1. Chapter 5: Photosynthesis
Process by which plants, algae, and some microorganisms harness solar energy and convert it into chemical energy
With few exceptions, all life on this planet ultimately depends on photosynthesis

2. Photosynthesis 6CO2 + 6H2O → C6H12O6 + 6O2
Specialized pigment molecules in plants capture the sun’s energy
Enzymes use the energy to build glucose (C6H12O6) from carbon dioxide (CO2)
Plant uses water in the process releasing oxygen gas (O2)
Light energy
6CO2 + 6H2O → C6H12O6 + 6O2

3. Photosynthesis
Redox – Chemical reaction where electrons are moved from H2O to CO2
Fueled by energy from the sun
Uses for glucose – about half for plant’s own cellular respiration, manufacture other compounds, store as starch or sucrose, cellulose for cell walls

4. Rise of photosynthesis radically altered Earth
Heterotrophs – organisms that obtain carbon by consuming preexisting organic molecules
Autotrophs – organisms that make their own organic compounds from inorganic compounds (water and CO2)
Rise of photosynthesis radically altered Earth
Decreased CO2, lowered global temperature, added oxygen gas to atmosphere

5. Sunlight as energy source
Electromagnetic spectrum – range of all possible frequencies of radiation
Consists of photons – discrete packets of kinetic energy
Shorter wavelengths have more energy
Sunlight
Ultraviolet (UV) – short wavelength, high energy
Visible – perceived by humans, powers photosynthesis
Infrared (IR) – long wavelength, low energy, heat

7. Photosynthesis occurs inside the cell!
Chloroplast – organelle of photosynthesis
2 outside membranes enclose stroma
Stroma – gelatinous with enzymes, ribosomes, DNA, and grana
Grana – stack of thylakoids
Thylakoid – membrane studded with photosynthetic pigments enclosing thylakoid space

9. Pigments Chlorophyll a Accessory pigments
Most abundant photosynthetic pigment in plants, algae, and cyanobacteria
Accessory pigments
Chlorophyll b
Carotenoids
Only absorbed light is photosynthetically active
Absorb red and blue
Reflect green
Accessory pigments extend used range of wavelengths used

10. 2 stages of photosynthesis Light reactions
Occur in thylakoid membranes
Convert solar energy to chemical energy
Energy from captured photons used to make ATP (stores energy) and NADPH (carries electrons)
Oxygen produced as byproduct
Carbon reactions
ATP and NADPH used to reduce CO2 to glucose
Occur in stroma
Do not require light – light-independent reactions

12. Chemiosmotic phosphorylation
Phosphorylation - adding P to ADP to make ATP
Chemiosmosis – movement of protons across membrane

13. Carbon reactions Calvin cycle assembles CO2 into glucose
Carbon fixation
PGAL synthesis
RuBP regenerated
ATP and NADPH from light reactions provide potential energy and electrons

14. C3, C4, and CAM
All plants use the Calvin cycle (C3 pathway) to make glucose
C3 plants use only the Calvin cycle
About 95% of plant species (peanuts, spinach, trees)
Photorespiration is a problem in hot, dry conditions
Rubisco uses O2 as a substrate (instead of CO2) starting a process that removes already fixed carbon
If stomata kept closed to prevent water loss, O2 builds up and photorespiration increases

16. C4 plants
CO2 combines with a 3 carbon “ferry” to form 4 carbon oxaloacetate in mesophyll
Moves into bundle sheath cells where Calvin cycle occurs
Costs 2 ATP but lose less carbon to photorespiration than C3 plants in hot, dry weather
Significant water savings
1% of plants – corn, sugarcane

18. CAM plant Crassulacean acid metabolism
Open stomata to fix carbon only at night
Store malate in vacuole
Fix it again in Calvin cycle during the day
Stored malate moves into chloroplast in the same cell
3-4% of plants
Pineapple and cacti
Saves water

19. Chapter 6: Cellular Respiration Cells use energy to make food
ATP powers every activity that requires energy input in the cell
Explains constant need for food (potential energy)
3 ATP-generating pathways
Aerobic respiration
Anaerobic respiration
Fermentation

20. Aerobic cellular respiration takes in oxygen and produces carbon dioxide
Explains why we must take oxygen into our body and get rid of carbon dioxide

21. 3 main processes of cellular respiration
Glucose oxidized and oxygen reduced
Released energy becomes trapped in ATP to be used as needed
Glycolysis – in cytoplasm - anaerobic
Krebs cycle – in mitochondria - aerobic
Electron transport chain – in mitochondria - aerobic

23. Where does cellular respiration occur?
Glycolysis occurs in cytoplasm
Prokaryotes – other reactions also happen in cytoplasm
Eukaryotes – other reactions happen in mitochondria
Outer and inner membrane
Intermembrane compartment (Cristae)
Matrix enclosed by highly folded inner membrane
ATP synthase part of inner membrane

25. Glycolysis 10 steps all in the cytoplasm
First 5 steps “activate” glucose – invest 2 ATP to get the process going
Last 5 steps produce 4 ATP
ATP produced through phosphorylation – donor molecule transfers P to ADP
Does not require oxygen (anaerobic)
Net gain of 2 ATPs
Results in 2 pyruvate and 2 NADH molecules per glucose that goes through glycolysis

27. Krebs Cycle/ Citric Acid Cycle
Pyruvate moves into mitochondria from cytoplasm
It is converted to Acetyl CoA and enters Krebs cycle
Electrons transferred to NADH and FADH2
ATP produced via phosphorylation
Carbon dioxide produced as waste product
Cell can use intermediate products to produce other organic molecules

29. Electron transport chain
Embedded in inner mitochondrial membrane
In Aerobic respiration, final electron acceptor is oxygen
oxygen forms water with hydrogen molecules from the broken-down glucose
Chemiosmotic phosphorylation
H+ removed from carriers NADH and FADH2
Pumped into intermembrane compartment creating proton gradient
Protons moving down gradient through ATP synthase powers the production of many ATP

31. Most ATP generated from chemiosmotic phosphorylation
Produces about
30 ATP total
32% of kilocalories in glucose
Rest of potential energy lost as heat

32. Proteins and lipids for energy
Glucose is not our only food; usually a cell uses amino acids from the diet to make more proteins
May use amino acids as energy source
Fats broken down into glycerol and fatty acids
Long fatty acid molecules can yield many acetyl CoA molecules
Feed into Krebs cycle

34. Life can thrive without oxygen
Anaerobic respiration
Essentially the same as aerobic respiration
Final electron acceptor is not O2
Lower ATP yield
Fermentation
Stops after glycolysis
Far less efficient than aerobic respiration
Alcoholic or lactic acid fermentation