The following document contains summarised all of the required infomation for the AQA Higher Seperate Biology Exam that helped myself and several others achieve a grade 9, and so can you!
Biology
Paper 1
Cell Biology:
● Animal cells:
○ Nucleus - controls the activities of the cell and contains the genetic material
○ Cytoplasm - in which most chemical reactions take place
○ Cell membrane - controls the passage of substances into and out of the cell
○ Mitochondria - where aerobic respiration takes place
○ Ribosomes - where proteins are synthesised
● Plant cells:
○ All sub cellular structures found in plant cells
○ Cell wall - made of cellulose, which strengthens the cell
○ Permanent vacuole - filled with cell sap, to support the plant
○ Chloroplasts - to absorb light to make food by photosynthesis
● Animal, plant and fungal cells are eukaryotic
● Bacterial cells are prokaryotic
● Prokaryotic cells:
○ Much smaller in size
○ The genetic material is not enclosed in a nucleus
○ The genetic material is a single loop of DNA, and there may be one or more small rings of DNA called
plasmids
○ They do not contain chloroplasts or mitochondria
● Bacterial cell:
○ The roles of mitochondria and chloroplasts are taken over by the cytoplasm
○ Plasmids are present
○ Plasmids allow bacterial cells to move genes from one cell to another#
○
○ Plasmids allow genes to be inserted into bacteria in genetic engineering
●
Unit Number of units in 1 metre
Centimetre (cm) 100
Millimetre (mm) 1000
Micrometre 1000000
Nanometre (nm) 1000000000
●
● A typical plant cell = 0.1mm diameter
● Typical animal cell = 0.02mm diameter
● Prokaryotic cell = 0.002mm long
● Microscopes:
○ The ability to see two or more objects as separate objects is called resolution
○ The light microscope was developed in the late 16th century
○ In 1933, the first electron microscopes were used
○ An electron microscope passes electrons, rather than light, through the specimen and can give much better
resolution
○ Practical:
■ Place a tissue sample on a microscope slide
■ Add a few drips of a suitable stain
■ Lower a coverslip onto the tissue
, ■ Place the slide on the microscope stage and focus on the cells using low power
■ Change to high power and refocus
■ Draw any types of cells that can be seen
■ Add a scale line to the diagram
■
○ Magnification - how many times larger the image is than the real object
○ Magnification = size of image / size of real object
● Growing microorganisms:
○ Bacteria divide by binary fission, a form of aesexual reproduction
○ If they have enough nutrients and a suitable temperature, they can multiply every 20 minutes
○ The Petri dishes and agar must be sterilised before use, so that unwanted organisms are killed
○ An inoculating loop is sterilised by passing it through a flame
○ He cooled inoculating loop is used to transfer bacteria to the agr
○ The lid of the Petri dish must be quickly removed and replaced when transferring bacteria and secured with
tape to stop it coming off
○ The dish is stored upside down to stop condensation dripping onto the agar surface
○ The process uses aseptic techniques
○ Incubation temperature should be 25 degrees celsius
● Chromosomes:
○ The nucleus of a cell contains chromosomes made of DNA
○ Each chromosome carries many genes
○ Different genes contain the code to make different proteins and so control the development of different
characteristics
○ In body cells, chromosomes are found in paris
● Mitosis and the cell cycle:
, ○
○ Cell cycle:
■ DNA is copied and new chromosomes are made
■ Mitosis
■ Each cell grows and makes new sub-cellular structures
○ Cell division by mitosis is important because it makes new cells for:
■ Growth and development of multicellular organisms
■ Repairing damaged tissues
■ Aesexual reproduction
● Stem cells:
○ Stem cells are undifferentiated, so they can divide to make different types of cell
○ Stem cells are found in human embryos, in the umbilical cord of a newborn baby and in some
organs/tissues
○ Stem cells from embryos are called embryonic stem cells
○ Adult stem cells are found in some organs and tissues, like bone marrow. But they can only specialise into
some cells
● Uses of stem cells:
○ Stem cells can be used in the treatment of diabetes and paralysis, where cells are damaged or not working
properly
○ A cloned embryo of the patient may be made and used as a source of stem cells, this is called therapeutic
cloning
○ Stem, cells from the cloned embryo will not be rejected by the patient’s body
○ Some people are against using stem cells from cloned embryos:
■ There may be risks, such as the transfer of viral infection
■ They may be ethical or religious objections
○ In plants, stem cells are found in the meristem
○ The meristem allows plants to make new cells for growth
○ The stem cells can be used to produce clones of plants quickly
○ This could be useful:
■ Are pieces can be cloned to protect them from extinction
■ Large numbers of identical crop plants with special features, such as disease resistance, can be
made
● Diffusion:
○ Diffusion is the net movement of particles from an area of higher concentration to an area of lower
concentration
○ Examples;
Oxygen and carbon dioxide diffuse during gas exchange in lungs, gills and plant leaves
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller jackbarrell11. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.60. You're not tied to anything after your purchase.
