Chapter 10: Introduction to Metabolism

Cells obtain energy from their environment in a form of

ATP

Pathway

The organization of chemical reactions that occur in cells

Each reaction of a pathway is catalyzed by an

Enzyme

Three Major Types of Work

1. Chemical

2. Transport

3. Mechanical

Sources of Energy

Sunlight and Chemicals

Chemical work

Convestion of complex molecules

Transport work

In and out of nutrients, wastes, and ions

Mechanical work

cell motility and movement of structures within cells

Thermodynamics

Energy changes in a cell and organisms

First Law of Thermodynamics

Energy can’t be created or destroyed

Second Law of Thermodynamics

Physical and chemical processes proceed in a way that entropy of the universe increases

Calorie

Amount of heat energy needed to raise 1g of water 1C

Joules

Units of work capable of being done

1 cal of heat = _ J

4.184

Equation for Gibbs Free Energy

DG = DH - TDS

DG < 0

Spontaneous

DG > 0

nonspontaneous

Equilibrium

The rate of the forward and reverse reactions is equal

Hydrolysis of ATP

ATP + H20 —> ADP + Pi + H’

Electron Transport Chain

Series of proteins and molecules that transfer electrons from one molecule to another

Electron Carriers/Donors in ETC

NAD, FAD

Electron Carriers

NAD, NADP, FAD, FMN, CoQ, Cytochromes, Nonheme Iron Proteins, Ferredoxin

Enzyme

Proteins that act as biological catalysts and accelerate chemical reactions

Catalyst

substance that increases the rate of a chemical reaction without changing itself

Substrate

reactant in enzymatic reaction

Apoenzyme

inactive, protein component of an enzyme

Cofactor

inorganic component of an enzyme (ions)

Coenzyem

organic molecule

Holoenzyme

functional, apoenzyme and cofactor

Oxidoreductase catalyzes

Redox reactions

Transferase catalyzes

Reactions involving the trasnfer of chemical groups between molecules

Hydrolase catalyzes

hydrolysis of molecules

Lyase catalyzes

Breaking of C-C, C-O, C-N and other bonds by a means other than hydrolysis

Isomerase catalyzes

Rearrangement of molecules to isomer form

Ligase catalyzes

Joining of two molecule using ATP

Activation Energy

Energy required to form transition-state complex

4 Environmental Effects on Enzyme Activity

pH, temperature, substrate concentration, enzyme concentration

Competitivie inhibitor

directly competes with substrate to the active/catalytic site

Noncompetitive inhibitor

binds enzyme at site other than active site causing enzymes’s conformational change

Ribozymes function

Catalyze peptide bond formation, self-splicing, self-replication

Three regulating mechanisms of metabolism

1. Metabolic Channeling

2. Enzyme production regulaiton

   1. Enzymatic Activity Control

Metabolic Channeling

localized enzymes and metabolites to specific parts of a cell

Compartmentation

distrubtion/storage of enzymes and metabolites to certain cell structures/organelles

Allosteric regulation

Allosteric effectors binds reversibly and noncovalently at a regulatory/allosteric site

Allosteric regulation changes and alters?

Shape of enzyme and activity of catalytic site

Covalent modification

reversible formation of a covalent bond between a small molecule and specific amino side chain on an enzyme that affects its activity

Feedback inhibition

Inhibition of one or more criticla enzymes in a pathway regulates entire pathway

Isoenzymes

Different form of an enzyme that catalyze same reaction