Biochem

Question 1

Dry beriberi is characterized by symmetrical……..; wet beriberi includes the addition of………

Answer 1

peripheral neuropathy

high-output congestive heart failure

Question 2

Biotin acts as a CO2 carrier on the surface of carboxylase enzymes and is an essential cofactor for numerous reactions, including the conversion of……… and……. metabolism

Answer 2

pyruvate to oxaloacetate

fatty acid

Question 3

Excess ingestion of avidin, found in egg whites, has been associated with….. deficiency.

Answer 3

biotin

Question 4

Fructose can be detected by …. Because it is a reducing suger like galactose and glucose

Answer 4

Copper reducing test

Question 5

A urine dipstick, however, uses…….. to ascertain the presence of urinary glucose and will not test positive in the presence of……. or……

Answer 5

glucose oxidase

fructose

galactose

Question 6

Hartnup disease, an autosomal recessive metabolic disorder caused by inactivating mutations affecting the……. In the ….. and ….

Answer 6

neutral amino acid transporter

Small intestine and proximal renal tubule

Question 7

Tryptophan is an……. amino acid and a precursor for…..,…., and….

Answer 7

essential

niacin

serotonin

melatonin

Question 8

propionic acid pathway job:

Answer 8

This metabolic pathway funnels specific amino acids (isoleucine, valine, threonine, methionine) and odd-chain fatty acids into the tricarboxylic acid (TCA) cycle (propionyl-CoA → methylmalonyl-CoA → succinyl-CoA → TCA cycle).

Question 9

……..serves as a regulator of the urea cycle through activation of carbamoyl phosphate synthetase I

Answer 9

N-acetylglutamate

Question 10

The cytoplasm of a typical cell is characterized by a low concentration of… and high concentration of…. The extracellular fluid is inversely rich in…. and low in….

Answer 10

Na، K

Na، K

Question 11

G protein-coupled receptors that bind glycoprotein hormones (eg, TSH, LH, FSH) contain 3 major domains: an extracellular domain responsible for ligand binding, a transmembrane domain, and an intracellular domain coupled with heterotrimeric G proteins.

The transmembrane domain is made up of:……

These transmembrane domains help…..

Answer 11

nonpolar, hydrophobic amino acids (eg, alanine, valine, leucine, isoleucine, phenylalanine, tryptophan, methionine, proline, glycine). These amino acids are arranged in an alpha-helical fashion

anchor the protein to the phospholipid bilayer of the cell membrane.

Question 12

The oxygen-hemoglobin dissociation curve describes the relationship between…. and….

Answer 12

the partial pressure of oxygen in the blood

the oxygen saturation of hemoglobin

Question 13

……..interaction is responsible for the characteristic sigmoid shape of the oxygen-hemoglobin dissociation curve

Answer 13

heme-heme

Question 14

myoglobin is a monomeric protein and the primary oxygen-storing protein in … and ….

Answer 14

skeletal and cardiac muscle tissue

Question 15

Tetrahydrobiopterin (BH4) is a cofactor in the synthesis of :(count 4 substances)

Answer 15

serotonin (a major neurotransmitter), tyrosine (a precursor of DOPA), and DOPA (the antecedent of the neurotransmitters dopamine, norepinephrine and epinephrine)

Question 16

FMN serves as a component of complex I, whereas FAD functions as a component of succinate dehydrogenase (complex II). Complex II participates in….. and ……

Answer 16

the electron transport chain and tricarboxylic acid (TCA) cycle

Question 17

Triglycerides stored in adipose tissue are metabolized to free fatty acids and glycerol by hormone-sensitive lipase in response to….. and…..

Answer 17

low insulin

high catecholamine levels.

Question 18

DNA replication occurs with a high degree of fidelity because mismatched nucleotides are repaired through the proofreading activity of…. and….

Answer 18

DNA polymerases delta

epsilon

Question 19

The receptors for most steroid hormones, including progesterone, are located in the ……. and translocate to the nucleus upon ligand binding. In contrast, receptors for thyroid hormone and vitamins A and D are located…….

Answer 19

cytoplasm

within the nucleus at all times

Question 20

colchicine, which impairs…… and…… by interfering with microtubule formation. Colchicine also decreases……. in response to monosodium urate crystals, resulting in decreased neutrophil activation.

Answer 20

neutrophil migration

phagocytosis

tyrosine phosphorylation

Question 21

….is an enzyme found in adipose tissue that catalyzes the mobilization of stored triglycerides into free fatty acids (FFAs) and glycerol. HSL is activated in response to……, whereas it is inhibited by the release of….. The stress hormones stimulate…., leading to increased cAMP production and activation of…..). Finally, PKA phosphorylates and activates HSL, stimulating lipolysis.

Answer 21

Hormone-sensitive lipase (HSL)

stress hormones (eg, catecholamines, glucagon, ACTH)

insulin

Gs protein-coupled receptors on adipocytes

protein kinase A (PKA

Question 22

Cortisol increases the conversion of norepinephrine to epinephrine in the….. by increasing the expression of…….

Answer 22

adrenal medulla

phenylethanolamine-N-methyltransferase.

Question 23

Glucogenic amino acid metabolism produces….. or….

Answer 23

pyruvate

TCA cycle intermediates

Question 24

Ketogenic amino acid metabolism generates the ketone body precursor….

Answer 24

acetyl-CoA

Question 25

During normal glycolysis, ATP is generated when 1,3-BPG is converted to 3-phosphoglycerate by the enzyme…..

Answer 25

phosphoglycerate kinase

Question 26

The conversion of 1,3-BPG to 2,3-BPG is increased in…. and…..

Answer 26

chronic anemia

Question 27

The activity of pyruvate carboxylase is increased by……

Answer 27

acetyl-CoA

Question 28

When ribose-5-phosphate is produced in excess,…… and….. can produce the glycolytic intermediates glyceraldehyde-3-phosphate and fructose-6-phosphate for ATP generation

Answer 28

transketolase transaldolase

Question 29

the conversion of homocysteine to cystathionine requires the enzyme….., the amino acid….., and the cofactor vitamin…..

Answer 29

cystathionine synthase serine B6

Question 30

branched-chain alpha-keto acid dehydrogenase complex (BCKDC) deficiency. BCKDC is a……-dependent enzyme that helps breakdown the branched-chain amino acids……, ………, and…… into substrates that can be used in the tricarboxylic acid cycle.

Answer 30

thiamine leucine Isoleucine valine

Question 31

BCKDC deficiency is neurotoxic primarily due to elevated levels of…..

Answer 31

leucine

Question 32

Propionyl-CoA is subsequently converted to methylmalonyl-CoA in a reaction catalyzed by……..-dependent propionyl-CoA carboxylase.

Answer 32

biotin

Question 33

…….. proteins are stereoselective and preferentially catalyze the entrance of…-glucose rather than…-glucose into cells

Answer 33

GLUT4 D L

Question 34

Bone turnover is therefore regulated by the ratio of……

Answer 34

OPG to RANK-L

Question 35

During gluconeogenesis, phosphoenolpyruvate carboxykinase uses….. to synthesize phosphoenolpyruvate from oxaloacetate.

Answer 35

GTP

Question 36

The enzymes responsible for glycolysis, fatty acid……, and the pentose phosphate pathway reside in the……

Answer 36

synthesis cytosol

Question 37

The smallest amino acid,……., is necessary at every third position to ensure compact coiling of the helix in collagen

Answer 37

glycine (Gly)

Question 38

In collagen synthesis Many of the amino acids represented by X and Y are proline residues, which kink the polypeptide chain and enhance the…… due to their ring configuration.

Answer 38

rigidity of the helical structure

Question 39

Vitamin C is a required cofactor for this post-translational modification. Defective hydroxylation of these residues severely diminishes the amount of collagen secreted by fibroblasts and impairs…… and covalent crosslink formation.

Answer 39

triple helix stability

Question 40

Collagen is the most abundant protein in the human body and is synthesized by……, osteoblasts, and……..

Answer 40

fibroblasts chondroblasts

Question 41

The gamma chains do not bind effectively to 2,3-BPG due to replacement of a histidine residue with…….

Answer 41

serine

Question 42

Treatment for MSUD involves restricting BCAAs in the diet. BCKDC (in addition to pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase) requires 5 cofactors:

Answer 42

thiamine, lipoate, and coenzymes A, FAD, and NAD

Question 43

Apoptosis can occur through either the intrinsic (mitochondria-mediated) pathway or the extrinsic (receptor-initiated) pathway. Both pathways converge in the activation of……. Which are proteolytic enzymes that cleave cellular proteins. They contain….. and are able to cleave……acid residues (cysteine-aspartic-acid-proteases)

Answer 43

caspases cysteine aspartic

Question 44

Growth hormone binds to cell surface receptors, leading to intracellular activation of….. …..and hematopoietic growth factors (eg, erythropoietin, G-CSF) also use this pathway.

Answer 44

the JAK-STAT pathway Cytokines (eg, interferon)

Question 45

Arginase is a urea cycle enzyme that produces… and…. from arginine. Arginase deficiency results in progressive spastic diplegia, growth delay, and abnormal movements. Treatment includes an arginine-free, low-protein diet.

Answer 45

urea ornithine

Question 46

Heme is synthesized in virtually every organ, but the principal sites of synthesis are……(located in the bone marrow) and….. (use heme in microsomal cytochrome P450 system).

Answer 46

erythrocyte precursor cells hepatocytes

Question 47

Adhesion of cells to the extracellular matrix involves integrin-mediated binding to…….,……., and……. Differential expression of integrin subtypes affects adhesion properties of individual cells, and has been found to correlate with malignant behavior in a number of tumors

Answer 47

fibronectin collagen laminin

Question 48

Impairment of the ubiquitin-proteasome system can contribute to the development of neurodegenerative disorders such as……. and……. diseases

Answer 48

Parkinson’s Alzheimer’s

Question 49

Tay-Sachs disease is an autosomal recessive disorder caused by…. deficiency, which results in…… accumulation in neuronal lysosomes. Key clinical features include progressive neurodegeneration (eg, developmental regression), an exaggerated startle reflex, and a cherry-red macular spot.

Answer 49

β-hexosaminidase A GM2 ganglioside

Question 50

Isoniazid inhibits……… leading to impaired activation of pyridoxine (vitamin B6). Pyridoxine is a cofactor for…….., the enzyme that catalyzes the rate-limiting step of heme synthesis. Inhibition of this step can result in….. anemia.

Answer 50

pyridoxine phosphokinase, δ-aminolevulinic acid synthase sideroblastic