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Chapter 5: Macromolecules
Macromolecules
• A large molecule in a living organism– Proteins, Carbohydrates, Nucleic Acids
• Polymer- long molecules built by linking repeating building blocks in a chain
• Monomer- units that serve as building blocks of polymer
Dehydration Synthesis- How cells link together monomers- Monomers have H atoms and hydroxyl groups- Add a monomer to a chain, a water molecule is released
Hydrolysis
- Opposite of dehydration synthesis- Bond in a polymer are broken by addition of water
1. Carbohydrates
Carbohydrates: include sugars and polymers of sugar
Monosaccharides: the simplest carbohydrate, made of a single sugar
Monosaccharides • The simplest carbohydrate made of a
single sugar
• Have molecular formulas multiple of CH20 (Most common sugar is glucose C6H1206)
• Have a hydroxyl group (OH) and a carbonyl group (C=0)
• OH group make it an alcohol and the C=0 make it an aldehyde or ketone
Fig. 5-3
Dihydroxyacetone
Ribulose
Ket
ose
sA
ldo
ses
Fructose
Glyceraldehyde
Ribose
Glucose Galactose
Hexoses (C6H12O6)Pentoses (C5H10O5)Trioses (C3H6O3)
• Though often drawn as linear skeletons, in aqueous solutions many sugars form rings
• Monosaccharides serve as a major fuel for cells (glucose)
• Most sugars end in -oseMonosaccharides (cont’d)
Disaccharide • A double sugar created when dehydration
synthesis joins
Ex: 2 glucose -> maltose (malt sugar makes beer)
• Glycosidic linkage: covalent bond between 2 sugars of a disaccharide
(b) Dehydration reaction in the synthesis of sucrose
Glucose Fructose Sucrose
MaltoseGlucoseGlucose
(a) Dehydration reaction in the synthesis of maltose
1–4glycosidic
linkage
1–2glycosidic
linkage
• Many act as storage molecules of sugar, that cells break down for energy
• Hundreds or thousands of monosaccharides joined together (glycosidic links)
Polysaccharide
Polysaccharide- Starch • Made of all glucose and found in plants
• Plants store starch and break into glucose when needed for energy
• Humans and animals hydrolyze starch when they eat it (found in wheat, corn, rice, potatoes)
• Glycogen is hydrolyzed to release glucose when needed
• Excess sugar in animals is stored as glycogen in liver and muscles
Polysaccharide- Glycogen
• A component of a plant’s cell wall, gives them structure
Polysaccharide- Cellulose
• Cellulose molecules connected by hydrogen bonds and form fiber
Fig. 5-9
• Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods
• Chitin also provides structural support for the cell walls of many fungi
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-10
The structureof the chitinmonomer.
(a) (b) (c)Chitin forms theexoskeleton ofarthropods.
Chitin is used to makea strong and flexiblesurgical thread.
What does this say about their solubility?
• Compounds that consist mainly of C and H atoms linked by nonpolar covalent bonds
Lipid
• Ex: fats, oils, cholesterol, waxes
- a 3 carbon alcohol with hydroxyl group
• A large lipid made of glycerol and fatty acids
Fats
• Ex: fats, oils, waxes• 1 fat molecule = 1 glycerol and 3 fatty acids
• Function is energy storage (1 g of fat stores more than 2x as much energy as 1 g of starch)
Fig. 5-11
Fatty acid(palmitic acid)
Glycerol
(a) Dehydration reaction in the synthesis of a fat
Ester linkage
(b) Fat molecule (triacylglycerol)
• No double bond in fatty acid• Solids (lard, butter- animal fats)• Leads to heart disease, plaque in blood vessels
Saturated Fats
• the fatty acid contains double bonds, preventing the skeleton from having the max # of hydrogen’s.
• Molecules can’t pack together tightly and form liquids at room temp (oils and plant fats)
Unsaturated Fats
The Curious Case of Olestra
• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits
• Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen
• Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds
• These trans fats may contribute more than saturated fats to cardiovascular disease
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
• Major component of cell membranes• Similar to fat, but contain phosphorus and have 2 fatty acid (not 3)
Phospholipids
Cholesterol
• Stabilizes cell membrane
• Helps resist temperature changes
• 1 fatty acid and an alcohol• More hydrophobic than fats• Natural coating on fruit• Insects have to keep from drying out
Waxes
• lipids whose carbon skeleton is bent to form 4 fused rings
• all steroids have 3-6 sided rings and 1-5 sided ring
• Ex: cholesterol found in animal cell membranes and animal cells use it to make other steroids (estrogen and testosterone)
Steroids
Fig. 5-15
Chapter 5: Macromolecules
http://www.youtube.com/watch?v=lijQ3a8yUYQ
Proteins
• 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
Table 5-1
• Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions
• Enzymes can perform their functions repeatedly being reused
Enzymes
Fig. 5-16
Enzyme(sucrase)
Substrate(sucrose)
Fructose
Glucose
OH
HO
H2O
Amino Acid Monomers
• Amino acids (monomers) build proteins (polymers)• Amino acids are organic molecules with carboxyl and amino groups• Amino acids differ in their properties due to differing side chains,
called R groups• THE R GROUP is the variable part of the amino acid and determines
physical and chemical properties
Fig. 5-UN1
Aminogroup
Carboxylgroup
carbon
Nonpolar
Glycine(Gly or G)
Alanine(Ala or A)
Valine(Val or V)
Leucine(Leu or L)
Isoleucine(Ile or )
Methionine(Met or M)
Phenylalanine(Phe or F)
Trypotphan(Trp or W)
Proline(Pro or P)
Polar
Serine(Ser or S)
Threonine(Thr or T)
Cysteine(Cys or C)
Tyrosine(Tyr or Y)
Asparagine(Asn or N)
Glutamine(Gln or Q)
Electricallycharged
Acidic Basic
Aspartic acid(Asp or D)
Glutamic acid(Glu or E)
Lysine(Lys or K)
Arginine(Arg or R)
Histidine(His or H)
Fig. 5-17c
Acidic
Arginine (Arg or R)
Histidine (His or H)
Aspartic acid (Asp or D)
Glutamic acid (Glu or E)
Lysine (Lys or K)
Basic
Electricallycharged
Amino Acid Polymers
• Amino acids are linked by peptide bonds between carbonyl and amino group
• A polypeptide is a polymer of amino acids
• Polypeptides range in length from a few to more than a thousand monomers
• Each polypeptide has a unique linear sequence of amino acids
Peptidebond
Fig. 5-18
Amino end(N-terminus)
Peptidebond
Side chains
Backbone
Carboxyl end(C-terminus)
(a)
(b)
Polypeptides
• Polypeptides are polymers built from the same set of 20 amino acids
• A protein consists of one or more polypeptides
Protein Structure 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 structure
• A protein’s structure determines its function
• 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
Primary Structure
• The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone (amino and carbonyl group
• Typical secondary structures are a coil called an alpha helix and a folded structure called a pleated sheet
Secondary Structure
• 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 structure
Tertiary Structure
Fig. 5-21e
Tertiary Structure Quaternary Structure
Fig. 5-21f
Polypeptidebackbone
Hydrophobicinteractions andvan der Waalsinteractions
Disulfide bridge
Ionic bond
Hydrogenbond
• Quaternary structure results when two or more polypeptide chains form one macromolecule
• Forms a “globular protein”
Quaternary Structure
Fig. 5-21g
Polypeptidechain
Chains
HemeIron
Chains
CollagenHemoglobin
Sickle-Cell Disease: A Change in
Primary Structure
• A slight change in primary structure can affect a protein’s structure and ability to function
• Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin
What Determines Protein Structure?
• In addition to primary structure, physical and chemical conditions can affect structure
• Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel
• This loss of a protein’s structure is called denaturation
• A denatured protein is biologically inactive
Fig. 5-23
Normal protein Denatured protein
Denaturation
Renaturation
The Roles of Nucleic Acids
• 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
Fig. 5-26-3
mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
Ribosome
AminoacidsPolypeptide
Synthesisof protein
1
2
3
The Structure of Nucleic Acids
• Nucleotides are monomers of DNA/RNA
• Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
Nucleotide Polymers
• Adjacent nucleotides are joined by covalent bonds
• These links create a backbone of sugar-phosphate units