+ Structure and Function of Large Biological Molecules

+

Structure and Function of Large Biological Molecules

+Macromolecules

4 main types: carbohydrates, lipids, proteins, nucleic acids

Large molecules typically made of smaller subunits

Carbs, Nucleic acids, proteins = Polymers – built from monomers

+Synthesizing and Decomposing Macromolecules:

Dehydration Synthesis: “adding” monomers together to form a polymer.

Removal of an H2O molecule covalently bonds the monomers.

Hydrolysis: Breaking down of polymers into smaller subunits using water.

The H bonding to one monomer and the OH bonding to the other.

Both processes use enzymes!

+

Sugars and sugar chains – the fuel and building materials of life

Carbohydrates

+

Monosaccharides: Simple SugarsSugar units have empirical formula: CH2O

C chains range from 3-7

Enantiomers – different sugars!

5-6 C typically are aromatic!

+Glucose is Life

C1 and C5 bond to form ring

Glucose is a primary cellular fuel source for respiration

Glucose is also used as a building block for many other macromolecules

Can be stored for later use as di- and polysaccharides

2 forms of the rings α and βhttp://pslc.ws/macrog/kidsmac/toon_glu.htm

+α-glucose and β-glucose

+Disaccharides Through Dehydration Synthesis

2 monosaccharides bonded

Glycosidic linkage formed by dehydration synthesis

Disaccharides: maltose, sucrose, lactose

Linkages are named by the carbons that bond

Maltose is a 1-4 glycosidic linkage

Sucrose is a 1-2 glycosidic linkage

+Types of Glycosidic Linkages

1–4glycosidic

linkage

1–2glycosidic

linkage

Maltose

Sucrose

+Polysaccharides – huge chains of monosaccharides

Each monomer is added through dehydration synthesis

Huge chains are good for storage and even structure

Function of the poly- determined by type of linkage and sugar monomers

+Storage Polysaccharides

Plants create starch for storage

Glucose monomers = stored energy

Stored in plastids

Formed by 1-4 glycosidic linkages

+Storage Polysaccharides

Animals synthesize glycogen

Glucose monomers – high branched

Stored in liver and muscle

+

Structural Polysaccharides Cellulose – major

component of cell walls

Most abundant organic molecule on earth

Glucose monomers – different linkages!

Different forms of glucose but same 1-4 linkage!

+Cellulose: Tough Cell Walls…

Why?

Cellulose is straight chains and never branched

Form parallel chains

Different enzymes to digest!

Fiber

Chitin = exoskeletons

+

Hydrophobic, diverse molecules

Lipids

+Lipid Basics: Hydrophobic energy chains

Lipids are diverse in function but similar in their hydrophobicity

Typically have large regions that are hydrocarbon chains

+Building Blocks of Fats

Fatty acid chains Glycerol

+Triacylglycerol (TAGs)

AKA Triglycerides

Ester linkage!

Dehydration Synthesis! x3

+Saturated and Unsaturated Fats

Naturally occurring fatty acids have cis double bonds

+Cis vs Trans Fats

+Figure 5.12

Choline

Phosphate

Glycerol

Fatty acids

Hydrophilichead

Hydrophobictails

(c) Phospholipid symbol(b) Space-filling model(a) Structural formula

Hyd

rop

hilic

head

Hyd

rop

hob

ic t

ails

+Figure 5.13

Hydrophilichead

Hydrophobictail

WATER

WATER

+Steroids

Steroids have 4 carbon ring structures

Can be hormones or cholesterol

+

Multiple units, multiple uses

Proteins

+Functions of Protein

Proteins account for ~50% of the dry mass of most cells

Proteins act as catalysts, play roles in defense, storage, transport, and cellular communication

Greatest diversity in structure and function

+Figure 5.15-a

Enzymatic proteins Defensive proteins

Storage proteins Transport proteins

Enzyme Virus

Antibodies

Bacterium

Ovalbumin Amino acidsfor embryo

Transportprotein

Cell membrane

Function: Selective acceleration of chemical reactionsExample: Digestive enzymes catalyze the hydrolysisof bonds in food molecules.

Function: Protection against disease

Example: Antibodies inactivate and help destroyviruses and bacteria.

Function: Storage of amino acids Function: Transport of substances

Examples: Casein, the protein of milk, is the majorsource of amino acids for baby mammals. Plants havestorage proteins in their seeds. Ovalbumin is theprotein of egg white, used as an amino acid sourcefor the developing embryo.

Examples: Hemoglobin, the iron-containing protein ofvertebrate blood, transports oxygen from the lungs toother parts of the body. Other proteins transportmolecules across cell membranes.

+Figure 5.15-b

Hormonal proteinsFunction: Coordination of an organism’s activitiesExample: Insulin, a hormone secreted by thepancreas, causes other tissues to take up glucose,thus regulating blood sugar concentration

Highblood sugar

Normalblood sugar

Insulinsecreted

Signalingmolecules

Receptorprotein

Muscle tissue

Actin Myosin

100 m 60 m

Collagen

Connectivetissue

Receptor proteinsFunction: Response of cell to chemical stimuliExample: Receptors built into the membrane of anerve cell detect signaling molecules released byother nerve cells.

Contractile and motor proteinsFunction: MovementExamples: Motor proteins are responsible for theundulations of cilia and flagella. Actin and myosinproteins are responsible for the contraction ofmuscles.

Structural proteinsFunction: SupportExamples: Keratin is the protein of hair, horns,feathers, and other skin appendages. Insects andspiders use silk fibers to make their cocoons and webs,respectively. Collagen and elastin proteins provide afibrous framework in animal connective tissues.

+Protein Building Blocks - Peptides

All proteins are made of 20 different amino acids

Amino end

Carboxyl end

R = functional group

α CARBON

+Proteins are Polypeptides

Polymers of peptides are made through the formation of peptide bond

Carboxyl end of one AA bonds to the amino end of adjacent AA

Dehydration reaction to form peptide bond

N terminus (+) and C terminus (-)

+Figure 5.16

Nonpolar side chains; hydrophobic

Side chain(R group)

Glycine(Gly or G)

Alanine(Ala or A)

Valine(Val or V)

Leucine(Leu or L)

Isoleucine (Ile or I)

Methionine(Met or M)

Phenylalanine(Phe or F)

Tryptophan(Trp or W)

Proline(Pro or P)

Polar side chains; hydrophilic

Serine(Ser or S)

Threonine(Thr or T)

Cysteine(Cys or C)

Tyrosine(Tyr or Y)

Asparagine(Asn or N)

Glutamine(Gln or Q)

Electrically charged side chains; hydrophilic

Acidic (negatively charged)

Basic (positively charged)

Aspartic acid(Asp or D)

Glutamic acid(Glu or E)

Lysine(Lys or K)

Arginine(Arg or R)

Histidine(His or H)

+Figure 5.16a

Nonpolar side chains; hydrophobic

Side chain

Glycine(Gly or G)

Alanine(Ala or A)

Valine(Val or V)

Leucine(Leu or L)

Isoleucine(Ile or I)

Methionine(Met or M)

Phenylalanine(Phe or F)

Tryptophan(Trp or W)

Proline(Pro or P)

+Figure 5.16b

Polar side chains; hydrophilic

Serine(Ser or S)

Threonine(Thr or T)

Cysteine(Cys or C)

Tyrosine(Tyr or Y)

Asparagine(Asn or N)

Glutamine(Gln or Q)

+Figure 5.16c

Electrically charged side chains; hydrophilic

Acidic (negatively charged)

Basic (positively charged)

Aspartic acid(Asp or D)

Glutamic acid(Glu or E)

Lysine(Lys or K)

Arginine(Arg or R)

Histidine(His or H)

+Figure 5.17

Peptide bond

New peptidebond forming

Sidechains

Back-bone

Amino end(N-terminus)

Peptidebond

Carboxyl end(C-terminus)

Dehydration synthesis

Side chains vary in their charge, polarity, length

+Protein – Structure Dictates Function

3D structure of each protein is unique

Structure dictates function

Structure is determined due to 4 levels of folding

Most fundamental level of folding is sequence of AA

+Figure 5.19

Antibody protein Protein from flu virus

Primary Structure AA

SequenceSequence of AA

Read in order from N to C

Dictates secondary, tertiary, quaternary levels

+Secondary Structure

Regions of a peptide chain that are coiled or folded into patterns

Regulated by H bonding of atoms in the peptide backbone

α-Helix

β-sheets

+Tertiary

Structure

Overall shape of a protein

Stabilized by R groups and how they interact

Hydrophobic Interactions

Disulfide Bridges

Quaternary Structure

The interaction of multiple polypeptide chains

Forms a functional protein

Separate peptide chains

+Chaperonins: Protein Folders

+Protein Structure in a Cell

Folding is spontaneous

Other proteins aid in this process

Denaturation – unraveling/misfolding of a protein

+

Blueprints of life

Nucleic Acids

+Nucleotides

Monomers of nucleotides

2 types: DNA and RNA Deoxyribonucleic

acid Ribonucleic acid

+DNA to RNA to Protein

Genetic material

Inherited

Codes for all genes

DNA RNA Protein

+Nucleotides

Types

2 Types of sugars Ribose Deoxyribose

2 Categories of N bases Purines (Pure As Gold)

A and G Pyrimidines

C, T, U

+Polynucleotides – Nucleic Acids

Nucleotides are linked by a phosphodiester bond

Adjacent sugars are linked from 5’ end to first sugar to 3’ of next sugar

N Bases point inwards and provide “sequence” of DNA

+

Structure of DNA

Double helix

Sugar-phosphates are antiparallel

Bases pair 1 purine to 1 pyrimidine