Chapter 8:Chapter 8:An IntroductionAn Introductionto Metabolismto Metabolism

• Metabolism = Catabolism + Anabolism

• Catabolic reactions are energy yielding involved in the break down of more complex molecules into simpler ones

• Anabolic reactions are energy requiring

• involved in the building up of simpler molecules into more-complex ones

• Bioenergetics-study of how organisms use their energy resources

Metabolism

11stst & 2 & 2ndnd Laws of Thermodynamics Laws of Thermodynamics

“Energy can be transferred or

transformed but neither created nor destroyed.”

“Every energy transfer or transformation increases the

disorder (entropy) of the universe.”

Note especially the waste heat

transform energy to new forms (1st law)

are less than 100% efficient (2nd law)

Organisms tend to use energy in a more organized fashion therefore requiring energy ( always fighting entropy)

Organisms as TransformersOrganisms as Transformers

• G-Free energy-energy that is available to perform work

• H- total energy (enthalpy) • S – entropy• ΔG = ΔH - T ΔS • If ΔG = negative, reaction is

spontaneous• If ΔG = positive, reaction needs energy

Free energy change- Free energy change- ΔΔGG

Metabolic Reactions

• Exergonic reaction- releases energy so G decreases and ΔG is negative

• Endergonic reaction- absorbs free energy so G increases and ΔG is positive

Exergonic ReactionsExergonic Reactions

Energy released

“Food”

KNOW THIS CHART!

Endergonic ReactionsEndergonic Reactions

Energy required

“Work”

KNOW THIS CHART!

Cells do different kinds of work

Mechanical- muscles

Transport- cell membrane

Chemical- endergonic reactions

Summary of Metabolic CouplingSummary of Metabolic Coupling

Exergonic processes drive Endergonic processesATP is an agent of energy coupling

It is created by one process and is used in another!

Adenosine Triphosphate (ATP)

http://www.bozemanscience.com/atp-adenosine-triphosphate

Cellular work is always powered by ATP Cellular work is always powered by ATP

• Hydrolysis releases 7.3 kcal of energy per mole ATP

• Can heat the environment (keep us warm)

• ATP is renewable

• Catalysts speed up a reaction without being consumed

• An enzyme is a catalytic protein

• Catalysts reduce activation energy- energy needed to get a reaction going

Enzymes

KNOW THIS CHART !!!!KNOW THIS CHART !!!!

Enzymes lower activation

energy

Catalysis as Viewed in 3D

Active site is site of catalysis

Substrate is reactant that the enzyme works on

Induced Fit- used to beCalled “lock and key”

Enzymes and substrate brought into position for optimum interaction

• Temperature- increases enzyme action until it denatures

• pH 6-8 depending on environment or organ

• Cofactors- non-protein helpers (minerals)

• Coenzymes- vitamins

Environmental Factors and Enzymes

Each Enzyme has Opt. Temp and pHEach Enzyme has Opt. Temp and pH

Denatured?

Optimal pH of most

enzymes fall in 6-8 range

Competitive Enzyme Inhibitors

• resembles the substrate and bonds to active site, blocking it

• Is reversible by increasing substrate concentration

Noncompetitive Enzyme Inhibitors

• Binds to another site (allosteric site) not the active site

• Changes shape of protein so it can no longer function

• Toxins and Poisons- sarin, DDT

• Sarin (nerve gas ) attaches to acetylcholine- important nervous system enzyme

• DDT• Antibiotics blocks

active sites of bacterial enzymes

Negative Effects of Inhibition Negative Effects of Inhibition

• Not all inhibitors are bad. • Some are used to

regulate enzyme activity

• Can activate or inhibit enzyme

• Example-speeding up or slowing down of ATP production

Allosteric Regulation of Enzymes

Feedback Inhibition Pathway

is

switched

off by the

binding

of the

product to

the

allosteric site

ATP Feedback Inhibition