1. Cellular Respiration

2. Objectives Explain what cellular respiration is.
Describe what happens during the process of glycolysis and the Krebs cycle.
Name the two main types of fermentation.
Explain how high-energy electrons are used by the electron transport chain
Compare photosynthesis and cellular respiration

3. Energy in our food One gram of glucose = 3811 calories of heat energy
calorie – amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius
Glycolysis – literally means “sugar splitting” in the presence of oxygen, glycolysis leads to two chemical pathways that produce energy
AEROBIC – oxygen present
ANAEROBIC – no oxygen present

4. Cellular Respiration Sometimes called aerobic respiration
Process that releases energy by breaking down glucose and other food molecules IN THE PRESENCE OF OXYGEN.
3 steps
1. Glycolysis
2. Krebs cycle
3. Electron Transport Chain

5. The Equation 6O2 +C6H12O6 6CO2 + 6H2O + energy
Occurs in stages because cells must find a way to harvest the energy for later use.

6. 1. Glycolysis
WHAT: Process by which 1 molecule of glucose is broken in half producing 2 molecules of pyruvic acid.
WHERE: Occurs in the cytoplasm
HOW: Uses 2 molecules of ATP – like an investment in a savings account that pays back interest.
At completion of glycolysis 4 ATP are made (but 2 were used) for a net gain of 2 ATP.
Does NOT require oxygen – happens very quickly
If oxygen is present we move on to the next step.

7. 2. The Krebs Cycle
WHAT: Pyruvic acid is broken down into carbon dioxide and releases energy.
WHERE: Occurs in the mitochondrion
HOW: REQUIRES OXYGEN – AEROBIC
Carbon dioxide is released in your breath
Involves the high energy electron carriers NADH and FADH2

8. 3. Electron Transport Chain
WHAT: uses the high energy electron carriers from the Krebs Cycle to convert ADP to ATP.
“Excited” electrons move down the chain producing 3 molecules of ATP on average.

9. The totals
In the presence of oxygen: 36 total ATP are produced for each molecule of glucose.

10. Cellular Respiration

11. What happens if oxygen isn’t available?
If Oxygen is not present after glycolysis different chemical pathways are followed – FERMENTATION
2 TYPES of fermentation
Alcoholic fermentation
Lactic Acid fermentation

12. Alcoholic Fermentation
Occurs in yeast and a few other micro-organisms
EQUATION:
pyruvic acid +NADH alcohol +CO2 and NAD+
Causes bread to rise.
When the yeast runs out of oxygen it begins
to ferment – giving off bubbles of carbon
dioxide that form spaces in the bread
Alcohol evaporates when baked.

13. Lactic Acid Fermentation
Pyruvic acid accumulates and is converted to lactic acid.
Produced in muscles when your body cannot supply enough oxygen and there is not enough ATP available.
Causes painful burning sensations in your muscles.
Unicellular organisms produce lactic acid as a waste which are used to make a variety of foods and beverages such as butter milk, yogurt, cheese , pickles, sour cream
EQUATION:
pyruvic acid +NADH lactic acid and NAD+

14. Comparing Photosynthesis and Cellular Respiration
Function
Energy capture
Energy release
Location
chloroplasts
Mitochondrion
Reactants
Carbon dioxide and water
Glucose and oxygen
Products
Equation