1. Ground Rules of Metabolism
CHAPTER 6

2. Importance of Free Radicals
Example: O2-
Highly Reactive
Formed by reactions to break down fats & amino acids.
Destructive to macromolecules.
Importance of Free Radicals

3. Dealing with Free Radicals
Cells deal with O2- by using a series of reactions.
A series of reactions is a pathway
The pathway for the removal O2- of from a cell uses two enzymes:
Superoxide Dismutase
Catalase
Dealing with Free Radicals

5. Energy kinetic energy – energy of motion
potential energy – stored energy
chemical energy – the potential energy available for release in a chemical reaction
thermal energy – kind of energy that is related to and/or caused by heat
Energy
Cells utilize chemical & electrochemical energy, and often release thermal energy

6. Laws of Energy Transformation (Thermodynamics)
first law of thermodynamics – energy can be transferred & transformed, but it cannot be created or destroyed
second law of thermodynamics – energy transfer or transformation increases the entropy (disorder or randomness) of the universe
Laws of Energy Transformation (Thermodynamics)

8. Energy Flow through Ecosystem

9. Free Energy Change (G)
portion of a system’s energy than can perform work -when temperature and pressure are uniform throughout the system
measure of a system’s instability (tendency to change to a more stable state)
chemical reactions that…
lose free energy (G  0) are spontaneous or exergonic
Ex: cellular respiration
absorb free energy (G  0) are endergonic
Ex: Photosynthesis
Free Energy Change (G)

10. chemical reactions that…
lose free energy (G  0) are spontaneous or exergonic
Ex: cellular respiration
absorb free energy (G  0) are endergonic
Ex: Photosynthesis

11. ATP (Adenosine Triphosphate)
immediate source of cellular energy
common to ALL living things
responsible for mediating most energy coupling reactions (use of exergonic reaction to drive an endergonic reaction)
10 million consumed & regenerated per second per cell
ATP (Adenosine Triphosphate)

12. the hydrolysis of ATP powers cellular work
the bond between the 2nd & 3rd phosphate groups breaks
the phosphate group is transferred to another molecule (phosphorylation)
Phosphate lost easily due to concentration of negative charges in phosphate tail.

13. Cellular Work 3 kinds of cellular work: mechanical transport chemical
ex: beating of cilia, muscle contraction, movement of chromosomes during cell division
transport
ex: active transport
chemical
ex: endergonic reactions
Cellular Work

14. ATP synthesis
requires energy
ATP hydrolysis
yields energy
ATP Cycle

15. Reactant- substance that enters a metabolic reaction or pathway; also called an enzyme’s substrate.
Intermediate- Substance formed between reactants and end products of a reaction or pathway.
Product- Substance left at end of reaction or pathway.
Cofactors- Coenzyme or metal ion; assists enzymes or taxis electrons, hydrogen, or functional groups between reaction sites.
Metal Ions, NAD+, FAD2+, NADP+
Reaction Basics

16. Reaction Basics AB + CD  AD + CB
Energy carrier- Mainly ATP in cells;couples energy-releasing reactions with energy-requiring ones.
Transport Protein- Protein that passively assists substances across a cell membrane or actively pumps them across.
AB + CD  AD + CB
Reaction Basics

17. Metabolism: Cell’s capacity to acquire energy and to use it to build, degrade, store, & release substances in controlled ways.
Metabolic pathway: Enzyme mediated series of reactions
catabolism = metabolic pathways that release energy by breaking down compounds
anabolism = metabolic pathways that consume energy to build compounds
Metabolism- Pathways

18. Equilibrium equilibrium = state of maximum stability
metabolism as a whole is never at equilibrium because of the constant flow of materials in & out of the cell
Equilibrium

19. many chemical reactions in the cell are slow (even spontaneous reactions)
cells use enzymes (catalytic proteins) to speed up reactions
enzymes lower the energy required to start a reaction (activation energy – EA)
Enzymes

20. Enzymes Show Specificity
the active site of an enzyme has a specific shape that is specific to the shape of the substrate that binds to it
induced fit hypothesis – substrate induces a change in the shape of the active site to create a snug fit
Enzymes Show Specificity

21. How Enzymes Work enzymes emerge from reactions in their original form
enzymes can catalyze both the forward & reverse reactions
How Enzymes Work

22. How Enzymes Lowering EA
active site can help substrates come together in the proper orientation for a reaction to occur
enzyme may stretch substrates toward their transition-state conformation
active site may provide a microenvironment that is more conducive to a particular type of reaction
active site may participate directly in the chemical reaction
How Enzymes Lowering EA

23. Substrate Concentration
as substrate concentration increases, reaction rate will increase to a point
when enzyme becomes saturated (all enzymes have their active sites engaged), the rate of the reaction will be determined by the rate at which the active site can convert substrate to product
Substrate Concentration

24. enzyme reaction rate increases with an increase in temperature to a point
initially, an increase in temperature makes substrates move faster and they are more likely to collide with the active sites of enzymes
when temperatures get too high, the enzyme denatures and the reaction stops
most human enzymes have optimal temperatures between 35-40C
Temperature

25. pH the optimal pH for most enzymes is between 6-8
when the pH deviates from the optimum, the enzyme denatures and the reaction stops
2 exceptions: pepsin & trypsin pH

26. competitive – mimic the substrate; bind to & block the active site
noncompetitive – bind away from the active site; cause the enzyme to change shape which changes the shape of the active site
inhibitors can play a regulatory role
Enzyme Inhibitors

27. Regulation of Enzyme Activity
allosteric regulation – binding of an activator or inhibitor molecule to a regulator site on an enzyme which stabilizes the functional or inactive form of the enzyme, respectively
ex: ADP acts as an activator & ATP acts as an inhibitor for several catabolic enzymes
cooperativity – one substrate binds to an enzyme and primes the enzyme to accept additional substrates
feedback inhibition – product of a metabolic pathway binds to & inhibits an enzyme that acts early in the pathway
Regulation of Enzyme Activity

28. Enzyme Videos
(General Function and Competitive Inhibition)
(student made claymation to Pac Man theme - watch smile turn to frown)
(student made - quirky but good)
(MCGraw Hill shows conformation change leading to product formation)
(Interleukin-1 bindng to surface protein receptor, leads to conformational change - good 3D shapes)
(shows protein structure and stick figure molecular binding)

29. Enzyme E.C.!!!!!!
By yourself or with a group, create and film an enzyme video, post it on YouTube and send me the link. Amount of E.C will be based on Mr. Newton’s SUBJECTIVE opinion on the quality of the video AND the sheer number of YouTube hits!