biomolecule revision Flashcards
Covalent bonds
formed by sharing of electrons
single covalent bonds
share 2 electrons between atoms
double covalent bonds
share 4 electrons & stronger than single covalent bonds
polar covalent bonds
unequal sharing of electrons producing a postive charge at one end of the molecule, and a negative charge at the other end = net dipole
non polar covalent bonds
equal sharing of electrons & no net dipole
whats stronger covalent or non covalent bonds
covalent bonds
types of non covalent bonds
- thermal energy
- can der waals
- hydrogen bonds
- iconic bonds
ionic bonds
occur between two opposite charged ions & involve the complete transfer (either gained or loss) of electrons
how are ionic bonds weakened
by water, water can cluster around charged ions to weaken the interaction
what compounds formed by non covalent bond is soluble in water
ionic bonds e.g. NaCl = table salt
hydrogen bonds
occur due to attraction of positively charged H atoms to negatively charged atoms
how are hydrogen bonds weakened
water, as water competes for H bond interactions
hydrophobic forces
occur due to the attraction between non polar molecules & exclusion of water
water molecules cannot form hydrogen bonds with non polar molecules & tend to form pentagon or hexagon cages around the non polar molecules instead
molecular complementarity
Multiple non-covalent interactions can form between complementary molecules causing them to bind.
It can be thought of as a lock and key fit between molecules whose shape and charge are complementary to each other.
E.g. molecular complementarity and non-covalent bonds are what holds two DNA strands together into a double helix.
Van der Wall forces
attraction of neutral molecules in gases e.g. hydrogen bonding = weak bond formal transient dipoles
amino acid structure
determines the properties of the protein
amino group
designates the N terminus of a protein. has a positive charge when ionised.
carboxyl group
this designates the C terminus of a protein. has a negative charge when ionised
which isomer is most common in proteins found in humans
L isomers NOT D isomers
where do peptide bonds occur
between carboxyl group of one amino acid & amine group of another amino acid
what does a peptide bond result in molecular wise
results in ned loss of one H molecule (from N terminus) & one OH molecule (from C terminus) in a process called a dehydration or condensation reaction (net loss of one water molecule)
primary structure
linear sequence of amino acids formed by peptide bonds into a polypeptide chain
secondary structure
organisation of the polypeptide chain in a alpha helix or b sheets or turns. structures are stabilised by hydrogen bonds between backbone of the amino acids
tertiary structure
arrangement of secondary structures
