CELL METABOLISM Enzymes Definition Catalysts Proteins that speed up chemical reactions by lowering the energy of activation.

LOWERING THE ENERGY OF ACTIVATION Substrate

ENZYMES Characteristics Do not change or get used up. Is specific to one substrate. Does not make a reaction happen if it would not normally occur.

ENZYMES Structure Three-dimensional protein framework Active site Cofactors Coenzymes Organic molecules that become part of the enzyme structure. Metal ions Inorganic metals that help shape enzyme structure.

ENZYMES Mode of Action Chemical reactions Must have contact

Fig. 6.6b

ENZYMES Mode of Action Chemical reactions Must have contact Must have sufficient force

ENZYMES Mode of Action Chemical reactions Must have contact Must contact with sufficient force Must have proper orientation

ENZYMES Mode 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

2 0 & 3 0 PROTEIN STRUCTURE

ENZYMES External Effects Temperature Cold Temperatures Slow reactions down Warm Temperatures Speed reactions up Hot Temperatures Denature protein enzymes

ENZYMES External Effects Ph Strong Acids Denature proteins Strong Bases (Alkaline) Denature Proteins

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

METABOLISM Definition Orderly 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 Pathways Catabolic (Degradative)[Exergonic] Breaking down of complex molecules to simpler products with the release of energy.

Energy

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

Fig. 6.6b Energy

Fig. 6.3

ANABOLIC CATABOLIC ANABOLIC CATABOLIC sHEAT

METABOLISM Control Inhibitors Competitive Blocking of active site to prevent enzyme action

METABOLISM Control Inhibitors Noncompetitive Changing of the shape and chemistry of an enzyme to prevent action.

METABOLISM Noncompetitive 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.