Chapter 15: Lipids

Lipids

Lipids

These are a family of biomolecules that have the common property of being soluble in organic solvents but not in water.

nonpolar solvent

The lipid content of a cell can be extracted using a ____ such as ether or chloroform.

hydrolyzed

Lipids such as waxes, fats, oils, and phospholipids are esters that can be _____ to give fatty acids along with other molecules.

Fatty Acid

It contains a long, unbranched carbon chain with a carboxylic acid group at one end.

Saturated Fatty Acid

It contains only carbon–carbon single bonds, which make the properties of a long-chain fatty acid similar to those of an alkane.

Unsaturated Fatty Acid

• It contains one or more carbon–carbon double bonds.

  • It can be drawn as cis and trans isomers.

Monosaturated Fatty Acid

The long carbon chain has one double bond, which makes its properties similar to those of an alkene.

Polyunsaturated Fatty Acid

It has at least two carbon–carbon double bonds.

Prostaglandins

• These are hormone-like substances produced in small amounts in most cells of the body.

• These are also known as eicosanoids; which are formed from arachidonic acid, the polyunsaturated fatty acid with 20 carbon atoms.

Wax

An ester of a saturated fatty acid and a long-chain alcohol, each containing from 14 to 30 carbon atoms.

Natural waxes

These waxes are found on the surface of fruits, and on the leaves and stems of plants where they help prevent loss of water and damage from pests.

waterproof coating

Waxes on the skin, fur, and feathers of animals provide a _____.

Triacylglycerols

This is where fatty acids are stored, which are triesters of glycerol and fatty acids.

Fat

A triacylglycerol that is solid at room temperature, and it usually comes from animal sources such as meat, whole milk, butter, and cheese.

Oil

A triacylglycerol that is usually a liquid at room temperature and is obtained from a plant source.

Hydrogenation

• In this reaction, hydrogen gas is bubbled through the heated oil typically in the presence of a nickel catalyst.

• H atoms add to one or more carbon–carbon double bonds to form carbon–carbon single bonds.

lipases

Triacylglycerols are hydrolyzed in the presence of strong acids or _____.

hydrolysis

The products of _____ of the ester bonds are glycerol and three fatty acids.

polar glycerol

The _______ is soluble in water, but the fatty acids with their long hydrocarbon chains are not.

Saponification

It occurs when a fat is heated with a strong base.

softer soap

An oil that is polyunsaturated produces a ______.

Phospholipids

These are a family of lipids similar in structure to triacylglycerols; they include glycerophospholipids and sphingomyelins.

glycerophospholipid

In ______, two fatty acids form ester bonds with the first and second hydroxyl groups of glycerol.

sphingomyelin

In _____, sphingosine replaces glycerol.

Lecithins

Cephalins

These are two types of glycerophospholipids that are particularly abundant in brain and nerve tissues as well as in egg yolks, wheat germ, and yeast.

Glycerophospholipids

______ contain both polar and nonpolar regions, which allow them to interact with both polar and nonpolar substances.

phospholipases

The venom of the eastern diamondback rattlesnake and the Indian cobra contains ______, which are enzymes that catalyze the hydrolysis of the fatty acid on the center carbon of glycerophospholipids in the red blood cells.

Lysophospholipid

It causes the breakdown of the red blood cell membranes. This makes them permeable to water, which causes hemolysis of the red blood cells.

Steroids

These are compounds containing the steroid nucleus, which consists of three cyclohexane rings and one cyclopentane ring fused together.

Cholesterol

• It is one of the most important and abundant steroids in the body, is a sterol because it contains an oxygen atom as a hydroxyl group on carbon 3.

• It is a component of cellular membranes, myelin sheath, and brain and nerve tissue.

Bile Salts

These are synthesized from cholesterol in the liver and stored in the gallbladder.

Lipoproteins

They are made more soluble by combining them with phospholipids and proteins to form water-soluble complexes.

Hormones

These are chemical messengers that serve as a communication system from one part of the body to another

Steroid Hormones

These are closely related in structure to cholesterol and depend on cholesterol for their synthesis (sex hormones and adrenocortical hormones).

testosterone

androsterone

Two of the male sex hormones that promote the growth of muscle and facial hair, and the maturation of the male sex organs and of sperm.

Estrogens

A group of female sex hormones, direct the development of female sexual characteristics.

Progesterone

It prepares the uterus for the implantation of a fertilized egg.

Corticosteroids

Produced by the adrenal glands.

Cortisone

It increases the blood glucose level and stimulates the synthesis of glycogen in the liver.

Aldosterone

It is responsible for the regulation of electrolytes and water balance by the kidneys.

Cortisol

It is released under stress to increase blood sugar and regulate carbohydrate, fat, and protein metabolism.

Prednisone

These are synthetic corticosteroid drugs that are derived from cortisone and used medically for reducing inflammation and treating asthma and rheumatoid arthritis, although health problems can result from long-term use.

glycerophospholipids

sphingolipids

The main components of a cell membrane.

Lipid Bilayer

The double-layer arrangement of phospholipids.

fluid mosaic model

The model of biological membranes is referred to as the _____ of membranes.

peripheral proteins

In the fluid mosaic model, proteins known as _______ emerge on just one of the surfaces, outer or inner.

integral proteins

The _____ extend through the entire lipid bilayer and appear on both surfaces of the membrane.

Diffusion Transport

Molecules can diffuse from a higher concentration to a lower concentration.

Facilitated Transport

Proteins that extend from one side of the bilayer membrane to the other provide a channel through which certain substances can diffuse more rapidly than by passive diffusion to meet cellular needs.

active transport

In the conduction of nerve impulses and contraction of muscles, K+ moves into the cell, and Na + moves out by ______.