Weekly Year 1: Enzymes, Vitamins and Minerals Exam - June...

Question 1

The primary disadvantage of anaerobic glycolysis during high-intensity muscle contractions is:

Accepted Answer

The rapid accumulation of lactate, leading to muscle fatigue. — Anaerobic glycolysis produces ATP rapidly but inefficiently, yielding only 2 ATP per glucose. A major disadvantage in high-intensity contractions is the production of lactic acid (lactate) as pyruvate is converted to regenerate NAD+, which lowers muscle pH and contributes to fatigue.

Question 2

Chylomicrons are lipoprotein particles primarily responsible for the transport of:

Accepted Answer

Dietary lipids (triglycerides and cholesterol) from the intestine to peripheral tissues. — Chylomicrons are synthesized in the intestinal cells and are specifically designed to transport dietary triglycerides and cholesterol absorbed from the gut to various tissues in the body, including adipose tissue and muscle.

Question 3

Phosphocreatine is used to store high-energy phosphate bonds primarily in which type of tissue?

Accepted Answer

Skeletal muscle and brain — Phosphocreatine (creatine phosphate) acts as a readily available energy reserve, especially in tissues with high and fluctuating energy demands like skeletal muscle and the brain. It rapidly donates its phosphate to ADP to form ATP during sudden bursts of activity.

Question 4

In the Cori cycle, lactate produced in muscles during anaerobic metabolism is transported to the liver and converted into:

Accepted Answer

Glucose, which can be returned to the muscles. — The Cori cycle (lactic acid cycle) involves the transport of lactate from the muscles to the liver. In the liver, lactate is converted back to pyruvate, which is then used in gluconeogenesis to synthesize glucose. This glucose can then be released back into the bloodstream for use by muscles or other tissues.

Question 5

Long-term heavy alcohol consumption can cause a range of detrimental effects. Which of the following is a direct consequence of alcohol's impact on liver metabolism?

Accepted Answer

Alcoholic fatty liver (steatosis) — Alcohol metabolism in the liver leads to an increase in NADH/NAD+ ratio, inhibiting fatty acid oxidation and promoting fatty acid synthesis, resulting in the accumulation of triglycerides in hepatocytes, known as alcoholic fatty liver or steatosis.

Question 6

Which of the following is a common symptom associated with alcohol withdrawal syndrome?

Accepted Answer

Seizures — Alcohol withdrawal syndrome results from the central nervous system's adaptation to chronic alcohol exposure. Symptoms often include tremors, anxiety, hallucinations, tachycardia, hypertension, and potentially life-threatening seizures and delirium tremens.

Question 7

There are many types of alcohol. Intoxication as we know it from alcoholic beverages is caused by:

Accepted Answer

Ethanol — Ethanol is the specific type of alcohol found in alcoholic beverages that causes the psychoactive and intoxicating effects. Methanol, isopropanol, and ethylene glycol are other types of alcohol that are highly toxic and not consumed for recreational purposes.

Question 8

Enzymes primarily involved in the transfer of methyl groups from one molecule to another are collectively classified as:

Accepted Answer

Transferases — Transferases are a class of enzymes that catalyze the transfer of functional groups (such as methyl, acyl, or glycosyl groups) from one molecule (the donor) to another (the acceptor). Methyltransferases are a specific type of transferase.

Question 9

All of the following are generally associated with the diverse functions of serotonin (5-hydroxytryptamine), EXCEPT:

Accepted Answer

Direct signaling for skeletal muscle contraction. — Serotonin is a widely acting neurotransmitter and hormone involved in many physiological processes including mood, appetite, sleep, and gut motility. Skeletal muscle contraction is primarily mediated by acetylcholine at the neuromuscular junction, not serotonin.

Question 10

Under aerobic conditions, the complete degradation of one molecule of glucose ultimately yields a net maximum of approximately how many ATP molecules?

Accepted Answer

30-32 — The complete aerobic oxidation of one glucose molecule, through glycolysis, the citric acid cycle, and oxidative phosphorylation, yields approximately 30-32 ATP molecules. The exact number can vary slightly depending on the shuttle system used to transport cytoplasmic NADH into the mitochondria.

Question 11

Synthesis of glutamine, a crucial amino acid for nitrogen transport and detoxification, usually occurs primarily in:

Accepted Answer

Skeletal muscle and brain — Glutamine is synthesized from glutamate and ammonia by the enzyme glutamine synthetase. This enzyme is highly active in skeletal muscle and the brain, where glutamine serves as a non-toxic carrier of ammonia to the liver and kidneys.

Question 12

The body's central metabolic clearinghouse, responsible for detoxifying various substances, synthesizing plasma proteins, and regulating nutrient levels in the blood, is known to be the:

Accepted Answer

Liver — The liver plays a central role in metabolism, processing nutrients absorbed from the gut, synthesizing numerous essential molecules, and detoxifying harmful substances, thus acting as the body's primary metabolic clearinghouse.

Question 13

Which enzyme class catalyzes reactions that break chemical bonds by adding water (hydrolysis)?

Accepted Answer

Hydrolases — Hydrolases are enzymes that catalyze the hydrolysis of a chemical bond, involving the addition of a water molecule. Examples include peptidases, lipases, and nucleases.

Question 14

In Michaelis-Menten kinetics, the Km (Michaelis constant) represents the substrate concentration at which the reaction rate is:

Accepted Answer

Half of the maximal rate (1/2 Vmax) — Km is a measure of the enzyme's affinity for its substrate. A lower Km indicates a higher affinity. By definition, Km is the substrate concentration at which the enzyme achieves half of its maximum reaction velocity (Vmax).

Question 15

A competitive inhibitor of an enzyme typically:

Accepted Answer

Increases the apparent Km without affecting Vmax. — Competitive inhibitors resemble the substrate and bind reversibly to the enzyme's active site, competing with the substrate. This increases the apparent Km (more substrate is needed to reach 1/2 Vmax) but does not change Vmax, as high substrate concentrations can outcompete the inhibitor.

Question 16

Allosteric regulation of an enzyme typically involves:

Accepted Answer

A molecule binding to a site distinct from the active site, causing a conformational change. — Allosteric regulation involves the binding of an effector molecule to an allosteric site (a site distinct from the active site) on the enzyme. This binding induces a conformational change that affects the enzyme's activity, either activating or inhibiting it.

Question 17

Many proteolytic enzymes are synthesized as inactive precursors called zymogens (proenzymes). The advantage of synthesizing enzymes as zymogens is:

Accepted Answer

To prevent premature or inappropriate enzyme activity. — Zymogens are inactive precursors of enzymes, particularly proteases, that must be cleaved to become active. This mechanism prevents the enzyme from digesting cellular components where it's synthesized and ensures that its activity is confined to specific locations or triggered by specific signals.

Question 18

Which of the following serves as a common coenzyme for dehydrogenases, accepting electrons during metabolic redox reactions?

Accepted Answer

NAD+ — NAD+ (nicotinamide adenine dinucleotide) is a crucial coenzyme that acts as an electron acceptor in many oxidative reactions (catalyzed by dehydrogenases) during metabolism, becoming reduced to NADH.

Question 19

Salivary amylase, an enzyme found in saliva, initiates the digestion of which macronutrient?

Accepted Answer

Carbohydrates — Salivary amylase (also known as ptyalin) begins the breakdown of complex carbohydrates (starches) into smaller oligosaccharides like maltose and dextrins in the mouth.

Question 20

Enzymes increase the rate of biochemical reactions by:

Accepted Answer

Decreasing the activation energy of the reaction. — Enzymes are biological catalysts. They speed up reactions by providing an alternative reaction pathway with a lower activation energy, making it easier for the reactants to reach the transition state. They do not change the overall Gibbs free energy change or the equilibrium of a reaction.

Question 21

A deficiency in Vitamin B1 (Thiamine) is associated with which neurological condition?

Accepted Answer

Beriberi — Thiamine (Vitamin B1) is a crucial cofactor for several enzymes involved in carbohydrate metabolism. Its deficiency leads to Beriberi, characterized by neurological (dry beriberi) and cardiovascular (wet beriberi) symptoms.

Question 22

Vitamin B2 (Riboflavin) serves as a precursor for which important coenzymes involved in redox reactions?

Accepted Answer

FAD and FMN — Riboflavin is a component of the coenzymes Flavin Adenine Dinucleotide (FAD) and Flavin Mononucleotide (FMN), which are essential electron carriers in various metabolic pathways, including the electron transport chain.

Question 23

Pellagra, a disease characterized by dermatitis, diarrhea, and dementia, is caused by a deficiency of which vitamin?

Accepted Answer

Vitamin B3 (Niacin) — Pellagra is caused by a severe deficiency of Niacin (Vitamin B3) or its precursor, tryptophan. Niacin is a component of NAD+ and NADP+, critical coenzymes in many metabolic reactions.

Question 24

Vitamin B6 (Pyridoxine) in its active form (pyridoxal phosphate) is a coenzyme primarily involved in which type of metabolic reactions?

Accepted Answer

Amino acid metabolism (transamination, decarboxylation) — Pyridoxal phosphate (PLP), the active form of Vitamin B6, is a versatile coenzyme for numerous enzymes involved in amino acid metabolism, including transamination, decarboxylation, and racemization reactions.

Question 25

Which of the following conditions is a characteristic symptom of Vitamin B12 (Cobalamin) deficiency?

Accepted Answer

Megaloblastic anemia — Vitamin B12 is essential for DNA synthesis and the proper functioning of the nervous system. Its deficiency impairs red blood cell maturation, leading to megaloblastic anemia, and can also cause neurological damage.

Question 26

A patient presents with bleeding gums, impaired wound healing, and petechiae. These symptoms are most consistent with a deficiency in which vitamin?

Accepted Answer

Vitamin C — These symptoms are classic signs of scurvy, caused by a deficiency of Vitamin C (Ascorbic Acid). Vitamin C is crucial for collagen synthesis, acting as a cofactor for hydroxylase enzymes involved in forming stable collagen helices.

Question 27

Vitamin A (Retinol) is essential for:

Accepted Answer

Vision, immune function, and epithelial cell maintenance — Vitamin A is critical for several physiological processes, including the formation of rhodopsin (a photopigment in the retina) for vision, maintaining healthy epithelial tissues, and supporting immune function.

Question 28

A deficiency in Vitamin D can lead to which condition in children?

Accepted Answer

Rickets — Vitamin D is essential for calcium and phosphate homeostasis and bone mineralization. In children, Vitamin D deficiency leads to rickets, characterized by defective bone growth and skeletal deformities. In adults, it leads to osteomalacia.

Question 29

Vitamin K is primarily known for its essential role in:

Accepted Answer

Blood coagulation — Vitamin K is a fat-soluble vitamin crucial for the synthesis of several blood clotting factors (e.g., factors II, VII, IX, X) in the liver, by acting as a cofactor for gamma-glutamyl carboxylase.

Question 30

Compared to water-soluble vitamins, fat-soluble vitamins generally:

Accepted Answer

Are stored in the body, increasing the risk of toxicity. — Fat-soluble vitamins (A, D, E, K) are absorbed with dietary fats, stored in the body's fatty tissues and liver, and are not easily excreted. This storage capacity means they can accumulate to toxic levels with excessive intake, unlike water-soluble vitamins which are generally excreted if consumed in excess.

Question 31

Which major mineral is crucial for bone and tooth structure, muscle contraction, nerve transmission, and blood clotting?

Accepted Answer

Calcium — Calcium is the most abundant mineral in the body, primarily forming bones and teeth. It also plays vital roles as an intracellular messenger, in muscle contraction, nerve impulse transmission, and blood coagulation.

Question 32

Microcytic, hypochromic anemia is a classic manifestation of a deficiency in which trace mineral?

Accepted Answer

Iron — Iron is an essential component of hemoglobin, which carries oxygen in red blood cells. Iron deficiency leads to a reduction in hemoglobin synthesis, resulting in microcytic (small) and hypochromic (pale) red blood cells, a characteristic of iron-deficiency anemia.

Question 33

Sodium (Na+) is a primary electrolyte that plays a critical role in all of the following, EXCEPT:

Accepted Answer

Constituting the backbone of DNA and RNA. — Sodium is vital for extracellular fluid volume, blood pressure regulation, nerve impulse conduction, and muscle contraction. Phosphate and deoxyribose/ribose form the backbone of DNA and RNA, not sodium.

Question 34

Iodine is an essential trace mineral primarily required for the synthesis of:

Accepted Answer

Thyroid hormones — Iodine is a key component of thyroid hormones (thyroxine, T4, and triiodothyronine, T3), which are vital for regulating metabolism, growth, and development. Iodine deficiency can lead to goiter and hypothyroidism.

Question 35

Which trace mineral functions as a cofactor for numerous enzymes, supports immune function, and is involved in wound healing?

Accepted Answer

Zinc — Zinc is an essential trace mineral that acts as a cofactor for over 300 enzymes involved in diverse metabolic processes. It plays crucial roles in immune function, wound healing, DNA synthesis, and cell division.

Weekly Year 1: Enzymes, Vitamins and Minerals Exam - June...

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