Download Specification Sections AQA GCSE Biology 3

Teacher’s notes
Biology
2
Cells, tissues and organs
 Specification sections
AQA GCSE Biology B2.1, B2.2.
Overview
In 1665 Robert Hooke looked down a simple microscope and saw the small units in bark which he
called ‘cells’ and from this time cell theory has been expanding. This chapter begins by looking at the
subcellular components of animal cells before introducing plant, yeast and bacterial cells with their
additional features. Cell specialisation leads into tissues, organs and systems so the student gains a
complete overview of the organisation of plants and animal.
The final section focuses on the cell membrane, and looks at how dissolved substances move into
and out of cells. The processes of diffusion and its importance in living organisms is accompanied by
some practical investigations.
Students can use the Summary sheet to check their progress.
Timings
This is a relatively short chapter that can be covered in four lessons – about 4 hours.
Misconceptions
 The material on cell structure is fairly straightforward. It is difficult to explain some of the
functions as, at this time, the students have not studied many of the processes that are controlled
by organelles.
 Students often struggle to remember that diffusion is a passive processes and do not require
cellular energy but is dependent upon concentration gradient.
 Concentration gradients cause many students problems; explaining the concept using plenty
of diagrams and interactive animations available on the recommended internet sites may
help..
Skills
 Carrying out careful observations of diffusion.
 Collecting experimental or analysing secondary data.
 Reviewing experimental methods such as variables that can be controlled, ranges of values, etc.
Prior knowledge
This chapter revises and develops the following areas from Key Stage 3:
 Cells are the basic units of life and are organised into tissues from which organs are made.
 How to use a microscope safely.
 The differences between plant and animal cell structure..
 That there are different types of cell, adapted for different functions.
Assessment opportunities
Pre-test
Formative
Internal
Summative
Question 1 can be used as a pre-test for the chapter.
Questions 2–18 provide formative assessment opportunities.
Worksheet: ‘Delving deeper into diffusion’ (Higher extension) provides questions to promote
understanding of observational skills and a critical method of assessing scientific data.
Use the Exam questions on page 161 or Biology Unit 2 Interactive questions
Progression
Separate Sciences and AS level
The following ideas and knowledge are developed in GCSE Biology and AS level.
 How dissolved substances move by diffusion, osmosis and active transport, and how exchange
surfaces are adapted to maximise effectiveness.
 How red blood cells are specialised by having no nucleus and being packed with haemoglobin.
© 2010 Hodder Education
AQA GCSE Biology Teacher’s notes | 1
 How exchanges in the kidney take place, and sugar and dissolved ions can be absorbed against a
concentration gradient.
The following ideas and knowledge are developed in AS Biology and Human Biology:
 The structure of plant and animal cells and the use of a microscope; features and functions: cell
wall and plasma membranes, nucleus, chloroplasts, mitochondria, ribosomes, Golgi apparatus and
others.
 Diffusion and the factors that determine its rate: water potential; active transport.
 Cell differentiation.
Careers
This chapter provides foundation knowledge for all aspects of the health and medical professions.
Further links
ICT
Numeracy
Literacy
Students use the internet to look at animations of internal cell structure and diffusion.
Students plot and interpret graphical data on rates of osmosis.
Students take part in a group discussion on topics from the Student’s Book and can establish forums
on the intranet.
Scientific theories, models and evidence
 With reference to the development in our understanding of cells, students appreciate that scientific
ideas develop over time.
 Students apply knowledge of structure of different cells to suggest function.
5.1–5.4
/ 1.1–1.4
How do cells perform different functions?
AQA GCSE Biology pages 85–92 or
AQA GCSE Additional Science pages 5–12
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 2
Lesson plan
Timescale
Lesson 1
Objective
Resources
Starter
Main activity
This section in the Student’s Book will require three lessons (approximately three hours) plus three
homeworks.
Subcellular organelles
Students will study the development of cell theory and the structure and function of subcellular
organelles.
 Prepared information sheets on the scientists named on the Worksheet ‘Cell theory timeline’
(Activity).
 Preprepared diagrams.
 Materials for the HSW: Activity for the plenary.
 Students read the introductory paragraph on page 85 in AQA GCSE Biology or page 5 in AQA
GCSE Additional Science.
 Ask students why we can’t see individual cells with the naked eye – what do we need in order to
see them?
 A home is a unit – what do we need to keep that unit going. Energy, fuel, warmth, air, water, stairs
or corridors. If the cell is the basic unit of the organism how are some of the requirements
provided and maintained?
 Examine a model of a cell or large size diagram. Identify the structures starting with the nucleus
and establish what they can remember. At this stage students should be able to expand on ideas of
‘controls the cell’ and be able to answer the following questions.
How does the nucleus regulate cell activities?
How does the nucleus control cell division?
 Go through each organelle and create an annotated diagram using whatever technology you have
available: the students could use this as the foundation for their notes – time is saved if the
students are given large size diagrams without labels to annotate.
 Use questions 4 and 5 on page 87 in AQA GCSE Biology or page 7 in AQA GCSE Additional
Science to help students realise that not all animal cells are identical.
Plant cells have additional structures
 Hand out unlabelled diagrams of a plant cell and ask students what organelles they recognise that
were present in the animal cell. These should be labelled only.
Plenary HSW Activity: A fun activity which can be a team race is building a plant cell from household waste.
Gather sufficient resources such as boxes, cartons , string or cotton , paperclips to be used as clips etc.
This can be either in 2D or 3D and is an opportunity to let the more creative, and possibly less
academic, pupils shine. Explaining the models at the end will reinforce the lesson. The models can be
used for the starter of the next lesson to recap.
Outcomes Most students should:
 have a sound understanding of the roles of the nucleus.
 have a sound understanding that the different functions within the cell are carried out in
organelles.
Lesson 2
Objective
Resources
Starter
Main activity
Yeast and bacteria
Students should be able to recognise and describe the differences between animal, plant, bacterial and
yeast cells.
 Electron microscopy pictures of different cell types, downloaded from websites (try Google
images or www.cellsalive.com).
 Prepared A3 sheets with function of individual cell types in large font to hold up to class (or
PowerPoint slides if an interactive whiteboard is available).
Use one or more of the plant cell models made last lesson as a quick recap of cell structures.
 Show a picture of a yeast cell – what does it have in common with and how does it differ from a
plant cell?
 Annotate diagrams. Inform students that this is also the basic structure of a fungal filament Figure
3.25 on page 57 of AQA GCSE Biology and AQA GCSE Science.
 Show a bacterial cell diagram What is missing that you saw in plant and animal cells? Annotate
the diagram.
 Question 7 on page 89 in AQA GCSE Biology or page 9 in AQA GCSE Additional Science. Point
out the mesosome (no need to name this), the lack of a nucleus and the special cell wall.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 3
Cell specialisation
Plenary
Outcomes
Homework
Lesson 3
Objective
Resources
Starter
Main activity
Plenary
Homework
Outcomes
 Questions 4 and 5 showed that not all cells have the same number of organelles, additionally cells
have specialised shapes for carrying out specific functions. Read ‘Cell specialisation’ on on pages
88–90 in AQA GCSE Biology or pages 9–10 in AQA GCSE Additional Science.
 Show pictures of specialised cells and discuss their structure and physiology or use the examples
in the text.
 Worksheet ‘Matching cells to their jobs’ (Activity). Ask students to complete the matching
exercise to fit each cell type with its function and then answer the questions that follow.
 Using pre-prepared A3 sheets printed with the function of individual cell types, revise cell type
and function. Hold up each function and ask students to write the name of the cell that carries out
that function on a piece of scrap paper and hold it up. Award points for the first answer, and see if
any student can win three or more points.
 Ask students to name the one type of cell in the body that does not have a nucleus. Discuss, in
very simple terms, how this relates to the cell’s function.
 Ask students to discuss what the weirdest looking cell in the body is. Examples could include
nerve cells, cells from the wall of the small intestine, or macrophages; provide some internet
pictures to look at for fun.
All students should:
 understand that cells may be specialised to carry out a particular function.
 be able to relate the structure of a specialised cell to its function.
 Homework question 2 on page 97 of AQA GCSE Biology or page 17 of AQA GCSE Additional
Science.
 Learn Table 5.1/1.1.
Organisation at tissue, organ and system levels
Students should:
 appreciate that specialised cells with particular functions are normally arranged as tissues.
 see that organs can contain more that one type of specialised tissue and that these perform related
functions.
 appreciate that organs are part of systems.
 Diagrams needed showing tissues in organs. Microscope slide (with projector microscope) or wall
posters.
 Preprepared diagrams for students notes.
Do a ‘Name the organs’ quiz using models or diagrams. Use the mini-whiteboards for this.
 Examine Figures 5.10–5.12 on page 90 of AQA GCSE Biology or Figures 1.10–1.12 page 10 of
AQA GCSE Additional Science.
 Show diagrams of tissues such as gastric epithelium, muscle, etc. where there are many cells of the
same shape. Ask students what they notice about the cells making up a tissue. What are the
features of the cells in each tissue and how are they suited to their function? Large surface area
and thin epithelium are common features to show.
 Move onto the stomach as an organ. Examine the section of the stomach wall and locate the
muscle tissue, the glandular tissue and the epithelial tissue. What is the function of each? Do they
all contribute to digestion in the stomach? How? Students should produce and annotate a plan
diagram of the stomach.
 The stomach is not in isolation. How does it fit into the digestive system? Use Figure 5.14 on page
90 of AQA GCSE Biology or Figure 1.14 page 10 of AQA GCSE Additional Science.
 Label and annotate a pre-prepared diagram.
 Plants are also organised. Examine the tissues shown in Figure 5.15 on page 92 of AQA GCSE
Biology or Figure 1.15 page 12 of AQA GCSE Additional Science.
Complete question 11. Rehearse the parts of other body systems how will these all function together
in an Olympic athlete?
Questions 9–13 on pages 91–2 of AQA GCSE Biology or pages 11–12 of AQA GCSE Additional
Science.
All students should:
 be able to relate structure to function.
 be able to regard the body/all organisms as a series of interrelated systems.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 4
Answers to Test yourself questions (pages 85–92 or pages 5–12)
1. Cells are the smallest individual units in living things. A living organism is built from millions
of these individual units, all working together.
2. The resolving power of Hooke’s microscope – he could not see anything smaller than a whole
cell. (Also, the cells he saw were dead cells – just the cell wall.)
3. Robert Brown noticed that cells had something inside them – this was important because he saw
the same ‘blob’ inside cells taken from different parts of the plant. After Brown’s work,
scientists began to try and find out more about the insides of cells, and to work out what the
functions of cells might be.
4. Mitochondria.
5. Ribosomes.
6. Animals have other forms of support structure such as cartilage, bone or hydrostatic skeleton.
7. Complete from text.
8. Yes.
9. Mitochondrion, chromosome, bacterial cell, cheek cell, plant cell, heart, digestive system.
10. Xylem for transport of water and mineral ions, and phloem for transport of sugars.
11. Shape, TISSUE; tissues, ORGAN; SYSTEMS.
12. Palisade mesophyl.
13. Nucleus; chloroplasts; cell wall; mitochondrion, vacuole.
5.5 / 5.4
How do dissolved substances move into
and out of cells?
AQA GCSE Biology pages 93–6 or
AQA GCSE Additional Science pages 13–16
Scientific theories, models and evidence
 Students will look at the criticisms of opposers to Darwin’s hypothesis, including those of his
contemporary scientists who claimed that evidence was not available.
 Using and making models: students will examine evolutionary trees and some methods used to
construct them.
Lesson plan
Timescale
This section should take about one hour (one lesson) plus one homework.
Objective Students study the process of diffusion and look at examples of where and when it is important in
animal and plant cells. Students should understand the factors which change the rate of diffusion.
Resources Pre-prepared diagrams showing diffusion.
Starter  Set up some demonstrations of diffusion and ask students to observe them. Possibilities include a
potassium permanganate crystal in the bottom of a large beaker of water, a tea bag in a beaker of
water, perfume or other strong smelling substance left at the end of the room.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 5
 Generate a class discussion on what is happening.
 HSW: Practical skills ‘Diffusion’. Students should set up the demonstration on page 95 of AQA
GCSE Biology or page 15 of AQA GCSE Additional Science. Demonstrate how to test for
glucose either using clinitest strips or Benedict’s solution, and test for starch.
Main focus of the investigation: Care in setting up – no glucose should be on the outside of the
visking tubing.
Making a simple series dilution.
Considering the volumes needed and using appropriate sizes of
measuring cylinder.
Monitoring for glucose and recording results on a table.
Main activity  Explain the process of diffusion in detail using pre-prepared diagrams, animations and the
Student’s Book (there are many internet and CD-ROM animations available, e.g.
www.sciencezone.org.uk/work2.htm).
 Bring the class together to discuss the results of the demonstration they set up in terms of the
process of diffusion, and consolidate learning, using animations again if required.
 Ask students to answer Question 14 on page 94 of AQA GCSE Biology or page 14 of AQA GCSE
Additional Science.
 Students complete the Worksheet ‘Diffusion in the lungs’ (Activity).
 Examine the leaf diagram Figure 5.21 on page 96 of AQA GCSE Biology or Figure 1.21 on page
16 of AQA GCSE Additional Science and use this as an example to consolidate concentration
gradient.
Plenary Look at examples from animals and plants of where and when diffusion is important, for example:
 diffusion of oxygen across the membrane of the lungs into the blood
 diffusion of sugars from cells in the leaf to the phloem for transport to other parts of the plant
 diffusion of digested food molecules through the wall of the small intestine,
and use these to reinforce the summary on page 96 of AQA GCSE Biology or page 16 of AQA
GCSE Additional Science. The Personal Tutor ‘Respiration’ can also be used here.
Outcomes All students should:
 understand that diffusion is the movement of particles from a region of high concentration to a
region of lower concentration.
 understand that movement of particles occurs to equalise the concentration of particles in the
different regions.
 know that gases and particles in solution can diffuse.
 recall some examples of how diffusion occurs in the human body, e.g. diffusion of oxygen into
cells for respiration.
 understand that diffusion can occur through a partially permeable membrane.
Homework  Students complete the Worksheet ‘Delving deeper into diffusion’ (Higher extension).
 Or Homework questions 3 and 4 on page 97 of AQA GCSE Biology or page 17 of AQA GCSE
Additional Science.
Answers to Test yourself questions (pages 94–6 or pages 14–16)
14. Oxygen in, carbon dioxide out.
15. Diffusion is the movement of dissolved oxygen from the higher concentration in the blood,
through the muscle cell membrane and cytoplasm to the mitochondrion. The oxygen is moving
down the concentration gradient. The concentration gradient exists because the mitochondrion is
continually using up the oxygen for respiration.
16. The lungs have a very large surface area as a result of the very large numbers of alveoli, the
surface of the alveoli are moist, the lungs are ventilated, i.e. breathing movements continually
exchange the air, the alveoli have a thin epithelium.
17. Diffusion is a passive process dependent on concentration gradient. Concentration gradient
means that there is a higher number of molecules or ions per unit volume in one region
compared to an adjacent region and so the molecules spread out.
Answers to HSW: Practical ‘Diffusion’ (page 95 or page 15)
Glucose would be expected in the beaker containing the visking tubing with the highest glucose
concentration. Hopefully the class results show that the rate of diffusion is proportional to the
concentration gradient.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 6
Starch should not be detected as the molecules (actually it is a polymer) are too big to pass
through the small pores in the visking tubing.
Answers to Homework questions (page 97)
1.
System
Digestive system
Nervous system
Transport system
Urinary system
Female reproductive system
Organs
Mouth, Oesophagus, Stomahc, Pancreas, Liver, Samll
intestive, Large intestine, Rectum
Brain, Spinal cord, Sensory and motor nerves, Receptors
Heart, Arteries, Veins, Capillaries
Kidney, Bladder
Ovary, Uterus
2. a) Central vacuole, mitochondria, ribosomes, cell membrane , cell wall (although made of
different materials) nucleus, cytoplasm.
b) Cell wall of plant cell made of cellulose, cell wall of yeast cell not cellulose, yeast does not
have chloroplasts, storage material in plant cells is starch but lipid droplets in yeast.
3. i)large surface area
ii) oxygen concentration kept high by ventilation
iii) oxygen dissolves on moisture
iv) thin epithelium of alveoli and capillaries
v) rich capillary network
vi) blood constantly taking away oxygen maintains concentration gradient
vii) red cells (with haemoglobin) pick up oxygen.
4. a) A from visking tubing to beaker
B from beaker to visking tubing
C both concentrations are equal so there will be no net movement
b) A.
5. a) Diffusion or active transport through the membrane of the small intestine and into the blood
capillaries in the villi, along the hepatic portal vein to the liver, from the liver hepatic vein to
the vena cava, through the RHS of heart to lungs, to LHS of heart to great aorta, through
artery to pancreas, diffusion from blood capillaries into cells of pancreas.
b) The insulin diffuses into blood capillaries around the cells which produce it and is transported
in the plasma.
c) Ribosomes.
d) In the DNA in the nucleus.
e) Aerobic respiration.
Answers to Exam questions (page 161)
1. a) Mitochondrion. (1 mark)
b) Ribosome. (1 mark)
c) Long (1 mark), so there is direct connection to carry the impulse to the target organ
(1 mark); or branching dendrites (1 mark) can make many connections with other neurones
(1 mark)
2. a) Line from centre of alveolus to capillary. (1 mark)
b) Alveoli have a large surface area; close contact between capillary and alveolar membrane;
and both have a thin epithelium giving a short diffusion distance; blood continually removing
oxygen maintaining the concentration gradient. (3 marks)
c) Diagram of a mitochondrion. (1 mark)
d) Cells in the pancreas make the protein insulin and these cells have many ribosomes. (1 mark)
e) The nucleus contains the code for the proteins (as the sequence of base triplets on the DNA).
(1 mark)
Worksheet ‘Cell theory timeline’ Activity
Resources
Use the internet or A level textbooks or reference books to research and prepare some brief
information on the scientists listed on the student worksheet. Wikipedia (en.wikipedia.org/) has
entries on all the men and you could just print out the Wikipedia page (or first part for Hooke and
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 7
Leeuwenhoek). Half an A4 page per person should be plenty: include dates, main work done,
contribution to cell theory and a photograph if possible. Print out sufficient copies for size of class.
Worksheet ‘Matching cells to their jobs’ Activity
Introduction
Resources
Answers
Students do not need to recall details of different specialised cells, only to be able to use additional
information which is given to them, i.e. to relate structure to function. Although the difference
between the structure of animal and plant cells is not encountered in the Student’s Book or lesson
plans till later, the simple function of plant cells for support is mentioned here as one example of cell
function.
 Use the internet to download additional pictures of different cell types. (Try Google images or
www.cellsalive.com.) Print out copies for class discussion or display in colour on interactive
whiteboard, if available.
 Prepare A3 sheets or PowerPoint slides (if interactive whiteboard available) with function of
individual cell types in large font to hold up/display to class.
In order from the top, the diagrams show: plant cell, intestinal epithelial cell, muscle cell, nerve cell,
sperm cell.
Taking it further
1. Skeletal muscle cells are used for movement and need to use a lot of energy. Hence they need
lots of mitochondria to release that energy.
2. The folds (villi and microvilli) increase surface area. The cell absorbs food from the intestine,
and a larger surface area allows absorption to be more efficient.
3. Sperm need a tail to swim to egg. Egg needs a large food store to nourish the embryo after
fertilisation.
Worksheet ‘Diffusion in the lungs’ Activity
Questions 5–7 could be omitted for Foundation-tier students.
Answers
1. Concentration of carbon dioxide goes down as we breathe out, concentration of oxygen goes
up as we breathe in.
2. Concentration of oxygen greatest in alveoli when you have breathed in fully.
3. Oxygen diffuses across the wall of the alveolus and across the wall of the capillary and enters
the blood.
4. Carbon dioxide diffuses across the wall of the capillary and the wall of the alveolus and enters
the air space of the alveoli.
5. The thickness of the wall of the capillary and the thickness of the wall of the alveolus.
6. Someone with cystic fibrosis produces a lot of mucus that they can’t get rid of. This lines the
alveoli and makes a much thicker barrier for oxygen and carbon dioxide to diffuse through.
Cystic fibrosis sufferers are also very prone to lung infections and the lung tissue can become
scarred. This also thickens the tissue and causes the distance for diffusion of oxygen and
carbon dioxide to be greater. Both these effects make it more difficult to carry out efficient
gas exchange.
7.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 8
Worksheet ‘Delving deeper into diffusion’ Higher extension
This is an extension worksheet, looking at the effect of temperature.
Answers
1. About 37C in fresh water.
2. Temperature and salinity.
3. In cold seas – the rate of diffusion is lowest in the sea water at temperatures below 10C. The
coating would last longest under these conditions.
4. In warm freshwater lakes in tropical areas. The rate of diffusion is generally higher in fresh
water, but it is highest when the temperature of the water is over 30C.
© 2011 Hodder Education
AQA GCSE Biology Teacher’s notes | 9