Amino acids, proteins and DNA Flashcards
What’s the function of the amine in an amino acid?
uses its lone pair to accept a proton
What is the function of the acid in an amino acids?
undergoes a condensation reaction and donates a proton
What is the formula of glycine?
NH2CH2COOH
smallest amino acid
How do you name an amino acid
The longest carbon chain includes the R group and the NH2 is a branch
e.g 2-amino,propanioic acid
What stereoisomers are amino acids
enantiomers
they all have a chiral centre except glycine
What is a Zwitterion
a molecular ion which has both +ve and -ve charges and is neutral overall
What structure do zwitterions form?
giant ionic structures
solids with high boiling points
What happens to an amino acid when in an acidic solution
the amino group is protonated and the carboxyl group is unchanged
- N2 gains another H and becomes NH3
What happens to amino acids when in a basic solution?
the carboxyl group is deprotonated and the amino group is unchanged
- the COOH loses a H and becomes COO-
What happens when an amino acid is acting as a nucleophile with something in excess
The N forms 3 bonds with the alkyl group
- quaternary ammonium salt is formed
How do amino acids react to form a dipeptide?
a water is removed
- OH is removed from COOH one and one H is removed from NH2
- form CONH bond
What is a protein?
a polymer of amino acids
- many amino acids joined together by covalent bonds forming a polypeptide
What is a primary structure protein?
sequence of amino acids
What is the secondary structure of a protein?
the shape the protein takes
- formed by hydrogen bonds between the C=O on one amino acid and the N-H on the other
What is a tertiary structure?
the way the polypeptide is coiled and folded into its overall 3D shape
- formed from more hydrogen bonds and disulfide bridges and ionic bonding
- more hydrogen bonds between R groups
How are disulfide bridges formed?
only occurs between cystines the R groups interact
the S-H on one reacts with the S-H on another
- loss of H’s forming S-S bond
- stronger than other R group interactions
How are hydrogen bonds formed between R groups in a tertiary structure?
between delta +ve H and delta -ve O
How are ionic bonds formed between amino acids?
the COOH on the R group of one amino acid can protonate the NH2 group of the other R group of an amino acid
- a bond then forms between the COO- and NH3+
What are enzymes?
globular proteins that act as catalysts
- contain a stereospecific active site where reactions take place
- the substrate binds to the active site by intermolecular forces
- these forces promote the movement of electrons within a substrate that lowers ea
What is stereospecificity?
the active site may only catalyse reactions of one of the pair of enantiomers (stereoisomers)
What is enzyme inhibition?
drugs can be designed to affect the actions of enzymes
- the active site can be blocked by changing its shape by changing temp or pH (denaturing)
OR
- a molecule with a similar shape to the substrate can be synthesised so it can bind to the active site and prevent the substrate
What is computer modelling?
used to predict and understand the factors that influence the shape of extremely complex molecules and predict their properties
- enables them to design drugs that may be used to treat medical conditions
What are nucleotides?
monomers that form DNA
How are DNA strands joined together
- strands of nucleotides are covalently joined together
- hydrogen bonds are formed between two bases
Describe the phosphate group
- its on the same side as the sugar ‘O’
- CH2 between sugar and phosphate
How are bases joined to the sugar (deoxyribose)
H from the NH bond in the base is removed
OH from the sugar is removed
- water is lost
What is the polymerisation of nucleotides?
two nucleotides bond together when the H of phosphate on one nucleotide reacts with the OH group on a sugar molecule
- water is removed
How are two nucleotide bases joined together?
hydrogen bonds form between the bases on one strand to the base on another strand
Where do bases join to the sugar (2-deoxyribose)
The NH group on the bases
How many hydrogen bonds are formed between adenine and thymine?
2
How many hydrogen bonds are formed between guanine and cytosine?
3
- so more energy is needed to separate G and C
What is the formula of cis-platin?
Cl2Pt(NH3)2
How does cis platin work as a drug?
used in chemotherapy
- it covalently bonds with guanine and stops DNA replication during cell division by cross-linking strands of DNA which kills cells
- guanine bases replace chlorine ligands in a ligand substitution reaction
- the nitrogen atom uses its lone pair to form a coordinate bond with the Pt
- guanine bases can be on the same or different strands
Why does trans-platin not work as a drug
the chlorine ligands are on opposite sides of the complex
What other fast multiplying cells in the body are affected by cis-platin
- white blood cells
- gametes
- hair cells
What are side effects of using cis-platin
- immune system
- fertility
- hair loss
What part of guanine bonds to cis-platin?
the nitrogen atoms that aren’t involved with covalently bonding to the phosphate group and which are also not involved in hydrogen bonding to cytosine
- usually the top N
