1. Cellular Metabolism Energy as it relates to Biology
Energy for synthesis and movement
Energy transformation
Enzymes and how they speed reactions
Metabolism and metabolic pathways
Catabolism (ATP production)
Anabolism (Synthesis of biologically important molecules)

2. Energy in Biol. Systems:
General definition of energy: Capacity to do work
Chemical, transport, movement
First Law of Thermodynamics: Energy can neither be created nor destroyed
Ultimate source of energy: Sun!
2 types of energy:
Kinetic energy = motion
examples ?
Potential energy = stored energy
Fig 4-2

3. Energy (E) Transfer Overview
Figure 4-1

4. Potential Energy heat (~ 70% of energy Kinetic Energy WORK
used in physical exercise)
Kinetic Energy
WORK

5. Bioenergetics = study of energy flow through biol. systems
Chemical reactions transfer energy
A + B C + D
Products
Substrates or
reactants
Speed of reaction = Reaction rate
Initial force = Activation Energy

6. Potential Energy Stored in Chemical Bonds of Substrate can be . . .
transferred to the chemical bonds of the product
released as heat (usually waste)
used to do work (= free energy)

7. Chemical Reactions p 93 Activation energy
Endergonic vs. exergonic reactions
Coupled reactions
Direct coupling vs. indirect coupling
Reversible vs. irreversible reactions

8. Activation Energy
Fig 4-3

9. Endo- and Exergonic Reactions
Which is which??
ATP + H2O ADP + Pi + H+ + Energy

10. Enzyme (= Biol. Catalyst)
Some important characteristics of an enzyme:
Enzymes are proteins
 rate of chemical reaction by lowering activation energy
is not changed itself
It may change DURING the reaction
does not change the nature of the reaction nor the result
is specific
Fig 4-6

11. Enzymes lower activation energy:
All chemical reactions in body must be conducted at body temp.!!
How do enzymes lower activation energy ?

12. Some more characteristics of enzymes:
Usually end in –ase
Inactive form: -ogen
in few cases RNA has enzymatic activity (eg: rRNA  peptide bond)
Isoenzymes may be produced in different areas of the body
E.g., LDH

13. Active Site:
Small region of the complex 3D structure is active (or binding) site.
Enzymes bind to substrate
Troponin I and T are structural components of cardiac muscle. They are released into the bloodstream with myocardial injury. They are highly specific for myocardial injury--more so than CK-MB--and help to exclude elevations of CK with skeletal muscle trauma. Troponins will begin to increase following MI within 3 to 12 hours, about the same time frame as CK-MB. However, the rate of rise for early infarction may not be as dramatic as for CK-MB.
Troponins will remain elevated longer than CK--up to 5 to 9 days for troponin I and up to 2 weeks for troponin T. This makes troponins a superior marker for diagnosing myocardial infarction in the recent past--better than lactate dehydrogenase (LDH). However, this continued elevation has the disadvantage of making it more difficult to diagnose reinfarction or
Old: Lock-and-key model / New: Induced-fit model

14. Enzyme-substrate interaction: The old and the new model
Lock and Key:
Induced fit:

15. Naming of Enzymes Kinase Phosphatase Peptidase Dehydrogenase
mostly suffix -ase
first part gives info on function
Kinase
Phosphatase
Peptidase
Dehydrogenase
examples

16. Isoenzymes = different models of same enzyme (differ in 1 or few aa)
Catalyze same reaction but under different
conditions and in different tissues/organs
Examples:
Amylase
LDH → importance in diagnostics
(LDH) Lactate dehydrogenase  - Total LDH will begin to rise 2 to 5 days after an MI; the elevation can last 10 days.
U/L
Normal Adult Range: U/L Optimal Adult Reading: 125

17. Enzyme Activity depends on
Proteolytic activation (for some)
Cofactors & coenzymes (for some)
Temperature pH
Other molecules interacting with enzyme
Competitive inhibitors
Allosteric modulators

18. 1) Proteolytic Activation
Also
Pepsinogen Pepsin
Trypsinogen Trypsin

19. 2) Cofactors & Coenzymes
structure:
Inorganic molecules (?)
function:
conformational change of
active site
structure:
Organic molecules (vitamin
derivatives, FADH2 ....)
function:
act as receptors & carriers
for atoms or functional
groups that are removed
from substrate

20. 3)

21. 4) Molecules interacting with enzyme
Competitive inhibitors: bind to active site
Fig 4-13
block active site
E.g.: Penicillin binds covalently (= irreversibly
to important bacterial enzyme active site)

22. 4) Molecules interacting with enzyme, cont’d
Allosteric modulators (fig 4-14): bind to enzyme away from active site change shape of active site (for better or for worse)
Special case:
= end product inhibition

23. Allosteric Modulation

24. Reaction Rate Depends on Enzyme & Substrate Concentration

25. Reversible Reactions follow the Law of Mass Action

26. Three Major Types of Enzymatic Reactions:
Oxydation - Reduction reactions
(transfer of electrons or protons (H+))
Hydrolysis - Dehydration reactions
(breakdown & synthesis of water)
Addition-Subtraction-Exchange (of a functional group) reactions

27. ?