1. Photosynthesis & Cellular Respiration
Chapter 5
Photosynthesis & Cellular Respiration
Energy & Living Things, Photosynthesis and Cellular Respiration

2. Energy in Living Things
Building Molecules That Store Energy
Metabolism: builds and breaks molecules
Photosynthesis: conversion of light energy into chemical energy
Autotrophs: organisms that use sunlight or inorganic molecules to produce organic matter
These organisms include:
Plants – use sunlight
Prokaryotes – use chemicals flowing out of earth vents on the ocean floor

3. Breaking Down Food for Energy
Chemical energy can also be transferred from one organic compound to another
Ex. Hydrolysis using water to break bonds
Heterotrophs: organisms who receive chemical energy from consuming organic matter
Cellular respiration: releases energy that is contained in food to convert it to ATP (another form of energy)
ATP is the source of energy for cells to carry out their daily activities for an organism to survive

4. Transfer of Energy to ATP
Similar to burning coal or wood for heat
Food energy is released in a series of enzyme-assisted chemical reactions
The product from the previous reaction becomes the reactant in the next reaction until ATP is created
Example:
Starch is broken down into glucose and glucose is broken down into Carbon Dioxide & Water
During the reaction: heat is released

5. ATP Adenosine triphosphate Removal of a phosphate group = energy
Equation: H 2 O+ATP →ADP+P+ENERGY

6. Photosynthesis
All the energy used by organisms is traced back to the sun
Stages of Photosynthesis:
Energy is captured from the sun
Light Energy → Chemical Energy: temporarily stored in ATP and NADPH
ATP and NADPH powers the formation of organic compounds with the use of CO2
Equation:
𝟔 𝐂𝐎 𝟐 +𝟔 𝑯 𝟐 𝑶 𝒍𝒊𝒈𝒉𝒕 𝑪 𝟔 𝑯 𝟏𝟐 𝑶 𝟔 +𝟔 𝑶 𝟐

8. Stage One: Absorption of Light Energy
Light –Dependent Reactions
Pigments
Light absorbing substances
Absorb only certain wavelengths and reflect all others
Chlorophyll: absorbs blue & red, reflects green & yellow
Plants contain chlorophyll, chlorophyll a & chlorophyll b
Carotenoids: produce yellow and orange colors
Absorbs and reflect different wavelengths than chlorophyll
Enables plants to absorb more light during photosynthesis

9. Stage One: Continued Production of Oxygen
Thylakoids: disk-shaped structure containing of clusters of pigments in the chloroplast of the cell
Light strikes the thylakoids, energy is transferred to electrons and electrons move to higher levels
Electrons move from chlorophyll to nearby molecules to initiate stage two of photosynthesis.
These electrons are replaced by water molecules

10. Stage Two: The Conversion of Light Energy
Electron Transport Chain (ETC): a series of molecules that electrons pass through along the thylakoid membrane
Works around a concentration gradient – Hydrogen ions lose energy when they channel through a protein when the concentration builds within the cell, the ions diffuse out
The ions are “recharged” when they assist in adding a phosphate group to ADP to make ATP (first ETC)
In the 2nd ETC, electrons combine with hydrogen ions to create NADPH from NADP+
NADPH: electron carrier that provides high-energy electrons for stage three of photosynthesis
Look at the summary at end of this stage

12. Stage Three: Storage of Energy
Purpose: production of organic compounds from carbon atoms
Carbon Dioxide Fixation: transfer of carbon dioxide to organic compounds (light-independent reaction)
Calvin Cycle
A CO2 molecule added to a five-carbon compound (3)
Three 6-C compounds split into six 3-C compounds
One 3-C sugar is used to make organic compound
Five 3-C compounds are cycled through
Draw Calvin Cycle

13. Factors That Affect Photosynthesis
Increase
Light Intensity Increases (until saturation)
Carbon Dioxide concentration (until max)
Decrease
Slowed by the Calvin Cycle
Unfavorable conditions for enzymes

14. Cellular Respiration – Cellular Energy
Aerobic: metabolic processes that require O2
Anaerobic: metabolic processes that do not require O2
Equation of Cellular Respiration:
𝑪 𝟔 𝑯 𝟏𝟐 𝑶 𝟔 +𝟔 𝑶 𝟐 𝒆𝒏𝒛𝒚𝒎𝒆𝒔 𝟔 𝐂𝐎 𝟐 +𝟔 𝑯 𝟐 𝑶+𝑨𝑻𝑷

15. Stage One: Breakdown of Glucose
Glycolysis: enzyme assisted anaerobic process that breaks down 6-C glucose into two 3-C pyruvate ions
Step 1: In 3 rxns, phosphate groups from 2 ATP are transferred to a glucose molecule

16. Stage One: Breakdown of Glucose
Step 2: In 2 rxns, glucose broken down into two 3- carbon compounds each with a phosphate

17. Stage One: Breakdown of Glucose
Step 3: Two NADH molecules are produced and one more phosphate group is transferred to each 3-C compound

18. Stage One: Breakdown of Glucose
Step 4: In 4 rxns, each 3-C compound →→pyruvate ion and four ATP molecules are produced

19. Summary of Glycolysis Uses 2 ATP to begin
Produces 4 ATP
Net gain: 2 ATP
Glucose (6-Carbons) → Two 3-C pyruvate ions
NADH and NAD+ are recycled

20. Stage Two: Production of ATP
Oxygen present – pyruvate is converted to a 2-carbon compound in the mitochondrion
Reaction produces:
One molecule of CO2
One molecule of NADH
One 2-C acetyl group attached to form acetyl-CoA
Draw Krebs Cycle

21. Krebs Cycle A cycle beginning with acetyl-CoA to produce ATP
Step 1: Acetyl-CoA attached to a 4-C compound to form a 6-C compound and release CoA
Step 2: CO2 is released from 6-C compound forming a 5-C compound
Electrons transferred to NAD+ to make NADH
Draw Krebs Cycle

22. Krebs Cycle - Continued
Step 3: Another CO2 is released forming a 4-C compound, an ATP molecule and NADH are produced
Step 4: 4-C compound converted to a different 4-C compound.
Electrons transferred to FAD to produce FADH2
Step 5: 4-C compound converted to the original 4-C compound that started the cycle
NADH produced
Draw Krebs Cycle

23. Electron Transport Chain
Electrons are donated from NADH & FADH2
Located in the inner membrane of mitochondrion
The energy of electrons are used to pump out hydrogen ions
Concentration gradient is created - causes hydrogen ions to be pumped into the membrane
The energy created adds a phosphate group to ADP to form ATP
Products include: ATP and water molecules

24. Respiration in the Absence of Oxygen
ETC cannot function – oxygen is the final electron acceptor
NAD+ is recycled in other ways
Fermentation: recycling of NAD+ using another form of organic hydrogen acceptor
Lactic Acid
Alcoholic

25. Lactic Acid Fermentation
3-C pyruvate converted to 3-C lactate
Lactate: ion of its organic acid lactic acid
Formed during intense workouts
During the conversion:
NAD+ and NADH are recycled
No FADH2
Lactate expelled from muscles
Draw on the board

26. Alcohol Fermentation
3-C pyruvate broken down to ethanol (2-C compound)
Step 1: Pyruvate is converted to 2-C compound
Carbon dioxide expelled
Step 2: 2-C compound converted to ethanol
During break down:
NAD+ and NADH are recycled
Draw on the board