© Boardworks Ltd 20091 of 6 Warm Up What is a chemical reaction? What are products? What are...

© Boardworks Ltd 20091 of 6

Warm Up• What is a chemical reaction?• What are products?• What are reactants?• Describe the building of a monomer into a polymer as a chemical reaction.


Chemical Reactions and Energy

• Chemical reactions happen when bonds are broken and/or formed.

• Reactants (what you start with)• Products (what you end with)• Chemical Reaction:

Reactants Products

Na+ + Cl- NaCl(arrow points away from reactants and towards products)


Energy

• Energy (E)~ the ability to do work; – Kinetic energy~ energy of motion; – Potential energy~ stored energy

• Thermodynamics~ study of E transformations– 1st Law: conservation of energy;

• E can be transferred (from one thing to another) or transformed (go from PE to KE or KE to PE),

• E can not be created or destroyed

• quantity of E is constant, quality is not


Energy and Life

• Metabolism: All of the chemical processes in a living organism; managing the material and energy resources of the cell

• Catabolic pathways: process that break things down (hydrolysis) for example: cellular respiration; releases energy

• Anabolic pathways: building process such as (dehydration synthesis) for example: protein synthesis; photosynthesis; consumes energy


Free Energy

• Free energy: E that is available to do work • Exergonic (Exothermic)reaction: net release of free E to surrounding

(catabolic processes) We get energy from breaking down food.• Endergonic (Endothermic) reaction: absorbs free E from surroundings

(anabolic processes) We need energy to build us (proteins)


How is ATP used for energy?

• When we break down glucose (cellular respiration), the energy that was stored in the glucose is now stored in ATP.

• How is the ATP used to do work?• The process is called Energy Coupling: use of exergonic

process to drive an endergonic one• Adenosine triphosphate

– Water is added to ATP to break off the last phosphate group (hydrolysis): This releases free E

ATP + H2O ADP + P + energy


The ATP Cycle


Enzymes

• What are Enzymes?• Enzymes are organic catalysts. Catalysts speed up chemical reactions.

How do they speed up chemical reactions?• Lower the activation energy of a reaction (the energy needed for the reaction to happen)

• Do not change the reaction – only speed up a reaction that would have occurred anyway.


What does a Chemical Reaction look like

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition%20state.swf

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/transition%20state.swf


How do enzymes speed up reactions?

Enzymes speed up reactions by lowering the activation energy (Ea) of a reaction. The activation energy is the energy needed to start a reaction.

Different reactions have different activation energies.

Draw the following graph:

reaction (time)

ener

gy

(kJ)

Ea with enzyme

Ea without enzyme


http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/prox-orien.swf


What are enzymes made of?

Enzymes are protein molecules, and so are made up of amino acids. Most enzymes contain between 100 and 1,000 amino acids.

These amino acids are joined together in a long chain, which is folded to produce a unique 3D structure.


Why is shape important?

The shape of an enzyme is very important because it has a direct effect on how it catalyzes a reaction.

An enzyme’s shape is determined by the sequence of amino acids in its structure, and the bonds which form between the atoms of those molecules.

Why do enzymes have different shapes?

Different types of enzymes have different shapes and functions because the order and type of amino acids in their structure is different.


Why are enzymes so specific?

Enzymes are very specific about which reactions they catalyze. Only molecules with exactly the right shape will bind to the enzyme and react. These are the reactant, or substrate, molecules.

The part of the enzyme to which the reactant binds is called the active site.

This is a very specific shape and the most important part of the enzyme.


What happens at the active site?

Lock and Key Model:In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key.

enzyme

substrate

+enzyme-

substrate-complex

↔products

enzyme

+↔

+ ↔ ↔ +


The lock and key model


Enzymes: true or false?


• Over the next several days you will be completing lab activities to learn about the different properties of enzymes.• Homework:• Read the lab, get it written into your notebook, include prelab questions, and describe your procedures.


Factors affecting enzymes

If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes.

normal denatured

heat

pH

This affects the shape of the active site and means that the enzyme will no longer work.

When this happens the enzyme is denatured.


Enzymes and temperature


Enzymes

• Catalytic proteins: change the rate of reactions w/o being consumed

• Free E of activation (activation E): the E required to break bonds

• Substrate: enzyme reactant• Active site: pocket or groove on enzyme that

binds to substrate• Induced fit model binding of substrate changes

shape of the active site so that the substrate can bind

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/enzyme.swf

http://www.stolaf.edu/people/giannini/flashanimat/enzymes/enzyme.swf


Factors affecting enzymes

The rate of enzyme-catalyzed reactions depends on several factors. What are some of these?

All enzymes work best at only one particular temperature and pH: this is called the optimum.

Factors that affect the rate of a reaction include: substrate concentration temperature

Different enzymes have different optimum temperatures and pH values.

pH enzyme concentration

surface area pressure.

© Boardworks Ltd 20091 of 6 Warm Up What is a chemical reaction? What are products? What are...

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