Topic 2 - Cell Fractionation

Question 1

What is the purpose of cell fractionation?

Answer 1

To isolate organelles in cells.

Question 2

What is the process of homogenisation?

Answer 2

– Cells are broken apart using a homogeniser
– This forms a liquid called the homogenate, which contains a mixture of cell organelles
– The homogenate is then filtered to remove debris and unbroken cells

Question 3

What is ultracentrifugation?

Answer 3

– The homogenate is placed in a centrifuge and spun a different speeds to separate the organelles based on their density

Question 4

What will occur when spinning a difference speeds in ultracentrifugation?

Answer 4

At a low speed, the heaviest organelle (the nucleus) settles at the bottom of the tube as a pellet the remaining is the supernatant and is removed.
The supernatant is transferred to YouTube and span at highest speed the next heaviest organelle forms a pallet at the bottom.

Question 5

Why must cells be suspended in a cold isotonic, buffered solution?

Answer 5

1. Cold: reduce enzyme activity and prevent organelle damage.
2. Isotonic: maintain the same water potential as the cells to prevent osmotic lysis or shrinkage of organelles.
3. Buffered: prevent fluctuations in pH, which could nature proteins and damage organelles.

Question 6

What is the order of organelle separation including plants?

Answer 6

1. Nuclei
2. Chloroplasts
3. Mitochondria.
4. Lysosomes and endoplasmic reticulum.
5. Ribosomes.