The most important metabolic fuel in the human body is:

A. Sucrose

B. Starch

C. Protein

D. Cellulose

E. Glucose

When two monosaccharides undergo a condensation reaction:

A. a new monosaccharide is formed

B. a disaccharide is formed

C. a polysaccharide is formed

D. a starch is formed

E. hydrolysis occurs

Metabolism & Enzymes

I. Constraints on Reactions

II. Making Reactions Possible with ATP

III. Making Reactions Probable with Enzymes

IV. Why does Grandma take St. Joseph’s?

What is Metabolism?

• All the chemical reactions of the body

What is Metabolism?

• All the chemical reactions of the body

• Catabolism– breaking large molecules into smaller

molecules (hydrolysis)– releases energy (an exergonic process)

What is Metabolism?• All the chemical reactions of the body

• Catabolism– breaking large molecules into smaller molecules (hydrolysis)– releases energy (an exergonic process)

• Anabolism– builds a large molecule from smaller ones (dehydration

synthesis/condensation)– consumes energy (an endergonic process)

Metabolism & Enzymes

I. Constraints on Reactions

II. Making Reactions Possible with ATP

III. Making Reactions Probable with Enzymes

IV. Why does Grandma take St. Joseph’s?

Constraints on Reactions

• First Law of Thermodynamics– Energy can be converted from one form to another,

but it cannot be created or destroyed– Chemical energy is stored in macromolecules we eat– When bonds are broken, energy is released– We use this energy to power our bodies

Constraints on Reactions

• First Law of Thermodynamics– Energy can be converted from one form to another,

but it cannot be created or destroyed– Chemical energy is stored in macromolecules we eat– When bonds are broken, energy is released– We use this energy to power our bodies

• Second Law of Thermodynamics– In every energy transfer, some energy is lost as heat– Unless our bodies obtain energy from our

surroundings, we lose energy over time (entropy)

To counter the loss of energy (as heat), we add energy to our bodies in the form of food

Using ATP to Build Macromolecules

Using ATP to Build Macromolecules

endergonic

exergonicexergonic

(Breakdown of food)

ATP is Recycled

Metabolism & Enzymes

I. Constraints on Reactions

II. Making Reactions Possible with ATP

III. Making Reactions Probable with Enzymes

IV. Why does Grandma take St. Joseph’s?

Enzymes are Everywhere

Enzymes are Biological Catalysts

• Enzymes are proteins that function as biological catalysts– Increase the speed of chemical reactions– Increase likelihood of chemical reactions

Enzymes are Biological Catalysts

• Enzymes are proteins that function as biological catalysts– Increase the speed of chemical reactions– Increase likelihood of chemical reactions

• Can increase rate of chemical reactions by over 1,000,000X

• Bind with one or more reactants, termed substrates

Enzymes Bind to Substrates

• Bind with one or more reactants, termed substrates

• Enzymes are named after the substrate with which they bind– -ase forms the suffix (e.g., the enzyme

amylase digests the starch amylose)

Enzymes Bind to Substrates

• Enzymes can affect reactions by:

1) Placing reactants in proper orientation2) Create environment that promotes the reaction3) Chemically weakening the bonds within the reactants4) Donating electrons or protons to the reactants

How do Enzymes Work?

• Enzymes can affect reactions by:

1) Placing reactants in proper orientation2) Create environment that promotes the reaction3) Chemically weakening the bonds within the reactants4) Donating electrons or protons to the reactants

• Enzymes catalyze specific reactions

How do Enzymes Work?

• Enzymes can affect reactions by:

1) Placing reactants in proper orientation2) Create environment that promotes the reaction3) Chemically weakening the bonds within the reactants4) Donating electrons or protons to the reactants

• Enzymes catalyze specific reactions

• Enzymes are reusable (i.e. recycled)

How do Enzymes Work?

Enzymatic Reactions

Cofactors

• Cofactors bind to enzyme and change its shape, creating an active site (e.g., iron, copper, zinc, magnesium or calcium ions)

Cofactors

• Cofactors bind to enzyme and change its shape, creating an active site (e.g., iron, copper, zinc, magnesium or calcium ions)

• Vitamins are used to make organic cofactors called coenzymes.

• Many enzymes cannot function without cofactors.

Rate of Enzymatic Reactions

• The basis for chemical reactions is molecular and collision

Molecular Motion Animation

• Rates of reactions are affected by various factors:– Substrate and enzyme concentration– Temperature– pH

• Why do these influence reaction rates?

Rate of Enzymatic Reactions

Enzyme/Substrate Concentration

• Slow at low concentration

Enzyme

Enzyme/Substrate Concentration

• Slow at low concentration

• Increase until point of saturation

• Why does saturation occur?

Enzyme

Temperature

• Slow at low temperatures

Rea

ctio

n R

ate

Temperature (°C)

Temperature

• Slow at low temperatures

• Slow at high temperatures

• Explain rate at each arrow

Rea

ctio

n R

ate

Temperature (°C)

pH

• Enzymes function best within a specific pH range

• Why does pH alter enzyme function?

Competitive Inhibition• Slow down enzyme function• Effect is reversible

EnzymeEnzyme

Substrate

Active Site Inhibitor

• Binds to enzyme away from active site

Non-Competitive Inhibition

Substrate

Enzyme

Inhibitor

• Binds to enzyme away from active site

• Substrate no longer binds to active site

• Irreversible damage to enzyme function- Mercury, Cyanide

Non-Competitive Inhibition

Substrate

Enzyme

Inhibitor

Metabolism & Enzymes

I. Constraints on Reactions

II. Making Reactions Possible with ATP

III. Making Reactions Probable with Enzymes

IV. Why does Grandma take St. Joseph’s?

Aspirin is a Non-Competitive Inhibitor

• Inhibits COX enzyme, which functions in blood platelet aggregation

• What do blood platelets do?

• Hence, Aspirin reduces risk of a heart attack

Patient Profile: Laurie

• Ate a Cheese Omelet, Blueberry yogurt, and 2 glasses of chocolate milk at IHOP

• Symptoms: Diarrhea, Nausea, Stomach Ache

• What do you think Laurie suffers from?

Summary• Building macromolecules, is an anabolic process

that requires energy released from the catabolism of adenosine triphosphate (ATP)

• Enzymes bring together reactants and create an environment that favors a reaction

• Like any protein, the structure of an enzyme is critical to its function. Environmental conditions, cofactors, and inhibitors alter the structures of enzymes and hence alter their functions