1. Chapter 9.1 Cellular Respiration: Harvesting Chemical Energy
ATP

2. Nutritional Requirements
Animals are heterotrophs
need to take in food
Why? fulfills 3 needs…
fuel = chemical energy for production of ATP
raw materials = carbon source for synthesis
essential nutrients = animals cannot make
elements (N, P, K, Fe, Na, K, Ca...), NAD, FAD, etc.

3. Harvesting stored energy
Energy is stored in organic molecules
heterotrophs eat food (organic molecules)
digest organic molecules
serve as raw materials for building & fuels for energy
controlled release of energy
series of step-by-step enzyme-controlled reactions
“burning” fuels
carbohydrates, lipids, proteins, nucleic acids
We eat to take in the fuels to make ATP which will then be used to help us build biomolecules and grow and move and… live!
heterotrophs = “fed by others”
vs.
autotrophs = “self-feeders”

4. { { { Energy Budget food intake ATP production synthesis storage
basal (resting) metabolism
temperature regulation
activity
food intake
synthesis {
repair
growth
reproduction
storage {
glycogen
fat

5. Harvesting energy stored in glucose
Glucose is the model
catabolism of glucose to produce ATP
glucose + oxygen  carbon + water + energy
dioxide
C6H12O6
6O2
6CO2
6H2O
ATP  +
+ heat
respiration
CO2 + H2O + heat
fuel (carbohydrates)
combustion = making heat energy by burning fuels in one step
Movement of hydrogen atoms from glucose to water
respiration = making ATP (& less heat) by burning fuels in many small steps
ATP
CO2 + H2O + ATP (+ heat)

6. 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
that energy is stored in another bond, released as heat, or harvested to make ATP
loses e-
gains e-
oxidized
reduced
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.
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. + – + + e-
oxidation
reduction e-

7. How do we move electrons in biology?
Moving electrons
in living systems, electrons do not move alone
electrons move as part of H atom
loses e-
gains e-
oxidized
reduced + – + + H
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
reduction H

8. Coupling oxidation & reduction
Redox reactions in respiration
release energy as breakdown molecules
break C-C bonds
strip off electrons from C-H bonds by removing H atoms
C6H12O6  CO2 = fuel has been oxidized
electrons attracted to more electronegative atoms
in biology, the most electronegative atom?
O2  H2O = oxygen has been reduced
release energy to synthesize ATP
 O2
O2 is 2 oxygen atoms both looking for electrons
LIGHT FIRE ==> oxidation
RELEASING ENERGY
But too fast for a biological system
C6H12O6
6O2
6CO2
6H2O
ATP  +
oxidation
reduction

9. 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

10. Moving electrons in respiration
Electron carriers move electrons (and energy) by shuttling H atoms around
NAD+  NADH (reduced)
FAD+2  FADH2 (reduced)
now has
reducing power!
Make sure you get this!!!
NAD+
nicotinamide
adenine
dinucleotide
(vitamin B3) P O– O –O C
NH2 N+ H
NADH P O– O –O C
NH2 N+ H
adenine
ribose
sugar
phosphates
reduction
oxidation + H
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.
when NADH
is oxidized
back to NAD:
DG = -219kJ/mol

11. Overview of cellular respiration
4 metabolic stages
Anaerobic respiration
1. Glycolysis
respiration without O2
in cytosol
Aerobic respiration
respiration using O2
in mitochondria
2. Pyruvate oxidation
3. Kreb’s cycle
4. Electron transport chain
These involve
those redox reactions!
C6H12O6
6O2
6CO2
6H2O
ATP  +
(+ heat)

12. What’s the point?
ATP
The Point is to Make ATP!
Any Questions??