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Questions and Answers
What is the characteristic of lipids in terms of solubility?
What is the characteristic of lipids in terms of solubility?
- Soluble in water but not in organic solvents
- Soluble in both water and organic solvents
- Insoluble in both water and organic solvents
- Soluble in organic solvents but not in water (correct)
What is the primary function of lipids in adipose tissues?
What is the primary function of lipids in adipose tissues?
- Energy reserve (correct)
- Structural component of cells
- Protein synthesis
- Hormone regulation
What is the purpose of using calcium in Baker's formal calcium fixation?
What is the purpose of using calcium in Baker's formal calcium fixation?
- To preserve the structure of carbohydrates
- To remove proteins from the tissue
- To make lipids more soluble
- To make lipids less soluble (correct)
What is the principle of Oil Red O staining?
What is the principle of Oil Red O staining?
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What is the common problem in lipid staining due to insufficient fixing or drying of tissue sections?
What is the common problem in lipid staining due to insufficient fixing or drying of tissue sections?
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What is the result of Sudan Black staining on lipid substances?
What is the result of Sudan Black staining on lipid substances?
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Study Notes
Characteristics of Lipids
- Lipids are soluble in organic solvents but not in water.
- They are found in adipose tissues as an energy reserve.
- Lipids are rarely present in a pure state (triglycerides).
- They are usually found in combination with carbohydrates or proteins, forming glycolipids or lipoproteins/proteolipids.
Staining Methods for Lipids
- Oil Red O:
- Principle: Based on the greater solubility of the dye in lipid substances than in hydroalcoholic solvents.
- Results: Lipids (triglycerides, cholesterol esters) stain red, nuclei stain blue (with alum hematoxylin).
- Sudan Black:
- Principle: Sudan Black B is a dye that is insoluble in water but dissolves in fat.
- Results: Lipids (triglycerides, cholesterol esters) stain blue/black, nuclei stain red (with nuclear fast red).
Fixation for Lipid Demonstration
- Unfixed cryostat sections or Baker's formal calcium can be used.
- Baker's formal calcium: 10% formalin with 1.1g CaCl per 100ml, which reacts with lipids to form soaps, making them less soluble.
Common Problems in Lipid Staining
- Patchy or no staining: Incomplete removal of paraffin wax.
- Section float off during staining: Insufficient fixing/drying of tissue section on the glass slide.
- Sections appear cloudy: Insufficient dehydration or clearing.
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