Lipids- Does this molecule make me look fat? A.P. Biology Chapter 3 Liberty Senior High School Mr. Knowles

Lipids Have C, H, O, but more H and less O than carbohydrates. Four Kinds: Fats, Phospholipids, Terpenes, Steroids Functions of Lipids: 1. May form cell membranes. 2. Used for long- term energy storage.

1. Fats A Fat = Glycerol + 1 or more Fatty Acids Glycerol- a 3 carbon alcohol. Fatty Acid- HO - C - R O Where R = hydrocarbon chain.

Synthesis of a Fat Dehydration Synthesis - removing H 2 O and forming an ester bond between the OH of glycerol and the carboxyl group of a fatty acid.

Fats: are constructed from two types of smaller molecules, a single glycerol and usually three fatty acids. (b) Fat molecule (triacylglycerol) H H H H H H H H H H H H H H H H O Figure 5.11

A Glycerol Three Fatty Acids

Types of Fatty Acids Saturated Fatty Acids- single-bonded hydrocarbon chains completely filled with H. Solids at Room Temp. Usually from animals. Ex. Lard Unsaturated Fatty Acids- usually contain a double bond within the hydrocarbon chain, at least one carbon may bond with a H. Liquids at room temp. Derived from plants. Ex. Veg. Oil

Saturated Fatty Acids: -have the maximum number of hydrogen atoms possible. -have no double bonds. (a) Saturated fat and fatty acid Stearic acid Figure 5.12

Unsaturated Fatty Acids: –Have one or more double bonds. (b) Unsaturated fat and fatty acid cis double bond causes bending Oleic acid Figure 5.12

Steric Acid- a saturated fatty acid.

Show me oleic acid- an unsaturated fatty acid.

What does an unsaturated fat look like?

How does olestra compare to real fats?

So what is Peanut Butter? If it comes from a plant, it should be a(n)…. Unsaturated Fat! But it’s a solid! It is a hydrogenated fat!

The Importance of Fats Efficient energy-storage molecules because of high # of C-H bonds. More than twice the # in carbos. Convert unused glucose into starch or fats. Fats = 9 kcal/g; Carbo = 4 kcal/g Energy in Saturated fats > Unsaturated fats

So what does this mean for living organisms? The Big Picture! Show the movie! Discovery Channel- Grizzly: Face to Face

The Importance of Lipids for Survival Video: Discovery- Blue Planet: Frozen Seas

2. Phospholipids Substitute a phosphate (PO 4 ) for one fatty acid in a triglyceride. The (PO 4 ) group is polar (charged). The polar ends interact with each other- Hydrophilic The nonpolar (uncharged) hydrocarbon chains interact- Hydrophobic Found in all cell membranes.

Phospholipid structure: –Consists of a hydrophilic “head” and hydrophobic “tails.” CH 2 O P O O O CH CH 2 OO C O C O Phosphate Glycerol (a) Structural formula (b) Space-filling model Fatty acids (c) Phospholipid symbol Hydrophobic tails Hydrophilic head Hydrophobic tails – Hydrophilic head CH 2 Choline + Figure 5.13 N(CH 3 ) 3

Phospholipids

A Phospholipid

A spontaneous barrier?

Micelles

The structure of phospholipids: –Results in a bilayer arrangement found in cell membranes. Hydrophilic heads WATER Hydrophobic tails Figure 5.14

Phospholipids form a lipid bilayer for cell membranes

Phospholipid Bilayer

Phospholipid Bilayers are 3-Dimensional!

The lipid bilayer allows nonpolar molecules to freely enter cells- “like dissolves like.”

3. Terpenes Long chain lipids; many CH bonds. Many photosynthetic pigments are terpenes. Examples are the cholorophyls and carotenes. Rubber is a terpene.

4. Steroids and other ringed lipids Four-ringed Structures. Ex. Cholesterol, hormones, vitamin D Animal cell membranes contain cholesterol, most bacteria do not.

Steroids

Who cares? How does all of this relate to biology?

Lipids are Effective Barriers At the cellular level – phospholipids. A waxy covering on the epidermis of plants – cutin. Coating of bird wings – oils.

Other Importants Fats provide a way of absorbing and storing fat- soluble vitamins A, D, E, K.

DDT: a fat-soluble poison and the osprey