CHAPTER 9 Cellular Respiration

9-1 Chemical Pathways

Chemical Energy and Food

calorie- amount of energy needed to raise the temperature of 1 gram of water by 1° Celsius.

“Calorie”, kilocalorie- 1000 calories

1 gram of glucose when burned has 3811 calories of energy

Overview of Cellular Respiration

• 6O2 + C6H12O6 → 6CO2 + 6H2O + Energy

• Photosynthesis

6CO2 + 6H2O + Energy → 6O2 + C6H12O6

• Cellular Respiration- process the releases energy by breaking down glucose and other food molecules in the presence of oxygen

Photosynthesis and Cellular Respiration

• Photosynthesis- takes place in the chloroplast• Cellular Respiration- takes place in the

mitochondrion

Photosynthesis and Cellular Respiration

• Photosynthesis produces ATP and NADPH• Cellular Respiration produces ATP, NADH, and

FADH2

Electron Carriers• NADP+ + 2e- + H+ ↔ NADPH • NADP + Nicotinamide adenine dinucleotide

phosphate

• NAD+ + 2e- + H+ ↔ NADH • NAD + Nicotinamide adenine dinucleotide

• FAD + 2e- + 2H+ ↔ FADH2

• FAD Flavine adenine dinucleotide

3 Main Parts of Cellular Respiration

• 1. Glycolysis• 2. Krebs Cycle• 3. Electron Transport Chain

Overview

Electron Transport Chain

1. Glycolysis

• Takes place in the cytoplasm• Does NOT require oxygen• Glucose is broken down into two molecule of

pyruvate. • Two phases

• Energy investment- takes 2 ATP to get started

• Energy return

• 4 ATP are produced (gain of 2 ATP)

• 2 NADH

ATP

• ATP is adenosine triphosphate• 3 phosphate groups

• ADP (2 phosphate groups) + Phosphate group → ATP

Electron Carriers

• NAD+ + 2e- + H+ ↔ NADH • Uncharged Charged

Glycolysis

Glucose C-C-CC-C-C

C-C-CC-C-C

2 Pyruvate

4 ADP 4 ATP 2 ATP 2 ADP

2 NAD+ 2 NADH

C-C-C-C-C-C

9-2 The Krebs Cycle and Electron TransportGlycolysis :

Turns Glucose into 2 Pyruvate molecules

90% of the energy is still trapped in Pyruvate

To get this energy oxygen is needed

Aerobic respiration- with oxygen

Anaerobic respiration- without oxygen

2. The Krebs CyclePreparation• The Krebs Cycle will break down Pyruvate into

CO2 and extract energy.

• Step 1. Pyruvate enters the mitochondrion

2. The Krebs Cycle Preparation• Step 2. One CO2 molecule is released. NAD+

forms NADH. • Step 3. Coenzyme A joins the 2-Carbon

intermediate to form Acetyl CoA.

2. The Krebs Cycle Preparation• Step 4. Acetyl CoA will enter the Krebs Cycle

2. The Krebs CycleThe Cycle

Acetyl CoAC-C

CitrateC-C-C-C-C-C

C-C-C-C-C

CO2

NAD+

NADH

CO2

NADH NAD+

ATP ADP

C-C-C-C

NAD+ NADH

FADH 2

FAD

Energy Summary

For each Pyruvate• 4 NADH• 1 FADH2• 1 ATP

Pyruvate x2 from Glucose

• 8 NADH• 2 FADH2• 2 ATP

CO2 Summary

Glucose (6-Carbons)

 

Pyruvate (3-Carbons)

Krebs Cycle:

• 3 CO2 are produced

3. Electron Transport Chain

The Electron Transport Chain uses the high-energy electrons that are transported by NADH and FADH2 to convert ADP into ATP.

• The electron carriers (NADH and FADH2) transfer their high energy electrons

The electrons move from carrier protein to carrier protein until they reach a molecule of oxygen.

• Oxygen accepts the electrons and combines with H+ to form H2O.

• As the electrons moved from carrier protein to carrier protein, part of their energy was used to move H+ into the intermembrane space of the mitochondrion.

• This creates a high concentration of H+ in the intermembrane space. To return to the matrix, the H+ travel through ATP synthase. This generates ATP.

ATP Synthase

ATP Synthase joins ADP and a phosphate group to form ATP.

The H + must travel through ATP synthase. They do this to reach a level of low concentration in the matrix of the mitochondrion.

NADH and FADH2 Comparison

• NADH has electrons with more energy than the electrons of FADH2

• NADH starts the electron transport chain at an earlier point than FADH2

NADH and FADH2 Comparison

• Each NADH supplies enough energy to make 3 ATP.

• Each FADH2 supplies enough energy to make 2 ATP.

Counting up the energy

• Glycolysis- How much energy?

Glycolysis

Glucose C-C-CC-C-C

C-C-CC-C-C

2 Pyruvate

4 ADP 4 ATP 2 ATP 2 ADP

2 NAD+ 2 NADH

C-C-C-C-C-C

Counting up the energy

Glycolysis-

2 ATP

2 NADH

Krebs Cycle- How much energy?

Acetyl CoAC-C

CitrateC-C-C-C-C-C

C-C-C-C-C

CO2

NAD+

NADH

CO2

NADH NAD+

ATP ADP

C-C-C-C

NAD+ NADH

FADH 2

FAD

Counting up the energy

Glycolysis-

2 ATP

2 NADH

Krebs Cycle-

Preparation phase1 NADH

Cycle 1 ATP

3 NADH

1 FADH2

Counting up the energy

Glycolysis-

2 ATP

2 NADH

Krebs Cycle-

Preparation phase1 NADH x2

Cycle 1 ATP x2

3 NADH x2

1 FADH2 x2

Counting up the energy

Glycolysis-

2 ATP

2 NADH

Krebs Cycle-

Preparation phase2 NADH

Cycle 2 ATP

6 NADH

2 FADH2

Counting up the energyGlycolysis- ATP

2 ATP 2

2 NADH 6

Krebs Cycle-

Preparation phase2 NADH 6

Cycle 2 ATP 2

6 NADH 18

2 FADH2 4

Total: 38

How efficient is cellular respiration?

Cellular respiration can obtain about 38% of the total energy of glucose.

What happens to the other 62%?

How efficient is cellular respiration?

Cellular respiration can obtain about 38% of the total energy of glucose.

What happens to the other 62%?

Lost as heat.

Aerobic vs Anaerobic respriation

Glycolysis- What can the cell use?

Glucose C-C-CC-C-C

C-C-CC-C-C

2 Pyruvate

4 ADP 4 ATP 2 ATP 2 ADP

2 NAD+ 2 NADH

C-C-C-C-C-C

Fermentation- recycles NADH into NAD+

• Fermentation occurs without oxygen• It enables the cell to continue producing ATP with

Glycolysis.

Two types of fermentation:

Alcohol Fermentation

Lactic Acid Fermentation

Alcohol FermentationRecycles NADH

Done by yeasts and produces ethanol and CO2 as waste products.

Used to make wine, beer, and bread.

Lactic Acid FermentationRecycles NADH

Done by bacteria and fungi and produces lactate as waste.

Used to make yogurt, cheese, sour cream, pickles, sauerkraut, and kimchi.

Lactic Acid Fermentation- in Humans

Muscle cells switch from aerobic respiration to lactic acid fermentation to generate ATP when O2 is scarce.• The waste product,

lactate, may cause muscle fatigue, but ultimately it is converted back to pyruvate in the liver.

What happens when we run?

What happens when we run?

• Start to first seconds- our body only has enough ATP on hand for a few seconds of intense activity.

• First seconds to 90 seconds- after the first supply of ATP has run out, our body switches over to Lactic Acid Fermentation- it is quick but does not last long.

What happens when we run?

• 90 seconds to 15-20 minutes- your body uses glycogen that is stored in your muscle cells and processes it with cellular respiration (slower process than lactic acid fermentation).

• 20 minutes and longer- your body starts to break down other stored molecules including fats for energy.

Other molecules can be used as fuel.

Photosynthesis and Cellular Respiration