THE STRUCTURE & FUNCTION OF

LARGE BIOLOGICAL MACROMOLECULESCampbell and Reece CHAPTER 5

Macromolecules are Polymers polymer: long molecule consisting

of many similar, sometimes identical, building blocks linked by covalent bonds

monomer: the smaller units that make up a polymer

Many Monomers Make a Polymer

Making Polymers 2 monomers joined by dehydration

reaction

Disassembling Polymers hydrolysis reaction breaks apart 2

monomers in a polymer

Diversity of Polymers possible varieties of

macromolecules infinite only use 40 -50 monomers small molecules common to all

organisms are ordered into species unique macromolecules

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Carbohydrates Simple Carbohydrates

Sugars Monosaccharides Disaccharides

Complex Carbohydrates Polysaccharides

Monosaccharides multiples of the unit CH2O glucose most common

monosaccharide

Monosaccharide Diversity depending on position of the carbonyl

group in a sugar it is classified as either:

1. aldose (aldehyde sugar)2. ketose (ketone sugar)

Monosaccharide Diversity 3 to 7 carbons hexose: 6 carbons long pentose: 5 carbons triose: 3 carbons

Monosaccharide Diversity most hexoses and pentoses form

rings in aqueous solutions used in cellular respiration

(especially glucose) serve as raw materials for synthesis

of amino acids and fatty acids

if not immediately used in these ways used to build disaccharides or polysaccharides

Forms of Glucose

Alpha Glucose Beta Glucose

Disaccharides reaction: 2 monosaccharides joined

in a glycosidic linkage covalent bond formed by dehydration

reaction

Disaccharides 2 glucose = maltose (malt sugar) glucose + galactose glucose + fructose = sucrose (table

sugar)

sucrose: form plants use to transport sugars from leaves roots & other nonphotosynthetic parts of plant

Polysaccharides polymers of hundreds to thousands

of monosaccharides joined by glycosidic linkages

function determined by its sugar monomers & positions of glycosidic linkages

2 types:1. storage of monosaccharides to be

used for energy when needed2. building material

Storage Polysaccharides Plants store glucose (the

monomers)as starch (the polymer) represents stored energy

Starch most is made of α glucose

monomers joined in 1-4 linkages simplest form of starch (amylose) is

unbranched complex starch, amylopectin, has 1-

6 linkage

Storage Polysaccharides Animals: store glucose (the

monomers) as glycogen (the polymer) in 1-4 & 1-6 linkages stored mainly in liver & muscle cells humans store about 1 days supply of

glucose this way

Structural Polysaccharides Cellulose: most abundant organic

cpd on Earth is polymer of β glucose (makes

every monomer of glucose “upside down” from its neighbors)

Starch & Cellulose

many are mostly helical

digested by enzymes breaking its α linkages

never branched has –OH groups

available for H-bonds

digested by enzymes breaking its β linkages

Starch Cellulose

Cellulose digested by very few organisms

(don’t have enzymes to do it) in humans: passes thru GI tract

abrading walls & stimulating mucus secretion along the way smoother passage of food thru

not technically a nutrient but is important

“Insoluble Fiber” = Cellulose

Cellulose Cows: have bacteria and protists in

their guts that have enzymes that can digest cellulose nutrients that can be used by cow

Termites unable to digest cellulose in wood it eats have prokaryotes & protists to break it down and so termite can use nutrients

Termite Life Cycle

Termites

Chitin another structural polysaccharide used by arthropods to build

exoskeletons exoskeletons: made of chitin +

calcium carbonate

Chitin also in many fungi cell walls monomer has N group attached

Lipids large group of hydrophobic

molecules do not have true monomers Includes:

Waxes Steroids Some Pigments Oils, Fats Phospholipids

Fats large molecules assembled from

smaller molecules by a dehydration reaction

2 parts:1. Glycerol2. Fatty Acid

Glycerol

Fatty Acids long (16-18) chain of carbons

(hydrophobic) @ one end carboxyl group (hence

fatty acid)

Triglyceride 3 fatty acids + glycerol

Saturated & Unsaturated

Saturated Fats include most animal fats most are solids @ room

temperatures

Unsaturated Fats fats of plants, fish usually liquid @ room temperature

Hydrogenated Vegetable Oil seen on some food labels means that unsaturated fats have

been synthetically converted to saturated fats to keep from separating

Plaques deposits of saturated & trans fats

(hydrogenated vegetable oils with trans double bonds) in muscularis of arteries

Plaques lead to atherosclerosis (leading cause

of heart attacks) by decreasing resilience of vessel & impeding blood flow

Trans Fats USDA now requires nutritional

labels to include amount of trans fats

some cities & Denmark ban restaurants from using trans fats

Essential Fatty Acids cannot be synthesized in body so

must be included in diet include: omega-3 fatty acids:

required for normal growth in children

probably protect against cardiovascular disease in adults

Omega-3 Fatty Acids

Energy Storage 1 g fat has 2x chemical potential

energy as 1 g of polysaccharide plants (generally immobile) can

store majority of their energy in polysaccharides except vegetable oils extracted from their seeds

Functions of Fat Plants: storage of energy Animals: 1. storage of energy2. protect organs3. insulation

Phospholipids essential component of cell

membranes

Phospholipids when added to water self-assemble

into lipid bilayers

Steroids lipids characterized by a carbon

skeleton made of 4 fused rings cholesterol & sex hormones have

functional groups attached to these fused rings

Cholesterol in Animals part of cell membranes precursor for other steroids vertebrates make it in liver +

dietary intake saturated fats & trans fats increase

cholesterol levels which is ass’c with atherosclerotic disease

In plant seeds, the inside of the seed is rich in lipids (oils). Describe & explain the form the membrane around a droplet of oil would need to take:

Proteins word in Greek from “primary” account for >50% of dry mass of

most cells instrumental in almost everything

organisms do

Proteins are Worker Molecules

Proteins humans have tens of thousands of

proteins, each with specific structure & function

all made from 20 amino acids (a.a.)

Proteins are biologically functional molecules made of 1 or more polypeptides, each folded & coiled into a specific 3-D structure

Amino Acid Monomers all a.a. share common structure:

Amino Acid Structure alpha carbon: center asymmetric

carbon its 4 covalent bonds are with:

1. amino group2. carboxyl group3. H atom4. R = variable group= side chain

Amino Acids http://www.johnkyrk.com/aminoacid.html

20 Amino Acids

R Groups its physical & chemical properties

determine the unique characteristics of a.a. so affect the physical & chemical properties of the polypeptide chain

Peptide Bonds

Polypeptide Backbone polypeptide chain

will have 1 amino end (N-terminus) and 1 carboxyl end (C-terminus)

R side chains far outnumber N & C terminus so produce the chemical nature of the molecule

Protein Structure & Function

polypeptide ≠ protein

Functional Protein is not just a polypeptide chain but 1

or more polypeptides precisely twisted, folded, & coiled into a uniquely shaped molecule

Protein Shape determined by a.a. sequence

Protein Shape1. Globular

Protein roughly

spherical2. Fibrous

Protein long fibers

when polypeptide released from ribosome it will automatically assume the functional shape for that protein’s (due to its primary structure)

Name that Shape

Protein Structure determines how it functions almost all proteins work by

recognizing & binding to some other molecule

1st Level of Protein Structure

Secondary Structure segments of each polypeptide chain

that coil or fold in patterns result of:

H-bonds in polypeptide backbone α helix: every 4th a.a. held together by

H-bonds β pleated: 2 parallel β strands held

together by H-bonds (is what makes spider silk so strong)

Secondary Structure

Tertiary Structure 3-D shape stabilized by interactions

between side-chains1. hydrophobic interactions

a.a. with nonpolar side chains usually end up together at core of protein: result of exclusion of nonpolar parts by water

once nonpolar side chains away from water, van der Waals forces hold them together

Tertiary Structure: Hydrophobic Interactions

Tertiary Structure2. Disulfide Bridges covalent bonds that form between 2

S in side chains of different a.a.

Quarternary Structure for proteins that are made of >1

polypeptide chain the overall protein structure that

results from aggregation of all polypeptide subunits in protein

http://www.learner.org/courses/biology/archive/animations/hires/a_proteo1_h.html

Protein Structure

http://www.stolaf.edu/people/giannini/flashanimat/proteins/protein%20structure.swf

Collagen fibrous protein:

40% of all protein in human body

3 identical polypeptides “braided” into triple helix

gives collagen its great strength

Hemoglobin globular protein

made of 2 alpha & 2 beta subunits (polypeptides)

each has nonpolypeptide part = heme which has Fe to bind O2

Sickle Cell Disease due to substitution of one a.a.

(valine) for the normal one, glutamine

causes normal disc-shape of RBC to become sickle shaped because the abnormal hemoglobin crystallizes

Sickle Cell Disease go thru periodic “sickle-cell crises” angular sickled cells clog small

blood vessels impedes blood flow causes pain

Protein Structure also depends on physical & chemical

environment protein is in:1. pH2. salt concentration3. temperature

all of the above can change weak bonds & forces holding protein together

Denaturation process in which a protein loses its

native shape due to the disruption of weak chemical bonds & interactions

denatured protein becomes biologically inactive

Denaturation Agents taking protein out of water

nonpolar solvent: hydrophilic a.a that were on outer edge to core vise versa with hydrophobic a.a.

Protein Structure most proteins probably go thru

some intermediate shape stages b/4 achieving their stable shape

chaperonins: protein molecules that assist in the proper folding of other proteins

Chaperonins

Misfolded Proteins ass‘c with:

Alzheimer’s Mad Cow disease Parkinson’s Senile Dementia

X-ray Crystallography used to determine the 3-D shape of

proteins

Nuclear Magnetic Resonance (NMR) Spectroscopy

does not require crystallization of protein

Bioinformatics uses computers to store, organize,

& analyze data to predict 3-D structure of polypeptides from a.a. sequences

NUCLEIC ACIDS are polymers made of monomers

called nucleotides genes code for a.a. sequences in

proteins

1. DNA deoxyribonucleic acid1. RNA ribonucleic acid

Nucleic Acid RolesDNA:1. self-replication2. reproduction of organism3. flow of genetic information: DNA

RNA synthesis protein synthesis

Nucleic Acid RolesRNA:1. mRNA

conveys genetic instructions for building proteins from DNA ribosomes

in eukaryotic cells means from nucleus cytoplasm

prokaryotic cells also use mRNA

Nucleic Acids polymers of nucleotides (the

monomers)

Nucleoside portion of a nucleotide w/out any

phosphate group(s)

Nitrogenous Bases each has 1 or 2 rings that include N are bases because the N atoms can

take up H+ 2 families:1. Pyrimidines

(1) 6-sided ring made of C & N2. Purines

(1) 6-sided ring fused to a 5-sided ring

Pyrimidines 1. Cytosine

2. Thymine

3. Uracil

Purines1. Adenine

2. Guanine

Sugars in Nucleic Acidsadded to

1. Deoxyribose

2. Ribose

Phosphate Group added to 5’ C of the sugar (base was added to 1’ C)

Nucleotide Polymers 1 nucleotide added to next in

phosphodiester linkages

Nucleic Acid Backbone Phosphodiester

linkages repeating pattern of phosphate – sugar – phosphate – sugar..

notice: phosphate end

is 5’ sugar end is 3’

Polynucleotides have built-in direction along their sugar-phosphate backbones

DNA bases held together by H-bonds with backbones going in opposite directions

Linear Order of Bases specifies start, stop of

transcription/translation and codons determine primary structure of proteins (which determines the 3-D structure of a protein which in turn determines the function of the protein)

DNA Molecules dbl stranded (in opposite directions

= antiparallel) bases held together by H-Bonds most have thousands – millions base

pairs bases pair using complementary

base rules

Complimentary Bases

DNA Molecules

RNA complementary base pairing occurs

between:1. 2 strands of RNA2. 2 stretches of same RNA strand

Uracil pairs with Adenine instead of Thymine (none in RNA)

DNA & Proteins genes & their proteins document

the hereditary background of an organism

able to expect 2 species that appear to be closely related based on fossil & anatomical evidence to also share a greater proportion of their DNA & protein sequences than do more distantly related species

Hemoglobin human & gorilla hgb differ only by 1

a.a out of 46 in β chain human & frog differ by 67 a.a.