LARGE BIOLOGICAL MOLECULESChapter 5

FUEL FOR LIVING SYSTEMS Large molecules are important for the basic

processes of life Grouped into 4 classes of organic compounds

Carbohydrates* Lipids Proteins* Nucleic acids*

Important to know how these are made, stored, and destroyed

Also, structure and function

* are considered macromolecules

POLYMERS

Chain of similar repeating units linked by covalent bonds E.g CAT-CAT-CAT-CAT=CAT-CAT or the alphabet Carbs, proteins, and nucleic acids are examples

The similar repeating units are called monomers E.g CAT or any letter of alphabet Joined and broken by reversible reactions

Enzymes can speed the reaction E.g digestion: cells need organic molecules broken

down so can be absorbed after which they can be rebuilt

POLYMERS

Dehydration reaction Links monomers Loss of water for each

monomer added Forms a covalent bond

Hydrolysis reaction Breaks polymers Addition of water for

each broken bond

Making polymers Breaking polymers

1 42

21

3

3 4

1

2

2 3

3

4

41

EXAMPLES OF POLYMERS

Small molecules are ordered to dictate life DNA is a polymer composed of 4 monomers

(nucleiotides) Creates variation based on arrangement

Proteins are polymers from 20 different amino acids (AA’s)

Sequence variation separates humans from flowers and individuals from individuals

CARBOHYDRATES

Simple sugars and polymers of simple sugars Sugars are broken down based on the number of

polymers Monosaccharides Disaccharides Polysaccharides

Each is joined by a dehydration reaction Polymers of sugar are actually what is

generally considered a carbohydrate or starchy food

MONOSACCHARIDES

Glucose is most common Major nutrient for cells Respiration, fuel for cellular work, and raw

material Trademarks of sugars

Molecular repeating unit of CH2O- Carbonyl and hydroxyl functional groups 3-7 carbons long

Hexoses (6 carbons, e.g glucose and fructose) Pentoses (5 carbons, e.g ribose and dioxyribose)

End in “-ose”

GLUCOSE VS FRUCTOSE

Also are examples of what?

DISACCHARIDES 2 monosaccharides

joined by a covalent bond Result of dehydration

reaction Form a glycosidic

bond/linkage Maltose

glucose + glucose Whoppers, malts, beer

Sucrose Glucose + fructose Table sugar Plant sap

Lactose galactose + glucose

POLYSACCHARIDES

Multiple glycosidic linkages Storage material until needed

Hydrolysis will break apart to provide sugars to cells

Building materials for cell protections 4 types

Starch Glycogen Cellulose Chitin

POLYSACCHARIDES FOR STORAGE

Starch Polymer of many glucose monomers Plants use as storage

Form of plastids Stockpiled glucose = stored E

E.g potatoes, grains, wheat, and corn Glycogen

More branched polymer of glucose Vertebrate storage in liver and muscles

Hydrolyzed when sugar is needed Not good for long term because depleted quickly

CELLULOSE

Cell wall of plant cells Most abundant organic compound on Earth Polymer of glucose with different linkages Straight molecule, grouped to form microfibrils

= strong Major component of paper and only of cotton

Most animals can’t hydrolyze Undigested, stimulates GI tract through abrasion

to stimulate mucous secretion Most fresh fruits, vegetables, and whole grains

Insoluble fiber on packages

CHITIN Composes arthropod exoskeletons

CaCO3 covers body and hardens Molted off and commonly eaten as Ca2+ source

Cell walls in fungi Used for surgical thread

Dissolvable stitches

LIPIDS ‘Grab bag’ of molecules

Not true polymers Not really big enough to

be macromolecules All mix poorly with

water due to hydrophobic nature (hydrocarbon chains)

Form ester linkages 3 types

Fats Phospholipids Steroids

FATS Glycerol (alcohol w/ 3 carbons) and fatty acids (16-

18 carbons and carboxyl end) Hydroxyl and carboxyl linkage = ester linkage

(triglyceride) Can be saturated or unsaturated Hydrogenated vegetable oils

Unsaturated synthetically to saturated by adding hydrogens Peanut butter and margarine to prevent separation Trans fats when conversion changes conformation of double

bond

Necessary for energy storage (hydrogen bonds) More compact, better for mobility Adipose storage

Cushions vital organs and insulates

SA

TU

RA

TED

VER

SU

S

UN

SA

TU

RA

TED

CH

AIN

S

Saturated

All single bonds with H

Most animal fats Solid, close

bonds; e.g butter

Unsaturated

Carbon carbon double bonds

Most plant and fish fats

Liquid, can’t bind close = bend; e.g olive oil

PHOSPHOLIPIDS

Makes up cell membranes Glycerol with 2 FA’s and 1

phosphate (negative charge) Hydrocarbons make

hydrophobic (form tails) Phosphate and attachment

are hydrophilic (form heads)

Bi-layered to protect hydrophobic from water

STEROIDS

Lipids with 4 fused rings Synthesized from cholesterol, common in

animal cell membranes Precursor to sex hormones Synthetic variants

Anabolic steroids (Testosterone)

PROTEINS

Necessary for almost anything living organisms do

Know types and functions from table 5.1 Enzymes regulate metabolism by acting as

catalysts Speed reactions w/o being consumed

Unique 3D shapes Formed from polypeptides (polymers of

amino acids) 20 AA’s, same set for all Protein = 1+ polypeptide folded and coiled into

specific 3D shape

AMINO ACID MONOMERS Common structure

Carboxyl and amino group

α-carbon is middle with H and R group (variable) Determines specific AA

from fig. 5.17

Side chains grouped by properties Nonpolar, hydrophobic Polar, hydrophilic Acidic, (-) charge b/c

carboxyl group Basic, (+) charge b/c

amino group Charges = hydrophilic

Polymers formed by peptide bonds

STRUCTURE AND FUNCTION

Polypeptides ≠ protein AA sequence does 4 levels of structure

1°-seq of AA, determined by genes 2°-repeated coils or folds for overall shape

H-bonds b/w carboxyl and amino backbone α-helix = H bonds b/w 4th AA ß-pleated sheet = 2+ regions of H bonds

3 °- interactions b/w side chains Hydrophobic interaction = side chains cluster in Disulfide bridges = -SH side chain interactions

4°-overall structure of 2+ polypeptides

PROTEIN STRUCTURE AND FUNCTION Polypeptides ≠

protein 1°: genes decide 2°: H-bonds b/w

carboxyl and amino

α-helix: 4th AA Β-sheet: 2+

regions of side by side H-bonds

3°: hydrophobic side chains and disulfide bridges

4 : 2+ polypeptides

CHANGING PROTEIN STRUCTURE

Sickle cell Single AA substitution in hemoglobin

Abnormal shape RBC’s that clogs vessels

Denaturation Proteins unravel and lose shape pH, [salt], temp, and other effects can cause Inactivates proteins

Removing agents might reverse

Misfolding Accumulate and cause detrimental problems E.g Alzheimer’s and Parkinson’s disease

Often times unfolding exposes hydrophobic areas to the aqueous solutions surrounding the protein

Aggregates to protect itself

PR

OTEIN

MIS

FO

LD

ING

NUCLEIC ACIDS Polymers of nucleotides (polynucleotides)

Blueprint for proteins to control all of cellular workings

Control of reproduction DNA RNA proteins

Central dogma of molecular biology Occurs in ribosomes

Monomer is a nucleotide Structure consists of 3 components

Nitrogenous base 5 carbon sugar Phosphate group

NUCLEOTIDE

Nitrogenous base Pyrimidine = a 6 member carbon and nitrogen

ring cytosine (C), thymine (T), uracil (U)

Purines = 6 member carbon ring fused to a 5 member ring (smaller name, bigger structure) adenine (A) and guanine (G)

DNA – C, T, G, and A RNA – C, U, G, and A

5 Carbon sugar Ribose Deoxyribose (missing oxygen)

NUCLEOTIDE POLYMERS

Phosphodiester linkage = phosphate joins sugars of 2 nucleotides For backbone of DNA Phosphate on 5’ carbon joins hydroxyl on 3’

carbon DNA codes 5’ -3’ Sequence of bases unique to each gene

Linear order of nitrogenous bases in a gene specifies AA sequence (which level of structure ?) Start codon

ATG and AUG = DNA and RNA Stop codon

UAG, UAA, UGA

DOUBLE HELIX

1st proposed by Watson and Crick Sugar-phosphate

backbones are antiparallel

Nitrogenous bases face in and H-bonds hold them together

2 strands are complementary

Binding specific A binds w/ T G binds w/ C