Biochemistry Final Review

Question 1

What is the primary purpose of a buffer in biochemistry?

Answer 1

To maintain a stable pH by resisting changes in H+ concentration.

Question 2

How is ΔE° calculated using half-reactions?

Answer 2

ΔE° = E°(reduction half-reaction) - E°(oxidation half-reaction).

Question 3

What does ΔG° represent in biochemical reactions?

Answer 3

The standard free energy change, indicating spontaneity of a reaction.

Question 4

How do you calculate concentration after a dilution?

Answer 4

C1V1 = C2V2, where C is concentration and V is volume.

Question 5

What determines the oxidation level of a compound?

Answer 5

The number of bonds to more electronegative atoms (e.g., O, N).

Question 6

What is the expected charge of a small peptide at pH 7?

Answer 6

Depends on termini (NH3+ and COO-) and side chains (acidic/basic).

Question 7

How are disulfide bonds formed in proteins?

Answer 7

Through oxidation of two cysteine thiol (-SH) groups.

Question 8

What amino acids are typically found in the core of a protein?

Answer 8

Hydrophobic amino acids (e.g., Val, Leu, Ile).

Question 9

What stabilizes an alpha helix in proteins?

Answer 9

Hydrogen bonds between backbone amides and carbonyls, and R-group interactions.

Question 10

What is a reducing sugar?

Answer 10

A sugar with a free aldehyde or ketone group that can reduce other compounds.

Question 11

How can you distinguish reducing from non-reducing sugars?

Answer 11

Reducing sugars have free aldehyde or ketone, 1–>4 bond.

Question 12

What is the purpose of SDS-PAGE?

Answer 12

To separate proteins by molecular weight under denaturing conditions.

Question 13

What type of DNA sequence do restriction enzymes recognize?

Answer 13

Palindromic sequences (e.g., GAATTC).

Question 14

What does the hemoglobin-oxygen binding curve show?

Answer 14

Cooperative binding: R state (high affinity) and T state (low affinity).

Question 15

What are the types of enzyme inhibitors?

Answer 15

Competitive, non-competitive, uncompetitive, and mixed inhibitors.

Question 16

What stabilizes DNA structure in solution?

Answer 16

Hydrogen bonds, base stacking, and ionic interactions with cations.

Question 17

What is catalytic efficiency (kcat/Km)?

Answer 17

A measure of how efficiently an enzyme converts substrate to product.

Question 18

What is the role of glycosidic bonds in carbohydrates?

Answer 18

To link monosaccharides (e.g., α-1,4 in starch, β-1,4 in cellulose).

Question 19

What are shared intermediates in the citric acid cycle and gluconeogenesis?

Answer 19

Oxaloacetate, citrate, and succinyl-CoA.

Question 20

What is required for DNA synthesis primer?

Answer 20

A short single-stranded DNA or RNA sequence complementary to the template.

Question 21

How are fatty acids named?

Answer 21

By carbon chain length and double bond positions (e.g., 18:1 Δ9).

Question 22

What factors influence membrane fluidity?

Answer 22

Fatty acid chain length, saturation (cis/trans), and cholesterol content.

Question 23

How does cis vs trans configuration affect melting point?

Answer 23

Cis fatty acids have lower melting points due to kinks in the chain.

Question 24

What are the products of fatty acid oxidation used for?

Answer 24

Energy (ATP), ketone bodies, and biosynthetic pathways.

Question 25

What is secondary active transport?

Answer 25

Transport coupled to an ion gradient (e.g., Na+/glucose symport).

Question 26

How is enzyme regulation influenced by ΔG°?

Answer 26

Reactions with large negative ΔG° are irreversible and tightly regulated.

Question 27

What is the function of Complex I in the ETC?

Answer 27

Transfers electrons from NADH to ubiquinone, pumps protons.

Question 28

How does dinitrophenol inhibit ATP synthesis?

Answer 28

It uncouples the ETC by dissipating the proton gradient.

Question 29

Which amino acids are one-step converts to citric acid intermediates?

Answer 29

Glutamate → α-ketoglutarate, Aspartate → Oxaloacetate.

Question 30

What is the key regulatory enzyme of glycolysis?

Answer 30

Phosphofructokinase-1 (PFK-1), inhibited by ATP and citrate.

Question 31

What is the role of the pyruvate dehydrogenase complex?

Answer 31

Converts pyruvate to acetyl-CoA, linking glycolysis to the citric acid cycle.

Question 32

What is the main product of the pentose phosphate pathway used for lipids?

Answer 32

NADPH, which provides reducing power for lipid biosynthesis.

Question 33

What happens during β-oxidation of fatty acids?

Answer 33

Fatty acids are broken into acetyl-CoA units for energy production.

Question 34

What determines lipoprotein density?

Answer 34

Higher protein content increases density (e.g., HDL > LDL).

Question 35

What cofactor is used by aminotransferases?

Answer 35

Pyridoxal phosphate (PLP), derived from vitamin B6.

Question 36

What is the end product of purine degradation in humans?

Answer 36

Uric acid.

Question 37

How is urea synthesized in the urea cycle?

Answer 37

From ammonia, CO2, and aspartate, via ornithine and citrulline intermediates.

Question 38

What is a conservative amino acid replacement?

Answer 38

Substitution with an amino acid of similar properties (e.g., Leu → Ile).

Question 39

How are signals propagated along a neuronal axon?

Answer 39

Via action potentials driven by Na+ and K+ ion fluxes.

Question 40

What are the fates of pyruvate?

Answer 40

Lactate, acetyl-CoA, oxaloacetate, alanine, or ethanol (varies by organism).

Question 41

What activates a G-protein coupled receptor (GPCR)?

Answer 41

Ligand binding causes Gα subunit to exchange GDP for GTP and dissociate.

Question 42

What is the structure of mature mRNA?

Answer 42

5' cap, coding exons, 3' poly-A tail; introns are removed.

Question 43

How do you find the complementary DNA strand sequence?

Answer 43

A ↔ T, C ↔ G (e.g., 5'-ATCG-3' → 3'-TAGC-5').

Question 44

What is the purpose of ELISA?

Answer 44

To detect and quantify proteins/antibodies using enzyme-linked antibodies.

Question 45

How does fluorescence intensity change during protein unfolding?

Answer 45

Intensity decreases as temperature increases due to conformational changes.

Question 46

What products are generated by photosystems?

Answer 46

ATP and NADPH (used in the Calvin cycle).

Question 47

What is the principle of Sanger sequencing?

Answer 47

Uses dideoxynucleotides (ddNTPs) to terminate DNA synthesis at specific bases.

Question 48

How is an open reading frame (ORF) identified?

Answer 48

Starts with a start codon (AUG) and ends with a stop codon (UAA, UAG, UGA).

Question 49

What statistical test compares two-group data means?

Answer 49

A t-test determines if the difference is significant and accurate.

Question 50

What does a confidence interval indicate?

Answer 50

The precision of a measurement; a narrower range is better.