the molecules of life chapter 3. the simplest hydrocarbon methane = carbon + hydrogen
TRANSCRIPT
• Thanksgiving dinner: carbohydrates (mashed potatoes); fats (butter/gravy); proteins (meat)
• After finishing a huge Thanksgiving dinner many people feel especially lethargic- many think that turkey makes you sleepy
- is there a biological basis to this claim?
• Turkey meat is high in trytophan- it is converted to serotonin, a chemical that can act on the brain to promote sleep
Biology and Society
Fig 3.1
A Sleep-Inducing Meal
Tryptophan must be taken on an empty stomach to be an effective sleep aid
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
Methane – Simplest Hydrocarbon
The 4 single bonds of C point to the corners of a hydrocarbon
Fig 3.3.
Tetrahedral = 4 triangular sides
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
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
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
Isomers
• Molecules that have the same molecular formula but different structures- because shape is so important minor differences in the arrangement of atoms give isomers different properties
- shape difference gives fructose a taste considerably sweeter than glucose
• In aqueous solutions, monosaccharides form rings
Ring Structure of Glucose
Dissolved in water 1 part of a glucose molecule can bond to
another part to form a ring – reversible process
Fig 3.9