1. Energy and Metabolism
Chapter 6

2. Section 6.1 Learning Objectives
The Flow of Energy in Living Systems
Differentiate between kinetic and potential energy.
Identify the source of energy for the biosphere (Earth).
Contrast oxidation and reduction reactions.

3. Flow of Energy Thermodynamics
Branch of chemistry concerned with energy changes
Study of energy flow or transformations
Kinetic energy  potential energy
Potential energy  kinetic energy
Cells are governed by the laws of physics and chemistry

4. What is Energy? Energy – capacity to do work 2 states
Kinetic – energy of motion
Potential – stored energy
Many forms – mechanical, heat, sound, electric current, light, or radioactivity
Heat the most convenient way of measuring energy
1 calorie = heat required to raise 1 gram of water 1ºC
calorie or Calorie?
Calorie (1000 calories) how food energy measured

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a. Potential energy
b. Kinetic energy
Stored energy based on her position (also think of a bolder on top of a hill)
Energy in motion (she is able to slide down based on her previous position)

6. The Source of Energy on Earth
Energy flows into the biological world from the sun
Photosynthetic organisms (plants/algae) capture this energy
Stored as potential energy in chemical bonds (in sugars made from photosynthesis)
cell respiration
photosynthesis

7. Redox reactions (how energy is transferred at molecular level)
Oxidation
Atom or molecule loses an electron
Reduction
Atom or molecule gains an electron
Higher level of energy than oxidized form
Oxidation-reduction reactions (redox)
Reactions always paired
LEO says GER (leo is a lion)
Loss of e- is oxidation
Gain of e- is reduction

8. To follow the energy, follow the e-
Loss of electron (oxidation) LEO e- e – A B A + B A + + B –
Gain of electron (reduction) GER
Lower energy
Higher energy

9. Question Oxidation is the ____________ and reduction is the ________.
loss of electrons, gain of electrons
gain of protons, loss of protons
loss of protons, gain of protons
loss of electrons, gain of protons
Bloom’s level: Knowledge/Understanding

10. Section 6.2 Learning Objectives
The Laws of Thermodynamics and Free Energy
Explain the laws of thermodynamics.
Relate free energy changes to the outcome of chemical reactions.
Contrast the course of a reaction with and without an enzyme catalyst.

11. Laws of thermodynamics
First law of thermodynamics
Energy cannot be created or destroyed
Energy can only change from one form to another
Total amount of energy in the universe remains constant
During each conversion, some energy is lost as heat

12. Second law of thermodynamics
Entropy (disorder) is continuously increasing
Energy transformations proceed spontaneously to convert matter from a more ordered/less stable form to a less ordered/ more stable form

13. Disorder happens spontaneously
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Disorder happens spontaneously
Organization requires energy
© Jill Braaten

14. Free energy G = Energy available to do work G = H – TS
H = enthalpy, energy in a molecule’s chemical bonds
T = absolute temperature
S = entropy, unavailable energy G

15. ΔG = ΔH – TS ΔG = change in free energy Positive ΔG Negative ΔG
Products have more free energy than reactants
Not spontaneous, requires input of energy
Endergonic (photosynthesis)
Negative ΔG
Products have less free energy than reactants
Spontaneous (may not be instantaneous)
Exergonic (cell respiration)

16. Energy Released Energy Supplied Energy Released Energy Supplied
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Endergonic
Products
Energy must
be supplied
Energy Released Energy Supplied
Free Energy (G)
 G > 0
Reactants
photosynthesis
Course of Reaction a.
Exergonic
cell respiration
Reactants
Energy Released Energy Supplied
Free Energy (G)
Energy is
released
Products
 G < 0
Course of Reaction b.

17. Activation Energy: How to Start a Reaction
Extra energy required to destabilize existing bonds and initiate a chemical reaction
Exergonic reaction’s rate depends on the activation energy required
Larger activation energy proceeds more slowly
Rate can be increased 2 ways
Increasing energy of reacting molecules (heating)
Lowering activation energy

18. Energy Released Energy Supplied
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uncatalyzed
catalyzed
Activation
energy
Activation
energy
Energy Released Energy Supplied
Free Energy (G)
Reactant ΔG
Product
Course of Reaction

19. Catalysts
Substances that influence chemical bonds in a way that lowers activation energy
Cannot violate laws of thermodynamics
Cannot make an endergonic reaction spontaneous
Do not alter the proportion of reactant turned into product

20. Energy Released Energy Supplied
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uncatalyzed
catalyzed
Activation
energy
Activation
energy
Energy Released Energy Supplied
Free Energy (G)
Reactant ΔG
Product
Course of Reaction

21. Question The energy in a system that is able to do work is called
Enthalpy
Entropy
Free energy
Kinetic energy
Potential energy
Bloom’s level: Knowledge/Understanding

22. Question A reaction with a positive ∆G is – Exergonic Entropic
Endergonic
Enthalpic
Energertic
Bloom’s level: Knowledge/Understanding

23. Question
A ball sitting atop a hill begins to roll down after getting a slight tap. This is analogous to an endergonic reaction.
This is true
This is false
Bloom’s level: Application. This is exergonic. Ask how to make it endergonic

24. Section 6.3-6.4 Learning Objectives
ATP: The Energy Currency of Cells
Describe the role of ATP in short-term energy storage.
Distinguish which bonds in ATP are “high energy.”
Enzymes: Biological Catalysts
Discuss the specificity of enzymes.
Explain how enzymes bind to their substrates.
List the factors that influence the rate of enzyme-catalyzed reactions.

25. ATP: Cell Energy Adenosine triphosphate Chief “currency” all cells use
Composed of
Ribose – 5 carbon sugar
Adenine
Chain of 3 phosphates
Key to energy storage
Bonds are unstable
ADP – 2 phosphates
AMP – 1 phosphate – lowest energy form

26. a. b. ATP Triphosphate group O– O P O– O ADP High-energy bonds O P O–
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ATP
Triphosphate
group O– a. O P O– O
ADP
High-energy
bonds O P O–
Adenine
NH2 N C O C N H C C C H N N
AMP CORE O P O O
CH2 O H H H H OH OH
Ribose b.

27. ATP cycle ATP hydrolysis drives endergonic reactions
Coupled reaction results in net –ΔG (exergonic and spontaneous)
ATP not suitable for long-term energy storage
Fats and carbohydrates better
Cells store only a few seconds worth of ATP

28. photosynthesis cell respiration
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H2O
ATP
Energy from
exergonic
cellular
reactions
Energy for
endergonic
cellular
processes
photosynthesis +
cell respiration
ADP Pi

29. Enzymes: Biological Catalysts
Most enzymes are protein
Some are RNA
Shape of enzyme stabilizes a temporary association between substrates
Enzyme not changed or consumed in reaction
Carbonic anhydrase (enzyme used to maintain blood pH)
200 molecules of carbonic acid per hour made without enzyme
600,000 molecules formed per second with enzyme

30. a. b. Active site Substrate Enzyme Enzyme–substrate complex
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Active site
Substrate
Enzyme
Enzyme–substrate complex a. b.

31. Active site Pockets or clefts for substrate binding
Forms enzyme–substrate complex
Precise fit of substrate into active site
Applies stress to distort particular bond to lower activation energy
Induced fit

32. consists of glucose and fructose bonded together.
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1. The substrate, sucrose,
consists of glucose and
fructose bonded together.
3. The binding of the substrate and enzyme places stress on the glucose– fructose bond, and the bond breaks.
2. The substrate binds to the active site
of the enzyme, forming an enzyme–
substrate complex.
Glucose
Bond
Fructose
H2O
4. Products are
released, and
the enzyme is
free to bind other
substrates.
Active site
Enzyme
sucrase

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34. Nonprotein enzymes Ribozymes
1981 discovery that certain reactions catalyzed in cells by RNA molecule itself
2 kinds
Intramolecular catalysis – catalyze reaction on RNA molecule itself
Intermolecular catalysis – RNA acts on another molecule

35. Enzyme function Small molecules can affect function
Coenzymes
Cofactors
Rate of enzyme-catalyzed reaction depends on concentrations of substrate and enzyme
Any chemical or physical condition that affects the enzyme’s three-dimensional shape can change rate

36. Optimum temperature for enzyme from hotsprings prokaryote
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Optimum temperature
for human enzyme
Optimum temperature for enzyme
from hotsprings prokaryote
Rate of Reaction 30 40 50 60 70 80
Temperature of Reaction (˚C) a.
Optimum pH for pepsin
Optimum pH for trypsin
Rate of Reaction 1 2 3 4 5 6 7 8 9
pH of Reaction b.

37. Inhibitors
Inhibitor – substance that binds to enzyme and decreases its activity
Competitive inhibitor
Competes with substrate for active site
Noncompetitive inhibitor
Binds to enzyme at a site other than active site
Causes shape change that makes enzyme unable to bind substrate

38. Competitive inhibitor interferes with active site of enzyme so
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Substrate
Substrate
Inhibitor
Inhibitor
Active
site
Active
site
Enzyme
Enzyme
Allosteric site
Competitive inhibitor interferes
with active site of enzyme so
substrate cannot bind
Allosteric inhibitor changes shape of enzyme so it cannot bind to substrate
a. Competitive inhibition
b. Noncompetitive inhibition

39. Allosteric Enzymes
Allosteric enzymes – enzymes exist in active and inactive forms
Most noncompetitive inhibitors bind to allosteric site – chemical on/off switch
Allosteric inhibitor – binds to allosteric site and reduces enzyme activity
Allosteric activator – binds to allosteric site and increases enzyme activity

40. Question
If inhibition is to be competitive, which of the following must be true?
There must be more than one binding site
The substrate and the inhibitor must be similar
The reaction can not require a cofactor
The reaction must be endergonic
The allosteric and active sites must be near each other
Bloom’s level: Application. Thnk in competitive, they bind the same actie site

41. Question
Carbon monoxide (CO) binds to the hemoglobin protein at the oxygen binding site. Once the CO binds, the oxygen can no longer be transported. What does this describe?
Non-competitive inhibition
Feedback inhibition
Substrate inhibition
Allosteric inhibition
Competitive inhibition
Bloom’s level: Application

42. Question
Increasing the temperature increases the rate of an enzyme-catalyzed reaction. Once a critical temperature is reached, the reaction stops. Why does this happen?
The concentration of reactants drop
The enzymes have all been consumed in the reaction
The increase in temperature alters the pH
The polypeptide chains in the enzyme denature
Bloom’s level: Application

43. Section 6.5 Learning Objectives
Metabolism: The Chemical Description of Cell Function
Explain the kinds of reactions that make up metabolism.
Discuss what is meant by a metabolic pathway.
Describe mechanisms to control a metabolic pathway

44. Metabolism Catabolism Metabolism Anabolism
Total of all chemical reactions carried out by an organism
Anabolic reactions/anabolism
Expend energy to build up molecules
Anabolic Steroids=build muscle
Catabolic reactions/catabolism
Harvest energy by breaking down molecules
Starvation=breakdown muscle
Catabolism
Anabolism
Metabolism
Large molecules
Small molecules

45. Biochemical pathways
Chemical reactions that create/store or produce other chemical products for daily function.
Reactions occur in a sequence
Product of one reaction is the substrate for the next reaction A
Enzyme 1 B
Enzyme 2 C
Enzyme 3 D

46. Basic metabolic pathway chart

47. Initial substrate Enzyme1 Intermediate substrate A Enzyme2
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Initial substrate
Enzyme1
Intermediate
substrate A
Enzyme2
Intermediate
substrate B
Enzyme3
Intermediate
substrate C
Enzyme4
End product

48. Feedback inhibition
End-product of pathway binds to an allosteric site on enzyme that catalyzes first reaction in pathway
Shuts down pathway so raw materials and energy are not wasted
Feedback inhibition

49. a. b. Initial substrate Initial substrate Enzyme 1 Enzyme 1
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Initial
substrate
Initial
substrate
Enzyme 1
Enzyme 1
Intermediate
substrate A
Enzyme 2
Enzyme 2
Intermediate
substrate B
Enzyme 3
End product
Enzyme 3
End product a. b.

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51. Question
Feedback inhibition occurs when the final product acts as an inhibitor to the first enzyme in the pathway.
This is true
This is false
Bloom’s level: Knowledge/Understanding

52. Question
Catabolic reactions expend energy to form or transform chemical bonds.
This is true
This is false
Bloom’s level: Knowledge/Understanding.

53. Final Review

54. Question The First Law of Thermodynamics states that energy can be –
Created
Destroyed
Converted
Lost
None of the above
Bloom’s level: Knowledge/Understanding

55. Question
Small organic molecules that assist in enzymatic functions are –
Coprolites
Cofactors
Activators
Coenzymes
Intermediates
Bloom’s level: Knowledge/Understanding

56. Question
Spending ATP involves hydrolyzing it into ADP and inorganic P. The energy released can drive other chemical reactions.
This is true
This is false
Bloom’s level: Knowledge/Understanding

57. Question Enzymes are consumed by reactions. This is true This is false
Bloom’s level: Knowledge/Understanding

58. Question
A catalyst speeds up chemical reactions. How do catalysts do this?
Decreasing entropy
Altering ∆G
Consuming reactants
Lowering activation energy
Making different products
Bloom’s level: Application

59. Question
A muscle contraction is ________, but as the muscle contracts heat is released which is ___________.
Exergonic, endergonic
Exergonic, exergonic
Endergonic, endergonic
Endergonic, exergonic
Bloom’s level: Application

60. Question
Study this metabolic pathway: A -E1  B -E2  C -E3  D. Which of the following statements is NOT correct? (E represents enzymes)
C is the substrate for enzyme E1 and D is the product
A is the substrate for enzyme E1 and B is the product
Enzyme E2 can catalyze the substrate B but not A, C and D
B is the product formed by enzyme E1 but the substrate for enzyme E2
Bloom’s level: Application

61. Question
When muscles contract, chemical energy is converted to mechanical energy with the loss of heat. This conversion of energy is an example of the ______ Law of Thermodynamics.
First
Second
Third
Fourth
Bloom’s level: Application

62. Question
Which of the following is defined as the amount of heat required to raise one gram of water one degree Celsius?
Tesla
Joule
Newton
Calorie
calorie
Bloom’s level: Knowledge/Understanding