Week 5 Quiz

A friend says, "My cells make energy when I eat breakfast." Which sentence fixes the claim using the first law of thermodynamics?

Select one.

• My cells create a small amount of new energy from each meal.
• My cells destroy the energy in food and replace it with heat.
• My cells capture energy stored in food and transfer it.
• My cells make energy only when an enzyme adds it to a reaction.

Which of these holds potential energy rather than kinetic energy?

Select one.

• An arrow in flight
• A drawn bowstring held still
• A sprinter crossing the finish line
• The heat coming off warm skin after a run

A muscle cell joins amino acids into a new protein. How should this reaction be classified?

Select one.

• Catabolic and exergonic
• Catabolic and endergonic
• Anabolic and exergonic
• Anabolic and endergonic

A molecule of adenosine is carrying two phosphates instead of three. What is it, and what state is it in?

Select one.

• ADP, the spent form that food energy can recharge
• ATP, the charged form ready to be spent
• DNA, the instruction set that stores energy
• A phosphate released by spending energy

What does an enzyme do to a reaction it speeds up?

Select one.

• It adds energy so the reaction can reach a higher end point.
• It lowers the activation energy without changing the start or the end.
• It changes which products the reaction makes.
• It is used up in the reaction, so every reaction needs a brand-new enzyme molecule.

In the catalase and temperature example (illustrative data), the room-temperature potato, at about 22 °C, made foam heights of 4, 5, and 6 cm in three trials. What is the room average?

Select one.

• 15 cm
• 6 cm
• 2 cm
• 5 cm

In the catalase and temperature example (illustrative data), the averages were 2 cm cold (about 5 °C), 5 cm at room temperature, 10 cm at body temperature (about 37 °C), and 0 cm after boiling at about 100 °C and cooling. Which explanation fits the cold and boiled results?

Select one.

• Cold slowed the enzyme, which would recover when warmed; boiling denatured it for good.
• Both the cold and the boiled samples were denatured, so neither can recover.
• The boiled sample was tested while too cold, so it only looks inactive.
• Hotter is always faster, so the boiled zero must be a failed trial.

Why does heating an enzyme far past its optimum stop it from working?

Select one.

• The heat breaks the amino-acid chain apart into many separate, single amino acids.
• The heat destroys the protein's three-dimensional shape, including its active site.
• The heat uses up the ATP stored inside the enzyme.
• The heat turns the enzyme's substrate into a different enzyme.

True or false: pepsin, the protein-digesting enzyme of the stomach, works best near neutral pH, like most human enzymes.

True or false.

• True
• False

Select every statement about enzymes that this course teaches as correct.

Select every option that applies.

• An enzyme is released unchanged after a reaction and is reused.
• The lock-and-key and induced fit pictures are both classroom models of how an enzyme grips its substrate.
• Adding more substrate keeps speeding the reaction without any limit.
• In feedback inhibition, the end product of a chain of reactions slows an earlier enzyme in that chain.
• An enzyme is used up in the reaction, the way fuel is burned.