6051 to 6100 MCQs for Lab Technician and Technologist Exam Preparation
5000 Plus MCQs for Lab Technician and Technologists are designed to test the knowledge and proficiency of laboratory professionals who work in the field of clinical laboratory science. These questions cover a wide range of topics related to laboratory science, including anatomy, physiology, microbiology, chemistry, and hematology.
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Questions 6051 to 6100
A diet containing this fat is helpful in lowering the blood cholesterol level.
- a) Unsaturated
- b) Saturated
- c) Vitamin enriched
- d) Refined
Explanation:
Unsaturated fats (found in olive oil, nuts, and fish) are considered healthy fats. They help improve blood cholesterol levels, ease inflammation, and stabilize heart rhythms.
Why other options are incorrect:
Why other options are incorrect:
- • Saturated: These fats can raise the level of LDL (bad) cholesterol in your blood, increasing the risk of heart disease.
- • Vitamin enriched: While healthy, this refers to nutritional additives rather than a specific category of fat that manages cholesterol.
- • Refined: Refined fats/oils are often processed and may contain trans-fats, which are harmful to cardiovascular health.
Phospholipase A2 is an enzyme which removes a fatty acid residue from lecithin to form
- a) Lecithin fragments
- b) Phosphotidic acid
- c) Glyceryl phosphate
- d) Lysolecithin
Explanation:
Phospholipase A2 specifically catalyzes the hydrolysis of the fatty acid ester bond at the sn-2 position of glycerophospholipids (like lecithin/phosphatidylcholine), resulting in the formation of a free fatty acid and lysophosphatidylcholine, commonly known as Lysolecithin.
Why other options are incorrect:
Why other options are incorrect:
- • Lecithin fragments: This is a vague term and not the specific biochemical product of this reaction.
- • Phosphotidic acid: This is a precursor in the synthesis of phospholipids, not the product of PLA2 hydrolysis.
- • Glyceryl phosphate: This is the backbone structure, but it is not the immediate product formed by the removal of a single fatty acid by PLA2.
Pancreatic lipase is an enzyme which hydrolyzes fats. It acts as a/an
- a) Peptidase
- b) Hydrolase
- c) Carbohydrase
- d) Dehydrogenase
Explanation:
Pancreatic lipase is a member of the hydrolase class of enzymes. Hydrolases catalyze the hydrolysis (breaking down using water) of various chemical bonds, including the ester bonds found in triglycerides.
Why other options are incorrect:
Why other options are incorrect:
- • Peptidase: Enzymes that specifically break down proteins into peptides or amino acids.
- • Carbohydrase: Enzymes that break down carbohydrates (e.g., amylase).
- • Dehydrogenase: Enzymes that catalyze the removal of hydrogen atoms from a substrate (involved in redox reactions).
This interferes with cholesterol absorption
- a) Lipoprotein lipase
- b) Creatinase
- c) 7-dehydrocholesterol
- d) β-sitosterol
Explanation:
β-sitosterol is a plant sterol (phytosterol) that is structurally similar to cholesterol. Because of this similarity, it competes with dietary cholesterol for absorption in the small intestine, thereby reducing the amount of cholesterol that enters the bloodstream.
Why other options are incorrect:
Why other options are incorrect:
- • Lipoprotein lipase: An enzyme that breaks down triglycerides in lipoproteins, not involved in cholesterol absorption interference.
- • Creatinase: An enzyme involved in the metabolism of creatine.
- • 7-dehydrocholesterol: A precursor of cholesterol that is converted into Vitamin D in the skin upon UV exposure; it is not an inhibitor of absorption.
The carbon chain of fatty acids is shortened by 2 carbon atoms at a time. This involves successive reactions catalysed by 4-enzymes. These act in the following order:
- a) Acyl CoA dehydrogenase, enoyl hydrase, β-OH acyl CoA dehydrogenase, thiolase
- b) Acyl CoA dehydrogenase, thiolase, enoyl hydrase, β-OH acyl CoA dehydrogenase
- c) Acyl CoA dehydrogenase, thiolase, enoyl hydrase, β-OH acyl CoA dehydrogenase
- d) Enoyl hydrase, β-OH acyl CoA dehydrogenase, acyl CoA dehydrogenase, thiolase
Explanation:
The β-oxidation of fatty acids follows a repeating four-step cycle:
Key Insight: Each cycle effectively removes a two-carbon unit in the form of Acetyl-CoA, shortening the original fatty acid chain.
- Oxidation: Catalyzed by Acyl CoA dehydrogenase.
- Hydration: Catalyzed by Enoyl-CoA hydratase (enoyl hydrase).
- Oxidation: Catalyzed by β-hydroxyacyl CoA dehydrogenase.
- Thiolysis: Catalyzed by Thiolase.
Key Insight: Each cycle effectively removes a two-carbon unit in the form of Acetyl-CoA, shortening the original fatty acid chain.
Acyl carrier protein is involved in the synthesis of
- a) Protein
- b) Glycogen
- c) Fatty acid outside the mitochondria
- d) Fatty acid in the mitochondria
Explanation:
The Acyl Carrier Protein (ACP) is a vital component of the fatty acid synthase complex. Fatty acid synthesis (lipogenesis) occurs primarily in the cytosol (outside the mitochondria) of the cell.
Why other options are incorrect:
Why other options are incorrect:
- • Protein/Glycogen: ACP is specific to lipid biosynthesis, not the synthesis of proteins or glycogen.
- • Fatty acid in the mitochondria: The mitochondria are primarily the site of fatty acid degradation (beta-oxidation), whereas the synthesis occurs in the cytoplasm.
1 molecule of palmitic acid on total oxidation to CO2 will yield molecules of ATP (as high energy bonds):
- a) 129
- b) 154
- c) 83
- d) 25
Explanation:
Palmitic acid (16 carbons) undergoes 7 cycles of β-oxidation, producing 8 Acetyl-CoA, 7 NADH, and 7 FADH2.
Why other options are incorrect:
- • 8 Acetyl-CoA yield: 80 ATP (via TCA cycle)
- • 7 FADH2 yield: 10.5 ATP
- • 7 NADH yield: 17.5 ATP
- • Minus 2 ATP for activation: -2 ATP
- • Total: 106 to 129 ATP (Depending on the P/O ratio used in textbooks; 129 is the standard figure in many biochemistry curricula).
Why other options are incorrect:
- The other values listed do not align with the standard stoichiometric calculations for the complete aerobic oxidation of a 16-carbon fatty acid.
HMG CoA is formed in the metabolism of
- a) Cholesterol, ketones and leucine
- b) Cholesterol, fatty acid and Leucine
- c) Lysine, Leucine and Isoleucine
- d) Ketones, Leucine and Lysine
Explanation:
3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) is a critical metabolic intermediate. It is formed during:
Why other options are incorrect:
- • Cholesterol Biosynthesis: Where HMG-CoA reductase converts it to mevalonate.
- • Ketogenesis: Where it is synthesized in the liver to produce ketone bodies.
- • Leucine Catabolism: Where leucine degradation leads to the formation of HMG-CoA.
Why other options are incorrect:
- While other amino acids like Lysine and Isoleucine are ketogenic, HMG-CoA is specifically defined as the key intermediate for the combination of cholesterol, ketone synthesis, and leucine catabolism.
NADPH is produced when this enzyme acts
- a) Pyruvate dehydrogenase
- b) Malic enzyme
- c) Succinate dehydrogenase
- d) Malate dehydrogenase
Explanation:
The Malic enzyme (malate dehydrogenase (oxaloacetate-decarboxylating)) catalyzes the oxidative decarboxylation of malate to pyruvate, coupled with the reduction of NADP+ to NADPH. This is a significant source of NADPH in the cytosol, which is essential for fatty acid biosynthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Pyruvate dehydrogenase: Uses NAD+ to produce NADH.
- • Succinate dehydrogenase: Uses FAD to produce FADH2 (in the TCA cycle).
- • Malate dehydrogenase: Involved in the TCA cycle and malate-aspartate shuttle; it uses NAD+ to produce NADH.
As a result of each oxidation cycle, a long chain fatty acid is cleaved to give
- a) An acid with 3-carbons less and propionyl CoA
- b) An acid with 2-carbons less and acetyl CoA
- c) An acid with 1-carbon less and formyl CoA
- d) An acid with 4-carbons and butyryl CoA
Explanation:
During the β-oxidation of fatty acids, each cycle of four reactions removes a two-carbon unit from the carboxyl end of the fatty acid chain. This results in the release of one molecule of Acetyl-CoA and a remaining fatty acyl-CoA molecule that is 2 carbons shorter than the original.
Why other options are incorrect:
Why other options are incorrect:
- • 3-carbon/Propionyl CoA: This occurs in the oxidation of odd-chain fatty acids during the final cycle, not in every standard cycle.
- • 1-carbon: Beta-oxidation does not remove carbons one at a time.
- • 4-carbon: This does not describe the general cleavage process of the fatty acid chain.
Liposomes are
- a) Lipid bilayered
- b) Water in the middle
- c) Carriers of drugs
- d) All of these
Explanation:
Liposomes are spherical vesicles that possess at least one lipid bilayer. They are composed of phospholipids which surround an aqueous (water) core. Due to their ability to encapsulate both hydrophobic and hydrophilic substances, they are widely used as effective carriers for targeted drug delivery in medicine.
Summary: Since all three statements (bilayered structure, aqueous core, and drug delivery function) are correct descriptions of liposomes, “All of these” is the correct choice.
Summary: Since all three statements (bilayered structure, aqueous core, and drug delivery function) are correct descriptions of liposomes, “All of these” is the correct choice.
Long chain fatty acyl CoA esters are transported across the mitochondrial membrane by
- a) cAMP
- b) Prostaglandin
- c) Carnitine
- d) Choline
Explanation:
Long-chain fatty acids cannot cross the inner mitochondrial membrane on their own. They must be converted into acyl-carnitine by the enzyme Carnitine Palmitoyltransferase I (CPT-I). The molecule is then transported across the membrane by a translocase and converted back to fatty acyl-CoA inside the matrix. This process is known as the Carnitine Shuttle.
Why other options are incorrect:
Why other options are incorrect:
- • cAMP: A secondary messenger in cell signaling, not involved in transport.
- • Prostaglandin: A lipid-derived signaling molecule.
- • Choline: A nutrient used to synthesize phospholipids like lecithin and the neurotransmitter acetylcholine.
The acetyl CoA formed on β-oxidation of all long chain fatty acids is metabolized under normal circumstances to
- a) CO2 and water
- b) Cholesterol
- c) Fatty acids
- d) Ketone bodies
Explanation:
Under normal physiological conditions, the Acetyl-CoA produced by β-oxidation enters the Tricarboxylic Acid (TCA) cycle (also known as the Citric Acid cycle). Through the TCA cycle and the subsequent Electron Transport Chain, Acetyl-CoA is completely oxidized to CO2, water, and ATP.
Why other options are incorrect:
Why other options are incorrect:
- • Ketone bodies: These are formed primarily when the TCA cycle is overwhelmed or undersupplied with oxaloacetate (e.g., during starvation or uncontrolled diabetes), not under “normal circumstances.”
- • Cholesterol/Fatty acids: These are synthetic pathways (anabolic) that occur when energy levels are high, whereas β-oxidation is a catabolic process meant to generate energy.
Very low density lipoproteins (VLDL) are relatively rich in
- a) Cholesterol
- b) Triacyl glycerol
- c) Free fatty acids
- d) Phospholipids
Explanation:
Very low-density lipoproteins (VLDL) are synthesized by the liver to transport endogenous lipids. They are characterized by a very high content of triacylglycerols (triglycerides), which accounts for about 50-60% of their total mass, compared to smaller amounts of cholesterol, cholesterol esters, and phospholipids.
Why other options are incorrect:
Why other options are incorrect:
- • Cholesterol: This is the primary lipid component in LDL (Low-Density Lipoprotein).
- • Free fatty acids: These are primarily transported in the blood bound to albumin, not within VLDL.
- • Phospholipids: While present in the shell of all lipoproteins, they are not the primary lipid content of VLDL.
Neutral fat is stored in
- a) Liver
- b) Pancreas
- c) Adipose tissue
- d) Brain
Explanation:
Adipose tissue is the primary specialized connective tissue in the body designed for the storage of neutral fat (triacylglycerols). Adipocytes (fat cells) store energy in the form of droplets of triglycerides, which are mobilized when the body requires energy.
Why other options are incorrect:
Why other options are incorrect:
- • Liver: While the liver plays a major role in lipid metabolism (synthesis and processing), it does not store fat as its primary function; excessive accumulation here leads to fatty liver disease.
- • Pancreas: Primarily an endocrine and digestive organ, not a storage site for fat.
- • Brain: Contains high concentrations of lipids (myelin), but these are structural, not energy-storage “neutral fat.”
A pathway that requires NADPH as a cofactor is
- a) Fatty acid oxidation
- b) Extra mitochondrial denovo fatty acid synthesis
- c) Ketone bodies formation
- d) Glycogenesis
Explanation:
De novo fatty acid synthesis (which occurs in the cytosol/extra-mitochondrial space) requires NADPH as a reducing agent. Specifically, the reduction steps catalyzed by β-ketoacyl reductase and enoyl reductase utilize NADPH to convert the growing fatty acid chain into a saturated hydrocarbon chain.
Why other options are incorrect:
Why other options are incorrect:
- • Fatty acid oxidation: Utilizes NAD+ and FAD as oxidizing agents, not NADPH.
- • Ketone bodies formation: Primarily involves condensation and cleavage reactions using CoA-linked intermediates; it does not require NADPH.
- • Glycogenesis: The process of glycogen synthesis requires UTP (uridine triphosphate), not NADPH.
The ‘Committed step’ in the biosynthesis of cholesterol from acetyl CoA is
- a) Formation of acetoacetyl CoA from acetyl CoA
- b) Formation of mevalonate from HMG CoA
- c) Formation of HMG CoA from acetyl CoA and acetoacetyl CoA
- d) Formation of squalene by squalene synthetase
Explanation:
The reduction of HMG-CoA to mevalonate, catalyzed by the enzyme HMG-CoA reductase, is the rate-limiting and committed step in cholesterol biosynthesis. This reaction is the primary site of regulation (and the target for “statin” drugs) because it is the point of no return in the pathway toward cholesterol.
Why other options are incorrect:
Why other options are incorrect:
- • a, c: These are initial condensation steps that can also be used for other metabolic pathways, such as ketone body synthesis.
- • d: While squalene synthesis is an important downstream step, it is not the primary regulatory “committed” step of the overall pathway.
In β-Oxidation of fatty acids, which of the following are utilized as coenzymes?
- a) NAD+ and NADP+
- b) FADH2 and NADH + H+
- c) FAD and FMN
- d) FAD and NAD+
Explanation:
The β-oxidation cycle involves two oxidative steps:
Why other options are incorrect:
- 1. The first step, catalyzed by Acyl-CoA dehydrogenase, uses FAD as a coenzyme (reducing it to FADH2).
- 2. The third step, catalyzed by β-hydroxyacyl-CoA dehydrogenase, uses NAD+ as a coenzyme (reducing it to NADH + H+).
Why other options are incorrect:
- • FADH2 and NADH: These are the products of the reaction, not the coenzymes that are utilized in their oxidized form.
- • NADP+ and FMN: These are not the coenzymes used in the standard mitochondrial β-oxidation pathway.
The most important source of reducing equivalents (NADPH) for fatty acid synthesis in the liver is
- a) Glycolysis
- b) HMP-Shunt
- c) TCA cycle
- d) Uronic acid pathway
Explanation:
The Hexose Monophosphate (HMP) Shunt (also known as the Pentose Phosphate Pathway) is the primary metabolic pathway responsible for generating NADPH. Since fatty acid synthesis requires NADPH as a key reducing agent, the HMP shunt is the most important source of these equivalents in the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Glycolysis & TCA Cycle: These pathways primarily generate NADH and ATP, not NADPH.
- • Uronic acid pathway: Primarily involved in the synthesis of glucuronic acid and Vitamin C (in some species), not significantly involved in providing NADPH for lipogenesis.
All of the following tissues are capable of using ketone bodies except
- a) Brain
- b) Renal cortex
- c) R.B.C.
- d) Cardiac muscle
Explanation:
Red Blood Cells (R.B.C.) cannot use ketone bodies because they lack mitochondria. Ketone body oxidation requires the enzymes of the TCA cycle and beta-oxidation, which are housed within the mitochondria.
Why other options are incorrect:
Why other options are incorrect:
- • Brain: Can adapt to use ketone bodies during prolonged fasting or starvation.
- • Renal cortex & Cardiac muscle: These tissues are rich in mitochondria and rely heavily on the oxidation of fatty acids and ketone bodies for their energy requirements.
The major source of cholesterol in arterial smooth muscle cells is from
- a) IDL
- b) LDL
- c) HDL
- d) Chylomicrons
Explanation:
Low-Density Lipoprotein (LDL) is the primary cholesterol-carrying lipoprotein in the blood. Arterial smooth muscle cells and macrophages take up oxidized LDL via scavenger receptors, leading to cholesterol accumulation, which is a key process in the formation of atherosclerotic plaques.
Why other options are incorrect:
Why other options are incorrect:
- • HDL: Known as “good cholesterol” because it performs reverse cholesterol transport, taking cholesterol away from tissues back to the liver.
- • Chylomicrons: Primarily transport dietary triglycerides from the intestines.
- • IDL: An intermediate lipoprotein that is usually converted into LDL; while it can contribute, LDL is the major pathological source.
Ketone bodies are synthesized from fatty acid oxidation products by which of the following organs?
- a) Liver
- b) Skeletal muscles
- c) Kidney
- d) Brain
Explanation:
The liver is the primary site of ketogenesis (the synthesis of ketone bodies like acetoacetate, beta-hydroxybutyrate, and acetone). When there is a high rate of fatty acid oxidation, the liver produces these ketone bodies to serve as an alternative energy fuel for peripheral tissues (like the heart and brain) during periods of fasting or low carbohydrate intake.
Why other options are incorrect:
Why other options are incorrect:
- • Skeletal muscle, Kidney, & Brain: While these tissues can utilize ketone bodies for energy, they lack the specific enzymatic machinery required to synthesize them.
Chain elongation of fatty acids occurring in mammalian liver takes place in which of the following subcellular fractions of the cell?
- a) Nucleus
- b) Ribosomes
- c) Lysosomes
- d) Microsomes
Explanation:
In mammalian liver cells, the elongation of pre-existing long-chain fatty acids occurs primarily in the microsomal fraction (the smooth endoplasmic reticulum). This process utilizes Malonyl-CoA as the two-carbon donor and NADPH as the reducing agent.
Why other options are incorrect:
Why other options are incorrect:
- • Nucleus/Ribosomes: These are involved in genetic material storage/processing and protein synthesis, respectively.
- • Lysosomes: Primarily involved in cellular waste degradation and autophagy, not fatty acid elongation.
Which of the following cofactors or their derivatives must be present for the conversion of acetyl CoA to malonyl CoA in extramitochondrial fatty acid synthesis?
- a) Biotin
- b) FAD
- c) FMN
- d) ACP
Explanation:
The conversion of Acetyl-CoA to Malonyl-CoA is catalyzed by the enzyme Acetyl-CoA Carboxylase (ACC). This enzyme is a biotin-dependent carboxylase; it requires biotin (Vitamin B7) as a covalently bound prosthetic group to carry the activated carbon dioxide (as bicarbonate) to the acetyl-CoA substrate.
Why other options are incorrect:
Why other options are incorrect:
- • FAD/FMN: These are flavin coenzymes involved in redox reactions (like those in β-oxidation), not in carboxylation.
- • ACP (Acyl Carrier Protein): While ACP is a vital component of the fatty acid synthase complex, it is not the cofactor required for the initial formation of malonyl-CoA by the ACC enzyme.
Which of the following statement regarding β-oxidation is true?
- a) Requires β-ketoacyl CoA as a substrate
- b) Forms CoA thioesters
- c) Requires GTP for its activity
- d) Yields acetyl CoA as a product
Explanation:
β-oxidation is the metabolic process by which fatty acid molecules are broken down in the mitochondria to generate acetyl-CoA, which then enters the citric acid cycle.
Why other options are incorrect:
Why other options are incorrect:
- • Requires β-ketoacyl CoA: This is an intermediate product within the cycle, not the starting substrate.
- • Forms CoA thioesters: While the process involves thioesters, it is not the defining true statement compared to the final product formation.
- • Requires GTP: β-oxidation uses ATP for the initial activation of fatty acids and produces NADH/FADH2, not GTP.
All statements regarding 3-OH-3 methyl glutaryl CoA are true except:
- a) It is formed in the cytoplasm
- b) Required in ketogenesis
- c) Involved in synthesis of Fatty acid
- d) An intermediate in cholesterol biosynthesis
Explanation:
3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) is a critical intermediate in cholesterol synthesis (occurring in the cytoplasm) and ketogenesis (occurring in the mitochondria). It is not involved in fatty acid synthesis, which primarily utilizes Malonyl-CoA.
Why other options are correct (as statements):
Why other options are correct (as statements):
- • Formed in the cytoplasm: HMG-CoA reductase (the rate-limiting step for cholesterol) is cytosolic.
- • Required in ketogenesis: HMG-CoA synthase is required for the production of ketone bodies in the liver mitochondria.
- • Intermediate in cholesterol: It is the precursor that is reduced to mevalonate in the cholesterol pathway.
Which of the following lipoproteins would contribute to a measurement of plasma cholesterol in a normal individual following a 12 hr fast?
- a) Chylomicrons
- b) VLDL
- c) Both VLDL and LDL
- d) LDL
Explanation:
After a 12-hour fast, chylomicrons (which transport dietary lipids) are cleared from the plasma. Therefore, the measured plasma cholesterol consists primarily of cholesterol contained within VLDL (Very Low-Density Lipoprotein) and LDL (Low-Density Lipoprotein).
Why other options are incorrect:
Why other options are incorrect:
- • Chylomicrons: These are only present in the blood shortly after a fat-containing meal; they disappear after an overnight fast.
- • VLDL only / LDL only: Both particles contain cholesterol. While LDL carries the majority of circulating cholesterol, VLDL also contributes significantly to the total plasma cholesterol pool.
All the following statements regarding ketone bodies are true except:
- a) They may result from starvation
- b) They are formed in kidneys
- c) They include acetoacetic acid and acetone
- d) They may be excreted in urine
Explanation:
Ketone bodies (acetoacetate, beta-hydroxybutyrate, and acetone) are synthesized primarily in the liver (specifically in the mitochondria of hepatocytes), not the kidneys.
Why other options are correct (as statements):
Why other options are correct (as statements):
- • Starvation: During prolonged fasting or starvation, the body shifts to burning fat, increasing ketone body production.
- • Composition: Acetoacetic acid, acetone, and beta-hydroxybutyrate are the three classic ketone bodies.
- • Excretion: When blood levels of ketone bodies are high (ketosis), they are filtered by the kidneys and excreted in the urine (ketonuria).
In synthesis of Triglyceride from α-Glycero phosphate and acetyl CoA, the first intermediate formed is:
- a) β-diacyl glycerol
- b) Acyl carnitine
- c) Monoacyl glycerol
- d) Phosphatidic acid
Explanation:
The synthesis of triglycerides begins with the esterification of α-glycerophosphate with two molecules of fatty acyl-CoA. The first step produces lysophosphatidic acid, and the second step produces phosphatidic acid, which serves as a central intermediate.
Why other options are incorrect:
Why other options are incorrect:
- • β-diacyl glycerol: This is formed later in the pathway by the dephosphorylation of phosphatidic acid.
- • Acyl carnitine: This is an intermediate in fatty acid transport into the mitochondria for oxidation, not triglyceride synthesis.
- • Monoacyl glycerol: This is a key intermediate in the intestinal absorption pathway of triglycerides, but not in the α-glycerophosphate pathway.
During each cycle of β-oxidation of fatty acid, all the following compounds are generated except:
- a) NADH
- b) H2O
- c) FAD
- d) Acyl CoA
Explanation:
Each cycle of β-oxidation involves the oxidation of the β-carbon, which produces one FADH₂ (from FAD), one NADH (from NAD+), one acetyl-CoA, and one shortened Acyl-CoA. Water (H2O) is also utilized and produced in the hydration steps of the cycle. FAD is a cofactor/substrate that gets reduced, not a generated product.
Why other options are incorrect (as exceptions):
Why other options are incorrect (as exceptions):
- • NADH: Generated during the oxidation of L-3-hydroxyacyl-CoA.
- • H2O: Involved in the hydration of enoyl-CoA to hydroxyacyl-CoA.
- • Acyl CoA: The fatty acid chain is released as an Acyl-CoA that is two carbons shorter than the previous one.
β-Oxidation of odd-carbon fatty acid chain produces:
- a) Succinyl CoA
- b) Propionyl CoA
- c) Acetyl CoA
- d) Malonyl CoA
Explanation:
During the β-oxidation of odd-carbon fatty acids, the final cycle yields one molecule of Propionyl-CoA (a 3-carbon unit) along with several molecules of Acetyl-CoA. Propionyl-CoA is subsequently converted into Succinyl-CoA to enter the citric acid cycle.
Why other options are less appropriate:
Why other options are less appropriate:
- • Acetyl CoA: While produced, it is also the product of even-carbon fatty acids; Propionyl-CoA is the specific end-product of odd-chain oxidation.
- • Succinyl CoA: This is a downstream metabolite produced *after* the conversion of Propionyl-CoA, not directly from the β-oxidation cycle.
- • Malonyl CoA: This is an intermediate in fatty acid *synthesis*, not breakdown.
Brown adipose tissue is characterized by which of the following?
- a) Present in large quantities in adult humans
- b) Mitochondrial content higher than white adipose tissue
- c) Oxidation and phosphorylation are tightly coupled
- d) Absent in hibernating animals
Explanation:
Brown adipose tissue (BAT) contains a high number of mitochondria, which are rich in iron-containing cytochromes. Unlike white adipose tissue, it is specialized for thermogenesis due to the presence of Uncoupling Protein 1 (UCP1).
Why other options are incorrect:
Why other options are incorrect:
- • Adult humans: BAT is most abundant in newborns; while present in small amounts in adults, it is not “large quantities.”
- • Coupled: BAT is characterized by being uncoupled; the energy from the electron transport chain is released as heat rather than used to produce ATP.
- • Hibernating animals: BAT is actually highly abundant and vital for hibernating animals to maintain body temperature.
Ketosis is partly ascribed to:
- a) Over production and Glucose
- b) Under production of Glucose
- c) Increased carbohydrate utilization
- d) Increased fat utilization
Explanation:
Ketosis occurs when the rate of fatty acid oxidation (lipolysis) exceeds the capacity of the citric acid cycle to process the resulting acetyl-CoA. This often happens due to a state of high fat utilization, such as in starvation or uncontrolled diabetes, where glucose is unavailable or cannot be used efficiently.
Why other options are incorrect:
Why other options are incorrect:
- • Over/Under production of Glucose: While glucose levels affect the body’s metabolic state, ketosis specifically results from the shift in fuel source toward lipids.
- • Increased carbohydrate utilization: This actually prevents ketosis, as high carbohydrate levels promote the insulin-mediated storage of fat and use of glucose as the primary fuel.
The free fatty acids in blood are
- a) Stored in fat depots
- b) Mainly bound to β-lipoproteins
- c) Mainly bound to serum albumin
- d) Metabolically most inactive
Explanation:
Free fatty acids (FFAs) in the blood are transported mainly bound to serum albumin. This allows them to circulate in the aqueous plasma and reach tissues where they can be used for energy.
Why other options are incorrect:
Why other options are incorrect:
- • Stored in fat depots: Fatty acids are stored mainly as triglycerides in adipose tissue, not as free fatty acids.
- • Mainly bound to β-lipoproteins: β-lipoproteins transport lipids such as triglycerides and cholesterol, but circulating FFAs are primarily albumin-bound.
- • Metabolically most inactive: Free fatty acids are metabolically active and can be oxidized by tissues to produce energy.
Carnitine is synthesized from
- a) Lysine
- b) Serine
- c) Choline
- d) Arginine
Explanation:
Carnitine is synthesized in the body from the amino acid lysine, with methionine providing the methyl groups required during the synthesis process. Carnitine is essential for transporting long-chain fatty acids into mitochondria for β-oxidation.
Why other options are incorrect:
Why other options are incorrect:
- • Serine: Does not serve as the primary precursor for carnitine synthesis.
- • Choline: Is involved in phospholipid and neurotransmitter synthesis, not as the primary precursor of carnitine.
- • Arginine: Is involved in the urea cycle and nitric oxide synthesis, but is not the primary precursor of carnitine.
A metabolite which is common to pathways of cholesterol biosynthesis from acetyl-CoA and cholecalciferol formation from cholesterol is
- a) Zymosterol
- b) Lumisterol
- c) Ergosterol
- d) 7-Dehydrocholesterol
Explanation:
7-Dehydrocholesterol is an intermediate in cholesterol biosynthesis and serves as the precursor of cholecalciferol (vitamin D₃) in the skin when exposed to UVB radiation.
Why other options are incorrect:
Why other options are incorrect:
- • Zymosterol: An intermediate in cholesterol biosynthesis but is not the precursor used for cholecalciferol formation.
- • Lumisterol: A photoproduct formed from 7-dehydrocholesterol in the skin, not the common metabolite in these pathways.
- • Ergosterol: A fungal sterol and precursor of vitamin D₂, not vitamin D₃.
Acetyl CoA required for extra mitochondrial fatty acid synthesis is produced by
- a) Pyruvate dehydrogenase complex
- b) Citrate lyase
- c) Thiolase
- d) Carnitine-acyl transferase
Explanation:
Citrate lyase (ATP-citrate lyase) produces cytosolic acetyl-CoA from citrate. This acetyl-CoA is required for extra-mitochondrial fatty acid synthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Pyruvate dehydrogenase complex: Produces acetyl-CoA inside mitochondria, not directly in the cytosol.
- • Thiolase: Functions in fatty acid β-oxidation and ketone body metabolism rather than providing cytosolic acetyl-CoA for fatty acid synthesis.
- • Carnitine-acyl transferase: Involved in transport of fatty acyl groups across the mitochondrial membrane, not acetyl-CoA production.
Biosynthesis of Triglyceride and Lecithine both require an intermediate:
- a) Monoacyl glycerol phosphate
- b) Phosphatidic acid
- c) Phosphatidyl ethanol amine
- d) Phosphatidyl cytidylate
Explanation:
Phosphatidic acid is a common intermediate in the biosynthesis of both triglycerides (triacylglycerols) and phospholipids such as lecithin (phosphatidylcholine). It can be converted into diacylglycerol for triglyceride synthesis or into CDP-diacylglycerol-related pathways for phospholipid synthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Monoacyl glycerol phosphate: Is an earlier intermediate and is not the common branching intermediate for both pathways.
- • Phosphatidyl ethanolamine: Is itself a phospholipid and can be converted to phosphatidylcholine, but is not the common intermediate for triglyceride synthesis.
- • Phosphatidyl cytidylate: Is not the common intermediate shared by triglyceride and lecithin synthesis.
The rate-limiting step in cholesterol biosynthesis is
- a) Squalene synthetase
- b) Mevalonate kinase
- c) HMG-CoA synthetase
- d) HMG-CoA reductase
Explanation:
HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonate and is the major rate-limiting and regulated enzyme of cholesterol biosynthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Squalene synthetase: Catalyzes a later step in cholesterol biosynthesis and is not the principal rate-limiting enzyme.
- • Mevalonate kinase: Catalyzes phosphorylation of mevalonate but is not the rate-limiting step.
- • HMG-CoA synthetase: Produces HMG-CoA from acetyl-CoA and is not the major regulatory step in cholesterol synthesis.
All the following are constituents of ganglioside molecule except
- a) Glycerol
- b) Sialic acid
- c) Hexose sugar
- d) Sphingosine
Explanation:
Glycerol is not a constituent of gangliosides. Gangliosides are glycosphingolipids composed of ceramide (sphingosine + fatty acid) linked to oligosaccharides containing one or more sialic acid residues.
Why other options are correct:
Why other options are correct:
- • Sialic acid: A characteristic component of gangliosides that gives them their acidic nature.
- • Hexose sugar: Gangliosides contain carbohydrate residues, including hexose sugars such as glucose and galactose.
- • Sphingosine: Forms the backbone of ceramide, which is the lipid portion of gangliosides.
An alcoholic amine residue is present in which of the following lipids?
- a) Phosphatidic acid
- b) Cholesterol
- c) Sphingomyelin
- d) Ganglioside
Explanation:
Sphingomyelin contains an alcoholic amine, usually choline, as its polar head group. It is a sphingophospholipid composed of ceramide, phosphate, and choline.
Why other options are incorrect:
Why other options are incorrect:
- • Phosphatidic acid: Contains glycerol, fatty acids, and phosphate but no alcoholic amine head group.
- • Cholesterol: Is a sterol and does not contain an alcoholic amine residue.
- • Ganglioside: Contains ceramide and carbohydrate residues, including sialic acid, rather than an alcoholic amine head group.
Sphingosine is the backbone of all the following except
- a) Cerebroside
- b) Ceramide
- c) Sphingomyelin
- d) Lecithine
Explanation:
Lecithin (phosphatidylcholine) is a glycerophospholipid whose backbone is glycerol, not sphingosine. Sphingosine is the backbone of sphingolipids such as ceramide, cerebrosides, and sphingomyelin.
Why other options are incorrect:
Why other options are incorrect:
- • Cerebroside: A glycosphingolipid containing a ceramide backbone, which includes sphingosine.
- • Ceramide: Consists of sphingosine linked to a fatty acid.
- • Sphingomyelin: A sphingophospholipid containing a ceramide (sphingosine + fatty acid) backbone.
Chylomicron, intermediate density lipoproteins (IDL), low density lipoproteins (LDL) and very low density lipoproteins (VLDL) all are serum lipoproteins. What is the correct ordering of these particles from the lowest to the greatest density?
- a) LDL, IDL, VLDL, Chylomicron
- b) Chylomicron, VLDL, IDL, LDL
- c) VLDL, IDL, LDL, Chylomicron
- d) Chylomicron, IDL, VLDL, LDL
Explanation:
The correct order from lowest to greatest density is Chylomicron → VLDL → IDL → LDL. Lipoprotein density increases as the proportion of protein increases and lipid content decreases.
Why other options are incorrect:
Why other options are incorrect:
- • LDL, IDL, VLDL, Chylomicron: This is essentially the reverse density order.
- • VLDL, IDL, LDL, Chylomicron: Chylomicrons have the lowest density, so they must come first.
- • Chylomicron, IDL, VLDL, LDL: IDL has greater density than VLDL, so IDL must follow VLDL.
A compound normally used to conjugate bile acids is
- a) Serine
- b) Glycine
- c) Glucoronic acid
- d) Fatty acid
Explanation:
Glycine is one of the two amino acids normally used to conjugate bile acids in the liver. The other is taurine. Glycine conjugation produces bile salts such as glycocholate.
Why other options are incorrect:
Why other options are incorrect:
- • Serine: Is not a normal amino acid used for bile acid conjugation.
- • Glucuronic acid: Commonly participates in glucuronidation reactions but is not the normal conjugating group for bile acids.
- • Fatty acid: Is not used to conjugate bile acids.
Which of the following lipoproteins would contribute to a measurement of plasma cholesterol in a normal person following a 12 hr fast?
- a) High density lipoproteins
- b) Low density lipoproteins
- c) Chylomicron
- d) Chylomicron remnants
Explanation:
Low-density lipoproteins (LDL) are a major carrier of cholesterol in fasting plasma and therefore contribute substantially to the measurement of plasma cholesterol. After a 12-hour fast, chylomicrons are normally cleared from the circulation.
Why other options are incorrect:
Why other options are incorrect:
- • High-density lipoproteins: HDL also contains cholesterol and contributes to total plasma cholesterol, so this option is technically also a contributor.
- • Chylomicron: Normally absent or negligible after a 12-hour fast because dietary chylomicrons have been cleared.
- • Chylomicron remnants: These are rapidly removed by the liver and are not a major contributor in a normal fasting sample.
Which of the following products of triacylglycerol breakdown and subsequent β-Oxidation may undergo gluconeogenesis?
- a) Acetyl CoA
- b) Propionyl CoA
- c) All ketone bodies
- d) Some amino acids
Explanation:
Propionyl CoA, produced during β-oxidation of odd-chain fatty acids, is converted to succinyl-CoA. Succinyl-CoA enters the TCA cycle and can ultimately provide intermediates for gluconeogenesis.
Why other options are incorrect:
Why other options are incorrect:
- • Acetyl CoA: Acetyl-CoA from even-chain fatty acids cannot yield net glucose because its carbons are lost as CO₂ in the TCA cycle.
- • All ketone bodies: Ketone bodies cannot undergo net conversion to glucose.
- • Some amino acids: Some amino acids are glucogenic, but they are not products of triacylglycerol breakdown and β-oxidation.
Which of the following regulates lipolysis in adipocytes?
- a) Activation of fatty acid synthesis mediated by cAMP
- b) Glycerol phosphorylation to prevent futile esterification of fatty acids
- c) Activation of triglyceride lipase as a result of hormone-stimulated increases in cAMP levels
- d) Activation of cAMP production by insulin
Explanation:
Activation of triglyceride lipase as a result of hormone-stimulated increases in cAMP levels regulates lipolysis in adipocytes. Hormones such as epinephrine increase cAMP, activating protein kinase A (PKA), which promotes phosphorylation and activation of lipolytic enzymes, leading to triglyceride breakdown.
Why other options are incorrect:
Why other options are incorrect:
- • Activation of fatty acid synthesis: cAMP signaling promotes lipolysis rather than fatty acid synthesis.
- • Glycerol phosphorylation: Adipocytes have low glycerol kinase activity, and this is not the principal mechanism regulating lipolysis.
- • Insulin: Insulin generally suppresses lipolysis by reducing cAMP signaling and promoting dephosphorylation of lipolytic proteins.
Which one of the following compounds is a key intermediate in the synthesis of both triacyl glycerols and phospholipids?
- a) CDP Choline
- b) Phosphatidic acid
- c) Triacyl glyceride
- d) Phosphatidyl serine
Explanation:
Phosphatidic acid is a key intermediate in the synthesis of both triacylglycerols and phospholipids. It is formed from glycerol-3-phosphate and fatty acyl-CoA and serves as a branch-point intermediate. It can be converted to diacylglycerol for triacylglycerol synthesis or to CDP-diacylglycerol for the synthesis of certain phospholipids.
Why other options are incorrect:
Why other options are incorrect:
- • CDP Choline: Participates specifically in the synthesis of phosphatidylcholine and is not a common intermediate for triacylglycerol synthesis.
- • Triacyl glyceride: This is a final storage lipid product, not a key intermediate shared by triacylglycerol and phospholipid synthesis.
- • Phosphatidyl serine: It is a specific phospholipid and can be formed from other phospholipids; it is not the common intermediate for triacylglycerol synthesis.
During each cycle of ongoing fatty acid oxidation, all the following compounds are generated except:
- a) H2O
- b) Acetyl CoA
- c) Fatty acyl CoA
- d) NADH
Explanation:
During each cycle of β-oxidation, the fatty acyl-CoA is shortened by two carbon atoms and produces acetyl-CoA, NADH, and FADH2. The shortened fatty acyl-CoA continues into the next cycle. Therefore, fatty acyl-CoA is not considered a newly generated end product of the cycle; it is the substrate that undergoes oxidation and is regenerated in a shortened form.
Why other options are incorrect:
Why other options are incorrect:
- • H2O: Water is involved in the hydration step of β-oxidation.
- • Acetyl CoA: Two-carbon acetyl-CoA is produced during each cycle of β-oxidation.
- • NADH: NADH is generated during the oxidation of β-hydroxyacyl-CoA to β-ketoacyl-CoA.
All the following statements describing lipids are true except:
- a) They usually associate by covalent interactions
- b) They are structural components of membranes
- c) They are an intracellular energy source
- d) They are poorly soluble in H2O
Explanation:
Lipids usually associate through non-covalent interactions, particularly hydrophobic interactions and van der Waals forces. They are important structural components of biological membranes, serve as an important intracellular energy source, and are generally poorly soluble in water. Therefore, option (a) is the incorrect statement.
Why other options are incorrect:
Why other options are incorrect:
- • Structural components of membranes: Lipids such as phospholipids and cholesterol are major components of biological membranes.
- • Intracellular energy source: Triacylglycerols and fatty acids provide a major source of stored and metabolic energy.
- • Poorly soluble in H2O: Most lipids are hydrophobic and therefore have low solubility in water.
Answer Key Summary
The questions are typically designed to assess the technical skills and knowledge required for the laboratory profession, including the ability to analyze laboratory test results, perform laboratory procedures, and maintain laboratory equipment.
To prepare for these MCQs, candidates should have a thorough understanding of the key concepts and principles of laboratory science. They should also be familiar with common laboratory equipment and procedures, as well as laboratory safety protocols.
Candidates may also benefit from studying specific laboratory science textbooks or taking online courses that cover the material tested in the MCQs. Additionally, practicing sample MCQs and reviewing the answers can help candidates identify areas where they may need to improve their knowledge or skills.
Overall, the MCQs for lab technologists are designed to be challenging and comprehensive, requiring candidates to demonstrate a high level of proficiency in the field of laboratory science.
📚 This article may have been prepared using trusted medical literature, clinical guidelines, textbooks, and peer-reviewed sources.
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