1. Photosynthesis and Cellular Respiration
Chapter 5

2. Energy and Living Things
Section 5-1

3. Where does energy in food come from?
Directly or indirectly, all energy needed for metabolism comes from the SUN
Energy enters living systems when plants, algae and bacteria absorb sunlight
Some energy from the sun is captured to make organic compounds which are then stored
Where does energy in food come from?

4. Building molecules that store energy
Metabolism either uses energy to build molecules or break down molecules that store energy
Building molecules that store energy

5. Building molecules that store energy
Photosynthesis is the process by which light energy is converted to chemical energy
Autotrophs are organisms that use energy from sunlight or inorganic substances to make organic compounds
Most autotrophs like plants are photosynthetic
Building molecules that store energy

6. Breaking down food for energy
Chemical energy in organic compounds can transfer to organisms that consume those compounds
Heterotrophs are organisms that must get energy from food instead of directly from sunlight or inorganic substances
Cellular respiration is a metabolic process where organisms harvest energy from food

7. Cells Transfer energy from food to ATP
Cells burn energy differently than wood burns
In cells, stored energy is released in a series of enzyme assisted reactions
When cells break down food molecules, some energy is released as heat, most is released as ATP
Cells Transfer energy from food to ATP

8. ATP stores and Releases energy
ATP (adenosine triphosphate) is a nucleotide with 2 energy storing phosphate groups
Phosphate groups store energy like a spring and releases it when the bonds holding the groups together break
ATP ADP + P + Energy
ATP stores and Releases energy

9. Photosynthesis
Section 5-2

10. Photosynthetic Organisms Use Sunlight’s Energy
Plants, algae and some bacteria capture 1% of the energy in the sunlight that reaches Earth
Photosynthetic Organisms Use Sunlight’s Energy

11. Photosynthesis Overview
Stage 1: Energy is captured from sunlight
Stage 2: Light energy is converted to chemical energy; stored as ATP and the energy carrier molecule NADPH
Stage 3: Energy from ATP and NADPH powers the formation of organic compounds using carbon dioxide (CO2)
6CO2 +6H2O C6H12O6+ 6O2
Light
Photosynthesis Overview

12. First and second stage of photosynthesis are light stages
Without light, these reactions would not occur
Light energy is used to make energy storing compounds
Light Reactions

13. Pigments absorb different wavelengths of light
Pigments are molecules that absorb certain wavelengths of light and reflect others
Chlorophyll is the primary pigment involved in photosynthesis and it absorbs red and blue and reflects green and yellow
Carotenoids are pigments that produce yellow and orange fall leaf colors
Using both carotenoids and chlorophyll absorbs more light energy, so plants use both
Pigments absorb different wavelengths of light

14. Pigments used in photosynthesis are found in the chloroplast
Clusters of pigments are embedded in disk- shaped structures called thylakoids
When light strikes a thylakoid, energy is transferred to electrons in pigments and the electrons are excited
Production of Oxygen

15. Production of Oxygen cont…
Excited electrons jump from pigment molecules to others and power second stage of photosynthesis
The electrons must be replaced so water molecules split, taking electrons from hydrogen, leaving H+ and oxygen O which forms oxygen gas
Production of Oxygen cont…

17. Cellular Respiration
Section 5-3

18. Cellular Respiration Produces ATP
Oxygen makes the production of ATP more efficient
Some ATP is made without oxygen
Metabolic processes that require oxygen are called aerobic
Metabolic processes that do not require oxygen are called anaerobic
Cellular Respiration Produces ATP

19. Cellular respiration harnesses the energy in organic compounds
C6H12O  6CO2 + 6H2O + energy
Primary fuel for cellular respiration is glucose
Glucose is formed when starch or sucrose are broken down
Cellular Respiration

20. Stage 1: Glucose is broken down
Glucose (sugar) is broken down in the cytoplasm by the process glycolysis
Glycolysis is an enzyme assisted anaerobic process that breaks down one 6-carbon molecule of glucose to two 3-carbon pyruvates
Glycolysis uses 2 ATP molecules but produces 4 ATP molecules
Stage 1: Glucose is broken down

21. Step 1: Phosphate groups from 2 ATP molecules are transferred to glucose
Step 2: The 6-carbon compound is broken down into two 3-carbon compounds + 1 Phosphate
Step 3: Two NADH molecules are made 1 more phosphate group is added
Step 4: Each 3 carbon compound is converted to 3-carbon pyruvates, which produces 4 ATP
Glycolysis

23. When oxygen is present, pyruvate from glycolysis enters a mitochondria and is converted to a 2 carbon compound
This produces CO2, one NADH and a 2-carbon acetyl group
This attaches to an enzyme A (CoA) making acetyl-CoA
Acetyl-CoA enters a series of enzyme-assisted reactions called Krebs Cycle
Stage 2: More ATP is made

24. Step 1: Acetyl-CoA combines with a 4-C comp, making a 6-C comp and releasing CoA
Step 2: CO2 is released from the 6-C comp forming a 5-C comp. e- transfer making NADH
Step 3: CO2 is released from 5-C comp, making a 4-C, ATP and NADH
Step 4: 4-C comp is converted to another, and e- transfer to make electron carrier, FADH2
Step 5: 4-C comp is converted to original 4-C comp, NADH is produced and cycle can start over
Krebs Cycle

26. Electron Transport Chain
In aerobic respiration, electrons donated by NADH and FADH2 pass through electron transport chains
The chain pumps H+ out of the mitochondria which combines with O2 to make H2O
ATP is produced as H+ diffuses back into the mitochondria
Electron Transport Chain

27. Fermentation Follows Glycolysis in Absence of Oxygen
Without enough oxygen, Electron Transport Chain does not function the same
O2 receives electrons and when not present, NADH and NAD+ cannot be recycled
So NAD+ undergoes fermentation to recycle it
Fermentation Follows Glycolysis in Absence of Oxygen

28. Lactic Acid Fermentation
Lactate is the ion of an organic acid called lactic acid
A 3-C pyruvate converts to a 3-C lactate in order to continue glycolysis to produce ATP
Lactic Acid Fermentation

29. Alcoholic Fermentation
3-C pyruvate is broken down to ethanol, a 2-C compound during alcoholic fermentation
CO2 is released
Electrons transfer from NADH to the 2-C compound producing ethanol
NAD+ is recycled to continue glycolysis
Alcoholic Fermentation

30. Comparing Anaerobic with Aerobic
The total amount of ATP harvested from each glucose molecule depends on oxygen
Cells use energy more efficiently when oxygen is present
In stage 1: glucose is broken down by glycolysis (anaerobic) and gains 2 ATP
In Stage 2: pyruvate passes thru aerobic respiration or (anaerobic) fermentation
In fermentation, small amounts of ATP is produced
In respiration, up to 2 ATP are produced by Krebs cycle and 34 through electron transport chains
Comparing Anaerobic with Aerobic