Compounds of LifeBiological Molecules

By

Joseph A. Castellano, Ph.D.RESEED Silicon Valley

Reference: Reference: Focus on Physical ScienceFocus on Physical Science, Glencoe/McGraw-Hill, , Glencoe/McGraw-Hill, Columbus, Ohio, 2007, Pages 438-442. This textbook is used inColumbus, Ohio, 2007, Pages 438-442. This textbook is used inmany California Middle Schools.many California Middle Schools.

Biological molecules present in all living Biological molecules present in all living organisms include organisms include lipidslipids (fats and oils), (fats and oils), proteinsproteins, , nucleic acids nucleic acids and and carbohydratescarbohydrates..

Proteins, nucleic acids and carbohydrates are Proteins, nucleic acids and carbohydrates are large natural polymer molecules in all large natural polymer molecules in all

living living organisms that share the same few organisms that share the same few monomers: monomers:

- Amino acids make proteins- Amino acids make proteins- Nucleotides make nucleic acids (DNA)- Nucleotides make nucleic acids (DNA)- Sugars make complex carbohydrates- Sugars make complex carbohydrates

Biological MoleculesBiological Molecules

Nucleic AcidsNucleic Acids A A nucleic acidnucleic acid is a biomolecule found in all is a biomolecule found in all plant, animal and human cells.plant, animal and human cells.

RNA (RNA (rriboibonnucleic ucleic aacid) and DNA cid) and DNA ((ddeoxyriboeoxyribonnucleic ucleic aacid) store cellular cid) store cellular information in all living cells in the form of a information in all living cells in the form of a ““genetic codegenetic code.” .”

Every person’s genetic code is different. Every person’s genetic code is different. The The code in your cells determine the color of code in your cells determine the color of your your eyes and hair as well as every other feature eyes and hair as well as every other feature of of your body that is unique to you and only your body that is unique to you and only you. you.

Nucleotide MonomersNucleotide Monomers The nucleic acid DNA is composed of The nucleic acid DNA is composed of monomers called monomers called nucleotidesnucleotides..

A nucleotide is composed of a nitrogen base, a A nucleotide is composed of a nitrogen base, a sugar and a phosphate group: sugar and a phosphate group:

Nucleotide Monomer

Cytosine(a nitrogen base)

Nucleic Acid PolymersNucleic Acid Polymers The nucleic acid polymer, DNA, is composed The nucleic acid polymer, DNA, is composed

of nucleotides that have the same four of nucleotides that have the same four nitrogen nitrogen bases:bases:

- Adenine - Guanine - Cytosine - Thymine- Adenine - Guanine - Cytosine - Thymine

Scientists identify these four by the first Scientists identify these four by the first letter letter of their names: of their names: A, G, C, TA, G, C, T..

A single DNA molecule can have thousands A single DNA molecule can have thousands of of these nucleotides arranged in any number these nucleotides arranged in any number

of sequences (ATGCTGCA, etc.); the exact of sequences (ATGCTGCA, etc.); the exact sequence is the genetic code and is different sequence is the genetic code and is different

for for each person. each person.

DNA Chemical StructureDNA Chemical Structure

Methane

The dotted lines showThe dotted lines showhydrogen bonds, whichhydrogen bonds, whichhold the two strands ofhold the two strands ofnucleic acids togethernucleic acids togetherin a coil-likein a coil-likearrangementarrangementcalled a called a “double helix.”“double helix.”

DNA Molecular ModelDNA Molecular Model

Methane

LipidsLipids Lipids are fats and oils that contain carbon,Lipids are fats and oils that contain carbon,hydrogen and oxygen atoms.hydrogen and oxygen atoms.

Like hydrocarbons, lipids are Like hydrocarbons, lipids are non-polarnon-polar compounds that are not soluble in water.compounds that are not soluble in water.

Some lipids are long carbon chain, carboxylic Some lipids are long carbon chain, carboxylic acids often called acids often called fatty acidsfatty acids..

Neutral lipids in animal fats are fatty acids Neutral lipids in animal fats are fatty acids combined with glycerol to form compounds combined with glycerol to form compounds called called fattyfatty estersesters. .

Lipids – Fats and OilsLipids – Fats and Oils Fatty acid lipids can be Fatty acid lipids can be saturatedsaturated molecules with only molecules with only

single bonds between carbon atoms. Bacon contains single bonds between carbon atoms. Bacon contains the the solid saturated fatty acid, solid saturated fatty acid, stearic acidstearic acid..

Fatty acids with one or more double bonds between Fatty acids with one or more double bonds between carbons are called carbons are called unsaturated and are usually liquid. unsaturated and are usually liquid. Olive oil contains the unsaturated lipid, Olive oil contains the unsaturated lipid, oleic acidoleic acid. .

CarbohydratesCarbohydrates A A carbohydratecarbohydrate is anis an organic compound that organic compound that

contains the elements carbon, hydrogen, and contains the elements carbon, hydrogen, and oxygen. oxygen. Carbo-Carbo- stands for carbon and stands for carbon and

hydratehydrate for water. for water.

Simple Carbohydrates Simple Carbohydrates are sugars. There are are sugars. There are many different kinds of sugars. Some can many different kinds of sugars. Some can bought in boxes from the grocery store, but bought in boxes from the grocery store, but many are also present naturally in foods many are also present naturally in foods

such such as fruits and milk.as fruits and milk.

Carbohydrates are used by cells to store and Carbohydrates are used by cells to store and release energy.release energy.

Simple CarbohydratesSimple Carbohydrates The simplest carbohydrate is glucose. The The simplest carbohydrate is glucose. The

molecular formula molecular formula is:is:

CC66HH1212OO66

The The structural formula structural formula for glucose shows for glucose shows how how the atoms are arranged. the atoms are arranged.

Carbohydrates with only one carbonCarbohydrates with only one carbonring are called ring are called monosaccharidesmonosaccharides

Complex CarbohydratesComplex Carbohydrates AA complex carbohydrate complex carbohydrate is a long chain polymer is a long chain polymer

made up of simple carbohydrate monomers.made up of simple carbohydrate monomers.

Starch, cellulose and glycogen are all built from Starch, cellulose and glycogen are all built from glucose monomers, but the monomers are glucose monomers, but the monomers are arranged differently in each case.arranged differently in each case.

Starch and cellulose are found in plants, while Starch and cellulose are found in plants, while glycogen is present in liver and muscle cells. glycogen is present in liver and muscle cells.

Complex carbohydrates have many carbon rings,so they are called polysaccharides.

Polymers from GlucosePolymers from Glucose

Straight Polymer Chain BackboneStraight Polymer Chain Backbone

Branched Polymer Chain BackboneBranched Polymer Chain Backbone

CelluloseCellulose GlucoseGlucose

GlycogenGlycogen

Animal & HumanAnimal & HumanLiver & MusclesLiver & Muscles

Plants, Trees,Plants, Trees,Fruits, VegetablesFruits, Vegetables

ProteinsProteins Proteins are long chain polymer molecules Proteins are long chain polymer molecules

formed by connecting formed by connecting amino acids amino acids together.together.

Glycine is the simplest of the 20 common Glycine is the simplest of the 20 common amino amino acids that occur in nature.acids that occur in nature.

ProteinsProteins Proteins are made in human cells by a complex Proteins are made in human cells by a complex

process involving process involving DNADNA. .

The DNA directs the amino acids to combine The DNA directs the amino acids to combine with each other in a very specific sequence with each other in a very specific sequence

to to produce the desired protein for each organ. produce the desired protein for each organ.

For example, the protein collagen makes up For example, the protein collagen makes up skin while hemoglobin is the protein in skin while hemoglobin is the protein in

blood blood that carries oxygen to our cells.that carries oxygen to our cells.

Other proteins contract muscle tissue and Other proteins contract muscle tissue and fight fight viruses and bacteria that invade us. viruses and bacteria that invade us.

Protein StructureProtein Structure

Proteins in nature have a Proteins in nature have a helical structure, like a helical structure, like a

coil.coil.

The dashed lines in this The dashed lines in this protein molecular model protein molecular model represent “represent “hydrogen bondshydrogen bonds” ” that hold the atoms in the that hold the atoms in the coil-like structure.coil-like structure.

SummarySummary All living organisms are composed of All living organisms are composed of biological biological molecules that contain carbon, molecules that contain carbon, hydrogen, oxygen, hydrogen, oxygen, nitrogen and sometimes nitrogen and sometimes sulfur and phosphorous.sulfur and phosphorous.

Nucleic acids, proteins, lipids and Nucleic acids, proteins, lipids and carbohydrates carbohydrates are the main compounds of life.are the main compounds of life.

Biological molecules are formed from amino Biological molecules are formed from amino acids, sugars, long chain “fatty acids” and acids, sugars, long chain “fatty acids” and nucleotides.nucleotides.

Research on biological molecules leads to an Research on biological molecules leads to an understanding of the causes and cure of understanding of the causes and cure of

human human diseases.diseases.

This presentation was produced as a public service This presentation was produced as a public service to help middle school and high school science to help middle school and high school science teachers develop experiments, presentations and teachers develop experiments, presentations and demonstrations that can be used in their classes.demonstrations that can be used in their classes.

More science experiments and demonstrations are More science experiments and demonstrations are available on the RESEED Silicon Valley web site: available on the RESEED Silicon Valley web site: www.reseed-sv.org..

RESEEDRESEED ( (RRetirees etirees EEnhancing nhancing SScience cience EEducation ducation through through EExperiments and xperiments and DDemonstrations) is a emonstrations) is a program aimed at stimulating greater interest in program aimed at stimulating greater interest in science by middle school students. science by middle school students.