Thermodynamics & Energy Flow
Energy is officially defined as the capacity to do what? A) Create matter
B) Do work
C) Increase entropy
D) Store heat
B) Do work
In the formula G=H−TS, the letter "G" represents what?
A) Total Heat
B) Absolute Temperature
C) Free energy available to do work
D) Unavailable energy
C) Free energy available to do work
ATP is composed of a five-carbon sugar called ribose, a nitrogenous base called adenine, and how many phosphate groups?
A) One
B) Two
C) Three
D) Four
C) Three
Enzymes are biological catalysts that speed up reactions by doing what?
A) Increasing the ΔG
B) Lowering the activation energy
C) Raising the temperature of the cell
D) Consuming the reactants
B) Lowering the activation energy
Reactions that expend energy to build up complex molecules from smaller ones (biosynthesis) are called:
A) Catabolic reactions
B) Anabolic reactions
C) Redox reactions
D) Spontaneous reactions
B) Anabolic reactions
According to the First Law of Thermodynamics, energy cannot be created or destroyed, it can only be _____________.
A) Divided
B) Eliminated
C) Transformed
D) Lost forever
C) Transformed
A reaction that has a negative ΔG (ΔG<0) and releases energy spontaneously is described as:
A) Endergonic
B) Enthalpic
C) Exergonic
D) Active
C) Exergonic
Why is ATP not suitable for long-term energy storage compared to fats or carbohydrates?
A) It contains too much carbon
B) Its phosphate bonds are too unstable
C) It is too large to fit in cells
D) It cannot be recycled
B) Its phosphate bonds are too unstable
When a substrate binds to an enzyme, the enzyme undergoes a slight conformational change to hold the substrate more tightly. This is called:
A) Denaturation
B) Competitive binding
C) Induced fit
D) Lock-and-key rigidity
C) Induced fit
In a biochemical pathway, the product of one reaction becomes the ________ for the next reaction in the sequence.
A) Inhibitor
B) Catalyst
C) Substrate (reactant)
D) Coenzyme
C) Substrate (reactant)
The Second Law of Thermodynamics states that energy transformations are not 100% efficient because some energy is always lost as heat, which increases _____________.
A) Enthalpy
B) Free energy
C) Activation energy
D) Entropy (disorder)
D) Entropy (disorder)
Using the "OILRIG" mnemonic, "Oxidation" refers to the ______ of an electron, while "Reduction" refers to the ______ of an electron.
A) Gain; Loss
B) Loss; Gain
C) Creation; Destruction
D) Movement; Storage
B) Loss; Gain
What is the name for the "extra" energy required to destabilize existing chemical bonds and initiate a reaction?
A) Entropy
B) Free Energy
C) Activation Energy
D) Kinetic Energy
C) Activation Energy
What typically happens to a human enzyme if it is exposed to temperatures far above 40°C?
A) It works faster
B) It turns into RNA
C) It denatures (unfolds and loses function)
D) It becomes an inhibitor
C) It denatures (unfolds and loses function)
In a process called feedback inhibition, the __________ of a pathway binds to the first enzyme to shut the pathway down and conserve resources.
A) Initial substrate
B) Intermediate A
C) End-product
D) Water molecule
C) End-product
When your muscles contract, chemical energy is converted to mechanical energy with the loss of heat. This specific loss of energy as heat is a direct example of which law?
A) First Law of Thermodynamics
B) Second Law of Thermodynamics
C) Law of Conservation of Mass
D) Third Law of Thermodynamics
B) Second Law of Thermodynamics
A reaction with a positive ΔG is nonspontaneous and requires an input of energy. This is called a(n) _________ reaction.
A) Exergonic
B) Endergonic
C) Static
D) Catalytic
B) Endergonic
Cells use exergonic ATP hydrolysis to drive endergonic cellular processes. This is known as a ________ reaction.
A) Coupled
B) Parallel
C) Reverse
D) Spliced
A) Coupled
A drug that binds to the active site of an enzyme, physically blocking the substrate from entering, is a:
A) Noncompetitive inhibitor
B) Competitive inhibitor
C) Allosteric activator
D) Coenzyme
B) Competitive inhibitor
What are "ribozymes"?
A) Protein catalysts
B) RNA molecules that function as enzymes
C) Metal ions that assist enzymes
D) Long-term energy storage molecules
B) RNA molecules that function as enzymes
While the sun is the ultimate source of energy for life, photosynthetic organisms capture this energy and store it in what form?
A) Kinetic energy in heat
B) Potential energy in chemical bonds
C) Radioactivity in the nucleus
D) Electrical currents in the soil
B) Potential energy in chemical bonds
During cellular respiration, NAD+ serves as an electron acceptor. When it gains an electron, it is ________ to NADH.
A) Oxidized
B) Hydrolyzed
C) Reduced
D) Denatured
C) Reduced
Which molecule acts as a "low energy" sensor in the cell, signaling that more ATP needs to be produced?
A) ADP
B) AMP
C) Glucose
D) NADH
B) AMP
If a drug binds to a site on the enzyme that is NOT the active site, changing the enzyme's shape so it can no longer function, it is binding to the:
A) Substrate site
B) Allosteric site
C) Transition site
D) Ribozyme site
B) Allosteric site
Small, non-protein organic molecules (often vitamins) that are necessary for some enzymes to function properly are called:
A) Cofactors
B) Coenzymes
C) Activators
D) Allosteric inhibitors
B) Coenzymes