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Biochem 1 > Biochem > Flashcards

Biochem Flashcards

1
Q

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

A

peripheral neuropathy

high-output congestive heart failure

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2
Q

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

A

pyruvate to oxaloacetate

fatty acid

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3
Q

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

A

biotin

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4
Q

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

A

Copper reducing test

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5
Q

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

A

glucose oxidase

fructose

galactose

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6
Q

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

A

neutral amino acid transporter

Small intestine and proximal renal tubule

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7
Q

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

A

essential

niacin

serotonin

melatonin

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8
Q

propionic acid pathway job:

A

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).

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9
Q

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

A

N-acetylglutamate

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10
Q

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….

A

Na، K

Na، K

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11
Q

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…..

A

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.

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12
Q

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

A

the partial pressure of oxygen in the blood

the oxygen saturation of hemoglobin

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13
Q

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

A

heme-heme

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14
Q

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

A

skeletal and cardiac muscle tissue

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15
Q

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

A

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

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16
Q

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

A

the electron transport chain and tricarboxylic acid (TCA) cycle

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17
Q

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

A

low insulin

high catecholamine levels.

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18
Q

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

A

DNA polymerases delta

epsilon

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19
Q

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…….

A

cytoplasm

within the nucleus at all times

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20
Q

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

A

neutrophil migration

phagocytosis

tyrosine phosphorylation

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21
Q

….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.

A

Hormone-sensitive lipase (HSL)

stress hormones (eg, catecholamines, glucagon, ACTH)

insulin

Gs protein-coupled receptors on adipocytes

protein kinase A (PKA

22
Q

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

A

adrenal medulla

phenylethanolamine-N-methyltransferase.

23
Q

Glucogenic amino acid metabolism produces….. or….

A

pyruvate

TCA cycle intermediates

24
Q

Ketogenic amino acid metabolism generates the ketone body precursor….

A

acetyl-CoA

25
Q

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

A

phosphoglycerate kinase

26
Q

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

A

chronic anemia

27
Q

The activity of pyruvate carboxylase is increased by……

A

acetyl-CoA

28
Q

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

A

transketolase

transaldolase

29
Q

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

A

cystathionine synthase

serine

B6

30
Q

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.

A

thiamine

leucine

Isoleucine

valine

31
Q

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

A

leucine

32
Q

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

A

biotin

33
Q

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

A

GLUT4

D

L

34
Q

Bone turnover is therefore regulated by the ratio of……

A

OPG to RANK-L

35
Q

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

A

GTP

36
Q

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

A

synthesis

cytosol

37
Q

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

A

glycine (Gly)

38
Q

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.

A

rigidity of the helical structure

39
Q

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.

A

triple helix stability

40
Q

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

A

fibroblasts

chondroblasts

41
Q

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

A

serine

42
Q

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

A

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

43
Q

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)

A

caspases

cysteine

aspartic

44
Q

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

A

the JAK-STAT pathway

Cytokines (eg, interferon)

45
Q

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.

A

urea

ornithine

46
Q

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).

A

erythrocyte precursor cells

hepatocytes

47
Q

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

A

fibronectin

collagen

laminin

48
Q

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

A

Parkinson’s

Alzheimer’s

49
Q

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.

A

β-hexosaminidase A

GM2 ganglioside

50
Q

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.

A

pyridoxine phosphokinase,

δ-aminolevulinic acid synthase

sideroblastic

Biochem 1 (4 decks)

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