A Level Biology Lesson 9:

Lipids: The Properties of Phospholipids

Task 1. Check Where this Lesson fits into your Exam Specification!

Task 2. Watch the Revision Notes Lesson in Full.

00:00 Intro Screen / Learning Outcomes

00:52 Phospholipids (The 2nd Lipid you need to know)

01:00 Phospholipids are similar to triglycerides...

01:35 The Structure of a Phospholipid

03:16 Phospholipids are Ambivalent Molecules...

03:59 Phospholipids from monolayers (micelles)

04:36 In living Organisms Phospholipids form Bilayers

05:23 In living Organisms Phospholipids form Cell Membranes

Task 3. 

Download, Print out & complete the accompanying Interactive Worksheet.

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A-Level Biology "Lipids: The Properties of Phospholipids" Lesson 9. Summary.

Phospholipids are similar to triglycerides, but rather than having 3 fatty acids attached to glycerol, phospholipids have 2 fatty acids and a phosphate group.

 

Phospholipids are fundamental molecules in all living organisms!

 

Phospholipids are composed of the hydrophilic (water loving) phosphate head and the hydrophobic (water hating) fatty acid tails.

Phospholipids are ambivalent (i.e. a molecule that has different properties when placed in water). Because of this, when placed in water phospholipids spontaneously form monolayers known as micelles.

As we can see, micelles orientate themselves so that the hydrophilic phosphate head of the phospholipid is “facing outwards” dissolved in the water and protecting the hydrophobic fatty acid tails which are orientated “inwards”.

In living organisms, Phospholipids form Bilayers!

 

The phospholipid bilayer is the fundamental structure of all cell membranes. 

 

The Phospholipid bilayer separates the internal cellular environment from the external cellular environment. 

Check Your Spec!

★ AQA Specification Reference: - 3.1 Biological molecules: 3.1.3 Lipids. Triglycerides and phospholipids are two groups of lipid. In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group. Students should be able to: explain the properties of phospholipids.

 

★ CIE Specification Reference: - 2 Biological molecules. 2.2 Carbohydrates and lipids. lipids have important roles in the provision and storage of energy, and for a variety of other functions such as providing barriers around cells: the phospholipid bilayer. g) describe the structure of a phospholipid and relate the structure of phospholipids to their functions in living organisms.

 

★ Edexcel (Biology A – Salters-Nuffield) Specification Reference: - Topic 2: Genes and Health. 2.2 i) Know the structure and properties of cell membranes.

 

★ Edexcel (Biology B) Specification Reference: - Topic 1: Biological Molecules. iv Understand how the structure and properties of phospholipids relate to their function in cell membranes.

 

★ OCR (Biology A) Specification Reference: - Module 2: Foundations in biology - 2.1.2 Biological molecules. (j) how the properties of phospholipids relate to their functions in living organisms.

 

★ OCR (Biology B) Specification Reference: - Module 2: Cells, chemicals for life, transport and gas exchange. (j) how the plasma membrane is composed of modified lipids and how the structure of phospholipids is related to their functions. (k) the fluid mosaic model of the typical plasma membrane, to include the location and function of phospholipids.

 

★ WJEC Specification Reference: - Core Concepts 1. Chemical elements are joined together to form biological compounds (f) the structure, properties and functions of lipids as illustrated by triglycerides and phospholipids.

 

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