Assignment A2 – Produce A Booklet or Report
Centre Number Candidate Number -
Digestion
Activity One
Booklet/Report
Contents
How we digest our food
Mouth
Gullet
How we digest our food (continued)
Stomach
Small Intestine
How we digest our food (continued)
Large Intestine
Caecum
Appendix
The Digestion System
Digestion Tables
How We Digest
Our Food
Mouth
Firstly the food is broken down by the teeth. Chewing breaks the food
down into smaller pieces, increasing the surface area over which the
enzymes can act. As the food is being chewed, saliva is produced.
Saliva comes from the salivary glands, which are connected to the
mouth cavity by ducts. Saliva contains an enzyme called amylase. This
acts on starch, breaking it down into malt sugar (maltose) Saliva also
contains a slimy substance called mucus. This serves as a lubricant, enabling food to pass easily
through the throat when it’s swallowed.
When you swallow, the food is pushed down the back
of your throat by your tongue.
 At the same time the entrance to the windpipe is
closed off, so the food is prevented from going
down the wrong way.
 Once swallowed the food passes down the gullet
into the stomach. The gullet has muscle tissue in
its wall.
 A ring of muscle contraction moves slowly
downwards, pushing the food in front of it.
 This process is called peristalsis. Mucus again acts
as a lubricant, enabling the food to slip down
easily.
Stomach
The wall of the stomach is thick and it contains lots of gastric
glands. The gastric glands produce a fluid called gastric juice.
This contains an enzyme called pepsin which breaks down
protein into simpler substances called polypeptides. Pepsin
works best in acid conditions. For this reason gastric juice
contains hydrochloric acid. The acid also helps to kill germs
which happen to get into the stomach. The wall of the stomach
produces lots of mucus which protects the stomach lining from
being damaged by the acid. Food spends three or four hours in the stomach. Between the stomach
and the small intestine there is a ring of muscle. This is tightly shut most of the time, but every now
and again it opens. At the same time a wave of contraction passes along the stomach and sweeps
some of the food into the small intestine. If there is anything wrong with the food, violent
contractions occur in the other direction. As a result the contents of the stomach are shot up the
gullet and out through the mouth. This is vomiting and it is a useful way of getting rid of germs and
poisons.
Small Intestine
The inner surface of the small intestine has many finger like
projections called villi. The villi greatly increase the surface
area for absorption. The wall of the small intestine has a very
good blood supply. The villi contain blood and lymph
capillaries into which the digested food substances are
absorbed.
Muscle tissue in the wall enables the intestine to contract,
squeezing the contents this way and that, and strands of muscle
in the villi enable them to wave about. As a result the contents of
the small intestine are constantly brought into contact with the
lining. Every now and again a ring of contraction passes along
the small intestine, sweeping the contents towards the large
intestine.
The Large Intestine
As material moves along the colon, water is absorbed from it. As a
result it becomes more and more solid. The solid matter moves on
to the rectum where it is stored as faeces. The lining of the rectum
produces mucus which acts as a lubricant and eases the passage of
the faeces. Eventually the faeces are egested through the anus.
This is a reflex, triggered by the build up of pressure in the
rectum. The ring of muscle surrounding the anus opens up, and the
wall of the rectum contracts forcing the faeces out. The polite
word for this is defecation. Normally it takes between 24 and 48 hours from when the food is eaten
to when the faeces are ready to be expelled through the anus.
The Caecum and Appendix
The caecum and appendix are an off-shoot from the large intestine. They have no function in the
human, but in grass eating mammals, such as rabbits, they contain large numbers of helpful bacteria
which can digest cellulose and break it down into glucose. In humans the appendix can sometimes
become infected with harmful bacteria. As the appendix sticks out from the intestine, the bacteria
don’t get flushed out by the normal passage of material along the gut. So they multiply there, and
may cause severe inflammation leading to appendicitis. Normally appendicitis is cured by removing
the appendix in and operation.
Digestion Tables
This table outlines the path of food through the digestive system. It also tells us the special features
of each organ and the function.
Path of Food
Organ
Special Features
Function
Mouth
Teeth, tongue
Chewing food; digestion of starch
Oesophagus
Movement of food by peristalsis
Stomach
Gastric glands
Storage of food; acidity kills some bacteria; digestion
of protein
Small intestine
Villi
Digestion of all foods; absorption of nutrients
Large intestine
Absorption of water; storage of non-digestible
remains
Anus
Defecation
The following table shows us the various components of the main enzymes found in the human gut.
Where it comes
from
Where it works
Name of enzyme
Food acted on
Substances
produced
Salivary glands
Mouth cavity
Amylase
Starch
Maltose
Stomach wall
Stomach
Pepsin
Protein
Polypeptides
Liver
Small intestine
Bile salts
Fat
Fat droplets
Pancreas
Small intestine
Wall of small
intestine
Small intestine
Amylase
Trypsin
Lipase
Maltase
Sucrase
Peptidases
Starch
Protein
Fat
Maltose
Sucrose
Polypeptides
Maltose
Polypeptides
Fatty acids
Glucose
Glucose & fructose
Amino acids
Enzymes are proteins which speed up chemical reactions inside cells i.e. Biological catalysts.
Enzymes are necessary since the temperature of a living organism is relativity low. Enzymes are
involved in both building up and breaking down of molecules. Enzymes are normally very specific,
they only have an effect on one substance, its substrate. Enzymes are specific because the substrate
must have a shape which is complementary to the shape of the active site. (see below)
Activity Two
The Report
Topic Chosen
I have decided to do my I.C.T coursework on digestion. This is a topic which I study for my GCSEs
in biology. I have chosen this topic because I really enjoy biology and find digestion very
interesting.
In my booklet I have included pictures of the digestive system and a lot of information. I have also
added some tables which are very helpful.
I found most of my information from the school’s biology book. To copy the pictures from the book
I scanned them in using my home scanner. I then used an editing package to make them look better.
I also got a lot of my information off various websites, I found these websites by going to the search
engine, www.ask.com and typing in what information I was looking for. To copy the pictures from
these websites I right-clicked on the picture I wanted, and then scrolled down to ‘copy’. I then went
back to my word document and went to ‘edit’ at the top of the screen, and down to ‘paste’. These
pictures make my booklet more appealing to the people who are reading it because it gives them a
better understanding of the topic.
Choice of I.C.T
application
For my booklet I have decided to use the computer programme Microsoft Word. This is because I
found this programme the most suitable for the task I was given. With Microsoft Word I can indent
paragraphs, change the font, insert tables and use bullets points all very easily and quickly.
Another reason why I chose to use Microsoft Word was because I can view what I have done so far
in print preview mode. This shows me the entire document before being printed. It also saves time
and paper.
Also, Microsoft Word gives us the choice of putting in headers and footers into the document. This
is very easy to do and it also makes the document look a lot better.
This is the cover page. I
got the picture of the
human digestive system
from a website on the
internet. I found this
website by going to the
search engine
www.ask.com.
To copy the picture I
right clicked on the
picture I wanted and then
scrolled down and click
on copy. I then returned
to my word document
and clicked on edit at the
top of the screen, and
then scrolled down to
paste.
If you have some
information that you want to
put into bullet points, the
computer programme
Microsoft Word allows you
to do this very easily.
All you have to do is to click
on the word on which you
want your first bullet point to
be. In this case its, ‘When’
You then go to the top of the
screen and click on the button,
‘bullets’. This will bring up
your first bullet point for you.
To add new bullet points you
can just press the ‘enter’
button on your keyboard.
Microsoft word also gives
us the choice of changing
the actual bullet points.
We can do this by going to
‘format’ and then scrolling
down to ‘bullets and
numbering’.
You can also change the
bullets to numbers or letters.
This is very handy if you
are writing rules, for
example.
Once you do that this popup screen appears. You
can then choose the bullet
point of your choice.
Once you have made your
choice you then click on
“ok”.
I found the website, with
this picture, by going to
the Internet search engine
www.ask.com.
This is the picture that I used
on page 6 of my booklet. It
is entitled ‘The Digestive
System’.
To copy this picture I held
my cursor over it and right
clicked. I then scrolled down
the options box until I came
to ‘copy’. I then clicked on
copy.
Once you do the above, you
then go back to your word
document and click on ‘edit’
and then scroll down to
‘paste’. This will paste the
picture onto the page.
Once the picture is on
your word document you
can change the size of it.
You can do this by
clicking on one of the
handles and pulling the
cursor towards the middle
to make it smaller or by
moving it away to make it
bigger.
Whilst changing the size
of the picture, hold in
‘CTRL’, this will stop the
picture from being
distorted.
Information
Sources Used
I found most of my information from the school’s biology book. To copy the pictures from the book
I scanned them in, using my home scanner, I then used an editing package to make them look
better.
I also got a lot of my information off various websites. I found these websites by going to the search
engine, www.ask.com and typing in what information I was looking for. To copy the pictures from
these websites, I right clicked on the picture I wanted, and then scrolled down to ‘copy’. I then went
back to my word document and went to ‘edit’ at the top of the screen, and down to ‘paste’. These
pictures make my booklet more appealing to the people who are reading it because it gives them a
better understanding of the topic.