1. Chapter 8 Cellular Energy
Section 1: How Organisms Obtain Energy
Section 2: Photosynthesis
Section 3: Cellular Respiration

2. Transformation of Energy
Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Transformation of Energy
Energy is the ability to do work.
Thermodynamics is the study of the flow and transformation of energy in the universe.

3. Laws of Thermodynamics
Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Laws of Thermodynamics
First law—energy can be converted from one form to another, but it cannot be created nor destroyed.
Second law—energy cannot be converted without the loss of usable energy.

4. Autotrophs and Heterotrophs
Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Autotrophs and Heterotrophs
Autotrophs are organisms that make their own food.
Heterotrophs are organisms that need to ingest food to obtain energy.

5. All of the chemical reactions in a cell
Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
Metabolism
All of the chemical reactions in a cell
Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell
Cellular respiration—organic molecules are broken down to release energy for use by the cell

6. ATP: The Unit of Cellular Energy
Chapter 8
Cellular Energy
8.1 How Organisms Obtain Energy
ATP: The Unit of Cellular Energy
ATP releases energy when the bond between the second and third phosphate groups is broken, forming a molecule called adenosine diphosphate (ADP) and a free phosphate group.
ATP

7. Overview of Photosynthesis
Chapter 8
Cellular Energy
8.2 Photosynthesis
Overview of Photosynthesis
Photosynthesis occurs in two phases.
Light-dependent reactions
Light-independent reactions

8. Phase One: Light Reactions
Chapter 8
Cellular Energy
8.2 Photosynthesis
Phase One: Light Reactions
The absorption of light is the first step in photosynthesis.
Chloroplasts capture light energy.

9. Chapter 8
Cellular Energy
8.2 Photosynthesis
Electron Transport
Light energy excites electrons in photosystem II and also causes a water molecule to split, releasing an electron into the electron transport system, H+ into the thylakoid space, and O2 as a waste product.

10. Chapter 8
Cellular Energy
8.2 Photosynthesis
The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane.
The electron-acceptor molecule transfers the electrons along a series of electron-carriers to photosystem I.

11. Photosystem I transfers the electrons to a protein called ferrodoxin.
Chapter 8
Cellular Energy
8.2 Photosynthesis
Photosystem I transfers the electrons to a protein called ferrodoxin.
Ferrodoxin transfers the electrons to the electron carrier NADP+, forming the energy-storing molecule NADPH.

12. Chapter 8
Cellular Energy

13. Phase Two: The Calvin Cycle
Chapter 8
Cellular Energy
8.2 Photosynthesis
Phase Two: The Calvin Cycle
In the second phase of photosynthesis, called the Calvin cycle, energy is stored in organic molecules such as glucose.

14. Chapter 8
Cellular Energy

15. Chapter 8
Cellular Energy
8.2 Photosynthesis
Six CO2 molecules combine with six 5-carbon compounds to form twelve 3-carbon molecules called 3-PGA.
The chemical energy stored in ATP and NADPH is transferred to the 3-PGA molecules to form high-energy molecules called G3P.

16. Chapter 8
Cellular Energy
8.2 Photosynthesis
Two G3P molecules leave the cycle to be used for the production of glucose and other organic compounds.
An enzyme called rubisco converts the remaining ten G3P molecules into 5-carbon molecules called RuBP.
These molecules combine with new carbon dioxide molecules to continue the cycle.

17. Alternative Pathways C4 plants CAM plants 8.2 Photosynthesis Chapter 8
Cellular Energy
8.2 Photosynthesis
Alternative Pathways
C4 plants
CAM plants

18. Overview of Cellular Respiration
Chapter 8
Cellular Energy
8.3 Cellular Respiration
Overview of Cellular Respiration
Organisms obtain energy in a process called cellular respiration.
The equation for cellular respiration is the opposite of the equation for photosynthesis.

19. Cellular respiration occurs in two main parts.
Chapter 8
Cellular Energy
8.3 Cellular Respiration
Cellular respiration occurs in two main parts.
Glycolysis
Aerobic respiration

20. Chapter 8
Cellular Energy
8.3 Cellular Respiration
Glycolysis
Glucose is broken down in the cytoplasm through the process of glycolysis.
Two molecules of ATP and two molecules of NADH are formed for each molecule of glucose that is broken down.

21. Glycolysis has a net result of two ATP and two pyruvate.
Chapter 8
Cellular Energy
8.3 Cellular Respiration
Krebs Cycle
Glycolysis has a net result of two ATP and two pyruvate.
Most of the energy from the glucose is still contained in the pyruvate.
The series of reactions in which pyruvate is broken down into carbon dioxide is called the Krebs cycle.

22. Chapter 8
Cellular Energy
8.3 Cellular Respiration
The net yield from the Krebs cycle is six CO2 molecules, two ATP, eight NADH, and two FADH2.

23. Chapter 8
Cellular Energy

24. Final step in the breakdown of glucose
Chapter 8
Cellular Energy
8.3 Cellular Respiration
Electron Transport
Final step in the breakdown of glucose
Point at which ATP is produced
Produces 24 ATP

25. Anaerobic Respiration
Chapter 8
Cellular Energy
8.3 Cellular Respiration
Anaerobic Respiration
The anaerobic pathway that follows glycolysis
Two main types
Lactic acid fermentation
Alcohol fermentation
Cellular Respiration