1.1 cells

• a light microscope can magnify objects several hundred times
• electron microscopes can magnify objects several hundred thousand times
• the parts of a microscope are the stage, eyepiece, objective lens, stage clips, iris diaphragm and course/fine focus control
• the field of view is the size of what you look at when you put your eye above the eyepiece lens
• 1mm = 1000 micrometres
• to measure the diameter of the field of view, focus the mm scale of a clear ruler and repeat for each magnification
• actual size = observed size/magnification
• there are four main important parts of a light microscope. the source of light, the specimen, the lenses that make the specimen seem bigger and the magnified image of the specimen that you see.
• for a electron microscope, the light source is replaced by a beam of very fast moving electrons
• for an electron microscope, the specimen has to be specially prepared and held inside a vacuum chamber from where the air has to be pumped out (electrons do not travel very far in air)
• the lenses in an electron microscope are replaced by a series of coil-shaped electromagnets, these coils bend the electron beams
• the image formed using an electron microscope is called an electron micrograph
• resolution is the ability to distinguish between 2 points that are close together
• a beam of electrons has a shorter wavelength than a beam of light, thereby providing higher resolution imagery
• a light microscope provides a relatively low magnification image
• a SEM (scanning electron microscope) has a higher magnification than a light microscope and it provides 3D images of how a cell looks like
• a TEM (transmission electron microscope) has a very high magnification so we can see the inner organelles present within a cell
• a cytoplasm is a thick juice which fills a cell and is where all chemical reactions take place
• a nucleus is the control centre of a cell and contains chromosomes made of DNA (which contains instructions to operate and build the cell)
• a mitochondrion is the site of aerobic respiration in a cell
• a ribosome is where protein synthesis takes place in a cell
• a cell membrane is a thin skin which surrounds a cell and it is selectively permeable
• dilute methylene blue is used to dye animal cells for inspection
• chloroplasts are where the process of photosynthesis occurs and they contain a green pigment which absorbs light called chlorophyll
• a cell wall is typically made of cellulose (except for bacteria cells) and they provide protection to a cell from the outside
• a permanent vacuole (filled with a watery liquid called cell sap) helps to support the cell from the inside
• when inspecting plant cells, they need to be dyed by iodine
• for bacteria cells, they have their own unique parts of their structure which are slime capsules (helps to protect), a main loop of DNA (which isn't contained in a nucleus), a plasmid (which are extra loops of DNA), a flagellum (which help the bacterium move) and a cell wall (which IS NOT MADE OF CELLULOSE)
• when a cell becomes specialised, its structure starts to morph so it better is adapted to its role
• a nerve cell has a long axon (which allows impulses to be carried across large distances), a dendrite (which makes connections with other nerve cells) and an insulating sheath (which insulates the axon and speeds up the transmissions of the impulses)
• a sperm cell has a long tail (to help it swim), their middle section is filled with mitochondria (to provide energy for its journey for fertilisation), the acrosome contains enzymes (to break through the egg for fertilisation) and a large nucleus to carry genetic information to the egg cell
• a root hair cell can be found in the roots of plants and has a large surface area for absorbing water and mineral ions . it also has a lot of mitochondria to provide energy to carry out active transport
• a palisade cell is found in a leaf and is packed full of chloroplasts (which absorb sunlight for the process of photosynthesis) and these cells are column-shaped to trap the maximum amount of sunlight
• a tissue is a group of cells with a similar structure and function working together
• muscular tissue (animal) : contract to produce movement
• glandular tissue (animal) : containing secretory cells to produce important substances like mucus or sweat
• epithelial tissue (animal) : acts as a lining to the organs
• epidermal tissue (plant) : covers and protects the surfaces of a plant
• mesophyll tissue (plants) : contains chloroplasts for photosynthesis
• xylem tissue (plants) : transports water and mineral ions around a plant