Lipids: Phospholipid & Sphingolipid Metabolism

Questions and Answers

What is the purpose of adding KHSO4 to the powdered glycerol solution?

To create an emulsion

To neutralize the solution

To increase the solubility of lipids

To dehydrate glycerol (correct)

What does the peculiar odor produced during the heating process primarily indicate?

The formation of acrolein (correct)

Burnt carbohydrates

The presence of alcohol

Decomposition of fatty acids

What should be done with the ether-alcohol extract before conducting the acrolein test?

Mix it with sulfuric acid

Dilute it in water

Evaporate it to a syrupy consistency (correct)

Cool it to room temperature

Which part of the ether-alcohol extract is used for the acrolein test?

The first 2/3 portion Signup and view all the answers

What role do the glass beads play in the Erlenmeyer flask during heating?

To prevent bumping Signup and view all the answers

What happens to glycerol when it is heated in the presence of KHSO4?

It dehydrates to form acrolein Signup and view all the answers

What is the main component in the ether-alcohol extract that is tested for during the experiments?

Total lipids Signup and view all the answers

Why should the evaporation of the extract be done without flame?

It avoids flammable vapor ignition Signup and view all the answers

What property of glycerol allows it to be miscible with water?

The three hydroxyl groups Signup and view all the answers

Which statement about glycerol is incorrect?

Glycerol is is insoluble in water. Signup and view all the answers

In which solvent is glycerol insoluble?

CCl3 Signup and view all the answers

Which functional groups are primarily responsible for the solubility of glycerol in water?

Hydroxyl groups Signup and view all the answers

Which property classifies glycerol as hydrophobic despite its miscibility with water?

Attachment to fatty acids Signup and view all the answers

What is a notable characteristic of glycerol in terms of physical properties?

It is viscous. Signup and view all the answers

What conclusion can be drawn about the role of lipids regarding lung surfactant?

Lipids contribute to the reduction of surface tension in the lungs. Signup and view all the answers

In the context of chemical testing, what does the acrolein test specifically indicate?

Presence of lipids Signup and view all the answers

What are the primary functions of Type I pneumocytes in the alveoli?

Facilitating gas exchange Signup and view all the answers

Which lipid component is primarily responsible for the surface-active properties of lung surfactant?

DPPC (Dipalmitoylphosphatidylcholine) Signup and view all the answers

What causes alveoli to have an innate tendency to collapse?

Contribution of water vapor to surface tension Signup and view all the answers

How do Type II pneumocytes contribute to lung function?

They produce and secrete surfactant Signup and view all the answers

What is the effect of a pure film of DPPC on surface tension under dynamic compression?

Lowers surface tension to near 0 mN/m Signup and view all the answers

Which characteristic of saturated palmitic acids allows DPPC to stabilize the surface tension?

Close packed molecular arrangement Signup and view all the answers

What percentage of alveolar cells do Type II pneumocytes comprise?

5% Signup and view all the answers

What is the primary role of surfactant in the alveoli?

To reduce surface tension and prevent collapse Signup and view all the answers

What is the primary intervention for a mother with a fetus at 26 weeks gestation to prevent respiratory distress syndrome (RDS)?

Administering glucocorticoids to the mother Signup and view all the answers

How does the administration of glucocorticoids shortly before delivery affect fetal development?

It accelerates lung maturation Signup and view all the answers

What method is used to deliver surfactant in the prevention and treatment of infant RDS?

Intratracheal instillation Signup and view all the answers

Which of the following is NOT typically considered a treatment option for preventing respiratory distress syndrome in preterm infants?

Continuous positive airway pressure (CPAP) for the infant Signup and view all the answers

What is DCCP, which is facilitated by glucocorticoid administration during pregnancy?

Dipalmitoylphosphatidylcholine Signup and view all the answers

What is the primary component of lung surfactant responsible for reducing surface tension?

Dipalmitoylphosphatidylcholine (DPPC) Signup and view all the answers

During which stage of lung development do components of the surfactant system begin to appear?

Canalicular stage Signup and view all the answers

What is an indicator of fetal lung maturity that reflects the synthesis of DPPC?

L/S ratio Signup and view all the answers

Which type of cell in the alveoli is primarily responsible for gas exchange?

Type I cells Signup and view all the answers

What condition can lead to respiratory distress syndrome (RDS) due to insufficient surfactant?

Damage to surfactant-producing pneumocytes Signup and view all the answers

At approximately what gestational age does the synthesis of surfactant begin in Type II alveolar cells?

32 weeks Signup and view all the answers

What is a potential outcome of inadequate surfactant production in preterm infants?

Impaired gas exchange Signup and view all the answers

Which lipids primarily make up a significant part of lung surfactant?

Phosphatidylcholine Signup and view all the answers

Study Notes

Lipid Metabolism Overview

Lipids are crucial for various biological functions including energy storage and cell membrane structure.
Phospholipid metabolism involves surfactant production, essential for lung function.

Experimental Procedures

Total lipid extraction involves homogenizing tissue in ether-alcohol, filtering to separate lipid components.
Triglycerides are isolated using hot water bath evaporation to a syrupy consistency before testing glycerol and lecithin.
Glycerol is a polyol compound with three hydroxyl groups, making it miscible with water, while being hydrophobic due to fatty acid attachment.
Acrolein test detects glycerol by heating with potassium bisulfate (KHSO4), resulting in a pungent odor indicative of dehydration products.

Role of Lipids in Lung Surfactant

Surfactant is composed of approximately 70-80% phospholipids, mainly dipalmitoylphosphatidylcholine (DPPC), and is critical for reducing surface tension in alveoli.
Surfactant therapy effectively reduces the incidence and severity of respiratory distress syndrome (RDS) in preterm infants.
Lung maturity is assessed by the lecithin/sphingomyelin (L/S) ratio in amniotic fluid, a ratio of 2 or above signals sufficient surfactant production.

Lung Structure and Function

Alveoli, the gas exchange sites in lungs, consist of Type I and Type II epithelial cells:
- Type I cells (95%) line the alveolar walls and facilitate gas exchange.
- Type II cells (5%) synthesize and secrete surfactant.
Surfactant lowers surface tension to prevent alveolar collapse, stabilizing the alveoli's spherical shape.

Surfactant Composition

DPPC is the primary active component in surfactant, maintaining low surface tension during inhalation and exhalation.
Saturated palmitic acids in DPPC allow for organization into a stable two-dimensional gel structure at body temperature.

Prevention and Treatment of RDS

Glucocorticoids, such as hydrocortisone, administered to mothers can accelerate fetal lung maturation by enhancing DPPC production.
Natural or synthetic surfactant can be administered intratracheally to treat or prevent RDS in preterm infants, especially those born before 28 weeks of gestation.

Key Questions

Identify the epithelial cell types found in alveoli:
- Type I (gas exchange)
- Type II (surfactant production)
Significance of lung surfactant: reduces surface tension, preventing alveolar collapse and facilitating efficient gas exchange.

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Description

This quiz covers the extraction and metabolism of lipids, focusing specifically on phospholipids and sphingolipids. Participants will explore the solubility characteristics of lipids in various solvents. Dive into the fascinating world of lipid metabolism with this comprehensive quiz.