BIOL 304 - Chapter 15 Metabolism

What is the advantage of having enzymes organized in complexes for metabolic pathways?

increases speed and efficiency

allows efficient processing of unstable or toxic intermediates

catabolism

reactions that break down complex molecules into simpler ones to capture energy in useful forms

anabolism

reactions that construct a more complex molecule from simpler molecules by using energy

Recognize how coupling of reactions allows for unfavorable reactions to proceed

Overall free-energy change for a chemically coupled series of reactions equals the sum of the free energy changes of the individual steps.

allows for the coupling of thermodynamically unfavorable and favorable reactions in enzyme active sites

structure of ATP

why is phosphoryl transfer favorable?

ATP acts as the free-energy donor in most energy-requiring processes

ATP hydrolysis is exergonic

what does ATP hydrolysis power?

release of free energy

What are the structural features of ATP that give it high phosphoryl transfer potential?

1. orthophosphate (Pi) has greater resonance stabilization than any of the ATP phosphoryl groups

2. electrostatic repulsion of the triphosphate unit

3. the entropy of the products of ATP hydrolysis is greater

4. ADP and Pi are stabilized due to hydration

How do the sources of energy change in exercising muscle?

ATP in muscle sustains contractile activity for < 1 second

How does creatine factor into ATP production?

creatine kinase = catalyzes the regeneration of ATP from creatine phosphate and ADP

How proton gradients power the synthesis of ATP?

The oxidation of fuel molecules or phototrophy produces electrochemical potentials of ion gradients across membranes

90% of ATP is generated when the energy of a proton gradient is coupled with ATP synthesis (oxidative phosphorylation) 

Stage 1 of extraction of energy from whole food

large molecules in food are broken down into smaller units

Stage 2 of extraction of energy from whole food

small molecules are degraded to a few simple units that play a central role in metabolism

Stage 3 of extraction of energy from whole food

ATP is produced from the complete oxidation of the acetyl unit of acetyl CoA

activated carriers

small molecules to which a chemical group or electrons have been added, which can then be donated to another molecule

NAD+

accepts a proton and two electrons in the oxidation of a substrate to form NADH

FAD

accepts two protons and two electrons in the oxidation of a substrate to form FADH2

coenzyme A

a carrier of acyl groups that is derived from vitamin B5 (pantothenate)

Acetyl CoA

Acetyl linked to CoA is called acetyl CoA

Electrons of the C=O bond cannot form resonance structures with the C—S bond that are as stable as
those that they can form with the C—O bond

oxidation-reduction reaction

electron transfer

Useful energy is often derived from the oxidation of carbon compounds

group transfer reaction

Transfer of a functional group from one molecule to another

used to synthesize ATP and in signaling pathways, among others

hydrolytic reaction

Cleavage of bonds by the addition of water

commonly used to degrade large molecules

Carbon bond cleavage by means other than hydrolysis or oxidation

Two substrates yielding one product or vice versa. When H2O or CO2 are a product, a double bond is formed

isomerization

Rearrangement of atoms to form isomers

typically to prepare the molecule for a subsequent reaction

Ligation requiring ATP cleavage

Formation of covalent bonds (i.e., carbon–carbon bonds)

forms bonds using free energy from ATP hydrolysis

metabolism regulated by

1. altering the amount of enzymes

2. restricting the accessibility of substrates

3. regulating the catalytic activity of enzymes internally or externally

energy charge

proportional to the mole fraction of ATP plus half the mole fraction of ADP

ATP-generating pathways are inhibited, and ATP-utilizing pathways are stimulated under conditions of high-energy charge