Biomolecules & Biochemistry — Part 1: 40 MCQs with Explanations

Salivary amylase (ptyalin) begins the digestion of carbohydrates in the mouth.

UV rays from sunlight convert 7-dehydrocholesterol to vitamin D3 in the skin.

Vitamin C (ascorbic acid) is needed for collagen synthesis; its deficiency leads to scurvy.

Vitamins A, D, E, and K are fat-soluble, stored in the body's fatty tissue.

The capsid is the protein shell that encloses the viral genetic material.

Pepsin is activated from pepsinogen by HCl and breaks proteins into peptides.

Nucleotides consist of a sugar, phosphate, and a nitrogenous base; amino acids are protein monomers.

Kwashiorkor is severe protein malnutrition, common in children.

According to the MDCAT syllabus on acellular life, viruses have a structure that includes a protein coat called a capsid, which encloses their genetic material.

In yeast, anaerobic respiration (alcoholic fermentation) converts glucose into ethanol, carbon dioxide, and a small amount of ATP.

Enzymes are biological catalysts that are not consumed or permanently altered in the reactions they catalyze, a key characteristic covered in the syllabus.

7-dehydrocholesterol in the skin is converted to cholecalciferol (vitamin D3) upon exposure to UV-B radiation from sunlight.

These models describe the specific interaction between an enzyme's active site and its substrate.

Monosaccharides are the simplest form of carbohydrates, consisting of single sugar units such as glucose and fructose.

Fungi, including yeast, are absorptive heterotrophs. They secrete digestive enzymes onto their food and then absorb the dissolved nutrients.

Salivary amylase (in mouth) and pancreatic amylase (in small intestine) catalyze the hydrolysis of starch into maltose, a disaccharide.

Enzymes are not consumed in reactions; they are catalysts that speed up reactions without being permanently altered or used up.

The proximal convoluted tubule (PCT) reabsorbs approximately 65-70% of filtrate, including glucose, amino acids, vitamins, and most ions and water.

The small intestine is the primary site for digestion and absorption of nutrients (carbohydrates, proteins, fats, vitamins, minerals) into the bloodstream.

Aerobic respiration (glycolysis → link reaction → Krebs cycle → ETC) yields approximately 36-38 ATP per glucose molecule in the presence of oxygen.

Salivary amylase (in mouth) and pancreatic amylase (in duodenum) break down starch into maltose, a disaccharide.

Gas exchange occurs in lungs. The liver performs bile synthesis, glycogen storage, detoxification, plasma protein synthesis, and urea production.

Vitamin C (ascorbic acid) deficiency causes scurvy, characterized by bleeding gums, poor wound healing, and connective tissue defects due to impaired collagen synthesis.

Trypsin (activated from trypsinogen by enterokinase) hydrolyzes proteins into smaller peptides. It also activates other pancreatic zymogens.

The colon absorbs water and electrolytes from indigestible residue, forms/stores feces, and hosts bacterial fermentation producing vitamins K and B.

Enzymes speed up reactions by lowering activation energy without being consumed or altering equilibrium position.

The PCT reabsorbs ~65-70% of filtrate including all glucose, amino acids, vitamins, and most ions/water via active and passive transport.

Most digestion completion and nutrient absorption (monosaccharides, amino acids, fatty acids, vitamins, minerals) occurs in the small intestine.

Theoretical maximum is 36-38 ATP per glucose: glycolysis (2 ATP net + 2 NADH → 3-5 ATP), link reaction (2 NADH → 5 ATP), Krebs cycle (2 ATP + 6 NADH → 15 ATP + 2 FADH₂ → 3 ATP). Actual yield is lower due to proton leakage.

Pathogen filtration occurs primarily in spleen and lymph nodes. The liver detoxifies chemicals, stores glycogen, produces bile, and synthesizes plasma proteins.

Active transport moves substances against concentration gradient using energy (ATP or ion gradients); facilitated diffusion moves down gradient without energy.

Primary structure is the linear sequence of amino acids linked by peptide bonds; determines higher-order folding.

Calvin cycle (light-independent reactions) occurs in chloroplast stroma, using ATP and NADPH to fix CO₂ into glucose.

Vitamins A, D, E, K are fat-soluble (stored in liver/adipose). Vitamins B and C are water-soluble (excreted if in excess).

Hydrogen bonds between backbone carbonyl and amide groups stabilize alpha helices and beta pleated sheets (secondary structure).

Oxidative phosphorylation (electron transport chain + chemiosmosis) produces ~34 ATP per glucose, compared to 2 ATP from glycolysis alone.

Beriberi results from thiamine (B1) deficiency, causing neurological and cardiovascular symptoms due to impaired carbohydrate metabolism.

Colon absorbs water and electrolytes, forms/stores feces, and hosts bacterial fermentation producing vitamins K and B complex.

Pellagra (dermatitis, diarrhea, dementia) results from niacin (B3) deficiency, often associated with corn-based diets low in tryptophan.

Catalase breaks down toxic hydrogen peroxide (H₂O₂) produced during metabolism into harmless water and oxygen: 2H₂O₂ → 2H₂O + O₂.

again and again is the correct answer to “Like enzymes, co enzyme can be used”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Marasmus is the correct answer to “Which of the following is a disease caused by deficiency of protein in children”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Deficiency of vitamin C will cause: Scurvy .

Special enzymes are released during necrosis from lysosomes .

Special kind of protein containing iron is called as Hemoglobin .

Enzyme activity can also be charted through the Rate of reaction .

Ascorbic acid is the correct answer to “Which one of the following vitamin is known as the œanti- Sterile factor”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Vitamin D is the correct answer to “Which of the following vitamins is useful in ostcoimalacia”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Amoeba secretes digestive enzymes to hydrolyse All of these and fats .

The simplest amino acid is glycine .

Many bacteria in our digestive system synthesize vitamins for example vitamin B12 .

ribosomes is the correct answer to “which of the following is called protein synthesizing machine”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Glomerular filtrate is the correct answer to “Which of the following filtrate contains excessive amount of amino acids, glucose, and salts”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

All of these is the correct answer to “Which of the following are proteins in nature”. Items of this type are drawn from the Biomolecules & Biochemistry — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Breaking of terminal phosphate of ATP releases about 7.3 Kcal of energy.

ATP are consumed during Glycolysis .

In Anaerobic respiration only 2% % of the energy present within the chemical bond of glucose is converted into ATP.

Carbohydrates, fats & proteins are essential for All of these .

Dipeptides into amino acids are are converted through Erypsin .

Protein subunits of capsid is called the capsomeres is a characteristic of each virus. Their number in Herpes virus is 162 .

Protein coat the capsid of adenovirus is Surrounding genome .

Actin and myosin are the basic proteins involved in contractile machinery of our body to which type of proteins do they belong Fibrous Proteins .

ATP is a an important molecule for its major function As an energy currency of the cell .

helical structure is kept by the formation of H bonds bonds among amino acids molecules.

Antibodies play important role against microorganisms and other pathogens to which type of proteins do they belong Globular proteins .

Which structural organization is most common in globular proteins Tertiary .

A bond formed by linkage between -OH of carboxyl group of one amino acid and H of amino group of another amino acid which releases water is called Peptide bond .

Total number of amino acids in a hemoglobin molecule are 574 .

Which structure of protein gives information aboutnumber and sequence of amino acids in it Primary structure .

Hemoglobin molecule exhibits which structural organization of proteins Quaternary structure .

In an aqueous environment the most stable tertiary conformation is that in which Hydrophobic amino acids are buried inside the conformation.

Protein coasts of viruses are synthesized in Lytic cycle .

Proteins are polymers of Amino acids .

In Glycin an amino acid R group is replaced by H .

The element in basic structure of proteins which differentiate them from carbohydrates S .

Animals obtain carbohydrates mainly from Starch .

Lipids are soluble in which of the following Ether .

Lipid molecules can store double amount of energy as compared to same amount of carbohydrate because of high number of C-H bonds .

The one which is not a globular protein Myosin .

Which of the following carbohydrate can not be hydrolysed Monosaccharide .