I have published a compilation of study notes on every topic of the CIE IGCSE Biology course. Using these study notes, I got an A* in Biology (well actually a 9 out of 9) and I found that without them, this would have been impossible. Each document is worth 5$ which is a very reasonable price, as m...
• Some organisms are UNICELLULAR → they are made up of one cell (e.g. bacteria and yeast)
MICROSCOPES
• Used in schools → light microscope: it shines light through what you want to observe
: uses a glass lens to magnify and focus the image
: can magnify about 1500 times
Photomicrographs → a photo taken under a light microscope
Electron microscope → can magnify up to 500,000 times
: Uses a beam of electrons instead of light
STRUCTURE CHARACTERISTICS FUNCTIONS
1. All cells have it 1. Controls what goes in and out of the cell
1) CELL MEMBRANE
2. A very thin layer of protein and fat 2. Holds the cell together
3. It is PARTIALLY PERMEABLE (will let some substances through)
4. Surrounds the cell
1. Mainly made of cellulose (belongs to a group of substances called 1. Helps protect and support the cell
2) CELL WALL
polysaccharides) 2. If the cell absorbs a lot of water and swells, the cell wall
2. Animal cells DON’T have it stops it from bursting
3. It Is FULLY PERMEABLE (allows even large molecules to go through it) 3. It defines the cell’s shape
1. It is a clear jelly (nearly all water) 1. Supports cell structure
3) CYTOPLASM
2. Contains many substances dissolved in it, like PROTEINS 2. Site of many chemical/metabolic reactions
1. Surrounded by a membrane 1. Used for storage of certain materials
4) VACUOLE
2. IN PLANTS → Contains a solution of sugars called CELL SAP 2. Helps support the shape of the cell
3. IN ANIMALS → These are called VESICLES (may contain food or water) 3. VESICLES → Used to safely transport substances form one
part of the cell to another
1. NEVER found in animal cells 1. Site of photosynthesis, providing food for the plants
5) CHLOROPLASTS
2. Contain green pigment called CHLOROPHYLL 2. The chlorophyll absorbs light energy needed for
3. Often contain starch grains PHOTOSYNTHESIS
6) NUCLEUS 1. Stores the genetic information, which helps the cell make
the right kinds of proteins
---
2. Controls cell division
3. Controls how the cells grow and work
1. NOT found in prokaryotic cells 1. Site of aerobic respiration, providing energy for the cell
7) MITOCHONDRIA
2. The powerhouses of the cell
3. Cells with lots of metabolic reactions going on have high numbers of
mitochondria
1. They are attached to a network of membranes called the ROUGH 1. Site of protein production in protein synthesis
8) RIBOSOMES
ENDOPLASTIC RETICULUM
2. Can also be found scattered freely in the cytoplasm
3. Found in all types of cells
MICROMETRES
Symbol → m
1m = 1 x 10-6m
CALCULATING MAGNIFICATION
Magnification is calculated using the following equation:
Magnification = Drawing size ÷ Actual size
1
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