CC27: Cellular Respiration - Do Cells Breathe?

Research has shown that treadmill training increases the activity of “energy-releasing structures” in the cells of both rats and humans. These structures are most likely:

• cell membranes

• mitochondria

• nuclei

• ribosomes

Answer explanation

Mitochondria are referred to as the “powerhouse of the cell” because they generate most of the energy needed by a cell for its activities.

Which activities are ways that humans maintain homeostasis? Select all that apply.

• In cold weather, a person’s muscles begin contracting in the form of shivers.

• During exercise, a person’s body temperature increases, and they begin to sweat.

• After getting a cut, a person’s body produces clotting factors to stop the bleeding.

Answer explanation

All these activities represent ways that the body maintains homeostasis, and they all require cellular energy.

Which description best characterizes the process of aerobic cellular respiration as it occurs in the human body?

• Carbohydrates are synthesized from molecules of carbon dioxide inside the body.

• Chemical energy stored in food molecules is converted to a form usable by cells.

• Light energy is converted into chemical energy stored in the bonds of organic molecules.

• Oxygen molecules are moved into the body’s cells via active transport processes.

Answer explanation

Cellular respiration converts the chemical energy in food to energy that cells can use, in the form of adenosine triphosphate (ATP).

The first stage of cellular respiration is glycolysis. The main role of glycolysis is to use glucose to form which molecule?

• ATP

• citric acid

• oxygen

• pyruvate

Answer explanation

The main role of glycolysis is to form pyruvate (d) out of glucose. Although ATP is a byproduct of this process, it’s a small amount compared to the ATP generated in later stages of cellular respiration.

The citric acid cycle produces “transport molecules” that fuel the final stage of cellular respiration. These molecules transport:

• carbon dioxide

• electrons

• glucose

• oxygen

Answer explanation

The transport molecules produced by the citric acid cycle, NADH and FADH2, are known as “electron carriers.” They help power the final stage of cellular respiration: oxidative phosphorylation.

The third and final stage of cellular respiration, oxidative phosphorylation, takes place at the mitochondrial membranes. Put the steps of oxidative phosphorylation in order by placing a number from 1 (first) to 4 (last) next to them.

Protons in the intermembrane space diffuse into the mitochondria through ATP synthase.​ (a)  

Proton pumps actively pump protons into the intermembrane space, creating a high concentration of protons there​ (b)  

ATP synthase is powered to phosphorylate ADP molecules, producing ATP.​ (c)  

Electrons are transferred to a series of acceptor molecules, releasing energy to power the proton pumps.​ (d)  

• 3
• 2
• 4
• 1

The electron transport chain includes a variety of “acceptor” molecules that take electrons from other molecules. At the end of the chain, what is the final acceptor molecule?

• ADP

• carbon

• oxygen

• water

Answer explanation

Oxygen is the final electron acceptor. Oxygen then combines with nearby hydrogen (H+ ), forming water.

Which processes are ways in which we can get rid of the waste products that result from cellular respiration? Select all that apply.

• exhaling

• fat storage

• urination

Answer explanation

The main waste products of cellular respiration are carbon dioxide and water. Exhaling (a) and urination (c) are two ways in which the body can remove these waste products

Oxygen is used to power cellular respiration. What similar process can be used to produce energy when oxygen isn’t available? a. b.

• aerobic respiration

• anaerobic respiration

Answer explanation

Anaerobic respiration produces energy by using molecules other than oxygen as electron acceptors. Anaerobic respiration can occur in many organisms, including humans, and is the primary mode of cellular respiration in some microorganisms.