IB BIOLOGY QUARTER 1 EXAM REVIEW

Topic 3.6 – Enzymes

GUIDELINES Get into a group of 4 Designate a recorder (you may rotate) In order to get points, your answer must be

written on the dry erase board When time is called, each group will raise

their answer/board up If your answer is correct, award yourself a

point (we’re on the honor policy ) I will take away points for disruptive behavior 1 minute per question

TOPIC 3.6 – ENZYMES Why are enzymes called biological

catalysts?

Because they speed up the rate of a reaction.

Reactants in the presence of an enzyme will form products at a faster rate than without an enzyme

TOPIC 3.6 – ENZYMES Which macromolecule group do

enzymes belong to?

Proteins Made up of amino acids

TOPIC 3.6 – ENZYMES What do we call the reactant to which

the enzyme binds?

Substrate

TOPIC 3.6 – ENZYMES True or false: The shape of an enzyme

is very specific.

True

TOPIC 3.6 – ENZYMES Define: denaturation

When the specific shape the of the enzyme is changed, which alters the shape of the active site

The substrate and enzyme can no longer bond

Rate of reaction decreases

TOPIC 3.6 – ENZYMES Outline the lock and key hypothesis

used for enzyme-substrate activity.

Lock = enzyme’s active site Key = substrate Because the shape of the enzyme is

very specific, only one key (substrate will fit)

Enzymes and substrate are specific for each other

TOPIC 3.6 – ENZYMES Define: active site

The area on an enzyme that binds to the substrate

Specific area responsible for the activity of all enzymes/proteins

TOPIC 3.6 – ENZYMES Outline the induced fit model for

enzyme-substrate activity.

The active site on the enzyme will slightly change its shape to form a tight bond with the substrate

TOPIC 3.6 – ENZYMES True or false: An enzyme can force a

reaction to take place.

False Enzymes cannot force reactions to

occur that would not otherwise take place

Enzymes only speed up the rate of reaction.

TOPIC 3.6 – ENZYMES How do enzymes speed up the rate of

reaction (think about activation energy)

The activation energy is the energy needed to start a reaction

Enzymes lower the activation energy Reactants are broken down to products

at a faster rate

TOPIC 3.6 – ENZYMES Why are small amounts of enzyme

effective in catalyzing a reaction?

Enzymes are reusable Once a substrate is converted to a

product, the active site on the enzyme is available for another substrate to bind

An enzyme can function as a catalyst many, many times

TOPIC 3.6 – ENZYMES Identify the three factors that can

effect enzyme activity.

Temperature pH Substrate concentration

TOPIC 3.6 – ENZYMES Identify the two factors that can cause

an enzyme to denature.

pH Temperature

TOPIC 3.6 – ENZYMES Draw a graph showing the effects of temperature

on enzyme activity. Be sure to include proper axis labels. Explain the effects of temperature on enzyme activity.

Graph: bell curve; increasing temp. on x-axis, rate of reaction on y-axis

At lower temperatures, molecules move slower less collisions between enzyme and substrate

As temperature increases, molecular movement increases more collisions

Peak of bell curve = optimal temperature After optimal temperature = denaturation

TOPIC 3.6 – ENZYMES Draw a graph showing the effects of pH on enzyme

activity. Be sure to include proper axis labels. Explain the effects of pH on enzyme activity.

Graph: bell curve; pH on x-axis, rate of reaction on y-axis

Too acidic = large number of hydrogen ions (H+) can bond to negative charges of the enzyme or substrate

Too basic = large number of hydroxide ions (OH-) can bond to positive charges of the enzyme or substrate

In either case, bonding between the enzyme and substrate is disrupted

Enzyme becomes less efficient, possibly inactive in extreme situations (denatured)

TOPIC 3.6 – ENZYMES True or false: All enzymes work best at

the same pH level

False – some prefer acidic environments (think pepsin in your stomach); some prefer neutral (think amylase in your mouth)

TOPIC 3.6 – ENZYMES Draw a graph showing the effects of substrate

concentration on enzyme activity. Be sure to include proper axis labels. Explain the effects of substrate concentration on enzyme activity.

Graph: linear increase in the beginning, followed by a plateau; x axis: increasing substrate concentration; y-axis: rate of reaction

As substrate concentration increases, so does rate of reaction because your have more substrate

There is a limit; as substrate out-numbers enzyme, the rate of reaction slows down because every enzyme molecule is working as fast as possible, so adding more substrate will not increase the reaction rate

TOPIC 3.6 – ENZYMES When comparing/discussing data, what

are important features you should include in your response?

Specific data Trends in data Units Objective terminology

TOPIC 3.6 – ENZYMES In the lab you just completed, identify:

the enzyme used and the substrate.

Pectinase Pectin

TOPIC 3.6 – ENZYMES Maltose, a disaccharide, is a sugar

used in the confectionary and brewing industries. Predict the name of the enzyme that breaks down maltose.

Maltase

TOPIC 3.6 – ENZYMES Just to recap …

If you haven’t figured it out yet, your quarter 1 exam covers IB topic 3.6 (enzymes)

Reflects papers 1 and 2 7 multiple choice 1 short answer1 DBQ