All of specification for paper 1 Biology AQA trilogy. Is an edited version I made with most crucial information highlighted and the methods for each practical are in the annotations. Notes are responding to the specification requirements
Plant and animal cells (eukaryotic cells) have a cell membrane, cytoplasm and genetic
material enclosed in a nucleus.
Bacterial cells (prokaryotic cells) are much smaller in comparison. They have cytoplasm and
a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a
nucleus. It is a single DNA loop and there may be one or more small rings of DNA called
plasmids.
Students should be able to demonstrate an understanding of the scale and size of cells and
be able to make order of magnitude calculations, including the use of standard form.
4.1.1.2 Animal and plant cells
Students should be able to explain how the main subcellular structures, including the
nucleus, cell membranes, mitochondria, chloroplasts in plant cells and plasmids in bacterial
cells are related to their functions.
Most animal cells have the following parts:
● a nucleus
● cytoplasm
● a cell membrane
● mitochondria
● ribosomes.
Plant cells often have:
- chloroplasts
- a permanent vacuole filled with cell sap.
Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.
Students should be able to use estimations and explain when they should be used to judge
the relative size or area of subcellular structures.
Required practical activity 1: use a light microscope to observe, draw and label a
selection of plant and animal cells. A magnification scale must be included.
MAGNIFICATION METHOD:
1. Peel off an epidermal layer on the onion using forceps.
2. Place on a slide with forceps
3. Add 2 drops of iodine solution to stain the cells.
4. Place the cover slip on at an angle to stop air bubbles forming
5. Remove any excess stain by soaking it with paper towels.
6. Place the slide on the stage of the microscope.
7. Turn the nosepiece to select a low power objective.
8. Use the coarse adjustment knob to raise the stage until the cover slip just touches
the objective.
9. Now look into the eyepiece and turn the coarse focus knob to move the stage away
until the image comes into focus
10. Turn the nosepiece to select a high power objective. (e.g x40)
, 11. Turn the fine focus knob until the image comes into focus.
12. Make a labelled drawing of a few of the cells you can see
4.1.1.3 Cell specialisation
Students should be able to, when provided with appropriate information, explain how the
structure of different types of cell relate to their function in a tissue, an organ or organ
system, or the whole organism.
Cells may be specialised to carry out a particular function:
4.1.1.4 Cell differentiation
Students should be able to explain the importance of cell differentiation.
As an organism develops, cells differentiate to form different types of cells.
● Most types of animal cells differentiate at an early stage.
● Many types of plant cells retain the ability to differentiate
throughout life.
● In mature animals, cell division is mainly restricted to repair and replacement.
● As a cell differentiates it acquires different subcellular structures to enable it to carry
out a certain function. It has become a specialised cell.
4.1.1.5 Microscopy
Students should be able to:
● understand how microscopy techniques have developed over time
● explain how electron microscopy has increased understanding of subcellular
structures.
Limited to the differences in magnification and resolution.
An electron microscope has much higher magnification and resolving power than a light
microscope. This means that it can be used to study cells in much finer detail. This has
enabled biologists to see and understand many more sub-cellular structures.
Students should be able to carry out calculations involving magnification, real size and
image size using the formula:
magnification = size of image size of real object
Students should be able to express answers in standard form if appropriate.
4.1.2 Cell division 4.1.2.1 Chromosomes
The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome
carries a large number of genes.
In body cells the chromosomes are normally found in pairs.
, 4.1.2.2 Mitosis and the cell cycle
Cells divide in a series of stages called the cell cycle. Students should be able to describe
the stages of the cell cycle, including mitosis.
During the cell cycle the genetic material is doubled and then divided into two identical cells.
Before a cell can divide it needs to grow and increase the number of subcellular structures
such as ribosomes and mitochondria. The DNA replicates to form two copies of each
chromosome.
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Finally the cytoplasm and cell membranes divide to form two identical cells.
Students need to understand the three overall stages of the cell cycle but do not need to
know the different phases of the mitosis stage.
Cell division by mitosis is important in the growth and development of multicellular
organisms.
Students should be able to recognise and describe situations in given contexts where
mitosis is occurring.
Visit aqa.org.uk/8464 for the most up-to-date specification, resources, support and administration 23
4.1.2.3 Stem cells
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to
many more cells of the same type, and from which certain other cells can arise from
differentiation.
Students should be able to describe the function of stem cells in embryos, in adult animals
and in the meristems in plants.
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.
Knowledge and understanding of stem cell techniques are not required.
Treatment with stem cells may be able to help conditions such as diabetes and paralysis.
In therapeutic cloning an embryo is produced with the same genes as the patient. Stem
cells from the embryo are not rejected by the patient’s body so they may be used for
medical treatment.
The use of stem cells has potential risks such as transfer of viral infection, and some people
have ethical or religious objections.
Stem cells from meristems in plants can be used to produce clones of plants quickly and
economically.
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