1. Chapter 6: Energy & Metabolism
Section 1
Energy and Living Things
Biology: Principles and Explorations---sea turtle book!

2. Organisms need energy to carry out many task vital to life:
Every Cell—is driven by energy
Growth
Reproduction
Movement
Photosynthesis
transport of molecules and ions across the cell membranes

3. The Flow of Energy in Living Things
Energy: is defined as the capacity to do work
Can be found in 2 STATES: (most basic)
1. Kinetic Energy: energy of motion
(kicking a football)
2. Potential Energy: stored energy
(a rock sitting on top of a hill)
Much of the work that living organisms carryout involves transforming potential energy to kinetic energy.

4. A bolder perched on a hilltop has SOME potential energy; as it begins to roll downhill, some potential energy is converted to kinetic energy

5. Forms of Energy 7 Forms of Energy 1. Mechanical or Chemical
Energy can take many forms:
7 Forms of Energy
1. Mechanical or Chemical
2. Radioactive Radiation
3. Solar/Light
4. Nuclear
5. Electrical
6. Heat
7. Sound
Because it can exist in many forms, there are many ways to measure it
There are so many different ways that mater can move and change, energy appears to exist in many different forms

6. The most convenient term
Energy can be transformed (changed from one form to another)
The most convenient is in terms of heat because all other forms of energy can be converted into heat
Example: an electrical fan converts electric energy to mechanical energy
Example: as gas burns in a car’s engine, chemical energy is converted to mechanical energy and heat

7. Universal Laws
All energy conversions are governed by the laws of Thermodynamics
The study of energy transformations
Two Universal Laws
1. First Law of Thermodynamics
2. Second Law of Thermodynamics

8. First Law of Thermodynamics
Energy cannot be created nor destroyed; it can only change from one form to another.
From potential to kinetic and vice-versa
The total amount of energy in the universe remains constant.
Most of the work done by living things involves energy transformations
-food as a source of energy for movement
-food to help maintain body temperature

9. Example
The lion eating the giraffe is acquiring energy by transferring some of the potential energy stored in the giraffe’s tissues to its own body

10. Second Law of Thermodynamics
States the disorder (entropy) in the universe is continuously increasing.
In simple terms: Disorder is more likely than order.
As energy is used, more and more of it is converted to heat, the energy of random molecular motion.
Ex: it is more likely that a column of bricks will tumble over than a pile of bricks

11. Entropy
Is the measure of the disorder of a system, so the Second Law of Thermodynamics can also be stated simply as “entropy increases”

12. Organization requires energy. It takes effort to keep this room clean.

13. Energy flows through living systems
All organisms need a constant supply of energy to fuel the activities of life
Photosynthesis: process of converting light energy to chemical energy
Chemosynthesis: process of converting inorganic molecules to organic chemical energy (certain bacteria)

14. Energy flows through living systems
Autotrophs: organisms that harvest energy from either sunlight or chemicals (aka: producers) means “self” “feed”
Heterotrophs: organisms that cannot harvest energy directly from sunlight or inorganic molecules but must consume food (aka: consumers) means “other” “to feed”
Cellular Respiration: a series of chemical reactions that converts energy stored in food to a more useful form. Mostly in ATP which fuels activities of life.

15. Autotrophs & Heterotrophs examples
Autotrophs: Producers
Heterotrophs: Consumers

16. Energy is Carried by Electrons
Energy can be extracted from chemical bonds in food you eat
Energy in food is actually stored in the shared electrons of carbon-to-hydrogen bonds
These electrons are portable & can be transferred to new chemical bonds by Oxidation-Reduction Reactions

17. The chemical reaction…
Chemical reactions that pass electrons from one atom or molecule to another are Oxidation-Reduction Reactions

18. Oxidation-Reduction Oxidation: is the loss of electrons
Reduction: is the gain of electrons
In organisms, electrons usually are NOT TRANSFERRED Alone
Each electron moves with a proton as part of a hydrogen atom, H
The transfer of energy in organisms usually involves the REMOVAL of H atoms from one molecule and the ADDITION of H atoms to another molecule

19. Key Roles
Oxidation-reduction reactions play key roles in organisms because they enable energy (carried by hydrogen atoms) to pass from one molecule to another
Plays a key role in the flow of energy through a biological system because of the electrons that pass from one atom to another carrying energy with them

20. C6H12O6 + 6O2  6CO2 + 6 H20 C6H12O6 is oxidized when it loses H atoms
O2 is reduced when it gains H atoms
Oxidation-Reduction always take place together because every electron that is lost by one atom or molecule is gained by another
C6H12O6 + 6O2  6CO2 + 6 H20

21. Cofactors Redox reactions often require cofactors
The enzymes that harvest H atoms have a binding site for NAD+ located near another binding site.
NAD+ & an energy-rich molecule bind to the enzyme.
In a redox reaction, a H atom is transferred to NAD+ , making NADH
NADH then diffuses away and is available to other molecules

22. Oxidation-Reaction Cofactors:electron carriers
Energy-rich molecule
Enzyme H H
NAD+ H
Product
NAD+
NAD+
NAD H
1. Enzymes that harvest
hydrogen atoms have a
binding site for NAD+
located near another
binding site. NAD+ and
an energy-rich
molecule bind to
the enzyme.
2. In an oxidation-
reduction reaction,
a hydrogen atom
is transferred to
NAD+, forming
NADH.
NAD H
3. NADH then
diffuses away and
is available to
other molecules.

23. Energy and Chemical Reactions

24. Chemical reactions absorb or release energy
A chemical reactions happens when chemical bonds between atoms are broken or formed
The substances that are combined or broken apart are called reactants
The new substances that are formed are called products
2H2 + O2  2H2O
Reactant  Product

25. Free Energy
The energy from chemical reactions that drives cell activities is called free energy
While most biochemical reactions release free energy into their surroundings, others absorb it.

26. 2 kinds of Reactions
1. Exergonic Reaction: a reaction that releases free energy
Product has higher energy level than reactant
Cellular Respiration is an Exergonic process
2. Endergonic Reaction: a reaction that absorbs free energy
Product has lower energy level than reactant
Photosynthesis is an Endergonic process

27. Activation Energy (kick in the pants)
Not all chemical reactions occur spontaneously because most reactions require an input of energy to start
The extra energy required to break existing chemical bonds to initiate a chemical reaction is called activation energy
The rate of the reaction depends on the activation energy necessary to initiate it. Catalysts reduce the activation energy and increase the rate of reaction but do not change the final proportions of reactants and products
The heat from a match supplies the sizeable amount of activation energy that is needed to start a chemical reaction by transferring free energy to the reactant. This extra energy causes the reactant particles to move and vibrate faster---because they have more kinetic energy. If the kinetic energy of reactant particles is the same as the required activation energy, it can be used to break chemical bonds in the reactants so that new bonds and products can form.

28. Fig. 8.7 ACTIVATION ENERGY Uncatalyzed Energy supplied Activation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 8.7
ACTIVATION ENERGY
Uncatalyzed
Energy supplied
Activation
energy
Catalyzed
Activation
energy
Reactant
Reactant
Energy released
Product
Product

29. Fig. 8.6 FREE ENERGY Product Energy supplied Free Energy Absorbed
Reactant
Reactant
Free
Energy
Released
Energy released
Product
Giving their products
More total energy than
Their reactant
Leaves product with less
Total energy than their reactant
Endergonic
Exergonic

30. Catalysts
A chemical reaction (exergonic or endergonic) will proceed at a faster rate than normal if the activation energy can be lowered.
A substance that alters a chemical reaction so it can proceed at a lower activation energy is a catalyst

31. Catalyst “do’s & don'ts
1. Substances that act as catalysts are not changed by the reactions they assist
2. Catalysts do not make chemical reactions begin spontaneous
3. They do not reduce the activation energy to zero
4. The need for activation energy cannot be avoided
Each reaction waits for the “nudge” that will give it enough activation energy to start

32. Enzyme Catalyze Cells need catalysts to help start chemical reactions
Cells control chemical reactions by controlling the activity of these catalysts
Enzymes are the catalysts used by cells to trigger and control particular chemical reactions
By molecular standards, enzymes are enormous.
Can be used over and over. This is called regenerated
Thousands of different kinds of enzymes are known, each catalyzing one or a few specific chemical reactions. By controlling particular reactions, the enzymes determine the course of metabolism in that cell. Different types of cells contain different sets of enzymes which contributes to structure & functional variations among cell types. Example: chemical reactions in a red blood cell are different than the ones in a nerve cell because the cytoplasm and membranes contain different enzymes.

33. Enzyme Nomenclature Most enzymes end in -ase
The rest of the name is usually derived from the substrate.
Example: If protein is the substrate, then
protease would be the enzyme
catalyzing the reaction.

34. Enzyme Examples
The stomach combines with the enzyme Pepsin with acids to speed up the digestion of processes
Engineers use the power of enzymes to clean up polluted soils & streams.
They make bioreactors (enzyme chemicals) which digest the chemical by the enzyme

35. Examples Protease is an enzyme that digest proteins
A lack of protease can result in low blood sugar, kidney problems & bone problems
Lipase is an enzyme that digest fats
If there is not enough lipase in the body, health problems can result such as obesity, diabetes, and heart & blood vessel disease
Amylase is an enzyme that changes starch into glucose: starch is the substrate
Starch Synthetase: is the reverse of Amylase; glucose is the substrate

36. Substrates
The enzyme is a protein that works by binding to a specific reactant molecule
The reactant molecule that an enzyme binds to is called a substrate
Enzymes are specific for substrates

38. The active site of an enzyme
It is the groove in the enzyme that fits the shape of a particular substrate
Most enzymes are globular proteins with one or more pockets on their surface called active sites
Substrates bind at these sites
For catalysis to occur, molecules must fit precisely into an active site

39. Active site: a pocket through which only 1 or 2 substrates can fit.

40. Fig. 8.8 (TEArt)
Active site
Substrate

41. One way that enzymes lower activation energy is by weakening chemical bonds so that they will break more easily
EX: Amylase speeds the breakdown of starch into glucose by weakening the bonds linking glucose subunits

42. Induced Fit
Sometimes when an enzymes active site is not exactly complementary to the shape of the substrate.
After binding to the substrate, the active site changes its shape to achieve a better fit around the substrate.
This is called Induced Fit
Proteins are not rigid to fit

44. Factors Affecting Enzymes
Factors that change the shape of an enzyme affect the enzymes activity
Temperature pH
For each enzyme, there is a range of temperature and pH where it operates efficiently.
Outside this range cause some of the H-bonds that determine enzyme’s shape to be broken or change the shape of the enzyme

45. 1. Temperature
The rate of an enzyme increases with temperature, but only up to a point (Optimum Temperature)
Below this point-not flexible enough to permit induced fit
Optimal temperature for humans= 37o to 40oC
Optimal temperature for prokaryotes found in hot springs 70oC

46. 2. pH Enzymes are specific for a pH
Different enzymes prefer different pH’s
Enzymes range from 6 to 8 pH & function in acidic environments
Example:
Pepsin in the stomach functions at a very low pH (1-2)
Enzymes in the blood function best at a pH close to neutral (7)

47. Peat Bog:Soil very acidic-enzymes will not decompose

48. Metabolism
Energy

49. Metabolism
Is defined as the chemistry of living systems representing all chemical reactions that occur in an organism
Life processes are driven by energy
It describes the cells capacity to acquire energy
Used to store substances in cellular processes
Helps eliminate waste products
Helps reactions break apart nutrients to release energy

50. Cells use energy to do required work
Such as Movement
-cells can swim (flagellum)
-cells can change their shape
-cells crawl over one another & reach new positions in the embryo
2. To build new Molecules
- most are manufactured by a series of enzyme-catalyzed chemical reactions

51. Biochemical pathways
An ordered series of enzyme-catalyzed chemical reactions that forms a product in a step-by-step manner called biochemical pathways
Make specific molecules cells need
A biochemical pathway consist of a series of enzyme-catalyzed chemical reactions
The product of each reaction in a pathway becomes the reactant of the next reaction in the pathway

52. Biochemical pathways points…
Almost always involve at least 1 endergonic chemical reaction (b/c building molecules takes energy)
These reactions consume energy
Their products contain more energy than their reactant did
Nothing can happen until extra energy from an external source triggers the reaction

53. A biochemical pathway
Consist of a series of enzyme-catalyzed chemical reactions
The product of each reaction in a pathway becomes the reactant of the next reaction in the pathway

54. ATP (Adenine Triphosphate)  ADP (Adenine Diphosphate)
ATP supplies most of the energy that drives metabolism
Energy temporarily stored in ATP is made available for use by the cell when the Phosphate Group is transferred to another molecule (exergonic reaction)
The splitting of ATP into ADP + P is exergonic b/c energy is released into the environment

56. Phosphorylation vs Hydrolysis
Phosphorylation is the process of adding a phosphate group to a molecule making an ADP  ATP
Hydrolysis removes a phosphate group to form ADP making an
ATP  ADP
The ADP is then available to become recharged

57. Coupling Energy
AN ENDERGONIC REACTION DRIVEN BY THE SPLITTING OF ATP IS CALLED A COUPLED REACTION
2 parts of a coupled reaction
1. ATP-splitting
2. Endergonic Reaction

58. Coenzymes help transport Energy
High energy electrons are passed from the active site of the enzyme that is catalyzing a reaction to an organic molecule called a coenzyme
The coenzyme carries the e- to another enzyme that is catalyzing a different reaction
Coenzymes shuttle energy from one place to another

59. 1 of the most important coenzymes
Is Nicotinamide Adenine Dinucleotide (NAD+)
When NAD+ gains a H+ atom from the active site, it becomes NADH
It has been reduced

60. NAD+ accepts high energy electrons (paired with hydrogen) and becomes NADH, which transfers the electrons from one set of enzyme-catalyzed reactions to another. When NADH reaches an enzyme in a second set of reactions, it releases the electrons (and their energy) to the reaction that this enzyme is catalyzing. NAD+ can then return to the enzyme in the first set of reactions and get more electrons

61. Altering enzyme shape
Enzymes must have precise shape to work correctly, it is possible for a cell to control an enzymes activity by altering the enzymes shape
Many enzymes have shapes that can be altered by the binding of “signal” molecules to their surface
These are called Allosteric (al oh STEHR ihk) Enzymes
Allosteric means “other shape”

62. Repress vs Activate
If an allosteric enzyme is not able to bind to a substrate because of the new shape produced by the binding of a signal molecule, the signal molecule is said to “repress” the enzymes activity
If an allosteric enzyme is not able to bind to a substrate unless a signal molecule is bound to it, the signal molecule is said to “activate” the enzyme

63. Allosteric Site
The site where the signal molecule binds to an allosteric enzymes surface is called the allosteric site

64. Allorsteric Site in simple terms
Most noncompetitive inhibitors bind to a specific portion of the enzyme called the allosteric site {allos – other, steros – form}
In simple terms: site other than the active site on an enzyme that can switch on & off.
Sites serve as chemical on/off switch
The binding of the substrate to the site can switch the enzyme between active & inactive configurations

65. Too much chemical produced by a biochemical pathway
When a cell has enough chemical produced by a biochemical pathway, the pathway will shut down and waste overproduction is avoided

66. How does the pathway “know” to shut itself down?
The first enzyme in the pathway is an allosteric enzyme with a site that has the shape of the pathways product.
The binding of the product molecule to the allosteric enzyme inhibits the enzymes activity so the concentration of product is high
The first step in the pathway is turned off
The shutting down of a biochemical pathway caused by a key enzymes sensitivity to the level of pathways produce is called feedback inhibition
When the product drops, the pathway is reactivated