Connect
•How many of you have heard “Chew your food”?
•Why is it important?
•What does your body use to assist in digestion?
•Do you know someone who is lactose-intolerant?
•What does that mean?
•What do they have to do?
•What causes it?
•Why can’t I use my truck key to get into my
classroom, and vice versa?
Enzymes
• Biological processes such as digestion, synthesis,
respiration and photosynthesis are made possible in
living things by enzymes.
Enzymes speed up the rate of reactions in living things.
Without enzymes, the processes that keep us alive
would not occur at a fast enough rate.
For example,
digestion of our
food would not
occur quickly
enough for our cells
to receive food.
Luckily, enzymes
are added to our
food as it moves
through the
digestive tract.
These enzymes
help make our food
small enough to fit
into our cells.
• Enzymes are catalysts, substances that
speed up the rate of a chemical reaction
without themselves being changed or used
up during the reaction.
• Enzymes are capable of carrying out the
same function over and over.
• Enzymes, like other molecules (hormones,
antibodies, receptors on cell membranes) have
specific shapes that determine how they
function.
• Enzymes are chain-like protein molecules that
are folded into precise shapes.
What happens if a protein loses its shape?
• Some molecules called substrates match precisely with
the shape of certain enzymes, others don’t fit.
For example, the enzyme pepsin in your stomach acts on
protein you eat to digest it. Pepsin is not effective in
digesting fat. This means that enzymes are specific.
• Enzymes help carry out many reactions in the
body such as digestion and synthesis.
• Synthesis creates a larger product than the
substrates, with the help of enzymes.
• Digestion breaks large molecules into
smaller ones, with the help of enzymes.
Chunk!
Study this diagram…
Try to label all the pieces…
• How can you always identify the enzyme?
• If the end molecule is larger, is it the
process of synthesis or digestion?
• What is the job of enzymes, in general?
Chunk continues..
•
•
•
•
•
Explain the role of enzymes in digestion.
What is another name for enzymes?
Are enzymes used up in the reaction?
How do enzymes work?
What type of organic molecules are
enzymes?
• Name some other molecules that function
by shape.
Enzymes Are Picky
• Like you and me, enzymes only function
well under the best of environmental
conditions. Each enzyme has set of
conditions that are best for it to work.
These conditions are called optimal.
1. Temperature
• Most enzymes have an optimum
temperature at which they function most
effectively bc enzymes and substrates
move faster at the optimum temperature,
increasing the reaction rate.
• Higher temperatures however cause the
rate to decrease bc the enzymes change
shape or break apart
2. pH
• Most enzymes have an optimum pH of
around 7 at which they function most
effectively
• Enzymes that work in specific locations
with other pH values tend to have the
optimum pH values that correspond with
their working environment
Chunk
• Why are enzymes “picky”? (Use these terms: lock and
key, substrate, active site, specific)
• What does “optimum” mean, in terms of enzyme action?
• How does temperature affect enzyme rate? Why?
• What do very high temps do to enzymes?
• What is body temp in degrees Celsius?
• What is pH?
• What is the pH of strong acids…weak acids?
• What is the pH of strong bases…weak bases?
• What is neutral pH?
• What is the optimum pH for most enzymes?
• What does the term “enzyme specificity” mean?
Just for Fun!
What could the
rabbit use to
increase the
reaction rate of the
turtle?