Proteins - amino acids Flashcards
what is an amino acid
monomers of all proteins with the same basic structure
what are peptides
polymers made up of amino acid molecules (the monomers)
what do proteins consist of
one or more polypeptides arranged as complex macromolecules and they have specific biological functions.
what do all proteins contain
the elements carbon, hydrogen, oxygen and nitrogen. sometimes contain sulfur
what structural properties do proteins have
they are the main component of body tissues such as muscle, skin, ligaments and hair
what catalytic properties do proteins have
all enzymes are proteins, catalysing many biochemical reactions
what signalling properties do proteins have
many hormones and receptors are proteins
what immunological properties do proteins have
all antibodies are proteins
what do the protein constituents on membranes act as
carriers and pores for active transport across the membrane and facilitated diffusion
how many different amino acids are there
over 500
how many amino acids are found in proteins
20
what does each protein chain of amino acids have
an amine group (-NH2) on one end and a carboxyl group (-COOH) at the other end
what does the R group represent
a side chain from the central “alpha” carbon atom and can be anything from a simple hydrogen atom to a more complex ring structure. R groups can vary by size, by charge and by polarity with some being hydrophobic and some hydrophillic
even though each amino acid has the same general structure, what makes each one different
the nature of the R group which defines an amino acid. different R groups result in different amino acids.
how do each of 20 amino acids act in our body
- 5 are non essential as our bodies are able to make them from other amino acids.
- 9 are essential and can only be obtained from what we eat
- 6 are conditionally essential as they are only needed by infants and growing children
what is the simplest amino acid
glycine
how do amino acids act as buffers
when dissolved in water, the amine group and carboxyl group can ionise. this means the amine group can accept an H+ ion to change from NH2 to NH3+. the carboxyl can give up an H+ to change from COOH to COO-. the carboxyl group acts as an acid in producing H+ ions. the amine group acts as a base in accepting H+ions
how does the amine group act as a base
in accepting H+ions
at low pH (lots of H+ ions in solution), the amino acid will accept H+ ions
at high pH (where there are fewer H+ ions in solution) the amino acid will release H+ ions
why are amino acids amphoteric
this means amino acids have acidic and basic problems. in a long chain of amino acids, you will amine and carboxyl groups on each end, but there are also many on the R groups of different amino acids
how are protein chains affected by this amphoteric nature
by accepting and releasing H+ ions, amine acids can help to regulate changes in pH. this is known as buffering
what is a buffer
a substance which helps to resist large changes in pH
how are amino acids joined together
by covalent bonds called peptide bonds
how are peptide bonds like glycosidic bonds and ester bonds
making a peptide bond involved condensation reactions and breaking peptide bpnds involves hydrolysis.
what do protease enzymes break down
in the intestine, they break down peptide bonds during digestion. they also break down protein hormones so their effects aren’t permanent.
how do amino acids join
the R groups are not involved. the hydroxyl in the carboxylic acid group of one amino acids reacts with a hydrogen in the amine group of another amino acid. a peptide bond is formed between the amino acids and water is produced
what is the resulting compound when two amino acids join together
a dipeptide molecule
what does joining a larger chain of amino acids result in
polypeptide
what can proteins consist of
a single polypeptide chain or more than one chain bonded together.
how do different R groups interact with each other
to form different types of bonds
what do the different sequences of amino acids lead to
different structures with different shapes being produced. the very specific shapes of proteins are vital for the many functions proteins have with living organisms
why does the peptide bond have some properties of a double bond
the peptide bond is depicted as a single bond but due to the electron arrangement around the bond, it has some properties of a double bond. this means the bond is shorter than a conventional C-N bond. it inhibits rotation around the peptide bond. this makes the polypeptide chain relatively stiff and rigid
