Getting energy to make ATP

• Process of breaking down food (glucose) to get energy.• b/c food is not the direct source of energy, it has to be

broken down by cells

• Happens in the mitochondria.

• C6H12O6 + 6 O2 6CO2 + 6H2O • Basically the opposite of photosynthesis

• Occurs 2 Ways: 1.Anaerobic

• w/o oxygen• Has 1 stage: Glycolysis

2.Aerobic • with oxygen• has 3 stages–

• Glycolysis • Krebs (citric acid) cycle • Electron transport chain• Glycolysis works the same way in both!!!

• In two parts of the cell:• Glycolysis occurs in the cytoplasm (Anaerobic)• Krebs cycle & Electron transport chain takes place in the mitochondria (Aerobic)

mitochondrion

animal cell

• Glycolysis must happen before cellular respiration can take place. – anaerobic process (does not require oxygen)

– takes place in cytoplasm

– splits glucose into two three-carbon molecules called pyruvate

– produces 2 ATP molecules

– Requires input of energy, but gets a good return*Like putting money into an account in order to gain interest*2 ATP in, 4 ATP out = 2 ATP net gain

- Fast energy production, but not long

STEP 1a

Pyruvate

Glycolysis Krebs

• The Krebs cycle transfers energy to an electron transport chain.

• takes place inmitochondrial matrix• breaks down pyruvate from

1a step glycolysis– makes 2 ATP– releases carbon dioxide– transfers energy-carrying

molecules to next step (Electron transport chain)

– Energy-carrying molecules called NADH & FADH2

– they specifically carry electrons

6H O2

6CO 2

6O 2

mitochondrionmitochondrion

matrix (area enclosedby inner membrane)

inner membrane

ATP

ATP

energy

energy from glycolysis

1

2

4

3

and

and

and

Krebs Cycle

Step 1b (requires Oxygen input after glycolysis)

Electrons transferred via NADH

6H O2

6CO 2

6O 2

mitochondrionmitochondrion

matrix (area enclosedby inner membrane)

inner membrane

ATP

ATP

energy

energy from glycolysis

1

2

4

3

and

and

and

• The electron transport chain produces 34 ATP. ( this is the 3rd & last step!)

– An ETC is made of proteins & needs energy-carrying molecules from the Krebs cycle & glycolysis

– oxygen is also needed– takes place in inner

membrane of mitochondria– 34 ATP molecules are made– Water & heat are given off as

wastes

Electron Transport Electrons transferred via NADH

• 38 ATP• 2 from Glycolysis• 2 from the Krebs (Citric Acid) Cycle• 34 from the Electron Transport Chain.

• Without oxygen (Anaerobic respiration) you only get 2 because O2 is needed for the last two stages.

• The equation for the overall process is:

C6H12O6 + 6O2 6CO2 + 6H2O

• The reactants in photosynthesis are the same as the products of cellular respiration.

6H2 O

6CO2

6O2

mitochondrionmitochondrion

matrix (area enclosedby inner membrane)

inner membraneATP

Energy carrying Compounds

(NADH, FADH2)

1

2

4

3

and

and

and

Kreb’s cycle

Glycolysis

Electron Transport Chain

ATP

ATP

Energy carrying Compounds

(NADH)