Summary GCSE AQA Biology (9-1) Full Course Revision
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Course
Biology
Institution
GCSE
Detailed notes for GCSE AQA Biology with clear explanations of each topic with all B1-B18 notes. Key Diagrams and specification references included in purple.
Nucleus: Controls all activ7ities of the cell and contains the genetic material of the cell
Cytoplasm: Gel-like substance where most of the chemical reactions happen. It contains
enzymes that control these chemical reactions
Cell membrane: Holds the cell together and controls what goes in and out of the cell.
Mitochondria: These are where most of the reactions for aerobic respiration take place.
Respiration transfers energy that the cell needs to work.
Ribosome: These are where the proteins needed for the cell are synthesised.
Cellulose cell wall: It supports the cell and strengthens it
Chloroplast: This is the site of photosynthesis, which makes glucose for the plant. They
contain a green substance called chlorophyll, which absorbs the light needed for
photosynthesis
Permanent Vacuole: Contains cell sap and helps to keep the cell rigid to support the plant.
Plasmid: To carry antibiotic-resistant genes and spread them in the whole human/animal
body
➔ Microscopy
Resolution: A measure of the degree of detail that can be seen. The ability to distinguish
between two points.
Magnification: The size at which an image can be seen. The number of times greater an
image appears compared to the real object.
An electron microscope has a much higher magnification and resolving power than a light
microscope. This means that it can be used to study cells in much finer detail.
Magnification= Image Size/ Object size
, ➔ RP1: Microscopy
1. Collect a specimen from a sample
2. Add a drop of water to the slide
3. Place the specimen onto the glass
slide
4. Add 2-3 drops of stain → Increases
clarity
5. Mount cover slip onto the specimen
6. Gently push the coverslip to remove
air bubbles
7. Use tissue paper to remove excess
stain
8. Place the slide onto the microscope
stage
➔ Cell Differentiation and Specialisation
Cellular Differentiation is the process by which cells become specialised and adapted to carry
out a particular function
Nerve Cells:
Function: Carry electrical signals from one part of the body to another.
Adaptations: → Lots of dendrites- To make connections to other nerve cells
→ Axon- Very long and carries nerve impulses to other parts
→ Synapse- Pass impulses of another cell between a nerve cell and a muscle cell
in the body using special transmitter chemicals.
→ Myelin sheath for insulation
Muscle Cells:
Function: Contract and relax in pairs so those vertebrates can move on land and water and in
some cases, fly
Adaptations: → Contains actin and myosin- slide over each other making fibres contract
→ Lots of mitochondria- To transfer the energy needed for the chemical reactions
that take place as the cells contract and relax
→ Can store glycogen- Can be broken down and used in cellular respiration by
the mitochondria to transfer the energy needed for contraction
,Sperm Cells:
Function: Contains the genetic information from the male parent
Adaptations: → Long flagellum- Whips from side to side to help the sperm move through the
female reproductive system
→ Middle section full of mitochondria- Transfers energy for the cell to work
→ Digestive enzymes in acrosome- Breaks down the outer layer of the egg
Root Hair Cells:
Function: Helps plants take in lots of water and mineral ions more efficiently
Adaptations: → High surface area- Allows more water to move into the cell
→ Large permanent vacuole- Speeds up the movement of water by osmosis
→ Lots of mitochondria- Transfers the energy needed for active transport of mineral ions
Photosynthetic Cells:
Function: Production of sugars through the process of photosynthesis
Adaptations: → Chloroplasts: Contains chlorophyll to trap light for photosynthesis
→ Positioned in layers- To maximise the absorption of light for photosynthesis
→ Large permanent vacuole- Keeps cell rigid as a result of osmosis
Xylem Cells:
Function: Carry water and mineral ions to the highest leaves and shoots
Adaptations: → Lignin- Causes cells to die and form long hollow tubes
→ Strong spirals of lignin- Helps the cell withstand the pressure of water moving up the plant
Phloem Cells:
Function: Carries the sugars made by photosynthesis around the body of the plant
Adaptations: → Cell wall breaks down to form sieve plates- Allows water to move freely up
and down the plant
➔ Plant Organisation
A tissue is a group of cells with a similar structure and function.
Organs are aggregations of tissues performing specific functions.
Organs are organised into organ systems, which work together to form organisms.
➔ Biological Examples of Diffusion
Diffusion is the spreading out of the particles of any substance in solution, or particles of a
gas, resulting in a net movement from an area of higher concentration to an area of lower
concentration.
, → Diffusion and Breathing
Oxygen is inhaled and diffuses through the lungs and into the bloodstream. The oxygen is
then transported around the body
Carbon Dioxide in the waste gas is produced by respiration and diffuses from the body
tissues and into the bloodstream
Alveoli adaptations: Very thin, covered by a network of fine capillaries enabling a short
diffusion distance, and are moist to encourage gas molecules to dissolve easily; Hollow cup
shape and many of them increase SA: V Ratio, and capillaries maintain steep concentration
gradients
→ Diffusion and Digestion
The villi increase the overall surface area of the small intestine, thus increasing the volume of
substances that can be absorbed by diffusion. The villi have a good blood supply so when
substances diffuse, they can go straight to the bloodstream enabling a concentration gradient,
also have microvilli on them to increase SA: V, and finally are 1 cell thick like capillary and
alveoli walls to reduce the distance for diffusion
→ Diffusion & Photosynthesis in a plant leaf
Carbon dioxide and oxygen are involved in the gas exchange of the leaf. When carbon
dioxide enters the stomata, the oxygen exits guard cells on the lower epidermis do this,
closing and opening the stomata based on whether they are turgid or flaccid - if they are
turgid in bright light they close the stomata to prevent water loss from evapotranspiration,
and if they are in low light they become flaccid and open the stomata.
➔ Osmosis
Osmosis is the diffusion of water from a dilute solution to a concentrated solution across a
partially permeable membrane.
Hypotonic Solution- The concentration of solutes in the solution outside the cell is lower than
the internal concentration of solutes
→ The plant cell will become turgid. This means that the cell has become swollen or
congested as the water moves into the cell by osmosis
→ The animal cell will become lysed/burst
Easier to remember by using water potential - (basically the concentration of water)
hypotonic means higher water potential in the solution than the cell so water moves in,
making it turgid (can remember this by hypo - like a hippo, so fat lmao)
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