1. Chapter 9
Cellular Respiration

2. Why do we need food? Food provides living things with energy
Food serves as a source of raw materials
Food serves as a source of energy

3. Chemical Energy and Food
What is a calorie?
Amount of energy needed to raise the temp. of
1 gram of water 1 degree Celsius
The Calorie (capital C) that is used on food labels is a kilocalorie, 1000 calories
How many calories make up 1 Calorie? 1000
Cells don’t “burn” glucose, they gradually release the amount of energy inside of them (calories)

4. Chemical Energy and Food
How do our bodies release the energy from food for us to use it? Cellular Respiration
Cellular respiration begins with a pathway called glycolysis
How much energy is released through glycolysis? A small amount
*glycolysis can occur with or without oxygen

5. Overview of Cellular Respiration
Glycolysis + Krebs Cycle + Electron Transport Chain = Cellular Respiration
What is cellular respiration?
The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

6. Overview of Cellular Respiration
Equations for cellular respiration:
6O2 + C6H12O6  6CO2 + 6H2O + Energy
6 oxygen + 1 glucose  6 carbon dioxide +
6 water + Energy

7. Overview of Cellular Respiration
Cellular respiration does not take place in just one step because most of the energy would be lost as heat
The cells trap small amounts of energy in ATP molecules
There are 3 different stages of cellular respiration

8. Overview of Cellular Respiration
Glycolysis – takes place in the cytoplasm
The Krebs Cycle - takes place in the mitochondrion
The Electron Transport Chain (ETC) –
takes place in the mitochondrion

9. Workbook Pages 97 & 98 Numbers 1 – 10 only Individually
You have 15 minutes

10. Glycolysis
The first set of reactions in cellular respiration is glycolysis.
Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of
pyruvic acid (a 3-Carbon compound)

11. Glycolysis
Glycolysis is an energy releasing process, but the cell needs energy to get it started
The cell gets glycolysis going by using 2 molecules of ATP
The two molecules act as an investment – before you can begin something new, you have to start with a base

12. Glycolysis
When glycolysis is completed, 4 ATP have been produced, but there is only a net gain of 2 ATP. Why?
The cell puts in 2 ATP in the beginning
The cell produces 4 ATP through glycolysis
* 4 new ATP – 2 old ATP = 2 net ATP

13. Glycolysis
Glycolysis removes 4 high energy electrons and passes them to a carrier, NAD+
NAD+ is an electron carrier that accepts a pair of high energy electrons and transfers them to another molecule
NAD + 2 e- + 2 H+ = NADH

14. Glycolysis What is the function of NAD + in glycolysis?
To pass energy from glucose to other pathways in the cell, using the ETC (electron transport chain)

15. Glycolysis
Advantage!
Glycolysis can supply chemical energy to cells when oxygen is not available
The process of glycolysis does not require oxygen

16. Glycolysis
Advantage!
Glycolysis produces small amounts of energy very fast!
Cells can make 1000s of ATP in milliseconds!
Problem
when a cell generates a large amount of ATP, all of the NAD+ molecules fill up with electrons, and ATP production stops!

17. Workbook
Page 98
#s 11-17
Individually

18. Fermentation
When oxygen is not present, glycolysis is followed by a different pathway.
Glycolysis without oxygen Fermentation
Fermentation releases energy from food molecules by producing ATP in the absence of oxygen.

19. Fermentation
During fermentation, cells converts NADH to NAD+ by giving high-energy electrons back to pyruvic acid
NADH is converted back into the electron carrier NAD+, which allows glycolysis to continue producing a steady supply of ATP.

20. Fermentation
Fermentation does not require oxygen, so it is said to be anaerobic
The two main types of fermentation are
Alcoholic fermentation
Lactic acid fermentation

21. Fermentation Alcoholic fermentation
Yeasts and other microscopic organisms use this process
The waste products of fermentation are ethyl alcohol and carbon dioxide
The equation after glycolysis:
Pyruvic acid + NADH  alcohol + CO2 + NAD+

22. Fermentation Alcoholic fermentation is what causes bread dough to rise
When the yeast runs out of oxygen, it starts to ferment for energy – this gives off CO2 bubbles that make the air spaces in bread
The small amount of alcohol also produced in the bread evaporates when the bread is baked

23. Fermentation Lactic Acid Fermentation
Lactic acid fermentation converts glucose into lactic acid
Glycolysis breaks the glucose into 2 molecules of pyruvic acid, which are converted to lactic acid
Equation after glycolysis
Pyruvic acid + NADH  lactic acid + NAD+

24. Fermentation
Lactic acid is produced in your muscles during exercise when the body cannot supply enough oxygen to the tissues
Without enough oxygen, your body cannot supply enough ATP
Your muscle cells rapidly produce ATP by lactic acid fermentation

25. Fermentation
How do you know when your muscle cells have gone through lactic acid fermentation?
Your muscles are sore! Lactic acid buildup causes a painful, burning sensation.

26. Fermentation
Unicellular organisms also go through lactic acid fermentation
Prokaryotes (bacteria) are used in foods and drinks because they give off lactic acid as a waste product
Lactic acid is a useful ingredient in
Cheese, yogurt, buttermilk, sour cream, pickles, and sauerkraut

27. Workbook
Finish section 9-1 in your workbook