Cellular Respiration and Fermentation Chapter 9

Cellular Respiration and Fermentation

Chapter 9

Big Idea #1

Chemical Energy and Food• Organisms get the energy

they need from food!• How do cells use this

food?– They don’t just burn food, they

break it down gradually getting all the nutrients and energy out

Chemical Energy and Food• Energy stored in food is

expressed in units of calories– The amount of energy

needed to raise 1 gram of water by 1° Celsius

– 1 gram of glucose releases 3811 calories of heat energy when it is used

Chemical Energy and Food• The Calorie (big

C) that you see on food labels is actually a kilocalorie, or 1000 calories.

Chemical Energy and Food• So only plants break down

food right?–WRONG!–All living organisms break

down energy sources–This is called cellular

respiration

Cellular Respiration• If oxygen is available, energy is

released from food• Here is a summary:

Oxygen + sugar carbon dioxide + water + ENERGY

OR

6O2 + C6H12O6 6CO2 + 6H2O + ENERGY

Cellular Respiration• There are 3

stages of cellular respiration1. Glycolysis2. Kreb’s cycle3. Electron

transport chain

Cellular respiration• These stages are called

pathways• Pathways that require

oxygen are aerobic– Kreb’s cycle– Electron transport chain

Cellular Respiration• Pathways that DO NOT

require oxygen are anaerobic–glycolysis

• Photosynthesis “deposits” the energy and cellular respiration “withdraws” that energy.

What is the relationship between photosynthesis and cellular respiration?

• Photosynthesis removes CO2 from the atmosphere and cellular respiration puts it back.

• Photosynthesis releases O2 into the atmosphere and cellular respiration uses that O2 to release energy from the food.

9.1 Quiz1. In what ways are cellular respiration and

photosynthesis considered opposite processes?

2. The Greek word glukus means “sweet,” and the Latin word lysis refers to a process of loosening or decomposing. Based on this information, write a definition for the word glycolysis.

Review• There are 3 stages of

cellular respiration1. Glycolysis

- produces only a small amount of energy.

- Most of glucose’s energy (90%) remains locked in the chemical bonds of pyruvic acid at the end of glycolysis.

Review2. Kreb’s cycle

- During the Krebs cycle, a little more energy is generated from pyruvic acid.

Review 3. Electron transport

chain- produces the bulk of the energy in cellular respiration by using oxygen, a powerful electron acceptor.

Review• Aerobic

processes require oxygen to take place– Kreb’s cycle– Electron

transport chain

Review • Anaerobic

processes DO NOT require oxygen to take place– glycolysis

The Process of Cellular Respiration

• Glycolysis is the first step of CR– Means “sugar breaking”– Involves many steps

transforming glucose– The end result is 2 molecules of

a 3-carbon molecule called pyruvic acid and 2 ATP

Glycolysis

Materials used/consumedMaterials

produced/made (net total)

2 ATP 2 ATP

1 sugar/glucose (C6H12O6) 2 NADH

  2 Pyruvic Acid

Fill in your chart:

http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html

• In the presence of oxygen, pyruvic acid produced in glycolysis moves into Kreb’s cycle– Named after

Hans A. Krebs, British biochemist

• During Kreb’s cycle, pyruvic acid is broken into carbon dioxide (CO2) in a series of energy extracting steps– This happens in the mitochondrial matrix

• 2 ATP molecules are produced, along with many electrons and CO2 molecules

Kreb's CycleMaterials used/consumed

Materials produced/made

2 pyruvic acids (2 cycles) 2 ATP

8 NADH

6 CO2

1 citric acid

Fill in your chart:

Electron Transport Chain• Electrons come from both glycolysis and

Kreb’s cycle• The electron transport chain uses the high

energy electrons from glycolysis and Kreb’s cycle to convert ADP ATP

 Electron Transport Chain: Step 3

Electron TransportHydrogen Ion Movement

ATP Production

ATP synthase

Channel

Inner Membrane

Matrix

Intermembrane Space

Mitochondrion

Electron Transport Chain• One “cycle” of the electron transport chain

yields 32 molecules of ATP

Electron Transport ChainMaterials

used/consumed Materials produced/madeNADH H2O

32 ATP

The Totals• How much energy does cellular respiration

generate?– Together, glycolysis, the Krebs cycle, and

the electron transport chain release about 36 molecules of ATP per molecule of glucose.

ATP

The Totals– Glycolysis: 2 ATP– Kreb’s cycle: 2 ATP– Electron Transport

Chain: 32 ATP• Total: 36 molecules

of ATP per 1 molecule of glucose

Fermentation

• What element does cellular respiration need to proceed?–Oxygen!

• What happens when no oxygen is available for cellular respiration?–Cells proceed into fermentation

Fermentation• In the absence of oxygen,

fermentation releases energy from food molcules by producing ATP

• There are 2 types of fermentation:– Alcoholic fermentation – Lactic acid fermentation

Fermentation• Alcoholic fermentation produces ethyl

alcohol and carbon dioxide – Yeasts and other microorganisms– Alcoholic beverages and rising bread

Pyruvic acid + NADH Alcohol + CO2 + NAD+

Fermentation• Lactic Acid Fermentation converts

pyruvic acid from glycolysis into lactic acid– Process used to make cheese, yogurt,

sour cream, pickles, kimchi– Muscle cells are lactic acid fermenters

Pyruvic acid + NADH Lactic acid + NAD+