Cells

Eukaryotic Cells

• Found in Plants, animals, fungi and protists.
• They are 10 - 100 micrometres in size.
• A eukaryote is an organism made up of eukaryotic cells.

Prokaryotic Cells

• Prokaryotic cells are 0.1 - 5.0 micrometres in size.
• A prokaryote is an organism made up of prokaryotic cells.
• Bacteria are prokaryotes.

The key features of prokaryotic cells are:

• No mitochondria or chloroplasts
• No nucleus - instead most of the genetic material is stored in a single DNA loop in the cytoplasm
• Plasmids - some cells contain small rings of dna called plasmids. These can replicate and move between cells so that genetic information can be shared

What is Binary Fission?

• Prokaryotic cells such as bacteria reproduce by a process called binary fission
• In binary fission a cell makes a copy of its genetic material (dna and plasmids) before splitting into two daughter cells
• In the right conditions bacteria can divide every 20 minutes

How does binary fission work?

1. Genetics in parent cell duplicates

2. The cytoplasm splitis into two

3. Two daughter cells are formed

Mean Division Time

If we want to estimate the number of bacteria in a population we need the mean division time.

Mean division time= average time taken for one bacterial cell to divide into two.

A bacterial cell has a mean division time of 30mins. How many cells will be produced after 2.5hrs?

1. Convert 2.5hrs into mins (2.5 x 60 = 150mins)

2. Divide the total time they have been producing cells by the mean division time- this gives you the number of divisions (150mins / 30mins = 5 divisions)

3. Multiply 2 by itself for the number of divisions. This gives you the number of cells (2x2x2x2x2 or 2^5 = 32 cells)