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GCSE level biology exam revision notes on
HOMEOSTASIS 2.
Part
2.3
Diabetes type 1 and diabetes type 2 -
problems with insulin and how to make sure your blood sugar levels are safely
at a normal concentration - problems with insulin levels in the blood
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Sub-index of notes on homeostasis:
Blood sugar level
control, insulin, diabetes
(2.3) Diabetes -
health issues with insulin production and how to regulate it if need be
Introduction
Reminders
Insulin reduces the concentration
of glucose in your blood - triggers the conversion of glucose into
glycogen - your principal chemical potential energy store.
Lack of insulin can lead to
dangerously high glucose levels in your blood.
See (1)
The need to control the blood sugar
level - health issues
What is diabetes?
Diabetes conditions occur in people whose body,
for one reason or another,
does not produce enough insulin to adequately control the level of
glucose in the bloodstream.
Diabetes is the failure of the homeostasis
control system described in the previous section i.e. the negative
feedback system based on the hormones insulin and glucagon - diagram
below.
Type 1
Diabetes - caused by insulin deficiency
Type 1 diabetes is a disease in which a person’s
blood glucose concentration may rise to a high
level because the pancreas does not produce
enough of the hormone insulin.
What causes type 1 diabetes? The insulin producing cells are
destroyed - this can be due to an autoimmune condition in which the
immune system mistakenly attacks the body's own healthy cells.
Type 1 diabetes is caused by a
lack of insulin, the hormone which controls the level of glucose in the blood -
too little may be produced or non at all - a potentially dangerous
situation.
Without insulin secretion the blood glucose level to rise
to potentially lethal levels.
 Without insulin, the body's cells are unable
to utilise glucose, whose level becomes dangerously high and excreted in the urine.
The graph on the right compares the glucose
concentration in the blood after a Type 1 diabetic and a
non-diabetic person after each is given a sugary drink.
The diabetic, not producing insulin, has no
control over the glucose level which rises well above that normally
required. It remains too high, but can be lowered if insulin is
injected into the body.
The non-diabetic produces insulin from the
pancreas in response to the rising concentration of glucose, which
goes well above normal. The glucose level then falls back to normal
as the body's cells take up the glucose (respiration or glycogen
formation).
Note that if the supply of glucose is
inadequate, the body's cells use fat and protein as alternative
energy supplies.
If the diabetes is not controlled, a
person can lose weight and lead to kidney failure and death.
Type 1 diabetes may be controlled
partially by careful
attention to diet and exercise, BUT injection of insulin, usually into the
subcutaneous fat is required- insulin therapy must always be applied to type 1 diabetes
patients.
Type 1 diabetes can be controlled by two
strategies, and both may be required ..
There is NO CURE for Type 1 diabetes and it
cannot be prevented.
(i) Avoid too much sugary foods and
carbohydrates in the diet, sugars in particular, will cause a rapid rise in
glucose levels which is difficult to remove without the presence of
sufficient insulin - but diet management is not enough to cope with
Type 1 diabetes.
(ii) Insulin therapy - injecting insulin, perhaps
several times a day at meal times, which will make the
liver and muscles remove excess glucose from the digested food - this makes sure the
excess glucose is converted to glycogen, reducing the concentration in
the blood.
This is an inconvenient, but very effective
way, of keeping the blood sugar level in check.
The insulin is usually injected into the
subcutaneous fatty tissue just under the skin.
You cannot take insulin orally as a
pill or tablet because the enzymes in your stomach break it
down before it can reach the bloodstream.
The amount of insulin required varies from
individual to another - it depends on the body mass, diet and
exercise they take - injecting too much insulin could lead to
too low a level of glucose in the blood.
In Type 1 diabetes, the level of physical
activity and diet affect the amount of insulin required.
The amount of insulin required by injection depends on
the person's diet and level of physical activity.
A diabetic should minimise food rich in simple
carbohydrates like glucose which can cause quite a rapid increase in blood sugar.
As well as controlling carbohydrate intake,
taking regular exercise helps to use up some of the excess glucose
from the blood.
It is dangerous to inject too much
insulin because that could lead to dangerously low levels
of glucose.
Insulin injections can greatly help
diabetics in providing the necessary insulin but it can never be as
successful as a properly functioning normal pancreas and diabetics can
suffer from long-term health problems.
A healthy balanced diet, regular eating and
regular exercise will both help to keep a diabetic in good health and
minimise the amount of insulin needed.
Diabetics can have a pancreas transplant
which, if successful, can theoretically avoid the need for insulin, but
there is always the danger tissue rejection and costly immunosuppressive
drugs must be taken (with the added complication of serious side-effects).
Monitoring your blood sugar
levels
You can do a blood sugar level check by doing a finger-prick
test, or by using an electronic blood sugar monitor
called a flash glucose monitor or CGM.
You can do this several times a day – helping you
keep an eye on your levels as you go about your life and help you
work out what to eat and how much insulin medication to take.
Footnote on source of insulin
Insulin was once extracted from the pancreas
of a pig or cow, but human insulin is now made genetic engineering and
doesn't give the side effects experienced from patients using animal
insulin.
I remember a class debate on the merits and
ethical issues concerning the use of genetic modification (GM)
engineering. A diabetic in the class took to task another student trying
to take the 'moral high ground' in arguing how wrong it was to use GM
for medical purposes (or any other purpose - on the grounds it was
interfering with nature). So, can I please point out the millions of
diabetic patients around the world whose lives are so much more improved
by a 'slow release' genetic modification of the hormone insulin.
Type 2 Diabetes - caused by insulin
resistance
Type 2 diabetes is caused by a
person becoming resistant to their own insulin.
The type 2 diabetes condition is
(i) When the
pancreas doesn't make enough insulin to enable the body to respond
effectively to rising glucose levels.
(ii) The person has become resistant to
insulin so the body doesn't even respond appropriately to any of the
hormone insulin
present - its as if the body's cells have lost their sensitivity to changes
and both will cause the blood sugar level to rise
to potentially lethal levels.
Test for Type 2 diabetes
One test is to ask the patient to refrain
from eating and drinking for ~10 hours and the glucose level in
the blood measured.
The patient is then given glucose and
their blood reanalysed for its concentration 2 hours later.
If the patient's tolerance to glucose is
lowered, the glucose will be above an acceptable level.
Type 2 diabetes can be controlled by eating
a healthy balanced diet, regular eating, regular exercise and losing weight
if necessary.
Being overweight increases your chance of
developing type 2 diabetes, obesity is considered to be potentially a
major risk factor in the onset of diabetes disease.
As well as a poor diet of too much fat and
carbohydrates (often 'fast food'), lack of exercise can be
another contributing factor.
Sadly, in the UK, there are rising numbers of
diabetes Type 2 cases being recognised.
It is estimated, in the UK, about 3 in 10
children are obese.
Type 2 diabetes patients should make an effort to
control the amount of carbohydrates in their food and take regular
exercise - both strategies can help reduce the glucose sugar level in
the blood.
Some Type 2 diabetics take medication or insulin to help
control this diabetic condition - but insulin therapy is more associated
with type 1 diabetes.
There is some correlation between
obesity and Type 2 diabetes.
Obese people have an increased risk to develop
type 2 diabetes.
There are two ratio indexes used as a measure of
obesity.
They are both described in detail in the last
section on this page.
Obese people (BMI > 30) do run the risk of
developing type 2 diabetes,
and if their BMI is over 30, then action should
be taken.
Body Mass Index (BMI) = (body mass in kg) /
(height in m)2
Footnote on the food and drinks
industry
Many drinks, processed foods and snacks
contain too much sugar, but they are very popular.
Governments, with some success, have tried to
get manufactures to reduce the sugar content in food.
How, and should we, enforce changes on
manufacturers to control our diet?
Isn't there an ethical responsibility for
manufacturers to produce more healthy food?
Cafes, restaurants and school/factory canteens
should provide healthy food that contributes to a healthy diet.
One idea is to impose a 'sugar tax' on the
cost of sugar rich foods or directly on food companies that produce
them.
However, such a tax might disproportionately
affect the poorest people in society, where statistics show they are
the most at risk from diabetes - some of the most unhealthy food is
also the cheapest and most children like 'snacky' foods too (as do
many of us adults, but it is occasionally a relatively harmful
lifestyle choice!).
Measures of obesity
(just
one measure of healthiness and well-being)
However, people outside the limits of the indexes
described below, i.e. overweight or obese, could be more susceptible
to diabetes than the average person.
Introduction
There is no such thing as the 'perfect
weight', we come in all shapes and sizes, but there are limits
within which we should be to be healthy!
In the medical profession, a doctor can't just
simply that somebody is overweight, without reference to some kind
of statistical index, usually by one/both of the ratios described
below.
Equally healthy people can have quite
different weights, but there are some reasonably good indicators as
to when your weight is not what it should be 'ideally'.
In rich developed countries we are often dealing
with 'overweight' people eating too much rich fatty food.
The negative health effects of being overweight and
obese, many of which can be fatal include: high blood pressure (hypertension),
high LDL cholesterol or
high levels of triglycerides,
Type 2 diabetes,
coronary heart disease, stroke and gallbladder disease.
The Body Mass Index
The body mass index is a 'rough' guide to help
the medical profession decide whether you are underweight, normal,
overweight or obese - based on your height and height.
The higher your BMI the more fat you are
carrying - but not necessarily unhealthily.
Body Mass Index (BMI) = (body mass in kg) /
(height in m)2
When measured, you then consult a table of BMI
values to se where you fit in!
Table of BMI values (from
https://www.vertex42.com/ExcelTemplates/bmi-chart.html)
|
Body mass index |
Weight description |
|
less than 18.5 |
underweight |
|
18.5 to 24.9 |
normal |
|
25.0 to 29.9 |
overweight |
|
30.0 to 40.0 |
moderately obese |
|
over 40.0 |
very obese |
If you eat too much fatty sugary foods and
don't take enough exercise, most people will put on weight and too
much of it. You are taking in too much energy rich food for your
daily needs.
The excess energy releasing food is stored as
fat and gives you a raised BMI value.
Having a higher than normal BMI value
increases your risk of developing type 2 diabetes.
Note of caution: Having a high BMI is not
always unhealthy e.g. athletes train hard to build up extra muscle
which is heavier than fat, so they will tend to have higher than
'normal' BMI values and would not be classed as overweight.
The waist-to-hip ratio
Where the body stores fat is quite
important.
If a lot of fat is stored around the
abdomen you get a 'fat tummy' and this is associated with an
increased risk of developing type 2 diabetes - hence the
importance of diet and exercise.
Comparing the circumferences of waist and hips
is another measure of whether you are 'overweight' and concentrates
around one area where we can accumulate to much fat - the 'tummy'.
waist-to-hip ratio = circumference of waist
(cm) /
circumference of hips (cm)
The higher your waist-to-hip ratio the more
fatty tissue you are carrying around the middle of your body.
When measured, you then consult a table of BMI
values to se where you fit in!
Table of waste-to-hip ratios (from
https://www.healthline.com/health/waist-to-hip-ratio)
|
Health risk |
waist-to-hip ratio (women) |
waist-to-hip ratio
(men |
|
low |
less than 0.81 |
less than 0.96 |
|
moderate |
0.81 to 0.85 |
0.96 to 1.00 |
|
high (overweight) |
over 0.86 |
over 1.00 |
If you are female and your waist-to-hip ratio
is over 0.86 you are classed as overweight.
If you are male and your waist-to-hip ratio is
over 1.00 you are classed as overweight.
If you are above the moderate waist-to-hip
ratio values you are carrying too much fat around your 'middle' -
referred to as abdominal obesity.
Having a higher than normal waist-to-hip ratio
increases your risk of developing type 2 diabetes.
Key points
Source of information is based on textbooks & syllabus-specifications for students taking the AQA
GCSE, Edexcel GCSE and OCR
GCSE level biology examinations (~US grades 9-10).
Key
points about diabetes and health issues
Revision notes for
biology students on Type 1 and Type 2 diabetes,
including their causes, effects,
treatments, and links to non-communicable
diseases and health issues.
What Is Diabetes?
Diabetes
is a chronic condition where the body cannot properly regulate blood glucose levels. It is a
non-communicable disease
(NCD), meaning it is not caused by pathogens and cannot be
passed from person to person.
Comparing the
two types of diabetes
| Feature |
Type 1 Diabetes |
Type 2 Diabetes |
| Cause |
Autoimmune destruction of
insulin-producing cells in the pancreas |
Body cells become resistant to
insulin (insulin no longer works effectively) |
| Onset |
Usually in childhood or
adolescence |
Usually in adults, but
increasingly in teens |
| Insulin Production |
Little or none |
Normal or high, but
ineffective |
| Treatment |
Insulin injections |
Diet, exercise, medication,
sometimes insulin |
| Risk Factors |
Genetic, autoimmune |
Obesity, poor diet, lack of
exercise, age |
Causes of
diabetes
Type 1 Diabetes
-
Autoimmune
disease: The immune
system attacks beta cells in the pancreas that
produce insulin.
-
Genetic
predisposition: Runs
in families.
-
Environmental
triggers: Possibly
viral infections.
Type 2 Diabetes
Effects of Diabetes
If untreated or
poorly managed, both types can lead to:
-
Hyperglycaemia
(high blood glucose)
-
Fatigue
and blurred vision
-
Kidney damage
(nephropathy)
-
Nerve damage
(neuropathy)
-
Eye damage
(retinopathy → blindness)
-
Cardiovascular
disease
-
Slow wound
healing and
increased infection risk
Treatments
Type 1 Diabetes
-
Insulin
injections (daily or
via pump)
-
Monitoring
blood glucose
regularly
-
Balanced diet
and exercise
Type 2 Diabetes
Links with
Non-Communicable Diseases (NCDs)
-
Type 2
diabetes is strongly
linked to other NCDs:
-
Heart
disease
-
Stroke
-
Kidney
failure
-
Certain
cancers
-
Obesity
is a major shared risk factor.
-
These diseases often
occur together, increasing overall health risks.
Importance in
Understanding Human Biology
-
Demonstrates
homeostasis in action (blood glucose regulation).
-
Highlights the role of
the endocrine system (insulin and glucagon).
-
Shows how
lifestyle choices impact long-term health.
-
Encourages
preventative healthcare and early diagnosis.
-
Reinforces the concept
of non-communicable diseases and their societal
impact.
Exam Tips
-
Use key terms:
insulin, glucagon, glycogen,
homeostasis, negative feedback,
pancreas, non-communicable disease.
-
Be able to
compare Type 1 and Type 2 diabetes.
-
Interpret
graphs showing blood glucose levels before and after meals
or insulin treatment.
-
Understand
risk factors and preventative strategies.
Keywords, phrases and learning objectives for this part on ?
This page will help you answer questions like e.g. What are glucagon and insulin? What do
they do in your body? What is the difference between type 1 diabetes and type 2 diabetes?
Know what diabetes is and the difference between
type 1 diabetes and type 2 diabetes.
Know diabetes is about insulin production
(deficiency) and resulting health issues and insulin is required to
ensure blood sugar levels are safely normal.
Know that diabetes treatments and strategies include insulin therapy
injection, avoiding sugary foods, monitoring blood sugar levels e.g.
with a finger
prick test and an electronic flash glucose monitor.
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