Relationship between Photosynthesis and Cellular Respiration

1
Relationship between Photosynthesis and Cellular
Respiration

• CO2 H2O
• Photosynthesis
• (plants, algae, cyanobacteria)
• C6H12O6 O2
• Cellular Respiration
• (Eukaryotic cells)
• CO2 H2O

2
Cellular Respiration (requires O2 and gives off
CO2)

• Breakdown of glucose in the presence of oxygen to
  yield large amounts of ATP
• Occurs in the cytoplasm and mitochondria of
  eukaryotic cells
• C6H12O6 6O2 ? 6CO2 6H2O (36 ATP) (what is
  oxidixed?reduced?)
• Exergonic reaction- high energy molecule,
  glucose, produces low energy molecules 39
  efficient
• What do cells do with the ATP?

3
Cellular Respiration Occurs in 4 Phases

• Stage I Glycolysis (cytoplasm)
• Stage II Prep Stage (mitochondrial matrix)
• Stage III Citric Acid Cycle (mitochondrial
  matrix)
• Stage IV Electron Transport Chain ? oxidation-
  reduction reactions using NADH, FADH2
  (mitochondrial cristae)

4
Stage I Glycolysis

• Ancient universal reaction
• Breakdown of glucose? 2 pyruvates
• Occurs in the cytoplasm outside of mitochondria
• Anaerobic
• Requires an initial energy (2 ATPs) investment
• 4 ATPs are made by substrate level
  phosphorylation (ATP synthesis)
• Net Yield 2 ATPs, 2 NADHs

Substrate level ATP synthesis coupled reactions
5
NAD redox coenzyme, carries electrons to ETC
when O2 is available and is reused.
Substrate level ATP synthesis
When O2 is not available fermentation occurs,
with a net yield of 2 more ATP
Substrate level ATP synthesis
6
Stage II Prep Stage

• Pyruvate ? Acetyl CoA
• Occurs in the mitochondria (matrix)
• Releases 2 CO2
• Makes 2 NADH

7
Stage III Citric Acid Cycle

• A circular enzyme driven metabolic pathway that
  generates coenzymes and ATP
• Occurs in the mitochondria (matrix)
• Starts with the combination of oxaloacetate
  Acetyl CoA ? citrate
• 2 turns 2 ATPs, 6 NADH, 2 FADH2 are made
• 4 CO2 are released Glucose has been converted to
  6 CO2- 2 in prep, 4 in Citric acid cycle

Substrate level ATP synthesis
8
Stage IV Electron Transport Chain (ETC)

• Movement of electrons through a series of
  coenzyme/protein redox reactions to yield large
  amounts of ATP electrons fall from hydrogen to
  oxygen releasing energy
• Electrons (e-) are donated from NADH, FADH2 to
  the ETP
• As, e- move through the ETP, they attract H ions
  to the outer compartment of mitochondria

9
Stage IV ETC and Chemiosmosis

• A electrical and H concentration gradient is
  created (10x)
• H ions must move back from a higher? lower
  concentration
• Only return to inner compartment through ATP
  synthases, gates of the dam
• As they move through, activate ATP synthase to
  make ATP from ADP Pi
• This process is called Chemiosmosis (ATP
  production linked to H gradient)
• 1 minute reserve of ATP

10
Stage IV-ETC

• The coenzymes NADH and FADH2 give up electrons to
  the ETP
• The higher up in the ETP, the more energy
  released by those e-
• 1 NADH 3 ATP, 1 FADH2 2 ATP
• The final electron acceptor is O2, which combines
  with H ions to form H2O
• How many ATPs are made through the ETC?

11
Total ATP Yield during Cellular Respiration
Molecular Bookkeeping

• Glycolysis 2 NADH, 2 ATP
• Prep stage 2 NADH
• Citric Acid Cycle 6 NADH, 2 FADH2, 2 ATP
• ETC 34 ATP (but, substract 2 ATP from total to
  account for NADH brought in from cytoplasm) 32
  ATP net
• ATP yield from the complete breakdown of 1
  glucose 36 ATP
• 38 ATP in liver, heart, kidney cells

12
Anaerobic Respiration A Comparison to Aerobic
Respiration

• Anaerobic respiration
• Breakdown of glucose
• No oxygen required
• Low ATP yield
• Quick energy yield
• Starts and finishes in cytoplasm
• Bacteria, muscle, yeast cells

• Cellular respiration
• Breakdown of glucose
• Oxygen required
• High ATP yield
• Slow energy yield
• Starts in cytoplasm
• Finishes in mitochondria
• Animal, plant cells

13
Anaerobic Respiration Lactic Acid Fermentation

• Pyruvate ? lactate 2 ATP
• Occurs in absence of O2
• Lactobacillus (dairy products) and muscle cells
• Quick, low energy yield
• Wastes glucose, pyruvate cannot enter into Citric
  Acid Cycle

14
Anaerobic Respiration Alcoholic Fermentation

• Pyruvate ? ethanol CO2
• Occurs in absence of O2
• Low ATP yield, wastes pyruvate (glucose)
• Yeast cells (baking) and production of beer and
  wine

15
Metabolic Pool Concept

• Human diet consists of other macromolecules such
  as proteins and fats. What happens to them?
• Which of the biomolecules gives the cell the most
  ATP when completely broken down?
• How much ATP would be made from a 18 carbon fatty
  acid? 9 Acetyl CoA?
• Catabolism ? degradation
• Anabolism ? synthesis

16
Compare and Contrast Photosynthesis to Cellular
Respiration