3.13 Amino Acids, Proteins and DNA Flashcards
Draw the displayed formula for glycine.
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for the general structure of an amino acid.
(see page 1 in the chemrevise revision guide)
All amino acids, except glycine, are ______ because they have ________ groups around the C atom.
They rotate plane polarised light.
All amino acids, except glycine, are chiral because they have 4 different groups around the C atom.
They rotate plane polarised light.
Draw the displayed formula for 2-aminobutanedioic acid
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for 2-amino-3-hydroxypropanoic acid
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for (2-)aminoethanoic acid
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for aspartic acid
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for lycine
2,6-diaminohexanoic acid
(see page 1 in the chemrevise revision guide)
What type of ions are amino acids?
Zwitterions
What is a zwitterion?
A zwitterion is an ion with a positive AND negative charge.
What state are amino acids often in?
Amino acids are often solids
Why do amino acids have relatively high melting points?
The ionic interaction between zwitterions explains the relatively high melting points of amino acids as opposed to the weaker hydrogen bonding that would occur in the no charge form.
Which part of an amino acid is an acid and which is a base?
amine group - base
carboxyl group - acid
Show what a general amino acid would look like in high pH solution.
(see page 1 in the chemrevise revision guide)
Show what a general amino acid would look like in low pH solution.
(see page 1 in the chemrevise revision guide)
Show what a general amino acid would look like in neutral pH solution.
(see page 1 in the chemrevise revision guide)
Write the equation for a general amino acid in HCl.
(see page 1 in the chemrevise revision guide)
Write the equation for a general amino acid in NaOH.
(see page 1 in the chemrevise revision guide)
Draw the displayed formula for aspartic acid in high pH
(see page 1 in the chemrevise revision guide)
Draw the skeletal formula for lycine in low pH
(see page 1 in the chemrevise revision guide)
What is a dipeptide?
Dipeptides are simple combination molecules of two amino acids with one amide (peptide) link.
Draw a dipeptide of the two amino acids on top of page 2 of the chemrevise revision guide.
correct?
Draw any esterification reaction of an amino acid.
(see page 2 in the chemrevise revision guide)
How do you hydrolyse proteins?
If proteins are heated with dilute acid or alkali they can be hydrolysed and split back into their constituent amino acids.
(see page 2 in the chemrevise revision guide for an equation)
How would you identify different amino acids in a sample?
thin-layer chromatography
Describe the method for thin-layer chromatography.
(see page 3 in the chemrevise revision guide)
In thin-layer chromatography:
Should the line be in pencil or pen on the chromatography paper?
Why?
pencil line - will not dissolve in the solvent
In thin-layer chromatography:
How big should the spots be on the line of the chromatography paper?
Why?
tiny drop - too big a drop will cause different spots to merge
In thin-layer chromatography:
How deep should the solvent line be?
Why?
Not that deep, if the solvent is too deep it will dissolve the sample spots from the plate.
In thin-layer chromatography:
Should there be a lid on the apparatus?
Why?
Yes, to prevent evaporation of the toxic solvent
You will get more accurate results if the solvent is allowed to rise to near the top of the plate but the Rf value can be calculated if the solvent front does not reach the top of the plate.
In thin-layer chromatography:
Should you dry the paper in a fume cupboard?
Why?
Yes, the solvent is toxic.
In thin-layer chromatography:
Should you wear plastic gloves?
Why?
Yes, to prevent contamination from the hands to the plate.
How do you calculate the Rf value when using thin-layer chromatography with amino acids?
Rf value = distance moved by amino acid / distance moved by the solvent
What is the primary structure of proteins?
The primary structure of proteins is the sequence of the 20 different naturally occurring amino acids joined together by condensation reactions with peptide links.
Describe the secondary structure of a protein.
(see page 4 in the chemrevise revision guide)
Describe the tertiary structure of a protein.
(see page 5 in the chemrevise revision guide)
Draw how 2 cysteine molecules bond together.
the molecule is on bottom of page 5 In the chemrevise revision guide, you’ll get it in the exam of the data sheet
they bond with the two S together.
form a sulfer bridge
Describe the active site of an enzyme.
(see page 6 in the chemrevise revision guide)
Describe a stereospecific active site.
(see page 6 in the chemrevise revision guide)
Describe how enzyme inhibitors can be used.
Many drugs act as an enzyme inhibitor by blocking the active site.
The inhibitor will often bind to the active site strongly so stopping the substrate attaching to the enzyme.
(Some inhibitors can also attach elsewhere on the enzyme but in doing so can change the shape of the active site which also stops its effectiveness)
Computers can be used to help design such drugs.
Draw the structure of a nucleotide, the molecules will be given in the data sheet but you need to know how the molecules bond to form a nucleotide.
(see page 7 in the chemrevise revision guide)
Draw how 2 nucleotides bond together to make a phosphate backbone in DNA.
(see page 8 in the chemrevise revision guide)
How many bonds form between adenine and thymine?
2
What type of bonds form between bases in DNA?
hydrogen bonds
What is cisplatin used for?
Draw the structure.
Explain how it is used for this.
anticancer drugs.
see page 9 in the chemrevise revision guide
