Task K: Introducing respiration to pupils
Slide 4.15
15 minutes
Show slide 4.15, which gives the instructions for this short plenary task.
Slide 4.15
Task K: Introducing respiration to pupils
• Work with a partner.
• You are going to plan part of a lesson for a Year 9 class.
• How would you use the first 10 minutes of the first lesson of a topic on respiration
to introduce the topic and identify or deal with some initial misconceptions? (You
have about five minutes to jot down ideas.)
• Be prepared to share your ideas with the other participants.
During the task, circulate to provide help as necessary.
After 5 minutes, ask pairs for their ideas. Record any that are particularly useful on
a flipchart.
Photosynthesis
T
20 minutes
Additional guidance
This session is in two parts: each should take about 10 minutes. During the first
part, you will explain those aspects of photosynthesis and leaf structure which are
important in Year 9. In the second part, participants look at a range of leaf crosssections to become more familiar with leaf cells and structure.
10 minutes
Definition of photosynthesis
Slide 4.16
Introduce this part of the session by explaining that, although the word
photosynthesis is not specified in the programme of study for Key Stage 2, pupils
will have been taught that plants need light and water to survive and grow. They will
probably have grown a variety of plants and undertaken some simple investigations
with them. It is likely therefore that many pupils will know the word photosynthesis
and some may have well-developed ideas about it. Show slide 4.16, which is the
relevant part of the Key Stage 2 programme of study.
Slide 4.16
Part of the Key Stage 2 programme of study
3
Pupils should be taught:
a the effect of light, air, water and temperature on plant growth;
b the role of the leaf in producing new materials for growth;
c that the root anchors the plant, and that water and minerals are taken in
through the root and transported through the stem to other parts of the
plant.
Slide 4.17
Show slide 4.17. Explain that this misunderstanding arises because respiration and
photosynthesis are taught at separate times. Teachers need to make explicit the
similarities, differences and links between the two processes.
95 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
C6H12O6 + 6O2
24
glucose
6CO2 + 6H2O
oxygen
carbon
dioxide
water
J
k
8
9
8
2 energy mo l –1
Slide 4.17
Respiration and photosynthesis – a common
misconception
• Pupils often believe that plant cells photosynthesise but do not respire.
glucose
25
enzyme
Ener gy
lactic acid
Explain that:
•
26
•
•
1
1
–
–
k
J
0
2
1 energym o l
Only plant cells with chlorophyll (i.e. green plant cells) photosynthesise. They
photosynthesise during the day when there is sunlight. (However, green plant
cells must respire throughout the 24 hours of the day, in order to provide
yeast
energy for the other
processes
which are happening in the cell.) The browns
glucose
ethanol
+ carbon dioxide
and reds of seaweeds and some shrubs and trees are due to the presence of
other photosynthetic pigments, which add to or replace chlorophyll.
Ener gy
27
28
All plant cells respire in order to provide the energy for the other processes
that are happening
in the cell.
enzymes
C6H12O6
2C3H6O3
Most
glucosebut not all plant
lacticcells
acid photosynthesise. Root and most stem cells that are
not green do not photosynthesise.
•
In a similar way to animal cells, respiration in plant cells releases energy from
glucose, usually in reaction with oxygen.
•
Green plant
cells produce glucose (for respiration) and oxygen from carbon
yeast
C
H
O
2Cutilising
2COenergy
transferred by sunlight, by the process of
dioxide
and
water,
6 12 6
2H5OH +the
2
glucose
ethanol
carbon
photosynthesis.
dioxide
Slide 4.18
210enkerJgymol –1
Show slide 4.18, which provides the word equations for photosynthesis and respiration.
Word equations for photosynthesis and respiration
Slide 4.18
Photosynthesis
29
carbon dioxide + water
enzymes
glucose + oxygen
light
Respiration
glucose + oxygen
Handout 4.19
enzymes
carbon dioxide + water
Ener gy
Make the following points, and explain that they and the word equations are on
handout 4.19.
•
Photosynthesis and respiration can be considered as opposite reactions. In
photosynthesis, water and carbon dioxide are the raw materials used by the
cell. Energy usually transferred by sunlight enables the reaction to take place
whereby glucose and oxygen are produced. In respiration, glucose and
oxygen are the raw materials used by the cell. Carbon dioxide and water are
produced, and energy is released to enable other reactions to take place.
•
Chlorophyll is needed for photosynthesis. It is located in small intracellular
structures called chloroplasts, which enable the reactions of photosynthesis to
take place in an ordered sequence. Participants should have seen chloroplasts
during session 1 but there will be a further opportunity to look at some at the
end of this session.
96 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
Handout 4.19
Photosynthesis
Photosynthesis
carbon dioxide + water
enzymes
glucose + oxygen
light
Respiration
glucose + oxygen
enzymes
carbon dioxide + water
Ener gy
•
Photosynthesis and respiration can be considered as opposite reactions. In
photosynthesis, water and carbon dioxide are the raw materials used by the
cell. Energy usually transferred by sunlight enables the reaction to take place
whereby glucose and oxygen are produced. In respiration, glucose and
oxygen are the raw materials used by the cell. Carbon dioxide and water are
produced, and energy is released to enable other reactions to take place.
•
Chlorophyll is needed for photosynthesis. It is located in small intracellular
structures called chloroplasts which enable the reactions of photosynthesis to
take place in an ordered sequence.
•
Some of the oxygen that green plants produce during photosynthesis is used in
respiration. The rest diffuses out of the plant into the atmosphere via the
stomata on the underside of leaves.
•
Glucose is one of the products of photosynthesis. In outline, it is rapidly
converted into the sugar sucrose (roughly, two glucose units linked together)
which has the property of being much less reactive than most other sugars.
Sucrose is further converted into starch for temporary storage in the leaf. It is
converted back into sucrose for subsequent transportation around the plant
because sucrose, although more reactive than starch, is soluble.
•
Through photosynthesis, plants produce much more glucose than is needed for
respiration. Some is used for other life processes such as growth, water uptake
from the roots and making new cells.
•
Many plants store starch in a variety of structures, all of which are associated
with reproducing more plants. These include seeds such as cereals, roots such
as carrots, and stem tubers such as potatoes. All these storage organs provide
excellent food for animals, including humans.
110 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
•
Some of the oxygen that green plants produce during photosynthesis is used in
respiration. The rest diffuses out of the plant into the atmosphere via the
stomata on the underside of leaves.
•
Glucose is one of the products of photosynthesis. In outline, it is rapidly
converted into the sugar sucrose (roughly, two glucose units linked together)
which has the property of being much less reactive than most other sugars.
Sucrose is further converted into starch for temporary storage in the leaf. It is
converted back into sucrose for subsequent transportation around the plant
because sucrose, although more reactive than starch, is soluble.
•
Through photosynthesis, plants produce much more glucose than is needed for
respiration. Some is used for other life processes such as growth, water uptake
from the roots and making new cells.
•
Many plants store starch in a variety of structures, all of which are associated
with reproducing more plants. These include seeds such as cereals, roots such
as carrots, and stem tubers such as potatoes. All these storage organs provide
excellent food for animals including humans.
Leaf cells and structure
10 minutes
A brief introduction (two minutes) leads on to task L in which participants look at a
variety of leaves under the microscope.
Explain that, through evolution, plant leaves have become very specialised to
maximise photosynthesis. A leaf can be considered as a plant organ with
specialised cells that support photosynthesis.
Slide 4.20
Show slide 4.20, which shows a typical leaf.
Say that:
•
A typical leaf is wide and flat to absorb as much sunlight as possible. The top
and bottom sides are different. One side is positioned facing the Sun. Leaves
are arranged on stems so that they shade each other as little as possible. They
are thin, to reduce the distance over which carbon dioxide has to diffuse into
the cells from the air (or water in the case of aquatic plants). They have a welldeveloped system of veins, which transports water to the cells and sucrose
away to be stored.
97 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
A typical green leaf
Slide 4.21
Much of this detail can be seen in a typical diagrammatic cross-section of leaf as
shown in slide 4.21. Remind participants that all diagrams of a leaf cross-section
are stylised to a greater or lesser extent, as they will see when they look at actual
leaf cross-sections later.
Diagram of cross-section of a leaf
Handout 4.22
Slide 4.20
Slide 4.21
Make the following points and tell participants that these, and other points about
leaves, are included on handout 4.22:
•
The palisade cells nearest the top side of the leaf have lots of chloroplasts.
•
Leaves have many pores (stomata, singular stoma) to let carbon dioxide in.
There are many air spaces (see diagram) in the leaf to allow the carbon dioxide
to diffuse easily into individual cells.
•
The mesophyll cells have a thin water layer on the outside, to allow carbon
dioxide to dissolve so that it can pass into the cells to the chloroplasts.
98 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
•
Water evaporates from this layer and diffuses out of a leaf through the stoma.
Many plants have modified stomata or leaf surfaces to reduce this water loss.
Handout 4.22
The leaf: an important
plant organ
•
A typical leaf is wide and flat to absorb as much sunlight as possible. The top
and bottom sides are different. One side is positioned facing the Sun. Leaves are
arranged on stems so that they shade each other as little as possible. They are
thin, to reduce the distance over which carbon dioxide has to diffuse into the
cells from the air (or water in the case of aquatic plants). They have a welldeveloped system of veins, which transports water to the cells and sucrose
away to be stored.
•
The palisade cells nearest the top side of the leaf have lots of chloroplasts.
•
Leaves have many pores (stomata, singular stoma) to let carbon dioxide in.
There are many air spaces (see diagram) in the leaf to allow the carbon dioxide
to diffuse easily to individual cells.
•
The mesophyll cells have a thin water layer on the outside, to allow carbon
dioxide to dissolve so that it can pass into the cells to the chloroplasts.
•
Water evaporates from this layer and diffuses out of a leaf through the stoma.
Many plants have modified stomata or leaf surfaces to reduce this water loss.
111 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
Task L: Cross-sections of leaves
8 minutes
The last eight minutes of this session are available for participants to look at some
cross-sections of leaves under the microscope and see if they can identify and
name the various cells. This helps to consolidate the microscope work they did in
session 1 and gives them a feel for the range of specialist cells and the part they
play in photosynthesis.
Reproduction
18 minutes
Introduce this final part of the session by explaining that pupils in Year 9 need to
build on their earlier knowledge of reproduction and cells. They need to recognise
that an organism possesses features that are inherited from information contained
in the male and female reproductive cells, which join during fertilisation. Achieving
the Year 9 yearly teaching objectives is important to prepare pupils for the genetics
taught in more detail during Key Stage 4.
Handout 4.23
Read out the poem ‘Where do babies come from?’ (handout 4.23).
Where do babies come from?
Handout 4.23
I’m sure when you were very young,
you used to say to dad or mum,
Mummy? Daddy? Where do babies come from?
Well your mum and dad reply
and suddenly they go all shy.
Well my dear you’ll learn some day
how you have turned out this way.
A little creature called a sperm
which lives inside a man
will swim towards a tiny egg
as fast as it possibly can.
The egg just waits inside a woman
waiting for a sperm.
It really is quite complicated
there’s quite a lot to learn.
The sperm with his little wiggly tail
and its pointy head
finds its way into the egg
while your parents are in bed.
Slowly then the egg splits and grows
as large as it can go.
Then forms into a sort of baby
called an embryo.
The embryo then grows and grows
and gets all its bits and pieces.
Then it grows a little bit bigger
and this is called a foetus.
In the next nine months your mum gets fat,
starts buying the baby clothes and hats.
She then goes into hospital
to wait for the baby to be born.
She screams and shouts
while the baby comes out, and daddy holds her hand.
Then you give it the name you want
and then you can take it home!
The above poem is reproduced with kind permission of the ASE. ‘Where do babies
come from?’ is included in Science is like a tub of ice-cream – cool and fun, edited
by Rosemary Feasey and published by the ASE (2001). (ISBN 086357 3223)
112 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
99 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
28
C6H12O6
yeast
2C2H5OH + 2CO2
glucose
ethanol
carbon
dioxide
Photosynthesis
J
–
k
m
0
o
1
l
2 energy 1
Handout 4.19
Photosynthesis
29
carbon dioxide + water
enzymes
glucose + oxygen
light
Respiration
glucose + oxygen
enzymes
carbon dioxide + water
Ener gy
•
Photosynthesis and respiration can be considered as opposite reactions. In
photosynthesis, water and carbon dioxide are the raw materials used by the
cell. Energy usually transferred by sunlight enables the reaction to take place
whereby glucose and oxygen are produced. In respiration, glucose and
oxygen are the raw materials used by the cell. Carbon dioxide and water are
produced, and energy is released to enable other reactions to take place.
•
Chlorophyll is needed for photosynthesis. It is located in small intracellular
structures called chloroplasts which enable the reactions of photosynthesis to
take place in an ordered sequence.
•
Some of the oxygen that green plants produce during photosynthesis is used in
respiration. The rest diffuses out of the plant into the atmosphere via the
stomata on the underside of leaves.
•
Glucose is one of the products of photosynthesis. In outline, it is rapidly
converted into the sugar sucrose (roughly, two glucose units linked together)
which has the property of being much less reactive than most other sugars.
Sucrose is further converted into starch for temporary storage in the leaf. It is
converted back into sucrose for subsequent transportation around the plant
because sucrose, although more reactive than starch, is soluble.
•
Through photosynthesis, plants produce much more glucose than is needed for
respiration. Some is used for other life processes such as growth, water uptake
from the roots and making new cells.
•
Many plants store starch in a variety of structures, all of which are associated
with reproducing more plants. These include seeds such as cereals, roots such
as carrots, and stem tubers such as potatoes. All these storage organs provide
excellent food for animals, including humans.
110 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003
Handout 4.22
The leaf: an important
plant organ
•
A typical leaf is wide and flat to absorb as much sunlight as possible. The top
and bottom sides are different. One side is positioned facing the Sun. Leaves are
arranged on stems so that they shade each other as little as possible. They are
thin, to reduce the distance over which carbon dioxide has to diffuse into the
cells from the air (or water in the case of aquatic plants). They have a welldeveloped system of veins, which transports water to the cells and sucrose
away to be stored.
•
The palisade cells nearest the top side of the leaf have lots of chloroplasts.
•
Leaves have many pores (stomata, singular stoma) to let carbon dioxide in.
There are many air spaces (see diagram) in the leaf to allow the carbon dioxide
to diffuse easily to individual cells.
•
The mesophyll cells have a thin water layer on the outside, to allow carbon
dioxide to dissolve so that it can pass into the cells to the chloroplasts.
•
Water evaporates from this layer and diffuses out of a leaf through the stoma.
Many plants have modified stomata or leaf surfaces to reduce this water loss.
111 | Strengthening teaching and learning of cells | Notes for tutors | Session 4
© Crown copyright 2003