Jennifer Naples
DI Biology

• How do you feel when you are hungry?
• Stomach growls
• Tired
• Weak
• Dizzy
• Why do you feel that way?
• Take 2 minutes to write down why your body acts the way it does when you are hungry?

• Why do we need food?
• Food provides our bodies with the chemical building blocks that we need to grow and reproduce.
• Food is a source of raw materials from which our bodies make new molecules
• Food is a source of energy

• How much energy is in food?
• A lot!
• One gram of sugar (glucose)when burned releases 3811 calories of heat energy
• A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree celcius
• The calorie(capital “C”) that is used on food labels is a kilocalorie or 1,000 calories

• Cell respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen.
• The equation cell respiration is:
• 60
2
+C
6
H
12
O
6
• oxygen+glucose
6CO
2
+6H
2
O+Energy carbon dioxide+water+energy

• Cell respiration requires oxygen and glucose
• Cell respiration releases carbon dioxide, water and energy
• There are three stages of cell respiration:
• Glycolysis
• Krebs Cycle
• Electron Transport Chain

• The first stage of cell respiration
• One molecule of glucose is broken in half
• Produces 2 molecules of pyruvic acid
• Occurs in the cytoplasm of a cell
• Requires 2 molecules of ATP to start
• Makes 2 molecules of ATP

• If there is no oxygen present glycolysis is followed by a pathway called fermentation
• Fermentation releases energy from food molecules by producing ATP in the absence of oxygen
• Fermentation is anaerobic – it requires NO oxygen

• There are two types of fermentation
• Alcoholic Fermentation and Lactic Acid
Fermentation
• Alcoholic Fermentation produces carbon dioxide and alcohol
• Causes dough to rise
• Gives of bubbles of carbon dioxide that form the air spaces that you see in bread.

• Lactic acid fermentation produces lactic acid
• Produced in your muscles during rapid exercise when the body can not supply enough oxygen to the tissues
• Without oxygen your body is not able to produce all of the ATP required.
• When you do vigorous exercise your body quickly begins to produce ATP through Lactic
Acid Fermentation.

• What is Cell Respiration?
• What are the products of glycolysis?
• What are the two main types of fermentation?
• What is a calorie? A Calorie?

• The second stage of cell respiration in the presence of oxygen
• Pyruvic acid is broken down into carbon dioxide in a series of energy extracting reactions
• Also called the citric acid cycle because citric acid is one of the compounds formed during this cycle

• The Krebs cycle occurs in the Mitochondrion
• The Krebs Cycle produces high energy electrons that are used in the next cycle of cell respiration to create large amounts of ATP
• The Krebs Cycle produces ATP

• High energy electrons that are produced in the Krebs Cycle are passed on to Electron
Transport Chain.
• Converts ADP into ATP

• Glycolysis produces 2 ATP molecules per glucose
• The Krebs Cycle produces 1 molecule of ATP
• The Electron Transport Chain produces 33 molecules of ATP
• Cellular Respiration produces 36 molecules of
ATP and uses only 2 to get started

• Quick energy like that used for a sprint is usually obtained through lactic acid fermentation
• About a 50 meter mark ATP store are used up
• Lactic acid build up is a by product of fermentation
• The only way to get rid of the build up is through a chemical pathway that requires oxygen
• That is why we breathe heavily after exercise

• What happens when you are exercising for a long period of time?
• Cell respiration is the only way to generate a continuing supply of ATP.
• Cell respiration releases energy more slowly that fermentation
• Energy is stores in muscle tissue and other tissues in the body(glycogen) which last for 15-20 minutes
• After that your body begins to break down other stored molecules including fats for energy
• That is why aerobic forms of exercise are beneficial for weight control