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

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.

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.

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.

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

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

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

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.

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.

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.

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.

Chapter 8 Cellular Energy

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.

Chapter 8 Cellular Energy

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.

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.

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

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.

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

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.

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.

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.

Chapter 8 Cellular Energy

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

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