Class Notes (809,497)
Canada (493,753)
Biology (1,278)
BIOL 102 (194)

Chapter 3 Biology Summary

20 Pages
Unlock Document

Queen's University
BIOL 102
Wayne Snedden

CHAPTER 3 ORGANIC MOLECULES SUMMARY NOTES Carbon • Carbon has 4 electrons in its outer shell (2s orbital is filled with 2 electrons and other energy or- bitals in the second energy level contain either one or 0 electrons) • Therefore C needs 4 more electrons to fill the shell so it can make up to 4 bonds (usually single or double bonds) • Carbon can form nonpolar and polar bonds •Molecules with nonpolar bonds (like hydrocarbons) are poorly water soluble •Molecules with polar bonds are more water soluble -in solution (at a neutral pH) H+ leaves the carbonyl group; most organic acids are highly dissoci- ated Functional Groups • Groups of atoms with special chemical features that are functionally impor- tant • Each type of functional group exhibits the same properties in all molecules in which it occurs Isomers • identical molecular formula but different structures and characteristics • Structural isomers- contain the same atoms but in different bonding relationships • Stereoisomers- identical bonding relationships, but the spatial positioning of the atoms differs in the two isomers; 2 types of stereoisomers are: • geometric isomers– have different positioning around double bond • the 'cis' isomer has both of the same adjoining groups on the same side of the double bond; the 'trans' isomer has both of the same adjoining groups on opposite sides of the double bond • there is no free rotation around the carbon-carbon double bond (like there is around a sin- gle bond) so the stereoposition of the molecule is fixed • enantiomers- non-superimposable mirror image of another molecule isomers are important because some enzymes will attack/ react with certain isotopes but not oth- • ers Four major bio-organic macromolecules 1. Carbohydrates 2. Lipids 3. Proteins 4. NucleicAcids Carbohydrates • Composed of CHO: C (HnO) n • Most of the carbon atoms in a carbohydrate are linked to a hydrogen atom and a hydroxyl group Monosaccharides: Simplest sugars • • Most common are 5 or 6 carbons • Pentoses (5C)- ribose (C5H10O5), deoxyribose(C5H10O4) • Hexose- glucose (C6H12O6) (used by he body for energy) • Different ways to depict structures: linear and ring (the 'real' structure of monosaccharides in so- lution) (a) A comparison of the linear and ring structures of glucose. In solution, such as the fluids of organisms, nearly all glucose is in the ring form. (b) Isomers of glu- cose. Glucose exists as stereoisomers designated α- and β-glucose, which differ in the position of the OH group attached to carbon atom number 1. Glucose and galactose differ in the position of the OH group attached to carbon atom number 4. Enantiomers of glucose, called D-glucose and L-glucose, are mirror images of each other. D-glucose is the form that is used by living cells. Note: The letters D and L are derived from dextrorotatory (rotating to the right) and levorotatory (rotat- ing to the left). • Disaccharides: composed of two monosaccharides via dehydration (condensa- tion) reaction which forms a glycosidic bond between the two monomers • Broken apart by hydrolysis • Examples -sucrose,(made by plants),maltose, lactose Formation of a disaccharide. Two monosaccharides can bond to each other to form a disaccharide. Shown here, the first carbon of α-glucose is bonded with fructose to create sucrose, through a dehydration reaction. • Polysaccharides: many monosaccharides linked together to form long polymers • Examples • Energy storage: starch (plants) and glycogen (animals) • composed of thousands of α-D- glucose molecules linked by α-glycosidic linkages into long branched chains (differing in the extent of branching) • Both branched polysaccharides can readily have individual glucose molecules removed by hy- drolysis, providing an efficient means of storing energy. But a higher degree of branching in glyco- gen contributes to its solubility in animal tissues, making it easily available to muscle tissue. Structural role – cellulose, chitin, glycosaminoglycans • • cellulose is a polymer of β-glucose held by β-glycosidic linkages in a linear arrangement of carbon–carbon bonds • unbranched linear fibres of adjacent cellulose molecules can form hydrogen bonds between the multiple hydroxyl groups on the glucose molecules of one chain and the oxygen molecules on a neighbouring chain to hold cellulose fibres firmly together giving cellulose high tensile strength Lipids • Composed predominantly of H & C • non-polar and insoluble in water • examples: fats, phospholipids, steroids Fats • Mixture of triglycerides (aka) triacylglycerols • Formed by bonding glycerol to three fatty acids • Joined by dehydration, broken via hydrolysis • great for energy storage (1 gram of fat stores twice as much energy as 1 gram of carbohydrates because it contains more energy-rich bonds) • Fats can also be structural in providing cushioning and insulation -The formation of a triglyceride requires three dehydration reactions in which fatty acids are bond- ed to glycerol. Fatty acids -saturated fats: all carbons are linked by single covalent bonds • Tend to be solid at room temperature • Unsaturated fats: contain one or more double bonds • 1 double bond- monounsaturated • 2 or more – polyunsaturated • Tend to be liquids at room temperature (oils) • The double bonds of unsaturated fats create bends in the structure. The trans configuration of the double bonds in trans fats and the set of single bonds of saturated fats create straight hydrocarbon tails. • Enzymes in our bodies are not good at attacking the trans-bond in unsaturated fatty acids but they can react with the cis bond At low temperatures phospholipid bilayer membranes can solidify (become less fluid) unless • membrane is modified to include cis-bonds (increases number of kinks therefore increases fluidity) Phospholipids (found in plasma membrane) • Consist of glycerol, 2 fatty acids and a phosphate group •Amphipathic molecule: Head region is polar and hydrophilic while fatty acid chains are non-polar and hydrophobic • Important in membrane structure and signaling Steroids • Four interconnected rings of carbon atoms • Usually not very water soluble (predominantly hydrophobic C-H bonds) therefore they usually need carriers to move through the cell • examples: • Cholesterol • Estrogen and testosterone; these molecules differ only slightly therefore receptors must be able to distinguish between them Proteins • Composed of COHN, some S, often modified • Machines of the cell •Amino acids are the monomers – Common structure with variable R-group – 20 L-amino acids (the L-isomer is used in proteins) – Side-chain determines structure and function Major Categories and Functions of Proteins Category Functions Examples Proteins in- Control produc- RNA polymerases use DNA as a template to volved in gene tion of nucleic make RNA; transcription factor proteins regulate replication, ex- acids and RNA polymerase access to genes pression, and polypeptides regulation Motor proteins Initiate move- Myosin is a motor protein that provides the con- ment tractile force of muscles; kinesin is a key protein that helps cells to sort their chromosomes Defence pro- Protect organ- Antibodies ward off infection caused by bacteria teins isms against or viruses disease Metabolic en- Increase rates Hexokinase is an enzyme involved in sugar me- zymes of chemical re- tabolism
More Less

Related notes for BIOL 102

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.