Enzymes
What are enzymes and what do they do?
§ Enzymes are proteins that function as
biological catalysts.
§ This means they make a chemical reaction
faster and/or lower the activation energy
needed for a reaction
§ Examples of these reactions include digestive
reactions that break down large food
molecules into smaller, soluble nutrients
8 March 2023 What are cells? 1
How do enzymes work?
How do enzymes catalyse reactions?
§ Enzymes work using the ‘lock and
key’ model
§ This is where the active site of the
enzyme must be a complimentary
shape to the substrate it binds to
§ Once they bind, they become an
enzyme-substrate complex.
§ Then, the products are formed
§ Only one substrate can fit into each
enzyme, so they are specific
8 March 2023 What are cells? 2
What enzymes are there?
Which enzymes do you need to know?
§ You need to know the three major
digestive enzymes that we use to break
down our food.
§ This process is really important, because
molecules like protein, starch and lipids
can not be absorbed as they are large
and insoluble.
§ Therefore, enzymes in our alimentary
canal break down these molecules into
smaller and soluble nutrients, which can
be absorbed
8 March 2023 What are cells? 3
What enzymes are there?
Which enzymes do you need to know?
§ The first enzyme is amylase. It breaks down
starch into simpler sugars. More
specifically, it breaks it into maltose. (There
is a maltase enzymes that breaks this down
into glucose). Amylase is produced in the
salivary glands, small intestine and the
pancreas.
§ Lipase breaks down lipids into one glycerol
and three fatty acids each. It is produced in
the pancreas, small intestine and
pancreas.
§ Proteases break down proteins into amino
acids. Proteases are produced in the
stomach, pancreas and small intestine.
8 March 2023 What are cells? 4
What can affect enzyme activity?
How does temperature effect enzyme activity?
§ Anyone know how temperature affects
enzyme activity?
§ At higher temperatures, the enzyme and
substrate particles have more kinetic
energy as they move and vibrate more, so
there will be more successful collisions
and the reaction will be faster.
§ However, if the temperature gets too high, it
can change the shape of the enzyme’s
active site, making it denatured. This
means the substrate is no longer a
complimentary shape and can no longer fit.
8 March 2023 What are cells? 5
What can affect enzyme activity?
How does pH effect enzyme activity?
§ Anyone know how pH affects enzymes
activity?
§ Each type of enzyme has an optimum pH,
which is the pH it works best at and gives the
highest rate of reaction.
§ If the pH strays too far from the optimum
(too high or too low), this can also change
the shape of the enzyme’s active site and
make it denatured. Again, this means the
substrate is no longer a complimentary
shape and it will no longer fit.
8 March 2023 What are cells? 6
How have we adapted for digestion?
How have we adapted for digestion?
§ The stomach is full of hydrochloric acid,
around pH 2. This is because the protease
that works in the stomach, called pepsin, has
an optimum pH of 2.
§ However, the protease in the small intestine,
trypsin, has an optimum pH of 7. This is
why bile, an alkali, is produced by the liver
and secreted into the small intestine to
neutralize the stomach acid.
§ Also never forget, the small intestine has lots
of villi to increase the surface area for very
fast absorption of these nutrients
8 March 2023 What are cells? 7
Specific Enzymes
What specific enzymes do humans have?
§ Pepsin is a protease found in the stomach
that digests protein into amino acids. It’s
optimum pH is pH 2 since the stomach
contain hydrochloric acid
§ Trypsin is another protease which also
digests protein into amino acids but this time
found in the small intestine, so the optimum
pH is 8
§ Maltase breaks down maltose into glucose in
the small intestine. (Maltose is produced
when amylase breaks down starch)
8 March 2023 What are cells? 8
One more use for enzymes
Are enzymes just used for digestion?
§ Enzymes are not just used for digestion
§ There is pretty much one enzyme for every
chemical reaction that happens in your body
(which is a lot)
§ One example you need to know are the
enzymes in sperm cells.
§ Sperm cells have an organelle in the head
called an acrosome which contains
enzymes to break down the wall of the
egg.
8 March 2023 What are cells? 9
