Italics = extra credit work
What are we going to learn?
How enzymes work and their role in the digestive system
Enzyme Envy
Please read through the information below and then answer the questions:
Chemical reactions in most organisms take place within a fairly narrow range of
temperatures. These temperatures are not high enough to supply enough energy for
a reaction to occur. So how do organisms carry out the multitude of complex
chemical reactions we call metabolism? .
ENZYMES!!!
Enzymes are specialized proteins that lower the
energy needed for a reaction to start. This means
enzymes act as biological catalysts (speeding up
chemical reactions). In these reactions Enzymes
are not used up and therefore can be reused
many times.
https://www.citelighter.com/science/environment/kno
wledgecards/enzyme-influence-on-environment
Enzymes are large complex proteins (made of amino acids) have an active site. The
active site is the place on the protein where only certain molecules (we call these
substrate) can fit (bind) - see picture above of the catalase enzyme breaking up
H2O2
How do enzymes work?
When the Enzyme and Substrate are
together this is called the enzymes
substrate complex and its unique
structure causes a reduction in the
activation energy (energy required
to start a chemical reaction).
Once the chemical reaction has
CATABOLISM - http://www.shmoop.com/energy-flowenzymes/enzymes.html
occurred the products (parts of the
substrate now separated) break away and leave the enzyme for another molecule to
attach.
Enzymes can build molecules - anabolism or they can break apart molecules –
catabolism.
Italics = extra credit work
What is the purpose of an enzyme?
What are we going to learn?
How enzymes work and their role in the digestive system
How does an enzymes do this?
What is the name for the area of the enzyme where only the specific substrate bind?
Give one example of where you think catabolism occurs in the human body.
Making an Enzyme Model
(Bring your spatial awareness and your scissors!)
Goal
To make a working model to show how an enzyme functions as a catalyst.
Your model should contain:
An enzyme (color 1)
Substrate (color 2 & 3)
Competitive inhibitor (color 4)
Non-competitive inhibitor (color 4)
Method
1. Make plan on a piece of paper.
2. Be original and creative and use the flexibility of the foam to illustrate the
properties of the enzyme.
3. When all pieces are drawn to scale transfer your patterns to the pieces of
foam.
4. Cut the pieces carefully and slowly with scissors. Try and make the pieces fit
as precisely as possible.
5. You should be able to identify the enzyme the active site, the substrate, the
competitive inhibitor and the non-competitive inhibitor.
Results and Discussions
1. Explain using diagrams how your model works
2. How is your model like the other models in your class?
3. How does it compare to real enzymes?
Italics = extra credit work
What are we going to learn?
How enzymes work and their role in the digestive system
The Human Digestive System
The human body is composed of millions of cells that need to carry out chemical
reactions to survive. For these chemical reactions (e.g. respiration, digestion,
detoxification) enzymes are the catalysts and the body also needs the nutrients,
water and oxygen to use in these chemical reactions. These come from the food we
eat and that makes the magical journey through the alimentary canal. Using the
information in the table fill in the blanks in the paragraph below:
Site of digestion
Mouth
Stomach
Small intestine
Secretion
Saliva
Gastric Juice
Bile from the liver
Enzyme
Amylase
Pepsin
NONE
Action
Starch to maltose
Proteins to polypeptides
Breaks down fats to small droplets
Pancreatic juice
from pancreas
Amylase,
Trypsin,
Lipase
Starch to maltose
Poly peptide to peptide
Fats to fatty acids and glycerol
Maltase,
Sucrase,
Lactase,
Erpesin,
Lipase
Mouth – S_______________ containing amylase.
This breaks down starch into g_____________
Intestinal juice
from intestinal
glands
Stomach – gastric acid (HCl) containing an
e________________ called pepsin. This breaks
down protein to P__________________
Small Intestine (produced from the pancreas
and the small intestine itself.) – Amylase which
breaks down s_____________, lipase which breaks
down l___________ and t___________ which begins
the break down of polypeptides. There are
further enzymes shown below.
Once the nutrients have been processed by the
digestion and absorbed in v__________ of the
s_______ i___________ into the blood. The blood
then travels directly to the l________ so that any
toxins can be processed.
Maltose to glucose
Sucrose to parts
Lactose to parts
Peptide to amino acids
Fat to fatty acids and glycerol
Italics = extra credit work
What are we going to learn?
How enzymes work and their role in the digestive system
Method
You are going to complete one of the following procedures below depending on the
letter you are give: A – protein and B – fat or C – carbohydrate. You will then be
sharing your results from the other group who have completed the different
method/s.
Test
tube
(A)1
Contents
(A)2
Protein, pepsin and biuret
(B)3
Litmus-milk solution
(B)4
Litmus-milk and lipase solution
(C)5
Starch and iodine
(C)6
Starch, amylase and iodine
(C)7
Starch, amylase and Benedicts
(C)8
Glucose and Benedicts
Observations
Protein and biuret
Results and Discussions
1. Compare and contrast test tube 1 & 2. Describe the evidence, if any, that
digestion of protein occurred using pepsin.
2. The pepsin was prepared in weak HCl, why was this?
3. Compare and contrast test tubes 3 & 4, is there any evidence that there is
digestion of butterfat using lipase?
4. Compare test tubes 5 & 6, explain what you are seeing using close
observations and based on the enzyme amylase.
5. What do you see in test tube 7, what do you think this means about Benedicts
reagent and glucose?
6. Describe what is happening in the test tubes 2, 4 , 6 and 7 and relate them to
a specific part of the digestive system.
Italics = extra credit work
What are we going to learn?
How enzymes work and their role in the digestive system
Things you should have got from this practical:
o Enzymes are complex proteins which catalyze reactions
o They can break up and make up molecules, by changing the energy
needed for the reaction
o They can be inhibited by other molecules with a similar shape or by ones
changing the shape of the enzyme
o Enzymes in the digestive system break down food
o There are a variety of different enzymes and they are specific to the
different types of biological molecule
o They also occur in specific places in the alimentary canal
[G]enes make enzymes, and enzymes control the rates of chemical
processes. Genes do not make “novelty seeking” or any other complex and
overt behavior. Predisposition via a long chain of complex chemical reactions,
mediated through a more complex series of life's circumstances, does not equal
identification or even causation.
Stephen J Gould, The Lying Stones of Marrakech, 2001
Italics = extra credit work
What are we going to learn?
How enzymes work and their role in the digestive system
Why do enzymes sometimes not work?
(e.g. grapefruit , molecule furanocoumarin inhibiting drugs such as statins, ritilin
e.t.c)
Most enzymes can be inhibited (unable to act) by specific molecules that interfere
with the binding site of the substrate (active site). This can happen one of two ways:
Competitive inhibition
Non-competitive inhibition
Write a paragraph explaining what is happening in the diagram below.
Normal Enzyme Action
Competitive Inhibition
Non-competitive inhibition