Cells and Miroscopes

All living things are made up of cells. The structures of different types of cells are related to their functions. All living things are made of cells. Most human cells, like most other animal cells, have the following parts: a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant and algal cells also have: cell wall, chloroplasts and a permanent vacuole. Here is what each feature does:

•  Nucleus – controls the activities of the cell. 
• Cytoplasm – where most of the chemical reactions take place.
• Cell membrane - controls the passage of substances in and out of the cell.
• Mitochondria - where most energy is released in respiration. 
• Ribosomes -  where protein synthesis occurs.
• Cell wall – made of cellulose and strengthens plant cells.
• Chloroplasts - absorb light energy to make food in plant cells.
• Permanent vacuole - filled with cell sap in plant cells.

Specialised cells are cells that are adapted to a particular function. Here are two examples:

• Sperm Cell - They have a long tail so they can move quickly. The middle section is full of mitchondria, which transfer energy needed for the tail to work. They also have a large nucleus which contains the genetic material that needs to be passed on. 

• Nerve Cell - Nerve cells have lots of different dendrites to connect with other nerves. They contains axons which carry the nerve impulse from one place to another. They aslo have myelin sheath for insulation. 

To get into or out of cells, dissolved substances have to cross the cell membranes.

• Solutes = particles in solution eg glucose, sodium ions, chloride ions.
• Solvent = liquid in which the particles are dissolved eg water.

Solute and solvent molecules move around randomly. Solutes can move into and out of cells by diffusion.  

Diffusion

Diffusion is the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region where they are of a higher concentration.

Oxygen required for respiration passes through cell membranes by diffusion. The greater the difference in concentration, the faster the rate of diffusion.

Eukaryotic cells are plant and animal cells. They all have cell membranes, cytoplasm and genetic material in the nucleus. The genetic material is called DNA and is contained in the nucleus of chromosomes.  

 Prokaryotic cells are bacteria, they are single celled living organism. They are twice as small as eukaryotic cells. Bacteria have cytoplasm and a cell membrane surrounded by a cell wall. However, the genetic material isn’t contained in the nucleus. The bacteria chromosome is a single DNA loop found in the cytoplasm. 

Here is a diagram of a bacteria cell:

The light microscope magnifies up to 2000 times whereas the electron microscope magnifies up to 2 million times. The Electron Microscope is more useful because it uses electron beams instead of normal light beams meaning the image is better and in more detail. 

You can calculate magnification by multiplying the magnification of the eye piece by the magnification of the object lense.

 If you want to calculate the size of objects under the microscope then there’s a simple formula, based on the magnification triangle, if you know/measure two of the factors you can always find the third.

 Example – If you’re working at a magnification of x40 and the image of the cell you’re looking at measures 1mm you can work out the actual size of the cell. 

1cm = 10mm

1mm = 1000micrometers (um)

1um = 1000 nanometers (nm)

So a nanometer is 0.000000001m, or in standard form 1 x 10

In standard form a number is always written as:

A = 10

A is always 1 - 10, n tells us how many places to move the decimal place.