1. Metabolism: Energy, Enzymes, and Regulation
Chapter 9
Metabolism: Energy, Enzymes, and Regulation

2. An Overview of Metabolism
metabolism is the total of all chemical reactions in the cell and is divided into two parts
catabolism – larger molecules are broken down to smaller molecules. Energy is released. Cellular respiration
anabolism – the synthesis of complex organic molecules from simpler ones. Energy is used.
photosynthesis

3. Overview of Metabolism
Figure 8.1

4. Energy and Work
energy
capacity to do work or to cause particular changes

5. Types of work carried out by organisms
chemical work
synthesis of complex molecules
transport work
take up of nutrients, elimination of wastes, and maintenance of ion balances
mechanical work
Cell motility and movement of structures within cells

6. ATP – quick source of energy in cells
Energy carrier molecule
Synthesis, movement, transport
ATP ADP + Phosphate + energy
ADP + phosphate + energy ---- ATP

7. The cell’s energy cycle
Figure 8.7

8. Oxidation-Reduction Reactions and Electron Carriers
many metabolic processes involve oxidation-reduction reactions (electron transfers)
electron carriers are often used to transfer electrons from an electron donor to an electron acceptor
Leo says ger

9. Oxidation-Reduction (Redox) Reactions
transfer of electrons from a donor to an acceptor
can result in energy release, which can be conserved and used to form ATP
Leo says ger

10. Oxidation reduction reactions are coupled
They take place simultaneously

12. Enzymes protein catalysts catalyst substrates products
have great specificity for the reaction catalyzed and the molecules acted on
catalyst
substance that increases the rate of a reaction without being permanently altered
substrates
reacting molecules
products
substances formed by reaction

13. Almost all the chemical reactions – enzymes
Biological catalysts
Speed up chemical reactions
Come out of the reaction unchanged
Absence enzymes – chemical reactions take place slow – cells cannot survive
Specific for its substrate
Substrate – substance with which the enzyme reacts.

14. Bring molecules together
Weaken bonds in a molecule – breaks down

15. sucrose
Glucose+ fructose
sucrase
Perfect fit

16. Structure and Classification of Enzymes
some enzymes are composed solely of one or more polypeptides
some enzymes are composed of one or more polypeptides and nonprotein components

17. Enzyme structure apoenzyme cofactor holoenzyme = apoenzyme + cofactor
protein component of an enzyme
cofactor
nonprotein component of an enzyme
prosthetic group – firmly attached – heme group – cytochrome c oxidase
coenzyme – loosely attached – NAD+
holoenzyme = apoenzyme + cofactor

18. Coenzymes They transport Substances
NAD+ transports electron and Hydrogen
Figure 8.14

19. Enzyme inhibitors – competitive, noncompetitive
Compete with the substrate for the active site.
Sulfanilamide – synthetic drug – UTI
Para aminobenzoic acid (PABA) folic acid
Enzyme
Drug takes the place of PABA on the enzyme
Inactivates the enzyme

20. Noncompetitive inhibitor binds to the allosteric site on the enzyme
Allosteric site – site other than the active site
Shape of the active site is changed
Enzyme is inactivated
Cyanide

21. PABA
sulfanilamide

22. denaturation
Enzymes are saturated
No free enzymes to interact
With the excess substrate.

23. Cell does not make
The product that is
In abundance
All 20AA for making
proeins
Leucine-isoleucine
Enzyme
Product –
Non competitive
Inhibitor of the enzyme
allosteric site
Feedback inhibition
Normal – regulate
synthesis
Product of a reaction
Inhibits the enzyme that
Catalyzes the reaction.
Reaction does not take place