What is cell fractionation?

Cell fractionation is the process of breaking open cells and separating the organelles.

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Name the 4 main steps in the process of cell fractionation.

  1. Sample preparation
  2. Homogenisation
  3. Filtration
  4. Ultracentrifugation 

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Why does the tissue sample need to be homogenised?

The tissue sample needs to be homogenised to break open the cells and release the organelles.

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Why does the homogenised solution need to be filtered?

The homogenised solution needs to be filtered to remove any large cell debris.

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What is the purpose of ultracentrifugation?

The purpose of ultracentrifugation is to separate the organelles by density or mass.

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Why is the tissue sample added to an ice-cold solution?

The tissue sample is added to an ice-cold solution to reduce the activity of enzymes that digest organelles.

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Why is the tissue sample added to an isotonic solution?

The tissue sample is added to an isotonic solution to prevent damage to organelles by osmosis.

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Why is the tissue sample added to a buffered solution?

The tissue sample is added to a buffered solution to maintain the pH so that proteins or enzymes are not denatured.

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In ultracentrifugation, what is a pellet?

A pellet is a thick sediment at the bottom of a tube containing the heaviest organelles.

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In ultracentrifugation, what is a supernatant?

A supernatant is a fluid above the pellet that contains lighter organelles.

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What is the order of organelles from heaviest to lightest?

Nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum, ribosomes.

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