3.13- Amino acids, proteins and DNA Flashcards
What is the general structure of an amino acid
Amino acids contain an amine group and a carboxylic acid group to the same carbon
What is the optical acitivity of amino acids
All amino acids except for glycine are chiral because there are four different groups around the C, They rotate plane polarised light
What is a zwitterion
The amino acid always exist as a dipolar zwitterion, the zwitterion have a postive end with the NH3+ and a negative end with the CO2- ion
Explain the acidity and basicity of amino acids in different pH solutions
The amine group is basic and the carboxylic acid group is acidic
If they are in a alkaline solution of a high pH the zwtitterions will be only negative CO2- , if in an acidic solution with a low pH the zwitterions will be only positive NH3+
What happens to the extra carboxylic acid or amine groups that are attached to the different carbons
They willl also react and change form in alkalie and acidic conditions
What is a dipeptide
Dipeptides are a simple combination of molecules of two amino acids with one amide link, for any 2 amino acids there are two possible combinations of the amino acids in the dipeptide
What are some of the other reactions of amino acids
They can also go under esterfication
With a reaction with alcohol or acyl chloride they can react to form an ester
What can you use to hydrolyse di peptites/proteins
You canuse concentrated hydrochloric acid or concentrated strong alkalis, they can be hydrolysed and split back into thier constituent amino acids
WHat is the primary structure of proteins
It is the sequenze of the 20 different natrually occuring amino acids joined together by condensation reactions with peptide loinks
What is the secondary structure of protein, alpha helix
Held in a corkscrew shape with hydrogen bonds between the H of -N - -H+ group and the -O of C +=O of the fourth amino acid along the chain, the R groups ar all pointed to the outside of the helix
What is the secondary structure of protiens, pleated sheet
The protein chain folds into parallel strands side by side, ther protein chain is held into the pleated shape by hydrogen bonds between the H of the N-H group and the O of C=O of the amino acid much further along the chain in the parallel region
What is the tertiary structure of proteins
The tertiary structure is just the folding of the secondary structure inro more complex shapes, it is held in shape by the interactions betwen the R side grop sin more distant amino acids, there are many different types of interactions like hydrogen bonding, sulfur bonds and ionic intercations
Where does ionic interactions occur in tertiary protein structures
There could be a transfer of H+ from COOH to the NH2 groups as it is in simple amino acids
Where could sulfur bridges be formed in a tertiary protein
With two cysteine side chains that are close together, due to folding in the protein chain they can react to form a sulfure bridge which is a covalent bond
What is an enzyme
Enzymes are proteins, they have active sites which are ustuall a hollow in the globular protein structure into which a substrate molecule can bond to the amino acid side chain, throughout a variety of interactions like all of the intermolecular forces and ionic interactions
What properties do substrates need to have to bond to the enzyme correctly
The interactions need to be strong enough to hold the substrate for long enough for the enzyme catalysed reaction to occur but weak enough for the product to be released
They also have to have the right shape with the correct positions of functional groups (lock and key hypotheses)
Explain how a stereospecific active site works
If there is a substrate that is chiral, it is likely that only one of the enantiomer will be able to fit in the enzyme so only one isomer will be catalysed, this is becuase the substrate functional groups do not line up with the enzyme functional group so they are unable to form bonds unlike the other enatiomer
What is an enzyme inhibitor
They work by blocking the active site, they bind t the active site strongly so stopping the substrate attaching to the enzyme
Give the names of the 6 different molexules present in DNA
. Phosphate ion
. 2-Deoxyribose aka pentose sugar
Bases-
. Adenine
.Guanine
.Thymine
.Cytosine
What is a nucleotide
A nucleotide is made up from phosphate ion bonded to 2-deoxyriose which is in turn onded to one of the four bases
How do the pentose sugar and the phosphate group bond
There is a sugar phostophate sugar phosphate polymer chain which bases attached to the sugars
The bonds are betweeh the 2 OH bonds in each molecule
How does dna exist
There are 2 complementary starnds of the polymer chain in a form of the doule helix . the A must be matched to T and C to G
How does cisplatin work as an anticancer drug
2 chlorides ions are displaced and the molecule joins on the DNA, in doing this stops the replication of cancerous cells. However it can also prevent the replication of healthy cells by bonding on to the healthy DNA which may lead to side effects like hair loss.
