1. Ms. Luaces, Honors Biology
Cellular Reactions
Ms. Luaces, Honors Biology

2. Photosynthesis What happens during the process of photosynthesis?
Why is ATP useful to cells?
What role do pigments & electron carriers play in photosynthesis?
What are the reactants and products of photosynthesis?
What factors affect photosynthesis?

3. 8.1 Energy & Life Energy is the ability to do work
Have to be able to obtain and use energy in many forms (light, heat, electricity, or chemical compounds)
One of the most important compounds that cells use to store and release energy is called adenosine triphosphate (ATP)

4. 8.1 Chemical Energy & ATP ATP is made up of: 1. Adenine
2. A 5-carbon sugar called ribose
3. 3 phosphate groups
Sometimes seen as ADP (has 2 phosphates instead of 3, and can store small amounts of energy)

5. 8.1 Chemical Energy & ATP
ATP can easily release energy (by breaking chemical bonds) or store energy (by adding chemical bonds) between its phosphate groups to supply a basic energy source for all cells
ADP will store energy when you add a phosphate
ATP will release energy when you take away a phosphate

6. 8.1 Chemical Energy & ATP How do we use the energy provided by ATP?
Carry out active transport by pumping Na+ ions out of cells and pumping in K+ ions
Contract muscles
Build proteins & respond to signals
Breathe

7. 8.1 Chemical Energy & ATP
ATP is NOT a good long-term storage molecule. Sugar molecules, like glucose, store 90 times the energy ATP does
Heterotrophs (?) & Autotrophs (?) therefore are always looking to take in/make sugar or carbs to power their cells

8. 8.2 Photosynthesis: An Overview
Energy from the sun travels to Earth in the form of light. Plants gather it in light-absorbing molecules called pigments
Plants principal pigment is chlorophyll
Chlorophyll a & b are present, and capture blue-violet and red regions of the color spectrum

9. 8.2 Photosynthesis: An Overview
Photosynthesis takes place inside organelles called chloroplasts, which contain many thylakoids arranged in stacks
Chlorophyll are found inside the thylakoid membranes
The fluid portion of the chloroplast is known as the stroma

10. 8.2 Photosynthesis: An Overview
When chlorophyll absorbs light, a large fraction of that light energy is transferred directly to electrons in the chlorophyll molecule
An electron-carrier accepts the electrons and transfers them, along with the energy, to another molecule
Photosynthesis electron-carrier is known as NADP+

11. 8.2 Photosynthesis: An Overview
Photosynthesis uses the energy of sunlight to convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products)
6CO2 + 6H2O  C6H12O6 + 6O2
(light)

12. 8.2 Photosynthesis: An Overview
Photosynthesis involves 2 kinds of reactions:
Light-dependent reaction
Requires light and water (for electrons & hydrogen ions)
Occurs in the thylakoids
Oxygen is released as a byproduct
Light-independent reaction
Doesn’t require light
Requires carbon dioxide, ATP & NADPH
Occurs in the stroma
Creates sugars and carbs

13. Let’s Get Funky!
Create a song / rap / act / drawing showing the process of Photosynthesis. Your creative imagination should include:
Light
Leaf
Chloroplast
Thylakoid
Chlorophyll
Excited Electron
NADP+
Sugar
*** If you are doing an act, you MUST have a narrator!!

14. 9.1 Cellular Respiration: Overview
Organisms get the energy they need from food
How much energy depends on the kind of food
Energy is measured in calories: the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius
Fats: 9 calories per gram
Carbs & Proteins: 4 calories per gram

15. 9.1 Chemical Energy & Food
Food must be broken down gradually to control the release of energy and create compounds such as ATP to directly power the cell
If we broke down food all at once, most of the energy would burn away in the form of heat

16. 9.1 Cellular Respiration: Overview
Cellular respiration is the process that releases energy from food in the presence of oxygen
6O2 + C6H12O6  6CO2 + 6H2O + Energy
Notice anything??

17. 9.1 Cellular Respiration: Overview
Cellular respiration has 3 main stages:
1. Glycolysis: creates very little energy
2. Krebs cycle: creates a little more energy
3. Electron transport chain (ETC): creates the majority of the energy ; directly involves the world’s most powerful electron acceptor - Oxygen

18. 9.1 Cellular Respiration: Overview
Aerobic
Anaerobic
Requires oxygen
Ex: Electron Transport Chain
Doesn’t require oxygen
Ex: Fermentation
** Glycolysis & Krebs don’t DIRECTLY use oxygen, but are involved with products/reactants of oxygen

19. 9.1Where Do These Processes Occur?
Cytoplasm
Mitochondria
Glycolysis
Krebs Cycle
Electron Transport Chain (ETC)

20. 9.1 Cellular Respiration: Overview
Cellular respiration is balanced by photosynthesis: the equations are reverse of each other
One processes gives the reactants of the other

21. 9.2 Glycolysis
The first set of reactions in cellular respiration is Glycolysis (sugar-breaking). During glycolysis:
1 molecule of glucose (6 carbon molecule)  2 molecules of pyruvic acid (3 carbon molecule)
Uses NAD+ as an electron acceptor to become NADH
Remember, Glycolysis doesn’t require oxygen!

22. 9.2 Glycolysis What does glycolysis produce? 2 ATP molecules NADH
2 pyruvic acid molecules

23. 9.2 Krebs Cycle
During Krebs, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
Also known as the citric acid cycle
Pyruvic acid is converted into acetyl-coA and then into citric acid
One molecule of glucose = 2 turns of the cycle
Uses NAD+ & FAD as electron acceptors  NADH and FADH2

24. 9.2 Krebs Cycle What are the products of Krebs cycle? 2 ATP molecules
NADH & FADH2
Carbon dioxide

25. 9.2 ETC
The electron transport chain uses high-energy electrons from glycolysis & Krebs cycle to convert ADP & ATP
NADH & FADH2 release their electrons, and as they pass down the line, they generate energy to spin something known as ATP synthase
With each rotation, the enzyme grabs an ADP molecule and attaches a phosphate group, producing ATP
Oxygen is directly involved here

26. 9.2 ETC
What are the products of ETC?
36 ATP (on average)
Water

27. Let’s Visualize
Create a table that lists the 3 steps of cellular respiration and include:
Where does it take place?
Directly requires oxygen?
What are the reactants?
What are the products?
Glycolysis
Krebs Cycle
ETC

28. 9.2 Cellular Respiration
All together, cellular respiration produces about 36 ATP, water, and carbon dioxide.
The rest of the energy is lost in the form of heat

29. 9.3 Fermentation
In the absence of oxygen, fermentation releases energy from food molecules by producing ATP
Cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid in the cytoplasm
2 types: Alcoholic and Lactic Acid Fermentation

30. 9.3 Fermentation Alcoholic Lactic Acid Used by yeasts & microorganisms
Causes bread dough to rise
Pyruvic acid + NADH  Alcohol + CO2 + NAD+
Used by bacteria & humans (when?)
Creates cheese, yogurt, buttermilk
Pyruvic acid + NADH  Lactic acid + NAD+

31. 9.3 Fermentation 3 main sources of ATP:
ATP already in the muscles: few seconds of intense activity
ATP made by lactic acid fermentation: short quick bursts of energy
ATP made by cellular respiration: exercise longer than 90 seconds

32. Let’s Practice! Study Workbook A – Pg. 97-99
Work with a buddy, answers only, one sheet of paper