copyright © 2005 pearson education, inc. publishing as benjamin cummings pre quiz – share a sheet...

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Pre Quiz –

• Share a sheet a paper so everyone has a half sheet. Fold your half in half and number to 9.

• Turn to question 20 in your lecture guide. Take 5 minutes and see how many of these you can answer.

• Use your reading guide if you have it.


1. Overview: The Molecules of Life

• Within cells, small organic molecules are joined together to form larger molecules

• The four classes include:

– Carbohydrates, Lipids, Proteins, Nucleic Acids

• Macromolecules are large molecules composed of thousands of covalently connected atoms


2-3. Concept 5.1: Most macromolecules are polymers, built from monomers

• Three of the four classes of life’s organic molecules are polymers:

– Carbohydrates

– Proteins

– Nucleic acids

• A polymer is a long molecule consisting of many similar building blocks called monomers


4,5,6. The Synthesis and Breakdown of Polymers

• Monomers link up by condensation reactions called dehydration reactions

• Polymers are broken down to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction

• Hydro- water

• Lysis – break

Animation: Polymers

LE 5-2

Short polymer Unlinked monomer

Dehydration removes a watermolecule, forming a new bond

Dehydration reaction in the synthesis of a polymer

Longer polymer

Hydrolysis adds a watermolecule, breaking a bond

Hydrolysis of a polymer


7. Consider the reaction

• Where does the water go?

• What kind of reaction is it?

• Is glucose a monomer or polymer?

• To summarize, when two monomers are joined, a molecule of _________is always removed.


The Diversity of Polymers

• Each cell has thousands of different kinds of macromolecules

• Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species

• An immense variety of polymers can be built from a small set of monomers

1 2 3 HOH


8. Concept 5.2: Carbohydrates serve as fuel and building material

• Carbohydrates include sugars and the polymers of sugars

• The simplest carbohydrates are monosaccharides, or single sugars

• Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks


9. Sugars

• Monosaccharides have molecular formulas that are usually multiples of CH2O

• Glucose is the most common monosaccharide

9. What is the formula of a hexose sugar?

CnH2nOn

LE 5-3Triose sugars

(C3H6O3)

GlyceraldehydeAld

ose

sK

eto

s es

Pentose sugars(C5H10O5)

Ribose

Hexose sugars(C5H12O6)

Glucose Galactose

Dihydroxyacetone

Ribulose

Fructose

10-12


• Monosaccharides serve as a major fuel for cells and as building blocks for other molecules

• Though often drawn as a linear skeleton, in aqueous solutions they form rings

13.

LE 5-4

Linear andring forms

Abbreviated ringstructure

13. Where are all the carbons in the abbreviated ring?


• A disaccharide =mono + mono

• What type of reaction bonds them together?

• This covalent bond is called a glycosidic linkage

Animation: Disaccharides

14.

LE 5-5

Glucose

Maltose

Fructose Sucrose

Glucose Glucose

Dehydrationreaction in thesynthesis of maltose

Dehydrationreaction in thesynthesis of sucrose

1–4glycosidic

linkage

1–2glycosidic

linkage

14.

15. What does –ose mean?


16. Glycosidic Linkage.

• A Glycosidic linkage is a covalent bond formed between two monosaccharides by a dehydration reaction.

• 1-4 glycosidic linkages


Polysaccharides

• Polysaccharides have storage and structural roles

• The structure and function is determined by its monomers and the positions of glycosidic linkages


18. Storage Polysaccharides

• Starch, a storage polysaccharide of plants, consists entirely of glucose monomers

• Plants store surplus starch as granules within chloroplasts and other plastids

LE 5-6aChloroplast Starch

1 µm

Amylose

Starch: a plant polysaccharide

Amylopectin


• Glycogen is a storage polysaccharide in animals

• Humans and other vertebrates store glycogen mainly in liver and muscle cells

LE 5-6bMitochondria Glycogen granules

0.5 µm

Glycogen

Glycogen: an animal polysaccharide


18. Structural Polysaccharides

• Cellulose is a major component of the tough wall of plant cells

• Like starch, cellulose is a polymer of glucose, but the glycosidic linkages differ

• The difference is based on two ring forms for glucose: alpha () and beta ()

Animation: Polysaccharides

LE 5-7

a Glucose

a and b glucose ring structures

b Glucose

Starch: 1–4 linkage of a glucose monomers.

Cellulose: 1–4 linkage of b glucose monomers.

LE 5-8

Cellulosemolecules

Cellulose microfibrilsin a plant cell wall

Cell walls Microfibril

Plant cells

0.5 µm

Glucosemonomer


• Enzymes that digest starch by hydrolyzing alpha linkages can’t hydrolyze beta linkages in cellulose

• Cellulose in human food passes through the digestive tract as insoluble fiber

• Some microbes use enzymes to digest cellulose

• Many herbivores, from cows to termites, have symbiotic relationships with these microbes

19.


• Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods

• Chitin also provides structural support for the cell walls of many fungi

• Chitin can be used as surgical thread


21. Concept 5.3: Lipids are a diverse group of hydrophobic molecules

• Lipids do not form polymers

• Lipids have little or no affinity for water

• Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds (remember?)

• The most biologically important lipids are fats, phospholipids, and steroids


22. Fats

• Fats = glycerol + 3 fatty acids

• Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon

• A fatty acid consists of a carboxyl group attached to a long carbon skeleton

Animation: FatsAnimation: Fats

LE 5-11a

Dehydration reaction in the synthesis of a fat

Glycerol

Fatty acid(palmitic acid)

23. How many water molecules are removed? What is this process called?


• Fats separate from water because water molecules form hydrogen bonds with each other and exclude the fats

• In a fat, three fatty acids are joined to glycerol by an ester linkage, a bond between a hydroxyl group and carboxyl group, creating a:

• Fat molecule = triacylglycerol = triglyceride

24

LE 5-11b

Ester linkage

Fat molecule (triacylglycerol)


• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds

• Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds

• Unsaturated fatty acids have one or more double bonds

• The major function of fats is energy storage

25.


• Fats made from saturated fatty acids are called saturated fats

• Most animal fats are saturated

• Saturated fats are solid at room temperature

• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits

26.

LE 5-12a

Saturated fat and fatty acid.

Stearic acid


• Fats made from unsaturated fatty acids are called unsaturated fats

• Plant fats and fish fats are usually unsaturated

• Plant fats and fish fats are liquid at room temperature and are called oils

28. The kinks in the fatty acid tail prevent unsaturated fats from packing together closely

enough to solidify at room temperature.

27.

LE 5-12b

Unsaturated fat and fatty acid.

Oleic acid

cis double bondcauses bending


29. Trans fats

• Hydrogenated oils – synthetically converted to saturated fat by adding hydrogen

– Prevents lipids from liquefying in peanut butter and margarine

• Trans fats – caused by hydrogenating process, has a trans double bond

– Contribute more that saturated fats to atherosclerosis


30. Four important functions of fats.


31. Phospholipids

• A phospholipid = glycerol + 2 fatty acids + a phosphate group

• The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head

LE 5-13

Structural formula Space-filling model Phospholipid symbol

Hydrophilichead

Hydrophobictails

Fatty acids

Choline

Phosphate

Glycerol

Hyd

rop

ho

bic

tai

lsH

ydr o

ph

ilic

hea

d


• When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior

– Tails are hydrophobic because of the non polar covalent bond of the hydrocarbons

• The structure of phospholipids results in a bilayer arrangement found in cell membranes

• Phospholipids are the major component of all cell membranes

32.

LE 5-14

WATERHydrophilichead

Hydrophobictails

WATER

34 - 35


36.


37. Steroids

• Steroids = a carbon skeleton consisting of four fused rings

• Cholesterol, an important steroid, is a component in animal cell membranes

• Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease


Concept 5.4: Proteins have many structures, resulting in a wide range of functions

• Proteins account for more than 50% of the dry mass of most cells

• Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances

• In other words, proteins are abundant and important!!!


38.

LE 5-16

Substrate(sucrose)

Enzyme(sucrose)

Fructose

Glucose

39


• Enzymes are protein catalysts

• That means they speed up chemical reactions

• Enzymes can perform their functions repeatedly, functioning as “workhorses” that carry out the processes of life

40. Is this reaction dehydration synthesis or hydrolysis?

39.


Polypeptides

• Polypeptides are polymers of amino acids

• A protein consists of one or more polypeptides

LE 5-UN78

Aminogroup

Carboxylgroup

carbon41.


42. Amino Acid Monomers

• Amino acids are organic molecules with carboxyl and amino groups

• Amino acids differ in their properties due to differing side chains, called R groups

• Cells use 20 amino acids to make thousands of proteins

LE 5-17a

Isoleucine (Ile)

Methionine (Met) Phenylalanine (Phe) Tryptophan (Trp) Proline (Pro)

Leucine (Leu)Valine (Val)Alanine (Ala)

Nonpolar

Glycine (Gly)

43.

LE 5-17b

Asparagine (Asn) Glutamine (Gln)Threonine (Thr)

Polar

Serine (Ser) Cysteine (Cys) Tyrosine (Tyr)

43.

LE 5-17c

Electricallycharged

Aspartic acid (Asp)

Acidic Basic

Glutamic acid (Glu) Lysine (Lys) Arginine (Arg) Histidine (His)

43.


44. Amino Acid Polymers

• Amino acids are linked by peptide bonds

• A polypeptide is a polymer of amino acids

• Polypeptides range in length from a few monomers to more than a thousand

• Each polypeptide has a unique linear sequence of amino acids called its primary structure


Protein Conformation and Function

• A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape

• The sequence of amino acids determines a protein’s three-dimensional conformation

• A protein’s conformation determines its function

• Ribbon models and space-filling models can depict a protein’s conformation

LE 5-19

A ribbon model

Groove

Groove

A space-filling model


45. Four Levels of Protein Structure

• The primary structure of a protein is its unique sequence of amino acids

• Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain

• Tertiary structure is determined by interactions among various side chains (R groups)

• Quaternary structure results when a protein consists of multiple polypeptide chains

Animation: Protein Structure IntroductionAnimation: Protein Structure Introduction

LE 5-20

Amino acidsubunits

pleated sheet+H3N

Amino end

helix

45-46


• Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word

• Primary structure is determined by inherited genetic information

Animation: Primary Protein StructureAnimation: Primary Protein Structure

LE 5-20a

Amino acidsubunits

Carboxyl end

Amino end


• The coils and folds of secondary structure result from hydrogen bonds between repeating parts of the polypeptide backbone

• The two types of secondary structure are:

– Alpha helix

– Beta pleated sheet

Animation: Secondary Protein StructureAnimation: Secondary Protein Structure

LE 5-20b

Amino acidsubunits

pleated sheet

helix


• Tertiary structure is determined by interactions between R groups, rather than interactions between backbone constituents

• These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions

• Strong covalent bonds called disulfide bridges may reinforce the protein’s conformation

Animation: Tertiary Protein StructureAnimation: Tertiary Protein Structure

LE 5-20d

Hydrophobicinteractions andvan der Waalsinteractions

Polypeptidebackbone

Disulfide bridge

Ionic bond

Hydrogenbond


• Quaternary structure results when two or more polypeptide chains form one macromolecule

• Example: Collagen is a fibrous protein consisting of three polypeptides coiled like a rope

• Example: Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains

Animation: Quaternary Protein StructureAnimation: Quaternary Protein Structure

LE 5-20e

Chains

ChainsHemoglobin

IronHeme

CollagenPolypeptide chain

Polypeptidechain


PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

LE 5-20d

Hydrophobicinteractions andvan der Waalsinteractions

Polypeptidebackbone

Disulfide bridge

Ionic bond

Hydrogenbond

47.


48. Sickle-Cell Disease: A Simple Change in Primary Structure

• A slight change in primary structure can affect a protein’s conformation and ability to function

• Example: Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

LE 5-21a

Red bloodcell shape

Normal cells arefull of individualhemoglobinmolecules, eachcarrying oxygen.

10 µm 10 µm

Red bloodcell shape

Fibers of abnormalhemoglobin deformcell into sickleshape.

LE 5-21b

Primarystructure

Secondaryand tertiarystructures

1 2 3

Normal hemoglobin

Val His Leu

4Thr

5Pro

6Glu Glu

7Primarystructure

Secondaryand tertiarystructures

1 2 3

Sickle-cell hemoglobin

Val His Leu

4Thr

5Pro

6Val Glu

7

Quaternarystructure

Normalhemoglobin(top view)

Function Molecules donot associatewith oneanother; eachcarries oxygen.

Quaternarystructure

Sickle-cellhemoglobin

Function Molecules interact withone another tocrystallize intoa fiber; capacityto carry oxygenis greatly reduced.

Exposedhydrophobicregion subunit subunit


49. What Determines Protein Conformation?

• In addition to primary structure, physical and chemical conditions can affect conformation

• Changes in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel

• This loss of a protein’s native conformation is called denaturation

• A denatured protein is biologically inactive

LE 5-22

Denaturation

Renaturation

Denatured proteinNormal protein


50. The Protein-Folding Problem

• It is hard to predict a protein’s conformation from its primary structure

• Most proteins probably go through several states on their way to a stable conformation

• Chaperonins are protein molecules that assist the proper folding of other proteins

LE 5-23a

Chaperonin(fully assembled)

Hollowcylinder

Cap

LE 5-23b

Polypeptide

Correctlyfoldedprotein

An unfolded poly-peptide enters thecylinder from oneend.

Steps of ChaperoninAction:

The cap comesoff, and theproperly foldedprotein is released.

The cap attaches, causingthe cylinder to changeshape in such a way that it creates a hydrophilicenvironment for thefolding of the polypeptide.


Pre Quiz

• Turn to page 11 question 51

• Try to answer this questions with your background knowledge from Biology and your reading guide


Concept 5.5: Nucleic acids store and transmit hereditary information

• The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene

• Genes are made of DNA, a nucleic acid• There are two types of nucleic acids:

– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)

• DNA provides directions for its own replication

• DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis

• Protein synthesis occurs in ribosomes

LE 5-25

NUCLEUS

DNA

CYTOPLASM

mRNA

mRNA

Ribosome

Aminoacids

Synthesis ofmRNA in the nucleus

Movement ofmRNA into cytoplasmvia nuclear pore

Synthesis of protein

Polypeptide

51.


The Structure of Nucleic Acids

• Nucleic acids are polymers called polynucleotides

• Each polynucleotide is made of monomers called nucleotides

• Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group

LE 5-26a5 end

3 end

Nucleoside

Nitrogenousbase

Phosphategroup

Nucleotide

Polynucleotide, ornucleic acid

Pentosesugar

52-53.

LE 5-26bNitrogenous bases

Pyrimidines

Purines

Pentose sugars

CytosineC

Thymine (in DNA)T

Uracil (in RNA)U

AdenineA

GuanineG

Deoxyribose (in DNA)

Nucleoside components

Ribose (in RNA)

54.


56. Nucleotide Monomers

• There are two families of nitrogenous bases:

– Pyrimidines have a single ring structure (cytosine and thymine and uracil)

– Purines have a double ring structure (adenine and guanine)

• In DNA, the sugar is deoxyribose

• In RNA, the sugar is ribose


Nucleotide Polymers

• Nucleotides are joined by covalent bonds that form between the –OH group on the 3´ carbon of one nucleotide and the phosphate on the 5´ carbon on the next

• These links create a “sugar-phosphate backbone”

• The sequence of bases along a DNA or mRNA polymer is unique for each gene


58-59. The DNA Double Helix

• A DNA molecule has two polynucleotides spiraling around an imaginary axis, forming a double helix

• In the DNA double helix, the two backbones run in opposite 5´ to 3´ directions from each other, an arrangement referred to as antiparallel

• One DNA molecule includes many genes

• The nitrogenous bases in DNA form hydrogen bonds in a complementary fashion: A always with T, and G always with C

LE 5-27

Sugar-phosphatebackbone

3 end5 end

Base pair (joined byhydrogen bonding)

Old strands

Nucleotideabout to beadded to anew strand

5 end

New strands

3 end

5 end3 end

5 end

60.-63.

copyright © 2005 pearson education, inc. publishing as benjamin cummings pre quiz – share a sheet...

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