Biochemistry and Physiology Quiz 3

Question 1 of 20

1. Question

Plasma proteins and edema

( Circulation / Biological Compounds )

A malnourished patient has markedly reduced plasma albumin. Which outcome is most directly expected?

Increased plasma oncotic pressure and dehydration of tissues

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Decreased plasma oncotic pressure and peripheral edema

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Increased capillary hydrostatic pressure and vasoconstriction

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Decreased lymphatic drainage and pulmonary embolism

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Question 2 of 20

2. Question

Enzyme saturation – Michaelis–Menten

( Metabolism / Enzyme Kinetics )

At very high substrate concentration, the reaction rate of an enzyme approaches a maximum. This plateau is called:

Km

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Vmax

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Activation energy

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Turnover number

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Question 3 of 20

3. Question

Allosteric inhibition of glycolysis

( Metabolism )

High cellular ATP inhibits phosphofructokinase-1 (PFK-1) in glycolysis. This is an example of:

Competitive inhibition at the active site

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Allosteric feedback inhibition

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Noncompetitive inhibition by product removal

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Covalent irreversible inhibition

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Question 4 of 20

4. Question

Collagen synthesis defect

( Connective Tissue / Molecular Biology )

A patient with poor wound healing and bleeding gums has a vitamin C deficiency. Which collagen step is impaired?

Formation of tropoelastin

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Hydroxylation of proline and lysine in the rough ER

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Cleavage of C-peptide from procollagen in the Golgi

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Cross-linking of elastin with desmosine

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Question 5 of 20

5. Question

Sodium–potassium pump

( Membranes )

The Na⁺/K⁺-ATPase moves ions across the membrane in which ratio per ATP hydrolyzed?

3 Na⁺ into cell, 2 K⁺ out

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3 Na⁺ out, 2 K⁺ in

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2 Na⁺ in, 3 K⁺ out

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1 Na⁺ out, 1 K⁺ in

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Question 6 of 20

6. Question

Nerve action potential – absolute refractory period

( Nervous System )

The absolute refractory period of a neuron occurs because:

All Na⁺ channels are closed and ready to open

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Voltage-gated Na⁺ channels are inactivated and cannot reopen

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K⁺ channels are closed

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Membrane potential is hyperpolarized below resting level

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Question 7 of 20

7. Question

Sympathetic vs parasympathetic heart effects

( Circulation / Autonomic Physiology )

Activation of the sympathetic nervous system typically causes which change in the heart?

Decreased heart rate and contractility

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Increased heart rate and contractility

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Decreased conduction through AV node only

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No effect on cardiac function

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Question 8 of 20

8. Question

Starling forces at capillary

( Circulation )

Which force promotes movement of fluid out of a capillary into interstitial space?

Capillary oncotic pressure

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Interstitial oncotic pressure

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Interstitial hydrostatic pressure

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Plasma protein concentration

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Question 9 of 20

9. Question

Oxygen transport – left shift

( Respiration / Hemoglobin )

Which change causes a leftward shift of the oxyhemoglobin dissociation curve?

Increased 2,3-BPG

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Increased temperature

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Decreased pH (acidosis)

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Decreased CO₂ concentration

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Question 10 of 20

10. Question

Carbon dioxide transport in blood

( Respiration )

Most CO₂ in blood is transported as:

Dissolved CO₂ gas in plasma

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Carbaminohemoglobin bound to globin

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Bicarbonate ions in plasma

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CO bound to heme groups

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Question 11 of 20

11. Question

Renal handling – glucose

( Renal Physiology )

Under normal conditions, how is glucose handled by the nephron?

Freely filtered and completely secreted

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Freely filtered and partially reabsorbed

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Freely filtered and completely reabsorbed until transport maximum is exceeded

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Not filtered at the glomerulus

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Question 12 of 20

12. Question

Renin–angiotensin–aldosterone system

( Renal / Endocrines )

Which event stimulates renin release from the juxtaglomerular cells?

Increased renal perfusion pressure in afferent arteriole

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Sympathetic stimulation via β₁ receptors

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Elevated NaCl delivery sensed by macula densa

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High blood volume

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Question 13 of 20

13. Question

Salivary flow and composition

( Oral Physiology )

At high salivary flow rates, saliva tends to be:

Very low in bicarbonate and more acidic

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Higher in bicarbonate and closer to plasma osmolarity

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Completely isotonic with blood and protein-free

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Purely mucous with no ions

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Question 14 of 20

14. Question

Swallowing – phase under voluntary control

( Digestion / Oral Physiology )

Which phase of swallowing is largely voluntary?

Pharyngeal phase

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Esophageal phase

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Oral (buccal) phase

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Gastric phase

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Question 15 of 20

15. Question

Gastrin’s main effect

( Digestion / Endocrines )

The primary action of gastrin secreted by G cells is to:

Inhibit gastric acid secretion

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Stimulate gastric acid secretion and mucosal growth

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Stimulate bile release from gallbladder

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Inhibit gastric motility

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Question 16 of 20

16. Question

Insulin and GLUT4

( Endocrines / Metabolism )

Insulin promotes glucose uptake in skeletal muscle and adipose tissue mainly by:

Activating GLUT2 transporters

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Stimulating GLUT3 insertion into membranes

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Increasing GLUT4 transporter translocation to cell surface

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Opening voltage-gated Ca²⁺ channels

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Question 17 of 20

17. Question

Thyroid hormone effect on metabolism

( Endocrines )

Which systemic change is most characteristic of increased thyroid hormone levels?

Decreased basal metabolic rate and cold intolerance

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Increased basal metabolic rate and heat intolerance

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Increased body weight with decreased appetite

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Severe bradycardia and hypotension

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Question 18 of 20

18. Question

Skeletal muscle tetany

( Muscle Physiology )

Sustained tetanus in skeletal muscle occurs when:

Action potentials are so frequent that Ca²⁺ remains elevated in cytosol

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Muscle fibers run out of ATP completely

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Motor neurons are silent

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Only a single twitch occurs

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Question 19 of 20

19. Question

Cardiac action potential plateau

( Muscle / Cardiac Physiology )

The plateau phase (phase 2) of ventricular action potential is mainly due to:

Opening of voltage-gated Na⁺ channels

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Efflux of K⁺ only

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Balance between Ca²⁺ influx through L-type channels and K⁺ efflux

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Na⁺/K⁺-ATPase activity

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Question 20 of 20

20. Question

Oral fluid pH and caries risk

( Oral Physiology / Clinical )

A patient has chronically low salivary flow and pH frequently below 5.5. This condition favors:

Remineralization of enamel

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Demineralization and higher caries risk

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Complete protection against plaque bacteria

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Reduced need for fluoride

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Biochemistry and Physiology Quiz 3

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