Molecules of LifeChapter 2 Part 22.6 Organic Molecules

The molecules of life carbohydrates, proteins, lipids, and nucleic acids are organic molecules

OrganicType of molecule that consists primarily of carbon and hydrogen atomsSome Elemental AbundancesModeling an Organic MoleculeBuilding Organic Molecules

Carbon atoms bond covalently with up to four other atoms, often forming long chains or rings

Enzyme-driven reactions construct large molecules from smaller subunits, and break large molecules into smaller ones

From Structure to Function

Cells assemble large polymers from smaller monomers, and break apart polymers into component monomers

MetabolismAll the enzyme-mediated chemical reactions by which cells acquire and use energy as they build and break down organic molecules

Monomers and Polymers

MonomersMolecules that are subunits of polymersSimple sugars, fatty acids, amino acids, nucleotides

PolymersMolecules that consist of multiple monomersCarbohydrates, lipids, proteins, nucleic acidsCondensation and Hydrolysis

Condensation (water forms)Process by which an enzyme builds large molecules from smaller subunits

Hydrolysis (water is used)Process by which an enzyme breaks a molecule into smaller subunits by attaching a hydroxyl to one part and a hydrogen atom to the other

Condensation and HydrolysisAnimation: Condensation and hydrolysisAnimation: Functional groups2.7 Carbohydrates

Cells use carbohydrates for energy and structural materials

CarbohydratesMolecules that consist primarily of carbon, hydrogen, and oxygen atoms in a 1:2:1 ratio

Complex Carbohydrates

Enzymes assemble complex carbohydrates (polysaccharides) from simple carbohydrate (sugar) subunits

Glucose monomers can bond in different patterns to form different complex carbohydratesCellulose (a structural component of plants)Starch (main energy reserve in plants)Glycogen (energy reserve in animals)Some Complex Carbohydrates

Animation: Structure of starch and celluloseAnimation: Examples of monosaccharides2.8 Lipids

Lipids are greasy or oily nonpolar organic molecules, often with one or more fatty acid tails

LipidsFatty, oily, or waxy organic compounds

Fatty acidConsists of a long chain of carbon atoms with an acidic carboxyl group at one endFatsFats, such as triglycerides, are the most abundant source of energy in vertebrates stored in adipose tissue that insulates the body

FatLipid with one, two, or three fatty acid tails

TriglycerideLipid with three fatty acid tails attached to a glycerol backboneSaturated and Unsaturated Fats

Saturated fats pack more tightly than unsaturated fats, and tend to be more solid

Saturated fatFatty acid with no double bonds in its carbon tail

Unsaturated fatLipid with one or more double bonds in a fatty acid tailFatty AcidsSaturated, unsaturated, cis, and trans fatty acids

Phospholipids

Phospholipids are the main structural component of cell membranes

PhospholipidA lipid with a phosphate group in its hydrophilic head, and two nonpolar fatty acid tails

Phospholipids

Waxes

Waxes are part of water-repellent and lubricating secretions in plants and animals

WaxWater-repellent lipid with long fatty-acid tails bonded to long-chain alcohols or carbon rings

Steroids

Steroids such as cholesterol occur in cell membranes or are remodeled into other molecules (such as steroid hormones, bile salts, and vitamin D)

SteroidA type of lipid with four carbon rings and no fatty acid tails

SteroidsAnimation: Fatty acidsAnimation: Triglyceride formationAnimation: Phospholipid structureAnimation: Cholesterol2.9 Proteins

A proteins function depends on its structure, which consists of chains of amino acids that twist and fold into functional domains

ProteinOrganic compound that consists of one or more chains of amino acids

Amino AcidAmino acidSmall organic compound with a carboxyl group, amine group, and a characteristic side group (R)

Peptide Bonds

Amino acids are linked into chains by peptide bonds

Peptide bondA bond between the amine group of one amino acid and the carboxyl group of another

PolypeptideChain of amino acids linked by peptide bondsPolypeptide Formation

Animation: Peptide bond formationProtein Synthesis

1. Primary structure (polypeptide formation) A linear sequence of amino acids

2. Secondary structureHydrogen bonds twist the polypeptide into a coil or sheet

3. Tertiary structureSecondary structure folds into a functional shapeProtein Synthesis

4. Quaternary structure In some proteins, two or more polypeptide chains associate and function as one moleculeExample: hemoglobin

5. Fibrous proteins may aggregate into a larger structure, such as keratin filamentsExample: hairProtein Structure

Animation: Secondary and tertiary structureThe Importance of Protein Structure

Changes in a proteins structure may also alter its function

DenatureTo unravel the shape of a protein or other large biological molecule

Misfolded Proteins: Prion Disease

Prion A misfolded protein that becomes infectiousExample: mad cow disease (BSE) in cattleExample: vCJD in humansVariant Creutzfeldt-Jakob Disease (vCJD)

Animation: Structure of an amino acidAnimation: Molecular models of the protein hemoglobinAnimation: Globin and hemoglobin structure2.10 Nucleic Acids

NucleotideMonomer of nucleic acidsHas a five-carbon sugar, a nitrogen-containing base, and phosphate groups

Nucleic acidsPolymers of nucleotide monomers joined by sugar-phosphate bonds (include DNA, RNA, coenzymes, energy carriers, messengers)ATP

The nucleotide ATP can transfer a phosphate group and energy to other molecules, and is important in metabolism

Adenosine triphosphate (ATP)Nucleotide that consists of an adenine base, five-carbon ribose sugar, and three phosphate groupsFunctions as an energy carrier

Functions of DNA and RNA

DNA encodes heritable information about a cells proteins and RNAs

Different RNAs interact with DNA and with one another to carry out protein synthesisDNA and RNA

Deoxyribonucleic acid (DNA)Nucleic acid that carries hereditary materialTwo nucleotide chains twisted in a double helix

Ribonucleic acid (RNA)Typically single-stranded nucleic acidFunctions in protein synthesisA Nucleotide and Nucleic Acid

Animation: Structure of ATPAnimation: Subunits of DNA2.11 Impacts/Issues Revisited

Our enzymes cant easily break down trans fats in processed foods, which causes health problems several countries will not import foods made in the US that contain trans fats Digging Into Data:Effects of Fats on Lipoprotein Levels