L1&2 - Biological Molecules Flashcards
What are the four main classes of biological macromolecules?
Nucleic acids - made from nucleotides
Lipids - made from fatty acids
Proteins - made from amino acids
Carbohydrates - made from sugars e.g. glucose. (monosaccharides)
Functions of monomers:
Sugars and fatty acids:
Nucleotide (ATP):
Sugars and fatty acids: It is an energy source.
Nucleotide (ATP): Energy carrier
Carbohydrates: (Monomers, General Formula, Functional groups, Properties, Types of Monosaccharides)
Made from monosaccharides.
Molecular formula (CH2O)n e.g. C6H12O6 - Glucose
Functional groups: Carbonyl and Hydroxyl
Hydroxyl group make monosaccharide hydrophilic and polar.
Properties: Hydrophilic, polar, water soluble
Monosaccharides can be either aldoses or ketoses. If it has aldehyde group then aldose e.g. glucose. If it has ketone group then it’s a ketose e.g. fructose.
Forming ring structure of monosaccharides:
Reacts carbonyl group (on C1) to hydroxyl group (on C5). Gives 6 ring structure - pyranose
Isomers: (Optical isomers, Epimers, Anomers and different glycosidic bonds)
Monosaccharides can occur as optical isomers (D- or L-) - mirror images. Most naturally occurring sugars are D-isomers. D-glucose can be metabolised by cells in the glycolysis pathway and not L-glucose. (C1 of glucose is chiral and has 4 different groups attached to it).
Other isomers vary in spatial arrangement of carbonyl and hydroxyl groups and so given different names.
Epimers: Stereoisomers that differ in cofiguration at a single asymmetric carbon. (OH switched planes on C2, for example.)
Anomers: Stereoisomers that differ in configuration of anomeric carbon (C1). e.g. α- and β-glucose. These forms interconvert rapidly in solution. This configuration locked when glycosidic bond forms between monosaccharides.
Different types of glucose so different bonds made. α-glycosidic bond and β-glycosidic bond.
Disaccharides:
2 monosaccharides linked by glycosidic bond. α1->4 linkage between C1 and C4. H2O released. e.g. maltose. β1->4 linkage. e.g. cellobiose/lactose αβ’1->2 linkage e.g. Sucrose (has α-glucose and β-glucose (fructose))
Polysaccharides:
Many monosaccharides come together. Energy store (starch and glycogen).
Amylose has α1->4 glycosidic bonds.
Glycogen has α1->4 and α1->6 bonds. It is branched and has similar structure to amylopectin but more branched.
Sugars can be modified and linked to lipids or proteins.
Complex oligosaccharides can form recognition molecules on cell surfaces e.g. blood group determinants.
Lipids and examples: Fatty acids: (Monomers, What determines their physical properties)
Lipids are molecules that are water insoluble (hydrophobic) but soluble in organic solvents.
Examples:
- Triacylglycerols (fats and oils)
- Glycerophospholipids and other membrane lipids
- Steroids and cholesterol
Fatty acids are the monomeric building blocks of triacylglycerols and glycerophospholipids.
Length and structural formula (saturated/unsaturated) of FA chain determines its physical properties (shape, melting point).
Triacylglycerols:
Formed by ester linkages between FA and glycerol. Different triacylglycerols made by joining different FA to glycerol. Important energy storage molecule. Hydrophobic (insoluble) so store as fat droplets within cells.
Glycerophospholipids:
Has glycerol with 2 FA and phosphate group with polar head group. Causes there to be hydrophobic tail and hydrophilic head - amphipathic so is polar. Forms bilayer.
Cholesterol:
Is a sterol lipid and made using steroid template. Needed in cell membrane - rigid structure. Inserted between glycerophospholipids and modulates membrane fluidity. Non-polar so is insoluble as it is lipid based. OH on steroid template allows it to be hydrophilic. Long carbon chain attached to template is hydrophobic.
Nucleic acids:
RNA and DNA act as information molecules for the cell, made by nucleotides.
Nucleotides consist of: pentose sugar, nitrogenous base, and phosphate.
Nitrogenous bases: Adenine, Guanine, Cytosine, Thymine and Uracil where PureAG and pyrimidine for C,T,U.
ATP (type of nucleotide) carries chemical energy in its phophoanyhydride bonds.
Proteins:
Carry out mechanical, structural and transport functions of the body.
Can be enzymes - biological catalysts.
Have a wide variety of shapes and sizes.
DNA sequence is different for each protein.
Can be polar if hydrophilic side chains stick out and hydrophobic inside and vice versa. Side chains interact and make disulphide bonds and H bonds - allow protein to fold up.
Amino acids:
Make proteins when AA joined together. All organisms have 20 common amino acids. Can be water soluble/insoluble. Side chain determines characteristics. Side chains are not involved in peptide bonding. Hydrophilic: DERKHNQSTY Hydrophobic: AGVLIPFMWC Acidic(-ve): DE Basic(+ve): RKH
