Intro to biomolecules Flashcards
list the 4 major biomolecules
1) nucleic acid
2) proteins
3) lipids
4) carbohydrate (MOST ABUNDANT)
what are the building blocks of
a) nucleic acid
b) proteins
c) lipids
d) carbohydrate
a) nucleotides
b) amino acids
c) glycerol and fatty acids
d) sugar
what is the significance of the 4 major biomolecules
all cells are made entirely of them (building block molecules)
what are biomolecules
large molecules (polymers) composed from covalent bonding of many repeat sub-units (monomers)
what do carbohydrates contain and give their general formula
carbon, hydrogen, oxygen
(C.H2O)n (n = 3+)
large quantities of hydroxy groups
what functions do carbohydrates have
- provide energy
- storage form of energy in body
- cell membrane component (mediates intracellular communication)
- structural component of many organisms (bacteria cell walls, insect exoskeletons, plants fibrous cellulous)
- SO essential for ALL living organisms
what are the most common forms of carbohydrates
- sugar fibres
- starch
what 4 categories are carbohydrates divided into
1) monosaccharides
(ie glucose which all cells use as energy source)
2) disaccharides
(2 monosaccharides linked by covalent bonds)
3) oligosaccharides
(3-10 monosaccharides linked by covalent bonds)
4) polysaccharides
(100s/1000s of monosaccharides linked by covalent bonds)
monosaccharides: what are they and what is their structure
simplest form of carbs + sugars
backbone = unbranched carbon chain (all C atoms linked by single bonds)
one of the C atoms is double bonded to an O atom = carbonile group
each of the other C atoms has a hydroxy group
monosaccharides: how does the position of the carbonyl group influence the name of the monosaccharide
carbonyl group at END of chain = ALDEHYDE called ALDOSE
carbonyl group at another position = KETONE called KETOSE
what is the name for simplest monosaccharides containing 3 carbons and name the 2 types
TRIOSE
- glyceraldehyde (an aldotriose)
- dihydroxyacetone (a ketotriose)
give the category name and examples of monosaccharides with 3 to 9 carbons (excluding 8)
3 = triose (glyceraldehyde, dihydroxyacetone)
4 = tetrose (erythrose)
5 = pentose (ribose, ribulose, xylulose)
6 = hexose (glucose, galactose, mannose, fructose)
7 = heptose (sedoheptulose)
9 = nonose (neuraminic / sialic acid)
which monosaccharides are major ones
those containing 4 to 6 carbon atoms
how do we number the carbons in the monosaccharide backbone
carbon 1 is the carbon on the end closest to the reactive carbonyl group (H-C=O)
what is a feature of all monosaccharides (except for dihydroxyacetone)
contain at least 1 asymmetrical (CHIRAL) carbon atom which makes the carbon optically active
what is an asymmetric / chiral carbon
a carbon with 4 different types / groups of atoms attached to it
what can we not do with chiral molecules
superimpose them on their mirror images by any combination of rotations / translations
what are the 2 different forms from the arrangement around an asymmetric carbon
OPTICAL ISOMERS (D isomer and L isomer)
- image mirror of the order
- not superimposed
so what are the 2 optical isomers of glyceraldehyde (simplest aldose)
D-glyceraldehyde
L-glyceraldehyde
define isomer
compounds with the SAME molecular formula but DIFFERENT molecular structures
define stereoisomer
subset of isomers
same with respect to which atoms are joined to which other atoms
BUT the atoms are oriented differently in space
define enantiomers
stereoisomers which are NON-SUPERIMPOSABLE mirror images
(2+ compounds w same molecular formula and seq of bonded atoms differing in only spatial arrangement of the atoms)
molecule with 1 chiral carbon exist as stereoisomers termed enantiomers
why do carbohydrates have many stereoisomers
because of the arrangment of the OH groups around each asymmetric carbon
what does the number of stereoisomers a molecule will have depend on
a molecule with ‘n’ asymmetric carbons can have 2^’n’ stereoisomers (2 because one D and one L)
example: aldohexose... 4 asymmetric carbons so 2^4 = 16 stereoisomers 8 D-isomers and 8 L-isomers
what are D and L conformations determined by in glyceraldehyde (only 1 asymmetric carbon)
orientation of the hydroxy group around the asymmetric carbon
D-ISOMER - if hydroxy group is on the right about the asymmetric carbon
L-ISOMER - if its on the left
what are D and L conformations determined by in larger molecules (more than 1 asymmetric carbon)
based on orientation of hydroxy group on the asymmetric carbon furthest from the carbonile group (on right = D, on left = L)
what happens in monosaccharides with 5+ carbon atoms in backbone and how
occur in aqueous solutions as cyclic structures forming either alpha or beta form
Carbonile group forms a covalent bond w the O of the OH group along the chain
what is the name of the carbon where the ring forms and orientation of the hydroxy group can change and what determines alpha or beta composition
ANOMERIC CARBON
thus the 2 forms are called ANOMERS…
ALPHA FORM = when hydroxy group on anomeric carbon points DOWN
BETA FORM = when hydroxy group on anomeric carbon points UP
what can the rings of cyclic monosaccharides do
open and re-close allowing rotation to occur about the anomeric carbon (this yields the 2 distinct configurations)
what is the name of the process where carbohydrates change spontaneously between alpha and beta configurations
MUTAROTATION
what are 3 diagrams to depict monosaccharide structures
1) cyclic fischer projections (in alpha = places hydroxy attached to anomeric carbon to right toward the ring)
2) haworth projection
3) chair conformation
(in alpha the 2 above place the hydroxy downwards)
what happens in alpha and beta anomeric forms of ketahexoses
hydroxy group on carbon 5 reacts with ketone group at carbon 2 to form a 5 or 6 membered ring
the 5 membered ring structures resemble furan (an organic molecule) so are termed FURANOSES
the 6 resemble pyran so termed PYRANOSES
how is a disaccharide formed
2 monosaccharides bond together through a dehydration reaction which forms a covalent glycosidic bond (between anomeric hydroxyl of 1 sugar and hydroxyl of a 2nd)
what is a glycoside
molecule where a sugar is bound to another functional group via a glycosidic bond
what are the 3 important disaccharides
sucrose
maltose
lactose
what is lactose
galactose + glucose monosaccharides bound by beta 1,4 glycosidic bond principle sugar (carbohydrate) found naturally in milk of mammals / dairy
what is lactose digested by and what happens if this is lacking
lactase
(+ by bacteria in the gut through FERMENTATION producing H2, CO2 + CH4)
lactose intolerance
what is sucrose
glucose + fructose joined by alpha 1,2 glycosidic bond
obtained from sugar cane and bead
what is sucrose used in (medically)
cough medicine = makes it taste sweet
sweetener in pharmaceuticals
what is maltose
2 glucose molecules connected by alpha 1,4 glycosidic bonds
a product of starch breakdown (2 step) during digestion
found in germination
what are oligosaccharides
- composed of 3-10 monosaccharides connected by glycosidic bonds
- large numbers of them = prepared by partially breaking down polysaccharides
- most of few naturally occuring ones are in plants
- examples = raffinose, stachyose, verbascose
what are polysaccharides
- most complex + important carbohydrates
- long chains of monosaccharides linked by glycosidic bonds
- can be branched or unbranched
- high molecular weight
what is the most common monomer used to generate polysaccharides
D-glucose
which 3 types of polysaccharides have been recognised depending on component monosaccharides
1) homopolysaccharides
2) heteropolysaccharides
3) congegated polysaccharides
what are homopolysaccharides
give examples
polysaccharides with only 1 type of monosaccharide in the chain
starch, glycogen, cellulose
what is starch
- major form of stored carbohydrates in plant cells
- identical structure to glycogen BUT lower degree of branching
- made up of a mixture of amylose and amylopectin
what is amylose
linear chain of 100s of alpha glucose monomers linked by alpha 1,4 glycosidic bonds
what is amylopectin
branched molecule
1000s of alpha glucose monomers linked by alpha 1,4 glycosidic bonds
branches = formed by alpha 1,6 glycosidic bonds
how is starch digested
hydrolysis reaction by amylase
2 step
starch -> maltose -> glucose (by maltase)
what is glycogen
- long term energy store in animal cells
- made primarily by liver + muscles
- made of alpha glucose monomers linked by alpha 1,4 glycosidic bonds
branched bc of alpha 1,6 glycosidic bonds
what is the structure of glycogen
compare this to amylopectin
compact because of coiling of polymer chains (allows large amounts of carbon energy to be stored in small volume with little effect on cellular osmolarity)
more extensively branched with branches 1 in every 10 units (amylopectin = 1 in 30)
what is cellulose
- firbous carbohydrate found on all plants
- thousands of d-glucose sub-units linked by beta 1,4 glycosidic bond
- unbranched + linear (chains arranged parallel)
- no coiling or helix formation
how is cellulose broken down
humans = digestive juice lacks enzymes to hydrolyse glycosidic bond
BUT certain microorganisms make cellulase so can digest it
what are derivative carbohydrates
- sugar molecules modified with substitute other than hydroxy groups
- can contain nitrogen, phosphate + sulphur compounds (glycosaminoglycans, sugar phosphates / acetates)
MOST sugar derivatives…
- occur naturally
- important biological function
(ie chondroitin sulphate - imp structural component of cartilage providing its resistance to compression)
what are a number of carbohydrates (large polysaccharides and small oligosaccharides found in association with)
molecules other than carbs ie lipids + proteins
carbs with lipids = GLYCOLIPIDS
carbs with proteins = GLYCOPROTEINS
what are heteropolysaccharides
2+ different monosaccharides linked to form a polysaccharide
USUALLY repeating units of disaccharide
BUT SOMETIMES the polymer has 2 alternating disaccharides
