Chapter 15 - Metabolism (Extended)

Phototrophs

capture energy from sunlight

Chemotrophs

capture energy through the oxidation of chemicals

Metabolism

a highly integrated network of chemical reactions that carried out the fundamental cellular processes of extracting energy and synthesizing new material (starts with a molecule and ends with the formation of another molecule)

ATP

common energy currency that is a motif across all life forms; links energy releasing (exergonic) pathways with energy-requiring (endergonic) pathways

Metabolic Pathways

a series of linked reactions in which fuels are degraded and large molecules are constructed step by step

Catabolism

reactions that break down complex molecules, (fuels) into simpler ones (allows energy to be captured)

Anabolism

reactions that construct a more complex molecule from simpler components (requires energy)

Amphibolic pathways

a metabolic pathway that consists of reactions that can be anabolic or catabolic, depending on the energy conditions and biosynthetic needs of the cell

A thermodynamically unfavorable reaction can be driven by a ________ reaction

favorable

-ΔG

the reaction can occur spontaneously

+ΔG

the reaction can proceed under physiological conditions

The coupling of unfavorable reactions to favorable ones occur in the _____

active sites of enzymes

Metabolism is facilitated by the use of ____

ATP from light or the oxidation of food

ATP hydrolysis is ____

exergonic

the active form of ATP is usually a complex of ATP with ___ or ____

Mg²⁺or Mn²⁺

The free energy released in __________ is used to drive reactions that require an input of free energy (muscle contractions)

the hydrolysis of ATP

NAD⁺, FAD and coenzyme A (the acyl group carrier) are _______

derivatives of ATP

An unfavorable reaction can be made possible by coupling to ______

ATP hydrolysis

Through changes in protein conformation, molecular motors such as ____, ____, and ____ convert the chemical energy of ATP into mechanical energy

myosin, kinesin, and dynein

The active transport of ___ and ____ across membranes is driven by the phosphorylation of the sodium potassium pump by ATP and its subsequent dephosphorylation

Na+ and K+

Phosphoryl transfer potential

the tendency of organic molecules to transfer a phosphoryl group to an acceptor molecule

ATP has a _____ phosphoryl-transfer potential than glycerol 3-phosphate

higher

ATP has a high phosphoryl-transfer potential because of its:

Stabilization, electrostatic repulsion, increase in entropy, and its stabilization due to hydration

Used to compare the phosphoryl-transfer potential of phosphorylated compounds:

Standard free energies of hydrolysis

Compounds with a higher-phosphoryl-transfer potential than ATP:

PEP 1,3 - BPG and creatine phosphate

PEP can transfer its ______ to ADP to form ATP

phosphoryl group

Serves as a reservoir of high-potential phosphoryl-groups that can be readily transferred to ADP

Creatine phosphate in vertebrate muscle

____ is used to regenerate ATP from ADP every time we exercise, the reaction is catalyzed by _______

Creatine phosphate; creatine kinase

There is a large amount of _______ present in resting muscle

creatine phosphate

One of the primary roles of catabolism is:

the regeneration of ATP

Oxidative phosphorylation

the generation of ATP by proton gradients made by the oxidation of carbon fuels

Activated carrier

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

Frequently acts as coenzymes or cosubstrates in enzyme-catalyzed reactions

activated carriers

ATP is an ______ of _______ because phosphoryl transfer from ATP is an exergonic process

activated carrier; phosphoryl groups

Activated carriers of electrons for fuel oxidation

NADH and FADH2

In aerobic organisms, ___ is the ultimate electron acceptor in the oxidation of fuel molecules

O2

During fuel oxidation, ___ and ____ accept electrons

NAD+ and FAD (oxidized forms)

Activated carrier of electrons for reductive biosynthesis

NADPH

Coenzyme A

derived from vitamin B5 (pantothenate); an activated carrier of acyl group (two -carbon fragments)

Acyl groups are linked to CoA by _______ and the resulting derivative is _____

thioester bonds; acyl CoA

A _____ is more unstable than an oxygen ester

thioester

Acetyl CoA has a ____ acetyl-transfer potential because transfer of the acetyl group is ______

high; exergonic

Acetyl CoA carries an activated ____ group and ATP carries an activated ____ group

acetyl; phosphoryl

Many activated carriers are derived from ____

vitamins

Vitamins

organic molecules that are needed in small amounts in the diets of some higher animals

Lyases

enzymes that catalyze the reactions in which when CO2 or H2O is released, a double bond is formed (critical in glycolysis)

Hydrolytic reactions

cleave bonds by the addition of water (ex. proteins)

Isomerization reactions

rearrange atoms within a molecule (critical within the citric acid cycle)

Ligation reactions

form covalent bonds (carbon-carbon) by using free energy from ATP hydrolysis

Oxaloacetate is formed from _____ and ____ using energy from ATP to form the carbon-carbon bond

pyruvate; CO2

Energy charge

an index of the energy status of the cell; the concentration of ATP plus half the concentration of ADP all divided by the total adenine nucleotide concentration

ATP is energy-rich because its triphosphate unit contains

two phosphoanhydride linkages

Free energy is released by:

formation of new bonds, formation of noncovalent interactions with water, increase in entropy

Nucleoside monophosphate kinases

enzymes that phosphorylate nucleoside monophosphates

Nucleoside Diphosphate Kinases

enzymes that phosphorylate nucleoside diphosphates

ATP’s phosphoryl-transfer potential describes its:

tendency to transfer its terminal phosphoryl group to water

Oxidation-reduction reactions

electron transfer (in the citric acid cycle)

Group transfer reactions

transfer of a functional group from one molecule to another (phosphoryl-group transfer)

The conversion of citrate to isocitrate is an ______ reaction

isomerization

The formation of oxaloacetate from pyruvate and CO2 is a _____ reaction

ligation