Aerobic Respiration

Chapter 9-2

Cellular Respiration

• Aerobic requires oxygen– It’s the final step

• 90% of the energy from the original glucose is still present in the 2 pyruvic acids

• 3 steps: Glycolysis, Krebs cycle, ETC

• Takes place in the mitochondria

MITOCHONDRION– Highly folded inner membrane = cristae– Liquid space inside = matrix

-Krebs cycle occurs in

the matrix

-ETC proteins are in inner membrane.

-H+ ions are pumped out of the matrix into inner

membrane space

-H+ ions then diffuse back into matrix through ATPsynthase

• Pyruvic acid is broken down into CO2 in a series of energy-extracting reactions.

The Krebs Cycle

Steps of the Krebs CycleA 1. Pyruvic acid (3C from glycolysis) enters

mitochondrion – across 2 membranes

2. 3C (pyruvic acid) splits: 1 C becomes CO2 and is released. The remaining 2C combine with coenzyme A now called acetyl CoA

3. acetyl group (2C) combines with 4C molecule (already in mitochondrion) to form citric acid (6C)

Pyruvic acid + Coenzyme A CO2 + acetyl CoA

• First step after glycolysis

• Link between glycolysis and the cycle part

Krebs Cycle cont.B 1. Citric acid (6C) loses 1carbon as CO2

and makes a 5-C molecule and NADH

2. The 5-C loses another carbon as CO2 and makes a 4-C molecule, NADH and ATP*

3. This 4-C molecule rearranges again & again, giving off Hydrogens as FADH2 and NADH

Krebs Cycle • Cycle continues :

this 4C molecule combines with acetyl CoA to start cycle

again.

• Cycle goes around once per molecule of pyruvic acid

• Therefore, it goes around twice per molecule of glucose

Krebs Cycle Outcome

PER GLUCOSE:

(2 turns of cycle)6 CO2

2 ATP

electron 8 NADH

carriers to 2 FADH2

ETC

10 pair of e-

• Click the image to play the video segment.

Video 3

Krebs Cycle, Part 1

• Click the image to play the video segment.

Video 4

Krebs Cycle, Part 2

Electron Transport ChainSection 9-2

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

Electron Transport Chain• High-energy electrons from the Krebs

cycle (carried by NADH and FADH2) are used to convert ADP to ATP

• The high-energy electrons are passed along a series of proteins embedded in the inner membrane of the mitochondria– This is in eukaryotes– Prokaryotes don’t have organelles, so this

process occurs directly in the cell membrane

Electron Transport Chain 1. NADH and FADH2 from Krebs cycle (in

matrix) transfer high energy e- to proteins of membrane.

2. e- are passed from one protein to the next in the chain. For each pair of e-, H+ ions are pumped out of matrix, across membrane, into intermembrane space.

3. When e- get to the end, an enzyme joins them with H+ ions and O2 to form water

This is why it’s aerobic!

• In order for the chain to work, there must be a molecule at the end to accept the electrons.

• Oxygen is this final electron acceptor. The electrons combine with free hydrogens to form water

Electron Transport Chain5. The H+ that were pumped into

intermembrane space begin building up, creating a positive charge

-- (likewise, the matrix is negative now)

6. This high concentration of positive charge wants to even out. The H+ ions will diffuse back across the inner membrane, through ATP synthetase.

7. As H+ move through the ATP synthetase protein, it spins, combining ADP and P to form ATP

• Click the image to play the video segment.

Video 5

Electron Transport Chain, Part 1

• Click the image to play the video segment.

Video 6

Electron Transport Chain, Part 2

TOTALS• On Average: each pair of e- along the ETC

provides enough energy to convert

3 ADP to 3 ATP1 NADH 3 ATP1 FADH2 2 ATP

Totals will depend on whether you’re talking about 1 turn of the Krebs cycle or 2 turns: 1 pyruvic acid or 2 pyruvic acid (1 glucose)

TOTAL ATPRemember: Cellular respiration includes 3

steps: glycolysis, Krebs, ETC

Per Glucose molecule:

2 ATP from glycolysis

34 ATP from Krebs/ETC = 18X more!

-----------

36 ATP total = 38% of total original energy in a glucose molecule. 62% is lost as heat

why you get warmer exercising

Exercising Stores1st stores of ATP already in cell

- enough for a few seconds2nd lactic acid fermentation

- enough for ~90seconds- builds up lactic acid & oxygen debt

3rd cellular respiration (Krebs & ETC)- long-term energy- slow release as glycogen stores are broken down (15-20 min)- after 20 min, body starts breaking down other stores (like fat)

Which forms use aerobic?

anaerobic?

• Weight-lifting• Marathon running• 50 meter dash• Playing soccer• Playing basketball

AEROBIC• Long-term, slow release• Cellular respiration

– Marathon– Soccer (80%)– Basketball (80%)

ANAEROBIC• Quick stores, used up• Lactic acid fermentation

– Weight-lifting– 50 meter dash

Tricky part…

6CO2 + 6H20 + light C6H12O6 + 6O2

C6H12O6 + 6O2 6CO2 + 6H20 + energy

Plants do both processes!

Plants have chloroplasts & mitochondria

Energy In vs. Energy OutPhotosynthesis Respiration

Function Energy Storage Energy Release

Location Chloroplasts Mitochondria

Reactants Carbon dioxide & water Sugar & oxygen

Products Sugar & oxygen Carbon dioxide & water

Equation 6CO2 + 6H20 + λ C6H12O6 + 6O2 C6H12O6 + 6O2 6CO2 + 6H20 + energy

If Oxy

gen

If no Oxygen

ProcessProcess ATPATPmademade

NADHNADHmademade

FADHFADHmademade

CO2CO2mademade

O2O2usedused

NADHNADHusedused

FADHFADHusedused

Glycolysis

Kreb’s cycle

ETC

ProcessProcess ATPATPmademade

NADHNADHmademade

FADHFADH22

mademadeCOCO22

mademadeOO22

usedusedNADHNADHusedused

FADHFADH22

usedused

Glycolysis 2 (4) 2

Kreb’s cycle

2 8 2 6

ETC 32 5 10 2

Net number (Gross number)

Extra slides

• Pyruvate (C3H4O3) Lactic Acid (C3H6O3)

Mighty-Tighty Mitochondria• 1. Obtain two sheets of paper and a metric ruler. What is

the surface area of the paper?

• 2. Roll one sheet of paper into a tube lengthwise. What is the surface area of the rolled paper?

• 3. Fold the second sheet of paper into a fan. Then, roll the firstsheet of paper around the folded paper so it is inside the rolled paper.What has happened to the surface area of the inside of the rolled paper?

• 4. What would be the value of increasing the surface area of the membrane inside a mitochondrion