chapter 4:carbon and the molecular diversity of...
TRANSCRIPT
Wilkie
South Fort Myers High School
2015-2016
CHAPTER 4:CARBON AND THE MOLECULAR DIVERSITY OF LIFE
Organic Chemistry:The Chemistry of Carbon• Later in the year you will read an article
that focuses on the origins of life and describes, in more detail, Stanley Miller’s experiment.
• For now let’s go over the basics:• Stanley Miller hypothesized that the
precursors to the more complex macromolecules (nucleic acids, proteins, lipids and carbohydrates) could form under conditions present on the early Earth.
• The experiment used a flask to represent the early ocean and it’s chemical make up.
• Heat vaporized the water where it entered the “atmosphere”, here electrodes simulated lightning.
• The lightning combined the components of Earth’s early atmosphere (CH4=methane, NH3=Ammonia, H2=Hydrogen gas) into simple organic molecules.
• The samples taken for analysis revealed early simple building blocks that could give rise to the more complex macromolecules essential for life.
Carbon Basics• Carbon is the 6th element on the periodic
table.• Since it’s atomic # is 6 carbon contains:
• 6 Protons in the nucleus
• 6 electrons
• 2 in the first orbital ring
• 4 in the second orbital ring-valence shell.
• Since Carbon’s atomic # is 12, we subtract the atomic # from the atomic mass:
• 12-6=6 neutrons in the nucleus.
• The foundation of organic chemistry is based on the emergent properties associated with carbon’s valence electrons.• The organization of carbon’s valence electrons
means it can form 4 bonds with other atoms.
• Because carbon is not so electronegative that it will “steal” electrons from other atoms and isn’t so weakly electronegative that it will give away electrons, carbon forms covalent bonds with most atoms.
• This gives carbon incredible flexibility in forming long complex chains of atoms called hydrocarbons.
Isomers and Isotopes:What’s the difference?• If you recall from my lecture in
chapter 2 we discussed the importance of isotopes in biology.
• An isotope is an atom with same # of protons/electrons as the other forms of that atom, but it has a different atomic mass because it has a different number of neutrons.
• For example carbon 12 an atomic mass of 12, has 6 protons, 6 electrons and 6 neutrons (12-6)
• Carbon 13 has 6 protons has an atomic mass of 13, 6 neutrons and 7 neutrons (13-6)
• An isomer is a molecule that has the same molecular formula but has different structural configurations.
• For example, the chemical above is C5H12.
• In both instances the chemical formula still contains 5 carbon atoms and 12 hydrogen atoms but the two molecules have very different shapes.
What are the different isomers called?• Structural isomers are simple
isomers that differ in structure
• When a double bond exists between atoms, a rotation can occur that can create two unique structures.
• The molecule will rotate around that double bond creating a geometric isomer.
• A molecule that is a mirror image of itself is known as an enatiomer.
What is the biological significance of an isomer?• Form and function go hand in hand
in biology.
• Many biological processes (enzymes, cell signalling, protein synthesis, DNA replication etc.) all depend on molecules with specific structures to do specific functions.
• The first picture to the right illustrates an enatiomers for cell signalling molecules.
• If you notice the slight change in structure (mirror images) the molecule on the left will communicate with target cells because its structure will fit the target cells receptors. The molecule on the right will not fit those receptors and thus will not complete its function…which is to reduce the effects of Parkinson’s disease.
• Are the two molecules to the right isomers?• This is a simplified model of a large organic
compound.
• Every place you see the angle of the shape change represents a carbon atom. Each line to the left and right represents a covalent bond between adjacent carbon atoms.
• Not pictured are the hydrogen atoms that are covalently bonded to the carbon atoms completing the valance shell of the carbon atoms.
• These are not isomers because they do not have the same chemical formula.
• What makes them different?• The branches sticking off of the molecule
represent important groups of atoms known as functional groups.
• As the name implies, these groups can give molecules specific functions because of their chemical properties.
• I will discuss the functional groups in detail in the online lecture.
Summer Assignment Reminder• This concludes the powerpoints for the
summer assignment.
• Hopefully you have been following up each powerpoint by watching the online lectures.
• By now you should have the majority of your directed reading notes completed.
• As I told you in the first lecture, taking detailed notes besides the directed reading notes as part of the lecture process is a good idea to help you ask questions in class.
• Don’t forget to print out a bubble sheet and take the quizzes associated with each chapter.
• I have posted a youtube video up to google classroom from a resource called crash course.• Crash course will be something that I expect
you to utilize as we move forward so it is worth your time to review it over the summer.
• The responsibility falls on you to complete all parts of the summer assignment.
• If you have difficulty with a particular part of the assignment you should contact me and I will get back to you in a few days time.
• Have a safe and enjoyable summer, or if you are a procrastinator and are looking at this a few days before the Fall semester starts…see you in a few days!