Chapter 9

Chapter 9

Cellular Respiration and Fermentation

Chemical energy and food• How much energy is in food?

– When 1 gram of glucose (C6H12O6) is burned in the presence of oxygen, 3811 calories are released.

– What is a calorie? A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius.

Chemical energy and food– On a food label

Calories (with a capital “C”) represent kilocalories. 1 kilocalorie = 1000 calories.

– Cells use the energy in glucose by slowly releasing it.

Chemical energy and food• How many calories

are in 2 crackers?

• How many calories are in 6 crackers?

60,000

180,000

• This SLOW release of energy from glucose is called CELLULAR RESPIRATION

• We think of respiration as breathing…– think of breathing as gas exchange (O2 in and

CO2 out) to help you do cellular respiration – gas exchange occurs at the cellular level to

drive cellular respiration• O2 is a reactant of cellular respiration

• CO2 is a waste product of cellular respiration

– Breathing is just the way you get these gases into and out of your body.

Overview of Cellular Respiration

• Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.

Oxygen + glucose carbon dioxide + water + energy

O2 + C6H12O6 CO2 + H2O + ATP

Overview of Cellular Respiration

What is the balanced chemical equation for cellular respiration?

6O2 + C6H12O6 6CO2 + 6H2O + 36 ATP

Show up to 40 seconds

• Energy released can be in the presence of oxygen or not. When oxygen is present, more energy can be released.

• The process always begins with Glycolysis, and will be followed by another process depending on whether or not oxygen is present.

Glycolysis

Fermentation Krebs Cycle

Electron Transport Chain

O2no O2

• Mitochondria - Energy– Inner membrane is

highly folded to increase surface area

Add this into your notes!Add this into your notes!

Glycolysis (part 1)• Glycolysis is the process in which one molecule of

glucose (C6H12O6) is broken in half, producing two 3 carbon molecules of pyruvic acid (called pyruvate).

• Uses 2 ATP molecules but 4 ATP molecules are created. Net gain: 2 ATP

Glycolysis

• Glycolysis uses an electron carrier called similar to NADP+ called NAD+.

• Similarly, the way it carries electrons is:

NAD+ + 2 electrons + H + NADH

• Glycolysis occurs in the cytoplasm.

Play video!

Fermentation (part 2 option 1)• Fermentation also occurs in the cytoplasm.• Fermentation is the process by which cells

release from food molecules in the absence of oxygen (anaerobic).

• After glycolysis, if there is no oxygen, fermentation may occur. Fermentation itself does not produce ATP, but it regenerates NAD+ to propel more glycolysis which does create ATP.

There are two types of fermentation:

a. Alcoholic fermentation: used by yeast. It produces alcohol as waste. It uses pyruvic acid produced in glycolysis.

pyruvic acid + NADH alcohol + CO2 + NAD+

• We can use this to help us make things such as bread and wine

There are two types of fermentation:

• b. Lactic acid fermentation:occurs in cells other than yeast. Process produces lactic acid.

pyruvic acid + NADH lactic acid + NAD+

• During rigorous exercise, your body gets behind in getting oxygen to your muscle cells.

• Your muscles switch from aerobic respiration (using oxygen) to anaerobic fermentation (does not use oxygen).

• Lactic acid can build up in your muscles- you feel a painful, burning sensation and may feel sore.

• Lactic acid is also used by bacteria that are used to produce yogurt and other foods.– Also used to make sourdough breads,

sauerkraut, pickles and olives

yogurt

Sauerkraut

Aerobic Cellular Respiration(part 2 option 2)

• The remaining 90% of the energy from the glucose molecule that was not used in glycolysis is used in the part of cellular respiration that requires oxygen (aerobic).

The Krebs Cycle

• breaks down pyruvic acid from glycolysis into carbon dioxide (CO2) releasing energy as ATP, NADH, and FADH2.– ATP stores energy in its phosphate bonds– NADH and FADH2 store energy from high-

energy electrons.

Play until 1:20

In the Electron Transport Chain,

• the energy from electrons that is stored in NADH and FADH2 is transferred between electron carrier molecules and is used to make ATP.– Used: O2, NADH, FADH2

– Produced: ATP, H2O

• The Krebs Cycle and Electron Transport Chain occur in the mitochondria.

The Totals• Cellular respiration produces 36 ATP molecules.• More ATP is produced with oxygen than without.

Cellular respiration is more efficient using oxygen.

2 2 32

Energy and Exercise: Quick Energy

• Running a short race, you use ATP in your muscles, and produce new ATP by lactic acid fermentation and cellular respiration.

• When sprinting, you produce most of your ATP using lactic acid fermentation because you have run out of oxygen for the Krebs cycle.

• You breathe heavily after you finish a race to rebuild your ATP supply.

Energy and Exercise: Long-term Energy

• When running a long race, you use carbohydrate energy stored as glycogen from your muscles and other tissues. This will give you enough energy for up to 20 minutes of activity.

• After using up glycogen, your body will use up fats for energy.

• Aerobic exercises like running and swimming are beneficial for weight control.

Comparing Photosynthesis and Cellular Respiration

• If storing energy is compared to money in a savings account, photosynthesis deposits the energy and cellular respiration withdraws the money.

• Cellular Respiration is the reverse reaction of photosynthesis.

• What is the formula for photosynthesis?– 6CO2 + 6H2O + light 6O2 + C6H12O6

• What is the formula for cellular respiration (think about the opposite)?– 6O2 + C6H12O6 6CO2 + 6H2O + ATP

– Photosynthesis uses CO2 in the atmosphere, but cellular respiration puts it back

– Photosynthesis releases O2 into the atmosphere but cellular respiration using O2 to release energy from the food

– Cellular respiration occurs in all eukaryotes and some prokaryotes

– Photosynthesis occurs only in plants, algae, and some bacteria. Other organisms (heterotrophs) get their food by consuming other organisms.