Amino acids and proteins Flashcards
Describe the nature of amino acids
Amino acids consist of a central alpha carbon atom, bonded to a hydrogen atom, an amine group, a carboxyl group and a variable R group.
What are the 9 essential amino acids to humans (those we cannot produce)?
Histidine, lysine, threonine, valine, leucine, isoleucine, methionine, phenylalanine and tryptophan.
Name the 2 polar acidic side chained-amino acids
Aspartic acid and glutamic acid
Name the 3 polar basic side chained-amino acids
Arginine, histidine and lysine
Name the 7 polar neutral side chained-amino acids
Asparagine, glutamine, serine, threonine, tyrosine, cysteine and glycine
Name the 8 non-polar side chained-amino acids
Alanine, valine, leucine, isoleucine, methionine, proline, phenylalanine and tryptophan
What is the primary structure of a protein?
The sequence of amino acids in the polypeptide
What is the secondary structure of a polypeptide?
The folding of the polypeptide due to hydrogen bonds between amino acids, to form alpha helices or beta pleated sheets
What is the tertiary structure of a polypeptide?
The way in which the helices and sheets are folded up into more densely packed globular structures and held in these conformations by weak chemical bonds, such as H bonds and ionic bonds between side chains. The structures may be stabilised by covalent disulphide bonds between cysteine molecules
What is quaternary structure of polypeptides?
In proteins made of multiple polypeptide chains, the quaternary structure is how the chains are arranged in relation to each other to form the mature protein
Name 3 fibrous proteins
Collagen, myosin and keratin
Name 2 properties of collagen protein
Collagen has a triple helix, not an alpha helix.
Collagen molecules may assemble into long fibres.
Water soluble proteins are often ________ in shape
globular
In water soluble proteins, hydrophilic residues are mostly found where?
The external surface
What causes sickle-cell anaemia?
A mutation in a single amino acid in the beta chain of haemoglobin
What is the amino acid substitution involved in sickle-cell anaemia?
Glutamic acid is replaced by valine at position 6 due to mutation.
What is the cellular target in bacteria of the antibiotics streptomycin and tetracyclines?
Streptomycin and tetracyclines target the small subunit of ribosomes to prevent protein synthesis
What is the cellular target in bacteria of the antibiotics chloramphenicol and erythromycin?
Chloramphenicol and erythromycin target the large subunit of ribosomes in bacteria
Name 3 limitations of antibiotics acting on protein synthesis
They can’t act on viruses.
There can be antibiotic resistance, via alteration of target sites or destruction of the antibiotic.
They may inhibit protein synthesis in mammalian mitochondria.
How do penicillins work?
Penicillins are antibiotics that inhibit cell wall synthesis by inhibiting the enzymes that make pentapeptide links
How does aspirin work?
Aspirin is an anti-inflammatory drug which blocks prostaglandin
How does methotrexate work?
Methotrexate is an anticancer drug and a folate analogue- it interferes with DNA precursor synthesis
In what 3 ways is the rough ER involved in protein synthesis/ processing?
- Synthesis of proteins for subsequent packaging and secretion from the cell or for insertion into intracellular structures such as other membranes.
- Involved in the initial steps of glycosylation
- Site of disulphide bond formation
In what way is the smooth ER involved in protein synthesis/ processing?
Modification of newly synthesised proteins via addition of carbohydrates/ phosphates/ lipid groups
