Bio lesson 4

molecular composition of a typical cell

-70% water, 4% small molecules, 26% macromolecules

-macromolecules: 15% proteins, 2% polysaccharides, 6% RNA, 1% DNA, 2% lipids

carbon

-framework for most biological molecules

-C atoms may bind to other carbon atoms, or to atoms of H, O, N, phosphorous or sulfur

-2 ex. of organic molecules: butane (hydrocarbon), alanine (amino acid)

-butane: hydrocarbons store energy in the many C-H bonds and act as fuel. nonpolar since H and C both have about the same electronegativity, so therefore, it is hydrophobic

-alanine: ex. of molecule where multiple different types of atoms are bound to the carbon framework. most molecules that contain O, P, N, sulphur create polar regions which are ex of functional groups (diff. functional groups have specific chem. properties)

common functional groups

-hydroxyl

common functional groups

-hydroxyl:

ex molecule: ethanol

general classes of bio. molecules that contain each functional group: carbs, protiens, nucleic acids, lipids

-carbonyl:

acetaldehyde

carbs, nucleic acids

-carboxyl:

acetic acid

proteins, lipids

-amino:

alanine

proteins, nucleic acids

-sulfhydryl

cysteine

proteins

-phosphate

glycerol phosphate

nucleic acids

-methyl

alanine

proteins

function of carbs

energy storage

structural support

function of proteins

enzymes

structural support

nucleic acids

storage

expression of genetic info

lipids

energy storage

membrane structure

cell communication

carbohydrates

-cellular structure: starch grains in a chloroplast

-polymer: starch

-monomer: monosaccharide

carbs are assembled from monosaccharide subunits

nucleic acid

-cellular structure: chromosome

-polymer: DNA strand

-monomer: nucleotide

nucleic acids are assembled from nucleotide subunits

protein

-cellular structure: intermediate filament

-polymer: polypeptide

-monomer: amino acids

lipid

-cellular structure: adipose cell w/ fat droplets

-polymer: triglyceride

-monomer: fatty acid

carbs are assembled from monosaccharides

-simple sugars

-contain C, H, O in a 1:2:1 ration

-bonds store energy

-typically have 3-6 carbons

-common ex: 3 C sugars (glyceraldehyde), 5 C sugars (ribose, deoxyribose), 6 C sugars (glucose, fructose, galactose)

structural features of monosaccharides

-glucose: linear, ring, alpha-glucose or beta-glucose

-ring: ring closure involves formation of covalent bond btwn hydroxyl oxygen of C5 and C1 so that the oxygen is part of the ring and C6 extends from the ring. closure occurs so that 2 forms can result

isomers

-molecules that have the same chem formula

-ex of monosaccharide isomers: fructose, glucose, galactose

-although they have the same formula, they are distinct cells w/ different functions and activities

disaccharides

-formed by covalent linkage of 2 monosaccharides

-in some cases, disaccharides have functional roles such as acting as a transport form to move sugars from one part of an organism to another

polysaccharides

-monosaccharides and disaccharides can assemble into much longer polymers

-starch

nucleic acids are assembled from nucleotides

-nucleotides contain a 5-C pentose sugar, phosphate group, and nitrogenous base

-% C of the pentose sugar are designated as 1”, 2”, etc. The base is covalently attached to the 1’ and the phosphate group is attached to the 5’

-nitrogenous bases can be purines or pyrimidines

purines

-A, G

-double ringed molecules

pyrimidines

-C, T, U

-single ringed molecules

structure of DNA

-double helix

-2 strands run anti-parallel to one another

-antiparallel strands and pairing of specific bases means that the sequence of one strand can be deduced from the sequence of the other

-H bonds btwn nitrogenous bases

nucleotides function in many energy reactions

-adenosine: base adenine is linked to a sugar

-triphosphate: 3 phosphates

-the chem. energy associated w/ ATP is contained in the linkage btwn 2nd and 3rd phosphate groups

-ATP is the energy currency of the cell

proteins are functionally diverse

enzymes: proteases, polymerases

movement: actin, myosin

structural: collagen, keratin

defense: antibodies, venoms

R group

-functional group that determines the chem. property of each amino acid

-each type of amino acid has a different R group (side chain)

amino acids

-monomers of proteins

-has an amino group, carboxyl group and R group

-each of these groups is covalently attached to a central C along w/ a H atom and the R group

-certain amino acids are associated w/ specific functions within proteins

peptide bond

-covalent bond created through a dehydration reaction

-amino acids assemble via peptide bond formation

-this dehydration reaction doesn’t occur spontaneously, catalyzed by ribosome

-direction of synthesis: N-terminus to C- terminus (amino to carboxyl)

every type of protein has a unique AA sequence

-protein sequence determines protein structure, determines protein function (activity)

-changes in amino acid sequence (as a result of changes in genetic info caused by mutations) can change the structure and function of a protein. Changes in structure as a result of chem. modification or the binding of a small molecule/another protein can change whether or not a protein is active

-primary structure created by covalent peptide bonds that link amino acids into polypeptides. AA sequence= primary structure

protein secondary structure

-2 types of secondary structures: beta sheet and alpha helix

-beta sheet: planar (flat sheet)

-alpha helix: cylinder

protein tertiary structure

-generated by interactions btwn amino acids far apart in sequence

-these interactions bring tg secondary structure elements that are connected by flexible stretches of amino acids termed loops

-may involve H bonds, ionic interactions, covalent (disulfide) bonds, hydrophobic interactions

protein quaternary structure

-some proteins may require 2+ polypeptide chains to form a functional protein

-quaternary: interaction btwn 2+ polypeptides (subunits)

-each polypeptide first folds into its tertiary structure before association w/ other subunits

-generated by the same bonds that produce tertiary structure

denaturation

-inactivates proteins

-if the protein’s environment is altered, the protein may change its structure and possibly unfold

-changes in pH, temo, or ionic concentration of surrounding solution leads to denaturation

-renaturation is sometimes possible