Lipids and Nucleic Acids

Nestor T. Hilvano, M.D., M.P.H.(Images Copyright Discover Biology, 5th ed., Singh-Cundy and Cain,

Textbook, 2012.)

Learning Objectives

1. Describe the 4 major types of lipid molecules as to structures and functions.

2. Differentiate saturated and unsaturated fats. Give its importance.

3. What are the functions of cholesterol in human? 4. Discuss the effects of too much cholesterol in

blood. 5. Describe the health risk associated with the use

of anabolic steroids.6. Describe the structure and function of nucleic

acids.

Lipids • Insoluble in water = _______________• Compose mainly of carbon and hydrogen atoms

linked by nonpolar covalent bonds• Long term energy storage

• 4 types of lipids 1. fats and oils (triglycerides)

2. Phospholipids 3. steroids

4. waxes

Functions of Lipids1. mainly for storage of energy

2. insulate the body and cushion vital organs

3. cell membrane structure (phospholipids)

4. lipid hormones (steroids)

5. interactions with vitamins

6. Water repellant (waxes) * Energy value of Lipid = 9 kcal/g

Triglycerides (Fats & Oils)• Structure is made of 3 fatty acids attached to a

glycerol backbone• What lipid is tested in blood examination?

Saturated Fats• ___________ bond between carbons

• ___________ number of hydrogen atoms.

• ___________ physical state at room temp. • i.e. animal fats (butter, lard, human fat)

http://www.fishoilbenefits.tk/saturated-fatty-acids.html

Unsaturated Fats• __________ bonds between carbons• __________ number of hydrogen atoms • __________ physical state at room temp. • i.e. Plant fats (coconut, peanut, safflower, corn, and olive oil)• Monosaturated= single C=C; Polysaturated= more than a

single C=C bond in chain

Unsaturated Fats• Hydrogenation is the process of converting

unsaturated fats to saturated fats by adding hydrogen• Hydrogenating vegetable oils (liquid) creates

unsaturated fats with trans double bond (Margarine) • What are the implications of diet rich saturated fats

and trans fats in a person.

Phospholipids • Major component of cell membrane• Structure is made up of glycerol, 2

fatty acids and a phosphate group• Phosphate group and its attachment

form the hydrophilic head; 2 fatty acids are hydrophobic tails

• Emulsion- oil and water (don’t mix); emulsification-soluble in both (lecithin in egg yolk in mixture of mayonnaise)

Waxes

• Structure made up of one fatty acid linked to an alcohol

• More hydrophobic than fats

• Form protective coverings for ______ and _________

• i.e. beeswax, carnuba wax, spermaceti

Steroids • Lipids with 4 fused carbon rings, based on

cholesterol structure • All steroids have the same ring pattern

Cholesterol • Importance: Important steroid, found in animal

cell membrane; precursor to sex hormones and vitamin D

• Lipoproteins -carry lipids (including cholesterol) around in the blooda) LDL – bad cholesterolb) HDL – good cholesterol

Nucleic Acids • 2 types = _______ & ______ • What is the building blocks of

nucleic acids? • Each nucleotide contains:

a) nitrogenous base

b) pentose sugar

deoxyribose in DNA

ribose in RNA

c) phosphate group –to linked

sugars

Nitrogenous Bases• Purines (double ring)

- Adenine

- Guanine• Pyrimidines (single ring)

- Uracil

- Thymine

- Cytosine• DNA bases = A-T; C-G• RNA bases = A-U; C-G

DNA Structure and Function• Watson and Crick- double helix model• Features: double stranded, run in opposite

direction• Function: Genetic make-up• Genes are made up of DNA (in nucleus)

G C

T A

A T

G

G

C

C

A T

GC

T A

T A

A T

A T

G C

A T

O

O

OH–

O

P

O O–

O

PO

OOP–

O

–

OO

PO O

O

OH

H2

C

H2

C

H2

C

H2

C

O

O

O

O

O

O

O

O

PO

–

O–

O–

O–

OH

HO

O

O

O

P

P

P

O

O

O

O

O

O

O

O

T A

G C

C G

A T

CH

2

CH

2

CH

2

CH

2

Hydrogen bond

Basepair

Ribbon model

Partial chemical structure

Computer model

RNA Structure and Function• Smaller than DNA• # of nucleotide chain =

single stranded, but can loop back due to H bonds

• Function- direct synthesis of protein in the cytoplasm

Homework 1. Compare and contrast triglycerides (fats), phospholipids,

waxes, and steroids as to structural components.

2. What is hydrogenation?

3. What is the building block of lipids? What is the building block of nucleic acids?

4. Differentiate saturated fat from unsaturated fats.

5. Discuss the health implications of high level of saturated fats, trans fats, and LDL (low density lipoprotein) in human.

6. Compare and contrast DNA and RNA according to number of strand, sugar component, and base pairs.