Class Starter

• List as many different forms of energy as you can. Give an example of each type of energy.

• Heat energy – warmth from wood burning in a fireplace. • Light energy – light from the sun.• Chemical energy – gasoline used to run a car engine.• Mechanical energy – energy used to power a windup

toy. • Electrical energy – electricity that runs appliances

in a home.

Objectives

• What type of energy is used in cells, and what is the ultimate source of this energy?

• How is an organism’s metabolism related to the carbon cycle?

• How is energy released in a cell?

Chapter 9 Cellular Respiration and

Photosynthesis

9.1 Energy In Living Systems

Chemical Energy

• Organisms require a constant source of energy. Energy is needed for organisms to maintain their homeostasis.

• Organisms use and store energy in the chemical bonds of organic compounds.

• Almost all of the energy in organic compounds comes from the sun.

Trace a Ham and Cheese sandwich back to the sun:

Ham → pig → grains → sun

Cheese → milk → cow → grass → sun

Bread → grain → sun

Chemical Energy, continued

Photosynthesis • the process by which plants, algae, and

some bacteria use sunlight, carbon dioxide, and water to produce carbohydrates and oxygen.

• Autotrophs : Organisms that are able to perform photosynthesis, such as plants.– make organic compounds that serve as food for

them and for almost all of the other organisms on Earth,

Chemical Energy, continued• Heterotrophs: Organisms that cannot make their

own food– must absorb food molecules made by autotrophs, eat

autotrophs, or eat organisms that consume autotrophs.

• Food molecules that are made or consumed by an organism are the fuel for its cells.

• Cells use these molecules to release the energy stored in the molecules’ bonds. The energy is used to carry out life processes.

Metabolism and the Carbon Cycle

• Metabolism involves either using energy to build organic molecules or breaking down organic molecules in which energy is stored.

• Organic molecules contain carbon. Therefore, an organism’s metabolism is part of Earth’s carbon cycle.

• Energy from the sun is converted to chemical energy in chloroplasts.

Metabolism and the Carbon Cycle, continued

• Organisms extract energy in glucose molecules.

cellular respiration • the process where cells make the carbon in

glucose into stable carbon dioxide molecules and produce energy.

• Energy is also released and used to make ATP (adenosine triphospate), an organic molecule that is the main energy source for cell processes.

Transferring Energy

• In chemical reactions,– form bonds = energy is absorbed – break bonds = energy is released

• In cells, chemical energy is gradually released in a series of chemical reactions that are assisted by enzymes.

• Enzymes are proteins that act as catalysts in biochemical reactions.

Transferring Energy, continuedATP• When cells break down food molecules, some of

the molecules is released as heat. Much of the remaining energy is used to make ATP.

• ATP is a portable form of energy “currency” inside cells.

• ATP is a nucleotide made up of a chain of three phosphate groups. When the bond of the third phosphate group is broken, energy is released, producing ADP.

ATP Releases Energy

Transferring Energy, continued

• ATP synthase: recycles ADP by bonding a third phosphate group to the molecule to form ATP.

• ATP synthase acts as both an enzyme and a carrier protein for hydrogen ions.

Transferring Energy, continued• The flow of H+ ions through ATP synthase powers

the production of ATP.

Electron transport chain:• In chloroplasts and mitochondria• a series of molecules pump H+ ions across the

membrane to create a concentration gradient.• uses energy released from electron carriers, such

as NADH and NADPH, to pump hydrogen ions.

Electron carriers

Review• What is the difference between a heterotroph

and an autotroph?• What do organic molecules contain?• What does photosynthesis require and what

does it produce from the process?• What do we require for cellular respiration?

What do we produce?• What is the energy carrying molecule in us?

How does it release energy?• What is the purpose of ATP Synthase?

Summary• Organisms use and store energy in the chemical

bonds of organic molecules.

• Metabolism involves either using energy to build organic molecules or breaking down organic molecules in which energy is stored. Organic molecules contain carbon. Therefore, an organism’s metabolism is part of Earth’s carbon cycle.

• In cells, chemical energy is gradually released in a series of chemical reactions that are assisted by enzymes.