adv. nitrition lecture 20

Attendance and Participation

• Attendance is mandatory for evaluations.

• Medical documentation is required for absences due to illness.

• Participation in peer evaluations is essential, as you will actively be involved in grading classmates' presentations.

Presentation Submission Guidelines

• Groups of two must submit two files per person on the Moodle site.

• Ensure both your name and your partner’s name are included on submissions for grading purposes.

• Comments and evaluations of presentations are to be included as part of the submission process.

Evaluation Criteria

• Avoid uniform grading (e.g., all 5’s). Provide thoughtful assessments based on individual contributions.

• Aim for professionalism in grading; personal feelings should not influence evaluation results.

Course Schedule Adjustments

• The instructor indicated potential changes in class schedules (e.g., Monday class) due to holiday considerations.

Digestive Processes Overview

• Recap on digestion of lipids, specifically triglycerides and phospholipids.

• Understanding of enzymes involved (e.g., pancreatic lipase) and digestion products (e.g., micelles).

Micelle Formation and Function

• Micelles are negatively charged aggregates formed from digestion products.

• Essential for the emulsification of lipids to facilitate further digestion.

• Micelles allow products of lipid digestion to be absorbed into enterocytes (intestinal cells).

Absorption Mechanisms

• Two mechanisms for lipid absorption into enterocytes:

  • Protein-Independent Diffusion:

    • Involves diffusion of lipid products without protein assistance.

    • Allows fatty acids, MAG, and lysophospholipids to enter through similar amphipathic nature of membranes.

  • Protein-Dependent Transport:

    • Requires transport proteins (e.g., CD36) to facilitate absorption.

    • Protein-dependent pathways help move fatty acids and some phospholipids across membranes.

Post-Absorption Processing

• Once in enterocytes, dietary lipids are re-esterified and packaged for transport into the bloodstream via chylomicrons.

• Chylomicrons are reassembled lipids (e.g., TAGs) combined with proteins for solubility in blood.

Cholesterol Absorption

• Cholesterol is absorbed or secreted.

• Efficiency of absorption is crucial for maintaining cholesterol balance in the body.

• Some cholesterol can become incorporated into enterocyte membranes.

Chylomicrons

• Chylomicrons are lipid-protein complexes that transport dietary fats through the bloodstream.

• Their composition reflects dietary intake (triglycerides, cholesterol).

Lipoprotein Classes

• Different types of lipoproteins, including very low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and high-density lipoprotein (HDL), each with specific functions and lipid compositions.

• Density of lipoproteins varies with lipid-to-protein ratios; higher lipid content leads to lower density.

Clinical Applications

• Medium-chain fatty acids (MCFAs) can bypass normal absorption processes and be used in treatments for intestinal disorders.

• Exploring strategies to lower blood cholesterol by using phytosterols or other blockers (e.g., ezetimibe) to prevent cholesterol absorption.

Key Points to Remember for Exams:

• Importance of micelle in absorption, mechanisms of lipid absorption, roles of different proteins, and understanding of chylomicron functions.

• Grading policies and participation in peer evaluations as part of course requirements.