Get the most from this book
Everyone has to decide his or her own revision strategy,
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your understanding. These Revision Notes will help
you to do that in a planned way, topic by topic. Use
this book as the cornerstone of your revision and don’t
hesitate to write in it — personalise your notes and
check your progress by ticking off each section as you
revise.
You can also keep track of your revision by ticking off
each topic heading in the book. You may find it helpful
to add your own notes as you work through each topic.
My revision planner
1 The causes of disease
Unit 1 Biology and disease
1 The causes of disease
Revised
Tested
Exam
ready
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XX Pathogens
. . . . . basic
. . . . . . . causes
. . . . . . . . . of
. . . .disease:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
There are three
XX Lifestyle
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● pathogens
lifestyle
2 The●digestive
system
● genes
XX The
digestive system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tick to track your progress
Use the revision planner on pages 4 and 5 to plan your
revision, topic by topic. Tick each box when you have:
l revised and understood a topic
l tested yourself
l practised the exam questions and gone online to
check your answers and complete the quick quizzes
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Proteins
. . . cause
. . . . . . . . of
. . . .any
. . . . .one
. . . . . disease
. . . . . . . . . .is
. . .often
. . . . . . . a
. . complex
. . . . . . . . . . . .mixture
. . . . . . . . . . .of
. . .two
. . . . . .or
.
The actual
moreenzymes
of the above
factors.
How
work
. . . . For
. . . . . example,
. . . . . . . . . . . . some
. . . . . . . .people
. . . . . . . . . inherit
. . . . . . . . . genes
. . . . . . . . that
. . . . . .
make them more likely to develop heart disease or a particular type of
Enzyme properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
cancer, but their lifestyle also has a lot to do with it.
Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Carbohydrate digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Types
ofplasma
pathogen
Lipids
and
membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diffusion
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pathogens
are disease-causing organisms. Most pathogens are
Osmosis
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. . . . . . .as
. . .bacteria,
. . . . . . . . . . . viruses
. . . . . . . . . and
. . . . . .fungi,
. . . . . . . .but
. . . . .there
. . . . . . . are
. . . .
microorganisms such as . . .such
also larger
pathogens
Active
transport
. . . such
. . . . . . .as
. . . worms
. . . . . . . . . .and
. . . . . flukes.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pathogens
3 Cells, diffusion and absorption
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Absorption
of glucose
The terms transmissible,
infectious and communicable all refer to the same■
thing: diseases
you can catch.
Sneezing, kissing, drinking dirty water, insect■
Cholera
— a bacterial
disease
. . . . . . . . . . . . . . . . . .
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bites — there are lots of ways to transfer pathogens from one person to
4 Theanother.
lungs and lung disease
XX Lung function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bacteria
XX The biological basis of lung disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bacterial diseases include tuberculosis (TB), cholera and typhoid. Bacteria
5 Theoften
heart
heart
causeand
disease
becausedisease
their waste products are toxic. For example,
the bacteria
that cause
(severe
XX Heart
structure
and botulism
function
. . . . . . . food
. . . . . . .poisoning)
. . . . . . . . . . . . . .produce
. . . . . . . . . . . a
. . . . . . . .
toxin that paralyses muscles. This is the ‘botox’ (botulinum toxin) that is
XX The biological basis of heart disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
commonly used in cosmetic surgery.
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6 The immune system
Viruses
XX Principles of immunology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Viruses are tiny, infectious particles. They consist simply of some DNA
or RNA (containing a few genes) surrounded by an outer protein coat.
They are not classed as living organisms because they do not perform the
classic signs of life such as feeding, growth and excretion. All they do is
reproduce, and they cannot do that on their own. They need a host cell.
Unit 2Viruses
Theget
variety
of use
living
into cells and
them organisms
to make thousands of identical copies
of the virus, which have the potential to burst out and infect new cells.
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Features to help you succeed
7 TheFungi
nature of variation
Revised
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variation
. . . . . . . . . . fungi
. . . . . . . . do
. . . . not
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. . .a . . threat
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Compared to bacteria
and viruses,
to someone
with a healthy
XX Causes
of variation
. . . . . . .immune
. . . . . . . . . . . system.
. . . . . . . . . . Athlete’s
. . . . . . . . . . . .foot
. . . . . . and
. . . . . .thrush
. . . . . . . . .are
. .
about as bad as fungal diseases get.
Examiner’s tips and summaries
8 DNA and cell division
XX Structure of DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Genes and polypeptides
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Expert tips are given throughout the book to help you polishXX
technique in order to
your
XX your
DNA andexam
chromosomes
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chances in the exam.
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8
. . . . . .quick
. . . . . . . . .quizzes
. . . . . . . . . . . .at
. . . .www.therevisionbutton.co.uk/myrevisionnotes
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Exam practice answers and
179705_01_Biology_1-114.indd 8
4
20/09/12 1:37 PM
Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
The summaries provide a quick-check bullet list for each topic.
179705_01_Biology_1-114.indd 4
Typical mistakes
The author identifies the typical mistakes
candidates make and explains how you can avoid
them.
Definitions and key words
Clear, concise definitions of essential key terms are
provided on the page where they appear. Key words
from the specification are highlighted in bold for you
throughout the book.
Exam practice
Practice exam questions are provided for each topic.
Use them to consolidate your revision and practise
your exam skills.
179705_01_Biology_1-111.indd 3
15/09/12 6:01 PM
Now test yourself
These short, knowledge-based questions provide the
first step in testing your learning. Answers are at the
back of the book.
Revision activities
These activities will help you to understand each
topic in an interactive way.
Online
Go online to check your answers to the exam
questions and try out the extra quick quizzes at
www.therevisionbutton.co.uk/myrevisionnotes
31/10/12 12:16 PM
My revision planner
Unit 1 Biology and disease
1 The causes of disease
Revised
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8Pathogens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10Lifestyle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 The digestive system
13 The digestive system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16 How enzymes work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17 Enzyme properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23 Carbohydrate digestion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Cells, diffusion and absorption
26Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
30 Lipids and plasma membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
33Diffusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
35Osmosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37 Active transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37 Absorption of glucose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
38 Cholera — a bacterial disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 The lungs and lung disease
41 Lung function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44 The biological basis of lung disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 The heart and heart disease
47 Heart structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
51 The biological basis of heart disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 The immune system
55 Principles of immunology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
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Unit 2 The variety of living organisms
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7 The nature of variation
60 Investigating variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
62 Causes of variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 DNA and cell division
64 Structure of DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
66 Genes and polypeptides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
68 DNA and chromosomes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
69Meiosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
70 Replication of DNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
72Mitosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
73 Cell cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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9 Genetic diversity and selection
77 Genetic diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
79 Cell differentiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
80Antibiotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
80 Genetic variation in bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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10 Surface area, volume, gas exchange and transport
84 Size and surface area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
85 Gas exchange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
87 Mass transport systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
94Haemoglobin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
97Carbohydrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
98Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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11 Biodiversity and classification
01 Principles of taxonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1
103 Genetic comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105Behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105Biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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109 Now test yourself answers
Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
My revision planner
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Countdown to my exams
6–8 weeks to go
One week to go
Start by looking at the specification — make sure
you know exactly what material you need to
revise and the style of the examination. Use the
revision planner on pages 4 and 5 to familiarise
yourself with the topics.
l Organise your notes, making sure you have
covered everything on the specification. The
revision planner will help you to group your notes
into topics.
l Work out a realistic revision plan that will allow
you time for relaxation. Set aside days and times
for all the subjects that you need to study, and
stick to your timetable.
l Set yourself sensible targets. Break your revision
down into focused sessions of around 40 minutes,
divided by breaks. These Revision Notes organise
the basic facts into short, memorable sections to
make revising easier.
l
l
Revised
4–6 weeks to go
l
l
l
l
l
l
Read through the relevant sections of this book
and refer to the examiner’s tips, examiner’s
summaries, typical mistakes and key terms. Tick
off the topics as you feel confident about them.
Highlight those topics you find difficult and look
at them again in detail.
Test your understanding of each topic by working
through the ‘Now test yourself’ questions in the
book. Look up the answers at the back of the
book.
Make a note of any problem areas as you revise,
and ask your teacher to go over these in class.
Look at past papers. They are one of the best
ways to revise and practise your exam skills.
Write or prepare planned answers to the exam
practice questions provided in this book. Check
your answers online and try out the extra quick
quizzes at www.therevisionbutton.co.uk/
myrevisionnotes
Use the revision activities to try different revision
methods. For example, you can make notes using
mind maps, spider diagrams or flash cards.
Track your progress using the revision planner and
give yourself a reward when you have achieved
your target.
Try to fit in at least one more timed practice of
an entire past paper and seek feedback from your
teacher, comparing your work closely with the
mark scheme.
l Check the revision planner to make sure you
haven’t missed out any topics. Brush up on any
areas of difficulty by talking them over with a
friend or getting help from your teacher.
l Attend any revision classes put on by your
teacher. Remember, he or she is an expert at
preparing people for examinations.
Revised
The day before the examination
Flick through these Revision Notes for useful
reminders, for example the examiner’s tips,
examiner’s summaries, typical mistakes and key
terms.
l Check the time and place of your examination.
l Make sure you have everything you need — extra
pens and pencils, tissues, a watch, bottled water,
sweets.
l Allow some time to relax and have an early
night to ensure you are fresh and alert for the
examination.
l
Revised
My exams
AS Biology Unit 1
Date: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Location: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AS Biology Unit 2
Date: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Time: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Location: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Revised
6
Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
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4 The lungs and lung disease
Lung function
Why exchange gas?
Revised
It’s all about respiration — the process that releases the energy locked
in organic molecules such as glucose and lipids. All cells, in all living things,
respire all the time. The process requires a constant supply of oxygen and
produces carbon dioxide that needs to be eliminated.
The lungs are organs that are adapted for gas exchange in air. Their
function is simple: to get as much fresh air as possible in contact with
blood. As you can see in Figure 4.1, the bronchial tree is a branching
system of tubes that takes air to the alveoli deep in the lungs. All of the
tubes are held open by rings of cartilage except the terminal bronchioles.
Examiner’s tip
Ventilation and breathing refer to
the same process, but respiration
is different. Make sure you use the
correct terms.
Rib section
Right bronchus
Trachea
Two pleural layers
Left lung
Pleural fluid
(acts as a
lubricant)
Space
occupied
by heart
Intercostal
muscles
Muscular
part of the
diaphragm
Terminal
bronchiole
Alveolus
Figure 4.1 The structure of the human gas exchange system
The alveolar epithelium
Revised
The alveolar epithelium is a surface over which gas exchange takes
place. Its structure is related to function:
● Millions of alveoli provide a large surface area.
Unit 1 Biology and disease
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4 The lungs and lung disease
●
The alveolar walls consist of flat cells called squamous epithelium
that are as thin as possible. This makes the diffusing pathway as small
as possible.
● The dense network of blood capillaries around the alveoli means that a
lot of blood is in close contact with the air.
● The beating of the heart, along with constant breathing, makes sure
that deoxygenated blood meets fresh air. This maintains a diffusion
gradient.
All these features serve to make diffusion as fast and efficient as possible.
The rate of diffusion of a substance across an exchange surface is inversely
proportional to the thickness of the exchange surface.
The exchange of gases at the alveoli
Revised
The exchange of gases at the alveoli (Figure 4.2) occurs by simple
diffusion. Oxygen and carbon dioxide are small, simple molecules that
pass easily through cell walls. There is more oxygen in the air than in the
blood, so oxygen diffuses into the blood. There is more carbon dioxide in
the blood than in the air, so this gas diffuses in the opposite direction.
Terminal
bronchiole
Pulmonary arteriole
(deoxygenated blood)
Pulmonary venule
(oxygenated blood)
Alveolar
duct
Alveolar
sac
Alveoli
Capillaries
Figure 4.2 Alveoli are found at the end of terminal bronchioles
Pulmonary ventilation
Examiner’s tip
Gas exchange always occurs
by diffusion. There is no active
transport, facilitated diffusion or
osmosis.
Revised
Pulmonary ventilation is the amount of air we inhale in 1 minute. It is
calculated as:
pulmonary ventilation = tidal volume × ventilation rate per minute
Typical values would be 0.5 litres for tidal volume and 14 breaths per
minute, giving a pulmonary ventilation of 7 litres per minute.
Tidal volume is the volume of air breathed in and out with each breath.
Ventilation rate is the number of breaths per minute.
42
Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
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A
B
C
4 The lungs and lung disease
Lung volumes are measured using a spirometer, which produces a trace
like the one in Figure 4.3. When we exercise, our breathing undergoes a
series of changes. Key points on the trace are labelled with the letters
A to E:
●A to B shows normal, tidal breathing while at rest.
●B to C shows the effect of exercise — breathing is deeper and more
frequent.
Examiner’s tip
●C to D shows a return to normal after exercise.
You may have been taught terms
●D shows the subject breathing out as far as possible.
such as inspiratory reserve volume
and expiratory reserve volume, but
● E shows the subject inhaling as much as possible.
they are not in the specification and
● So the difference in volume between D and E shows the vital
so cannot be tested in the exam.
capacity — the total usable lung volume.
● Residual volume is the air that must remain in the lungs.
D E
5
4
vital
capacity
tidal
volume
3
Volume
of air in
lungs/dm3 2
1
0
total
lung
capacity
residual
volume
0
30
60
Time/s
90
120
150
Figure 4.3 Changes in breathing during exercise
The mechanism of breathing
Revised
The lungs are spongy organs that simply fill with air and then empty
again. They cannot do this on their own because they have no muscle.
To inflate, they need the intercostal muscles and the diaphragm.
The mechanism of breathing is shown in Table 4.1. Inspiration is an
active process — it requires energy. Expiration is largely a passive process.
The lungs, diaphragm and intercostal muscles are all elastic. When
stretched, they tend to go back to their original shape.
Table 4.1 The mechanism of breathing
Stage
Breathing in (inspiration)
Breathing out (expiration)
1
The external intercostal muscles contract, pulling
the ribs up and out
The external intercostal muscles relax
2
The diaphragm muscles contract, flattening the
diaphragm
The diaphragm relaxes. The abdominal organs
(liver and intestines) push upwards
3
Their combined effect is to increase the volume
of the thorax
The volume of the thorax decreases
4
This lowers the pressure in the thorax to below
atmospheric pressure
The pressure inside the thorax increases
5
Atmospheric pressure forces air into the lungs
Air is forced out
Unit 1 Biology and disease
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4 The lungs and lung disease
The biological basis of lung disease
Pulmonary tuberculosis
Pulmonary tuberculosis (TB) is an infection that usually affects
the lungs and is caused by the bacterium Mycobacterium tuberculosis.
Transmission is by means of inhaling droplets from an infected person
if they cough or sneeze over a period of time. You won’t get TB if an
infected person coughs or sneezes on you just once.
The bacteria set up small pockets of infection in the lungs. The immune
system surrounds the infection and creates nodules called tubercles.
These reduce the surface area available for gas exchange. Symptoms of the
disease include:
● constant coughing that produces sputum/phlegm
● loss of appetite
● night sweats
● weight loss
Revised
Now test yourself
1 Suggest why hostels for the
homeless can be a common
source of new TB infections.
2 If you were to look down a
microscope at the organisms
that cause TB, would they have
a nucleus? Explain your answer.
Answers on p. 109
Tested
When antibiotics became available in the early 1940s, they were very
effective against TB and so the disease became rarer. However, resistant
strains of bacteria have since developed and TB now has to be treated
with a combination of antibiotics over a number of months.
TB is prevented by the BCG vaccine, which used to be recommended for
all UK children but now it is restricted to high-risk groups such as health
workers or people who have travelled from a country where the incidence
of TB is high.
Asthma, fibrosis and emphysema
Revised
Asthma is a condition in which the muscles lining the terminal
bronchioles constrict and over-produce mucus. Both of these responses
narrow the airway, making it particularly difficult to breathe out. The
narrow airway produces a wheezing sound during exhaling. In asthmatics,
an attack is brought on by an environmental trigger, which can be stress
or cold air, but is commonly an allergen such as house dust or animal fur.
Asthma affects lung function because it reduces air flow. It does not
damage alveoli and so there is no reduction in surface area.
Fibrosis is a response to tissue damage. When normal body tissue such
as lung, liver, bone or heart becomes damaged, the body responds by
producing connective tissue, commonly called scar tissue.
Emphysema is fibrosis of the alveoli. Lung damage results from long-term
exposure to irritants such as cigarette smoke and air pollution. When
the delicate alveolar walls become damaged and replaced by connective
tissue, the effects are:
● reduced surface area
● increased diffusing pathway due to the thicker walls
44
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(a)
4 The lungs and lung disease
Both of these combine to make gas exchange less efficient. Emphysema is
long-term, irreversible damage to the lungs.
(b)
Figure 4.4 (a) Healthy alveoli (b) Alveoli in a person with emphysema
Exam technique Graphs and patterns
There will always be questions about data in the exam.
Tables and graphs are nothing to be afraid of. In fact, they
often bring easy marks as the information is there for you.
Example question 1
Study the graph below, which shows the change in
the number of asthma patients and four common air
pollutants over a 20-year period. The air pollutants are
particle matter, sulphur dioxide, nitrogen oxide and
carbon monoxide.
[3]
Describe the pattern of incidence of asthma.
400%
all 4 main pollutants
asthma incidence
300%
200%
100%
0%
100%
200%
1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996
Year
Answer
You have to match up your answer to the number of
marks. If the graph is one straight line, there will usually
be 1 mark for writing something like ‘as X increases, Y
increases’. However, for a more complex graph like the one
here, there will often be 2 or 3 marks available. A good
answer is:
● There is a slow increase up to 1986.
● There is a rapid increase from 1986 to 1993.
● There is a fall after the peak in 1993.
Note that the question says ‘describe’. There is no need to
explain anything here.
Example question 2
[3]
Evaluate the claim that air pollution causes asthma.
Answer
Evaluate means to look at both sides. A good answer is:
● There is a correlation between the number of cars and
the incidence of asthma.
● However, a correlation does not mean a cause.
●Something else could be causing the increase, such as
more allergens.
Now test yourself
Tested
3 Explain the difference between the terms respiration and breathing.
4 List three ways in which the lungs are adapted to speed up the process of diffusion.
Answers on p. 109–110
Unit 1 Biology and disease
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4 The lungs and lung disease
Exam practice
1 The graph below shows the pressure and volume changes in the lungs during one breathing cycle.
+0.15
+0.10
+0.05
Pressure
0.0
in
alveoli/kPa
–0.05
–0.10
–0.15
0.50
0.40
Volume 0.30
of air in
lungs/dm3 0.20
0.10
0.0
0
1
2
Time/s
3
4
(a) During which time is the person:
(i)inhaling[1]
(ii)exhaling[1]
(b) Use the scale to work out the ventilation rate.[1]
(c) What is value of the tidal volume?[1]
(d) Work out the pulmonary ventilation in litres.[1]
2 An individual who suffers from emphysema will find exercise difficult, often getting out of breath simply by
walking upstairs. Explain why.[4]
Answers and quick quizzes online
Online
Examiner’s summary
By the end of this chapter you should be able to
understand:
4 The basic structure of the human gas exchange
system including the alveoli and bronchial tree.
4 The features of the alveolar epithelium as a surface
over which gas exchange occurs.
4 How the lungs are adapted for gas exchange.
46
4 Pulmonary ventilation as the product of tidal volume
and ventilation rate.
4 The mechanism of breathing.
4 The course of infection, symptoms and transmission
of pulmonary tuberculosis.
4 The effects of fibrosis, asthma and emphysema on
lung function.
Exam practice answers and quick quizzes at www.therevisionbutton.co.uk/myrevisionnotes
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