Photosynthesis and Cellular Respiration Biology EasyShiksha.Com-A Way of Simple Learning
Jul 14, 2015
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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How energy flows in living systemslight energy plant rabbit fox
[sun plants animals other animals]
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Why do we need energy?
Energy is required for:
Growth
Reproduction
Movement
Transport of materials across the cell membrane
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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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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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ATP (Adenosine Triphosphate)
3 (tri) Phosphate groups provide energyWhen 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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“photo” – Greek for light
“synthesis” – to make (Calvin Cycle)
Where photosynthesis occurs in a leafa.k.a mesophyll
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Photosynthesis
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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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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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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Chemical FormulaMust know the ENTIRE equation of
photosynthesis
6 CO2 + 6 H2O + light C6H12O6 +6O2
reactants products
Major atmospheric by-product!
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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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Diagram of Light Dependent Reactions Note the arrows and circled molecules entering and leaving.
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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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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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Light Independent Reactions
Take CO2 from air and make sugar (glucose, starch)
Requires ATP, NADPH from ETC
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Cellular Respiration
The process in which chemical energy stored in food molecules (carbohydrates, protiens, and fats) is released.
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Aerobic – w/oxygen
Anaerobic – w/out oxygen
Occurs outside & inside of mitochondria
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Metabolic processes
Stages of Cellular Respiration
1. Stage One---Glycolysis
• Glucose pyruvate
2. Stage Two---Aerobic and Anaerobic Respiration
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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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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
Where Glycolysis occurs? In cytoplasm, outside of mitochondria
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Occurs w/in the mitochondria
NADH and FADH2 now contain energy that was in glucose and pyruvate
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Stage Two – Kreb’s Cycle
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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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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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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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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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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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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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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Overall Pathway of Cell Respiration
2 ATP in
4 Net Gain = 2 ATP
38 Total
Inside mitochondriaOutside mitochondria
(a.k.a glucose)
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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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The sunlight is combined with water, Carbon Dioxide and nutrients from the soil.
CO2
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The chlorophyll processes the ingredients and makes sugar(plant food) and oxygen.
Sugar + Air
O2
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