Ace your BCHM 307 Exam 1 at Purdue University with this comprehensive study guide featuring 150 meticulously crafted multiple-choice questions (MCQs). Each question is accompanied by a clear answer and a detailed elaboration, explaining not only the correct choice but also why the other options are...
BCHM 307 - Exam 1 ~Purdue 2023 with 100% correct questions and answers
1. In humans, approximately what percentage of the genome encodes for proteins?
o a) 50%
o b) 25%
o c) 1.5%
o d) 10%
Elaboration:
o The human genome contains a vast amount of non-coding DNA, with only a small
fraction (around 1.5%) directly coding for proteins.
o The other options significantly overestimate the protein-coding portion of the human
genome.
2. Of the following biomolecules - lipids, carbohydrates, nucleotides, and amino acids - which is
never found in a polymerized form?
o a) Lipids
o b) Carbohydrates
o c) Nucleotides
o d) Amino acids
Elaboration:
o While amino acids are the building blocks of proteins (polymers), they themselves do
not form polymers on their own.
o Lipids can form aggregates and complex structures, but not true polymers.
o Carbohydrates form polysaccharides like starch and glycogen.
o Nucleotides polymerize to form nucleic acids like DNA and RNA
3. Which of the following is NOT a characteristic of a coupled reaction?
o a) The overall ΔG is negative
o b) An exergonic reaction drives an endergonic reaction
o c) The individual reactions have the same ΔG
, o d) The reactions share a common intermediate
Elaboration:
o In coupled reactions, an energetically favorable (exergonic) reaction provides the energy
to drive an energetically unfavorable (endergonic) reaction. The overall ΔG is negative,
indicating spontaneity.
o The individual reactions in a coupled process will have different ΔG values, with one
being negative and the other positive.
4. What is the relationship between ΔG and the spontaneity of a reaction?
o a) If ΔG < 0, the reaction is spontaneous
o b) If ΔG > 0, the reaction is spontaneous
o c) If ΔG = 0, the reaction is spontaneous
o d) ΔG has no relationship to spontaneity
Elaboration:
o ΔG (Gibbs free energy change) is a thermodynamic quantity that predicts the
spontaneity of a reaction. A negative ΔG indicates a spontaneous or exergonic reaction.
o A positive ΔG denotes a non-spontaneous or endergonic reaction.
o A ΔG of 0 indicates a reaction at equilibrium
5. Which of the following statements accurately describes enthalpy (H)?
o a) It is a measure of disorder or randomness in a system
o b) It is the heat content of a system
o c) It always decreases in spontaneous reactions
o d) It has units of J/K-mol
Elaboration:
o Enthalpy (H) represents the total heat content of a system. It is related to the internal
energy of the system and the pressure and volume.
o Entropy is the measure of disorder.
o Enthalpy can increase or decrease in spontaneous reactions, depending on the entropy
change and temperature
, 6. How does entropy (S) affect the ΔG of a reaction?
o a) An increase in entropy leads to a more positive ΔG
o b) An increase in entropy leads to a more negative ΔG
o c) Entropy has no effect on ΔG
o d) The effect of entropy on ΔG depends on the enthalpy change
Elaboration:
o Entropy (S) is a measure of disorder or randomness. An increase in entropy favors
spontaneity, leading to a more negative ΔG.
o The relationship is captured in the equation: ΔG = ΔH - TΔS, where T is the temperature.
7. Which type of bond links monosaccharides to form polysaccharides?
o a) Peptide bond
o b) Phosphodiester bond
o c) Glycosidic bond
o d) Hydrogen bond
Elaboration:
o Glycosidic bonds are covalent bonds that link monosaccharides (simple sugars) together
to form polysaccharides (complex carbohydrates).
o Peptide bonds link amino acids in proteins
o Phosphodiester bonds link nucleotides in nucleic acids
8. Which of the following is a major function of nucleotides?
o a) Catalyze biochemical reactions
o b) Encode genetic information
o c) Provide structural support to cells
o d) Transport molecules across membranes
Elaboration:
o Nucleotides are the building blocks of nucleic acids (DNA and RNA), which store and
transmit genetic information
, o While nucleotides have other roles in metabolism and cell signaling, their primary
function is information storage
9. Which of the following is NOT a fundamental structural characteristic of lipids?
o a) Hydrophobic tail
o b) Hydrophilic head
o c) Presence of a phosphate group
o d) Amphipathic nature
Elaboration:
o Lipids are diverse in structure but generally have a hydrophobic tail (nonpolar) and a
hydrophilic head (polar), making them amphipathic.
o While some lipids, like phospholipids, contain a phosphate group in their head, it is not a
universal feature of all lipids
10. Which of the following elements is NOT commonly found in biological molecules?
o a) Carbon
o b) Hydrogen
o c) Oxygen
o d) Silicon
Elaboration:
o Carbon, hydrogen, oxygen, and nitrogen are the four most abundant elements in
biological molecules, forming the backbone of carbohydrates, lipids, proteins, and
nucleic acids
o Silicon, while abundant in the Earth's crust, is not a major component of living
organisms
11. What is the primary function of enzymes in biochemical reactions?
o a) Provide energy for the reaction
o b) Shift the equilibrium of the reaction
o c) Lower the activation energy of the reaction
o d) Change the ΔG of the reaction
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