1. Chapter 6 - Cell Respiration
Metabolism - the sum of all the chemical reactions that occur in the body. It is comprised of:
anabolism – synthesis of molecules, requires input of energy
catabolism – break down of molecules, releases energy..
aerobic – occurs in the presence of oxygen
anaerobic – occurs in the absence of oxygen..

2. Energy Flow And Chemical Cycling In The Biosphere
Fuel molecules in food represent solar energy
Energy stored in food can be traced back to the sun
Animals depend on plants to convert solar energy to chemical energy
This chemical energy is in the form of sugars and other organic molecules..

3. Those organisms that consume the autotrophs are consumers.
Those organisms that convert sun energy into food energy are producers.
autotrophs - the most common carry out photosynthesis
Those organisms that consume the autotrophs are consumers.
heterotrophs..

4. Chemical Cycling Between Photosynthesis And Cellular Respiration
The ingredients for photosynthesis are CO2 and H2O
CO2 is obtained from the air by a plant’s leaves
H2O is obtained from the damp soil by a plant’s roots
Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules
O2 is a by-product of photosynthesis
Both plants and animals perform cellular respiration
Cellular respiration is a chemical process that harvests energy from organic molecules and occurs in mitochondria
The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis..

5. Sunlight
energy
Ecosystem
Photosynthesis
(in chloroplasts)
Glucose
Oxygen
Carbon dioxide
Cellular respiration
(in mitochondria)
Water
for cellular work
Heat energy

6. Oxygen is the final e- acceptor.
We have been designed to liberate energy from food molecules by aerobic cellular respiration. This process is described as aerobic because oxygen is required. Why is oxygen required?
During cellular respiration, hydrogen and its bonding electrons change partners from glucose to water.
Oxygen is the final e- acceptor.
Glucose
Oxygen
Carbon
dioxide
Water
Energy

7. Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions.
the loss of electrons (and hydrogens) is called oxidation
the gain of electrons (and hydrogens) is called reduction
[Oxygen gains electrons (and hydrogens)]
Oxidation
[Glucose loses electrons (and hydrogens)]
Glucose
Oxygen
Carbon
dioxide
Water
Reduction

8. When NAD (nicotinamide adenine dinucleotide) is reduced, a pair of hydrogen atoms donates a pair of e-, one of which then binds one proton and the other proton follows along = NADH + H+. We simplify this with NADH2..

9. Aerobic cellular respiration occurs in four stages: glycolysis transition reaction Krebs cycle electron transport pathway..

10. Glycolysis – glucose must be “activated” by the addition of two phosphate groups P . The addition of the P also traps glucose within the cell. This process occurs in the cytosol.
2ADP + Pi ATP
C6H12O C3H4O3
glucose pyruvic acid
2NAD + 4H NADH2

11. Glucose
2 Pyruvic acid

12. In animals if oxygen is not present to take the e- from NADH2, then the e- will be donated to pyruvic acid = Lactic acid pathway (anaerobic respiration).
The final product is lactic acid. This metabolic pathway only yields 2 ATP/molecule.
2 ADP+ 2
Glycolysis
Glucose
2 NAD
2 Pyruvic
acid
+ 2 H
2 Lactic

13. Various types of microorganisms perform fermentation
Yeast cells carry out a slightly different type of fermentation pathway = alcoholic fermentation
This pathway produces CO2 and ethyl alcohol
2 ADP+ 2
2 ATP
Glycolysis
Glucose
2 NAD
2 Pyruvic
acid
2 CO2 released
+ 2 H
2 Ethyl
alcohol

14. Transition reaction = pyruvic acid moves into the matrix of the mitochondrion. CO2 is cleaved off and at the same time Coenzyme A is added.Coenzyme A is derived from the vitamin pantotenic acid.
NAD + 2H NADH2
2C3H4O3 + 2CoA C2H3O-CoA + 2CO2
pyruvic acid coenzyme A acetyl-CoA carbon
dioxide

15. CoA
Pyruvic
acid
Acetic
Coenzyme A
Acetyl-CoA
(acetyl-coenzyme A)
CO2

16. Krebs Cycle
Acetic acid (2C) is added to oxaloacetic acid (4C) to form citric acid (6C). CO2 is enzymatically released. This occurs in the matrix of the mitochondria.
3NAD+6H NADH2
2C2H3O-CoA CO2
FAD+2H FADH2 2ADP+P 2ATP

17. Input
Acetic acid
ADP
3 NAD
FAD
Krebs
Cycle
Output
2 CO2

18. Electron Transport System
e- are passed along a chain of molecules to O2, which acts as the final e- acceptor.
The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mito-chondrial membrane
These ions store potential energy
When the hydrogen ions flow back through the membrane, they release energy
34 ADP+Pi 34 ATP
2 H+ + 2e- + ½ O H2O

19. If the last member of the chain remained in a reduced state, it would be unable to accept more e-. E- transport would then progress only to the next-to-last molecule. This process would continue until all of the elements of the chain remained in the reduced state. At this point, the system would stop and no ATP could be produced in the mitochondrion. With the system incapacitated, NADH2 and FADH2 could not become oxidized by donating their electrons to the chain and, through inhibition of Krebs cycle enzymes, no more NADH2 and FADH2 could be produced in the mitochondrion. The Krebs cycle would stop and respiration would become anaerobic..

20. Lipids and proteins can also be used in aerobic respiration.
Food
Polysaccharides
Fats
Proteins
Sugars
Glycerol
Fatty acids
Amino acids
Amino groups
Glycolysis
Acetyl-
CoA
Krebs
Cycle
Electron
Transport

22. Lipogenesis
Excess glucose does not complete respiration but instead is converted into glycerol and fatty acids. The acetyl-CoA subunits from the transition reaction are added together to produce fatty acids. This occurs primarily in adipose tissue and the liver..

24. Lipolysis
Triglycerides are hydrolyzed into glycerol and free fatty acids (FFA) by lipolysis.
In some tissues glycerol can be converted into phosphoglyceraldehyde.
FFAs are a major energy source and are metabolized by b-oxidation..

26. Amino Acids
Excess amino acids (a.a.) in the diet are not simply stored as additional protein – instead they are deaminated and the carbon skeleton is either respired or converted to carbohydrates or fats.
Adequate amounts of amino acids are required for growth and repair. Some a.a. can be make by rearranging parts of carbohydrates and essential a.a. A new amino acid can be obtained by transamination.
Amine group (NH2) transferred from one amino acid to form another amino acid and a keto acid.
Catalyzed by a specific enzyme (transaminase)..

29. Excess amino acids are processed for excretion by oxidative deamination. The amine group is removed and converted to urea, which is then excreted by the kidneys.

30. Not all cells can use glucose as the energy source.
Blood contains a variety of energy sources:
Glucose and ketone bodies, fatty acids, lactic acid, and amino acids.
Different tissues preferentially use different energy molecules.
Blood [glucose] maintained as many organs spare glucose.
Why??