1. The Structure and Function of Large Biological Molecules
Chapter 5

2. Macromolecules
Macromolecules (or polymers) are long, chain-like molecules
Consists of many similar or identical building blocks (monomers) linked by covalent bonds
Includes carbohydrates, nucleic acids, and proteins
Lipids are not a true macromolecule
Built via condensation or dehydration reaction (or dehydration synthesis)
Take away water molecule
Helped by enzymes to speed reaction
Breakdown via hydrolysis
Add water molecule
Occurs in digestion

3. Carbohydrates Monomers: monosaccharides or simple sugars
Simplified formula is CH2O
Structure is used to classify sugars
General structure includes a carbonyl group and multiple hydroxyl groups
Location of carbonyl will determine if it is aldose or ketose (aldehyde or ketone sugars)
Sugars are made up of 3-7 carbons in skeleton which may be linear or ringed
Spatial arrangement around asymmetric carbons is important
Examples: glucose, fructose, galactose
Important in cellular respiration and synthesis of materials

4. Carbohydrates Disaccharides: 2 sugars joined by a covalent bond
The covalent bond is known as a glycosidic linkage when it is between 2 monosaccharides
The bond is formed by dehydration reaction
Examples: Maltose, sucrose, lactose

5. Carbohydrates
Polymers: polysaccharides; these are macromolecules also formed via glycosidic linkages
Storage polysaccharides
Starch – polymer of glucose monomers found in plants; starch allows plants to stockpile glucose
α configuration of glucose
Humans consume these in potatoes and grains
Glycogen – a branched polymer of glucose found in most vertebrates; largely stored in liver and muscle cells and is released when the body needs sugar

6. Carbohydrates Structural Polysaccharides
Cellulose – major component in cell walls
β configuration of glucose (every other glucose monomer in upside down)
Important in digestion – humans do not have the appropriate enzymes to digest β linkages, but promotes healthy digestion
Most abundant organic compound on Earth
Chitin – used by arthropods in exoskeletons
Similar structure to cellulose, but contains nitrogen

7. Lipids
Lipids do not include true polymers and are not generally considered macromolecules
They are grouped together because they are hydrophobic
Largely composed of hydrocarbons
Includes: fats, phospholipids, steroids, waxes and pigments

8. Lipids
Fats (triacylglycerol or triglyceride) – composed of glycerol attached to 3 fatty acids bonded via an ester linkage
Ester linkage occurs between hydroxyl and carboxyl groups
Glycerol – alcohol with 3 carbons each with its own hydroxyl group
Fatty acid – long carbon skeleton (16-18 common) with one carbon end associated with a carboxyl group. The rest is a long hydrocarbon chain.
Important in energy storage and protection

9. Lipids Fats Saturated fat or fatty acid Unsaturated fat or fatty acid
No double bonds which allows the greatest number of hydrogens to be attached to the carbon skeleton
Includes most animal fats
Solid at room temp
Unsaturated fat or fatty acid
Has 1 or more double bonds and thus fewer hydrogen atoms
A kink in the chain will occur whenever a cis double bond occurs (as opposed to trans double bonds – ie trans fats found in hydrogenated veg. oil)
Includes plant and fish oils
Liquid at room temp

10. Lipids Phospholipids – essential for cell membrane composition
Similar to fat molecule, but only have 2 fatty acids attached to glycerol
The 3rd hydroxyl group is attached to a phosphate group (these can in turn bond to other molecules)
Hydrocarbon tail is hydrophobic (inside the bilayer), phosphate group is hydrophilic (face outward)

11. Lipids
Steroids – carbon skeleton composed of 4 fused rings with different chemical groups attached
Includes many hormones and cholesterol
Fat can affect cholesterol levels

12. Proteins
Proteins account for ~50% of cell’s dry mass and extremely important in functions

13. Proteins Monomers are amino acids Polymers are polypeptides
20 different amino acids that are composed of an asymmetric carbon surrounded by an amino group, carboxyl group, hydrogen and an R group or side chain which varies
Polymers are polypeptides
Different combinations of A.A. allows for the variety of proteins
A.A. are attached with a covalent bond between the carboxyl group of one to the amino group of another called a peptide bond

14. Proteins Protein structure and function are intimately linked
The specific folds of a protein are determined by the ordering of A.A. in the polypeptide chain. This folding in turn determines shape.
Shape will then determine function.

15. Proteins Primary Structure – the unique sequence of amino acids
Secondary Structure – coils and folds in the polypeptide chain caused by hydrogen bonds between repeating constituents
α helix – a coil held together by hydrogen bonds at every 4th A.A.
β pleated sheet – folding creating pleats at particular intervals

16. Proteins
Tertiary Structure – Overall shape of a polypeptide due to interactions of R groups
Shape may be reinforced by disulfide bridges
Covalent bond between sulfhydryl groups
Quaternary Structure – overall protein structure (potentially several polypeptide chains interacting)

17. Proteins
Changes in primary structure lead to changes in further structures, potentially leads to a misfunctioning or nonfunctioning protein
Example: Sickle Cell
Protein shape and function can also be changed via denaturation
pH, temperature, salt concentration, etc.

18. Proteins
Chaperonins or chaperone structure are specialized proteins that assist in the proper folding of proteins
Are not specific, but keep the protein away from potentially bad influences
Folding is spontaneous

19. Nucleic Acids
Main function is to store and transmit genetic information
2 kinds: RNA and DNA
These are both polymers/macromolecules
The monomers are nucleotides
Composed of a nitrogenous base, a 5-carbon sugar, and a phosphate group
Nucleosides are this unit minus the phosphate group

20. Nucleic Acids Two groups of nitrogenous bases Two kinds of sugars
Pyrimidines: single 6-C ring
Cytosine, thymine, uracil
Purines: double fused rings (1 5-C, 1 6-C)
Adenine, guanine
Two kinds of sugars
RNA – ribose
DNA – deoxyribose

21. Nucleic Acids
Nucleotides are linked together by phosphodiester linkages
Covalent bond between a phosphate group and a sugar
This creates the sugar-phosphate backbone
One end will have a phosphate attached to a 5’ carbon; the other will have a hydroxyl group on a 3’ carbon (these are the ends of DNA and this plays a role in replication)
The opposing sides of DNA are linked via hydrogen bonds and twist about an imaginary axis creating the double helix