Cellular Respiration

AP Biology

Photosynthesis….then• Photosynthesis captures

the sun’s energy and converts it to glucose

• Cellular respiration is the breakdown of glucose to produce ATP

• ATP is useable energy• This process is carried

out by plants and every other organism in the various trophic levels

Cellular Respiration

C6H12O6 + 6O2 6CO2 +6 H2O

This is the summary: showing beginning and end

There are three stages in between

Cellular Respiration

• Occurs in three stages:

• Glycolysis• Kreb’s Cycle• Electron Transfer

Phosphorylation• Net ATP yield

depends on whether oxygen is present

ATP Yield

• Anaerobic respiration yields two ATP

• Aerobic respiration yields 36 ATP

• Bacteria do not need much ATP

• You depend on the aerobic pathway

Glycolysis• This is the first stage

for both aerobic and anaerobic respiration

• The first energy releasing pathways to evolve were anaerobic

• Glucose is converted to pyruvate

Glycolysis

Many steps: to convert glucose into pyruvate

2 ATP invested; 4 produced

Glycolysis

• Occurs in the cytoplasm• First step requires 2 ATP• The next steps form 4

ATP by substrate level phosphorylation

• This is the direct transfer of a phosphate group from a substrate to some other molecule (in this case ADP)

• Meanwhile , NAD picks up electrons and H liberated from the PGAL

Glycolysis

• Pyruvate and NADH are used in the next stage of aerobic respiration

• If no oxygen is present, the pyruvate goes into a fermentation pathway

• Produces either lactic acid or alcohol (ethanol)

2nd stage ( Krebs Cycle)

• Pyruvate molecules enter

the inner compartment

of the mitochondria• Electrons and hydrogen

carried by NADH are transferred to many coenzymes

• A carbon is removed from each pyruvate and joins Coenzyme A, becoming Acetyl-CoA.

• This molecule enters the Krebs cycle

Krebs Cycle

• Three functions:• Loads electrons and hydrogen onto NAD+

and FAD, making 6NADH2 and 2FADH2• (This is important for ATP production in the 3rd stage)

• Forms 2 ATP• Cycles back to oxaloacetate, which is the

molecule that acetyl CoA reacts with to start the Krebs cycle

Phosphorylation

• Substrate level: production of ATP by transferring a phosphate group from an intermediate directly to an ADP

• Oxidative: production of ATP from the reactions of an electron transport chain

• Includes chemiosmosis H+ conc gradient

Substrate level phosphorylation

• An enzyme catalyses the joining of P to ADP

• Happens during glycolysis and Krebs cycle

Oxidative phosphorylation• (Each NADH

molecule represents stored energy that can “fall” down the energy gradient with oxygen as the final acceptor)

• Controlled release of energy

• The ETC creates the H+ gradient

3rd stage

• ATP formation kicks into high gear

• Uses electron transfer chains and the enzyme ATP synthase

• NADH2 and FADH2 give up electrons and hydrogen into the chains

• H+ is pumped out to create a concentration gradient. When the H+ is released, ATP is formed

GlycolysisIn the Glycolysis stage 4 ATP molecules are produced ,but 2 ATP's are used in the process so the net yield is 2 ATP's.In this stage 2 NAD's become NADH's.

Krebs CycleBEFORE the cycle 2 NADH's are created in the creation of Acetyl Coenzyme A.IN the cycle 2 GTP's are created.6 NADH's are created, & 2 FADH2's too.

Electron ChainEvery NADH produces 3 ATP's. We have 10 NADH's, therefore 30 ATP's are created.Every FADH2 produces 2 ATP's. We have 2 FADH2's, therefore 4 ATP's are created.

Total Balance 2 ATP + 2GTP +34 ATP :38 ATP Glycolysis Krebs Cycle Electron Chain Total

Alternative Energy Sources

• Proteins, broken down into amino acids, can also be broken down into pyruvate and therefore enter the Krebs cycle

• Fats, broken down into fatty acids and glycerol, can also enter the cycle at two different points, resulting in the same end result