Biological Molecules Flashcards
What are carbohydrates?
Most common organic compounds on earth
Function : Energy storage, Fuel , Metabolite & Structural element
General Formula = (CH2O)n
Monomer = Monosaccharides - 2 kinds = Ketose & Aldose Polymer = Disaccharides / Polysaccharides
Examples of Monosaccharides
A- glucose (OH bottom) , B-glucose (OH top), Fructose, Galactose
Monosaccharides
Number of Carbon atoms decides name ( Triose, Tetrose, Pentose…)
Have chiral centres ( 4 different groups & non-superimposable images)
Example of Monosaccharide: Glucose
An Aldose ( Aldehyde based monosaccharide)
6 C atoms = Hexose
D-configuration = Asymmetric C-atom = most distant from aldehyde/ketone group
Can exist in long chain and ring structure
What are Oligosaccharides?
Carbohydrates
Type of oligosaccharides present in surface of RBCs = determine blood type
Condensation reactions in Monosaccharides
Monosaccharides can be joined together w Hydrogen Bonds
To form Disaccharides & Polysaccharides - releasing a water molecule
Condensation reactions in Disaccharides
a-Glucose + Fructose = Sucrose
a-Glucose + Galactose = Lactose
a-Glucose + a-Glucose = Maltose
Condensation reactions in Polysaccharides
a-1-4 Glycosidic bond = Starch, Amylase
B-1-4 Glycosidic bond = Cellulose
a-1-4 Glycosidic bind & a-1-6 Glycosidic Bond = Glycogen
D & L structures
Count downwards from top & consider penultimate carbon
If OH group = on right = D configuration
If OH group = on left = L configuration
Or
CH2OH group above ring = D configuration
CH2OH group below (in) ring = L configuration
Proteins
Made of AAs (form dipeptides/polypeptides)
20 AAs naturally occurring
9 essential - must from diet
Condensation reactions = form peptide bonds - releasing water
Functions of proteins
Carrier Functions ( Trafficking Oxygen)
Metabolic Functions ( Enzymes / Energy )
Cellular Machinery ( Spliceosome / ribeosomes)
Structural Scaffold ( Microtubules, conveyor belt, nucleosomes, histone DNA complex)
Sensing Molecules ( Receptors & Ligands)
Amino Acids
Have individual functions e.g
Precursors to drugs / hormones such as :
Tyrosine —> Adrenaline = Glycogenolysis
Histidine —> Histamine = Vasodilator
Called “ Residues” singly
Amino Acids Features
Tetrahedral arrangement w Chiral Carbon ( apart from glycine w 2H). Glycine = freer to move due to small R chain group
Readily ionises = Can form Zwitterion at neutral pH - where carboxyl group loses H+ & Amine group gains H+
At low pH = acts as base & accepts protons
At high pH = acts as acid & loses protons
Changes depending proportion of acid/ base in R group
D & L isomer can form. L = CORN clockwise. D = CORN backward
L form = common. D residues = bacterial cell walls & therapeutics
R group = usually trans arrangement.
Only 0.1% = CIS so less energetically favourable
Structure of Proteins
Primary = Covalent bonds forming polymer - e.g order of AA residues joined by PEPTIDE BONDS
Secondary = Regular folded form - often stabilised by HYDROGEN BONDS - e.g helices & sheets
Tertiary = Overall 3D - stabilised by HYDROGEN bonds, HYDROPHOBIC, HYDROPHILIC, VDW forces & DISULPHIDE BRIDGES
Quaternary = organisation of macromolecules into assemblies - often stabilised by IONIC bonds - e.g several polypeptide chains = can make up a protein
Difference in tertiary & quaternary structures
Intra-chain & inter-chain covalent bonds
Quaternary = has cofactors or coenzymes
Tertiary = a combination of secondary structures:
Beta sheet - continuous folded polypeptide chain. Beta strands w H bonds to form cross-links. Anti-parallel or parallel - which= less stable due to longer H bonds linking strands
Beta Strands - Contains 4 AA residues. Allow for 180 turns. Common in Proline, CIS conformation R group & Glycine. Small R group / Flexible.
Alpha Helix - Each turn = contains 3.6 AA residues. Stabilised by H bond between 1 & 5 residues
Side chains protrude outwards for each. Trans arrangement allows for B-sheet
Protein Structure
Membrane spanning proteins = have external hydrophobic residues - for lipid interaction & hydrophobic central channels
Water soluble - often have globular shapes
Hydrophilic residues external & Hydrophobic buried within
Can be filaments or coins instead
Proteins = denatured by high heats & changes in pH
Nucleotides
Energy Unit ( ATP ) Second Messenger ( cAMP ) RNA Synthesis (DNA / RNA) (AMP)
DNA = more stable than RNA - due to single additional oxygen
Ribonucleotide = OH Deoxyribonucleotide = H
Amino Acid Classification
Glycine = sometimes put in separate group - as it has a single H R group - reducing steric hinderance - so has different properties
Sulphuric AAs - may also be classified separately
Non - polar / Hydrophobic, aromatic, polar
Properties of AA = determined by structure - specifically R group
Lipids / Fats - Associate to form Membranes
Body Fats
Predominantly - food reserves ( for energy )
Glycerol esters w fatty acids
Lubrication between joints & insulations
Condensation reactions form ester bonds
Triglycerides / Phospholipids - used as bilayers in cell membrane, micelles and liposomes
Saturated fatty acids = X double bonds
Unsaturated-cis fatty acids = H atoms same side ( bent configuration)
Unsaturated-trans fatty acids = H atoms opposite sides
Cholesterol
Steroid
Can intercalate into the membrane
OH group interacts w polar heads & it’s steroid scaffold w fatty acids
Making them closer together
This decreases fluidity & increases flexibility of the membrane
Reduces permeability for soluble molecules
Hormones building block for aldosterone, cortisol,testosterone & progesterone
Structure & Function relationships
Proteins -> denature / mutated = affect function
Starch & Glycogen = Major energy sources for humans
Whereas we can’t digest Cellulose
Single oxygen difference makes DNA much more stable than RNA
Examples of single molecule disease
Diabetes ( insulin - dependent ) - absence of a protein hormone ( insulin ) leads to failure to regulate blood glucose
Sickle Cell disease - one AA change in a globin chain - causes haemoglobin to aggregate ( combine ) into polymers
Cystic Fibrosis - absence of a membrane protein that transports chloride - leads to altered properties of secretions
