enzymes and nucleic acids recap-as biology [jm]

ENZYMES 1

Jorge Melo

DNA nucleotide recap

OO=P-O O

N

CH2

O

C1C4

C3 C2

5

Phosphate Group

Sugar(deoxyribose)

Nitrogenous base (A, G, C, or T)

DNA double helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

DNA Double helix

Antiparallel (5’-3’) (3’-5’)

Complementary rule

Chargaff’s rule

A-T C-G

Hydrogen bonds

DNA vs RNA The sugars

Uracil instead of thymine

RNA –usually single stranded

RNA mRNA

tRNA rRNA

RNA- recap

DNA double helix unwind (helicase)

RNA polymerase

Ligase

Nucleic acids recap

Helicase

RNA polymerase

Ligase

tRNA

Transcription

Translation

Gene

Name given to some stretches of DNA and RNA that encode for a peptide

Stands for:Ribonucleic acid

What am I? I am important to life

I am affected by temperature

I am a globular molecule

I am involved in biochemical reactions

I am involved in the breakdown of molecules

I am an Enzyme

Aims and objectives

Aim: explore and the structure and function of enzymes

Objectives: List the main properties of enzymes Explain the terms active site, specificity

and catalysts Discuss how enzyme activity is affected

by temperature and pH

Mind Map Enzymes: facts and functions

Enzymes: chemical structure

Enzymes: properties

Names of enzymes

How enzyme works (theories)

Activation energy and Rate of reaction

The effect of temperature and pH on the enzyme

Facts about enzymes Enzymes are chemicals that

control the reactions in cells.

They are the caretakers of cells and tissues.

They make sure that cell chemistry is kept in good shape.

Each one has a particular job to do.

Examples of enzyme functions

Clear the fat out the blood stream after a meal

Detection of glucose level in the body

Break down the alcohol in beer or wine (liver)

Enzymes

Thousands of chemical reactions take place in the body every second.

These make up the metabolism.

Enzymes control the metabolism by determining when and how chemical reactions take place.

Enzymes

Enzymes are catalysts that speed up the rate of metabolic reactions.

These reactions will take place without enzymes, but they would take years rather milliseconds.

Enzymes Which of the following reactions break

molecules down and which build molecules up?

A glycogen molecule formed from glucose molecules.

The digestion of starch to maltose.

Urea formed from ammonia and carbon dioxide.

Enzyme

Example of a reaction that you already know:

Hydrolysis Condensation

Enzyme Enzyme

Enzymes the Chemical Structure

globular proteins.

long chains of amino acids.

In a globular protein, the amino acid chain is folded and wound into a spherical or globular shape.

Enzyme

Tertiary structure

Enzymes the Chemical Structure

Specific three-dimension shape (tertiary structure)

This is Important: if it is altered , the enzyme cannot function

Three dimension shape is maintained by hydrogen bonds and ionic forces

Properties of Enzymes

Specific.

Not used up in reactions.

Combine to form enzyme/substrate complexes.

Only small amount of enzyme needed

Properties of Enzymes

Are fast acting – high turnover number.

Affected by temperature and pH.

Some only able to work if a cofactor is present.

Can be slowed down or stopped by inhibitors.

Specificity Each enzyme can only catalyse one

particular reaction.

This is because an enzyme can only react with a specific substrate molecule.

Amylase can only catalyse the hydrolysis of starch into smaller disaccharide maltose molecules.

This is because amylase can only react with starch molecules.

Properties of enzymes

An enzyme acts on a chemical known as a substrate and the new substance that is formed is the product

Substrate product

The name of the enzyme often comes from substituting or adding -ase in the name of the substrate

Enzyme

Names of Enzymes

The name of an enzyme comes from the particular substance on which it acts.

Lactase acts on the milk sugar lactose.

Amylase works on starch – proper name amylose.

Cellulase breaks down cellulose.

Enzymes and their substrates

Enzyme Substrate Reaction catalysed

Maltase Maltose Hydrolysis of maltose to glucose

Amylase Amylose Hydrolysis of starch to maltose

Alcohol dehydrogenase

Alcohol Removal of hydrogen from alcohol

DNA Ligase DNA Joining together 2 DNA strands

RNA polymerase Nucleotides that make RNA

Synthesis of mRNA to DNA molecule

Glycogen synthetase

Glucose Polymerisation of glucose into glycogen

ATPase ATP Synthesis or splitting of ATP

Names of Enzymes

Which substrate do you think each of these enzymes acts upon?

Sucrase.

Lipase.

Protease.

Task1

How enzymes work

There are two models that explain how enzymes work:

1. Lock and Key theory

2. Induced fit theory

Lock and Key Theory

Enzyme

SubstrateEnzyme Substrate complex

Products

Enzyme

Activation site

The Lock and Key Theory

This attempts to explain why enzymes are specific.

They are large molecules, usually much bigger than their substrates.

Only a relatively small part comes into contact with the substrate.

The Lock and Key Theory

This is called the active site.

Only 3-12 aa make the active site, but its shape is an exact fit for the substrate.

The substrate is the key that fits the enzymes lock.

Lock and Key Continued

The two molecules form a temporary structure called an enzyme/substrate complex

The products are formed at the active site

They then no longer fit and are repelled

The active site is then free to react with more substrate

The Lock and Key Theory

2 types of reactionCatabolic reaction: certain enzyme break a substrate down into two or more products

Substrate

EnzymeProducts

Enzyme

2 types of reactionAnabolic reaction: certain enzyme bond tow or more substrates together to assemble one product

Enzyme

Substrates Enzyme

Product

Induced fit theory

Induced fit theory The active site is a cavity of a particular

shape

Initially the active site is not the correct shape in which to fit the substrate

As the substrate approaches the active site, the site changes and this results in it being a perfect fit

After the reaction has taken place, and the products have gone, the active site returns to its normal shape

Rate of Reaction Most reactions in

cells would be very slow without enzymes.

The substrate may not be converted into the product unless it is given extra energy.

Heating the particles would increases their kinetic energy and they move about more quickly.

Rate of Reaction

This means that there is greater chance of collisions.

The rate of reaction then increases.

Activation EnergyThe energy needed to start a chemical reaction

It can be thought of as an energy barrier to get over before the reaction can get underway.This energy can be supplied in the form of heat.

But this is not practical in living systems.

Activation Energy By lowering the activation energy of a reaction,

the enzyme provides a different pathway for the reaction.

By lowering the activation energy, enzymes reduce the input of energy needed.

This allows reactions to take place at the at the lower temperatures found in the cells of organisms.

Activation Energy

Factors affecting enzyme activity

The factors that affect enzyme activity also affect the functions of the cell and ultimately the organism

enzymes are proteins and their functions is therefore altered by:

Temperature pH Substrate concentration Enzyme concentration Cofactors inhibitors

Activity

Work in pairs and think about how are the enzymes affected with the temperature and pH

Temperature High temp. reactions tend to take place faster

(more kinetic energy)

However if temp. is too high the enzyme may lose their shape Bonds that old the tertiary structure of the enzyme

molecule on shape tend to break When the active site of the enzyme loses its shape it

is no longer able to bond to the substrate Enzyme denatured Irreversible reaction

The temperature at which the enzyme works most rapidly is called optimum temperature

OT for plant enzymes 25 C

OT for Human body 37 and 40 C

OT some bacteria 80 C

Ph

Can have a direct effect on the bonding responsible for holding the enzyme molecule in its precise three-dimensional shape. If the active site is changed then enzyme action will be affected

Each enzyme has an optimum pH Extremes of pH can denature enzymes

and stop them from functioning as catalysts

Task2

Summary Six facts about enzymes Enzymes are globular proteins They reduce the activation energy needed for a

reaction to proceed and produce products Enzymes have a region called an active site.

The site is the "lock" into which a substrate "key" fits.

The enzyme then fits closely around the substrates. This is called induced fit.

Enzyme activity is affected by substrate type, temperature, pH and substrate concentration.