structure & function of large biological molecules (macromolecules)
TRANSCRIPT
STRUCTURE & FUNCTION OF LARGE BIOLOGICAL
MOLECULES
(MACROMOLECULES)
Concept 2.1: Macromolecules are polymers, built from monomers
– Carbohydrates amino acids
– Proteins monosaccharides
– Nucleic acids lipids
– Do not form polymers nucleotides
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1. Match the polymer to its monomer
2. Number the carbons properly
3. To link these 2 monosaccharides together, what do you do?
4. What is the process called that will link the 2 together to make a disaccharide?
5. What is this sugar called?
6. Suppose 2 more monosaccharides link to the diagram below, what would the carbohydrate be called?
7. How many total water molecules would need to be removed to have 4 monosaccharides linked together?
8.Between which two carbons does this process always occur when covalently bonding monosaccharides together? Use the carbon numbering system to figure this out.
Concept 5.1: Macromolecules are polymers, built from monomers
• A polymer is a long molecule consisting of many similar building blocks
• These small building-block molecules are called monomers
• Three of the four classes of life’s organic molecules are polymers:
– Carbohydrates
– Proteins
– Nucleic acidsCopyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 2.2: Carbohydrates serve as fuel and building material
• Carbohydrates include sugars and the polymers of sugars
• The simplest carbohydrates are monosaccharides, or single sugars. They provide ready energy for the body.
• Carbohydrate macromolecules are polysaccharides, polymers composed of many sugar building blocks
• Polysacchrides – fuel that “burns” more slowly. More bonds for the body to break (hydrolysis).
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Sugars
• Monosaccharides have molecular formulas that are usually multiples of CH2O
• Glucose (C6H12O6) is the most common monosaccharide
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Fig. 5-4b
(b) Abbreviated ring structure
• A disaccharide is formed when a dehydration synthesis joins two monosaccharides
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Fig. 5-5
(b) Dehydration reaction in the synthesis of sucrose
Glucose Fructose Sucrose
MaltoseGlucoseGlucose
(a) Dehydration reaction in the synthesis of maltose
1–2glycosidic
linkage
Dehydration synthesis: remove water make a bond
Polysaccharides
• Polysaccharides, the polymers of sugars, have storage and structural roles
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Storage Polysaccharides
• Starch, a storage polysaccharide of plants, consists entirely of glucose monomers
• Plants store surplus starch as granules within chloroplasts and other plastids
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Fig. 5-6
(b) Glycogen: an animal polysaccharide
Starch
GlycogenAmylose
Chloroplast
(a) Starch: a plant polysaccharide
Amylopectin
Mitochondria Glycogen granules
0.5 µm
1 µm
• Glycogen is a storage polysaccharide in animals
• Humans and other vertebrates store glycogen mainly in liver and muscle cells
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Structural Polysaccharides
• The polysaccharide cellulose is a major component of the tough wall of plant cells
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Fig. 5-7a
Glucose
Glucose: a monosaccharide. It’s only 1 ring!
Fig. 5-7bc
(a) Starch: a linkage of glucose molecules
(b) Cellulose: same thing but a little different!! Doesn’t seem like much: but it makes Cellulose less digestible than .
Fig. 5-8
b Glucosemonomer
Cellulosemolecules
Microfibril
Cellulosemicrofibrilsin a plantcell wall
0.5 µm
10 µm
Cell walls
The reasonyou can’t graze on the front lawn of the school like a cow during lunch!!
• Enzymes that digest starch (amylase) can’t break bonds 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
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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
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Fig. 5-10
The structureof the chitinmonomer.
(a) (b) (c)Chitin forms theexoskeleton ofarthropods.
Chitin is used to makea strong and flexiblesurgical thread.
Hey look, chitin’s got some nitrogenOther carbs don’t have that.
Concept 5.3: Lipids are a diverse group of hydrophobic molecules
• Lipids are the one class of large biological molecules that do not form polymers
• Lipids are hydrophobic & form nonpolar covalent bonds
• The most biologically important lipids are fats, phospholipids, and steroids, waxes & oils
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Fats
• Fats are constructed from two types of smaller molecules: glycerol and 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
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Fig. 5-11a
Fatty acid(palmitic acid)
(a) Dehydration reaction in the synthesis of a fat
Glycerol
Fig. 5-11b
(b) Fat molecule
• Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds
• Unsaturated fatty acids have one or more double bonds
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Fig. 5-12a
(a) Saturated fat
Structuralformula of asaturated fatmolecule
Stearic acid, asaturated fattyacid
Fig. 5-12b
(b) Unsaturated fat
Structural formulaof an unsaturatedfat molecule
Oleic acid, anunsaturatedfatty acid
doublebond causesbending
• Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature
• Most animal fats are saturated
• Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature
• Plant fats and fish fats are usually unsaturated
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• 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 (This is bad for you!!)
• Trans fats may contribute more than saturated fats to cardiovascular disease
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• The major function of fats is energy storage
• Humans and other mammals store their fat in adipose cells
• Adipose tissue also cushions vital organs and insulates the body
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Phospholipids
• In a phospholipid, two fatty acids and a phosphate group are attached to glycerol
• The two fatty acid tails are hydrophobic, but the phosphate group and its attachments form a hydrophilic head
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Fig. 5-13
(b)(a) (c)Structural formula Phospholipid symbol
Fatty acids
Hydrophilichead
Hydrophobictails
Phosphate
Hyd
rop
ho
bic
tai
lsH
ydro
ph
ilic
hea
d
Let’s use Diagram C. It’s easy to Understand!
• When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior
• Phospholipids are the major component of all cell membranes
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Fig. 5-14
Hydrophilichead
Hydrophobictail WATER
WATER
Steroids
• Steroids are lipids characterized by 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
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Fig. 5-15
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
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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, functioning as workhorses that carry out the processes of life
• Enzymes have specific shapes
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Fig. 5-16
Enzyme(sucrase)
Substrate(sucrose)
Fructose
Glucose
OH
HO
H2O
Polypeptides
• Polypeptides are polymers built from the same set of 20 amino acids
• A protein consists of one or more polypeptides
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Amino Acid Monomers
• Amino acids are organic molecules with carboxyl (-COOH) and amino groups (NH2)
• COOH and NH2 are functional groups and make the molecule an amino acid.
• Amino acids differ in their properties due to differing side chains, called R groups
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Fig. 5-UN1
Aminogroup
Carboxylgroup
carbon
Fig. 5-17Nonpolar
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)
Don’t getworked upabout these. Appreciate them!! Theseare aminoacids. Thereare 20. Theybond togetherby peptidebonds to makeup all proteins!
Amino Acid Polymers
• Amino acids are linked by special covalent bonds called peptide bonds
• A polypeptide is a polymer of amino acids
• Each polypeptide has a unique linear sequence of amino acids
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Peptidebond
Fig. 5-18
Peptidebond
(a)
(b)
Protein Structure and Function
• A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape
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Fig. 5-19
A ribbon model of lysozyme(a) (b) A space-filling model of lysozyme
GrooveGroove
• The sequence of amino acids determines a protein’s three-dimensional structure
• A protein’s structure determines its function
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What Determines Protein Structure?Remember these things about liver lab
• 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 native structure is called denaturation
• A denatured protein is biologically inactive
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Fig. 5-23
Normal protein Denatured protein
Denaturation
Renaturation
Concept 5.5: Nucleic acids store and transmit hereditary information
• The amino acid sequence of a polypeptide (protein) is determined by chemical information found on segments of DNA (aka: genes)
• Genes are made of DNA, a nucleic acid
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The Roles of Nucleic Acids
• There are two types of nucleic acids:
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
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The Structure of Nucleic Acids
• Each polynucleotide is made of monomers called nucleotides
• Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group
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Fig. 5-27ab5' end
5'C
3'C
5'C
3'C
3' end
(a) Polynucleotide, or nucleic acid
(b) Nucleotide
Nucleoside
Nitrogenousbase
3'C
5'C
Phosphategroup Sugar
(pentose)
Fig. 5-27c-1
(c) Nucleoside components: nitrogenous bases
Purines
Guanine (G)Adenine (A)
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Nitrogenous bases
Pyrimidines
Fig. 5-27c-2
Ribose (in RNA)Deoxyribose (in DNA)
Sugars
(c) Nucleoside components: sugars
Fig. 5-UN5
Fig. 5-UN6