Principles of Cellular Function ( 5% )

Question 1

Na/K ATPase:

• a) Hydrolyses ADP to ATP.
• b) Extrudes 3 Na from the cell for every 2 K in
• c) Consists of an α, β and γ subunit.
• d) Lies on the ECF side of the cell membrane.
• e) Is potentiated by the drug ouabain

Answer 1

• b) Extrudes 3 Na from the cell for every 2 K in
• • a) Hydrolyses ADP to ATP. (Opp)
• c) Consists of an α, β and γ subunit. (No gamma unit)
• d) Lies on the ECF side of the cell membrane. (Spans the membrane)
• e) Is potentiated by the drug ouabain. (Attenuated)

Question 2

The Na/K ATPase pump

• a) Mobilizes equal quantities of Na and K.
• b) Hydrolyses ADP.
• c) Has an extracellular binding site for ouabain
• d) Has the same structure in all tissues in the body.
• e) Consists of 3 subunits.

Answer 2

c) Has an extracellular binding site for digoxin/ouabain

Ouabain is a cardiac glycoside, like digoxin. They bind to the K+ binding site on the exterior of the cell. Hypokalaemia potentiates digoxin toxicity as there is less competition for binding. See pharmacology for more details.

• a) Mobilizes inequal quantities of Na and K. (3Na+ out, 2K+ in)
• b) Hydrolyses ATP
• d) Has the variable structure in different tissues in the body - presumably this is why digoxin affects the heart but not the renal tubules for example
• e) Consists of 2 subunits - alpha and beta

Question 3

concerning transmembrane ion pumps which is false

• a) they assist in the process of diffusion.
• b) the Cl channel is abnormal in cystic fibrosis
• c) they constitute one of the major energy processes in the cell
• d) some channels are opened by mechanical stretch
• e) uniport, symport and antiport refer to carrier or transport proteins

Answer 3

a) they assist in the process of diffusion.

Diffusion is movement down a conc gradient, ion pumps do the opposite, however ion pumps are often used to set up a concentration gradient for diffusion. This still seems like the best answer though

Question 4

2nd messengers

• a) are substances that interact with 1st messengers inside cells.
• b) are substances that bind to 1st messengers in the cell membrane
• c) are hormones secreted in response to stimulation by another hormone
• d) mediate the intracellular responses to many different hormones and neurotransmitters
• e) are not formed in the brain

Answer 4

• d) mediate the intracellular responses to many different hormones and neurotransmitters
• • a) are substances that interact with 1st messengers inside cells. (1’ messengers are ligands (ie extracellular), whilst 2’ messengers are intracellular (usually coupled to a receptor on the cell membrane))
• b) are substances that bind to 1st messengers in the cell membrane
• c) are hormones secreted in response to stimulation by another hormone e) are not formed in the brain

Question 5

regarding movements across cell membranes

• a) Exocytosis requires Na and energy
• b) Insulin reuptake is by receptor mediated endocytosis
• c) Thyroid hormones reduce Na/K ATPase activity.
• d) Active transport of Na is rarely coupled with other substances.
• e) Na/K ATPase has a 1:1 coupling ratio

Answer 5

b) Insulin reuptake is by receptor mediated endocytosis

“The half-life of insulin in the circulation in humans is about 5 min. Insulin binds to insulin receptors, and some is internal- ized. It is destroyed by proteases in the endosomes formed by the endocytotic process.”

• a) Exocytosis requires calcium and energy
• c) Thyroid hormones increase Na/K ATPase activity.
• d) Active transport of Na is frequently coupled with other substances.
• e) Na/K ATPase has a 3:2 coupling ratio

Question 6

Fluid movement across the capillary wall is mediated mainly by

• a) Diffusion
• b) Filtration
• c) Endocytosis
• d) Exocytosis
• e) Ion channels

Answer 6

b) Filtration

Question 7

with respect to the cell

• a) the bases composing RNA are adenine, guanine, thymine and urosine.
• b) ribosomes in eukaryocytes are composed of 30S and 50S subunits.
• c) mitochondria contain DNA transmitted only from the mother
• d) phospholipids are the only lipids found in the cell membrane.
• e) the golgi apparatus attaches amino acids to oligosaccharides.

Answer 7

• c) mitochondria contain DNA transmitted only from the mother
• • a) the bases composing RNA are adenine, guanine, thymine and urosine. (Uracil)
• b) ribosomes in eukaryocytes are composed of 30S and 50S subunits.( 40S and 60S)
• d) phospholipids are the only lipids found in the cell membrane. (Cholesterol as well)
• e) the golgi apparatus attaches amino acids to oligosaccharides. (Glycosylates proteins)

Question 8

Intracellular calcium

• a) Concentrations is approximately double the ECF concentration.
• b) Is essential to activate G protein as an intracellular messenger.
• c) Stored calcium is found in the ER and mitochondria
• d) Myosin light chain kinase binds to calcium prior to initiating muscle contracture.
• e) Thyroxine uses calcium as a second messenger.

Answer 8

Unsure which is correct answer. Could be b) as its wording is a little vague, and GPCR activation often -> Ca2+

• a) Concentrations is approximately 12,000x the ECF concentration.
• b) Is activated G protein as an intracellular messenger. (Is activated by a G-protein (via IP3))
• c) Stored calcium is found in the sarcoplasmic reticulum​
• d) Myosin light chain kinase binds to calcium prior to initiating muscle contracture. (Calmodulin binds Ca2+ which allows it to activate kinases such as MLCK)
• e) Thyroxine acts on a nuclear receptor

Question 9

Na/K ATPase

• a) Exchanges 2 Na out of the cell for every 3 K transported into the cell
• b) In neurons, it accounts for 30% of energy used by the cell
• c) Catalyses ADP to ATP
• d) β subunit bind the Na molecule.
• e) the amount of sodium provided to the pump is the rate limiting factor in its operation

Answer 9

• e) the amount of sodium provided to the pump is the rate limiting factor in its operation
• • a) Exchanges 2 Na out of the cell for every 3 K transported into the cell (opposite)
• b) In neurons, it accounts for 30% of energy used by the cell
• c) Catalyses ADP to ATP (opposite)
• d) β subunit bind the Na molecule. (Alpha)

Question 10

regarding extracellular volume maintenance

• a) control of Na balance is the major mechanism of maintaining ECF volume
• b) a rise in ECF volume stimulates ADH secretion.
• c) osmotic stimuli override volume stimuli in the regulation of ADH secretion
• d) ADH causes Na retention by the kidney
• e) Angiotensin II inhibits aldosterone secretion

Answer 10

d) ADH causes Na retention by the kidney by inducing ENaC in the collecting ducts

• Primarily this seems to be due to aldosterone, but plenty of sources indicate ADH does this as well, it just also causes water retention in excess of solute retention*
• a) control of Na balance is the major mechanism of maintaining ECF volume
• “the amount of Na+ in the ECF is the most important determinant of ECF volume” - Ganongs*
• b) a fall in ECF volume stimulates ADH secretion (but main stimulator is rise in serum osmolality)
• c) volume stimuli override osmotic stimuli in the regulation of ADH secretion
• e) Angiotensin II induces aldosterone secretion

Question 11

Which is the largest in size

• a) β1 globulin
• b) fibrinogen
• c) albumin
• d) α globulin
• e) Hb

Answer 11

b) fibrinogen

Question 12

bradykinin

• a) is named after its effect on the heart
• b) stimulates smooth muscle constriction
• c) stimulates GI smooth muscle contraction

Answer 12

c) stimulates GI smooth muscle contraction

Question 13

The human cell membrane

• a) Is a phospholipid trilayer
• b) Has the fatty acid radicals on its outer edge
• c) Is permeable to alcohol
• d) Is permeable to glucose
• e) All of the above

Answer 13

• c) Is permeable to alcohol
• • a) Is a phospholipid trilayer (bilayer)
• b) Has the fatty acid radicals on its outer edge
• d) Is permeable to glucose (needs transport)
• e) All of the above

Question 14

The peripheral proteins of the cell membrane:

• a) Act as ion channels
• b) Act as enzymes
• c) Act as co-transporters
• d) Act as hormone receptor types
• e) Generate the negative charge of the cell membrane

Answer 14

• b) Act as enzymes
• A, C, and E would have to cross the whole membrane, making them integral proteins. D would not be located in the cell membrane
• a) Act as ion channels
• c) Act as co-transporters
• d) Act as hormone receptor types
• e) Generate the negative charge of the cell membrane

Question 15

The golgi apparatus

• a) Is closely related to the ER
• b) Forms peroxisomes
• c) Contains oxidases to form hydrogen peroxide
• d) Contain a large number of ribosomes on their outer surface
• e) Is contained within the ectoplasm

Answer 15

• a) Is closely related to the ER
• • b) Forms peroxisomes (glycosylates proteins and lipids)
• c) Contains oxidases to form hydrogen peroxide
• d) Contain a large number of ribosomes on their outer surface (this is the rough ER)
• e) Is contained within the ectoplasm (is a membrane-enclosed sac)

Question 16

The nuclear membrane

• a) Allows molecules only of MW<1000 through its nuclear pores
• b) Is continuous with the ER
• c) Is lined with oxidative phosphorylation enzymes
• d) Is impermeable to RNA
• e) Consists of 3 distinct layers

Answer 16

• b) Is continuous with the ER
• • a) Allows molecules only of MW<1000 through its nuclear pores
• c) Is lined with oxidative phosphorylation enzymes (this occurs in the mitochondria)
• d) Is impermeable to RNA
• e) Consists of 3 distinct layers

Question 17

ATP:

• a) Is acetyl tetraphosphate
• b) Supplies the energy for muscle contraction
• c) Is largely formed in the ER
• d) Contains no nitrogen
• e) Stores energy in special sulphate bonds

Answer 17

• b) Supplies the energy for muscle contraction
• a) Is acetyl tetraphosphate (adenosine triphosphate)
• c) Is largely formed in the ER (mitochondria)
• d) Contains no nitrogen
• e) Stores energy in special sulphate bonds (??phosphate bonds)

Question 18

Intracellular fluid

• a) Contains phosphate in similar concentrations to extracellular fluid.
• b) Has a lower PCO2 than extracellular fluid.
• c) Has a K + concentration of 110meq/L
• d) Has a pH of 7.5.
• e) Contains more Mg than ECF

Answer 18

e) Contains more Mg than ECF

• a) Contains phosphate in similar concentrations to extracellular fluid. (ICF > ECF)
• b) Has a lower PCO2 than extracellular fluid. (Higher, otherwise would never diffuse out)
• c) Has a K + concentration of 110meq/L
• d) Has a pH of 7.5. (7.2)

Question 19

All of the following are endogenous antioxidants except

• a) Glutathione
• b) Transferrin
• c) Superoxide dismutase
• d) Catalase
• e) Ferrous sulphate

Answer 19

e) Ferrous sulphate

Question 20

Regarding ribosomes

• a) There are 3 subunits
• b) They are 65% DNA
• c) They synthesise haemoglobin
• d) They contain 30% DNA

Answer 20

c) They synthesise haemoglobin

• a) There are 3 subunits (2)
• b) They are 65% DNA
• d) They contain 30% DNA

Question 21

Smooth ER

• a) Is the site of cell steroid production
• b) Is the site of cell protein synthesis
• c) Is the site of cellular cytochrome oxidases

Answer 21

a) Is the site of cell steroid production

• b) Is the site of cell protein synthesis
• c) Is the site of cellular cytochrome oxidases

Question 22

pinocytosis

• a) adds to the cell membrane
• b) involves the uptake of soluble macromolecules

Answer 22

b) involves the uptake of soluble macromolecules( cf phagocytosis which is the engulfing of a substance within a pinched off part of the cell membrane)

Question 23

Which of the following is an anti-oxidant

• a) Vitamin D
• b) Vitamin B12
• c) Vitamin E
• d) Vitamin K
• e) Vitamin B6

Answer 23

Vitamin E

Question 24

bradykinin

• a) causes smooth muscle dilation
• b) kallikrein causes prohormone degradation to produce bradykinin

Answer 24

b) kallikrein causes prohormone degradation to produce bradykinin
* a) causes smooth muscle dilation (GI smooth muscle contraction)

Question 25

Total body water:

• a) Increases with age.
• b) Is typically 45% bodyweight
• c) Is typically 63% bodyweight.
• d) Is greater in men than women
• e) Is composed largely of interstitial fluid

Answer 25

d) Is greater in men than women. (Due to higher body fat in women)

• a) Increases with age. (the Opposite)
• b) Is typically 45% bodyweight (60%)
• c) Is typically 63% bodyweight. (60%)
• e) Is composed largely of interstitial fluid. (intracellular fluid)

Question 26

Regarding basic physiological measures all of the following are TRUE except:

• a) Osmolarity is the number of osmoles per Litre of solution.
• b) pH is the log to the base 10 of the reciprocal H+ concentration
• c) carbon has a molecular mass of 12 dalton
• d) osmolarity is measured by freezing point depression.
• e) one equivalent of Na+ is 23g/L.

Answer 26

d) osmolarity is measured by freezing point depression. (Osmolality)

• a) Osmolarity is the number of osmoles per Litre of solution.
• b) pH is the log to the base 10 of the reciprocal H+ concentration
• c) carbon has a molecular mass of 12 dalton
• e) one equivalent of Na+ is 23g/L. (Actually 23g - it is a mass, not a conc)

Question 27

With regards to cell membrane potential:

• a) The Donnan effect relies on non diffusible ions
• b) The exterior of the cell is negative with respect to the interior.
• c) The membrane potential tends to push chloride out of the cell
• d) It can be derived by measuring the chloride concentration and using the Nernst equation.
• e) K leaks out against a concentration gradient

Answer 27

a) The Donnan effect relies on non diffusible ions

• b) The exterior of the cell is negative with respect to the interior. (Opposite is true)
• c) The membrane potential tends to push chloride out of the cell (into the cell)
• d) It can be derived by measuring the chloride concentration and using the Nernst equation. (Derived by summing the membrane potentials for all membrane-permeable ions. The Nernst equation provides the equilibrium potentials using the concentration ratio (inside to outside))
• e) K leaks out against a concentration gradient. (Down a conc gradient, not against)

Question 28

Intracellular fluid:

• a) Is maintained by purely passive processes
• b) Varies little with dehydration
• c) Has chloride as its major anion
• d) Approximates 60% total body weight
• e) Can be measured by the dilution of deuterium oxide

Answer 28

e) Can be measured by the dilution of deuterium oxide

• a) Is maintained by purely passive processes (Passive and active – eg Na-K-ATPase)
• b) Varies little with dehydration. (Opposite)
• c) Has chloride as its major anion. (Phosphates and proteins)
• d) Approximates 60% total body weight. (40%; 60% is total body water)

Question 29

Which is correct:

• a) Osmolality is the number of osmoles per kg of solvent
• b) Osmolarity is unaffected by volume of solutes in the solution and by temperature.
• c) Because the density of water is 1, osmolality and osmolarity in plasma are essentially the same.
• d) The boiling point method is used to measure osmolarity.
• e) The process of osmosis determines both osmolarity and osmolality.

Answer 29

a) Osmolality is the number of osmoles per kg of solvent

• b) Osmolarity is unaffected by volume of solutes in the solution and by temperature. (Opposite. This is true for osmolality though)
• c) Because the density of water is 1, osmolality and osmolarity in plasma are essentially the same. (Dissolved solutes add mass)
• d) The boiling point method is used to measure osmolarity. (Freezing point)
• e) The process of osmosis determines both osmolarity and osmolality.

Question 30

With regards to body fluid compartments:

• a) Intracellular fluid constitutes 60% body weight.
• b) Females in general have higher total body water compared with males
• c) Plasma volume is ~ 3500mL
• d) Blood plasma is ~ 20% body weight.
• e) The ECF volume/ICF volume ratio is larger in adults than infants

Answer 30

c) Plasma volume is ~ 3500mL

• a) Intracellular fluid constitutes 60% body weight. (40%)
• b) Females in general have higher total body water compared with males (opposite due to female fat)
• d) Blood plasma is ~ 20% body weight. (5%)
• e) The ECF volume/ICF volume ratio is larger in adults than infants

Question 31

The resting membrane potential

• a) Is +70 in mammalian cardiac cells.
• b) Is responsible for only a small part of the energy requirements of the cell.
• c) Is increased with increased external Na.
• d) Implies that the inside of the cell is positive relative to the outside of the cell at rest.
• e) Is decreased by increasing external K.

Answer 31

e) Is decreased by increasing external K. (Membranes are relatively permeable to K+, hence this affects RMP significantly. Increasing external K+ will decrease the size of the conc gradient promoting K+ efflux, meaning that less positive charges are leaving the cell.)

• a) Is +70 in mammalian cardiac cells. (-70mV)
• b) Is responsible for only a small part of the energy requirements of the cell. (30%)
• c) Is increased with increased external Na. (The membrane is not very permeable to Na+, hence it contributes little to the RMP. Even if it did, increasing extracellular Na+ would promote more Na+ influx into the cell, resulting in a more positive RMP)
• d) Implies that the inside of the cell is positive relative to the outside of the cell at rest. (cellular interior is Negative cf exterior)

Question 32

regarding body fluids: a) blood plasma is 15% body weight b) intracellular fluid is 20% body weight c) extracellular fluid is about 7L in a 70kg man d) interstitial fluid volume is 10.5L in a 70kg man e) extracellular fluid is 40% body weight

Answer 32

d) interstitial fluid volume is 10.5L in a 70kg man (15%) a) blood plasma is 15% body weight (5%) b) intracellular fluid is 20% body weight (40%) c) extracellular fluid is about 7L in a 70kg man (20% = 14L) e) extracellular fluid is 40% body weight (20%)

Question 33

ECF compared to ICF has: a) More K b) Less PO4 c) More Mg d) Less Na

Answer 33

b) Less PO4

Question 34

Osmolarity is:

Answer 34

number of osmoles per litre of solution

Question 35

Osmolality is:

Answer 35

number of osmoles per kg of solvent

Question 36

Describe the body’s fluid compartments and their volumes.

Answer 36

TBW = 60% total body weight ICF = 40% ECF = 20% (plasma 5% + interstitial fluid 15%)

Question 37

What is tonicity

Answer 37

Osmolality of a substance related to plasma osmolality.

Question 38

In what ways may ions and other small molecules be transported across cell membranes ?

Answer 38

• Passive diffusion down electrochemical gradients - Active transport against gradient eg NaKATPase - Secondary active transport -Aquaporins - Co / Counter transport - Ion channels - voltage- and ligand- gated - Exocytosis - Endocytosis - Phagocytosis - Pinocytosis

Question 39

Describe the Na+ / K+ ATP-ase pump.

Answer 39

Transport 3Na out of the cell, 2K into the cell, uses one molecule of ATP. Has alpha and beta subunits. Spans entire cell membrane.

Question 40

What is osmosis

Answer 40

Diffusion of solvent molecules (eg water) to an area of higher solute (eg Na+) concentration, through a semi-permeable membrane through which the solute cannot pass

Question 41

What is a second messenger ?

Answer 41

Extracellular ligand binds a surface receptor –> morphological or chemical change in the intra cellular part of the receptor which will activate an enzyme, G Protein activation, ion channel activation, direct transcription etc –> increase in intracellular cAMP, Ca2+ etc –> secondary effect eg increased protein production

Question 42

1 Regarding cellular components:

• a) peroxisomes are larger than lysosomes
• b) pH of lysosomes is higher than the rest of the cytoplasm
• c) microfilaments are hollow
• d) myosin 1 molecules are characteristically found in muscle cells
• e) microfilaments are made up of actin

Answer 42

e) microfilaments are made up of actin

• a) peroxisomes are larger than lysosomes (?similar size)
• b) pH of lysosomes is higher than the rest of the cytoplasm (lower at 7.2 where enzymes are more effective. Safety mechanism so in case of a leak the enzymes are not as efficient)
• c) microfilaments are hollow (microtubules are hollow)
• d) myosin 1 molecules are characteristically found in muscle cells

Question 43

2 Na -K -ATPase is an example of a/an:

a) symport
b) uniport
c) biport
d) antiport
e) airport

Answer 43

d) antiport

Question 44

Which decreases Na-K-ATPase activity?

• a) thyroid hormones
• b) dopamine
• c) G-actin
• d) intracellularsodium
• e) insulin

Answer 44

b) dopamine

Thyroid and insulin increase the pumps

Dopamine reduces pump activity in the kidneys -> natriuresis

Question 45

Given that a person weighs 60kg and their haematocrit is 40%, their total blood volume is:

• a) 6L
• b) 5L
• c) 4L
• d) 3L
• e) cannot be calculated with the given information

Answer 45

b) 5L

5% 60 = 3L plasma

Hct 40% means plasma = 60%

3/0.6 = 5L

Question 46

What percentage of body weight is plasma?

• a) 2%
• b) 5%
• c) 8%
• d) 15%
• e) 20%

Answer 46

b) 5%

Question 47

ECF volume can be estimated using:

• a) inulin
• b) D2O
• c) Evan’s blue
• d) radioactivechromium
• e) ironisotopes

Answer 47

a) inulin

Non-secreted non-absorbed polysaccharide that is somehow used in ECF calculations

Question 48

The number of molecules in a mole is:

• a) 1X10^26
• b) 6X10^26
• c) 4X10^26
• d) 1X10^23
• e) 6X10^23

Answer 48

e) 6X10^23

Avogadros number

Question 49

The molecular mass of a substance is expressed in:

• a) moles
• b) Daltons
• c) equivalents
• d) osmoles
• e) grams

Answer 49

b) Daltons

1 Dalton = 1/12 the mass of Carbon-12

Question 50

Regarding mitochondria:

• a) genome inheritance is strictly maternal
• b) the citric acid cycle occurs at the outer membrane
• c) the space between the two membranes is called the matrix
• d) the mutation rate for mitochondrial DNA is less than for nuclear DNA
• e) involutions of the outer membrane are called cristae

Answer 50

a) genome inheritance is strictly maternal

Question 51

Which volume of distribution is evaluated with which substance?

• a) plasma–D2O
• b) RBC volume – Cr
• c) ECF – Evans Blue
• d) Interstitialfluid–Inulin
• e) ICF–mannitol

Answer 51

b) RBC volume – Cr

This concept does not seem to be mentioned at all in Ganongs or Katzungs. However, seems unlikely that Cr is used to measure RBC volume. So who knows, the correct answer isnt in the text.

Question 52

Which is correct?

• a) blood volume is 8% total body weight
• b) 2/3 total body weight is ECF
• c) 75% of ECF is blood plasma
• d) water content of lean tissue is 25%
• e) total body water increases with increasing age

Answer 52

a) blood volume is 8% total body weight

(?? 5% for plasma + 3% for RBC)

Question 53

12 For mitochondria, which is TRUE?

• a) NADH-DH, 5DH, bc, cox synthesise ATP
• b) the matrix is between the inner and outer mitochondrial DNA
• c) mitochondrial DNA is not transmitted paternally
• d) 99% of mitochondrial proteins are encoded by mitochondrial DNA
• e) ATP synthetase is powered by an electron gradient

Answer 53

c) mitochondrial DNA is not transmitted paternally

Question 54

13 Which is TRUE?

• a) the cytoskeleton is composed of hydroxyapatites
• b) the mitotic spindle is composed of actin microtubules
• c) myosin is the most abundant protein in cells
• d) colchicine stabilises microtubules preventing organelle movement
• e) actin-myosin interaction allows cells to move

Answer 54

e) actin-myosin interaction allows cells to move

Question 55

For the genome, which is TRUE?

• a) the human genome encodes 3 X 10^9 genes
• b) adenine binds to cytosine and guanine to thymine
• c) uracil replaces thymine in RNA
• d) 3% of DNA are introns
• e) haploid DNA in germ cells is single stranded

Answer 55

c) uracil replaces thymine in RNA

Question 56

16 For the Erlanger and Gasser classification, which is TRUE?

• a) Sunday morning syndrome mainly affects C fibres
• b) local anaesthetics primarily affect A fibres
• c) preganglionic autonomic fibres are type B
• d) C fibres have the largest diameter
• e) B fibres are the least susceptible to hypoxia

Answer 56

c) preganglionic autonomic fibres are type B

Question 57

For the glial cells, which is TRUE?

• a) one schwann cell can myelinate up to 40 neurons
• b) oligodenotocytes are the scavenger cells of the CNS
• c) microglia are the scavenger cells of the PNS
• d) there are up to three glial cells per neuron in the nervous system
• e) protoplasmic astrocytesase found in grey matter

Answer 57

e) protoplasmic astrocytesase found in grey matter

Question 58

For cardiac muscle, which is FALSE?

• a) HERG really is the acronym for human ether-a-go-go related gene
• b) intercolated discs are calcified structures within cardiac muscle cells
• c) resting membrane potential is -90mV
• d) cardiac muscle requires continuous supply of O2 to function
• e) cardiac muscle action potential time decreases with increasing heart rate

Answer 58

b) intercolated discs are calcified structures within cardiac muscle cells

Question 59

For neurotransmitters, which is TRUE?

• a) acetylcholine is synthesised by true cholinesterase
• b) atropine blocks muscarinic cholinergic receptors
• c) catecholamines are formed from VMA (vanillylmandelic acid)
• d) adrenaline has a higher affinity for α rather than β adrenergic receptors
• e) dopamineisformedbyCOMTfromtryptophan

Answer 59

b) atropine blocks muscarinic cholinergic receptors

Question 60

Regarding body water, which is FALSE?

• a) 1/3 total body weight is extra and 2/3 intra cellular
• b) 60% of body weight is water
• c) plasma is 8% and total blood 10%, of body weight
• d) of extracellular fluid, 25% is vascular, 75% extravascular
• e) interstitial fluid is 15% of body weight

Answer 60

c) plasma is 8% and total blood 10%, of body weight

(5 + 8% respectively)

Unsure how a) is correct though - numbers would be right for total body WATER but not total WEIGHT

Question 61

Chemical composition, which is TRUE?

• a) pH is the negative natural logarithm of [H+]
• b) pH 5 to pH 6 involves tenfold increase in [H+]
• c) pH remains 7.4 +/- 0.05 in ECF, stabilised by buffer
• d) H2O and CO2<-> H2CO3 <->H+ and HCO -, adding H+ shifts the equilibrium to the right, while adding ??? shifts it to the left
• e) the Donnan effect does not contribute significantly to the balance of electrolyte between intra and extra vascular compartment

Answer 61

c) pH remains 7.4 +/- 0.05 in ECF, stabilised by buffer

• a) pH is the negative natural logarithm of [H+] (negative log 10)
• b) pH 5 to pH 6 involves tenfold increase in [H+] (10 fold reduction)
• d) H2O and CO2<-> H2CO3 <->H+ and HCO -, adding H+ shifts the equilibrium to the right, while adding ??? shifts it to the left (opposite)
• e) the Donnan effect does not contribute significantly to the balance of electrolyte between intra and extra vascular compartment (it does)

Question 62

Nerve fibres, which is FALSE?

• a) 70% of energy requirement of nerves is used in maintaining polarity across the recytlemina by action of Na-K ATPase
• b) metabolic rate of nerves doubles in max action
• c) “C” type fibres are non-myelinated and include some of the sympathetic preganglionic fibres
• d) “A” and “B” fibres are all myelinated
• e) effects of local anaesthetic are maximal in “C” fibres

Answer 62

c) “C” type fibres are non-myelinated and include some of the sympathetic preganglionic fibres

Are non-myelinated postganglionic fibres

Question 63

Regarding skeletal muscle, which is FALSE?

• a) metabolic rate of muscle may increase 100 times in maximal activity
• b) muscle cells can be excited chemically, mechanically and electrically, to produce action potentials in the cell membrane
• c) actin is a myosin-binding protein which is a molecular motor, converting ATP energy to monomers
• d) mitochondria are packed in between myofibrils
• e) T tubules occur over the junction of I and A bands

Answer 63

c) actin is a myosin-binding protein which is a molecular motor, converting ATP energy to monomers

I think this part about converting ATP to monomers is what is wrong

Question 64

5

More on muscles; which is TRUE?

• a) skeletal muscle cells act as syncytram, though intercellular communications
• b) some skeletal muscles are not subject to voluntary control
• c) smooth muscle contains regularly discharging pacemaker
• d) a variant of smooth muscle is found in the eye, which resembles skeletal muscle
• e) cardiac muscle does not contain regular striation

Answer 64

d) a variant of smooth muscle is found in the eye, which resembles skeletal muscle

Question 65

More on muscles; which is FALSE?

• a) T tubules are extensions of extracellular space
• b) “cystems’ of SR are in contact with T-tubules
• c) myosin molecules combine to form thick filaments while actin, tropomyosin, and the troponins the t…..
• d) an individual muscle cell is a myofibril, containing myofilaments
• e) the sarcolemnia transmits action potentials

Answer 65

d) an individual muscle cell is a myofibril, containing myofilaments

Myofilaments make up myofibrils.

A muscle cell/fibre contains many myofibrils