+ sbi4u biochemistry ms. manning enzymes. 1. what are enzymes and what is their role in normal...

+SBI4U

BIOCHEMISTRY

Ms. ManningEnzymes

1. What are enzymes and what is their role in normal cellular function?

2. What are the chemical structures and mechanisms of various common enzymes?

3. What are the factors that affect the function of enzymes in cellular processes?

4. Why/how are enzymes used in the food and pharmaceutical industry?

Essential Questions:

What does this look like?

Map of Glucose Metabolism

+Homework Question:

What is a metabolic (biochemical) pathway?

What is the role of enzymes in metabolic pathways?

http://highered.mcgraw-hill.com/classware/ala.do?isbn=0072965819&alaid=ala_1032272&showSelfStudyTree=true



+How are macromolecules brought into the body converted into molecules that make up the body?

The body’s metabolism consists of a large number of biochemical pathways that consist of sequences of chemical reactions.

convert substrate molecules into specific products needed by the body.

+ Types of Biochemical Pathways

There are two fundamental types of biochemical pathways.

1.Anabolic pathways build complex products from less complex substrates

2.Catabolic pathways break down complex molecules to make energy available for biological processes.

+Which of these reactions are: a) anabolicb) catabolic?

1. Neutralization (acid-base) reaction

2. Hydrolysis reaction

3. Oxidation-reduction (redox) reaction

4. Condensation (dehydration) synthesis reaction

+Enzymes

Proteins (globular structure) that catalyze chemical reactions

In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzymes converts them into different molecules, called the products

Why is an enzyme called a catalyst?

+Elephant Toothpaste Recipe

Recipe:- Hydrogen Peroxide- Soap

2 H2O2 O2 + 2 H2O

What will happen to the new recipe when a catalyst is added?

+Enzyme Characteristics

Speed up chemical reactions!

Almost all cellular reactions need enzymes to occur at significant rates.

Without enzymes, chemical reactions would still occur, but they would happen much to slowly to sustain life.

What characteristic was presented in the demo?

+How do enzymes work?




+Enzymes in Digestion

+Enzyme Characteristics

Enzymes are specific for one particular reaction or group of related reactions.

What characteristic was presented in the lock and key activity?

Lactose(milk sugar)

Lactase

Triglycerides(lipid)

Lipase

Amylose(starch)

Amylase

Protein

Protease

+Homework Question: #3-4, pg. 115

What is the difference?

+Homework Question: #1 pg. 115

- Enzymes called catalysts because they speed up chemical rxns

- Interact with substrates to convert them to products

- Substrates drawn to active site through weak bonds

- Intra-substrate bonds weakened and substrate is split apart

- Weakening of intra-substrate bonds by enzyme makes rxn occur faster

Enzyme Action and the Hydrolysis of Sucrose


Enzyme sucrase breaks down a molecule of sucrose into glucose and fructose


+Homework Question: #2, pg. 115

Catabolic – enzyme breaks substrate apart – exergonic reaction (yeilds energy)

Anabolic – enzyme builds larger substrate by joining two substrates – endergonic reaction (requires energy)

+Enzyme Structure

Hormone-sensitive lipase

HSL catalyzes the breakdown of stored fat

The active site of HSL (green) catalyzes the breakdown of TGs

in a process called Lipolysis.

Contreras J A et al. J. Biol. Chem. 1996;271:31426-31430

©1996 by American Society for Biochemistry and Molecular Biology

HSL + H2O (hydrolysis)

FA

FA

FAFA

Triglyceride

FAFA Diglyceride

Adipocyte(fat cell) TGTG

TG

+Activation Energy and Enzymes

+What is activation energy?

a) The thermal energy associated with random movements of molecules

b) The energy released through the active breaking of chemical bonds

c) The difference in free energy between reactants and products

d) The energy required to initiate a chemical reaction

+Explain the role of activation energy in a reaction. How does an enzyme affect activation energy? Activation energy the amount of energy

needed to trigger the reaction.

Without reaching the activation energy, reactions can't take place.

Enzymes catalyze this process by lowering the amount of energy required to activate the reaction.

+Activation Energy and EnzymesThe amount of activation energy that is required is considerably less when enzyme is present.

+Factors that Affect Enzyme Activity (reaction rate)

Q#1-4 pg. 116 on enzyme worksheet

Enzyme is said to be denatured – no longer a catalyst

Other Regulators of Enzyme Activity

Enzyme Cofactors (pg. 117)Q#1 - Describe the general role of cofactors in enzyme activity

Non-protein, bound to enzyme

May be organic or inorganic ions

Enhance enzyme activity - “helper”change enzyme active site shapemake active site more reactive

Examples of Inorganic CofactorsMg in Chlorophyll

Fe in heme group of hemoglobin

Organic CofactorsActive site

Enzyme

Active site

Enzyme

Prosthetic group(perm. attached)

Coenzyme(detaches)

Prosthetic Groups

Coenzymes

e.g., FAD

e.g., NAD

Important Organic CofactorsNicotinamide Adenine Dinucleotide (NAD)

coenzyme derived from vitamin B3

carries and transfers electrons and functions as oxidizing agent in redox reactions

Active site

Enzyme

Coenzyme(detaches)

Coenzyme

e.g., NAD

Important Organic CofactorsFlavin Adenine Dinucleotide

(FAD)

prosthetic group

like NAD, FAD functions as a reducing agent in cellular respiration and donates electrons to the electron transport chain

Active site

Enzyme

Prosthetic group(perm. attached)

Prosthetic Group

e.g., FAD

+Covalent Modulation

Enzymes can be activated or inactivated by covalent modification.

A common example is phosphorylation of an enzyme (addition of a phosphate group to the amino acids serine, threonine, or tyrosine) mediated by another enzyme called a kinase .

The phosphorylation is reversible, and other enzymes called phosphatases typically catalyze the removal of the phosphate group from the enzyme.

+Enzyme Inhibitors

Enzymes may become deactivated

Temporarily or Permanently

Types of InhibitorsReversible InhibitorsIrreversible Inhibitors

+Reversible Inhibitors

Used to control enzyme activity

Involves the substrate or the end product of the reaction

For example: a build up of the end product – called feedback inhibitionhttp://highered.mcgraw-hill.com/classware/ala.do?alaid=ala_1032273

+Competitive Inhibitors Competitive Inhibitors have a similar shape as the substrate

Compete with the substrate to bind to the active site, but no reaction occurs

Block the active site so no substrate can fit

Competitive Inhibition

+Non-Competitive Inhibitors Binds to a different site on the enzyme

Does not compete with the substrate to bind to the active site

Two ways to non-competitively inhibit the enzyme:1. slow down the reaction or 2. changes the shape of the active site (allosteric inhibition)

Which of the following diagrams represents allosteric inhibition?

+(a) Reaction

Substrate

enzyme

Inhibitor site

active site

Substrate binds with the active site of enzyme

Reaction occurs and product molecules are produced

enzyme

Inhibitor site

Inhibitor

active site

Inhibitor binds with the inhibitor site of the enzyme

Substrate may still bind with the enzyme but the reaction rate is reduced

(b) Inhibition

(a) Reaction

enzyme

active site



(b) Inhibition

enzyme

Inhibitor

active site

Substrate

Substrate

Inhibitor binds with the inhibitor site of the enzyme and changes the structure of the active site

Inhibitor prevents binding of the substrate by changing the active site shape

+(a) Reaction

Substrate

enzyme

Inhibitor site

active site



enzyme

Inhibitor site

Inhibitor

active site

Inhibitor binds with the inhibitor site of the enzyme

Substrate may still bind with the enzyme but the reaction rate is reduced

(b) Inhibition

Check for Understanding

Q#2 – Distinguish between competitive and non-competitive inhibition

Competitive

inhibitor competes with the substrate for binding to the active site of the enzyme and prevents reaction

Non-competitive

inhibitor does not compete for the active site,

binds to a different site,

either slows down or completely prevents reaction.

Check for Understanding

Q#2 – Explain how allosteric inhibitors differ from other non-competitive inhibitors:

While non-competitive inhibitors reduce enzyme activity and slow down the reaction rate, allosteric inhibitors block the active site altogether and prevent its functioning completely

+Irreversible Inhibitors

Also called poisons

For example: certain heavy metalsE.g., cadmium, lead, mercury

Retained in the body and lost slowly

Cyanide is a poison that prevents the activity of cytochrome C oxidase, an enzyme in the electron transport chain in the cell. It therefore inhibits ATP production and cellular respiration.

Cytochrome c oxidase

+Why are enzymes so tightly regulated by co-factors and inhibitors?

+Control of Metabolism Biochemical reactions are controlled in part by the specificity of

substrate biding, but the human body could not function if all enzymes were present together and all operating maximally with no regulation.

There would be biochemical chaos with substances being synthesized and degraded at the same time.

Instead, the body tightly regulates enzymes through metabolic pathways and by controlling specific enzymes within a pathway.

This approach allows an entire pathway to be turned on or off by simply regulating one or a few enzymes.

Metabolic pathways can also be regulated by switching specific genes on or off.

+

Enzymes play a critical role in everyday life. Many heritable genetic disorders occur because there is a deficiency or total absence of one or more enzymes.

Other disease conditions (e.g., cancer) result because there is an excessive activity of one or more enzymes.

Routine medical tests monitor the activity of enzymes in the blood, and many of the prescription drugs (e.g., penicillin,) exert their effects through interactions with enzymes.

Enzymes and their inhibitors can be important tools in medicine, agriculture, and food science.

Why is it important to know how enzymes are regulated?

Test study tip:

Create a concept map that summarizes the regulation of enzyme activity

Include the following terms:temperature Active site Co-factors

pH Enzyme inhibitors

Co-enzymes

Enzyme concentration

Competitive inhibitor

Allosteric inhibitor

Substrate concentration

Non-competitive inhibitor

Irreversible inhibitors

denature Inhibitor site

Enzyme reation rates

Reversible inhibitors

+ sbi4u biochemistry ms. manning enzymes. 1. what are enzymes and what is their role in normal...

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