Exam 2: Lipids

Week 7 pt 2, Week 8 all slides

lipids found in biological systems exist in two forms:

1. completely hydrophobic (only nonpolar groups)

2. amphipathic/ampiphilic

the nature of the lipid molecule is a highly ___ form of carbon, largely hydrocarbon based; and therefore has very ____ water solubility

reduced; poor

Fatty acids are characterized by (2 things):

1. long hydrocarbon chain

2. terminal carboxyl group (in the ionized form @ physiological conditions)

Many fatty acids have an ___ number of carbon atoms (##-##)

even; 14-24

There are two types of fatty acids:

1. saturated (only C-C single bonds)

2. unsaturated (one or more C=C double bonds)

one C=C means the fatty acid is ________

monounsaturated

more than one C=C means the fatty acid is ____

polyunsaturated

Fatty acids can be named in three ways:

1. systematic name

2. common name

3. *shorthand notation*

systematic name

naming based on the number of carbons in the hydrocarbon tail and whether or not it is saturated (-anoic acid) or unsaturated (-enoic acid)

common name examples

steric acid, oleic acid

shorthand notation consists of two parts:

number of carbon atoms : number of double bonds (ex. 18:1)

delta nomenclature

extension of shorthand notation that specifies the location of the C=C double bond, written using the symbol delta

• start counting from the COOH group

• if multiple, add commas

What is the delta nomenclature for this fatty acid?

18:3 ∆^9,12,15

Saturated fatty acids are extremely _____ molecules, and they can rotate about ____ bonds. But the prefer the _____ conformation since it limits _____ strain.

flexible; C-C single; extended; stericF

Fatty acids are more ____ in nature and tend to be ___ at room temp with ____ melting points

rigid; solid; higher

the double bonds in unsaturated fatty acids typically result in the ___ conformation, causing a visible ____

cis; kink

properties of unsaturated fatty acids (4)

1. cannot pack well

2. more flexible and fluid

3. liquid at room temp

4. lower melting point

Cell membranes have lipids that are _____ to avoid breaking

unsaturated

When you increase the carbon chain length, the melting point ____, because more _____ forces between C-C must be broken

increases; attractive

When you increase the number of double bonds, the melting point _____ because more bends _____ strong C-C attractions and increase _____

decreases; reduce; fluidity

Essential fatty acids

fatty acids that are not synthesized by mammals but are necessary for growth and life; must be obtained by food

The function of essential fatty acids is to…

be a precursor to the synthesis of compounds that exert hormonelike effects

Dietary fatty acids

fats in modern diet, include saturated and unsaturated

Most unsaturated fatty acids exist in the ____ form, but ____ fatty acids can be formed by some bacteria naturally in _____ animals

cis; trans; ruminant

margarine and other processed fats are made by a ____ ______ reaction of polyunsaturated oils that contain high amounts of ____ fats

partial hydrogenation; trans

Fat hydrogenation is used for many reasons:

1. extends shelf life

2. changes texture so it is now solid at room temp

3. these hurt our ability to remove LDL cholesterol from the body

A triacylglycerol consists of one ___ molecule and 3 ___ ___ molecules that combine in the presence of a catalyst, forming ______ and _____

glycerol; fatty acid; triacylglycerol; water

the two classifications of triacylglycerols

1. simple (all saturated or all unsaturated)

2. mixed (some saturated and some unsaturated)

Hydrolysis of triglycerides breaks the ___ linkage

ester

Saponification

hydrolysis of triglycerides in alkaline conditions

Triacylglycerols are a major ____ reserve in animals; stored in _____ tissue, and it is the most ____ form of carbon in molecules

energy; adipose; reduced

oxidation of 1g TAGs = _____ kJ of energy

38

Glycerophospholipid

a 1,2-diacylglycerol that has a phosphate group esterified at carbon 3 of the glycerol backbone

A glycerophospholipid consists of:

1. two fatty acid chains hanging off glycerol backbone, at carbons 1 and 2

2. a PO₄^3- that when added, creates a phospho-ester linkeage

Glycerophospholipids are essential in our _____ ______

cell membranes

the naming format for glycerophospholipids

phosphatidyl + name of group

The head group

the phosphate group and the esterified entity in a glycerophospholipid

snake venom contains _______ enzymes that breaks the fatty acid at ___

phospholipase; C2

Lysophospholipid

the result of hydrolysis form snake venom; doesn’t fit into membrane and causes it to rupture

Ether glycerophospholipids

glycerophospholipid that occurs at C1, where it has an ether linkage in place of an acyl linkage off the glycerol backbone

an important ether glycerophospholipid is the _____-_____ factor

platelet-activating factor

Sphingolipid

a second class of lipids in biological membranes, consisting of a sphingosine molecule and a fatty acid

Gangliosides

a more complex glycosphingolipid that consists of a ceramide backbone with three or more sugars esterified; present in nerve endings

Steroids

lipid with a distinct fused tetracyclic structure

the rings in a steroid molecule include;

1. three 6-membered rings

2. one 5-membered ring

3. ring A is sometimes aromatic

Steroids often have substituents at positions…

10: methyl or hydrogen

3: methyl group

17: different group that is larger than a methyl

Androgens

steroids derived from cholesterol in animals that mediate development of sexual characteristics and particular functions

Testosterone

the male sex hormone

Estradiol

the female sex hormone

Progesterone

the precursor for both testosterone and estradiol

Glucocorticoids

steroids that regulate protein, carbohydrate, and lipid metabolism

Mineralcorticoids

steroids that regulate salt balance in tissues

Bile acids

detergent-like molecules that are secreted into the bile from the gallbladder; help absorb any dietary lipid that is nonpolar

external source of cholesterol

dietary sources (food)

internal sources of cholesterol

cholesterol made within the body (mostly the liver)

Atheroscelrosis

a disease in which plaque builds up inside the arteries, where the plaque hardens and narrows the arteries over time