chapter 2 lecture notes

chapter 2 lecture notes - Cell and Molecular Biology...

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Cell and Molecular Biology Chemical components of cells Today, we will discuss the different molecules of cells and the chemical bonds that hold these molecules together. So, today, we’ll be reviewing things that you should already have had several times in the past; bonds, carbons, associations with water, etc. Living organisms are governed by the laws of chemistry and physics. However, the chemistry of living organisms is special in that it deals with organic compounds or carbon compounds. This is called organic chemistry. You should have already taken organic chemisty prior to this class- or, at the very least, you should be taking it right now. Chemistry of living organisms 1. organic- carbon compounds 2. reactions take place in aqueous solution 3. reactions take place in a narrow temp range 4. complex 5. dominated by large polymers (DNA, proteins, etc.) chains of molecules linked end to end. This is review (not covered in detail in class). Please make sure you understand the different bonds (covalent, ionic, hydrogen, etc). Chemical bonds- Matter is made of elements- ex, hydrogen, carbon and oxygen (there are 92 naturallly occuring elements). Elements are substances that may not be broken down or changed by chemical means. Living organisms use only a small number of elements: C,O, H, N, S and P constitute ~99% of the organic molecules/water in living organisms. Living organisms also contain small (Na, Ca, Mg, K) or trace amounts of other elements (Fe, Zn, Cl, I , Cr, Cu, Se, Mn). The smallest particle of an element is an atom. Atoms are made from protons (+), electrons (-), and neutrons (not charged). Atoms are linked together to form molecules and the way that they are linked together in groups determines the characteristics of the molecule. So, it’s important to understand chemical bonds. Atoms have a dense, centrally located nucleus- positively charged- contains most of the atom’s mass. This nucleus contains protons and neutrons. The nucleus is surrounded by a much less dense cloud of negatively charged electrons. The electrons move rapidly about the nucleus. Atomic # = # of protons (Hydrogen has 1 proton so atomic # = 1; carbon has 6 protons)
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Each atom has the same number of electrons as protons so overall charge is neutral (the charge carried by the protons is exactly equal and opposite to the charge carried by the electrons). All atoms of a given element have the same atomic # - this # determines the chemical behavior of the element. Atom weight = protons + neutrons (variation in neutrons in an element = isotopes) Ex Carbon 12- stable isotope (6 protons, 6 neutrons), carbon 14 is unstable (6 protons, 8 neutrons) so it decays The mass of atoms or molecules is often measured in daltons. 1 dalton = mass of one H atom. 1 proton or neutron weighs about 1/(6 x 10
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chapter 2 lecture notes - Cell and Molecular Biology...

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