1. Energy metabolism, enzyme and Cofactors

2. Forms of Energy These forms of energy are important to life: chemical
radiant (examples: heat, light)
mechanical
electrical
Energy can be transformed from one form to another.
Chemical energy is the energy contained in the chemical bonds of molecules.
Radiant energy travels in waves and is sometimes called electromagnetic energy. An example is visible light.
Photosynthesis converts light energy to chemical energy.
Energy that is stored is called potential energy.

3. Laws of Thermodynamics
1st law: Energy cannot be created or destroyed.
Energy can be converted from one form to another. The sum of the energy before the conversion is equal to the sum of the energy after the conversion.
Example: A light bulb converts electrical energy to light energy and heat energy. Fluorescent bulbs produce more light energy than incandescent bulbs because they produce less heat.
2nd law: Some usable energy dissipates during transformations and is lost.
During changes from one form of energy to another, some usable energy dissipates, usually as heat. The amount of usable energy therefore decreases.

4. Energy is required to form bonds.
Atoms or molecules
Energy
+ Energy
Larger molecule
The energy that was used to form the bonds is now stored in this molecule. 8

5. Energy is released when bonds are broken.
The energy is now released. It may be in a form such as heat or light or it may be transferred to another molecule.
Energy 8
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6. ATP (Adenosine Triphosphate)CH N C
NH2 HC O
O P O P O P O CH2
O O O
O O O- -
H H
OH OH H
3 phosphate groups
Base (adenine)
Ribose

7. ATP (Simplified Drawing)
3 phosphate groups
Base (adenine) A
Sugar (ribose) 11

8. ATP Stores Energy Energy ADP + Pi + Energy ATP
Breaking the bonds releases the energy.
The phosphate bonds are high-energy bonds. A
ATP

9. ATP is Recycled ATP Energy Energy ADP + Pi
ATP (Adenosine Triphosphate) is an energy-rich molecule used to supply the cell with energy. The energy used to produce ATP comes from glucose or other high-energy compounds.
ATP is continuously produced and consumed as illustrated below.
ADP + Pi + Energy  ATP + H2O
(Note: Pi = phosphate group)
ATP
Energy
Energy
(from glucose or other high-energy compounds)
ADP + Pi 13

10. Menu Energy ATP Energy release ADP + Pi ATP Energy absorbed Energy ADP8
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11. Catabolic and Anabolic Reactions
the breakdown of complex organic compounds to simpler compounds generally release energy and are called catabolic reactions.
Anabolic reactions are those that consume energy while synthesizing compounds.
ATP produced by catabolic reactions provides the energy for anabolic reactions. Anabolic and catabolic reactions are therefore coupled (they work together) through the use of ATP.

12. Menu An anabolic reaction A catabolic reaction ATP ADP + Pi Energy
e.g. Body building – protein synthesis
A catabolic reaction
e.g. breakdown of sugar
ATP
ADP + Pi
Energy 8
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13. Substrates (Reactants)
Anabolic Reactions
Products
Energy Supplied
Anabolic reactions consume energy.
Substrates (Reactants)
Energy Released 9
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14. Catabolic reactions release energy
Energy Supplied
Substrate (Reactants)
Catabolic reactions release energy
Energy Released
When bonds are broken, energy is released. 10
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15. Energy Supplied Activation Energy Energy Released Menu
In either kind of reaction, additional energy must be supplied to start the reaction. This energy is called activation energy.
Energy Supplied
Activation Energy
Energy Released 21
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16. Energy Supplied Activation Energy Energy Released Menu
An example of activation energy is the “spark” needed to ignite gasoline.
Energy Supplied
Activation Energy
Energy Released 21
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17. Activation energy without enzyme Energy Supplied
Enzymes lower the amount of activation energy needed for a reaction.
Activation energy without enzyme
Energy Supplied
Activation energy
with enzyme
Energy Released 22
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18. Energy is transferred with electrons
This atom served as an energy carrier. It picked up an electron from the atom on the left and gave it to the one on the right.
Oxidized atom
Electron is donated
Energy is donated
Reduced atom
Electron is received
Energy is received
Oxidized atom
Electron is donated
Energy is donated
Reduced atom
Electron is received
Energy is received 49

19. Oxidation and Reduction
Oxidation is the loss of electrons or hydrogen atoms.  Oxidation reactions release energy.
Reduction is gain of electrons or hydrogen atoms and is associated with a gain of energy.
Oxidation and reduction occur together. When a molecule is oxidized, another must be reduced.
These coupled reactions are called oxidation-reduction or redox reactions.
Food is highly reduced (has many hydrogens). The chemical pathways in cells that produce energy for the cell oxidize the food (remove hydrogens), producing ATP.

20. Cofactors
Many enzymes require a cofactor to assist in the reaction.  These "assistants" are non-protein and may be metal ions such as magnesium (Mg++), potassium (K+), and calcium (Ca++). 
The cofactors bind to the enzyme and participate in the reaction by removing electrons, protons , or chemical groups from the substrate.

21. Coenzymes Cofactors that are organic molecules are coenzymes.
In oxidation-reduction reactions, coenzymes often remove electrons from the substrate and pass them to different enzymes.
In this way, coenzymes serve to carry energy in the form of electrons (or hydrogen atoms) from one compound to another.

22. Coenzymes
Enzyme
Coenzyme
Enzyme
Coenzymes are organic cofactors that are not protein.
They bind to the enzyme and also participate in the reaction by carrying electrons or hydrogen atoms.

23. Vitamins are Coenzymes
Vitamin Coenzyme Name
B3 (Niacin) NAD+
B2 (riboflavin) FAD
B1 (thiamine) Thiamine pyrophosphate
B5 (Pantothenic acid) Coenzyme A (CoA)
B12 Cobamide coenzymes 46

24. Electron Carriers
Some coenzymes are electron carriers function in photosynthesis and cellular respiration. Three major electron carriers are listed below.
Respiration
NAD+
FAD
Photosynthesis
NADP+ 52

25. NAD+

26. NAD+ (Nicotinamide Adenine Dinucleotide)
Organic Molecule
NAD+
NAD+ + +
Oxidized
Organic Molecule
NAD+ + 2H  NADH + H+
NAD+ functions in cellular respiration by carrying two electrons. With two electrons, it becomes NADH.
NAD+ oxidizes its substrate by removing two hydrogen atoms. One of the hydrogen atoms bonds to the NAD+. The electron from the other hydrogen atom remains with the NADH molecule but the proton (H+) is released. 
NAD+ + 2H  NADH + H+
NADH can donate two electrons (one of them is a hydrogen atom) to another molecule.
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27. NAD+ + 2H  NADH + H+
NADH + H+
Energy + 2H
Energy + 2H
NAD+ 53

28. NADP+ + 2H  NADPH + H+
NADPH + H+
Energy + 2H
Energy + 2H
NADP+ 53

29. NADP+ (Nicotinamide Adenine Dinucleotide Phosphate)
NADP+ + 2H  NADPH + H+
NADP+ is similar to NAD+ in that it can carry two electrons, one of them in a hydrogen atom, the other one comes from a hydrogen that is released as a hydrogen ion. (Click here to review NAD+.)
Electrons carried by NADPH in photosynthesis are ultimately used to reduce CO2 to carbohydrate.

30. Phosphorylation
ATP is synthesized from ADP + Pi. The process of synthesizing ATP is called phosphorylation.
Two kinds of phosphorylation are illustrated on the next several slides.
Substrate-Level Phosphorylation
Chemiosmotic Phosphorylation

31. Substrate-Level Phosphorylation
A high-energy molecule (substrate) is used to transfer a phosphate group (Pi) to ADP to form ATP. Pi Pi Pi
High-energy molecule
ADP
Pi - inorganic phosphate

32. Substrate-Level Phosphorylation
A high-energy molecule (substrate) is used to transfer a phosphate group to ADP to form ATP. Pi Pi Pi
High-energy molecule
ADP
This bond will be broken, releasing energy.

33. Substrate-Level Phosphorylation
A high-energy molecule (substrate) is used to transfer a phosphate group to ADP to form ATP. Pi Pi Pi
High-energy molecule
ADP
The energy released will be used to bond the phosphate group to ADP, forming ATP.

34. Substrate-Level Phosphorylation
A high-energy molecule (substrate) is used to transfer a phosphate group to ADP to form ATP. Pi Pi Pi
High-energy molecule
ADP
Enzyme
An enzyme is needed.

35. Substrate-Level PhosphorylationPi Pi Pi
Enzyme

36. Substrate-Level Phosphorylation
The energy has been transferred from the high-energy molecule to ADP to produce ATP. Pi Pi Pi
Low-energy molecule
ATP

37. Mitochondrion Structure
This drawing shows a mitochondrion cut lengthwise to reveal its internal membrane.
Intermembrane Space
Cristae Matrix

38. Chemiosmotic Phosphorylation
This drawing shows a close-up of a section of a mitochondrion.
Chemiosmotic Phosphorylation H+ H+
Matrix (inside) H+ H+
Outside
Intermembrane Space
Matrix H+ H+ H+ H+ H+ H+ H+ H+ H+ 33
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39. Pumps within the membrane moves hydrogen ions from the matrix to the intermembrane space creating a concentration gradient. 00 H+ H+
Matrix (inside) H+ H+
Outside
Intermembrane Space
Matrix H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 33
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40. Menu This process requires energy -- cellular respiration. H+ H+ H+
Matrix (inside) H+ H+
Outside
Intermembrane Space
Matrix H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 33
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41. Chemiosmotic Phosphorylation
A high concentration of hydrogen ions in the intermembrane space creates a gradient for diffusion of H+ back to the matrix.
Chemiosmotic Phosphorylation H+
Matrix (inside) H+ H+
Outside
Intermembrane Space
Matrix H+ H+ H+ H+ H+ H+ H+ H+ H+ 33
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42. Chemiosmotic Phosphorylation
the hydrogen ions pass through this protein (called ATP synthase) as they return to the matrix down the diffusion gradient.
Chemiosmotic Phosphorylation H+ H+
Matrix (inside) H+ H+
Outside
Intermembrane Space
Matrix H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ 33
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43. Chemiosmotic Phosphorylation
Matrix (inside) H+ H+
Outside
Intermembrane Space H+ H+ H+
ADP + Pi H+ H+ H+
ATP H+ H+
ATP synthase produces ATP by phosphorylating ADP. The energy needed to produce ATP comes from hydrogen ions forcing their way into the matrix as they pass through the ATP synthase. H+ H+ 33
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44. Chemiosmotic Phosphorylation
Chemiosmotic phosphorylation is used by the mitochondrion to produce ATP. The energy needed to initially pump H+ ions into the intermembrane space comes from glucose. The entire process is called cellular respiration.
The chloroplast also produces ATP by chemiosmotic phosphorylation. The energy needed to produce ATP comes from sunlight.

45. Chloroplast Structure
The chloroplast is surrounded by a double membrane.
Molecules that absorb light energy (photosynthetic pigments) are located on disk-shaped structures called thylakoids.
The interior portion is the stroma.
Double membrane
Stroma
Thylakoids

46. A Thylakoid H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
In order to synthesize ATP, hydrogen ions must first be pumped into the thylakoid. This process requires energy. H+ 72

47. A Thylakoid H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
A concentration gradient of hydrogen ions is established. The chemical gradient can be used as an energy source for producing ATP. H+ 72

48. Chemiosmotic Phosphorylation
hydrogen ions force through this protein (ATP synthase) as they return to the stroma. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
ADP + Pi
ATP H+ H+
ATP synthase produces ATP by phosphorylating ADP. The energy comes from hydrogen ions forcing their way into the stroma as they pass through the ATP synthase H+ H+ 72

49. Phosphorylation
We have just discussed two different forms of phosphorylation:
Substrate-level phosphorylation
Chemiosmotic phosphorylation
We saw that chemiosmotic phosphorylation occurred in both the mitochondria (during cellular respiration) and in the chloroplast (during photosynthesis). These two processes are sometimes given separate names:
Oxidative phosphorylation (in mitochondria)
Photophosphorylation (in chloroplast)

50. Chemiosmosis: Chloroplasts vs. Mitochondria
Similarities: In both organelles
Redox reactions of electron transport chains generate a H+ gradient across a membrane
Involves ATP synthase which uses this proton-motive force to make ATP
Difference:
use different sources of energy to accomplish this (proton gradient). Chloroplasts use light energy (photophosphorylation) and mitochondria use the chemical energy in organic molecules (oxidative phosphorylation).

51. The End