chapter 2 pt 3

Copyright © 2009 Pearson Education, Inc..

Including the lecture Materials of

Gregory AhearnUniversity of North Florida

with amendments andadditions by

John Crocker

Chapter 2pt 3

Atoms, Molecules, and Life

Copyright © 2009 Pearson Education Inc.

2.5 How Are Biological Molecules Joined Together Or Broken Apart? Biomolecules are polymers (chains) of

subunits called monomers A huge number of different polymers can be

made from a small number of monomers Biomolecules Are Joined Through

Dehydration and Broken by Hydrolysis


Organic Molecule Synthesis

Monomers are joined together through dehydration synthesis An H and an OH are removed, resulting in the

loss of a water molecule (H2O)



Polymers are broken apart through hydrolysis (“water cutting”) Water is broken into H and OH and used to

break the bond between monomers



All biological molecules fall into one of four categoriesCarbohydratesLipidsProteinsNucleic Acids


2.6 What Are Carbohydrates?

Composition:C, H, and O in the ratio of 1:2:1

Construction: Simple or single sugars are

monosaccharides Two linked monosaccharides are

disaccharides Long chains of monosaccharides are

polysaccharides


Monosaccharides

Basic monosaccharide structure Backbone of 3-7 carbon atoms Many –OH and –H functional groups Usually found in a ring form in cells

Simple sugars provide important energy sources for organisms.

Most small carbs are water-soluble due to the polar OH functional groups


A simple sugar

Fig. 2-13

Glucose, linear form Glucose, ring form(a) (b)H

H

CH2OH

HO

OH

OH

O

H H

OH H

2356 4 1

H H H H

H

H

H

H

H H

H

H

O OOOO

O

CCCCCC


Monosaccharides

Example monosaccharides continued Fructose (found in corn syrup and fruits) Galactose (found in lactose) Ribose and deoxyribose (found in RNA and

DNA)


Most small carbs are water-soluble due to the polar OH functional groups


Disaccharides

Disaccharides are two-part sugars Sucrose (table sugar) = glucose + fructose Lactose (milk sugar) = glucose + galactose Maltose (malt sugar)= glucose + glucose


Manufacture of a disaccharide

Fig. 2-14

glucose fructose sucrose

dehydrationsynthesis

OHO

OHOCH2

OH

HO

CH2OH

H H

OH

H OH

H

H

O HO

OCH2OH

H H

OH

H OH

H

HH

H

H

HOCH2OHH

HOCH2 H

H

H

HOCH2OH

O

OH

O

+

OHH


Polysaccharides

Monosaccharides are linked together to form chains (polysaccharides)

Polysaccharides are used for energy storage and structural components


Polysaccharides

Storage polysaccharides Starch (polymer of glucose)

Formed in roots and seeds as a form of glucose storage

Glycogen (polymer of glucose)Found in liver and muscles


Polysaccharides

Structural polysaccharides Cellulose (polymer of glucose) Found in the cell walls of plants

Indigestible for most animals due to orientation of bonds between glucoses


Polysaccharides

Structural polysaccharides continued Chitin (polymer of modified glucose units)

Found in the outer coverings of insects, crabs, and spiders

Found in the cell walls of many fungi


2.7 What Are Lipids?

Molecular characteristics of lipids Lipids are molecules with long regions

composed almost entirely of carbon and hydrogen.

The nonpolar regions of carbon and hydrogen bonds make lipids hydrophobic and insoluble in water.


What Are Lipids?

Lipids are diverse in structure and serve in a variety of functions Energy storage Waterproofing Membranes in cells Hormones


Lipid classification Group 1: Oils, fats, and waxes Group 2: Phospholipids Group 3: Steroids


Group 1: Oils, fats, and waxes Formed by dehydration synthesis

3 fatty acids + glycerol triglyceride Contain only carbon, hydrogen, and oxygen Contain one or more fatty acid subunits in

long chains of C and H with a carboxyl group(–COOH)

Ring structure is rare


Group 1: Oils, fats, and waxes (continued) Fats and oils form by dehydration synthesis

from three fatty acid subunits and one molecule of glycerol.

Fig. 2-16

glycerol fatty acids

CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O

CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O

CH2CHO CH2 CH2 CH2 CH2 CH2 CH2 CHO

C OHHH

C OHH

C OHHH

CH2CH

CH2

CH2

etc.

+


triglyceride 3 watermolecules

OHH

OHH

OHH

+

+

CH2C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 etc.O

CH2C CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2

CH2

CH2 etc.O

CH2C CH2 CH2 CH2 CH2 CH2 CH2 CHO

CHH

CH

C

O

O

OHH

CH2CH

CH2

CH2

etc.

+

Group 1: Oils, fats, and waxes (continued) Fats and oils formed by dehydration synthesis

are called triglycerides. Triglycerides are used for long-term energy

storage in both plants and animals.

Fig. 2-16


Group 1: Oils, fats, and waxes (continued) Characteristics of fats

Solidity is due to the prevalence of single or double carbon bonds

Fats are solid at room temperature. Fats have all carbons joined by single covalent

bonds. The remaining bond positions on the carbons are

occupied by hydrogen atoms.


Beef fat (saturated)(a)

Group 1: Oils, fats, and waxes (continued) Fatty acids of fats are said to be saturated and

are straight molecules that can be stacked.

Fig. 2-18a


Group 1: Oils, fats, and waxes (continued) Characteristics of oils

Oils are liquid at room temperature.Some of the carbons in fatty acids have

double covalent bonds.There are fewer attached hydrogen atoms,

and the fatty acid is said to be unsaturated.


Group 1: Oils, fats, and waxes (continued) Unsaturated fatty acids have bends and kinks

in fatty acid chains and can’t be stacked.

Fig. 2-18b

Peanut oil (unsaturated)(b)


Group 1: Oils, fats, and waxes (continued) Characteristics of waxes

Waxes are solid at room temperature.Waxes are highly saturated.Waxes are not a food source.Waxes are composed of long hydrocarbon

chains and are strongly hydrophobic


Group 1: Oils, fats, and waxes (continued) Waxes form waterproof coatings

Leaves and stems of plantsFur in mammals Insect exoskeletons

Used to build honeycomb structures


Group 1: Oils, fats, and waxes (continued) Bees use waxes to store food and honey.

Fig. 2-17b


Group 2: PhospholipidsPhospholipids: form dual layered plasma

membranes around all cells Construction

like oils except one fatty acid is replaced by a phosphate group attached to glycerol.

2 fatty acids + glycerol + a short polar functional group

water-soluble heads and water-insoluble tails.


polar head glycerol

(hydrophilic) (hydrophobic)

fatty acid tails

CH3 O–

OO

CH3

CH CH2CH2

CH2CH2

CH2CH2

CH2CH3

H3C N+- CH2 - CH2 -O-P-O-CH2 O

HC-O-C-CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH

H2C-O-C- CH2 -CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 - CH2 -CH3

-

Group 2: Phospholipids (continued) The phosphate end of the molecule is water

soluble; the fatty acid end of the molecule is water insoluble.

Fig. 2-19


Group 3: Steroids Steroids contain four fused carbon rings. Various functional groups protrude from the

basic steroid “skeleton”. Examples of steroids

CholesterolFound in membranes of animal cells

Male and female sex hormones


2.8 What Are Proteins? Functions of proteins

Proteins act as enzymes to catalyze (speed) many biochemical reactions.

They provide structure (ex/ elastin) They can act as energy stores. They are involved in carrying oxygen around

the body (hemoglobin). They are involved in muscle movement.


Some proteins are structural and provide support in hair, horns, spider webs, etc.

Fig. 2-21


Proteins are formed from chains of amino acids.

All amino acids have the same basic structure: A central carbon An attached amino group An attached carboxyl group An attached variable group (R group)

Some are hydrophobicSome are hydrophilic

aminogroup

hydrogen

variablegroup

carboxylicacid group


Amino acid monomers join to form chains by dehydration synthesis. Proteins are formed by dehydration reactions

between individual amino acids. The –NH2 group of one amino acid is joined to

the –COOH group of another, with the release of H2O and the formation of a new peptide (two or more amino acids).

The resultant covalent bond is a peptide bond


Long chains of amino acids are known as polypeptides or just proteins


The sequence of amino acids in a protein dictates its three dimensional structure

This structure gives proteins their functions. Long chains of amino acids fold into three-

dimensional shapes in cells, which allows the protein to perform its specific functions.

When a protein is denatured, its shape has been disrupted and it may not be able to perform its function.


Four Levels of Structure

Proteins exhibit up to four levels of structure Primary structure is the sequence of amino

acids linked together in a protein Secondary structures are helices and

pleated sheets Tertiary structure refers to complex foldings

of the protein chain held together by disulfide bridges, hydrophobic/hydrophilic interactions, and other bonds

Quaternary structure is found where multiple protein chains are linked together


Three Dimensional Structures

The type, position, and number of amino acids determine the structure and function of a protein Precise positioning of amino acid R groups

leads to bonds that determine secondary and tertiary structure

Disruption of these bonds leads to denatured proteins and loss of function


2.9 What Are Nucleic Acids?

Structure of nucleic acids Nucleic acids are long chains of similar, but

not identical, subunits called nucleotides.



Structure of nucleic acids (continued) All nucleotides have three parts.

A five-carbon sugar (ribose or deoxyribose)A phosphate groupA nitrogen-containing molecule called a

base


phosphate

base

sugar

P O

O

OCH2

H

OH

H HH

H

OH

HO

C

N CH

NC

C

NHC

N

NH2


Deoxyribose nucleotide

Fig. 2-25



Types of nucleotides Those that contain the sugar ribose. Those that contain the sugar deoxyribose. Nucleotides string together in long chains as

nucleic acids with the phosphate group of one nucleotide bonded to the sugar group of another.


phosphate

base

sugar


Nucleotide chain

Fig. 2-26



DNA and RNA, the molecules of heredity, are nucleic acids. There are two types of nucleic acids.

Deoxyribonucleic acid (DNA): contains the genetic code of cell

Ribonucleic acid (RNA): is used in the synthesis of proteins



Other nucleotides perform other functions. Adenosine monophosphate: acts as a

messenger in the cell, carrying information to other molecules

Adenosine triphosphate: carries energy from place to place in the cell


Section 3.6 Outline

What Are Nucleic Acids? Structure of Nucleic Acids DNA and RNA, the Molecules of Heredity, Are

Nucleic Acids Other Nucleotides Act as Intracellular

Messengers, Energy Carriers, or Coenzymes


What Are Nucleic Acids?

Nucleotides are the monomers of nucleic acid chains


What Are Nucleic Acids?

All nucleotides are made of three parts Phosphate group Five-carbon sugar Nitrogen-containing base


Molecules of Heredity

Two types of nucleotides Ribonucleotides (A, G, C, and U) found in

RNA Deoxyribonucleotides (A, G, C, and T) found

in DNA



Two types of polymers of nucleic acids DNA (deoxyribonucleic acid) found in

chromosomes Carries genetic information needed for

protein construction RNA (ribonucleic acid)

Copies of DNA used directly in protein construction



Each DNA molecule consists of two chains of nucleotides that form a double helix


Other Nucleotides

Nucleotides as intracellular messengers Cyclic nucleotides (e.g. cyclic AMP) carry

chemical signals between molecule


Other Nucleotides

Nucleotides as energy carriers Adenosine triphosphate (ATP) carries

energy stored in bonds between phosphate groups

NAD+ and FAD carry electrons


Other Nucleotides

Nucleotides as enzyme assistants Coenzymes help enzymes promote and guide

chemical reactions

chapter 2 pt 3

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