B2.1 Supplying the cell
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B2.1 Supplying the cell
Mathematical learning outcome:
BM2.1i use percentiles and calculate percentage gain and loss of mass
Assessable content statements:
B2.1a explain how substances are transported into and out of cells through diffusion, osmosis and active transport to include: examples of substances moved, direction of movement, concentration gradients and use of the term water potential (no mathematical use of water potential required)
B2.1b describe the process of mitosis in growth, including the cell cycle to include: the stages of the cell cycle as DNA replication, movement of chromosomes, followed by the growth of the cell
B2.1c explain the importance of cell differentiation to include: the production of specialised cells allowing organisms to become more efficient and examples of specialised cells
B2.1d recall that stem cells are present in embryonic and adult animals and meristems in plants
B2.1e describe the functions of stem cells to include: division to produce a range of different cell types for development, growth and repair
B2.1f describe the difference between embryonic and adult stem cells in animals
A clear animation on mitosis in detail. Includes a pause and play button.
Can be used by learners as a revision tool or as a class.
Learners are provided with 4 specialised cells. They are to look at the descriptions provided and match them with the correct cells.
It is an introduction to specialised cells so should be done at start.
The animation looks at DNA replication and the part enzymes play and complimentary base pairing.
It is a PowerPoint and can be used as part of the lesson.
Learners to produce an information leaflet for patients explaining how stem cells can be used in their treatment.
To include following points:
- What is a stem cell?
- How do stem cells work?
- What is an adult stem cell?
- What is an embryonic stem cell?
- How do they differ?
Teaching mitosis in a practical way making it visual and engaging at the same time.
The mitosis with shoes activity is a great way.
Mitosis and the cell cycle (B2.1 b) are difficult topics for learners to understand. There are many pictures in books, which show the process but require learners to memorise them. Get learners physically involved by using pipe cleaners as chromatids and string as spindle fibre and get them to model it (Learner resources 2 and 3). This can also be done with DNA replication by using toothpicks and marsh mellows to make the double helix and then showing it separating to copy.
Learners believe that the difference between a child cells and an adult cells is that the adult cells are bigger, due to their increased size. The idea that the organism has more cells is new to some learners. Pose the question to learners ‘why do cells not just increase in size?’ and then carefully using illustrations of a big cell and a small cell, to make it more visual explain that the centre of bigger cells is further away from the membrane than smaller cells. This means that the nutrients have to travel further to get to the centre of the cell and opposite for smaller cells. More importantly the waste products of respiration have further to travel also. Therefore cells need to reproduce for an organism to get bigger and also specialise.
Specialised cells (B2.1 c), can be introduced by giving learners the specialised cells card sort and getting them in pairs to arrange them. The following can illustrate why cells become specialised. Learners can be given some plasticine and told to make 2cm squares from the lump. The learners must firstly do the task on their own – then they must do it as part of a production line (e.g. with one one tearing off plasticine from the large ball into appropriate sizes, one rolling the pieces into balls and the final one squaring them off ). Talk about the division of labour on production lines being more efficient as each person gets very good at their job. This could be done as a short activity during the start of a lesson.
A class practical or even a demo of a raw egg in water and syrup to show osmosis occurring (B2.1 a). Serendip Studio contains a premade worksheet to allow learners to record their findings. It also provides more details for teachers.
To introduce stem cells (B2.1 d,e,f ) get learners in pairs and ask them to write a few sentences on how the following words are linked. Write the words in no specific order: stem cells, red blood cell, nerve cell, differentiation adult stem cell, embryonic stem cell, growth, repair. This should lead to a group discussion. A virtual lab, allows you to create your own stem cells. “Cloning Cauliflower” experiment is a fascinating hands on technique at looking at stem cells.
Common misconceptions or difficulties learners may have
Learners may find it difficult to distinguish between adult and embryonic stem cells. Allow learners to read the case study about adult stem cell and then the case study about embryonic stem cells question learners: what did they both have in common? How are they different? Are there any ethical issues?
Mitosis and cell cycle is a topic, which contains many misconceptions. Using the approach in this delivery guide by making it more visual can make it easier for learners to understand.
Learners also have the misconception as to what a chromosome is. A piece of DNA one of the 46 is a chromosome, the classic replicated X form is also a chromosome. When these separate during anaphase these are now magically chromatids (even though they are structurally the same as the first chromosome mentioned) these chromosomes then transform into chromosomes again when they are enclosed by a nuclear envelope.
Conceptual links to other areas of the specification – useful ways to approach this topic to set learners up for topics later in the course
B2.1 a – Osmosis and diffusion are processes required in topics B2.2 a,b which looks at exchange surfaces and blood. The knowledge of B2.1 d,e,f stem cells can enable a better understanding of animals breeding B6.2 c.
The knowledge and understanding of DNA replication (B2.1 b) builds on the work covered previously in section B1.2 a,b,c on DNA structure. Using the activity, which follows on from mitosis with shoes, can show DNA replication.
A variety of class practicals and demonstrations that can be undertaken within the classroom.
Method and worksheet questions are provided.
Approaches to teaching the content
The topic lends itself to many engaging activities that can be used as starter or plenaries. Stem cells use some of the most pioneering techniques in modern time. Many stem cell applications are being developed from health care to medical drug production. Many approaches can be taken when teaching it in context.
Mitosis can be used to explain asexual reproduction in our very own gardens or even growth and repair.
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