CELL METABOLISM

Enzymes Definition

Catalysts Proteins that speed up chemical reactions by lowering the energy of activation.

LOWERING THE ENERGY OF ACTIVATION

Substrate

ENZYMESCharacteristics

Do not change or get used up.

Is specific to one substrate.

Does not make a reaction happen if it would not normally occur.

ENZYMESStructure

Three-dimensional protein frameworkActive siteCofactors Coenzymes

Organic molecules that become part of the enzyme structure.

Metal ions Inorganic metals that help shape enzyme structure.

ENZYMESMode of Action

Chemical reactionsMust have contact

Fig. 6.6b

ENZYMESMode of Action

Chemical reactionsMust have contactMust have sufficient force

ENZYMESMode of Action

Chemical reactionsMust have contactMust contact with sufficient forceMust have proper orientation

ENZYMESMode of Action

Method Induced Fit

A substrate promotes reactivity by altering the shape of the active site for a more precise fit.

Lock & Key

Induced Fit

PRIMARY PROTEIN STRUCTURE

20 & 30 PROTEIN STRUCTURE

ENZYMESExternal Effects

Temperature Cold Temperatures

Slow reactions down Warm Temperatures

Speed reactions up Hot Temperatures

Denature protein enzymes

ENZYMESExternal Effects

Ph Strong Acids

Denature proteins Strong Bases (Alkaline)

Denature Proteins

ENZYMESOptimum Environment

Resulting effects depend on the strength of the crosslinkages between amino acids.

METABOLISM

DefinitionOrderly sequence of chemical reactions that change substrates into products.

Product 1

Substrate 2

Substrate 1

Product 2

Substrate 3

Product 3

Substrate 4

Final End Product

METABOLISM

PathwaysCatabolic (Degradative)[Exergonic] Breaking down of complex molecules to simpler products with the release of

energy.

Energy

METABOLISM

PathwaysAnabolic (Biosynthetic) [Endergonic] Synthesis of complex molecules with a net input of energy.

Fig. 6.6b

Energy

Fig. 6.3

ANABOLIC

CATABOLIC

ANABOLIC

CATABOLIC

sHEAT

sHEAT

METABOLISMControl

Inhibitors Competitive

Blocking of active site to prevent enzyme action

METABOLISMControl

Inhibitors Noncompetitive Changing of the shape and chemistry of

an enzyme to prevent action.

METABOLISMNoncompetitive

Method Feedback Inhibition

Mechanism by which an end product shuts down the first enzyme of the pathway.Allosteric Enzymes containing an additional binding site for allosteric control.