Transcript IB SR Q1 Exam Review-2012

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:
 When
denaturation
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:
 The
active site
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 enzymesubstrate 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 yaxis
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; yaxis: 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 answer
 1 DBQ
