Chapter 3 The Molecules of Life Laura Coronado Bio 10 Chapter 3

Chapter 3Chapter 3

The Molecules of Life

Laura Coronado Bio 10 Chapter 3

Biology and Society: Got Lactose?– Lactose is the main sugar found in milk.– Some adults exhibit lactose intolerance, the inability to

properly digest lactose.– Lactose-intolerant individuals are unable to digest

lactose properly.• Lactose is broken down by bacteria in the large

intestine producing gas and discomfort.– There is no treatment for the underlying cause of

lactose intolerance.– Affected people must avoid lactose-containing foods or

take the enzyme lactase when eating dairy productsLaura Coronado Bio 10 Chapter 3

Figure 3.00Laura Coronado Bio 10 Chapter 3

ORGANIC COMPOUNDS

–A cell is mostly water.– The rest of the cell consists mainly of

carbon-based molecules.–Carbon forms large, complex, and diverse

molecules necessary for life’s functions.–Organic compounds are carbon-based

molecules.


Carbon Chemistry

–Carbon is a versatile atom.• It has four electrons in an outer shell that holds

eight.• Carbon can share its electrons with other atoms to

form up to four covalent bonds.

–Carbon can use its bonds to• Attach to other carbons • Form an endless diversity of carbon skeletons


Animation: Carbon Skeletons

Carbon skeletons vary in length Carbon skeletons may have double bonds,which can vary in location

Carbon skeletons may be unbranched or branched Carbon skeletons may be arranged in rings

Double bond


Hydrocarbons

– The simplest organic compounds are hydrocarbons, which are organic molecules containing only carbon and hydrogen atoms.– The simplest hydrocarbon is methane,

consisting of a single carbon atom bonded to four hydrogen atoms.


Structural formula Ball-and-stick model Space-filling model



Organic Molecule– Each type of organic molecule has a unique three-

dimensional shape.– The shapes of organic molecules relate to their

functions.– The unique properties of an organic compound depend

on• Its carbon skeleton • The atoms attached to the skeleton

– The groups of atoms that usually participate in chemical reactions are called functional groups. Two common examples are• Hydroxyl groups (-OH)• Carboxyl groups (C=O)


Giant Molecules from Smaller Building Blocks

–On a molecular scale, many of life’s molecules are gigantic, earning the name macromolecules.– Three categories of macromolecules are• Carbohydrates• Proteins• Nucleic acids


Giant Molecules from Smaller Building Blocks

–Most macromolecules are polymers.–Polymers are made by stringing together

many smaller molecules called monomers.–A dehydration reaction• Links two monomers together• Removes a molecule of water


Animation: Polymers

Short polymer Monomer

Dehydrationreaction

Longer polymer

a Building a polymer chain

Figure 3.4aLaura Coronado Bio 10 Chapter 3

Hydrolysis Reaction

–Organisms also have to break down macromolecules.–Hydrolysis• Breaks bonds between monomers• Adds a molecule of water• Reverses the dehydration reaction


Hydrolysis

b Breaking a polymer chain

Figure 3.4bLaura Coronado Bio 10 Chapter 3

LARGE BIOLOGICAL MOLECULES

– There are four categories of large molecules in cells:• Carbohydrates• Lipids• Proteins• Nucleic acids


Carbohydrates

–Carbohydrates are sugars or sugar polymers. They include• Small sugar molecules in soft drinks • Long starch molecules in pasta and potatoes


Monosaccharides–Monosaccharides are simple sugars that cannot

be broken down by hydrolysis into smaller sugars.–Glucose and fructose are isomers, molecules that

have the same molecular formula but different structures.–Monosaccharides are the main fuels for cellular

work. – In aqueous solutions, many monosaccharides

form rings.Laura Coronado Bio 10 Chapter 3

Animation: L-Dopa

Glucose Fructose

C6H12O6 C6H12O6

IsomersFigure 3.5


Glucose Fructose

C6H12O6 C6H12O6

IsomersFigure 3.5a


a Linear and ring structures

b Abbreviatedring structure


Disaccharides–A disaccharide is• A double sugar• Constructed from two monosaccharides• Formed by a dehydration reaction

–Disaccharides include• Lactose in milk• Maltose in beer, malted milk shakes, and malted

milk ball candy• Sucrose in table sugar


Animation: Disaccharides

Glucose Galactose

Lactose


Disaccharides– Sucrose is• The main carbohydrate in plant sap • Rarely used as a sweetener in processed foods

–High-fructose corn syrup is made by a commercial process that converts natural glucose in corn syrup to much sweeter fructose.– The United States is one of the world’s leading

markets for sweeteners.• The average American consumes about 45 kg of

sugar (about 100 lbs.) per year.Laura Coronado Bio 10 Chapter 3

processed to extract

broken down into

converted to sweeter

added to foods ashigh-fructose corn syrup

Starch

Glucose

Fructose

Ingredients: carbonated water,high-fructose corn syrup,caramel color, phosphoric acid,natural flavors


Polysaccharides–Polysaccharides are• Complex carbohydrates• Made of long chains of sugar units and polymers of

monosaccharides

– Starch is an example of a polysaccharide • Used by plant cells to store energy• Potatoes and grains are major sources of starch in

the human diet.


Animation: Polysaccharides

Glucosemonomer

a Starch

b Glycogen

c Cellulose

Starch granules

Glycogengranules

Cellulose fibril

Cellulosemolecules


Glycogen

–Glycogen is• Used by animals cells to store energy• Converted to glucose when it is needed


Cellulose

–Cellulose• Is the most abundant organic compound on Earth• Forms cable-like fibrils in the tough walls that

enclose plants• Cannot be broken apart by most animals


Carbohydrates in Water

–Monosaccharides and disaccharides dissolve readily in water.–Cellulose does not dissolve readily in water.–Almost all carbohydrates are hydrophilic, or

“water-loving,” adhering water to their surface.


Lipids & Fats– Lipids are• Neither macromolecules nor polymers• Hydrophobic, unable to mix with water• A typical fat, or triglyceride, consists of a glycerol

molecule joined with three fatty acid molecules via a dehydration reaction.

• Essential functions in the human body including• Energy storage• Cushioning• Insulation


Oil (hydrophobic)

Vinegar (hydrophilic)


Fatty acid

Glycerol

(a) A dehydration reaction linking a fatty acid to glycerol

(b) A fat molecule with a glycerol “head” and three energy-rich hydrocarbon fatty acid “tails”


Fatty Acid

– If the carbon skeleton of a fatty acid has• Fewer than the maximum number of hydrogens, it

is unsaturated• The maximum number of hydrogens, then it is

saturated

–A saturated fat has no double bonds, and all three of its fatty acids are saturated.


Lipids & Fats

–Most plant oils tend to be low in saturated fatty acids and liquid at room temperature.–Most animal fats• Have a high proportion of saturated fatty acids• Can easily stack, tending to be solid at room

temperature• Contribute to atherosclerosis, a condition in

which lipid-containing plaques build up within the walls of blood vessels


Hydrogenation

–Hydrogenation• Adds hydrogen• Converts unsaturated fats to saturated fats• Makes liquid fats solid at room temperature• Creates trans fat, a type of unsaturated fat that is

even less healthy than saturated fats


Saturated Fats

TYPES OF FATS

Unsaturated Fats

Margarine

Plant oils Trans fats Omega-3 fats

INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED

COTTONSEED OIL, PARTIALLY HYDROGENATED

COTTONSEED OIL AND SOYBEAN OILS, MONO AND

DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS


Figure 3.12b

Unsaturated Fats

Margarine

Plant oils Trans fats Omega-3 fats

INGREDIENTS: SOYBEAN OIL, FULLY HYDROGENATED

COTTONSEED OIL, PARTIALLY HYDROGENATED

COTTONSEED OIL AND SOYBEAN OILS, MONO AND

DIGLYCERIDES, TBHO AND CITRIC ACID ANTIOXIDANTS


Steroids– Steroids are very different from fats in

structure and function.• The carbon skeleton is bent to form four fused

rings.• Steroids vary in the functional groups attached to

this core set of rings.

–Cholesterol • A key component of cell membranes • The “base steroid” from which your body produces

other steroids, such as estrogen and testosterone


Cholesterol

Testosterone A type of estrogen


Steroids

– Synthetic anabolic steroids• Resemble testosterone• Mimic some of its effects• Can cause serious physical and mental problems• Are abused by athletes to enhance performance


THG


Proteins

–Proteins• Are polymers constructed from amino acid

monomers• Perform most of the tasks the body needs to

function• Form enzymes, chemicals that change the rate of a

chemical reaction without being changed in the process


MAJOR TYPES OF PROTEINS

Structural Proteins Storage Proteins Contractile Proteins Transport Proteins Enzymes


The Monomers of Proteins: Amino Acids

–All proteins are constructed from a common set of 20 kinds of amino acids.– Each amino acid consists of a central carbon

atom bonded to four covalent partners in which three of those attachment groups are common to all amino acids.


a The general structure of an amino acid

b Examples of amino acids with hydrophobic and hydrophilicside groups

Aminogroup

Carboxylgroup

Hydrophobicside group

Hydrophilicside group

Leucine Serine

Sidegroup


Proteins as Polymers–Cells link amino acids together by dehydration

reactions, forming peptide bonds and creating long chains of amino acids called polypeptides.– Your body has tens of thousands of different

kinds of protein.–Proteins differ in their arrangement of amino

acids.– The specific sequence of amino acids in a

protein is its primary structure.


Aminogroup

Carboxylgroup

Sidegroup

Sidegroup

Amino acid Amino acid

Sidegroup

Sidegroup

Dehydration reaction

Peptide bond

Figure 3.17-2Laura Coronado Bio 10 Chapter 3

Amino acid

1 510

20

15

253035

40

45

50 55

6065

70

75 8085

9095100

105

110 115

120125

129


Normal red blood cell

Sickled red blood cell Sickle-cell hemoglobin

b Sickle-cell hemoglobin

a Normal hemoglobin

Normal hemoglobin

1 2 3 4 5 6 7. . . 146

1 2 3 4 5 6 7. . . 146

SEM

SEM


Protein Shape–A functional protein consists of one or more

polypeptide chains, precisely folded and coiled into a molecule of unique shape.–Proteins consisting of• One polypeptide have three levels of structure • More than one polypeptide chain have a fourth,

quaternary structure–A protein’s three-dimensional shape• Recognizes and binds to another molecule• Enables the protein to carry out its specific function

in a cellLaura Coronado Bio 10 Chapter 3

a Primarystructure

b Secondary structure

Aminoacids

Pleated sheet

Alpha helix

c Tertiarystructure

Polypeptide

d Quaternarystructure

Protein withfour polypeptides

Figure 3.20-4Laura Coronado Bio 10 Chapter 3

Protein

Target


What Destroys Protein Shape?–A protein’s shape is sensitive to the

surrounding environment.–Unfavorable temperature and pH changes

can cause denaturation of a protein, in which it unravels and loses its shape.–High fevers (above 104º F) in humans can

cause some proteins to denature.


Protein Structural Errors

–Misfolded proteins are associated with• Alzheimer’s disease•Mad cow disease• Parkinson’s disease


Genetic Information–Nucleic acids are macromolecules that provide the

directions for building proteins• Include DNA and RNA• Are the genetic material that organisms inherit

from their parents– DNA resides in cells in long fibers called

chromosomes.– A gene is a specific stretch of DNA that programs

the amino acid sequence of a polypeptide.– The chemical code of DNA must be translated from

“nucleic acid language” to “protein language.”Laura Coronado Bio 10 Chapter 3

Gene

DNA

RNA

Protein

Amino acid

Nucleic acids


Nucleotides

– Nucleic acids are polymers of nucleotides.– Each nucleotide has three parts:

• A five-carbon sugar• A phosphate group• A nitrogenous base


Figure 3.23

Nitrogenous baseA, G, C, or T

Thymine T

Phosphategroup

Sugardeoxyribose

a Atomic structure b Symbol used in this book

Phosphate

Base

Sugar


DNA

– Each DNA nucleotide has one of the following bases:• Adenine (A)• Guanine (G)• Thymine (T)• Cytosine (C)


Adenine A Guanine G

Thymine T Cytosine C

Adenine A Guanine G Thymine T Cytosine C

Space-filling model of DNAFigure 3.24


DNA Linkages

–Dehydration reactions• Link nucleotide monomers into long chains called

polynucleotides• Form covalent bonds between the sugar of one

nucleotide and the phosphate of the next• Form a sugar-phosphate backbone

–Nitrogenous bases hang off the sugar-phosphate backbone.


Sugar-phosphatebackbone

NucleotideBasepair

Hydrogenbond

Bases

a DNA strandpolynucleotide

b Double helixtwo polynucleotide strands


DNA Linkages

– Two strands of DNA join together to form a double helix.–Bases along one DNA strand hydrogen-bond to

bases along the other strand.– The functional groups hanging off the base

determine which bases pair up:• A only pairs with T.• G can only pair with C.


RNA

–RNA, ribonucleic acid, is different from DNA.• RNA is usually single-stranded but DNA usually

exists as a double helix.• RNA uses the sugar ribose and the base uracil (U)

instead of thymine (T).


Phosphategroup

Nitrogenous baseA, G, C, or U

Uracil U

Sugar ribose


The Process of Science: Does Lactose Intolerance Have a

Genetic Basis?

–Observation: Most lactose-intolerant people have a normal version of the lactase gene.–Question: Is there a genetic basis for lactose

intolerance?–Hypothesis: Lactose-intolerant people have a

mutation but not within the lactase gene.


The Process of Science: Does Lactose Intolerance Have a

Genetic Basis?

–Prediction: A mutation would be found nearby the lactase gene.– Experiment: Genes of 196 lactose-intolerant

people were examined.–Results: A 100% correlation between lactose

intolerance and one mutation was found.


DNA

Human cellDNA in 46

chromosomes

Chromosome 2one DNA molecule

Section ofchromosome 2

Lactase gene

14,000 nucleotides

C at this site causeslactose intoleranceT at this site causeslactose tolerance


Evolution Connection: Evolution and Lactose Intolerance in Humans

–Most people are lactose-intolerant as adults:• African Americans and Native Americans — 80%• Asian Americans — 90%• But only 10% of Americans of northern European

descent are lactose-intolerant


Lactose Tolerance

– Lactose tolerance appears to have evolved in northern European cultures that relied upon dairy products.– Ethnic groups in East Africa that rely upon

dairy products are also lactose tolerant but due to different mutations.


Large biologicalmolecules

Functions Components Examples

Carbohydrates

Lipids

Proteins

Nucleic acids

Dietary energy;storage; plantstructure

Long-termenergy storagefats;hormonessteroids

Enzymes, structure,storage, contraction,transport, and others

Informationstorage

Monosaccharides:glucose, fructoseDisaccharides:lactose, sucrosePolysaccharides:starch, cellulose

Fats triglycerides;Steroidstestosterone,estrogen

Lactasean enzyme,hemoglobina transport protein

DNA, RNA

Monosaccharide

Components ofa triglyceride

Amino acid

Nucleotide

Fatty acid

Glycerol

Aminogroup

Carboxylgroup

Sidegroup

PhosphateBase

Sugar

Figure UN3-2Laura Coronado Bio 10 Chapter 3


Dietary energy;storage; plantstructure

Monosaccharides:glucose, fructoseDisaccharides:lactose, sucrosePolysaccharides:starch, cellulose

Monosaccharide

Carbohydrates

Figure UN3-2aLaura Coronado Bio 10 Chapter 3


Lipids

Long-termenergy storagefats;hormonessteroids

Fats triglycerides;Steroidstestosterone,estrogenComponents of

a triglyceride

Fatty acid

Glycerol

Figure UN3-2bLaura Coronado Bio 10 Chapter 3


Proteins

Enzymes, structure,storage, contraction,transport, and others

Lactasean enzyme,hemoglobina transport protein

Amino acid

Aminogroup

Carboxylgroup

Sidegroup

Figure UN3-2cLaura Coronado Bio 10 Chapter 3


Nucleic acids

Informationstorage DNA, RNA

Nucleotide

PhosphateBase

Sugar

Figure UN3-2dLaura Coronado Bio 10 Chapter 3

DNAdouble helix DNA strand DNA nucleotide

Base

Sugar

Phosphategroup

Figure UN3-4Laura Coronado Bio 10 Chapter 3

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Chapter 3 The Molecules of Life Laura Coronado Bio 10 Chapter 3