Enzymes

Metabolism

• The sum of all the chemical reactions in your body

• What does it mean if you have a high metabolism? Low?

• Does your metabolism change? Why?

Chemical Reactions

• Review:

A + B C AnabolicReactants Product

OR

A B + C CatabolicReactant Products

Types of Reaction

• Anabolic reactions: add things together

e.g. 2 glucose to maltose

• Catabolic reactions: cut things apart

e.g. maltose split into 2 glucose

Reversible Reactions

Metabolic Pathways

A B C D E

A series of reactions in which the product of one reaction becomes the reactant of the next.

Metabolic Pathways

• Very complex, lots of reactions

Thyroxin• protein hormone produced by the thyroid gland

• thyroid gland accumulates iodine to produce it

• Increases cell metabolism by binding to receptor sites, increases oxygen use

Cell Metabolism

Metabolism

Hyperthyroidism: too much thyroxin. Symptoms?

Hypothyroidism: not enough thyroxin. Symptoms?

Energy and Reactions

Exothermic reactions: reactions that release more energy than they require

Endothermic reactions: reactions that require more energy than they release

Energy can be in the form of heat or ATP.

Energy and Reactions

Activation energy: the energy required for a chemical reaction to take place.

Energy

Think of all the reactions in metabolism…

Where can we get all that energy?

Enzymes

• Biological catalysts: speed up reactions

• Lower activation energy

Structure and Function

Enzymes are PROTEINS

Need to remember protein structure

Enzymes

Proteins with tertiary or quaternary structure

Have a unique 3-D shape

Chemical Reactions

• Enzyme reactions

A + B CSubstrates Product

OR

A B + CSubstrate Products

Enzymes

SUBSTRATES PRODUCTS

Enzymes bind to substrate(s) at active site

Enzyme-Substrate Complex (E-S Complex)

Lock and Key

• Unique fit – one substrate per enzyme

Induced fit hypothesis

• As the E-S complex forms, stress is put on chemical bonds

• Can be anabolic or catabolic or both for some enzymes

Cofactors and Coenzymes

Co-factors: inorganic. Stabilize enzymes. E.g. Zn2+, Mg2+

Co-enzymes: organic. Assist in enzyme reactions.

e.g. NAD brings H+ ions

Factors that affect enzymes

1) Temperature

2) pH

3) Heavy metal ions

4) Inhibitors

5) Substrate & enzyme concentration

Temperature

• Enzymes function at an optimum temperature

• High temperatures denature enzymes

• Low temperature reduces particle energy

Denatured Protein

• H-bonds that hold tertiary shape break

• Loses specific 3-D shape, not reversible

pH

• Enzymes function at an optimum pH

• Conditions outside of that pH denature enzymes

Heavy Metal Ions

• Have strong positive charges

• Disrupt the electron configuration of enzymes

• Too many ions can denature enzymes

Inhibitors

Competitive: bind at active site and prevent substrate from binding

Non-competitive: bind at another site and alter enzyme shape preventing substrate from binding

Concentration• Increasing substrate concentration increases reaction rate to a

point

• Same for enzymes

Vitamins & Minerals

Why do you need them?

Digestive Enzymes

• Enzymes found in your digestive system that act in catabolic reactions

• Turn macromolecules (starch, protein, lipids) into monomers (glucose, amino acids, fatty acids and glycerol).

• Optimum temperature = 37o C• Optimum pH = varies

Mouth

• salivary glands

• produce enzyme salivary amylase

• pH 6.75-7

Stomach

• gastric cells produce gastric juice

• contains inactive pepsinogen, HCl

• HCl kills bacteria, activates pepsinogen by turning it into enzyme pepsin

• pH ~2.5

Small Intestine

• pancreas produces pancreatic juice

• contains bicarbonate ions, and the enzymes: trypsin, pancreatic amylase, nuclease, lipase

• bicarbonate ions (HCO3-) lower pH by “over-neutralizing” the acid

• pH ~8.4

Small Intestine

• duodenum produces intestinal juice

• contains enzymes peptidases (carboxypeptidase, aminopeptidase, dipeptidase) nucleosidases and phospatases, disaccharidases (maltase, lactase, sucrase)

Carbohydrates

Mouth

starch ------------------------ maltosesalivary amylase

Small intestine

starch --------------------------- maltosepancreatic amylase

disaccharides ------------------------ monosaccharidesdisaccharidases

Proteins

Stomach

proteins ---------------- polypeptides pepsin

Small intestine

polypeptides ---------------- peptides trypsin

peptides ---------------------- amino acids peptidases

Nucleic Acids

Small Intestine

nucleic acids ----------------- nucleotidesnucleases

nucleotides --------------------------------- sugar, phosphate, bases nucleosidases, phosphatases

Lipids

Small Intestine

lipids --------------------- fatty acids and glycerol lipases