MLPAO Basic Biology, Anatomy, and Physiology Questions and Answers 2 — Questions and Answers
Question 1: Which organelle is responsible for ATP production through oxidative phosphorylation in human cells?
- Nucleus
- Ribosome
- Mitochondria (Correct answer)
- Golgi apparatus
Correct answer: Mitochondria
Mitochondria are the sites of oxidative phosphorylation, producing the majority of cellular ATP through the electron transport chain and the citric acid cycle.
Mitochondria contain the enzymes for the citric acid (Krebs) cycle in their matrix and the electron transport chain complexes in the inner mitochondrial membrane. Through oxidative phosphorylation, mitochondria produce approximately 30-32 ATP per glucose molecule. This process requires oxygen, explaining why cells in tissues with high metabolic demands (heart, brain, skeletal muscle) have the most mitochondria. In laboratory medicine, mitochondrial dysfunction is relevant to understanding metabolic disorders. LDH and AST, which are released from cells during damage, are cytoplasmic and mitochondrial enzymes used as markers of cellular injury.
Question 2: In the ABO blood group system, a type B individual has which antigens and antibodies?
- B antigens on RBCs and anti-A antibodies in serum (Correct answer)
- A antigens on RBCs and anti-B antibodies in serum
- Both A and B antigens and no antibodies
- No antigens and both anti-A and anti-B antibodies
Correct answer: B antigens on RBCs and anti-A antibodies in serum
A type B individual has B antigens on their red blood cells and anti-A antibodies (isohemagglutinins) in their plasma, following Landsteiner's rule.
Landsteiner's rule states that individuals naturally produce antibodies against the ABO antigens absent from their red blood cells. Therefore: Type A has A antigens and anti-B; Type B has B antigens and anti-A; Type AB has both A and B antigens and no ABO antibodies; Type O has no ABO antigens and both anti-A and anti-B. This is fundamental to transfusion medicine. Transfusing incompatible ABO blood causes a life-threatening acute hemolytic transfusion reaction. The ABO system is the most important blood group system for transfusion compatibility and organ transplantation in Ontario clinical practice.
Question 3: What is the primary function of albumin in human plasma?
- Oxygen transport
- Coagulation factor synthesis
- Maintenance of oncotic pressure and protein transport (Correct answer)
- Immune defense
Correct answer: Maintenance of oncotic pressure and protein transport
Albumin is the most abundant plasma protein and serves to maintain colloid oncotic pressure (preventing fluid from leaking out of blood vessels) and to transport various substances including hormones, drugs, and bilirubin.
Albumin, synthesized by the liver, constitutes approximately 60% of total plasma protein and has two primary functions: (1) Colloid oncotic pressure — albumin accounts for approximately 75-80% of plasma oncotic pressure, keeping fluid within the vascular space. Low albumin (hypoalbuminemia) causes edema and ascites as fluid leaks into tissues. (2) Transport — albumin binds and carries fatty acids, bilirubin, calcium, medications (warfarin, phenytoin, aspirin), thyroid hormones, and other substances. Laboratory measurement of albumin is used to assess nutritional status, liver synthetic function, and to interpret calcium results (since approximately 40-45% of calcium is albumin-bound.
Question 4: During aerobic respiration, what molecule is the final electron acceptor in the electron transport chain?
- Carbon dioxide
- Glucose
- Oxygen (Correct answer)
- NAD+
Correct answer: Oxygen
Oxygen is the final electron acceptor in the electron transport chain, combining with electrons and protons to form water (Hâ‚‚O) at Complex IV (cytochrome c oxidase).
In aerobic respiration, NADH and FADH2 donate electrons to the electron transport chain located in the inner mitochondrial membrane. Electrons pass through Complexes I, II, III, and IV, with proton pumping creating a gradient that drives ATP synthase (Complex V). At Complex IV (cytochrome c oxidase), the electrons reduce molecular oxygen (O2) to water. This is why aerobic respiration absolutely requires oxygen. In anaerobic conditions, pyruvate is converted to lactate (lactic acid), which can be measured in the laboratory as a marker of tissue hypoxia. Elevated lactate is associated with sepsis, shock, and mitochondrial disorders.
Question 5: The nephron is the functional unit of which organ?
- Liver
- Pancreas
- Lung
- Kidney (Correct answer)
Correct answer: Kidney
The nephron is the structural and functional unit of the kidney. Each kidney contains approximately 1 million nephrons that filter blood, reabsorb nutrients, and produce urine.
Each kidney contains approximately 1 million nephrons, each consisting of a glomerulus (filtration unit) and renal tubule (reabsorption and secretion). The process of urine formation: (1) Glomerular filtration — blood is filtered under pressure through the glomerular capillaries, creating an ultrafiltrate; (2) Tubular reabsorption — glucose, amino acids, sodium, water, and other substances are reclaimed; (3) Tubular secretion — additional waste products (creatinine, drugs, hydrogen ions) are secreted. Urine analysis (urinalysis) reflects nephron function. Markers of kidney function including creatinine, BUN, and cystatin C are fundamental tests in Ontario clinical chemistry laboratories.
Question 6: Which hormone, produced by the beta cells of the pancreatic islets of Langerhans, promotes cellular glucose uptake?
- Glucagon
- Insulin (Correct answer)
- Cortisol
- Epinephrine
Correct answer: Insulin
Insulin, produced by pancreatic beta cells, promotes glucose uptake by cells (especially muscle and adipose tissue) and decreases blood glucose levels after meals.
Insulin is a peptide hormone synthesized and secreted by the beta cells of the islets of Langerhans in the pancreas. Its primary action is to lower blood glucose by: (1) Stimulating GLUT4 transporter expression, enabling glucose uptake in muscle and adipose tissue; (2) Promoting glycogen synthesis in liver and muscle; (3) Inhibiting gluconeogenesis and glycogenolysis in the liver. Insulin deficiency (Type 1 DM) or resistance (Type 2 DM) results in hyperglycemia. Laboratory assessment includes fasting glucose, HbA1c, insulin levels, C-peptide, and glucose tolerance testing. Glucagon (alpha cells) has the opposite effect, raising blood glucose.
MLPAO Basic Biology, Anatomy, and Physiology Questions and Answers 2
Which organelle is responsible for ATP production through oxidative phosphorylation in human cells?