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Structure and Function of Macromolecules

L. RuedaL. Rueda

AP BiologyAP Biology

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How Cells Use Organic Compounds

Biological organisms use the same kinds of building blocks.

All macromolecules (large, complex molecules) have specific functions in cells.

Other than water, macromolecules make up the largest percent mass of a cell.

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Condensation and Hydrolysis

Condensation[aka dehydration synthesis]

Two molecules combine with loss of water to form larger molecule.

Requires enzymes and energy.

Hydrolysis A molecule splits

into two smaller ones with addition of water.

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The Molecules of Life

Living cells synthesize Carbohydrates

Lipids

Proteins

Nucleic acids

Large polymers form from smaller monomers. New properties emerge.

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Carbohydrates

Used as energy and structural moleculesContain an aldehyde or a ketone group and

one or more hydroxyl groups. [Soluble]Organisms use D form but not L.Main types

Monosaccharides Disaccharides Polysaccharides

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Carbohydrates Monosaccharides

(CH2O)

Major cell nutrient, produced during PSN, raw material for other molecules.

6 Carbon sugars [Hexoses]

Glucose, Fructose, Galactose

5 Carbon sugars [Pentose]

Deoxyribose, Ribose

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Carbohydrates Disaccharides

Sucrose (glucose + fructose); table/cane sugar;

Lactose (glucose + galactose); milk sugar; unabsorbed in intestines if individuals lack lactase diarrhea

Maltose (glucose + glucose); beer, Whoppers!; formed during hydrolysis of starch by amylase.

Formed by condensation reactions (glycosidic linkage created)

Relative Sweetness of Sugars: Sucrose (100), Glucose (70), Fructose (170), Maltose (30), Lactose (16), Saccharin (40,000)

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Dissacharide Formation

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Carbohydrates Polysaccharides (aka

Complex carbos)

100s/1000s of monosaccharides long.

Energy Storage

Starch (amylose/amylopectin)

• digestible

Glycogen (highly branched)

Structural Support

Cellulose

Chitin

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Starch & Cellulose

Forms ring in aqueous sol’n

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LipidsLargely hydrocarbon; insoluble in waterDissolve in nonpolar substances

(chloroform, ether)Used for energy storage, structure and

chemical messenger. Lipids with fatty acids

Glycerides Phospholipids Waxes

Lipids with no fatty acids Steroids

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Fatty Acids

Carbon backbone (4 – 24 carbon atoms)

Carboxyl group (- COOH)

Unsaturated One or more double bonds

in backbone

Saturated All single bonds in

backbone

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Triglycerides Fats/Neutral fats

Three fatty acids and a glycerol

Condensation reaction forms ester linkage.

Most abundant lipid Non-polar, contain no

charged/polar functional groups

Functions: Energy storage in

adipocytes Insulation

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Phospholipids Glycerol backbone

Two fatty acid tails (hydrophobic)

Phosphate-containing head (negatively charged

therefore hydrophilic)

Amphipathic (both hydrophilic and hydrophobic regions)

Main materials of cell membranes

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Sterols

Steroids/Sterols No fatty acid tails

Four carbon ring

In eukaryotic cell membranes

Cholesterol in animals tissuesPrecursor to sex hormones and bile salts

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Waxes

Long-chained fatty acids linked to alcohols or carbon rings

Cover plant parts (Cuticle) Help conserve water Fend off parasites

Animals Protect, Lubricate, Impart pliability to skin and

hair Repel water (bird feathers, exoskeleton of

insects)

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Amino Acids and the Primary Structure of Proteins

Proteins Enzymes (Metabolism)

Structures (collagen & silk)

Transport and Movement (Lipoproteins, hemoglobin, actin/myosin, tubulin)

Nutritious (egg white, casein)

Hormones (chemical messengers, ex. Insulin/growth hormone)

Immune system (antibodies)

Two Classes: Globular and Fibrous

Proteins are made from a pool of 20 amino acids

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Structure of Amino Acids

Central carbon atom

An amino group

A carboxyl group

A hydrogen atom

One or more atoms “R Group”

Organisms use L form but not D.

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Peptide Bond FormationA type of condensation reaction

C-terminusN-terminus

Peptide Bond

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Protein Conformation

Conformation (shape) determines function and is the result of the linear sequence of amino acids in a polypeptide.

Folding, coiling and the interactions of multiple polypeptide chains create a functional protein.

4 Levels of Protein Structure. Primary (1°) Secondary (2°) Tertiary (3°) Quarternary (4°)

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Primary Structure

The unique, linear sequence determined by the mRNA.

A change in one a.a. can effect every other level of structure (eg. Point mutation in hemoglobin)

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Second Level of Protein Structure

Hydrogen bonding occurs between amino and carbonyl groups of amino acids.

Structures Formed: Alpha Helix. Common in

fibrous proteins, creates “elastic” properties.

Beta Sheet. Antiparallel chains form sheet.

Core of many globular proteins and inelastic fibrous proteins.

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Third Level of Protein Structure

Additional folding of secondary structure and bonding between R-groups. Hydrogen bonds

Disulfide bridges (strong)

Hydrophobic interactions

Ionic bonding

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Fourth Level of Protein Structure Two or more polypeptide

chains joined by Weak bonds (Hydrogen

bonds)

Covalent bonds between sulfur atoms and R groups

Collagen (3 helical polypeptides)

Insulin (2 polypeptides)

Hemoglobin (4 globular polypeptides)

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Structure of HairKeratin

Fibrous structural protein

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Four Levels of Protein Structure

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Structural Changes by Denaturation

Denaturation: altering a protein’s native conformation and activity.

Disruption of three-dimensional shape of protein

Temperature: thermal agitation

pH & Salts: additional H+/OH- or ions disrupts H-bonding, ionic and disulfide bridges

Non-Polar Solvents: protein turns “inside-out”

Some proteins have organic compounds attached Glycoproteins, Lipoproteins (common on

membranes)

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Nucleotides and The Nucleic Acids

Nucleotides Sugar

Ribose or Deoxyribose Phosphate group Bases

Single or double carbon rings with nitrogen

Subunits of coenzymes NAD+ and FAD

ATP Energy source for chemical reactions

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Structure of ATP

ATP Three phosphate groups

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Nucleic Acids - DNA and RNA

Building blocks Four kinds of

nucleotides

Differ only in component bases

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Single Strand of Nucleic Acid

A series ofcovalently bonded nucleotides

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DNA Double stranded Hydrogen bonds

between strands Twisted helically Four kinds of

nucleotide monomers (A, T, C, G)

Encodes protein-building instructions

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RNAs

Single strandedFour kinds of nucleotide monomers

(A, U, C, G)Do not encode protein-building

instructionsKey players in the protein-building

processesmRNA, tRNA, rRNA