The Molecules of Life

Chapter 3

The Simplest Hydrocarbon

• Methane = Carbon + Hydrogen

Organic Molecules

• A cell is mostly water but the rest consists mainly of carbon based molecules

• Compounds that contain carbon are called organic compounds

• Carbon has the ability to form the large, complex diverse, molecules necessary for life functions

• Why are carbon atoms so versatile as molecular ingredients?

Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings

Carbon Chemistry

• Carbon a versatile atom has 4 electrons in an outer shell that holds 8- carbon can share its electrons with other atoms to form up to 4 covalent bonds

• Carbon can use its bonds to attach to other carbons

to form an endless diversity of carbon skeletons- each carbon in an organic molecule can branch off in up to 4 directions

• Carbon atoms of organic molecules can also bond with other elements (hydrogen, oxygen, nitrogen)

Variations in Carbon Skeletons

• Simplest organic compounds are hydrocarbons• Hydrocarbons consist of carbon and hydrogen• Each C atom forms 4 bonds; each H atom forms 1 bond

Fig 3.2

Larger Hydrocarbons

• Main molecules in the gasoline we burn in our cars

• Hydrocarbons of fat molecules provide energy for our bodies

Fig 3.4

Functional Groups

• Each type of organic molecule has a unique 3-dimensional shape that defines its function in an organism- the molecules of your body recognize one another based on their shapes

• The unique properties of an organic compound depend not only on its carbon skeleton but also on the atoms attached to the skeleton- these atoms are called functional groups

• Functional groups behave consistently from one organic molecule to another

4 Important Functional Groups

• Many biological molecules have 2 or more functional groups• How do cells make large molecules out of smaller organic molecules

Size of Molecules• Monomers

– Molecules used as subunits to

build larger molecules (polymers)

• Polymers– Larger molecules that are chains of

monomers– May be split and used for energy

Building Blocks

• On a molecular scale, many of life’s molecules are gigantic- biologists call them macromolecules (macro = ‘big’) such as DNA, carbohydrates, proteins

• Most macromolecules are polymers- polymers are made by stringing together many smaller molecules called monomers- cells link monomers together through a dehydration reaction (removes a molecule of water)

• Organisms break down macromolecules (digestion)- cells do this by a process called hydrolysis (hydro = ‘water’ lyse = ‘break’; to break with water)

Dehydration Reaction

Synthesis – a polymer grows in length when an incoming monomer and the monomer at the end of the existing chain contribute to the formation of a water molecule, the monomers then replace their lost covalent bonds with a bond to each other

Hydrolysis

Breaking a polymer chain – hydrolysis reverses the process by

breaking down the polymer with the addition of water molecules, which

break the bonds between monomers

Biological Molecules

There are 4 categories of large molecules in cells:

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Carbon-Carbon Macromolecules

• Aka: Organic Molecules

• Fall into 4 groupings:

Carbohydrates

Lipids

Proteins

Nucleic Acids

Carbohydrates

• ‘Carbs’ - from small sugar molecules in soft drinks to long starch molecules in pasta and potatoes- serve as a primary source of dietary energy

- used as building material to form the body of a plant

• Monosaccharides (mono = ‘one’, and sacchar = ‘sugar’) are simple sugars:- glucose found in sports drinks

- fructose found in fruits

• Monosaccharides glucose and fructose are isomers - they have the same molecular formula, but their atoms are arranged differently

Glucose

• Monosaccharides, particularly glucose, are the main fuel that cells use for cellular work

• Cells break down glucose molecules and extract their stored energy

- give off CO2 as waste

• Monosaccharides also provide cells with carbon skeletons that can be used as raw material

Polysaccharides

• Long repeating chains of monosaccharides

• Often used for Energy storage

• Animals form Glycogen from glucose units

• Stored in Liver and muscles

• Plants also store glucose polysaccarides

• Starch

Carbohydrate Complexity

• Monosaccharides: useable Energy

• Disaccharides: transport form

• Polysaccharides: Storage and structural forms

Lipids:Fats & Oils

• Insoluble in water, but soluble in oil• Examples include:

Oils (olive, corn…)

Waxes (bee’s, ear)

Fats• Lipids have two ends.• Hydrophilic – water loving head• Hydrophobic – water fearing tail

Other Lipids

• Phospholipids… important in cell membranes

• Steroids… testosterone, cholesterol, hormones

Proteins

• Contain C, H, O, N, sometimes P and S

• Polymers of amino acids

• Functions: Basis of Protein hormones (eg., insulin, growth hormone), structural components of muscle (actin and myosin), & skin (collagen & keratin), antibodies (immunoglobulins), transport molecules (hemoglobin), cell surface receptors and channels, enzymes, pigments

Proteins

• Make up skin and muscles.

• Used as catalysts in the form of enzymes.

• Amino acids (monomers) are linked together to form peptides.

Protein Structure

Nucleic Acids (RNA and DNA)

• Polymers of nucleotides

• A single nucleotide:

• Carry and transmit hereditary information

• Direct the synthesis of proteins

Adenine, guanine, thymine, cytosine or uracil (RNA only)

Got all that?

• Knight Starts Monday.• Check wall for room assignment.• Unit 1 test next Friday!!!! Covers

EVERYTHING since beginning of year. Review all notes and vocabulary.

• Characteristics of life.• Scientific Method• Chemistry.• Molecules of life.