enzymes and nucleic acids recap-as biology [jm]

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ENZYMES 1 Jorge Melo

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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

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Page 1: Enzymes and Nucleic acids recap-AS Biology [JM]

ENZYMES 1

Jorge Melo

Page 2: Enzymes and Nucleic acids recap-AS Biology [JM]

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)

Page 3: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 4: Enzymes and Nucleic acids recap-AS Biology [JM]

DNA Double helix

Antiparallel (5’-3’) (3’-5’)

Complementary rule

Chargaff’s rule

A-T C-G

Hydrogen bonds

Page 5: Enzymes and Nucleic acids recap-AS Biology [JM]

DNA vs RNA The sugars

Uracil instead of thymine

RNA –usually single stranded

Page 6: Enzymes and Nucleic acids recap-AS Biology [JM]
Page 7: Enzymes and Nucleic acids recap-AS Biology [JM]

RNA mRNA

tRNA rRNA

Page 8: Enzymes and Nucleic acids recap-AS Biology [JM]

RNA- recap

DNA double helix unwind (helicase)

RNA polymerase

Ligase

Page 9: Enzymes and Nucleic acids recap-AS Biology [JM]

Nucleic acids recap

Helicase

RNA polymerase

Ligase

tRNA

Transcription

Translation

Page 10: Enzymes and Nucleic acids recap-AS Biology [JM]
Page 11: Enzymes and Nucleic acids recap-AS Biology [JM]

Gene

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

Stands for:Ribonucleic acid

Page 12: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 13: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 14: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 15: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 16: Enzymes and Nucleic acids recap-AS Biology [JM]

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)

Page 17: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 18: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 19: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 20: Enzymes and Nucleic acids recap-AS Biology [JM]

Enzyme

Example of a reaction that you already know:

Hydrolysis Condensation

Enzyme Enzyme

Page 21: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 22: Enzymes and Nucleic acids recap-AS Biology [JM]

Enzyme

Tertiary structure

Page 23: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 24: Enzymes and Nucleic acids recap-AS Biology [JM]

Properties of Enzymes

Specific.

Not used up in reactions.

Combine to form enzyme/substrate complexes.

Only small amount of enzyme needed

Page 25: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 26: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 27: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 28: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 29: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 30: Enzymes and Nucleic acids recap-AS Biology [JM]

Names of Enzymes

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

Sucrase.

Lipase.

Protease.

Page 31: Enzymes and Nucleic acids recap-AS Biology [JM]

Task1

Page 32: Enzymes and Nucleic acids recap-AS Biology [JM]

How enzymes work

There are two models that explain how enzymes work:

1. Lock and Key theory

2. Induced fit theory

Page 33: Enzymes and Nucleic acids recap-AS Biology [JM]

Lock and Key Theory

Enzyme

SubstrateEnzyme Substrate complex

Products

Enzyme

Activation site

Page 34: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 35: Enzymes and Nucleic acids recap-AS Biology [JM]
Page 36: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 37: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 38: Enzymes and Nucleic acids recap-AS Biology [JM]

The Lock and Key Theory

Page 39: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Substrate

EnzymeProducts

Enzyme

Page 40: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Enzyme

Substrates Enzyme

Product

Page 41: Enzymes and Nucleic acids recap-AS Biology [JM]

Induced fit theory

Page 42: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 43: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 44: Enzymes and Nucleic acids recap-AS Biology [JM]

Rate of Reaction

This means that there is greater chance of collisions.

The rate of reaction then increases.

Page 45: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 46: Enzymes and Nucleic acids recap-AS Biology [JM]

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.

Page 47: Enzymes and Nucleic acids recap-AS Biology [JM]
Page 48: Enzymes and Nucleic acids recap-AS Biology [JM]

Activation Energy

Page 49: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 50: Enzymes and Nucleic acids recap-AS Biology [JM]

Activity

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

Page 51: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 52: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 53: Enzymes and Nucleic acids recap-AS Biology [JM]

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

Page 54: Enzymes and Nucleic acids recap-AS Biology [JM]
Page 55: Enzymes and Nucleic acids recap-AS Biology [JM]

Task2

Page 56: Enzymes and Nucleic acids recap-AS Biology [JM]

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.