Biological Molecules 4 - Amino acids and proteins Flashcards
What is an amino acid a monomer of?
protein
What is the additional element that amino acids are made of?
nitrogen
State the general formula of an amino acid
R.NH2CH.COOH
What is the R group?
It is the variable group and represents the rest of the molecule
there are 20 diff. variable groups
it is diff. for each amino acid,
can be polar or nonpolar
can have a + or - charge
Since there are 20 diff. amino acids in nature, how do they differ?
no. of amino acids
type of amino acids
sequence of amino acid
How is a dipeptide formed and by which molecule?
2 amino acids can join to form a dipeptide
the resulting bond is a peptide bond
it is a condensation reaction so H20 eliminated
involves the NH2 group of an amino acid and the COOH group of another.
broken down by hydrolysis reaction
What are polypeptides?
they are formed by many amino acids joined together by peptide bonds
they are polymers
What do polypeptides form and what do they all have?
form proteins
all have a primary and secondary structure
sometimes and occasionally can have tertiary and quaternary structures
What does the primary structure of a protein refer to?
the no. and sequence of amino acids in a polypeptide chain
contain peptide bonds
How is a secondary structure formed from the primary structure and what are the 2 types?
the primary structure of a polypeptide can coil to form either an alpha-helix or a beta-pleated sheet.
the alpha-helix is held in a spiral shape by hydrogen bonds
the beta-pleated sheet is a flat zigzag structure also held by hydrogen bonds e.g silk
What are the 2 fibrous alpha helices and what are they shaped like?
keratin - found in hair and nails
collagen - found in connective tissue and skin
rope-like strands.
How is the tertiary structure formed from the secondary structure?
the sec. struc. folds to give complex 3D shapes held by bonds that form between R groups of some amino acids in the polypep. chain
What type of proteins are in the tertiary structure?
globular e.g enzymes, hormones and plasma
Give the 5 bonds and interactions in the tertiary structure
hydrogen bonds - between O and OH
ionic bonds - between oppositely charged R groups
disulphide bridges - between S atoms (cysteine)
Hydrophobic R group interactions - inside of protein
Hydrophilic - outside
Describe the quaternary structure
occurs when more than one polypep. chain with a tertiary structure combine to form a larger protein complex
the bonds involved are similar to the tertiary structure
sometimes associated with non-protein groups (prosthetic groups) e.g haemoglobin
heam groups in haemoglobin are prosthetic groups which contain iron
