Light microscopes are pretty poor overall, there only advantage is that they're cheap and can see in colour....
- Resolution = up to x1500
- Can see in colour
- Lower resolution than electron microscopes (resolution is the closest distance from which we can define two distinc structures)
In a light microscope, cells are stained with dyes in order to make them easier to see.
Transmission Electron Microscopes (TEM)
- Magnification = x500,000
- The image is 2D
- How it works - Electrons pass through denser areas of the sample less easily and this produces contrast.
Scanning Electron Microscope (SEM)
- Magnification = x100,000
- Image produced is 3D
- How it works - Electrons are bounced off the sample.
Both these methods are colourless but False-colour can be added.
Staining - Objects are stained with metal particles so that the electrons are more likely to be deflected from the object producing a clearer image.
Magnification and Resolution
Magnification - This is how big you can make the image compared to its original size. The Magnification of an image can be calculated by taking an images size and dividing it by its original size.
Resolution - This is the minimum distance which you need to define 2 seperate objects. For example.......
The resolution is 0.1nm for an electron microscope.
whereas a light microscope has a resolution of 200nm.
Actual Size = Image size/Magnification
Magnification = Image Size/Actual size
Plant cell structure
Animal Cell structure
Assorted Endoplasmic Reticulums (ER)
The structure of the ER is a series of membrane bound sacs these are called cisternae the rough ER is studded with Ribosomes whereas the Smooth ER is not.
Rough ER - The function of this is too transport proteins produced at the Ribosomes present on the rough ER's surface, some of these are secreted from the cell.
Smooth ER - The function of this is to produce Lipids that the cell needs.
Structure- The structure of the Golgi apparatus is a stack of membrane bound sacs, unlike the golgi apparatus where they are in a series.
Function- The function of the golgi apparatus is too receive proteins from the ER and modify them. These proteins are packaged into vesicles and these vesicles are then transported, they may be transported to the surfac of the cell where they are secreted.
Structure - The structure of the mitochondrion is that they may be spherical or sauasge shaped, inside it is 2 membranes seperated by a fluid filled space, these are folded very tightly to form cisternae (and increase surface area) the inner part of a mitochondrion is called the matrix.
Function - The function of a mitochondrion is the site of ATP production during respiration, this is the almost universal way of transporting potential energy, this is because many processes use the energy gained from reactions involving ATP.
Structure - These are found in plant cells, cholorplasts consist of two membranes seperated by a fluid filled space, in which there is an elaborate series of membrane sacs called thylakoids.
Function - This is the site of photosynthesis in plant cells, light drives this reaction in this reaction carbohydrate molecule i.e glucose from carbon dioxide and water.
Structure - These are spherical sacs surrounded by a single membrane.
Function - These contain powerful digestive enzymes, these break down materials.
Structure- These are tiny organelles with no membranes surrounding them.
Function - These are the site of protein synthesis in the cell some are present on the rough ER. They act as an assembly line using information from the nucleus to assemble proteins from amino acids.
Structures- These are small tubes of protein fibres.
Function- These play a key role in cell division, they form spindles which seperate genetic material during division.
Structure - A long whip like appendage which protrudes from the cell.
Function - The function of the flagellum is mainly locomotive, allowing the cell tom move. Though it is also sensory, being sensitive to chemicals and temperature outside the cell.
Structure - A small eyelash like structure which protrudes from the cell.
Function - They serve one of two functions
- They can be used to move objects like mucus within the trachea.
- They can be used as a sensory aid. (This its most likely role within a cell)
Structure - The structure of the nucleus consists of the nucleuolus within the nucleus which is surrounded by a nuclear envelope, this nuclear envelope contains pores which molecules can pass through.
Function - This structure houses all the genetic material of the cell, it is surrounded by chromatin which contains genetic material to be used in constructing new proteins.
Protein production and secretion
There is a specific system used to produce and secrete proteins and it goes a little something like this...
- Firstly the information is collected from DNA within a gene in the Nucleus.
- This is the copied onto a molecule called mRNA.
- This leaves the nucleus through a nuclear pore, and attaches to a ribosome on the rough ER.
- The protein is assembled at the rough ER where it is placed into a vesicle, and transported to the golgi apparatus.
- The golgi apparatus modifies the protein and then it is sent to the cell surface membrane where it is secreted.
The cytoskeleton basically provides the cell with a framework so it can maintain its shape.
It consists of a set of protein molecules they also contain microtubules, these move around stuff inside the cell for example vesicles these microtubules are called microtubule motors.
Prokaryotes - These are cells which lack a nucleus.