UNIT 1 NOTES Biological Chemistry Review

Transcription

1 UNIT 1 NOTES Biological Chemistry Review Why study Chemistry in Biology? The understanding of the basic chemistry of life is vital to a full comprehension of biology. Important atoms include: o Oxygen (O) o Phosphorous (P) o Carbon (C ) o Potassium (K) o Hydrogen (H) o Sulphur (S) o Nitrogen (N) Atoms: Atom = smallest part of an element that displays the properties of that element - Made up of 3 subatomic particles: o Protons (positively charged) Found in the nucleus o Neutrons (uncharged / neutral) o Electrons (negatively charged) found outside of the nucleus Ions: Ions = atoms that have gained or lost electrons - Signified by either (+) or (-) - Ex. Na +, K +, Cl -, Ca 2+ Types of bonding: 1. Ionic bonds: - Transfer of electrons from a metal (positive ion) to a non-metal (negative ion) 2. Covalent bonds: - Atoms share electrons between 2 non-metals - Can be single covalent bond (sharing 2 electrons), double covalent bond (sharing 4 electrons) or triple covalent bond (sharing 6 electrons) o o Nonpolar covalent bonds - Electrons shared fairly equally between atoms Polar covalent bonds - Unequal sharing of electrons 3. Hydrogen bonds: - When a covalently bonded H within a molecule (eg H 2 O) is also attracted to another atom (usually O, N or F) of a different molecule. - Always represented by dotted lines Inorganic Compounds: Inorganic Compounds Usually metal + non-metal Usually ionic bonding Associated with non-living Ex. Salts, water, acids, bases, buffers Organic Compounds Always contain carbon and hydrogen Always covalent bonding Associated with living things Ex. Carbohydrates, lipids, proteins and nucleic acids A. Salts: - Needed for survival - Too little fatigue, exhaustion, cramps, nausea, thirst, decrease in blood pressure and even death - Too much dehydration of cells and hypertension; can lead to heart attack B. Water: Structure of water: - Biological importance is due to its chemical structure - Water is a polar molecule o How does polarity of water produce H-bonding? Oxygen is bigger & negatively charged H is smaller & positively charged

2 Oxygen pulls the electrons toward it creating a dipole O is slightly more negative symbolized as - (electrons spend more time around the oxygen) H is slightly more positive symbolized as + (electrons spend less time around the hydrogen) = polar compound In a H-bond: o H (positive dipole) of one water attracted to O (negative dipole) of different water molecules o H-bonding can occur between the H and other polar compounds 4 Special Properties of Water: 1) Temperature regulator: Ø Water has a high specific heat capacity o Means takes a lot of energy to increase temperature of water and loses energy slowly Ø Keeps our body temperature constant o Water vaporization much heat energy released (sweating) Ø High melting & boiling points 2) Acts as a solvent: Ø 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 o Water acts as a solvent o Eg. NaCl dissolves into Na + & Cl - in water 3) Acts as a lubricant: Ø In mouth, joints, lungs, etc. o In lungs CO 2 & O 2 only diffuse across moist membranes 4) Water has a high surface tension: Ø This allows some insects to walk on the surface of a pond or lake C. Acids / bases/ buffers: Acids and bases: Ø When water ionizes, it releases an equal number of hydrogen ions (H + ) and hydroxide ions (OH - ) o H 2 O H + + OH - Ø Acids release H + ions into the solution o HCl H + + Cl - Ø Bases remove H + ions from the solution o NaOH Na + + OH - Ø Neutral solutions: o Equal amounts of H + and OH - o Neutralization reaction: Acid + base water + salt Eg. HCl + NaOH H 2 O + NaCl ph scale: The ph scale (proportion of H ions) Ø Measures acidity & alkalinity (basicity) of a solution Ø Ranges from 0 14 o A ph below 7 is acidic [H + ] > [OH - ] o A ph above 7 is alkaline [OH - ] > [H + ] o A ph of 7 is neutral [H + ] = [OH - ] Ø ph is the concentration of [H + ] expressed as a logarithm. Every change in the ph scale of one unit is a change in 10 times the concentration of H + Ø To determine ph from a diagram, only pay attention to the OH - and H + o If there are more H +, solution is acidic o If there are more OH -, solution is basic o If there is an equal number of OH - and H +, solution is neutral Why is it important to maintain ph? Ø The ph of most living systems is between ph 6-8. Maintaining the proper ph then is vital for living systems. Ø Living organisms maintain a proper ph balance by using the homeostatic control of buffers.

3 Buffers: Ø A buffer is a chemical(s) that can resist changes in ph Ø Living organisms internal chemical processes are sensitive to changes in H + and OH -. Examples: o Stomach ph = o Blood ph = 7.4 or get sick (most important buffer is bicarbonate HCO 3 - ) o Small intestine ph ~8.3 Ø We have a built in system to maintain our internal ph (homeostasis) via natural buffers Ø Buffers function by taking up excess H + or OH - to help keep ph constant À In a strong acid solution, there are too many hydrogen ions o if we add a strong acid to a buffered solution, the buffer is attracted to the hydrogen ions so that the ph does of the solution does not change In an acidic solution, the buffer will absorb the H + À In a strong base solution, there are too many hydroxide ions o if we add a strong base to a buffered solution, the buffer will give up H + in order to combine with OH - of the base to produce water (H 2 O). H + + OH - H 2 O Ø Therefore,the ph of the solution does not change o In a basic solution, a buffer will donate / release H + ions to neutralize the OH - Ø Buffers only work until all the ions are gone meaning they are not permanent Important Organic Compounds: Biological Molecules The most important biological compounds are polymers POLYMERS (poly = many) The polymers are proteins, carbohydrates, lipids (fats), and nucleic acids (DNA / RNA) A polymer is made up of a chain of many monomers linked together Large polymers are also called macromolecules MONOMERS (mono = one) Monomers are: amino acids, sugars, fatty acids, and nucleotides These are made or broken down over and over in living cells MONOMER (building block) POLYMER (Biological organic molecule) Monosaccharide (glucose) Carbohydrate Glycerol and fatty acid Lipid (fat) Amino acid Protein Nucleotide Nucleic acid Examples: Monomer è H - - OH (one block) Polymer è H OH (many blocks) Process to build polymers Dehydration synthesis: covalently bonding monomers together by removing water o Chains of monomers are called polymers Looks like. H - - OH + H - - OH H OH + H 2 O (monomer) (monomer) (dimer) (water) H OH + H OH H OH + H 2 0 (dimer) (dimer) (polymer) (water) To break apart polymers Hydrolysis: Add H 2 O for every covalent bond that needs to be broken H OH + 3 H H - - OH 1 H 2 O will be consumed for every 1 covalent bond to be broken

4 Organic Molecules: 1. Carbohydrates (simple and complex sugars) 2. Lipids (Fats) 3. Proteins 4. Nucleic Acids **reminder: organic molecules always contains C & H & covalent bonds 1. Carbohydrates (simple sugars and complex carbohydrates) Where does the name come from? Hydrated carbons: (CH 2 O) n C = carb ; H 2 O = hydrate Carbohydrates have the empirical formula of (CH 2 O) n o Where n = the number of times the chain is repeated The carbons, hydrogens and oxygens are found in the ratio of 1:2:1 and are made up of a repeating chain of sugars. Ie. (CH 2 O) 3 = C 3 H 6 O 3 ie glucose = (CH 2 O) 6 or C 6 H 12 O 6 in a ring shape o sugars are also known as saccharides o carbohydrates usually end in ose a) Monosaccharides (simple sugars) basic sugar molecule is GLUCOSE - C 6 H 12 O 6 glucose has a ring structure other monosaccharides include fructose, ribose, deoxyribose b) Disaccharides (simple sugars) When two monosaccharides bind together via dehydration synthesis (water lost) glucose Examples: glucose + glucose = maltose + water glucose + galactose = lactose (milk sugar) + water glucose + fructose = sucrose (table sugar) + water C 12 H c) Polysaccharides (complex carbohydrates) Polymer of identical monosaccharides (typically glucose) Examples: i. Starch ii. Glycogen iii. Cellulose i. Starch Function: Storage form of glucose in plants (long glucose chains) Structure: Few or no side chains branches Sugars produced by photosynthesis are stored as starch (in leaves, stems, roots) until needed maltose ii. Glycogen Function: Animals store their energy (extra glucose) as glycogen in the liver and muscles Structure: Long chains of glucose with many side chains

5 iii. Cellulose Function: Cell walls of plants are made of cellulose to give it strength Structure: Long chains of glucose with no side chains and have alternating position of linking oxygen atoms No mammals can break the bond (indigestible) however, important for digestive system as it serves as fibre Carbohydrate review Source Monomer Polymer Characteristic Animal Glucose Glycogen Highly branched Plant Glucose Starch No (or few) branches Cellulose Alternating O bonds Functions: Energy for cells Energy storage (starch, glycogen) Cell recognition role = glycoprotein or glycolipid o For example: the basis for A, B, and O blood groups 2. Lipids Characteristics: made up of C, H, O (sometimes P or N) large, insoluble (in water) molecules Ex. Water in oil 2 monomers: Glycerol Fatty acids (long hydrocarbon chains) 3 types of Lipids: A. Triglycerides aka neutral fats (nonpolar) or fats and oils Structure: E shaped molecule made of one glycerol and 3 fatty acids synthesized by dehydration of 3 H 2 O molecules Fatty acids are hydrocarbon chains with COOH end glycerol 3 main types of fatty acid 1. Saturated no C=C which means it is full of H, fairly straight, solid at room temp, fat (from animals) 2. Unsaturated at least one C=C bond, structurally bent, liquid at room temp., oil (from plants) 3. Polyunsaturated many C=C bonds so few H s (e.g veggie oils) µ Important - hydrogenation adds H s (margarine or shortening) but forms trans fats L 2 Types of triglycerides (due to different fatty acids): a) Fats= animal based & solid (eg. butter, lard) functions: 1. Long term energy source 2. Cushions organs 3. Insulation b) Oil = plant based & liquid (eg. olive, corn, etc) Main energy source for plants B. Phospholipids (2 nd type of lipid) o Comprised of 1 glycerol, 1 phosphate group & 2 fatty acids o think of a triglyceride except one fatty acid has been replace by a phosphate group o Primary components of cellular membranes

6 Phospholipid bilayer when placed in H 2 O, phospholipids form 2 layers the polar heads (hydrophilic) face out and the non-polar tails (hydrophobic) face in Diagram: C. Steroids (3 rd type of lipid) Structure: 4 fused rings of carbon with stuff attached (called functional groups) all made of cholesterol (a steroid) eg. Testosterone, estrogen, cholesterol and vitamin D Non-polar so can easily pass through cell membranes Are water insoluble (it is a lipid) Function: Used as sex hormone (e.g. estrogen & testosterone) Emulsification Needed to mix fats/oils into water e.g. soap and bile (produced by gallbladder) 3. Proteins Functions in cells. Structural strength and support Enzymes- speed up chemical reactions Hormones chemical messages in body Antibodies provides immunity Transport in blood and across cell membranes Contraction muscle movement (eg. actin & myosin) Protein Structure: Monomer = amino acid (symbolized by aa) Made up of C, H, O, and N (but not in a set ratio like carbs were) R-groups / side chains: 20 different R-groups for 20 different AA s Peptides o A peptide bond joins amino acids (a dipeptide) between C and N and one water is lost o A polypeptide is a chain of amino acids o Another name for a polypeptide is protein

7 Protein Structure is due to folding and bonding: 4 types of structures: i. Primary (1 ) protein ii. Secondary (2 ) protein iii. Tertiary (3 ) protein iv. Quaternary (4 ) protein o i. Primary (1 ) Protein Single chain of aa s in linear form Held together by peptide bonds only ii. Secondary (2 ) Protein H-bonding within polypeptide pulls 1 into alpha-helix or pleated sheet Held together by Hydrogen & peptide bonds iii. Tertiary (3 ) Protein Covalent bonding between R-groups pulls coil into tertiary shape Held together by covalent, hydrogen & peptides bonds iv. Quaternary (4 ) Protein 2 or more peptides ionically bonded together ( blobs ) Held together by covalent, hydrogen, peptide& ionic bonds Why is the shape of a protein so important? The shape of each individual protein is specific to its function; therefore, without the proper shape, it will not function Eg. if folding does not occur correctly, it can cause diseases such as Parkinson s or Alzheimer s Denaturation is the disruption of the shape of a protein & therefore, a loss of function is caused by exposure to high temp., ph, chemicals & heavy metals 4. Nucleic Acids À Monomer = nucleotide which is composed of: o Phosphate o Pentose sugar (5 carbon) o Nitrogen-containing base À Polymers of Nucleic Acids a) DNA (deoxyribonucleic acid) DNA nucleotide has: Sugar (deoxyribose), phosphate & one of 4 bases [adenine (A), thymine (T), cytosine (C), & guanine (G)] DNA is double stranded: 2 linear strands held together by H-bonds between the bases o A with T and C with G DNA twists into a double helix Always has phosphate-sugar backbone *different number & arrangements of N-bases provides variety in genetic information Function: Directs and controls all cell activities b) RNA (ribonucleic acid) Single stranded (no helix) Ribose sugar (not deoxyribose) Has Uracil (U) instead of thymine (T) 3 types of RNA needed to make proteins (discussed later)

8 DNA Structure vs RNA structure comparison table DNA Sugar Deoxyribose Bases Strands Helix adenine, guanine, cytosine, thymine RNA Ribose adenine, guanine, cytosine, uracil 2 double 1 - single Yes No c) ATP (Adenosine Triphosphate) Function: Provides energy for cells Produced during cellular respiration in the mitochondria (an organelle) Structure: Adenosine & 3 phosphate groups Adenine (a base) + ribose (a sugar) = adenosine Energy-rich bond between the 2 nd & 3 rd which when broken releases a large amount of energy ATP ADP + + energy Functions of nucleic acid polymers summary: DNA stores genetic information and codes for proteins. RNA helps make proteins ATP is the energy currency in cells 3 phosphates + ribose sugar + adenine = ATP!