METABOLISM

ENERGY AND LIFE

METABOLISM

The totality of an organisms chemical processes.

CATABOLIC PATHWAYS

Degradative Processes

ANABOLIC PATHWAYS

Building Processes

Complexity ofComplexity of

MetabolismMetabolism

Bioenergetics – study of how organisms manage energy

THERMODYNAMICS

• 1ST Law of Thermodynamics – Energy can be tranferred or transformed, but it can be neither created or destroyed.

• 2nd Law of Thermodynamics – Every energy transfer or transformation increases the entropy (disorder or randomness) of the universe.

Organisms live at the expense of free energy

• Chemical reactions may be classified based on free-energy changes. They are either

– Exergonic – proceeds with a net release of free energy

– Endergonic – absorbs free energy from its surroundings to proceed

ATP Powers Cellular Work

• A cell does three main kinds of workMechanical - beating of cilia, muscle

contraction, chromosome movementTransport – crossing a membrane

against the concentration gradientChemical – building of polymers

What is ATP? The nitrogenous base adenine with a

chain of three phosphates groups attached to the ribose.

• When the terminal phosphate bond is broken, ATP becomes ADP. This is an exergonic reaction releasing 7.3kcal of energy per mole of ATP

The ATP Cycle

ENZYMES• Catalytic proteins• Substrate-specific • Lock and Key fit• Initiate chemical reactions without being

used in the reaction ( reused)• Named for their substrate usually and

have the suffix (-ase)

The Catalytic Cycle of an Enzyme

• Enzymes use a variety of mechanisms that lower activation energy and speed up a reaction.

• Enzymes allow reactions to take place at lower temperature ( body temperature).

Factors that affect enzyme activity• Temperature

– Up to a point, the velocity of the reaction increases with the increase in temperature

– Most enzymes function optimally around body temperature (between 35o-40oC)

– Above the optimal temperature, the hydrogen bonds of the enzyme disrupt and the enzyme is denatured

• pH– The optimal pH is between 6 and 8

Other Factors Affecting Enzyme Activity

• Cofactors – nonprotein helper– If it is organic, then

it is a coenzyme– Most vitamins are

coenzymes• Enzyme inhibitors

– Competitive site– Noncompetitive site