Section 10.2 The Process of Cellular

Respiration

I Can…

• LS 1.9 I can model the relationship of mitochondrial structure to its function.

• LS 1.9 I can model the flow of matter and energy in cellular respiration including energy transfer mechanisms.

Key Questions

1. What happens during the process of glycolysis?

2. What happens during the Krebs cycle?

3. How does the electron transport chain use high-energy electrons from glycolysis and the Krebs cycle?

4. How much ATP does cellular respiration generate?

Vocabulary

• Glycolysis

• NAD+

• Krebs cycle

• Matrix

Food burns!

• Many food, like bananas, apples, and ground beef, have too much water to actually light with a match.

• Food with little water (sugar, flour, cooking oil, etc.) will burn.

• So, plenty of energy is available in food. How does a living cell extract that energy without catching fire?

• Cells release and capture that energy a little bit at a time.

Grain elevator catching fire in North Dakota

Glycolysis

• First step of cellular respiration

• “sugar-breaking”

• 1 molecule of glucose (6-carbon compound) is transformed into two molecules of pyruvic acid (3-carbon compound).

• Location- cytoplasm

Glycolysis

Glycolysis Steps

• Glucose is broken down into 2 molecules of pyruvic acid. ATP and NADH are produced as part of the process.

• ATP Production- Two ATP molecules are “invested” to get the process of glycolysis going. Overall, 4 ATP molecules are produced, for a net gain of 2 ATP per molecule of glucose.

• NADH Production- Four high-energy electrons are passed to the carrier NAD+ to produce NADH. NADH carries these electrons to the ETC.

• Read these steps while you look at the picture you drew.

Glycolysis Summary

• Products of glycolysis for one glucose: • 2 molecules of pyruvic acid

• 2 ATP molecules (net gain)

• 2 NADH molecules

Advantages of Glycolysis

• The energy yield is small, but the process is so fast that cells can produce thousands of ATP molecules in milliseconds.

• Speed is a big advantage when energy demands of a cell suddenly increase.

• The process itself does NOT require oxygen. • Glycolysis can quickly supply chemical energy to cells when oxygen is not

available.

The Krebs cycle

• In the presence of oxygen, the pyruvic acid produced in glycolysis passes to the second stage of cellular respiration.

• During the Krebs cycle, pyruvic acid in broken down in carbon-dioxide in a series of energy-extracting reactions.

• Also known as the citric acid cycle

• Location- the matrix of the mitochondria

The Krebs cycle

The Krebs Cycle Summary

• Pyruvic acid from glycolysis is used to make carbon dioxide, NADH, ATP, and FADH2.

• Because glycolysis produces 2 molecules of pyruvic acid from each glucose molecule, The Krebs cycle “turns” twice.

• Products of the Krebs cycle for one pyruvic acid:• 4 NADH

• 1 FADH2

• 1 ATP

• 3 CO2

The Electron Transport Chain (ETC)

• The electron transport chain uses the high-energy electrons from glycolysis and the Krebs cycle to synthesize ATP from ADP.

• Location- mitochondrial membrane

ETC

ETC Steps

• Electron transport- High-energy electrons from NADH and FADH2 are passed from carrier to carrier through the ETC. Water is from when oxygen accepts these electrons and an H+ ion. Energy is used to move H+ ions across the inner mitochondrial membrane and into the intermembrane space.

• ATP Production- H+ ions pass back across the mitochondrial membrane through ATP synthase, causing it to rotate. ATP synthase generates ATP from ADP.

ETC Summary

• On average, each pair of high-energy electrons that moved down the full length of the ETC provides enough energy to produce 3 molecules of ATP.

The Totals

• Cellular respiration- 36 molecules of ATP per one glucose

• Food sources• Carbs- can be broken down into sugars• Lipids and proteins can be broken down into molecules that can enter glycolysis or the

Krebs cycle. • Cells can generate ATP from just about any food source.

• How efficient is cellular respiration?• Captures 36% of total energy in glucose• 64% is released as heat

• This is why your body feels warmer after vigorous exercise • And why your body temp remains stable day and night

Total ATP from Cellular Respiration

Glycolysis, the Krebs cycle, and the electron transport chain release about 36 molecules of ATP per molecule of glucose.

2

2

32

CO2

Total ATP?

30 to 42

10.2 Exit Ticket

1. How do organisms generate ATP in aerobic and anaerobic environments?

The End