Aim 7E: How do enzymes control chemical
reactions?
1) What are enzymes made up of?
• Enzymes are made up of
proteins
• AKA: Organic Catalysts
a) Organic- contains carbon and
hydrogen
a) Catalysts- affect the rate of
chemical reactions
**enzymes are never used up or
changed so they can be reused**
2) How do enzymes function?
a) Substrate- molecule(s) that an
enzyme works on
b) Active Site- pocket or groove
where the chemical reaction
takes place (where substrate
meets enzyme)
c) Enzyme-Substrate Complex:
substrate temporarily binds to
active site (held in by hydrogen
or ionic bonds)
Short Video: How Enzymes Work
McGraw-Hill
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/a
nimation__how_enzymes_work.html
3) What are cofactors?
• Small molecules that bind with
enzymes and are necessary for
enzyme function
a) Inorganic- metal atoms
b) Organic- coenzymes (most
vitamins)
4) What is the Lock and Key Hypothesis?
• Enzymes are specific and will
only work on one type of
substrate
5) What is the Induced Fit Hypothesis?
• The enzyme changes shape to
enhance the ability of the
enzyme to catalyze the chemical
reaction
• The enzyme returns back to its
original shape after the reaction
occurs
6) How are enzymes named?
• Enzymes often end in “-ase”
a) Lipase- works on lipids
b) Protease- works on proteins
c) Maltase- works on maltose
7) What is activation energy (Ea)?
• The amount of energy
need to START a
chemical reaction
a) How do enzymes affect the activation energy of a
chemical reaction?
• Enzymes lower the activation energy needed for
a reaction to take place
8) What factors affect enzyme reactions?
a) Temperature- As the
temperature increases, the rate
of reactions increases then
decreases.
i.
Optimum Temperature- the
temperature at which the enzyme
works best
 98. 6 degrees Fahrenheit or 37
degrees Celsius
ii.
Denature- high temperature will
change the shape of the enzyme so
it does not fit anymore
8) What factors affect enzyme reactions?
b) pH- depends on where enzyme is
working in the body
 Amylase- breaks down starch in the
mouth (pH= 6.2 to 7)
 Pepsin- breaks down protein in the
stomach (pH= 1.5-2.2)
 Trypsin- breaks down protein in the
small intestines (pH= 8)
8) What factors affect enzyme reactions?
c) Enzyme concentration- as
more enzymes are added,
enzyme action increases and
then eventually levels off
8) What factors affect enzyme reactions?
d) Substrate concentration- as
more substrate is added,
enzyme action increases and
eventually levels off
Let’s Review!
1) What is an enzyme?
2) What are enzymes made of?
3) What is a substrate?
4) Can an enzyme work on any substance?
5) What letters do enzymes often end in?
6) What factors affect the rate of enzyme action?
•
Which chemical is classified as an enzyme?
1.
2.
3.
4.
galactose
lipid
protease
manganese dioxide
•
In enzyme controlled reactions, the role of certain
vitamins such as niacin is to act as
1.
2.
3.
4.
an enzyme
a substrate
a coenzyme
a polypeptide
•
Salivary amylase is an enzyme in humans
that breaks down starch. The optimum pH
for this reaction is 6.7. The rate of this
reaction would not be affected by
1.
2.
3.
4.
maintaining the pH of the reaction at 6.7
substrate concentration
enzyme concentration
decreasing the temperature of the reaction by
5 degrees C
•
Which statement best expresses
the information represented in the
graph shown?
1.
2.
3.
4.
The action of enzymes varies with
pH.
A pH of 7 provides the optimum
environment for digestive enzymes
Gastric juice is active at a pH
extending from 0 to 12.
Acids have a pH greater than 7.
•
Lipase, maltase, and protease are members of a group
of catalysts known as
1.
2.
3.
4.
hormones
carbohydrates
lipids
enzymes
•
The effect of temperature on the
relative rate of action of an
enzyme is represented in the
graph. The optimum temperature
for the action of this enzyme is
approximately
1.
2.
3.
4.
15 C
22 C
37 C
50 C
•
Here are of some stages of an
enzyme-controlled reaction . An
enzyme-substrate complex is
represented by diagram
1.
2.
3.
4.
A
B
C
D
•
The diagram below represents three steps in the
hydrolysis of a molecule of sucrose. In this
diagram, structure X is most likely
1.
2.
3.
4.
a molecule of oxygen
the end product
an organic catalyst
the substrate
•
The fact that amylase in the human small intestine works best at
normal body temperature suggests that
1.
2.
3.
4.
amylase is denatured at temperatures below 37 degrees C
amylase can function only in the small intestine
the lock-and-key model of enzyme action does not apply to amylase
the optimum temperature for amylase is 37 degrees C
•
Which statement best describes
the enzyme represented in the
graphs?
1. This enzyme works best at a
temperature of 35 C and a pH of 8.
2. This enzyme works best at a
temperature of 50 C and a pH of 12.
3. Temperature and pH have no
influence on the activity of this
enzyme.
4. This enzyme works best at a
temperature above 50 C and a pH
above 12
Use the chart below and your knowledge of the living
environment .
•
If enzyme C is functioning at 25°C
and a pH of 7, under which
conditions would the rate of enzyme
action probably increase?
1.
The temperature is decreased
to 22 C and the pH is kept the
same.
2. The temperature is kept the
same and the pH is decreased
to 6.
3. The temperature is increased to
44 C and the pH is kept the
same.
4.
The temperature is increased to
30 C and the pH is increased to
8.
•
At what temperature would enzyme
D most likely be denatured?
1. 15 C
2. 20 C
3.
25 C
4.
39 C
•
Letter A in chemical
reaction one most likely
represents
1.
2.
3.
4.
•
a substrate
a neurotransmitter
an organic catalyst
a hormone
Which substance most
likely represents letter C
in reaction two?
1.
2.
3.
4.
amylase
protease
sucrase
lipase
•
A student placed groups of
50 seeds in a variety of
temperatures ranging from 0
to 50 C. A difference in the
rate of germination
observed in the groups at
different temperatures was
most likely due to the effect
of temperature on
1. ammonia
2. acids
3. enzymes
4. cellulose
•
Using your knowledge of enzyme structure and function,
explain why a prolonged period of high fever is
dangerous to humans.