Chapter 6 (p. 97-105) and Chapter 20 (p. 375)
1. Demonstrate an understanding of the following terms: metabolism,
enzyme, substrate, coenzyme, activation energy. (p. 102-105)
2. Identify the source gland for thyroxin and relate the function of thyroxin to
metabolism. (p. 375)
3. Explain the “lock and key” model of enzymatic action. (p. 103)
4. Identify the role of vitamins in biochemical reactions. (p. 105)
5. Differentiate between the role of enzymes and coenzymes in biochemical
reactions (p. 105)
6. Apply knowledge of proteins to explain the effects on enzyme activity of
pH, temperature, substrate concentration, enzyme concentration,
competitive inhibitors, and heavy metals. (p. 104-105)
_____ Activation energy
_____ Active site
_____ Allosteric inhibitor
_____ Apoenzyme
_____ ATP energy
_____ Catalyst
_____ Co-enzyme
_____ Competitive inhibitor
_____ Concentration
_____ Dehydration synthesis
_____ Denature
_____ Endothermic
_____ Enzyme
_____ Enzyme-Substrate Complex
_____ Exothermic
_____ Functional protein
_____ Heavy metal ions
_____ Homeostasis
_____ Hydrogen carrier
_____ Hydrolysis
_____ Inhibitor
_____ Iodine
_____ Lock and key analogy
_____ Metabolism
_____ Optimum pH
_____ Optimum temperature
_____ Oxidize
_____ pH
_____ Structural protein
_____ Substrate
_____ Temperature
_____ Tertiary structure
_____ Thyroxin
_____ Vitamin
1. There are approximately 3,000 of enzymes that exist in our
body. Each of them with a specific function.
2. Enzymes help to promote metabolism, and help to catalyze
every reaction that occurs in the body (ie: replication,
transcription…).
3. Digestive enzymes also play a vital role in food digestion.
4. These enzymes act as sharp knives that cut up the complex
foods into smaller units so that it can be assimilated easily
into the blood stream.
5. The absorption will then enable our body to reassemble to
build new cells and every other molecule our bodies need.
•
Since the tight control of enzyme activity is essential for homeostasis,
any malfunction or mutation of a single critical enzyme can lead to a
genetic disease.
•
A lethal illness can be caused by the malfunction of just one type of
enzyme out of the thousands of types present in our bodies.
Example #1: PKU. http://ca.youtube.com/watch?v=KUJVujhHxPQ
Mutation in enzyme phenylalanine hydroxylase,
which helps to digest phenylalanine, results in
build-up of phenylalanine. This can lead to
mental retardation .
Can be controlled by a diet low in
phenylalanine.
Damage done is irreversible so early detection
is crucial.
Example #2: Mutations in genes coding for DNA repair enzymes.
Will cause cancer since the body is less able to repair mutations in the
genome.
This causes a slow accumulation of
mutations and results in the
development of many types of cancer
in the sufferer.
An enzyme is a catalyst (a substance that speeds up a
reaction without being consumed).
Enzymes are proteins and are reusable.
They work in low concentrations and speed up the
reaction rate.
Amylase
Starch
Lipase
Lipids
Glucose
Fatty Acids and Glycerol
Protease
Proteins
Amino Acids
Enzymes allow reactions to proceed at lower temperatures
than they would normally occur.
The reactant(s) that an enzyme acts upon is known as the
substrate(s).
Enzymes work by forming a very temporary complex with the
substrate. This is called the ENZYME SUBSTRATE COMPLEX.
Enzymes are large
globular proteins with
very specific 3-D
shapes (tertiary
structure).
Enzymes have grooves
(or pockets), which may
contain chemically
functional groups.
These areas are called
active sites and this is
where the substrate
attaches.
Specific groove shapes and chemical groups in an active site
means that enzymes can only bond with one specific
substrate or reactant.
When the substrate and enzyme join together, the shape of the
enzyme changes, which makes it more reactive.
This is called INDUCED FIT
http://www.phschool.com/science/biology_place
/labbench/lab2/images/indfit.gif
Many enzymes are made up of 2 pieces.
1) The APOENZYME – the protein portion (inactive)
2) The CO-ENZYME – a non-protein portion
When these join together, the enzyme becomes active and
the substrate will now ‘fit’ into the active site..
Co-enzymes usually fit into the ALLOSTERIC site, which
changes the shape of the active site so the substrate can “fit.”
The co-enzymes are often large molecules that the body cannot
make on its own.
Most co-enzymes are VITAMINS which we get from food or
supplements.
A typical balanced diet gives you
all the vitamins you need, so there
is little or no benefit from taking
additional vitamin pills.
The main exception to this is the
vitamin folate, or folic acid, which
is mainly found in dark green
vegetables like spinach or collard
greens.
Not surprisingly, this is often deficient in the diet, and so in
January 1999 the US government required companies making
basic products like flour to add folate to the flour.
So now when you eat bread, or pizza, or other common foods
you are getting the folate your body needs. So pizza really is
health food!
The active site of an enzyme is not an exact perfect fit to
the substrate.
When the substrate attaches to the enzyme, this causes
stress in the substrate, which will cause:
1.A substrate to break
apart (in a hydrolysis
reaction).
Another word for this is
CATABOLISM:
breaking big molecules
in to smaller ones.
2. Two substrates to form a bond (in a synthetic reaction).
Another word for this is ANABOLISM: putting small
molecules together to make bigger ones.
•Definition: Metabolism is
the constantly occurring
chemical reactions that
take place in a cell.
•These chemical reactions
occur in organized
sequences from
reactants to end
products with the help of
enzymes.
•This organized sequence
of reactions is known as a
metabolic pathway.
REACTANT
Intermediate
products
PRODUCT
Usually, heat is used to speed up chemical reactions by
increasing the number of collisions that occur between
reactants.
Excessive heat, however,
destroys the tertiary structure
of protein (denatures it).
Therefore, heat cannot be
used to speed up reactions
within living organisms.
Enzymes operate by lowering the energy of activation
needed for a reaction to occur.
Enzymes act as a CATALYST and are not consumed in a
reaction. This means that they can be used over and over
again.
1. Concentration: The amount of enzyme and/or
substrate available to react can affect enzyme activity.
The reaction speeds up as the [substrates] increases, and it
levels out when the enzymes are working at the maximum
speed (saturation).
What can you do
to cause an
increase in
reaction rate?
Add enzymes!
The reaction speeds up as you increase the [enzyme], and
slows down as the substrate has all been turned into
product.
What can you do
to cause an
increase in
reaction rate?
Add substrate!
Enzyme Concentration
2. Temperature: As temperature rises, the reaction rate will
increase as the enzymes and substrates bump into each
other more often (kinetic molecular theory).
At a certain point, the rate of these collisions will be at the
fastest rate. This is the OPTIMUM TEMPERATURE.
However, once you get above
the optimum temperature, the
enzyme becomes denatured
(changes shape) and no
longer functions properly.
Most of our enzymes have an optimal temperature of 37oC
(body temperature).
The antarctic fish trematomus lives under the ice in the antactic ocean. It
has large, bulging eyes to collect as much light as possible from the dim sea
underneath the ice.
The enzymes from these fish are so well adapted to cold environments that
they denature (and the fish dies) if the temperature reaches only 5oC.
As well as having enzymes that are adapted to the cold, these fish also
have special glycoproteins that act as an antifreeze in their blood. This
natural antifreeze is 300 times more effective than the antifreeze in your car.
3. pH: The 3D shape of an enzyme can be affected by pH.
All enzymes have an optimal pH to work at depending on
where they are in the body.
•
Saliva pH 7
•
Stomach pH 2.5
•
Intestines pH 8.5
•
Vagina pH 2.5
When the pH is too low, the
positive hydrogen ions interact
with the negative R groups in
the protein and tear them away.
This denatures the enzyme by
changing its shape.
When the pH is too high, the
negative hydroxide ions
interact with the positive R
groups in the protein and tear
them away. This denatures the
enzyme by changing its shape.
H+
OH-
When an animal dies, the
body is decomposed by
bacteria or fungi. If conditions
prevent enzymes in the
bacteria from working, the
body will be preserved.
This photo (Tollund man)
shows a body that was
discovered in Demark in a
peat bog in 1950.
The person had been strangled, and at first the police thought it was
a recent murder. But peat bogs are very acid, and it turned out that
the body was 2,000 years old, and had been very well preserved in
the peat. Archaeologists believe the body is from a ritual murder, but
they are not sure if the person was killed as a punishment, or
whether the body was a sacrifice to the gods.
4. Inhibitors: Chemicals that interfere with
the enzyme action.
There are two types of INHIBITORS:
a) Competitive Inhibitors
b) Non-Competitive Inhibitors
Allosteric Site
Competitive Inhibitors are chemicals that so closely resemble
an enzyme’s normal substrate that it can attach to the enzymes
active site. The substrate and inhibitor “COMPETE”.
If the inhibitor occupies the active site of the enzyme, the substrate
will not be able to join and no product will form from that enzyme.
If the Inhibitor is removed, the enzyme will become active again.
Enzyme inhibitors are important commercially in many ways. For
example pesticides kill bugs by inhibiting essential enzymes that are
present in insects ( these enzymes are not found in humans) and
herbicides kill weeds by inhibiting some of their important enzymes.
Similarly many medications, such as
aspirin and antibiotics are inhibitors.
The enzyme substilin digests proteins,
and is used in laundry detergent.
Rennin, an enzyme extracted from
calves, is used in curdling milk to make
cheese.
Glucose oxidase detects glucose in the
urine (for example in diabetics).
Non-Competitive Inhibitors
are atoms or molecules that
attach to an enzyme at an
allosteric site and this
denatures the enzyme.
Non-competitive inhibitors
will sometimes destroy an
enzyme by permanently
binding to the allosteric site.
An example of this is heavy
metals, such as lead in the
nervous system.
[substrate]
Rate of Reaction
Another type of non-competitive inhibition is when a metabolic
product can feedback on a metabolic pathway to control how
much product is made.
The final product can temporarily attach to the allosteric site
on the first enzyme.
The enzyme will be denatured and the reaction will stop.
http://ca.youtube.com/watc
h?v=zl2KYhgZ_u8
This is an example of NEGATIVE FEEDBACK or FEEDBACK
INHIBITION.
When the concentration of the final product gets low again, there
will be less inhibition on the enzymes and the metabolic pathway
is reactivated.
Thyroxin, the hormone that controls the
metabolic rate of all of the cells in your body,
is produced by the thyroid gland in the neck.
If the concentration of thyroxin in your body is
high, your metabolic rate will be raised, and if
thyroxin levels are low, your metabolic rate will
be low.
The thyroid gland is stimulated to release
thyroxin by a hormone produced in the
pituitary gland called TSH (thyroid stimulating
hormone).
But the enzymes in cells of the pituitary that
make TSH are inhibited by thyroxin.
Therefore, if thyroxin
levels are high, the
pituitary stops producing
TSH, and if thyroxin
levels are low, the
pituitary makes the TSH.
Thus, the metabolic rate of
cells in your body are
maintained by the
feedback inhibition of an
enzyme
http://ca.youtube.com/watch?v=VnneZReATW0
•Palpitations
•Heat intolerance
•Nervousness
•Insomnia
•Breathlessness
•Increased bowel movements
•Light or absent menstrual periods
•Fatigue
•Fast heart rate and trembling
hands
•Weight loss
•Muscle weakness
•Warm moist skin
•Hair loss
•Staring gaze
Modern sloths live upside-down in the forests of South America and eat
leaves in trees.
They have claws to help them remain sleeping and suspended underneath
branches for hours. A sloth's grip on its branch is so secure that in death it
continues to hang unless it is forcibly unhooked.
Sloths are generally nocturnal and move around little when awake. When
they do move, it is at a slow and deliberate speed.
Sloths have a very slow metabolism
and take their sweet time digesting
food (1-2 weeks per meal) and
consequently, only defecate once in
a one week period.
Their metabolism is so slow that
they may take a half a minute to
move a leg a few inches. Their
digestive system is so slow that
they need only defecate about once
a week. They even sneeze slowly.
Being so slow, and indeed entirely
immobile for much of the time, they
are almost invisible to predators. By
keeping such a low profile they
avoid running into dangerous
confrontations.
http://ca.youtube.com/watch?v=eotEEUN
atKY&feature=related
However, sloths just don't get
much done in life. Their birthrate is
low, with a single young born once
a year. They can't do much for
their kids anyway -- a mother
rushing to help her threatened
infant was timed at 14 feet per
minute.
The slow or low rate of metabolism
in sloths effects their ability to fight
off illness. Most sloths have
difficulty surviving when in captivity
outside of their natural range
because they cannot fight off new
diseases or adapt to a colder
climate.
Most cell reactions (metabolism) require energy to occur. The
energy ‘currency’ of cells is a molecule called ATP.
ATP has 3 phosphates, the last two of which are held
together by a high energy bond.
It takes a lot of energy to make this phosphate bond, and
energy is released when the bond is broken.