bchem lec sample exam

Tryptophan

Which of the following amino acids is classified as aromatic?

Leucine

Which amino acid is essential in the human diet?

Peptide bond

Which bond stabilizes the primary structure of proteins?

Cysteine

Which amino acid contains a sulfhydryl group?

Glycine at every third residue

Collagen’s triple helix stability is due to the presence of:

Collagen

Which protein is classified as a fibrous protein?

Cysteine

Which amino acid can form disulfide bridges in proteins?

Glutamate → Valine

Sickle cell anemia is due to substitution of which amino acid?

Amino acids

Which of the following is a zwitterion at physiological pH?

α-helices and β-sheets

The secondary structure of proteins includes:

Tryptophan

Which amino acid is important for neurotransmitter synthesis (serotonin)?

Hydrophobic interactions

Which force primarily drives protein folding?

Proline

Which amino acid is an imino acid?

Serine

Which amino acid is phosphorylated during protein regulation?

Lysine

Which amino acid carries a positive charge at physiological pH?

Cooperative binding

Hemoglobin is an example of a protein with:

Histidine

Which amino acid contributes to buffering at physiological pH?

Quaternary

Which protein structure level is lost first in denaturation?

Hydroxyproline

Which amino acid is hydroxylated in collagen synthesis?

Phenylalanine

Which amino acid acts as a precursor of catecholamines?

Chondroitin sulfate

Which glycosaminoglycan is most abundant in cartilage?

Hyaluronic acid

Which of the following is not sulfated?

Activating antithrombin III

Heparin acts as an anticoagulant by:

Contain more carbohydrate than protein

Proteoglycans differ from glycoproteins because they:

Fibronectin

Which glycoprotein is important in cell adhesion?

Hyaluronic acid

Which GAG is present in synovial fluid and vitreous humor?

Asparagine

Which amino acid links carbohydrate to protein in glycoproteins (N-linked)?

Aggrecan

Which proteoglycan is abundant in cartilage?

Rough endoplasmic reticulum and Golgi

Glycoproteins are synthesized mainly in:

Heparin

Which GAG is anticoagulant in function?

Mitochondrial inner membrane

The site of oxidative phosphorylation in eukaryotic cells is:

Smooth ER

Which organelle is responsible for detoxification and lipid metabolism?

Secretory proteins

The ribosomes attached to rough ER are responsible for synthesizing:

Lysosome

Which organelle contains hydrolytic enzymes for degradation?

Microtubules

Which cytoskeletal component is involved in intracellular transport?

Circular, double-stranded

The mitochondrial DNA is:

Golgi apparatus

Which organelle modifies and packages proteins?

Peroxisome

Which organelle produces hydrogen peroxide as a by-product?

Ribosomal RNA synthesis

The nucleolus is the site of:

Centrioles

Which structure forms the spindle during cell division?

Lysosome

Which cellular compartment has the lowest pH?

Actin

The major protein component of microfilaments is:

Golgi apparatus

The major site of protein glycosylation is:

Mitochondria

Which organelle plays a key role in apoptosis by releasing cytochrome c?

Fluid mosaic model

The plasma membrane model is best described as:

Phosphofructokinase-1

The first committed step of glycolysis is catalyzed by:

Glucose-6-phosphatase

Which enzyme converts glucose-6-phosphate to glucose in gluconeogenesis?

TPP (Thiamine pyrophosphate)

Which coenzyme is required for pyruvate dehydrogenase?

Phosphoenolpyruvate → Pyruvate

Which step of glycolysis produces ATP directly?

Phosphofructokinase-1

Which enzyme is inhibited by ATP and citrate?

Muscle

Which tissue lacks glucose-6-phosphatase?

UDP-glucose

Glycogen synthesis requires:

Branching enzyme (amylo-1,4→1,6-transglycosylase)

The enzyme responsible for glycogen branching is:

Calcium and AMP

The major regulator of glycogen phosphorylase in muscle is:

NADPH and ribose-5-phosphate

The pentose phosphate pathway generates:

Glucose-6-phosphatase

Which enzyme is deficient in von Gierke’s disease (Type I glycogen storage)?

Glycogen phosphorylase (muscle)

Which enzyme is deficient in McArdle’s disease (Type V)?

Lysosomal α-1,4-glucosidase

Which enzyme deficiency leads to Pompe disease?

Debranching enzyme

Which enzyme deficiency causes Cori disease (Type III)?

Aldolase B

Fructose intolerance is due to deficiency of:

Galactose-1-phosphate uridyltransferase

Galactosemia is due to deficiency of:

Glucose-6-phosphate dehydrogenase

Which enzyme is absent in red blood cells, making the PPP essential?

Glucagon

Which hormone stimulates glycogenolysis in liver?

Pyruvate carboxylase

Which enzyme catalyzes the conversion of phosphoenolpyruvate to oxaloacetate in

gluconeogenesis?

Lactate from muscle converted to glucose in liver

The Cori cycle involves:

Hexokinase

Which enzyme deficiency causes hemolysis upon oxidant stress?

Fructokinase

Which enzyme deficiency leads to essential fructosuria?

Pyruvate carboxylase

The committed step of gluconeogenesis is catalyzed by:

Fructose-1,6-bisphosphatase

Which enzyme bypasses phosphofructokinase in gluconeogenesis?

Pyruvate kinase

Which glycolytic enzyme catalyzes a substrate-level phosphorylation?

Lactase

Lactose intolerance is due to deficiency of:

Hexokinase

The enzyme that traps glucose inside cells is:

Dihydroxyacetone phosphate

Which glycolytic intermediate is also a precursor for triglyceride synthesis?

Lactate

In anaerobic glycolysis, pyruvate is converted to:

Aldolase B

Which enzyme is deficient in hereditary fructose intolerance?

Energy-releasing breakdown of molecules

Catabolism is best described as:

ATP

Which molecule is considered the “energy currency” of the cell?

Endergonic and synthetic

Anabolic pathways are generally:

Both catabolic and anabolic

Amphibolic pathways are:

NAD+

The universal electron carrier in catabolic reactions is: