Tutoring today at 3:15Retakes starting tomorrow at 2:45

Do-Now1.) Name three chemical reactions taking place in your body right now.

INB Pg 28 CHAPTER 3: ENZYMES

Enzymes are protein molecules that act as biological catalysts Catalyst: molecule that speeds up a chemical

reaction and remains unchanged after rxnEnzymes usually end in –aseVirtually every metabolic rxn is catalyzed by

an enzyme

ENZYMES

Globular proteins Precise 3D shape Multiple chains Hydrophilic R groups on outside = water soluble

Active site: region on an enzyme to which another molecule/molecules- called a substrate- can bind

ENZYMES

Idea that enzyme has a particular shape to which the substrate fits exactly Substrate=key. Held in place by temporary bonds Enzyme=lock

LOCK AND KEY HYPOTHESIS

Each type of enzyme will act on only one type of substrate moleculeShape of active site will only allow one shape to fit

Enzyme is said to be specific for substrate

LOCK AND KEY HYPOTHESIS

Modified the lock and key hypothesis in 1959 New evidence suggested that enzymes are more flexible

than is suggested by a rigid lock and key Basically same as lock and key, but adds the idea that the

enzyme, and sometimes substrate, changes shape slightly as substrate enters enzyme

INDUCED FIT HYPOTHESIS

Ensures a more perfect fitMakes catalysis more efficienthttp://www.youtube.com/watch?v=z8lG8X9Zv

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INDUCED FIT HYPOTHESIS

An enzyme may catalyze a reaction in which it joins together two peptides

An enzyme may catalyze a reaction in which the substrate molecule is split into two or more molecules

CATALYSIS

Enzyme-product complex is briefly formed before the release of products

Interaction between the R groups of the enzyme and the atoms of the substrate can break, or encourage formation of, bonds in the substrate molecule, forming products

When the rxn is complete, the products leave the active site Enzyme is unchanged and ready to accept another

substrate Rate of rxn is extremely rapid

CATALYSIS

Found in tears, saliva, and other secretions. Breaks the polysaccharide chains in the cell walls of bacteria

http://www.youtube.com/watch?v=QXIe0jDTlT4

LYSOZYME

As catalysts, enzymes increase the rate at which chemical reactions occur

Most of the rxns in living things would be too slow w/o an enzyme to sustain life

ENZYMES

Energy needed to start reaction = activation energy Enzymes work by lowering activation energy

CHEMICAL REACTIONS

Increase concentration of substrateIncrease energy of reactants (heating)

Ex: Benedict’s testMost rxns occur at temps higher than our body temp, which is why enzymes are necessary

OTHER WAYS TO INCREASE RXN RATE

WOD FORTHRIGHT(FORTH rite) adv./n. directly forward; without hesitation; a straight path

Whenever I want a FORTHRIGHT opinion, I always ask my two-year-old son.

The boss asked everyone to be FORTHRIGHT at the company meeting.

When Kathy asked Mark if her dress made her look fat, she wasn’t expecting his answer to be so FORTHRIGHT.

Compare and contrast the lock and key hypothesis with the induced fit

hypothesis.

DO NOW 12/2

When enzyme and substrate are first mixed, there are a large number of substrate molecules

At any moment, virtually every enzyme molecule has a substrate in its active site

THE COURSE OF A REACTION

Initially, the rate at which a reaction occurs will depend only on how many enzyme molecules there are and the speed at which the enzyme can convert substrate into product

However, as more substrate is converted to product, there are fewer and fewer substrate molecules, which slows down the rate of reaction

THE COURSE OF A REACTION

THE COURSE OF A REACTION

Directly proportional to reaction rate As we increase the

concentration of an enzyme, we have more active sites available for the substrate.

As long as there is plenty of substrate available, the initial rate of reaction increases linearly with enzyme concentration

THE EFFECT OF ENZYME CONCENTRATION

As concentration of substrate increases, the initial rate also increases

If we continue increasing substrate concentration, it will eventually max out because there are no more available active sites If more substrate is added,

the enzyme simply cannot work faster. The enzyme is working at its maximum possible rate, known as Vmax (V=velocity)

THE EFFECT OF SUBSTRATE CONCENTRATION

Low temp=low particle movement. Substrate move very slowly and will not often collide with the active site

As temp increases, substrates move faster and collide with active site more. Reaction rate increases

At a certain temperature (specific for diff. enzymes), hydrogen bonds begin to break in the enzyme (remember, it is a protein) and the enzyme will denature ( loose its structure and function)

TEMPERATURE AND ENZYME ACTIVITY

Denaturing of an enzyme is often irreversibleSubstrate cannot fit into denatured active sites, so no

activity takes placeThe temperature at which an enzyme catalyzes a

reaction at the maximum rate is called the optimum temperature

TEMPERATURE AND ENZYME ACTIVITY

Proteases (enzymes that break down proteins) are used in biological washing powders. How would a protease remove a blood stain on

clothes? Most biological washing powders are recommended

for use at low washing temperature. Why is this?

CHECK YOUR UNDERSTANDING

Hemoglobin is the colored pigment that causes blood stains. Protein-digesting enzymes hydrolyze hemoglobin to amino acids, which are colorless. They are also soluble, so will wash away in water.

Many protein-digesting enzymes have an optimum temperature of around 40 °C. If the temperature of a reaction is too high, the enzyme will denature.

CHECK YOUR UNDERSTANDING

pH is a measure of hydrogen ions in solution. The lower the pH, the higher the hydrogen ion solution.

Hydrogen can interact with R groups of amino acids which affects bonding in amino acids, which can change the structure (and function) of an enzyme

Enzymes work best under specific pH ranges.

PH AND ENZYME ACTIVITY

Page 64 #2, #6, #7, #9Quiz on enzymes (covered up to today) next class

HOMEWORK