1. Peep video Bioflix video on cell respiration Cell respiration video

2. Cellular Respiration and Fermentation

3. Remember energy coupling?

4. Yielding Energy Catabolic processes in the cell Anaerobic respiration
Both of these comprise cellular respiration

5. How do we harvest energy from fuels?
Digest large molecules into smaller ones
break bonds & move electrons from one molecule to another
as electrons move they “carry energy” with them
• They are called oxidation reactions because it reflects the fact that in biological systems oxygen, which attracts electrons strongly, is the most common electron acceptor.
that energy is stored in another bond, released as heat or harvested to make ATP
• Oxidation & reduction reactions always occur together therefore they are referred to as “redox reactions”.
• As electrons move from one atom to another they move farther away from the nucleus of the atom and therefore are at a higher potential energy state.
The reduced form of a molecule has a higher level of energy than the oxidized form of a molecule. • The ability to store energy in molecules by transferring electrons to them is called reducing power, and is a basic property of living systems.
loses e-
gains e-
oxidized
reduced + – + e- e- e-
oxidation
reduction
redox

6. How do we move electrons in biology?
Moving electrons in living systems
electrons cannot move alone in cells
electrons move as part of H atom p e + H –
loses e-
gains e-
oxidized
reduced
oxidation
reduction
Energy is transferred from one molecule to another via redox reactions.
C6H12O6 has been oxidized fully == each of the carbons (C) has been cleaved off and all of the hydrogens (H) have been stripped off & transferred to oxygen (O) — the most electronegative atom in living systems. This converts O2 into H2O as it is reduced.
The reduced form of a molecule has a higher energy state than the oxidized form. The ability of organisms to store energy in molecules by transferring electrons to them is referred to as reducing power. The reduced form of a molecule in a biological system is the molecule which has gained a H atom, hence NAD+  NADH once reduced.
soon we will meet the electron carriers NAD & FADH = when they are reduced they now have energy stored in them that can be used to do work.
C6H12O6
6O2
6CO2
6H2O
ATP  +
oxidation H
reduction e-

7. Oxidation & reduction Oxidation Reduction  adding O removing H
loss of electrons
releases energy
exergonic
Reduction
removing O
adding H
gain of electrons
stores energy
endergonic
C6H12O6
6O2
6CO2
6H2O
ATP  +
oxidation
reduction

9. Moving electrons in respiration
like $$ in the bank
Moving electrons in respiration
Electron carriers move electrons by shuttling H atoms around
NAD+  NADH (reduced)
FAD+2  FADH2 (reduced)
reducing power! P O– O –O C
NH2 N+ H
adenine
ribose sugar
phosphates
NAD+
nicotinamide
Vitamin B3
niacin
NADH P O– O –O C
NH2 N+ H H
How efficient!
Build once, use many ways + H
reduction
Nicotinamide adenine dinucleotide (NAD) — and its relative nicotinamide adenine dinucleotide phosphate (NADP) which you will meet in photosynthesis — are two of the most important coenzymes in the cell.
In cells, most oxidations are accomplished by the removal of hydrogen atoms. Both of these coenzymes play crucial roles in this.
Nicotinamide is also known as Vitamin B3 is believed to cause improvements in energy production due to its role as a precursor of NAD (nicotinamide adenosine dinucleotide), an important molecule involved in energy metabolism. Increasing nicotinamide concentrations increase the available NAD molecules that can take part in energy metabolism, thus increasing the amount of energy available in the cell.
Vitamin B3 can be found in various meats, peanuts, and sunflower seeds. Nicotinamide is the biologically active form of niacin (also known as nicotinic acid).
FAD is built from riboflavin — also known as Vitamin B2. Riboflavin is a water-soluble vitamin that is found naturally in organ meats (liver, kidney, and heart) and certain plants such as almonds, mushrooms, whole grain, soybeans, and green leafy vegetables. FAD is a coenzyme critical for the metabolism of carbohydrates, fats, and proteins into energy.
Enzymes called dehydrogenases remove hydrogen from the substrate and delivers the 2 electrons with one proton to its coenzyme.
oxidation
carries electrons as a reduced molecule

10. Metabolism is tightly controlled
The one-step exergonic reaction of hydrogen with oxygen to form water releases a large amount of energy in the form of heat and light. In cellular respiration, the same reaction occurs in stages. An electron transport chain breaks the fall of electrons in this reaction into a series of smaller steps and stores some of the released energy into a form that can be used to make ATP. The rest of the energy is released as heat.

11. Overview of Cellular Respiration
3 metabolic stages
Anaerobic respiration
1. Glycolysis
respiration without O2
in cytosol
Aerobic respiration
respiration using O2
in mitochondria
2. Krebs cycle
3. Electron transport chain
C6H12O6
6O2
ATP
6H2O
6CO2  +
(+ heat)

12. Step 1: Glycolysis
Glucose (6C) is cleaved into 2 molecules of pyruvate (3C)
Requires 2 ATP but produces 4 ATP
2 NAD+ are reduced to 2 NADH
Presence of oxygen does not affect the process of glycolysis

13. Do not need to know all the steps
Do not need to know all the steps. Uses 2 ATP to phosphorylate sugar derivatives, making it easy to break down the compounds- remember it makes the compounds more stable when you phosphorylate them. Charged molecules are unable to leave the cell.

15. Glycolysis and Evolution
Core process shared by all domains

17. Next Step Anaerobic conditions- Fermentation Aerobic conditions-
Makes 2 ATP
Aerobic conditions-
Citric Acid Cycle aka Kreb’s Cycle

18. Step II: Citric Acid Cycle
Inner membrane of mitochondrion
Pyruvate becomes acetyl CoA
One carbon leaves pyruvate and is released as CO2. Remaining molecule is Acetyl Coenzyme A (oxidized while NAD+ becomes reduced)

19. Energy transferred to FADH2 and NADH are sent on to electron transport chain . Acetyl CoA adds its two carbons to oxaloacetate- making citrate. The next seven steps deal with the decomposition of citrate back to oxaloacetate (regeneration of oxaloacetate that makes it a cycle).

22. Step III: Oxidative Phosphorylation
2 steps
Electron Transport Chain
Transfer of electrons
Proteins embedded in membrane
Last transfer is to oxygen
No ATP
Chemiosmosis
ATP synthase
Embedded proteins alternate between oxidized and reduced states as they accept and donate electrons. Oxygen is the final acceptor in chain. Very electronegative. After picking up an electron, it also picks up a pair of hydrogen ions, forming water
Notice how FADH2 comes in later on in the chain. Thus, it provides less energy that NADH does. About one third. Electron transport chain does not make ATP directly

25. Fermentation Anaerobic respiration Fermentation
Electron transport chain does not use oxygen
Fermentation
Extension of glycolysis
Must recycle NADH back to NAD+
Done by transferring electrons to pyruvate (end product)

26. Two Types of Fermentation
Alcohol Fermentation
Pyruvate converted to ethyl alcohol
CO2 produced
Bacteria and yeast
Lactic acid Fermentation
Pyruvate reduced directly by NADH to form lactic acid
Fungi and bacteria
Cheese
Human muscle cells…