1. A handful of peanuts contains enough energy to boil a quart of water
Energy: Potential & Kinetic Energy
A handful of peanuts contains enough energy to boil a quart of water
It takes about 10 million ATP molecules per second to power an active muscle cell

2. About 75% of the energy generated by a car’s engine is lost as heat
You’d have to run about 14 miles to burn the calories from a pepperoni pizza

3. Thermodynamics: 1st Law of Thermodynamics:
total amount of energy in universe is constant
energy can not be created or destroyed
energy is just converted from one form to another

4. Efficiency of chemical reactions is NOT 100%
2nd Law of Thermodynamics:
The second law of thermodynamics states that energy cannot be changed from one form to another without a loss of usable energy.
Efficiency of chemical reactions is NOT 100%
some energy escapes in the form of heat
not available to do work
a product of all energy conversions
pg 100

5. Cells and Energy

6. Conservation of Energy
Energy is defined as the capacity to perform work
Kinetic energy is the energy of motion
Potential energy is stored energy
see Fig 6.5

7. Chemical Energy Is a form of potential energy
Is found in food, gasoline, and other fuels
What drives our cellular metabolism
work of cells is powered by potential energy in molecular bonds
Fuel rich in
chemical
energy
Heat
Waste products
poor in chemical
Gasoline
Oxygen
Combustion
Kinetic energy
of movement
Water
(a) Energy conversion in a car

8. Chemical reactions either store or release energy:
Energy is stored (endergonic)
making a chemical bond
form of potential energy
ex: photosynthesis - storage of energy in sugar
Energy is released (exergonic)
initial energy require to start reaction
breaking a chemical bond
ex: cellular respiration – glycolysis

9. energy needed to get reaction started
Activation Energy:
energy needed to get reaction started
kinetic energy converted to potential energy
heat energy released
conversion of potential energy to kinetic energy
fig 6.5
biological reactions happen too slowly on their own without help

10. Enzymes biological catalysts
speed up chemical reactions by lowering activation energy
less energy needed to start reaction

11. How Enzymes Work: proteins or nucleic acids
binding to specific molecule
stressing bonds of molecules to make reactions MORE likely to occur
enzymes LOWERS the activation energy of a reaction
enzyme shape determines its activity
fig 6.6

12. Degradation vs. Synthesis
Enzyme complexes with a single substrate molecule
Substrate is broken apart into two product molecules
Synthesis:
Enzyme complexes with two substrate molecules
Substrates are joined together and released as single product molecule

13. How Enzymes Work: specificity
space/binding sites specific to particular molecule
e.g., sucrase breaks down sucrose!
used over and over
enzymes may temporarily transform, but unchanged by reaction
optimal conditions
e.g., temperature, pH
Pepsin is an enzyme whose precursor form (pepsinogen) is released by the chief cells in the stomach and that degrades food proteins into peptides.
Trypsin is produced in the pancreas as the inactive proenzyme trypsinogen. Trypsin cleaves peptide chains mainly at the carboxyl side of the amino acids lysine or arginine, except when either is followed by proline. It is used for numerous biotechnological processes
fig 6.8 & 6.9

14. Biochemical Pathways:
series of chemical reactions where the product of one reaction is the substrate (reactants) of the next reactions
frequently embedded in a membrane where the enzyme assembly is held in close contact to facilitate chemical reactions

15. Begins with a particular reactant ( A ),
Proceeds through several intermediates ( B – F ) , and
Terminates with a particular end product ( G )
Each enzyme accelerates a specific reaction
Each reaction in a metabolic pathway requires a unique and specific enzyme
End product will not appear unless ALL enzymes present and functional
E1 E2 E3 E4 E5 E6
A  B  C  D  E  F  G

16. The active site complexes with the substrates
Causes active site to change shape
Shape change forces substrates together, initiating bond
Induced fit model

17. Regulation of enzymatic activity:
enzyme activity may be repressed by the presence of a repressor molecule which changes the shape of the active site
enzyme activity may be “activated” by the binding of an activator; changing the shape of the enzyme which then allows the substrate to fit the active site

18. product blocks production
Enzyme Inhibitors
Competitive inhibitor
Can inhibit a metabolic reaction
Bind to the active site, as substrate impostors
Noncompetitive inhibitor
Bind at a remote site, changing the enzyme’s shape (like repressor)
In some cases, this is called feedback regulation
product blocks production

19. Factors Affecting Enzyme Activity: Feedback Inhibition

20. Irreversible Inhibition
Materials that irreversibly inhibit an enzyme are known as poisons
Cyanides inhibit enzymes resulting in all ATP production
Penicillin inhibits an enzyme unique to certain bacteria
Heavy metals irreversibly bind with many enzymes
Nerve gas irreversibly inhibits enzymes required by nervous system

21. Factors Affecting Enzyme Activity
Cells can affect presence/absence of enzyme
Cells can affect concentration of enzyme
Cells can activate or deactivate enzyme
Enzyme Cofactors
Molecules required to activate enzyme
Coenzymes are organic cofactors, like some vitamins
Phosphorylation – some require addition of a phosphate

22. Which of the following statements regarding enzymes is FALSE?
a. Enzymes are proteins that function as catalysts.
b. Enzymes display specificity for certain molecules to which they attach.
c. Enzyme function is dependent on the three-dimensional structure of the enzyme.
d. Enzymes work optimally at the specific pHs and temperatures associated with the environment (e.g., stomach) in which they are produced.
e. An enzyme be may be used many times over, but will eventually be worn down and replaced.

23. ATP - adenosine triphosphate
ENERGY STORAGE MOLECULE!
energy currency of body
highly reactive:
ADP + Pi + energy  ATP
when bonds break -- energy released
when bonds formed -- energy input is stored
ATP molecules cycle over and over:
Coupled reaction

24. Coupled Reactions
Figure 6.4

25. Examples of work:
muscle contractions
breakdown of food
make proteins - grow
cilia moving particles out of airways
cellular work = metabolism
“Cellular Work”
drives functioning of body
needs energy
to make energy need oxygen
Active transport
muscle contraction

26. Oxidative-Reduction
oxidation
oxygen has a strong pull on electrons
oxidation is the process of oxygen (or another electron acceptor) pulling away an electron
an oxidized molecule has LOST an electron
reduction
reduced atoms or molecule has GAINED an electron
may gain more than just an electron (e.g., along with H+)
energy is transferred along with the electron

27. Photosynthesis Respiration Water + Carbon Dioxide Glucose + Oxygen
Glucose + Oxygen Water + Carbon Dioxide
oxidation
reduction
oxidation
reduction

28. Electron Transport Chain
Membrane-bound carrier proteins found in mitochondria and chloroplasts
Physically arranged in an ordered series
Starts with high-energy electrons and low-energy ADP
Pass electrons from one carrier to another
Electron energy used to pump hydrogen ions (H+) to one side of membrane
Establishes electrical gradient across membrane
Electrical gradient used to make ATP from ADP – Chemiosmosis
Ends with low-energy electrons and high-energy ATP

29. A Metaphor for the Electron Transport Chain

30. Chemiosmosis

31. Glucose molecules provide energy to power the swimming motion of sperm
Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing ______.
a. chemical energy into kinetic energy
b. chemical energy into potential energy
c. kinetic energy into potential energy
d. kinetic energy into chemical energy

32. For the following reaction, energy is released when the reaction goes which direction?
ADP + P  ATP
right to the left
left to the right
“a” and “b”
depends on the presence of enzymes
depends on temperature

33. Cycle of Energy: Cellular Respiration & Photosynthesis
fig 6.11
photosynthesis: conversion of light energy into chemical energy
sunlight into glucose (carbohydrate)
cellular respiration: conversion of potential energy w/in chemical bonds (w/in carbohydrate) into kinetic energy (cellular work)