Cellular Work
What is energy?
A. The ability to create matter
B. The capacity to cause change
C. The ability to destroy molecules
D. The movement of electrons only
B. The capacity to cause change
A cell moving molecules across a membrane against their concentration gradient is an example of:
A. Synthetic work
B. Concentration work
C. Mechanical work
D. Bioluminescence
B. Concentration work
Which statement correctly describes oxidation?
A. It gains electrons
B. It loses electrons
C. It always requires sunlight
D. It produces ATP directly
B. It loses electrons
What does an enzyme do?
A. Increases activation energy
B. Adds heat to the cell
C. Lowers activation energy
D. Stops chemical reactions
C. Lowers activation energy
Which equation is used to calculate Gibbs free-energy change?
A. ΔG = ΔH + TΔS
B. ΔG = ΔH − TΔS
C. ΔG = ΔH × TΔS
D. ΔG = ΔS − TΔH
B. ΔG = ΔH − TΔS
Which type of cellular work involves building new molecules and chemical bonds?
A. Synthetic work
B. Concentration work
C. Mechanical work
D. Bioluminescence
C. Mechanical work
Which organisms use sunlight as their energy source?
A. Chemotrophs
B. Heterotrophs
C. Phototrophs
D. Consumers
C. Phototrophs
Photosynthesis is best described as:
A. Catabolic and exergonic
B. Catabolic and endergonic
C. Anabolic and exergonic
D. Anabolic and endergonic
D. Anabolic and endergonic
Which statement about ΔG is correct?
A. ΔG < 0 means endergonic
B. ΔG > 0 means exergonic
C. ΔG < 0 means exergonic and thermodynamically spontaneous
D. ΔG = 0 means the reaction must happen immediately
C. ΔG < 0 means exergonic and thermodynamically spontaneous
A reaction with ΔH < 0 is:
A. Endothermic
B. Endergonic
C. Exothermic
D. Catabolic
C. Exothermic
What are the six types of cellular work?
What is the difference between autotrophs and heterotrophs?
Autotrophs make their own organic molecules from carbon dioxide. Heterotrophs get organic molecules by consuming other organisms or their products.
Explain why aerobic cellular respiration is considered both catabolic and exergonic.
Aerobic cellular respiration is catabolic because it breaks down glucose into smaller molecules. It is exergonic because that process releases energy the cell can use.
An open system exchanges both matter and energy with its surroundings. A closed system exchanges energy but not matter. Living organisms are open systems because they take in nutrients and energy and release waste and heat.
What is the difference between an exothermic and an endothermic reaction? Include the signs of ΔH.
An exothermic reaction releases heat, so ΔH is negative (ΔH < 0). An endothermic reaction absorbs heat, so ΔH is positive (ΔH > 0).
What is the difference between phototrophs and chemotrophs?
Phototrophs get energy from sunlight. Chemotrophs get energy from chemical compounds.
Explain oxidation and reduction. What does OIL RIG mean?
Oxidation is the loss of electrons, and reduction is the gain of electrons. OIL RIG helps you remember: Oxidation Is Loss; Reduction Is Gain.
What is activation energy, and why do cells use enzymes instead of simply increasing the temperature to start reactions?
Activation energy is the energy needed to start a reaction. Cells use enzymes to lower that energy barrier because raising the temperature enough could damage the cell and its proteins.
State the first law of thermodynamics and explain what it means for biological systems.
The first law of thermodynamics states that energy cannot be created or destroyed; it can only be transferred or transformed. In biological systems, cells convert energy from sunlight or food into forms they can use, but they do not create new energy.
What does ΔG tell us about a reaction? Explain what ΔG < 0, ΔG > 0, and ΔG = 0 mean.
An exothermic reaction releases heat, so ΔH is negative (ΔH < 0). An endothermic reaction absorbs heat, so ΔH is positive (ΔH > 0).
What is energy, and why is energy important to cells?
Energy is the ability to cause change. Cells need it to build molecules, move substances, and carry out the processes that keep them alive.
What is a redox reaction, and why must oxidation and reduction occur together?
A redox reaction transfers electrons between substances. Oxidation and reduction occur together because the electrons one substance loses must be gained by another.
Explain why photosynthesis is considered both anabolic and endergonic.
Photosynthesis is anabolic because it builds glucose from smaller molecules. It is endergonic because it requires energy from sunlight to do so.
What is entropy? What does a positive ΔS and a negative ΔS mean?
Entropy measures how spread out energy is in a system. A positive ΔS means entropy increases; a negative ΔS means entropy decreases.
Explain why a spontaneous reaction does NOT necessarily happen immediately. How does activation energy relate to this?
A spontaneous reaction is favorable, but it may still happen slowly. It must first overcome an activation energy barrier; if that barrier is high, the reaction will not happen immediately.