summer biology chapter 3

molecules that contain carbon and that are found in all forms of life are called

organic molecules

organic chemistry

carbon containing molecules

number of covalent bonds a carbon atom can form with other atoms is

4

Framework of biological molecules consists primarily of carbon bonded to

Carbon
Oxygen
Nitrogen
Sulfur
Phosphorus
Hydrogen

Hydrocarbons

molecules consisting only of carbon and hydrogen

hydrocarbons are

nonpolar

functional groups add chemical properties

Isomers

molecules with the same molecular or empirical formula

stereoisomers

differ in how groups attached

Enantiomers

mirror image molcules

chiral

D-sugars and L-amino acids

Macromolecules

four general classes

carbohydrates

lipids

proteins

nucleic acid

polymer - built by linking monomers

monomer - small similar chemical subunits

Dehydration synthesis

formation of large molecules by the removal of water

monomers are joined to form polymer

hydrolysis

breakdown of large molecules by the addition of water

polymers are broken down to monomers

Carbohydrates

•Molecules with a 1:2:1 ratio of carbon, hydrogen, oxygen

•Empirical formula (CH₂O)_n

•C—H covalent bonds hold much energy

–Carbohydrates are good energy storage molecules

–Examples: sugars, starch, glucose

monosaccharides

•Simplest carbohydrate

•6 carbon sugars play important roles

•Glucose C₆H₁₂O₆

•Fructose is a structural isomer of glucose

•Galactose is a stereoisomer of glucose

•Enzymes that act on different sugars can distinguish structural and stereoisomers of this basic six-carbon skeleton

disaccharides

•2 monosaccharides linked together by dehydration synthesis

•Used for sugar transport or energy storage

•Examples: sucrose, lactose, maltose

polysaccharides

•Long chains of monosaccharides

–Linked through dehydration synthesis

•Energy storage

–Plants use starch

–Animals use glycogen

•Structural support

–Plants use cellulose

–Arthropods and fungi use chitin

Protein functions include

1. Enzyme catalysis

  2. Defense

  3. Transport

  4. Support

  5. Motion

  6. Regulation

  7. Storage

amino acids

proteins are polymers

–Composed of 1 or more long, unbranched chains

–Each chain is a polypeptide

•Amino acids are monomers

•Amino acid structure

–Central carbon atom

–Amino group

–Carboxyl group

–Single hydrogen

–Variable R group

R group

groups determine the chemistry of the amino acid:

  1. Nonpolar - leucine

  2. Polar uncharged - threonine

  3. Charged - glutamic acid

  4. Aromatic - phenylalanine

  5. Unique – proline and cysteine

amino acids joined by dehyration synthesis

peptide bond

4 levels of structure

the shape of a protein determines its funciton

Primary structure –

sequence of amino acids

1.Secondary structure

– interaction of groups in the peptide backbone

a helix

b sheet

Tertiary structure

– final folded shape of a globular protein

–Stabilized by a number of forces

–Final level of structure for proteins consisting of only a single polypeptide chain

. Quaternary structure –

arrangement of individual chains (subunits) in a protein with 2 or more polypeptide chains

Motifs

–Common elements of secondary structure seen in many polypeptides

–Useful in determining the function of unknown proteins

domains

–Functional units within a larger structure

–Most proteins made of multiple domains that perform different parts of the protein’s function

Chaperones

•Once thought newly made proteins folded spontaneously

•Chaperone proteins help protein fold correctly

•Deficiencies in chaperone proteins implicated in certain diseases

–Cystic fibrosis is a hereditary disorder

•In some individuals, protein appears to have correct amino acid sequence but fails to fold

Denaturation

protein loses structure and function

-Ph

Temperature

Ionic concentration of solution

Polymer

nucleic acid

monomer

nucleotide

–sugar + phosphate + nitrogenous base

–sugar is deoxyribose in DNA or ribose in RNA

–Nitrogenous bases include

•Purines: adenine and guanine

•Pyrimidines: thymine, cytosine, uracil

–Nucleotides connected by phosphodiester bonds

DNA

forms a double helix, uses deoxyribose, and uses thymine among its nitrogenous bases.

RNA

is usually single-stranded, uses ribose, and uses uracil in place of thymine.

deoxyribonucleic acid

•Encodes information for amino acid sequence of proteins

–Sequence of bases

•Double helix – 2 polynucleotide strands connected by hydrogen bonds

–Base-pairing rules

•A with T (or U in RNA)

C with G

ribonucleic acid

•RNA similar to DNA except

–Contains ribose instead of deoxyribose

–Contains uracil instead of thymine

•Single polynucleotide strand

•RNA uses information in DNA to specify sequence of amino acids in proteins

ATP

•adenosine triphosphate

–Primary energy currency of the cell

•NAD⁺ and FAD⁺

–Electron carriers for many cellular reactions

Lipids

fats

hydrophobic lipids form

fats and membranes

lipids are a loosely defined group of molecules with one main chemical characteristic

they are insoluble in water

high proportion of nonpolar c-h bonds causes the molecule

to be hydrophobic

lipids include

fats, oils, waxes, and some vitamins

triglycerides

composed of 1 glycerol and 3 fatty acids

fatty acids

need not be identical

chain length varies

satured - no double bond between carbon atoms

• higher melting point, animal origin

unsatured - 1 or more double bonds

• low melting point plant origin

trans fat produced industrially

phospholipds

composed of

• glycerol

• 2 fatty acids - nonpolar “tails”

form all biological membranes

micelles

lipid molecules orient with polar (hydrophilic) head toward water and nonpolar (hydrophobic) tails away from water

phospholipid bilayer

more complicated structure where 2 layer form

• hydrophilic heads point outward

• hydrophobic tails point inward toward each other

other kinds of lipids

Terpenes are found in biological pigments, such as chlorophyll and retinal, and b. steroids play important roles in membranes and as hormones involved in chemical signaling.