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Enzymes
Many organs have adapted to make the exchange of materials more
efficient
...
These increase the surface area
over which exchange can take place
...

Organs also work together, when they do they are known as organ systems
...
The digestive system is a good example
...
The stomach and the small intestine are where this happens
most
...

o

Liver-producing bile

o

Stomach- breaking down large insoluble molecules into smaller
soluble molecules and absorption

o

Large intestine- absorbing water from undigested food
...
There are 20 types and depending on
the order they occur in the chains; different proteins can be formed
...


When there are many specialised cells of the SAME type working together in
one area, they are collectively known as a tissue
...

In the same way, when there are several kinds of tissues working together,
they form an organ
...
For
example: blood is an organ because it is made up of several different tissues
working together
...

Your stomach is an organ
...
It has glands to secrete the digestive juices
...


Examples of proteins are:
- Insulin: a
involved in the control of
antibodies to destroy pathogens

hormone
blood sugar levels
...

- Enzymes which act as catalysts
All carbohydrates are made of sugars
...
Examples of carbohydrates:



Starch- a glucose store in plants



Glycogen- a glucose store in animals



Cellulose- a structural carbohydrate in the cell walls of plants

All lipids are fats and
oils
...
They
are insoluble in water
and stored in adipose
tissues
...
It is the combination of different fatty acids
that determines whether a fat will be a solid or liquid
...
These proteins speed up chemical
reactions without being used up- they therefore catalysts
...
An example of a substrate is the chemical – hydrogen peroxide
...

All enzymes are proteins, described as biological catalysts
...
For
example: hydrogen peroxide
...
But if catalase is
added, it will very quickly be turned into oxygen and water
...
Early idea of the mode of action of the active site

were based on the concept of a negative impression of the substrate- the
lock and key concept
...
The enzyme has an active site, which
has the same shape as the substrate molecule that the enzyme is acting on
...
Once the reaction has occurred and product molecules
have been formed, they no longer have a shape that can fit the active site
...


Enzyme Reactions
Enzymes combine reersibly with their substrates:
 Enzyme + substrate
 Enzyme – substrate complex
 Enzyme + products
All the chemical reactions occuring in your body are called your metabolism
...
Many break
larger molecules into smaller ones- the catabolic enzymes
...
Some can also
change one form of a molecule into another
...

- Temperature
- Ph
Any factor that affects the actuve site of an enzyme by changing its shape
said to cause the enzymes to become denatured
...


Temperature- all enzymes have an optimal reaction temperature where
they work the best
...
most mammalian enzymes are optimal at around 40°C
...
The increased
number of collisions accelerates the reaction
...
This disrupts the structure of the enzyme,
disrupting the active site and causing it to be denatured- NOT DEAD
...
It will regain its activity as it approaches its
optimal temperature
...
The
optimal pH of enzymes vary over a narrow range
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Enzymes do not ever recover from being denatured
...


Speeding Up Digestion
Digestion begins by chewing up food with your teeth
...
Chewing works for carbohydrate and
proetins because theya re solule in water but not for lipids
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Your body temperature is 37°C
...
Your stomach has thousands of cells that secrete
hydrochloric acid
...
The acid is
there to kill bacteria enetering your body in your food
...

Enzymes are not acids!
The trouble is that your small intestine absorbs food best at ph values close
to neutral (pH 7-8, alkaline), and cannot be covered in mucus
...
It does this by adding bile
...
Bile neutralises stomach acid
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Lipids and soils do not mix with water,
they form globules and drops instead
...

These tiny droplets form something called an emulsion
...
Bile emulsifies
fats and oils
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This causes severe pain and stops bile from acting oon lipids in
the gut

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