BYOD 9th Grade. Organic Molecules. Lipids

Hey hi. Here is the next topic on organic molecules. Enjoy!

Organic Molecules. Lipids

Learning outcomes

Content: to be able to distinguish different types of fats and their main functions

Language: to be able to use specific vocabulary in explaining molecules in your body; to get familiar with usage of comparative and superlative structures.

1 Team work. Answer question “Why is the river otter remains dry after swimming?”

2 Pair work. Answer questions in your notebook after reading the text.

Lipids are the one class of large biological molecules that does not include true polymers, and they are generally not big enough to be considered macromolecules. The compounds called lipids are grouped with each other because they share one important trait: they mix poorly, if at all, with water. The hydrophobic behaviour of lipids is based on their molecular structure. We will focus on the types of lipids that are most biologically important: fats, phospholipids, and steroids.Fats are large molecules assembled from smaller molecules by dehydration reactions. A fat is constructed from two kinds of smaller molecules: glycerol and fatty acids. The relatively nonpolar C-H bonds in the hydrocarbon chains of fatty acids are the reason fats are hydrophobic. In making a fat, three fatty acid molecules are each joined to glycerol by an ester linkage. Phospholipids are essential for cells because they are major constituents of cell membranes. Their structure provides a classic example of how form fits function at the molecular level. Phospholipid is similar to a fat molecule but has only two fatty acids attached to glycerol rather than three. At the surface of a cell, phospholipids are arranged in a similar bilayer. Steroids are lipids characterised by a carbon skeleton consisting of four fused rings. Cholesterol, a type of steroid, is an important molecule in animals. It is a common component of animal cell membranes and is also the compound from which other steroids, such as the vertebrate sex hormones, are made.

Questions. Pair work

1. Compare the structure of a fat with that of a phospholipid.
2. Why are human sex hormones considered lipids?
3. Suppose a membrane surrounded an oil droplet, as it does in the cells of plant seeds and in some animal cells. Draw it.

3 Individual work. Answer questions after watching the Lipids video (https://goo.gl/u9LBu1).

1. What are components of Triglycerides?
2. Rank the three types of fat in order from most to least healthy
3. Partial hydrogenation of cis (healthy) fats results in trans fats. What do you think full hydrogenation of unsaturated fats results in?