Photosynthesis
• Most autotrophs create energy from the sun using photosynthesis
• The overall equation is:
6CO2 + 6H2O C6H12O6 + 6O2
• This occurs in Two Phases:• Light Reaction• The Calvin Cycle
SUNLIGHT
6CO2 + 6H2O C6H12O6 + 6O2
Light-Reaction Phase:• Photosystem II
Uses energy from light to break down H2OReleases O2
• Photosystem IHarnesses electrons from broken H2O
molecules to produces NADPH
• ChemiosmosisUses H+ ions from broken H2O molecules to
harvest the energy to turn ADP into ATP
SUNLIGHT
6CO2 + 6H2O C6H12O6 + 6O2
Calvin Cycle:• Uses CO2 and the energy stored in NADPH and ATP
to produce Glucose (C6H12O6)
SUNLIGHT
Alternate Pathways
• Two alternate pathways exist: C4 plants CAM plants
The environment effects a plant’s ability to perform photosynthesis
Cellular Respiration• Function: to harvest electrons from glucose
to produce ATP
• Overall Equation:
• Three Stages:• Glycolysis• Citric Acid Cycle (CAC) [Kreb’s Cycle]• Electron Transport Chain (ETC)
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Glycolysis
• Glycolysis is anaerobic, meaning that it does not require oxygen.
• Glucose is broken down yielding:• Energy (ADP -> ATP)• Electron carriers (NADH)• Pyruvate
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Transition to the Citric Acid Cycle C6H12O6 + 6O2 6CO2 + 6H2O + ATP
• Requires oxygen (Aerobic)• Pyruvate converted to Acetyl CoA
Citric Acid (Kreb’s) Cycle
• Step 1- Acetyl CoA Citric Acid
• Step 2- Citric Acid broken down:• Energy (ADP -> ATP)• Electron carriers: NADH & FADH2
• Waste CO2
• Step 3- Acetyl CoA and Citric Acid are regenerated to repeat the cycle.
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Electron Transport Chain
• A flow of electrons from electron carriers NADH & FADH2 are used to harness energy
• ETC is Aerobic• Final electron acceptor is Oxygen • H+ + O2 = H2O
• Net 36 ATP in Eukaryotes, 38 ATP in Prokaryotes
C6H12O6 + 6O2 6CO2 + 6H2O + ATP
Anaerobic Respiration
• What happens when there is NO oxygen?
• Glycolysis can still occur• Kreb’s cycle and electron transport
cannot
• Instead, pyruvate goes into the anaerobic process known as fermentation
• Occurs entirely in the cytoplasm and regenerates NAD+
Fermentation• Two Types:
• Lactic Acid Fermentation-• Pyruvate is converted into lactic
acid• In muscle cells, occurs when body
cannot supply enough oxygen• In microorganisms this occurs to
make cheeses, yogurts, and sour cream.
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