This document covers key concepts in cell biology, including the differences between prokaryotic and eukaryotic cells, the structure and function of animal and plant cells, and the processes of cell differentiation and specialization. It also discusses microscopy techniques, particularly light and electron microscopes, and introduces stem cells and their potential medical applications. Finally, it summarizes the cell cycle, methods of transport across cell membranes, and adaptations of fish for efficient gas exchange.

1. GCSE Biology
AQA (grade 9 – 1)

2. Cell biology
• What’s the difference between Prokaryotes or Eukaryotes?
• Plants and animal cells – subcellular structures.
• Bacterial cells are much smaller, bacteria are prokaryotes.
• Microscope – light and electron
• Cell differentiation and specialisation.

3. Organisms can be Eukaryotes or Prokaryotes
Eukaryotes
• Eukaryotic cells are
complex
• All animal and plant cells
are Eukaryotic.
• Eukaryotes are organisms
which are made up of
Eukaryotic cells.
Prokaryotes
• A Prokaryote is a
prokaryotic cell (it’s a
single-celled organism)
• Prokaryotic cells are
smaller and simpler.

4. Animal and plant cells
• Draw both and an animal cell and fully label it.
• What is the function of each subcellular structure.
• What does a bacterial cell look like?

5. Animal cell

6. Plant cell

7. Bacterial cells

8. Microscopy
Light Microscope
• It uses light and lenses
to form an image of a
specimen and magnify it.
• They let us see
individual cells and large
subcellular structures,
like nuclei.
Electron Microscope
• Use electrons instead of light to
form an image
• They have a much higher
magnification than light
microscopes.
• They have a higher resolution
(sharper image)
• Can be used to see smaller things in
more detail, like the internal
structures of mitochondria and
chloroplasts.

9. Cell differentiation and specialisation
• Differentiation is the process by which a cell changes to
become specialised for its job.
• As cells change, they develop different subcellular structures
and turn into different types of cells. This allows them to
carry out specific functions.
• In most animal cells, differentiation takes place at an early
stage. After this, the ability to differentiate is then lost.
• However, lots of plant cells don’t ever lose this ability.
• The cells that differentiate in mature animals are mainly used
for repairing and replacing cells, such as skin or blood cells.

10. Stem cells
• Stem cell – undifferentiated cell is capable of giving rise to many
more cells the same type, and from which certain other cells can
arise from differentiation.
• Stem cells from human embryos can be cloned and made to
differentiate into most different types of human cells.
• Stem cells from adult bone marrow can form many types of cells
including blood cells.
• Meristem tissue in plants can differentiate into any type of plant
cell, throughout the life of the plant.
• Treatment with stem cells maybe able to help conditions such as
diabetes and paralysis.

11. Stem cells maybe able to cure many diseases
• Stem cells from the bone marrow of a healthy person can
replace faulty blood cells in the patient who receives them.
• Embryonic stem cells could be used to replace faulty cells in sick
people e.g. insulin producing cells for people with diabetes, nerve
cells for people paralysed with spinal injuries.
• In therapeutic cloning, an embryo could be made to have the
same genetic information as the patient. Stem cells produced
would contain the same genetic information as the patient and so
wouldn’t be rejected by the patient’s body.
• Possible risks – If stem cells grown in the lab are contaminated
with a virus, it could pass on to the patient.

12. Some people are against stem cell research
• Against – human embryos shouldn’t be used for experiments
since each one is a potential human life.
• For – curing existing patients who are suffering is more
important than the rights of embryos.
• For – Embryos used in the research are usually unwanted from
fertility clinics which would be destroyed anyway (campaigners
for the rights of embryos usually want this banned too, they
want scientists to concentrate on developing other sources of
stem cells).
• In some countries stem cell research is banned. It is allowed in
the UK as it follows strict guidelines.

13. Stem cells can produce identical plants
• Meristem used to produce clones (identical copies) of
whole plant quickly and cheaply.
• They can be used to grow rare species.

14. Video clips on stem cells
• https://www.youtube.com/watch?v=8JTw2RpDo9o
• https://www.youtube.com/watch?v=K7D6iA7bZG0
• https://www.youtube.com/watch?v=_Va5Sbbuvpo

15. Specialised cells

18. Chromosomes and Mitosis
Objectives
• Recap work done on stem cells.
• Go through test on quantitative chemistry.
• Repeat test on quantitative chemistry.
• New work: Nucleus, chromosomes, DNA & genes.
• The cell cycle: (i) grow and increase in the number of
subcellular structures such as ribosomes and
mitochondria (ii) DNA replicates (iii) mitosis.

19. Chromosomes and Mitosis
• The nucleus of a cell contains chromosomes made up
of DNA molecules.
• Chromosomes are coiled up lengths of DNA molecules.
• Each chromosome carries a large number of genes.
• Different genes control the development of
different characteristics, e.g. hair colour.
• In body cells, the chromosomes are normally found in
pairs (one from mother and one from father)

20. The cell cycle
• The cell cycle makes new cells for growth,
development and repair.
• The stage of the cell cycle when the cell divides is
called the mitosis.
• The 2 new cells are identical to the original cell, with
the same number of chromosomes.

21. OCR

22. OCR

26. Diffusion, osmosis and active transport
• What is diffusion? Osmosis and active transport?
• Required practical on osmosis.

28. Key points: Diffusion
• Happens in solutions and gases
• The bigger the concentration gradient, the faster the rate of diffusion.
• The higher the temperature the faster the rate of diffusion

32. Key questions:
• Independent variable?
• Dependent variable?
• Controlled variables?
• How may errors arise in this investigation?
• How can you reduce the chance of these errors?

35. Key points: Active transport
• Concentration of mineral ions is higher in the root hair cells than the
soil around them.
• So root hair cells can’t use diffusion to take up mineral ions from the
soil.

42. Summary of cell biology
• Gas exchange in fish.
Summary:
• Prokaryotes and Eukaryotes
• Sub-cellular structures and their
functions
• Light and electron microscope
• Specialised cells.
• Cell differentiation.
• Cell cycle
• Stem cells
• Diffusion
• Osmosis
• Active transport

43. • Gas exchange in fish
• Exam questions
• A3 review on the topic
• Workbook questions

44. How are fish adapted for efficient gas exchange?
• Large surface area
• Efficient blood supply
(animals only)
• A membrane which
is thin, to provide a
short diffusion path
• Concentration
gradient
• Each gill made of lots of thins plates called gill
filaments which are covered in lots of tiny
structures called lamellae (which increase the S.A
even more)
• The lamellae have lots of blood capillaries to speed
up diffusion.
• Thin surface layer of cells to minimise the distance
that gases have to diffuse.
• Blood flows through the lamellae in one direction
and water over in the opposite direction
(maintaining a large concentration gradient), so as
much O2 as possible diffuses from the water into
the blood.