Metabolis m Photosynthesis [8.2] Cell Respiration [8.3] Fermentation [8.3]

Metabolism

Photosynthesis [8.2]Cell Respiration [8.3]Fermentation [8.3]

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.

Fermentation• Two Types:

• Alcohol Fermentation• Occurs in yeast and some bacteria• Converts pyruvate into CO2 and ethanol• NAD+ is regenerated