EOY 2021 — Past Paper Questions & Answers

Question 1

The genetic defect associated with Fabry's disease is most likely carried on

Accepted Answer

The X-chromosome — Fabry's disease is an X-linked lysosomal storage disorder caused by a deficiency of alpha-galactosidase A.

Question 2

Amount of dietary iodine in the control of thyroid hormone secretion

Accepted Answer

Forcing function — The body regulates the uptake and utilization of iodine to maintain thyroid hormone levels, making the amount of iodine available a variable that is subject to control.

Question 3

Movement of Cl- ion from gastric cells into the gastric cavity

Accepted Answer

diffusion — Chloride ions are actively transported into the gastric lumen via specific channels and transporters, which is not described by diffusion, filtration, osmosis, or pinocytosis.

Question 4

Myeloid cells in innate and adaptive immunity EXCLUDE the following:

Accepted Answer

Dendritic cell — Natural killer (NK) cells are lymphocytes, which are part of the lymphoid lineage, whereas the other options are myeloid cells.

Question 5

The following statement is FALSE about the cells arising from the common lymphoid progenitor

Accepted Answer

Natural killer cells are modified T lymphocytes — Natural killer cells are a distinct lineage of lymphocytes that develop from common lymphoid progenitors, separate from T lymphocytes.

Question 6

While complete aerobic oxidation of one mole of glucose in the cell yields 38 moles of ATP, complete catabolism of one mole of a 6- carbon atoms fatty acid through the citric acid cycle yields

Accepted Answer

Nearly equal amount of energy molecules — Fatty acids are more reduced than carbohydrates, leading to a higher ATP yield per carbon atom, with longer fatty acids typically yielding about twice the ATP of glucose.

Question 7

25. Immune privileged sites include the following EXCEPT:

Accepted Answer

Testis — Bone marrow is a primary lymphoid organ, actively involved in immune responses, and is not considered an immune privileged site.

Question 8

40. The human genome

Accepted Answer

Experiences only negative modification (mutation) when changes occur at meiosis — The human genome contains approximately 20,000-25,000 protein-coding genes, with 30,000 being a commonly cited, though slightly outdated, estimate.

Question 9

61. The following are characteristics of skeletal muscle fibres EXCEPT:

Accepted Answer

Extensibility — Skeletal muscle requires nervous stimulation to contract and does not exhibit automaticity, which is the ability to generate its own impulses.

Question 10

64. Increasing the frequency of stimulation so that a muscle contracts without relaxation is called

Accepted Answer

Synergy — Tetany is a sustained muscle contraction resulting from a high frequency of stimulation, preventing the muscle from relaxing between stimuli.

Question 11

8. Which type of sensation is most affected if the lesion is in the sensory cortex?

Accepted Answer

Position & fine touch — Discriminative sensations like position sense (proprioception) and fine touch require extensive processing in the sensory cortex for accurate perception and localization.

Question 12

4. There are several important differences between a chemical and an electrical synapse. Which of the following statements does NOT constitute a a difference between these two types of synapses?

Accepted Answer

Slow vs. faster propagation — Both chemical and electrical synapses can occur between nerve cells and muscle cells (e.g., neuromuscular junction for chemical, gap junctions in cardiac muscle for electrical).

Question 13

37. The following units of measurement would be appropriate

Accepted Answer

Milliequivalents per Liter of glucose concentration — Femtoliters (fL) are a standard unit for measuring cell volume, particularly in hematology (e.g., Mean Corpuscular Volume).

Question 14

73. When a calcium ion binds to troponin,

Accepted Answer

muscle relaxation occurs. — Calcium binding to troponin causes a conformational change that moves tropomyosin away from the myosin-binding sites on actin, allowing cross-bridge formation.

Question 15

19. The following is false regarding Sensory systems

Accepted Answer

Monitor the energy levels in the environment — Sensory systems detect and transmit information about stimuli; the initiation and execution of vegetative (autonomic) actions are primarily functions of the motor and autonomic nervous systems.

Question 16

3. The following is FALSE about Excitatory post-synaptic potentials.

Accepted Answer

Decline exponentially with a time constant. — Excitatory post-synaptic potentials (EPSPs) are graded potentials that decay over distance and time; they are not actively propagated like action potentials.

Question 17

98. Which of the following are adrenergic fibers?

Accepted Answer

Most postganglionic sympathetic fibers. — Adrenergic fibers release norepinephrine (or epinephrine), which is characteristic of most postganglionic sympathetic neurons.

Question 18

46. The nucleotide sequence that codes for start of protein synthesis is

Accepted Answer

Totally different for each protein — The start codon for protein synthesis is AUG (in mRNA). While "AUGG" is a typo and "UAAG" is a stop codon, this option is the only one that refers to codons involved in protein synthesis, making it the most plausible intended answer among the choices.

Question 19

Synthesis of a specific protein is initiated by

Accepted Answer

An integrase — RNA transcriptase (RNA polymerase) synthesizes mRNA from a DNA template, which is the first step in gene expression leading to protein synthesis.

Question 20

During inflammation

Accepted Answer

The second macrophage invasion is the first line of defense — During inflammation, cell adhesion molecules are upregulated on endothelial cells to facilitate the extravasation of leukocytes into the injured tissue.

Question 21

pH of gastric acid secreted.

Accepted Answer

External influences — In a homeostatic control system, the pH of gastric acid is a physiological parameter that is regulated and maintained within a narrow range, making it a controlled variable.

Question 22

Synaptic signaling between adjacent neurons is like hormone signaling in which of the following ways?

Accepted Answer

It sends its signal molecules quite a distance. — Both synaptic signaling (neurotransmitters) and hormone signaling involve specific signaling molecules binding to specific receptors on target cells to elicit a response.

Question 23

Reflex arc:

Accepted Answer

Is composed of receptors, afferent and efferent neurones only. — A reflex arc typically includes an integration center, which for most reflexes is located within the central nervous system (CNS).

Question 24

Concerning the parasympathetic nervous system:

Accepted Answer

Its postganglionic cell bodies are in the CNS. — Parasympathetic stimulation generally increases the secretion of watery saliva from salivary glands.

Question 25

The major difference between hormones that have intracellular receptors and those that have cell membrane receptors is that the former tend to be

Accepted Answer

Proteins — Hormones that bind to intracellular receptors (e.g., steroid hormones) must be lipid-soluble (hydrophobic) to cross the cell membrane and enter the cytoplasm or nucleus.

Question 26

Nonconstitutive exocytosis

Accepted Answer

Occurs exclusively for excretion of enzymes — Nonconstitutive (regulated) exocytosis involves the release of specific, fully processed molecules (e.g., hormones, neurotransmitters) that are stored in vesicles and released in response to a specific signal.

Question 27

Proteins that contain a src homology 2 domain (SH2 domain)

Accepted Answer

have a phosphoserine residue that causes them to bind to other proteins — SH2 domains specifically recognize and bind to phosphorylated tyrosine residues on other proteins, mediating protein-protein interactions.

Question 28

The total body iron content amounts to;

Accepted Answer

3-4gm — The total body iron content in an adult human is typically between 3 to 4 grams.

Question 29

Membrane receptors that attach phosphates to specific amino proteins in proteins are

Accepted Answer

important in yeast mating factors that contain amino acids. — Receptor tyrosine kinases are a class of membrane receptors that, upon ligand binding, phosphorylate specific tyrosine residues on intracellular proteins.

Question 30

Functions of the sensory systems include the following EXCEPT

Accepted Answer

Effecting movement of cilia in some epithelia — Sensory systems detect and transmit information about the environment, but motor systems are responsible for executing desired changes.

Question 31

It is correct to say that:

Accepted Answer

Stimulation of postganglionic parasympathetic neurons causes release of noradrenaline. — Acetylcholine is the neurotransmitter released by preganglionic neurons in both sympathetic and parasympathetic divisions, stimulating nicotinic receptors on postganglionic neurons in the autonomic ganglia.

Question 32

The propagation of an action potential across a chemical synapse consists of several steps. Which of the following steps is the slowest?

Accepted Answer

Exocytosis of the neuro-transmitter — While diffusion and exocytosis contribute to synaptic delay, the conformational change required for a receptor-operated channel to open after ligand binding can be a rate-limiting step.

Question 33

Withdrawal reflex upon exposure to pain

Accepted Answer

Adaptive control — A withdrawal reflex is a negative feedback mechanism where the response (withdrawal) counteracts the stimulus (pain).

Question 34

If I tell you that our very own Dr. Mjuaji has just discovered a new membrane channel that can change the membrane potential of neurons from -65 mV to -60 mV when activated, how would you characterize it?

Accepted Answer

as a new hyperpolarizing EPSP. — A change from -65 mV to -60 mV is a depolarization (less negative), and since it brings the membrane potential closer to the threshold for an action potential, it is an Excitatory Postsynaptic Potential (EPSP).

Question 35

The reason why antibiotics inhibit bacterial multiplication without affecting host cell multiplication is because

Accepted Answer

of the sheer difference in number of cells — Many antibiotics exploit the structural differences between bacterial (70S, with 30S and 50S subunits) and eukaryotic (80S, with 40S and 60S subunits) ribosomes to selectively inhibit bacterial protein synthesis.

Question 36

In many cells, adrenalin will bind to the alpha-1 receptor and Gaq will be activated. All of the following will happen EXCEPT

Accepted Answer

Protein kinase activity will be decreased — Alpha-1 receptor activation via Gq leads to increased phospholipase C activity, generating IP3 and DAG, which in turn increase intracellular Ca2+ and activate Protein Kinase C, generally leading to increased protein phosphorylation, not decreased protein kinase activity.

Question 37

Proprioception includes the following EXCEPT

Accepted Answer

Joint position — Proprioception is the sense of body position and movement, encompassing joint position and muscle sense; pain (nociception) and temperature (thermoception) are distinct sensory modalities.

Question 38

Which one of the following is not a criterion for small neurotransmitter (NT) status?

Accepted Answer

evidence of presynaptic release. — All options A, B, C, and E are generally considered criteria or supporting evidence for a substance to be classified as a neurotransmitter.

Question 39

Small transmitter molecules are:

Accepted Answer

made in the soma, packaged in small synaptic vesicles and transported down axons. — Small molecule neurotransmitters are typically synthesized in the presynaptic terminal and packaged into small, clear synaptic vesicles.

Question 40

Weight is controlled by this.

Accepted Answer

Adaptive control — Body weight is regulated by complex homeostatic mechanisms involving hormones and neural signals that operate primarily through negative feedback loops to maintain a set point.

Question 41

Following the release of all chemical messengers from their source cells, all of the following will occur EXCEPT

Accepted Answer

The hormone will travel to its target cell — Many chemical messengers, particularly peptide hormones, bind to receptors on the cell surface and do not enter the target cell to elicit a response.

Question 42

The following antigen can be detected as a microbiome by the human immune system:

Accepted Answer

Commensals found on skin, oral mucosa, conjunctiva and gastrointestinal mucosa — The microbiome refers to the community of commensal microorganisms (like those found on skin and mucosa) whose antigens are recognized and tolerated by the human immune system.

Question 43

Which one of the following conditions will result in a decrease in the magnitude of a nerve membrane action potential?

Accepted Answer

Increasing the extracellular concentration of sodium. — While hyperpolarization (making the membrane potential more negative) typically increases action potential magnitude by increasing Na+ channel availability, in some contexts, extreme hyperpolarization could lead to reduced excitability or a failure to reach full action potential amplitude, effectively decreasing the observed magnitude. (Note: Physiologically, stimulating during the relative refractory period (B) is a more direct cause of decreased action potential magnitude.)

Question 44

A muscle cramp is most likely due to lack of

Accepted Answer

Acetylcholine. — Muscle cramps, particularly sustained contractions (contractures), often result from insufficient ATP, which is required for the myosin heads to detach from actin, leading to a prolonged rigor state.

Question 45

Growth of hair is an example of this

Accepted Answer

Feedforward control — Hair growth follows a genetically programmed cycle (anagen, catagen, telogen) with intrinsic timing and minimal continuous feedback regulation to maintain a specific set point, characteristic of an open-loop control system.

Question 46

Actin is tethered to Z lines in the sarcomere by:

Accepted Answer

Chitin — Alpha-actinin is the primary protein that anchors actin filaments to the Z-line in the sarcomere.

Question 47

In the stages of sensory stimulus handling, the following is correct EXCEPT

Accepted Answer

Modality discrimination begins at the sensory organ — Pain is generally poorly localized compared to discriminative touch, which allows for precise localization.

Question 48

The pancreatic cells in control of body glucose

Accepted Answer

Forcing function — Pancreatic beta cells act as sensors for blood glucose levels, releasing insulin in response to high levels.

Question 49

Regarding erythrocyte production, all the following statements are true, Except:

Accepted Answer

It takes place normally in the bone marrow of long bones during adult life. — In adults, erythropoiesis primarily occurs in the red bone marrow of flat bones (e.g., sternum, pelvis, vertebrae, ribs), not typically the long bones (which are mainly fatty marrow).

Question 50

Pyrimidines

Accepted Answer

Are broken down to uric acid for excretion — Pyrimidines are cytosine, thymine (in DNA), and uracil (in RNA). Guanine is a purine.

EOY 2021 — Past Paper Questions & Answers

Questions, Answers & Explanations