INTRODUCTION TO

METABOLISM

Chapter 6: Page 1

• 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

Chapter 6: Page 2

• Pathways that build up complex compounds

are called Anabolic

• Pathways that breakdown complex

compounds are called Catabolic

• Often these complimentary reactions are

paired

Chapter 6 Page 3 : 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

Chapter 6 Page 4:

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

Chapter 6 Page 5: 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

Chapter 6 Page 6: Free Energy

Cont.

• ∆ G = ∆ H - T ∆ 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

Chapter 6 Page 7: 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

Chapter 6 Page 8 : 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.

Chapter 6 Page 9 : 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

Chapter 6 Page 10: 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

Chapter 6 Page 11: 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?

Chapter 6 Page 12: 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

Chapter 6 Page 13: Inhibitors

• Enzyme inhibition

– Competitive = bind to active site

– Non-competitive = bind to another area

Chapter 6 page 14 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