1. Chapter 8
Cellular Energy

2. 8.1 Energy Transferring Energy- the ability to do work
Thermodynamics- the study of the flow and transformation of energy

3. Laws of Thermodynamics
1st Law states that energy can be converted from one form to another, but cannot be created nor destroyed
Ex. Stored energy is converted into chemical energy when you eat it and mechanical energy when you exercise

4. 2nd Law states that energy cannot be converted without the loss of usable energy
Ex. Energy that is lost is converted into thermal energy or heat

5. The sun All organisms need energy to live.
Where does the energy for life come from?
Autotroph- organisms use sun energy to make their own food
Heterotroph- organisms that must consume other organisms to obtain energy
The sun

7. Metabolism Metabolism- all the chemical reactions in a cell
Metabolic pathway - a series of chemical reactions in which the product of one reaction is the substrate (reactant) for the next reaction
2 types:
Anabolic- building up process that uses energy
Ex. Photosynthesis
Catabolic- breaking down process that releases energy
Ex. Cellular respiration

8. The Unit of Cellular Energy
ATP- Adenosine triphosphate, molecule that provides energy to cell
adenine + ribose + 3 phosphates
Energy is released when the bond between the 2nd and 3rd phosphate is broken; ADP is formed
ATP  ADP + P + energy

9. 8.2 Photosynthesis
Photosynthesis is the process of converting light energy from the sun into chemical energy for the cell.
6CO₂ + 6H₂O ----->C₆H₁₂O₆ + 6O₂
Photosynthesis occurs in 2 phases:
light dependent
light independent

10. Photosynthesis Process Location Reactants Products Sunlight
Light dependent reaction
(Photosystems)
Light independent reaction
(Calvin Cycle)

11. Phase 1: Light Reactions- absorption of light
Chloroplasts- large organelles found in photosynthetic organisms that capture light energy
Thylakoids- flattened saclike membranes arranged in stacks called grana
Stroma- fluid-filled space outside of the grana

12. Electron Transport
Light energy excites electrons in photosystem II which causes a water molecule to split and release an electron into the electron transport system and a hydrogen ion into the thylakoid space. Oxygen is produced as waste.
The excited electrons move from photosystem II to an electron-acceptor molecule in the thylakoid membrane.

13. The electron-acceptor molecule transfers the electron along a series of electron-carriers to photosystem I.
In the presence of light, the electron is transferred to a protein called ferrodoxin. The electrons are lost but replaced by more from photosystem II
Finally, ferrodoxin transfers the electron to the electron carrier NADP+ to form the energy-storage molecule NADPH.

14. Phase 2: The Calvin Cycle- energy is stored in organic molecules such as glucose
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.

15. 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- fix carbon into four-carbon compounds instead of three-carbon molecules during the Calvin cycle
Keeps stomata closed during hot days to minimize water loss
CAM plants- allows carbon dioxide to enter the leaves at night when its cooler and more humid
Occurs in water-conserving plants such as cacti, orchids, and pineapple

18. 8.3 Cellular Respiration
Cellular respiration- way that organisms obtain energy from food
2 parts take place in the mitochondria:
Glycolysis
Aerobic respiration

19. The chemical equation for cellular respiration is opposite from photosynthesis.

20. Electron Transport Chain
Process
Location
Reactants
Products
Glycolysis
Kreb’s Cycle
Electron Transport Chain
Total

21. Glycolysis is the 1st stage and is an anaerobic process which means it does not require oxygen.
Glucose is broken down in the cytoplasm of cells.
2 molecules of ATP and 2 molecules of NADH are formed from each molecule of glucose broken down

22. Krebs cycle- series of reactions in which pyruvate is broken down in mitochondria matrix
Glycolysis has a net result of two ATP and two pyruvate.
The net yield from the Krebs cycle is six CO2 molecules, two ATP, eight NADH, and two FADH2.

23. Electron transport-final step in breaking down of glucose in the mitochondria cristae
High-energy electrons and hydrogen ions from NADH produced in Krebs cycle are used to convert ADP into ATP.
Produces 32 molecule of ATP

24. The 2nd stage of cellular respiration is called anaerobic respiration also known as fermentation.
Two types:
Lactic acid fermentation- enzymes convert pyruvate made in glycolysis into lactic acid
Alcohol fermentation- occurs in yeast and some bacteria, pyruvate is converted into ethyl alcohol and carbon dioxide