Photosynthesis and respiration are reactions that complement each other in the environment. They are in reality the same reactions but occurring in reverse. While in photosynthesis carbon dioxide and water yield glucose andoxygen, through the respiration process glucose and oxygen yield carbon dioxide and water. They work well since living organisms supply plants with carbon dioxide which undergoes photosynthesis and produces glucose and these plants and bacteriagive out oxygen which all living organisms need for respiration. Photosynthesis is a process that converts carbon dioxide into organic compounds in presence of sunlight. Respiration is the set of metabolic reactions that take in cells of living organisms that convert nutrients like sugar into ATP (adenosine tri phosphate) and waste products. Processes in photosynthesis are divided on basis of requirement of sunlight while respiration processes are divided on basis of requirement of oxygen. Hence in photosynthesis you have the light dependent reactions and the dark reactions while inrespiration there is aerobic respiration and anaerobic respiration. In photosynthesis light dependent reactions, ultra violet light strikes chlorophyll pigments which excites electrons leading to separation of oxygen molecules from carbon dioxide. In the dark reactions, carbon molecules now independent of oxygen are converted into carbohydrates and stored in plant cells as energy and food source. In aerobic cellular respiration oxygen is utilized to convert organic compounds into energy and in anaerobic respiration converts organic compounds into energy without using oxygen.

1. Photosynthesis
and Cellular
Respiration
Biology
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2. Energy and Livings Things
All organisms require energy to carry out life processes.
Most of the energy used by life on Earth comes from the sun.
You get energy from the food you eat.
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3. How energy flows in living systems
light energy  plant  rabbit  fox
[sun  plants  animals  other animals]
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4. Why do we need energy?
Energy is required for:
Growth
Reproduction
Movement
Transport of materials across the cell membrane
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5. Plants and animals need each other to survive.
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6. Storing Energy
Photosynthesis - light energy converted to chemical energy
--- The atmospheric by-product of photosynthesis is oxygen (O2)
Autotrophs – organism that uses energy from sunlight or inorganic compounds to make
organic compounds (ex: plants, algae,
deep sea organisms)
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7. Breakdown Energy
Cellular Respiration – process by which cell produces energy (ATP) from food
Heterotrophs – organisms that get energy from food by organic molecules (food) being
broken down through cellular respiration
---have to consume other organisms to get energy!!!
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8. ATP (Adenosine Triphosphate)
3 (tri) Phosphate groups provide energy
When one phosphate is removed than energy is released
The phosphate groups are negatively charged and repel
each other
Most of the energy that drives metabolism is supplied by
ATP
“energy currency”
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10.  “photo” – Greek for light
 “synthesis” – to make (Calvin Cycle)
Where photosynthesis occurs
in a leaf
a.k.a mesophyll
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Photosynthesis

11. What is photosynthesis?
 Process plants use to make their own food
 Plant cells contain chloroplast
 Chloroplasts make photosynthesis possible
• Occurs in cell membranes in certain prokaryotes
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12. Stages of Photosynthesis
Light Dependent Reactions
1. Absorption of light
2. Conversion of light
 Electron Transport Chain (ETC)
 Makes ATP and NADPH (carries high energy electrons needed to make organic molecules)
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13. Stages of Photosynthesis
Light Independent Reactions
3. Storage of energy
 Calvin Cycle
 ATP and NADPH get fuel from ETC
 Sugars are produced from carbon atoms (CO₂) and hydrogen atoms (NADPH)
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14. Light Dependent
Rxns
Light Independent
Rxns
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15. Chemical Formula
Must know the ENTIRE equation of
photosynthesis
6 CO2 + 6 H2O + light  C6H12O6 +6O2
reactants products
Major
atmospheric by-product!
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16. Light Dependent Reactions
Electron Transport Chain
Occurs in thylakoids – clusters of pigment (ex: chlorophyll, which absorbs green & yellow, &
carotenoids, which absorb red & orange
Grana – stacks of thylakoids
Pigments absorb light
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17. Diagram of Light Dependent Reactions
 Note the arrows and circled molecules entering and leaving.
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18. Steps in Light Dependant Reactions
1. light absorbed by chlorophyll
2. electrons excited and transfer electrons and hydrogen from
H2O to NADP+  NADPH (electron carrier)
3. ADP + P  ATP
4. ATP and NADPH power light independent reaction
 Required by dark reactions to generate sugars
 (note: does not use CO2)
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19. Light Independent Reactions
Calvin Cycle
Occurs in the stoma —an opening in a leaf or stem that enables gas exchange
Series of enzyme-assisted chemical reactions that produces a three-carbon sugar
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20. Light Independent Reactions
 Take CO2 from air and make sugar (glucose, starch)
 Requires ATP, NADPH from ETC
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21. Cellular Respiration
The process in which chemical energy stored in food molecules (carbohydrates, protiens, and
fats) is released.
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22.  Aerobic – w/oxygen
 Anaerobic – w/out oxygen
 Occurs outside & inside of mitochondria
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Metabolic processes

23. Stages of Cellular Respiration
1. Stage One---Glycolysis
• Glucose pyruvate
2. Stage Two---Aerobic and Anaerobic Respiration
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24. Stage One - Glycolysis
- breaks down glucose to 2 pyruvates
- Why?
- Glucose (6-C) is too big to fit into the mitochondria
- Pyruvates are only 3 carbons!
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25.  Enzyme assisted anaerobic process that breaks down glucose
(6-C) to pyruvate (3-C)
 Requires energy to start breaking glucose down:
 Input 2 ATP
 Output 4 ATP
 Net Gain 2 ATP
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Glycolysis

26. Where Glycolysis occurs?
 In cytoplasm, outside of mitochondria
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27.  Occurs w/in the mitochondria
Stage Two – Kreb’s Cycle
 NADH and FADH2 now contain energy that was in glucose and pyruvate
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28. Kreb’s Cycle
 Starts with 2 carbon molecule
 4 carbon molecule is recycled at the end
 Makes 3 NADH, 1 ATP, 2 CO2 , and 1 FADH2
 NO NADPH!!!
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29. Stage Three – Electron Transport Chain
 Occurs w/in mitochondria
 Aerobic respiration
 Receives NADH & FADH2 from glycolysis and Kreb’s cycle
 Uses electrons to convert ADP + Pi to ATP
 H ions, spent e-, and oxygen molecules form H2O
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30. **(Note pathway of e-)**
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31. What happens when oxygen is not present?
Fermentation occurs
 Anaerobic process
 Occurs in cytoplasm (outside of mito.)
Two Types:
 Lactic Acid Fermentation
 Alcohol Fermentation
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32. Lactic Acid Fermentation
 Prokaryotes have over a dozen kinds of fermentation (yogurt, cheese)
 Pyruvate  lactate
 Allows glycolysis to continue in anaerobic conditions
 Blood removes excess lactate
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33. Alcohol Fermentation
 Pyruvate  ethanol
 CO2 is released, e- transferred to make ethanol
 Yeast is used to prepare certain foods and beverages
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35. Production of ATP
 Total amount of ATP depends on presence of oxygen
For each glucose molecule in aerobic respiration
 Glycolysis (outside) – net 2 ATP
 Kreb’s Cycle (inside) – 2 ATP
 ETC (inside) – 34 ATP
TOTAL ATP: 38
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36. Production of ATP (cont…)
Anaerobic Respiration
 No oxygen present
 Glycolysis (outside) – net 2 ATP
 Fermentation (outside) – no ATP
 No oxygen for H+ and e- to bind to, so go to make ethanol or lactate
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37. Overall Pathway of Cell Respiration
2 ATP in
4 Net Gain = 2 ATP
Outside mitochondria Inside mitochondria
38 Total
(a.k.a glucose)
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38. Importance of Oxygen
 Remember, oxygen is needed to bond H+ and e- to make H2O
 In Fermentation, no oxygen means H+ and e- go to lactate or ethanol
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39. The chlorophyll absorbs the sunlight.
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40. The sunlight is combined with water, Carbon Dioxide and
nutrients from the soil.
CO2
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41. The chlorophyll processes the ingredients and makes sugar
(plant food) and oxygen.
Sugar + Air
O2
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42. Animals including humans make the CO2 (carbon
dioxide) plants need.
They (the plants) make the O2 (oxygen) and food
we need.
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