MOLECULES OF LIFECH5

• All living things are made up of 4 classes of large biomolecules:oProteinsoCarbohydratesoLipidsoNucleic acids

• Molecular structure and biological function are intricately related

I. Macromolecules

• Large molecules made of thousands of atoms covalently bonded

• 3 of the 4 biomolecules are polymers: proteins, carbs, nucleic acids

• Polymer: a macromolecules made of repeating units called monomers

The Synthesis and Breakdown of Macromolecules

• Macromolecules are made by dehydration reactions

• Macromolecules are broken down by hydrolysis reactions

II. Carbohydrates

• Sugars and the polymers of carbohydratesoMonosaccharidesoDisaccharidesopolysaccharides

A. Monosaccharides (CH2O)• structureo A single sugar ex:

glucoseo Classified by

number of carbons in chain and location of carbonyl

• functionoQuick energy sourceoImmediately enters into cellular

respiration for production of ATP

• Most monosaccharides exist as a ring

• isomersoMolecules with same structural formula

but different arrangement of atomsoEx: glucose, fructose, and galactose

B. Disaccharides• Structureo2 monosaccharides linked via

dehydration reactionsoEX: sucrose, lactose

• FunctionEnergy

C. Polysaccharides

• Long chain of GLUCOSE molecules linked via dehydration reactions

• 2 groups of polysaccharidesoStorage: starch and glycogenoStructural: cellulose chitin

1. Storage polysaccharides

• Glycogen– Stores glucose in animals–Many glucose molecules linked via α1-4

linkages• Starch– Stores glucose in plants–Many glucoses linked by α1-4 linkages– http://bcs.whfreeman.com/thelifewire/co

ntent/chp03/0302002.html

2. structural polysaccharides

• celluloseo forms cell wall in plantsomany glucoses linked via β1-4 linkages

• chitino forms exoskeleton in arthropods and cell

wall in fungi

• Most animals have enzymes to break α1-4 linkage but not β1-4 linkage.

• Most cellulose consumed exits as insoluble fiber

• Only some bacteria have enzymes to break β1-4 linkage

III. Lipids

• Diverse group of hydrophobic molecules• Only macromolecule that doesn’t form

polymer

A. Triglycerides (fats and oils)

• One glycerol + 3 fatty acids linked via dehydration reactions

http://www2.nl.edu/jste/biochem.htm

Fatty Acid

• Long chain of C and H with a carboxyl group

• Usually 14 to 20 Cs• Fatty acids can be–Saturated: no carbon to carbon double

bonds. Solid at room temp–Monounsaturated: 1 carbon to carbon

double bond. Liquid at room temp–Polyunsaturated: more than 1 carbon to

carbon double bond. Liquid at room temp

–Function of triglycerides• Long term energy storage• Seeds use stored triglycerides as energy

during germination• Insulation in mammals• http://bcs.whfreeman.com/thelifewire/

content/chp03/0302002.html

B. Phospholipids• StructureoOne glycerol + 2 fatty acids + 1 phosphate

head

• PropertyoAmphiphathic: polar charged phosphate

head and nonpolar uncharged fatty acid tails

• Function:oMake up phospholipid bilayer found in

all biological membranes

C. Waxes and Steroids• Waxes–Function as protective barrier

• Steroids–Function as chemical messengers

IV. Proteins

• About 50% of all macromolecules are proteins

A. Functions of Proteins

• Polypeptide: long chain of amino acids• Protein: biologically functional molecule

made of 1 or more polypeptides

B. Amino Acids: monomer of proteins

• general structureo all contain amino and

carboxyl group but differ in their R group

Groups of amino acids: based on the characteristics of R group

Linking of amino acids

• Link to form peptide bond by dehydration reaction

• Amino end of incoming amino acid links to carboxyl end of growing chain

• Each polypeptide has a unique order of amino acids

http://www2.nl.edu/jste/biochem.htmhttp://bcs.whfreeman.com/thelifewire/content/chp03/0302002.html

Protein Structure

• Protein structure is determined by the sequence of amino acids

• Structure determines its function• As protein is being synthesized, it begins to

fold into its correct shape• Proteins fold as a result of the interactions

between amino acids in the polypeptide chain• http://www.ncbi.nlm.nih.gov/sites/entrez?db

=structure

There are 4 levels of protein structure

• primary structure

• number and order of amino acids in the protein chain

• primary structure is determined by______________

• all proteins have a different primary structure

• secondary structure–Hydrogen bonding between amino and

carboxyl groups–2 forms: α helix and β sheet

• Tertiary structure– Interaction among the R groups of amino

acids – Interactions include ionic bonds,

hydrogen bonds, hydrophobic interactions, and covalent bonds–What type of amino acids involved in

each?

• Quaternary structure• 2 or more

polypeptide chains associated together to form a functional protein

• In a cell, special proteins called chaperonins help proteins fold into their shape

• http://parasol-www.cs.tamu.edu/groups/amatogroup/research/folding/proteinA.php

•  

D. Protein unfolding

• Denaturation: unfolding of a protein as a result of changes in pH and temp

V. Nucleic Acids

• The information molecules: contain the code to make proteins

• Structure– Long chains of nucleotides Nucleotides– Made of a:• 5 carbon sugar• Phosphate group• One of 4 bases

• Function–DNA: stores hereditary

info–RNA: expresses it