PhotosynthesisBiology

Chapter 8

8.1 Energy and Life• Energy is the ability to do work• What is work for cells?

• Plants, algae, and some bacteria use light energy from the sun to produce food

• a. Autotrophs b. Heterotrophs

Chemical Energy and ATP• Adenosine diphosphate, ADP• Adenosine triphosphate, ATP

*ATP is used by all types of cells as their basic energy source*When a cell has energy available, it can store small amounts of it by adding a phosphate group to ADP molecules, producing ATP*ATP is like a rechargeable battery

• Because a cell can subtract the third phosphate group, it can release energy as needed

*bond breaks energy is released• ATP has enough energy to power

cellular activities like active transport across cell membranes, protein synthesis, and muscle contraction

• Most cells have only a small amount of ATP…

• One molecule of glucose stores more than 90x the chemical energy of 1 ATP

• Cells regenerate ATP from ADP by using the energy in foods like glucose

• How do plant cells make ATP and other molecules for long-term energy?

Quick Check1. Organisms that make their own food are called A. autotrophs B. heterotrophs C. decomposers

2. How is energy released from ATP? A. A phosphate is added B. An adenine is added C. A phosphate is removed

3. Why do most cells contain only a small amount of ATP? …Cells do not need ATP for energy …ATP isn’t very good for long-term energy storage

8.2 An Overview of Photosynthesis• Plants use the energy in sunlight to turn water

and carbon dioxide into high-energy carbohydrates and oxygen.

Some experiments to consider…• Jan van Helmont devised an

experiment to find out if plants grew by taking material out of the soil

• Joseph Priestley placed a glass jar over a burning candle and watched as the flame went out. He put a live plant in the jar, and guess what happened?

• Jan Ingenhousz showed that the effect observed by Priestley occurred only when the plant was exposed to light

Pigments of Photosynthesis

• Chlorophyll-green pigment in plants that absorbs blue-violet and red, and reflects green.

• Chlorophyll is present in the chloroplasts of a plant cell.

The Structure of a Chloroplast• Light-dependent rxns. take place on the

thylakoid membrane.• Thylakoids are “pancake-like” structures.• The stacks are called grana.• The Calvin cycle takes place in the stroma (the fluid the thylakoids float in).

Making ATP using Light Energy• The energy from the sun is absorbed by

the chlorophyll in the thylakoid membrane.

• NADP+ is an electron carrier that carries high energy electrons and two hydrogen ions turns into NADPH.

• The H+ ions are created when sunlight hits the thylakoid and water is split, creating free oxygen which is a waste product.

Light Reactions (cont.)

• The NADPH carries the e- and the H+ ions to the membrane where the H+ ions are pumped inside the thylakoid. (see page 211)

•The pressure of the H+ ions builds up, and the H+ ions are forced back out of the membrane through a structure called ATP synthase.

Making ATP• As the H+ ions and

their energy move through the ATP synthase, the protein rotates and creates 3 ATPs for every turn.

Light Dependent Reactions