Biological Chemistry Review

Transcription

1 Biological Chemistry Review

2 The understanding the basic chemistry of life is vital to a full comprehension of biology.

3 Atom: smallest part of an element that displays the properties of that element made up of 3 subatomic particles.

4 Protons (positively charged) Neutrons (uncharged) in nucleus Electrons (negatively charged) Outside of nucleus

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6 Ions are atoms that have gained or lost electrons Signified by either (+) or ( ) ex. Na+ K+ Cl- Ca2+

7 1. Ionic Bonds Transfer of electrons from a metal (positive ion) to a non-metal (negative ion)

8 Ionic Bonding

9 2. Covalent Bonds Atoms share e-s Between 2 non-metals ay/periodictable/covalentbond.shtml - covalent bonds Water Story (1:36)

10 Covalent Bonding single covalent bond (sharing 2 e-) double covalent bond (sharing 4 e-) Can have triple covalent bond (share 6 e-)

11 Nonpolar covalent bonds electrons shared fairly equally between atoms

12 Polar Covalent Bonds = Unequal sharing of electrons Creates a dipole (slight positive end & slight negative end)

13 Compound formulas

14 Shape of Molecules

15 = when H covalently bonds with one atom, which is also attracted to another atom (usually O, N or F) of a different molecule Always represented by dotted lines

16 If you need more Chemistry section MIT courseware Highlights for High School Biology Chemistry of Life Organic Molecules in Organisms

17 Goal (PLO B2 & B3) Inorganic Compounds 1. Salts 2. Water 3. Acids/bases, ph, buffers

18 Inorganic compounds Organic Compound Usually metal + non-metal Always contain carbon and hydrogen Usually ionic bonding Always covalent bonding Associated with non-living Associated with living things Ex. salts, water, acids, bases, Ex. carbohydrates, lipids, buffers nucleic acids, and proteins

19 1. Salts Needed for survival Too little fatigue, exhaustion, cramps, nausea, thirst, decreases blood pressure and even death Too much dehydration of cells and hypertension; can lead to heart attack

20 Water (cont d) Structure of water: Biological function/importance is due to its chemical structure Water is a polar molecule How does polarity of H2O produce H-bonding?

21 Oxygen is bigger & negatively charged H is smaller & positively charged oxygen pulls the electrons toward it creating a dipole O slightly more negative ( e- time) H slightly more positive ( e- time) = POLAR COMPOUND

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23 In a H-bond: H (positive dipole) of one H2O attracted to O (negative dipole) of different H2O molecules** H-bonding can occur between the H and other polar compounds

24 Special properties of H2O 1. temperature regulator H2O has a high specific heat capacity Means takes a lot of energy to increase temp of H2O and loses energy slowly Keeps our body temp constant Water vaporization much heat energy released (sweating) High melting & boiling points

25 2. Acts as a solvent When Polar substances (ie salts, sugars, some proteins) are added to water, oxygen (-) attracts positive end of solute & H (+) attracts negative of solute thus pulling the substances apart H2O acts as a solvent e.g. NaCl dissolves into Na+ & Cl- in water

26 3. Acts as a lubricant In mouth, joints, lungs, etc. In lungs CO2 & O2 only diffuse across moist membranes

27 4. Water has a high surface tension This allows some insects to walk on the surface of a pond or lake.

28 Use p (9 ed.) th What is an acid? Write the equation. What is a base? Write the equation. What does water dissociate into? Give a definition for a neutral substance? (think about this one it is not in the text) 5. What is meant by ph? 6. What is the ph scale?

29 Acids and Bases When water ionizes, it releases an equal number of hydrogen ions (H+) and hydroxide ions (OH-).

30 H 2O H+ and OH-

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32 Neutral solutions: Equal amounts of H+ and OH acid + base water + salt e.g. HCl + NaOH H2O + NaCl

33 The ph Scale (proportion of H ions) Measures acidity & alkalinity (basicity) of a solution Ranges from 0-14 A ph below 7 is acidic [H+] > [OH-] A ph above 7 is alkaline [OH-] > [H+] A ph of 7 is neutral [H+] = [OH-]

34 [ H+ ] ph is the concentration of expressed as a logarithm. Every change in the ph scale of one unit 10 is a change in times the concentration of H+.

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36 To determine ph from a diagram, only pay attention to the OH- and H+ if there are more H+ = acidic if there are more OH- = basic if there is an equal number of OH- and H+ = neutral

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38 Buffers A buffer is a chemical(s) that can resist changes in ph living organisms need to maintain a constant ph level because the chemical processes are sensitive to changes in H+ and OH We have a built in system to maintain our internal ph (homeostasis)

39 Buffers function by taking up excess H+ or OH- to help keep ph constant

40 In a strong acid solution, there are too many hydrogen ions. ions So, if we add a strong acid to a solution with a buffer, the buffer is attracted to the hydrogen ions. So the buffer (example: CO32-) will react with the H+ to form (in this case) HCO3-. H+ + CO32- HCO3- Therefore, the H+ gets absorbed by the buffer and the ph of the solution does not change. change When it is in an ACIDIC solution, a buffer will absorb H+ ions.

41 In a strong base solution, there are too many hydroxide ions. ions So if we add a strong base to a solution with a buffer, the buffer (example: H2CO3) will give up its H+ in order to transform the base (OH-) into water (H2O), also written as H(OH). Because the buffer has lost a H+, it will become HCO31-. OH- + H2CO3 H(OH) + HCO31- Therefore, the OH- gets turned into water and the ph of the solution does not change. change When it is in an BASIC solution, a buffer will donate/release H+ ions.

42 A buffer usually has 3 (or more) versions of itself. In the case we just looked at, the buffer could either be : H2CO3 HCO31-

43 Buffers (cont d) buffers only work until all the ions are gone They are not permanent Why do we talk about this? Important in our cells and blood E.g bicarbonate in blood most important buffer