Biology 12

CHAPTER

3

Reflecting

Questions

Cellular Energy

62

Imagine yourself running in a

distance marathon. With each step you

take, you breathe deeply. Although

you are running steadily you do not

get tired because you have been

training throughout the year. As a

result of this training, your lung

capacity has increased and your blood

can absorb a greater amount of oxygen.

Your cells, too, are ready to use the

oxygen you take in. In the presence

of oxygen, cellular organelles called

mitochondria produce energy-rich

molecules of ATP. To accomplish

this, the mitochondria use glucose

molecules. Glucose is obtained from

the food you eat and can be stored in

cells in the form of glycogen. How is

glucose used to produce molecules of

ATP? How is enough ATP produced

to carry out all necessary cellular

activity?

Photosynthetic organisms, such

as green plants, also produce ATP.

Plants, however, make their own food

— carbohydrate molecules — using

energy from the Sun, water, and

carbon dioxide. To accomplish this,

cellular organelles called chloroplasts,

shown in the inset photograph,

transform light energy into chemical

energy. This energy is used to make

carbohydrate molecules. These

molecules are then used to fuel

metabolic reactions that take place

inside mitochondria.

In this chapter you will learn how

animal and plant cells produce ATP,

the energy molecule that cells use to

do work. This process, known as

cellular respiration, involves a series

of reactions with enzymes that occur

in several systems. You will study

these systems and discover how they

function together. You will learn how

many molecules of ATP are produced

during cellular respiration. You will

also learn which organisms use

cellular respiration to produce ATP.

Finally, you will explore how diet

and exercise can influence metabolic

processes in people.

This chloroplast captures solar

energy, which is then used to make

food in green plants.

How do cells effectively

transfer energy between

reactions?

Under what conditions are

aerobic and anaerobic

cellular respiration

efficient?

How do electron transport

chains contribute to

metabolic reactions?

What are the similarities

and differences

between work done in

mitochondria and work

done in chloroplasts?

Prerequisite

Concepts

and Skills

Before you begin this chapter,
review the following concepts
and skills:

reviewing carbohydrate

structure (Chapter 1,

section 1.2),

explaining how a redox

reaction works in terms

of electronegativity

(Chapter 1, section 1.3),

applying the laws of

thermodynamics to

cellular respiration and

photosynthesis

(Chapter 2, section 2.1),

describing how enzymes

affect the activation

energy of a reaction

(Chapter 2, section 2.2).