biology 112 chapter 5 macromolecules. all living things are made up of four classes of large...

Biology 112Chapter 5

Macromolecules

MacromoleculesAll living things are made up of four classes

of large biological molecules: carbohydrates, lipids, proteins, and nucleic acids

Molecular function relates to molecular structure

Diversity of molecular structure is the basis for the diversity of life.

Most macromolecules are PolymersPolymer = Large molecule consisting of

many identical or similar subunits (monomers) connected together.

Three of the four classes of life’s organic molecules are polymers:CarbohydratesProteinsNucleic acids

Synthesis of PolymersCondensation (dehydration) reactions =

polymerization reactions during which monomers are covalently linked. This produces a net removal of one water molecule for each covalent linkage formed.

Breakdown of PolymersHydrolysis = reaction process that breaks

covalent bonds between monomers by the addition of water molecules.

Unity and DiversityA limitless variety of polymers

can be built from a small set of monomer building blocks.

Each cell has thousands of different kinds of macromolecules

Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species.

Unity…only about 40-50 common monomers are used

Diversity…emerges as these universal building blocks are arranged in different ways.

CarbohydratesCarbohydrates include sugars and the

polymers of sugarsThe simplest carbohydrates are

monosaccharides, or single sugarsMonosaccharidesMajor nutrient for cells. Glucose is most

common.Can be produced by photosynthesis from CO2,

H2O and sunlight.Energy stored in their chemical bonds which is

harvested by cellular respiration.Their carbon “skeletons” are the raw material

for other organic moleculesAre the monomers for polysaccharide polymersMany form ring structures in aqueous solutions

DisaccharidesA disaccharide is formed when a

dehydration reaction joins two monosaccharides

This covalent bond is called a glycosidic linkage.

PolysaccharidesStorage

PolysaccharidesStarchGlycogen

Structural PolysaccharidesCelluloseChitin

LipidsLipids are the one class of large biological

molecules that do not form polymersThe unifying feature of lipids is having little

or no affinity for water. They are hydrophobic. They are nonpolar.

Lipids are hydrophobic becausethey consist mostly of hydrocarbons, which form nonpolar covalent bonds

The most biologically important lipids are fats, phospholipids, and steroids

FatsFats are constructed from two types of

smaller molecules: glycerol and fatty acidsGlycerol is a three-carbon alcohol with a

hydroxyl group attached to each carbonA fatty acid consists of a carboxyl group

attached to a long carbon skeletonIn a fat, three fatty acids are joined to

glycerol by an ester linkage, creating a triacylglycerol, or triglyceride

Fat synthesis

SaturationFatty acids vary in length

(number of carbons) and in the number and locations of double bonds

Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds

Unsaturated fatty acids have one or more double bonds

Fats made from saturated fatty acids are called saturated fats, and are solid at room temperature. (Most animal fats are saturated)

Fats made from unsaturated fatty acids are called unsaturated fats or oils, and are liquid at room temperature. (Plant fats and fish fats are usually unsaturated)

A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits

Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen

Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds

These trans fats may contribute more than saturated fats to cardiovascular disease

Functions of Fats:

Energy storage!A high energy compact form of fuel

storage.Insulates against heat lossCushions some vital organs in mammals

(Kidneys)

PhospholipidsComposed of glycerol, 2 fatty acids and a

phosphate group ( and usually an additional chemical group attached to the phosphate.

Hydrophilic headsHydrophobic tails

Spontaneously form a phospholipid bilyer in an aqueous environment

Major constituents of biological membranes.

Phospholipids

SteroidsSome hormones are steroids. (estrogen,

testosterone)Steroids are common components of

animal membranes (cholesterol)

ProteinsPolypeptides = polymers

of amino acids in a specific sequence that are linked by peptide bonds.

Amino acids Carboxyl groupAmino groupA variable R group specific

to each amino acid. The physical and chemical properties of these groups give the uniqueness to each amino acid. (polar/nonpolar ; charged/uncharged ; acidic/basic)

20 common amino acids

Amino Acids

Peptide bonds

Protein structureA protein’s function depends upon its unique

conformation!!!!4 levels of protein structure

Primary --unique A.A. sequenceSecondary-- regular repeated coiling or folding

Alpha helixBeta pleated sheet

Tertiary -- irregular contortions due to bonding between side chains (R groups)Weak interactions

Hydrogen bonds Ionic bondsHydrophobic interactions

Covalent bonds – Disulfide bridgesQuaternary -- results when two or more

polypeptide chains form one macromolecule

Primary structure

Secondary structure

Tertiary structure

Quaternary structure

DenaturationDenaturation = a process that alters a

protein’s native conformation and biological activity.

Protein Functions

Sickle-Cell DiseaseA slight change in

primary structure can affect a protein’s structure and ability to function

Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

Nucleic AcidsNucleic acids are polymers of nucleotides

linked together by condensation reactions. (DNA and RNA)

NucleotidesNucleotides are composed of :

5-carbon sugarphosphate group nitrogenous base

PyrimidinesCytosineThymineUracil

PurinesAdenineGuanine

Nucleotide functions:monomers for nucleic acidstransfer of chemical energy (ATP)act as electron acceptors

The Roles of Nucleic Acids

There are two types of nucleic acids:Deoxyribonucleic acid

(DNA)Ribonucleic acid

(RNA)DNA provides directions

for its own replicationDNA directs synthesis of

messenger RNA (mRNA) and, through mRNA, controls protein synthesis

Protein synthesis occurs in ribosomes

Inheritance is based on the precise replication of DNA

EvolutionDNA and Proteins can serves as

measures of evolutionThe more closely related species have

more similar sequences of DNA and therefore also more similar proteins.