Macromolecules Flashcards
Roles of sugars and polysaccharides
Food molecules and energy store
Structural support
cell protection
cell-cell adhesion and motility
cell signalling
What are D isomers
straight chain polyhydroxy alcohols (linear form of cyclic sugars)
either an aldehyde or ketone group
at least three carbon units
What are the two glucose enantiomers
alpha and beta glucose
How do the two glucose enantiomers differ, which one is more stable
alpha glucose = OH group pointing down
beta glucose = OH group pointing up
beta is more stable as OH groups are further apart in the molecule
What are the polymers of the glucose enantiomers
alpha = starch and glycogen
beta = cellulose and chitin
How are sugars linked
condensation reaction, removing water forming a 1,4 glycosidic bond
What is the reducing end
the end that is free to become linearised
Glycogen
highly branched glucose polysaccharide
branching increases the number of ends available to be digested for rapid release of glucose
Structure of a ribosome
RNA and protein
active site of ribosome is RNA which is the catalyst for protein synthesis
ribozyme - extra OH on ribose
Structure of a ribosome
RNA and protein
active site of ribosome is RNA which is the catalyst for protein synthesis
ribozyme - extra OH on ribose
What is DNA and RNA used for
DNA = store of genes
RNA = gene expression
What bonds form when nucleotides are polymerised
phosphodiester
What type of pentose is deoxyribose and where is it deoxy at
Aldopentose
deoxy at the 2 position
How many hydrogen bonds between A and T, C and G
A and T = 2
C and G = 3
What are purine and pyrimidine bases
Purine = A and G, two rings
Pyrimidine = T, U, C, one ring
Why does a purine and pyrimidine always complementary base pair
keeps the sugar phosphate backbone the same distance apart all the way along the DNA strand
what is a nucleoside
ribose and base
what is a nucleoside
ribose and base
Which complementary base pair requires less energy to break
A and T as there is only two hydrogen bonds between them
Which complementary base pair requires less energy to break
A and T as there is only two hydrogen bonds between them
Which complementary base pair requires less energy to break
A and T as there is only two hydrogen bonds between them
Which complementary base pair requires less energy to break
A and T as there is only two hydrogen bonds between them
Levels of protein structure
Primary = the order of amino acid residues in the chain
Secondary = localised regular arrangements of the polypeptide backbone to form alpha helices and beta sheets
Tertiary = overall three dimensional fold of the protein
Quaternary = arrangement of multiple amino acid chains
Amino acids
Chiral carbon molecules
Carboxyl group
Amino group
Hydrogen
R group
Only amino acid that is not chiral = glycine
How do amino acids differ
Chemical groups within side chains
Hydrophobic
Water hating
Large and non polar R groups
Cluster away from water in the core of the protein or at interaction interfaces
What are the hydrophobic Amino acids
Alanine
Valine
Leucine
Isoleucine
Glycine
Cysteine
Phenylalanine
Tryptophan
Proline
Which two hydrophobic amino acids contain sulphur
Cysteine
Methionine
What amino acid can form disulphide bonds and how
Cysteine
In an oxidising environment so not in cells as this is reducing
Hydrophilic
Water loving
Forms hydrogen bonds with water
Can be uncharged but polar, negatively charged, positively charged
What are the negatively charged amino acids
Aspartic acid
Glutamic acid
(Both carboxylic acids)
What are the positively charged amino acids
Lysine (primary amine)
Arginine
Histidine
What are the uncharged polar amino acids
Serine
Threonine
Tyrosine
(Hydroxyl groups)
Asparagine
Glutamine
Peptide bond
Condensation reaction removing water as the amino and carboxyl groups are joined together forming a linear peptide
How are proteins numbered
From the N terminus to the C terminus
Residue 1 has a free NH3 +
What are the side chains of the polypeptide
The R groups
What structure is a peptide bond
Planar - no rotation
(All in one plane)
Why can the peptide bond flick between single and double bonded
Delocalisation of electrons from the nitrogen onto the single C-N gives it a partial double bond characteristics
Restricts rotational movement of the polypeptide chain around that bond
How is the confirmation of the backbone describe by
Torsion angles
What are the angles of rotation
Phi = angle around alpha carbon and nitrogen
Psi = angle around alpha carbon and carbon
How does folding of the polypeptide chain occur
Rotation of the phi and psi angles for each residue
Rotation around alpha carbon is not completely free as many combinations of phi and psi angles cause steric clashes of side chains
Disaccharides
Maltose = alpha glucose and alpha glucose
Sucrose = alpha glucose and alpha fructose
Lactose = alpha glucose and beta galactose
Lactulose = beta galactose and beta fructose
Consequences of breaching in starch and glycogen
Starch is more densely packed
More exposed end units for access by glycogen synthase/phosphorylase
How can C be converted to U
Spontaneous deamination
Why is DNA double stranded
Provide copying mechanism
Enable repair of damaged bases
Stabilise with hydrogen bonds
Why is RNA single stranded
Allow protein synthesis
Allow internal hydrogen bonding
Allow binding to proteins as well as other RNAs
Ramachandran plot shows
Most optimal phi and psi angles to avoid steric clashes
