cellular depolarization is dependent on factors other than the sodium/potassium pump (B false), and the structure is made up of single alpha and single beta subunits (D false). Ouabain binding site is extracellular (E false). It is an electrogenic pump, ie it produces net movement of positive charge out of the cell. The amount of Na+ provided to the pump is a rate limiting factor; the amount of Na+ extruded is regulated in feedback fashion by the amount of Na+ in the cell (C true).

Question 31

20841 – S. If the capillary blood pressure in a muscle falls to 10 mm Hg negligible glucose transfer will occur BECAUSE R. glucose transfer across the capillary wall occurs mainly by passive diffusion

Answer 31

S is false and R is true
Ganong 13th ed. Chapter 1 Page: 8