Chapter 3Chapter 3::The Molecules of LifeThe Molecules of Life

Organic CompoundsOrganic Compounds Compounds in the natural

world that contain the element carbon (bonded to hydrogen).

Hydrocarbons – contain only C & H (ex. CH4)

Most also include oxygen and some also have nitrogen, phosphorus and sulfur.

Carbon can form thousands of different compounds because it can form 4 strong covalent bonds

Variations in Carbon SkeletonsVariations in Carbon Skeletons

Functional GroupsFunctional Groups

A group of atoms within a A group of atoms within a molecule that interacts in molecule that interacts in predictable ways with other predictable ways with other molecules is called a molecules is called a functional groupfunctional group

Functional groups Functional groups determine the properties of determine the properties of organic molecules. For organic molecules. For example, example, hydrophilic hydrophilic groups groups (such as –OH) attract water (such as –OH) attract water and and hydrophobichydrophobic groups groups repel. repel.

The Process of PolymerizationThe Process of Polymerization

The formation of carbon-based compounds

Monomers (small compounds) become Polymers (complex compounds)

Macromolecules are very large polymers

MonomerMonomerss

PolymerPolymer

Dehydration Synthesis & HydrolysisDehydration Synthesis & Hydrolysis

Compounds of Life (Biomolecules)Compounds of Life (Biomolecules)

There are four groups of organic compounds that are found in living things.

– Carbohydrates– Proteins– Lipids– Nucleic Acids

These compounds all come from our foods and are needed by our bodies.

Self-AssessmentSelf-Assessment Draw a molecule that has a 3-C (carbon) skeleton Draw a molecule that has a 3-C (carbon) skeleton

and a hydroxyl group on the middle carbon. and a hydroxyl group on the middle carbon. (Hint: formula is C(Hint: formula is C33HH88O)O)

Explain the connection between monomers and Explain the connection between monomers and polymers.polymers.

Draw at least three ways in which five carbon Draw at least three ways in which five carbon atoms can be drawn to make different carbon atoms can be drawn to make different carbon skeletons. skeletons.

What molecule is released during the What molecule is released during the construction of a polymer? What is this process construction of a polymer? What is this process called?called?

Try This:Try This:

The diagram below shows two amino acids, the monomers of a protein. Draw these amino acids in your notes. What has to happen for these two molecules to combine? (What must be done for bonds to be made in biological systems?) Represent this process by redrawing the amino acids bonded together and drawing the bi-product formed.

Dehydration SynthesisDehydration SynthesisIn living systems, bonds are made by removing water. An In living systems, bonds are made by removing water. An –OH from one molecule and an –H from the other combine –OH from one molecule and an –H from the other combine to form water. The removal of these atoms provides to form water. The removal of these atoms provides “space” for the new bond to form, by leaving atoms with “space” for the new bond to form, by leaving atoms with unfilled valence shells. unfilled valence shells.

CarbohydratesCarbohydrates

An Example of IsomersAn Example of Isomers The formula for all three monosaccharides glucose, The formula for all three monosaccharides glucose,

fructose and galactose is Cfructose and galactose is C66HH1212OO66

Although they contain the atoms in the same Although they contain the atoms in the same proportion, their structural arrangement differs. proportion, their structural arrangement differs.

In aqueous solutions, most monosaccharides form ring structures as shown for glucoseAlso note the trademark functional groups of sugars, multiple hydroxyl groups and a carbonyl group

Is fructose an aldose or a ketose?Is glucose an aldose or a ketose?

Carbohydrates: MonosaccharidesCarbohydrates: Monosaccharides Sugars Made of C, H, and O Can contain 2-7 carbons

– most have 5 (pentose) or 6 (hexose) Trademarks: 1 carbonyl group & multiple hydroxyls

– Hydroxyl group makes a sugar an alcohol– Carbonyl group makes it either an aldose (aldehyde sugar) or a ketose

(ketone sugar) Breaking of their covalent bonds releases energy (fuels cellular work)

Monosaccharide Examples (single sugars)– Glucose (sugar green plants produce)– Galactose (found in milk)– Fructose (found in fruits)

Three Ways to Represent GlucoseThree Ways to Represent Glucose

DisaccharidesDisaccharides Formed by the dehydration synthesis of 2 Formed by the dehydration synthesis of 2

monosaccharidesmonosaccharides ExamplesExamples::

– SucroseSucrose– LactoseLactose– MaltoseMaltose

Carbohydrates: PolysaccharidesCarbohydrates: Polysaccharides complex carbs made up of 100s-1000s of complex carbs made up of 100s-1000s of

monosaccharides (glucose)monosaccharides (glucose)

Takes a long time to digest and break down Takes a long time to digest and break down polysaccharides into glucose through hydrolysispolysaccharides into glucose through hydrolysis

Taste is not sweetTaste is not sweet ExamplesExamples::

StarchStarch: : used in plants as an energy storage moleculeused in plants as an energy storage molecule CelluloseCellulose: : makes up cell walls of plants; most abundant makes up cell walls of plants; most abundant

compound on Earthcompound on Earth Chitin: Chitin: found in exoskeleton of insects and crustaceans and found in exoskeleton of insects and crustaceans and

the cell walls of fungithe cell walls of fungi GlycogenGlycogen: : used by animals to store excess sugar (liver & used by animals to store excess sugar (liver &

muscles)muscles)

Self-AssessmentSelf-Assessment

1.1. Write the formula for a monosaccharide Write the formula for a monosaccharide that has 3 carbons. that has 3 carbons.

2.2. Why do isomers, which have the same Why do isomers, which have the same formula, have different properties?formula, have different properties?

3.3. Explain the relationship between a Explain the relationship between a monosaccharidemonosaccharide and a and a disaccharidedisaccharide. Give . Give an example of each.an example of each.

4.4. Compare and contrast starch, glycogen, Compare and contrast starch, glycogen, cellulose and chitin.cellulose and chitin.

LipidsLipids Non-polar; hydroNon-polar; hydrophobicphobic

Three categories: Three categories: TriglyceridesTriglycerides PhospholipidsPhospholipids steroidssteroids

Contain C, H & O, but lower Contain C, H & O, but lower proportion of oxygen than carbsproportion of oxygen than carbs

Lipids store more energy than Lipids store more energy than carbohydrates because they carbohydrates because they have twice as many energy rich have twice as many energy rich (C-H) bonds than carbohydrates. (C-H) bonds than carbohydrates. ((9 cal/g v. 4cal/g9 cal/g v. 4cal/g))

Categories of LipidsCategories of Lipids TrigylceridesTrigylcerides (Neutral Fats) (Neutral Fats)

– Glycerol & 3 fatty acids “tails”Glycerol & 3 fatty acids “tails”– Fatty tissue – insulation & reserve Fatty tissue – insulation & reserve

energyenergy PhospholipidsPhospholipids

– Polar phosphate “head” and non-Polar phosphate “head” and non-polar fatty-acid “tails”polar fatty-acid “tails” AmphiphilicAmphiphilic (amphipathic) (amphipathic)

– Make up plasma membranesMake up plasma membranes SteroidsSteroids

– 4 ring structure4 ring structure– Ex) CholesterolEx) Cholesterol

helps provide support in animal cell helps provide support in animal cell membranesmembranes

Start material for other steroids, such Start material for other steroids, such as hormonesas hormones

Categories of Triglycerides Saturated -carbons are

joined by all single bonds (not healthy)

Unsaturated -2 carbons are joined by a double bond

Polyunsaturated -carbons have many double bonds (most healthy)

Self-AssessmentSelf-Assessment

1.1. What property do all lipids share?What property do all lipids share?

2.2. What are the parts of a fat (triglyceride) What are the parts of a fat (triglyceride) molecule?molecule?

3.3. Describe two ways that steroids differ Describe two ways that steroids differ from fats.from fats.

4.4. What does the term “unsaturated fat” on a What does the term “unsaturated fat” on a food label mean? food label mean?

ProteinsProteins A peptide bond is the

covalent bond that joins amino acids

A Polypeptide is a long chain (100+) of amino acids

A (functioning) protein is one or more polypeptide chains precisely coiled, twisted and folded into a unique three-dimensional shape

-Note dehydration synthesis reaction involved in forming a peptide bond.

- How is a peptide bond broken?

ProteinsProteins Contains N,H,C, and O Proteins come from animal foods Examples: (very diverse group)

– Enzymes (biological catalysts)– Structural (hair, connective tissue, such as

ligaments & tendons)– Defensive (antibodies)

Proteins are polymers of Amino Acids– All 20 amino acids are similar except for an

“R” group A proteins amino acid sequence

determines it’s shape which determines its function.

If the shape changes, function is disrupted and protein is denatured.

Structural Levels of a ProteinStructural Levels of a Protein• Primary: sequence of chain

of amino acids• Secondary: AA sequence

linked by H-bonds into an alpha-helix or Beta-pleated sheet

• Tertiary: Attractions between helixes and/or sheets (usually R-groups) lead to further coiling into a 3D shape (globular or fibrous)

• Quaternary: 2+ polypeptide chains (sub-units)

Nucleic AcidsNucleic Acids Large molecules composed of Large molecules composed of

N,H,O, C and P.N,H,O, C and P. The monomers are called The monomers are called

nucleotidesnucleotides Two types of nucleic acids are Two types of nucleic acids are

RNA and DNARNA and DNA DNA: DNA:

Hereditary info: Directions for Hereditary info: Directions for making proteinsmaking proteins

Controls cellular activitiesControls cellular activities RNA:RNA:

Carries out the instructions of DNA Carries out the instructions of DNA to make proteinsto make proteins

DNA & RNA StructureDNA & RNA Structure