STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES (MACROMOLECULES)

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

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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).


Sugars

• Monosaccharides have molecular formulas that are usually multiples of CH2O

• Glucose (C6H12O6) is the most common monosaccharide


Fig. 5-4b

(b) Abbreviated ring structure

• A disaccharide is formed when a dehydration synthesis joins two monosaccharides


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


Storage Polysaccharides

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

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


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


Structural Polysaccharides

• The polysaccharide cellulose is a major component of the tough wall of plant cells


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


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


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


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


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


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


• 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


• 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


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


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


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


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


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


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


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


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


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


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


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


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


The Roles of Nucleic Acids

• There are two types of nucleic acids:

– Deoxyribonucleic acid (DNA)

– Ribonucleic acid (RNA)


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


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

STRUCTURE & FUNCTION OF LARGE BIOLOGICAL MOLECULES (MACROMOLECULES)

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