INTRODUCTION TO METABOLISM

• Metabolism = the totality of an organisms chemical processes

• Inside cells thousands of chemical reactions occur within microscopic spaces

• Metabolism is concerned with the management of energy and chemical resources of the cell

• Pathways that build up complex compounds are called Anabolic

• Pathways that breakdown complex compounds are called Catabolic

• Often these complimentary reactions are paired

Energy

• Energy is the capacity to do work

• Kinetic energy is the energy of things in motion

• Potential energy is energy of non-moving matter; by virtue of its location or arrangement

• Energy can be converted from one form to another

Thermodynamics

• Thermodynamics is the study of energy transformations

• 1st Law of Thermodynamics = Energy cannot be created or destroyed

• 2nd Law of Thermodynamics = Every energy transfer or transformation increases the entropy (disorder) in the universe

Free Energy

• Free energy is the portion of a system’s energy that can perform work when temp. is uniform throughout the system. Ex In a living cell

• Delta G = Delta H - T Delta S : This is the free energy equation; This term is very important it determines whether reactions will “go” in systems

Free Energy Cont.

• Delta G = Delta H - T Delta S ( a triangle represents delta)

• Delta means “change in”

• G = G final state - G initial state

• T = C + 273

• S = entropy

• H = system’s total energy

Reactions in Biological Systems

• Chemical reactions are classified by their free energy status

• Exergonic reactions = proceed with a net release of free energy

• Endergonic = absorb energy from the environment. They need to be provided “power” to run

• Ex Breakdown of glucose exergonic but photosynthesis is endergonic

ATP and Cellular work

• ATP is a nucleoside that the cell uses to power the cell. It is the main energy currency of cells.

• ATP is composed of an adenine, a ribose, and PO4 group: the tri PO4 tail is unstable

• The bonds can be broken by hydrolysis

• The terminal phosphate is most unstable, when removed it yields - ( negative) 7.3 kcal of energy.

ATP Cont.

• Negative delta Gs mean the reaction is exergonic ( gives off energy)

• Positive delta Gs mean the reaction is endergonic ( needs energy to go)

• The cell can couple reaction yielding and needing ATP to make complex biochemical pathways go.

• ATP is a renewable resource it is recycled

Enzymes

• Most chemical reactions would occur too slowly in bio systems because the temps are fairly low

• Enzymes are chemical agents that change the reaction rate without being consumed or converted in the reaction process

• Enzymes speed reactions by lowering the activation energy

Enzymes cont.

• Enzymes are very specific

• Enzymes are proteins

• Chemical reactions involve bond a making and breaking

• The initial energy necessary to start the reaction is called activation energy

• Enzymes can “ recognize” their substrates WHY?

Enzymes Cont.

• The active site of an enzyme is the pocket where it attaches to the substrate

• Substrate------Product ( Enzyme) ; cofactors = helpers

• Factors affecting enzyme function and stability– Temp– pH– Salinity

Inhibitors

• Enzyme inhibition– Competitive = bind to active site– Non-competitive = bind to another area

Metabolic Control

• Not all metabolic pathways are simultaneously activated

• Feedback inhibition control is most common = pathway is turned off by a specific concentration of the end product