GRADE 9 REVISION NOTES: AQA Biology GCSE Topic 1 Cell Biology

Topic 1: Cell biology  Many mitochondria  active transport of minerals
Eukaryotes & Prokaryotes:  Vacuole with cell sap  maintains a concentration
 Eukaryotes gradient for faster diffusion
o Plant Cells + Animal Cells + Fungi o Xylem
o Divide by mitosis  Long tubes  transport water from roots to leaves
o Animal:  Very thick cell wall  stabilise walls
 Nucleus - Contains the genetic information for the cell +  No internal structures (no chloroplasts, nucleus, etc.)
Controls the activities of the cell.  easier + more space for water to flow
 Cytoplasm - Liquid gel containing organelle where most o Phloem
chemical reactions happen  Vessel cell contains sieve plates  allows sugar to
 Cell Membrane - Controls what substances go in and enter plant cells
out of the cell  No nucleus  easier for sugars to flow
 Mitochondria - Releases energy from respiration  Companion cells with many mitochondria  provides
 Ribosomes - Protein synthesis energy to phloem vessel cell to transport substances
 Cell Wall - Keeps the structure of the cell
o Plant: Cell Differentiation:
 Cell membrane  As an organism develops, cells differentiate to form different
 Nucleus types of cells.
 Cytoplasm  Most types of animal cell differentiate at an early stage.
 Mitochondria  Many types of plant cells retain the ability to differentiate
 Ribosomes throughout life.
 Cell Wall - Keeps the structure of the cell rigid  In mature animals  cell division is mainly restricted to
containing cellulose. repair and replacement.
 Chloroplast - Needed for photosynthesis. Contains  As a cell differentiates it acquires different sub-cellular
chlorophyll structures to enable it to carry out a certain function –
 Permanent Vacuole - Filled with cell sap to keep cell specialised cell
rigid
 Prokaryotes Microscopy:
o Bacteria  Electron Microscope:
o Divide by binary fission 1. Electron Beam
 Cell membrane 2. Higher magnification
 Plasmids – rings of DNA 3. Higher resolution
 Loose Genetic material  Light Microscope:
 (Flagella) – to allow it to swim 1. Light Beam
 (Slime Capsule) 2. Lower magnification
 Cytoplasm 3. Lower resolution
 Ribosomes 4. can be used to
 Comparisons  Can be used to study cells in much finer detail  has enabled
o Prokaryotic cells are much smaller in comparison biologists to see and understand many more sub-cellular
o Prokaryotic cells do not have their genetic material structures
enclosed in a nucleus – single DNA (+plasmids)  1mm = 1000micrometers
o Plant and algal cells have a cell wall (made of cellulose)  1 micrometre = 1000nanonmeters
which strengthens the cell  Magnification
1. By how much an object is enlarged underneath a
Required Practical Activity 1: How to use a microscope microscope
2. Controlled by power of lenses used
Cell Specialisation:  Resolution
 Animal: 1. The minimum distance between two objects at which a
o Sperm microscope can distinguish them as separate entities
 Pointy head  penetrate ovum 2. Controlled by the wavelength of illumination used
 Flagellum  swim to ovum ¿ Image
 Many mitochondria  energy to swim fast Magnication=
Actual ¿ ¿ ¿
 Small  easy to penetrate larger ovum
o Muscle Culturing microorganisms:
 Many mitochondria  release energy for muscle  Bacteria multiply by binary fission (Simple cell division)
contractions  Once every 20 minutes if they have enough nutrients +
 Layers of protein filament  side over each other to suitable temperature + moisture + correct pH
cause contraction  Factors affecting the speed of bacterial growth:
o Nerve 1. Temperature - most bacteria grow fastest in warm
 Long axon  reach different parts of the body + environments
nervous system 2. Nutrient availability - bacteria need a good supply of
 Dendrites (braches)  communicate with other nerve nutrients in order to grow rapidly
cells 3. Moisture - most bacteria grow fastest in moist conditions
 Myelin sheath insulate nerve impulses 4. Oxygen - different types of bacteria either need the
 Plant: presence or absence of oxygen for growth
o Root Hair  Can be grown in a nutrient broth solution/as colonies on an
 Large surface area  absorb more minerals + Water agar gel plate
 Thin cell wall  short diffusion path for minerals to  Uncontaminated cultures of microorganisms required for
enter cell investigating action of disinfectants + antibiotics