Cellular Respiratio

n

Chapter

9

1. How does your body feel at the start of exercise, such as a long, slowrun? How do you feel 1 minute into the run; 10 minutes into the run?

2. What do you think is happening in your cells to cause the changesin how you feel?

3. Think about running as fast as you can for 100 meters. Could youkeep up this pace for a much longer distance? Explain your answer.

• Feel the Burn

• Do you like to run, bike, or swim? These all are good ways to exercise. When you exercise, your body uses oxygen to get energy from glucose,a six-carbon sugar.

9-1 Chemical Pathways• Food provides living things with

the chemical building blocks they need to grow and reproduce

• Food serves as a source of raw materials used to synthesize new molecules

• Food serves as a source of energy

calorie• The amount of energy needed to

raise the temperature of 1 gram of water 1 Celsius degree

Calorie• 1000 calories

Chemical Pathways

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

Glycolysis• First step in releasing energy from

glucose

Cellular Respiration• The process that releases energy

by breaking down food molecules in the presence of oxygen

The equation for cellular respiration is…

O2 + C6H12O6 +CO2 +H2O ATPOxygen Glucose Carbon

dioxideWater Energy

Glycolysis• The process in which one

molecule of glucose is broken in half producing two molecules of pyruvic acid

Glucose2 Pyruvic acid

To the electron transport chain

ATP Production

• You need to put a little energy in to get going

• 2 molecules of ATP are used up to get glycolysis going

• 4 molecules of ATP are produced at the end of glycolysis

• Net gain of 2 ATP molecules

NADH Production One of the reactions of glycolysis

removes 4 high energy electrons and passes them to a carrier called NAD+

NAD+ accepts a pair of high energy electrons and becomes NADH

NADH holds the electrons until they can be transferred to other molecules

NADH Production Energy yield from glycolysis is

small, but the process is fast

• Doesn’t require oxygen

Problems with glycolysis• NAD+ molecules fill up with

electrons quickly

• Without NAD+ the cell cannot keep glycolysis going and ATP production stops

Chemical Pathways

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

Fermentation• Releases energy from food in the

absence of oxygen

Fermentation• During fermentation, cells convert

NADH to NAD+ by passing high energy electrons back to pyruvic acid

• Changes NADH back to NAD+

• Allows glycolysis to keep producing ATP

Anerobic• Does not require oxygen

There are 2 main types of fermentation

1. Alcoholic Fermentation

2. Lactic Acid Fermentation

Alcoholic Fermentation

• Carried out by yeast

Pyruvic Acid + NADH alcohol + CO2 NAD+

FermentationYeast

Lactic Acid Fermentation

• Regenerates NAD+ so that glycolysis can continue

Pyruvic Acid + NADH lactic acid + NAD+

Glucose Pyruvic acid

Lactic Acid Fermentation

• Lactic acid is produced during rapid exercise when the body is low on O2

• You quickly run out of O2

• The buildup of lactic acid causes painful burning sensation (This is why you feel sore)

Lactic acid makes you sore

• Your body creates an oxygen debt

• You must repay that debt with heavy breathing after the exercise

Good Lactic Acid• Unicellular organisms that produce lactic

acid during fermentation are used to make• Cheese• Yogurt• Buttermilk• Sour cream• Pickles• Sauerkraut• Kimchi

Do Now• Answer the questions on pg 6 of

your Chapter 5 packet.

9-2 The Krebs Cycle and Electron Transport

• At the end of glycolysis, about 90% of the chemical energy that was available in glucose is still unused, locked in high energy electrons of pyruvic acid

• To export the rest of that energy, the cell turns to the worlds most powerful electron acceptor… Oxygen

Aerobic• Requires oxygen

• RESPIRATION• Breathing

• CELLULAR RESPIRATION• Energy releasing pathways

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

The Krebs Cycle Pyruvic Acid is broken down into

carbon dioxide in a series of energy – extracting reaction

The Krebs Cycle• CO2 released is the source of all

CO2 in your breath

• Makes ATP

• High energy electron carriers are used to make huge amounts of ATP

Glucose

Glycolysis Krebs cycle

Electrontransport

Fermentation (without oxygen)

Alcohol or lactic acid

Electron Transport• Uses the high – energy electrons

from the Krebs cycle to convert ADP into ATP

A: Electron Transport

• High – energy electrons from NADH and FADH2 are passed along the electron transport chain

• At the end of the electron transport chain is an enzyme that combines these electrons with hydrogen ions and oxygen to form water

• _____Oxygen_____serves as the final electron acceptor of the electron transport chain

B: Hydrogen Ion Movement

• Every time 2 high-energy electrons transport down the electron transport chain, their energy is used to transport hydrogen ions (H+) across the membrane.

• During electron transport, H+ ions build up in the intermembrane space, making it positively charged.

• The other side of the membrane, from which those H+ ions have been taken, is now negatively charged.

C: ATP Production

• The inner membranes of the mitochondria contain protein spheres called ATP synthases.

• As H+ ions escape through channels into these proteins, the ATP synthases spin. Each time it rotates, the enzyme grabs a low-energy ADP and attaches a phosphate, forming high-energy ATP.

• On average, each pair of high-energy electrons that moves down the electron transport chain provides enough energy to convert 3 ADP molecules into 3 ATP molecules.

Glucose(C6H1206)

+Oxygen

(02)

GlycolysisKrebsCycle

ElectronTransport

Chain

ATP+

Carbon Dioxide

(CO2)+

Water(H2O)

Cellular Respiration

The Totals• 18 times as much ATP can be

generated from glucose in the presence of oxygen

• The final wastes of cellular respiration are– CO2

– H2O

• Q: How efficient is this?• A: 38 percent of the total energy

of glucose is released.– More efficient at using food than car

engines are at burning gasoline

• Q: What happens to the rest of the energy?

• A: Given off as heat

Comparing Photosynthesis and Cellular Respiration

• They are almost the opposite processes

• Savings account analogy– Photosynthesis – “deposits energy”– Respiration – “withdraws energy”

• Photosynthesis removes CO2, cellular respiration puts it back

• Photosynthesis releases O2, cellular respiration uses O2 to release energy

THE END