METABOLISM ENERGY AND LIFE. METABOLISM The totality of an organisms chemical processes. CATABOLIC...

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