general exam feedback

Question 1

what is the purpose of the buffer in centrifugation?

Answer 1

to maintain a constant pH and to prevent damage to the enzymes

Question 2

what features are in prokaryotes that aren’t in human cells?

Answer 2

70S ribosomes,capsule,circular DNA etc.

Question 3

why can mitochondria under a microscope vary in appearance?

Answer 3

cut from different angles/plane views

Question 4

why has TEM got a greater resolution than other microscopes?

Answer 4

• it has a greater resolving power

- smaller wavelength of electrons

Question 5

give three differences between mitosis and meiosis

Answer 5

• 1 division in mitosis whereas 2 divisions in meiosis
• 2 cells produced in mitosis whereas 4 cells produced in meiosis
• genetically identical daughter cells in mitosis whereas genetically different daughter cells in meiosis

Question 6

describe how to make a 1 in 10 dilution to then use this to make a 1 in 1000 dilution of the original liquid culture of bacteria

Answer 6

1. add 1 part bacteria culture to 9 parts sterile liquid (10^-1 dilution)
2. mix well
3. repeat using 9 parts fresh sterile liquid and 1 part of 10^-1 and 10^-2 dilutions to make 10^-3 dilutions