general properties of proteins Flashcards
what are amino acids?
monomers from which proteins are made
what is the structure of an amino acid?
look up
what are the 3 groups in the amino acid structure and what do they consist of?
- amino group
- r group
- carboxylic acid group
what is the r group?
a carbon containing side chain
what is the bond that forms between two amino acids?
peptide bond
what reaction forms the peptide bond between two amino acids and what is given off?
condensation reaction, water
what is formed by the condensation of two amino acids?
a dipeptide
draw a dipeptide
look up
how are peptide bonds broken?
hydrolysis reaction
what are polypeptides?
formed by the condensation of many amino acids, a long chain of them
what is the test for proteins?
biuret test
explain the biuret test.
- place sample of solution to be tested in a test tube and add an equal volume of SODIUM HYDROXIDE solution at room temp
- add a few drops of very dilute (0.05%) COPPER (II) SULFATE solution and mix gently
- PURPLE colouration indicates the presence of peptide bonds and so a protein, remains blue if not
what are the 5 types of proteins?
structural catalytic signalling fibrous proteins globular
what are fibrous proteins?
proteins formed from parallel polypeptide chains and held together by cross links
these form long, rope like fibres, with high tensile strength and are generally insoluble in water
3 examples of fibrous proteins.
- collagen
- keratin
- silk
what are globular proteins? and how are they structured?
have a spherical shape caused by tightly folded polypeptide chains
the chains are usually folded so that the hydrophobic groups are on the inside and the hydrophilic groups are on the outside, makes them soluble in water
3 examples of globular proteins.
- transport proteins (haemoglobin)
- enzymes (lipase)
- hormones (oestrogen)
what is the primary structure of a protein?
the sequence of amino acids found in its polypeptide chains -determines its properties and shape
what is the secondary structure of a protein?
the shape which the polypeptide chain forms as a result of hydrogen bonding
ALPHA HELIX, BETA PLEATED SHEET
how are hydrogen bonds formed in secondary structure (or all structures) of proteins?
hydrogen atoms have a small positive charge and the oxygen and nitrogen atoms have a small negative charge, opposite attract to form hydrogen bonds
what is the tertiary structure of a protein?
due to the bending and twisting of the polypeptide helix into a compact structure
hydrogen, ionic & disulfide bonds
what is the quaternary structure of proteins?
comes from the combination of a number of different polypeptide chains and prosthetic groups into a large, complex protein molecule
