merged mcb 450

Which of the following biological molecules are a primary component of potatoes?

Carbohydrates

In a condensation rxn which of the following molecules is ALWAYS formed?

Water

The bonds that are broken when water vaporizes are:

Hydrogen bonds b/w water molecules

If an aqueous solution has a hydroxyl ion concentration of 10-4 M, what is the pH of this solution?

10

A peptide bond is the linkage b/w:

the carbonyl carbon of the carboxylic acid of one amino acid and the nitrogen of the amine of ANOTHER amino acid.

Which of the following amino acids introduces a kink into an α helix (due to rigidity); thus, rarely found in α helix?

Proline

What is the major driving force for the formation of a phospholipid bilayer?

Hydrophobic effect

When a protein is transferred to a solution with a pH that is much lower than its optimal range, which of the following levels of protein structure is or can be affected?

Secondary, tertiary, and quarternary

PRIMARY = PEPTIDE BOND, CANT BE DENATURED BY ACID

What is the role of hydrochloric acid in protein digestion?

Denatures proteins

Which of the following amino acids is the least water soluble?

Cystine

Cystine is cysteine + cysteine with disulfide(?) bonds, very not water soluble :)

Lactose intolerance is due to the deficiency of which enzyme?

Lactase

What is responsible for transporting fatty acids from the lumen of the gut to the epithelial cell?

Bile acid micelles

Which of the following conditions might cause steatorrhea?

Inflammatory bowel disease (IBD)

What does an elevated level of alanine transaminase in a blood test typically indicate?

Liver damage or injury

What is Phenylketonuria (PKA)?

A rare metabolic disease that prevents the breakdown of phenylalanine.

Which of the following co-factor is involved in the synthesis of succinyl CoA from L-methylmalonyl CoA during methionine catabolism?

Deoxyadenosylcobalamin

Maple Syrup Urine Disease (MSUD) is a metabolic defect in the metabolism of amino acids:

Leucine, Isoleucine, Valine

Methotrexate inhibits purine synthesis by targeting the formation of:

tetrahydrofolate from folate.

Which of the following statement regarding gout is FALSE?

Gout is associated with degradation of pyrimidine

Which of the following statements is FALSE regarding Lesch-Nynan syndrome?

Gout causes Lesch-Nynan syndrome

What is the methyl-folate trap?

When vitamin B12 is not available, N5-methyl-THF cannot be converted back to THF.

For electron transport by mitochondria under physiological conditions, the overall reaction catalyzed by the complex III is the reduction of:

Cytochrome C

There are 3 conformations of the β subunit of ATP synthase, which represent different state of this enzyme. Which conformation represents the synthesis state of ATP synthase, ATP is synthesized from ADP and Pi?

T (tight) form

Which of the following is a unique property of complex 4 in the electron transport chain with respect to the other protein complexes?

It reduces oxygen to water

What shuttle mechanism transfers the electrons from cytosolic NADH into the mitochondria with the electrons being transferred to complex II?

Glycerol-3-phosphate shuttle

Which of the following biological molecules are the main structural component of cell membrane?

Phospholipids

Which of the following enzyme can catalyze the formation of glycosidic bonds in carbohydrate?

Glycogen synthase

Which of the statements is TRUE about phosphodiester bond in DNA?

The formation of a phosphodiester bond involves a dehydration reaction

Which of the following statement is FALSE about disulfide bonds (disulfide bridges)?

Disulfide bonds are important to primary and tertiary structure, not quaternary.

The partially positively charged hydrogen atoms of one water molecule can interact with the partially negatively charged oxygen atoms of another water molecule. This interaction between water molecules is called:

a hydrogen bond

If you fill a glass of water slightly above the rim without it spilling, which property is primarily responsible for the water's dome-like shape?

The cohesive forces of the water molecules

If an aqueous solution has pH of 10, what is the concentration of hydroxyl ion of this solution?

10^-4

A student must make a buffer solution with a pH of 4.0. Determine which weak acid is the best option to make a buffer at the specified pH

Formic acid, Ka=1.77x10^-4, 2.0 M

The peptide bond that links two amino acids together in a protein is best described as which of the following?

A covalent bond that links the alpha-carboxyl group of one amino acid to the alpha-amino group of another

A polypeptide with a net negative charge at physiologic pH (~7.4) most likely contains amino acids with R groups of what type?

Acidic R group

Proline is called "alpha-helix breaker" because of its:

side chain bonded to both the alpha-carbon and the nitrogen atom, limiting the rotation.

Which of the following statement is TRUE about hydrophobic effects?

They are the driving force in the formation of micelles of amphipathic compounds in water.

1. When sequencing a protein, it is necessary to break disulfide bonds within a polypeptide chain. What reagent is used to break the disulfide bonds?

a. β‑mercaptoethanol.

1. Which of the statements is TRUE about protein denaturation?

Denaturation of an enzyme will cause a loss of its catalytic activity

1. Sickle cell anemia is caused by a point mutation in hemoglobin, where a glutamate residue is changed to a valine. Based on this mutation mechanism, what level of protein structure is affected by sickle cell anemia?

Primary, secondary, tertiary, and quarternary structure

1. Enzymes that are activated by specific proteolytic cleavage are called:

zymogens

One of the roles of hydrochloric acid (gastric acid) in protein digestion is to

Activate pepsin.

Which of the following is NOT a component of the pancreatic juice?

Enteropeptidase

Which of the following statements correctly describes the formation and properties of cystine?

Cystine is the oxidized dimer of cysteine, linked by a disulfide bond (-S-S-).

Canada geese are able to digest grass because they have bacteria in their digestive tracks which produce an enzyme named cellulase. Which of the following glycosidic bond can be broken down by cellulase?

beta-1,4 Glycosidic bond in cellulose

What is the primary cause of lactose intolerance?

A deficiency of the enzyme lactase in the small intestine.

What is the main function of bile salts?

Emulsification of lipids

Which property of lipids that makes their digestion more complicated than that of carbohydrates and proteins?

Lipids are not water soluble.

What is responsible for transporting triacylglycerol from the small intestine epithelial cells to blood?

Chylomicron

1. Which of the following statement best describes the micelles?

a. Micelles are tiny microdroplets that are emulsified by bile salts, solubilizing lipid.

1. Which of the following condition might cause steatorrhea?

a. Gallbladder stone.

1. Which other enzyme is commonly measured alongside ALT to assess liver health?

a. Aspartate transaminase (AST).

1. Which of the following compound carries the first amino group into urea cycle?

a. Carbamoyl phosphate.

1. What is the most crucial dietary modification for an individual with PKU?

a. A low-phenylalanine diet.

1. Elevated urinary formiminoglutamic acid (FIGLU) levels following a histidine load are most indicative of a deficiency in which of the following vitamins?

B9

1. Which of the following co-factor is involved in the methylation of homocysteine to methionine?

Methylcobalamin

1. Nitrogen fixation is the process by which:

a. atmospheric nitrogen gas (N2) is converted into ammonia (NH3), a form usable by living organisms.

1. Maple Syrup Urine Disease (MSUD) is a metabolic disorder caused by a deficiency in the branched-chain alpha-keto acid dehydrogenase (BCKAD) enzyme complex. The function of this enzyme is to break down which group of amino acids?

a. Leucine, isoleucine, and valine.

1. Which of the following best describes the structural relationship between a nucleoside and a nucleotide?

a. A nucleotide is a nucleoside with one or more phosphate groups attached.

1. Which of the following is a common side effect of methotrexate?

Severe hair loss

1. The deficiency of the Adenosine Deaminase (ADA) enzyme leads to the accumulation of what toxic substance, particularly in lymphocytes?

a. Adenosine and deoxyadenosine.

1. In humans, uric acid is the final product of the metabolism of what substances?

Purines

1. Carbamoyl phosphate is made during urea cycle and pyrimidine synthesis. NH4+ is the nitrogen source in carbamoyl phosphate in urea synthesis. What is the nitrogen source in carbamoyl phosphate in pyrimidine synthesis?

Glutamate

1. The enzyme deficiency in Lesch-Nyhan syndrome disrupts the purine salvage pathway, leading to an overproduction of uric acid. What is the metabolic consequence of this enzyme deficiency?

a. Hypoxanthine and guanine are converted into excess uric acid instead of being recycled into nucleotides.

1. Thymidylate synthase catalyzes the synthesis of dTMP from dUMP by adding a one carbon methyl group to dUMP. What is the source of the one carbon in this reaction?

N5,N10,-methylene-THF

1. The "methyl-folate trap" is a metabolic phenomenon that occurs when a deficiency of which vitamin prevents the regeneration of tetrahydrofolate (THF) from 5-methyl-THF?

Vitamin B12 (cobalamin)

1. Tetrahydrofolate (THF) is a critical coenzyme in one-carbon metabolism. Which of the following is the primary role of THF?

a. To act as a carrier for one-carbon units.

1. Which of the following molecules delivers electrons from the TCA cycle to Complex I of the electron transport chain (ETC)?

NADH

Which critical cellular process is inhibited by cyanide?

a. The electron transport chain in mitochondria.

1. What is the movement of protons (H+) back into the mitochondrial matrix through ATP synthase called?

Chemiosmosis

1. What is the energy released as electrons move down the electron transport chain used for?

a. Pump protons (H+) from the mitochondrial matrix into the intermembrane space to create a proton gradient.

1. What is the primary function of Complex IV (cytochrome c oxidase) in the electron transport chain?

a. To reduce molecular oxygen (O2) to water (H2O).

1. The glutamate site within the c-ring of ATP synthase is essential for___.

a. Facilitating proton translocation, which drives the rotation of the c-ring.

1. What is the reason for a higher yield of ATP when the malate-aspartate shuttle is used to transfer the high energy electron from cytoplasmic NADH than the glycerol-3-phosphate shuttle?

a. It generates mitochondrial NADH, which leads to a higher ATP yield than mitochondrial FADH2

1. What is the primary effect of an uncoupler such as 2,4-dinitrophenol (DNP) on oxidative phosphorylation in the mitochondria?

a. It transports protons across the inner mitochondrial membrane, dissipating the proton motive force as heat.

What property does a carbonyl have to make it a good target for a nucleophilic attack?

A dipole with a partial positive charge on the carbon and a partial negative charge on the oxygen.

Which is true about the effect of an enzyme on the activation of a reaction?

Lowers the transition state so less energy is required to complete the reaction.

Which amino acid interaction is NOT favorable?

Arginine and Lysine.

The binding energy of an Enzyme-Substrate interaction is the sum of what?

Weak interactions such as hydrogen bonds, ionic and hydrophobic interactions.

What does Km represent?

The Km is ½ of the Vmax and represents the binding affinity of the substrate-enzyme interaction.

Noncompetitive inhibitor double-reciprocal plot result?

A

How does aspirin inhibit COX?

Aspirin reacts with a Serine in the catalytic pocket of COX to form a covalent bond and inhibit enzyme activity.

Why does enzyme activity decrease at high temperature?

The enzyme becomes denatured and loses the three-dimensional structure critical for activity.

What occurs when pyruvate is reduced by NADH?

The C2 carbonyl will be converted to a hydroxyl and gain proton.

Which is NOT true about NADPH in immune response?

B and C.

Which statement about membrane transport is true?

Solutes that cross a cell membrane by facilitated or passive diffusion will move down a concentration gradient.

Which is NOT a second messenger?

Protein kinase A.

How does HGP activation lead to Ca²⁺ release?

GTP bound HGP activates PLC → PIP2 → IP3 → ER Ca²⁺ release.

What feature is shared by kinase receptor complexes?

Conformational changes occur upon ligand binding.

Least favorable ΔG?

ΔG = +50 kcal/mol

Effect of mutating Arg finger to Asp?

The negative charge of the Asp repels the negative charge of the gamma phosphate.

Role of Mg²⁺ in ATP binding?

Neutralizes phosphate negative charges.

Least to most oxidized carbon?

Methane > Methanol > CO2

Full reduction of FAD?

Gain of 2 electrons and 2 protons.

Why are thioesters more reactive than esters?

The lack of resonance between the carbonyl oxygen and the sulfur atom.

PIP2 cleavage by PLC occurs at?

A and C.

What does PLA2 do?

Cleaves at the Carbon 2 ester to make a free fatty acid and a lysolipid.

How does ATP inhibition of PFK1 inhibit hexokinase?

Inhibition of PFK1 → ↑F6P ↔ G6P → inhibits hexokinase.

Aldolase B products from fructose-1-phosphate?

1 Glyceraldehyde and 1 dihydroxyacetone phosphate.

Which statement about pyruvate kinase is false?

PKA activates PK in the liver.