Proteins - amino acids

Question 1

what is an amino acid

Answer 1

monomers of all proteins with the same basic structure

Question 2

what are peptides

Answer 2

polymers made up of amino acid molecules (the monomers)

Question 3

what do proteins consist of

Answer 3

one or more polypeptides arranged as complex macromolecules and they have specific biological functions.

Question 4

what do all proteins contain

Answer 4

the elements carbon, hydrogen, oxygen and nitrogen. sometimes contain sulfur

Question 5

what structural properties do proteins have

Answer 5

they are the main component of body tissues such as muscle, skin, ligaments and hair

Question 6

what catalytic properties do proteins have

Answer 6

all enzymes are proteins, catalysing many biochemical reactions

Question 7

what signalling properties do proteins have

Answer 7

many hormones and receptors are proteins

Question 8

what immunological properties do proteins have

Answer 8

all antibodies are proteins

Question 9

what do the protein constituents on membranes act as

Answer 9

carriers and pores for active transport across the membrane and facilitated diffusion

Question 10

how many different amino acids are there

Answer 10

over 500

Question 11

how many amino acids are found in proteins

Answer 11

20

Question 12

what does each protein chain of amino acids have

Answer 12

an amine group (-NH2) on one end and a carboxyl group (-COOH) at the other end

Question 13

what does the R group represent

Answer 13

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

Question 14

even though each amino acid has the same general structure, what makes each one different

Answer 14

the nature of the R group which defines an amino acid. different R groups result in different amino acids.

Question 15

how do each of 20 amino acids act in our body

Answer 15

• 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

Question 16

what is the simplest amino acid

Answer 16

glycine

Question 17

how do amino acids act as buffers

Answer 17

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

Question 18

how does the amine group act as a base

Answer 18

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

Question 19

why are amino acids amphoteric

Answer 19

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

Question 20

how are protein chains affected by this amphoteric nature

Answer 20

by accepting and releasing H+ ions, amine acids can help to regulate changes in pH. this is known as buffering

Question 21

what is a buffer

Answer 21

a substance which helps to resist large changes in pH

Question 22

how are amino acids joined together

Answer 22

by covalent bonds called peptide bonds

Question 23

how are peptide bonds like glycosidic bonds and ester bonds

Answer 23

making a peptide bond involved condensation reactions and breaking peptide bpnds involves hydrolysis.

Question 24

what do protease enzymes break down

Answer 24

in the intestine, they break down peptide bonds during digestion. they also break down protein hormones so their effects aren’t permanent.

Question 25

when do amino acids join

Answer 25

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

Question 26

what is the resulting compound when two amino acids join together

Answer 26

a dipeptide molecule

Question 27

what does joining a larger chain of amino acids result in

Answer 27

polypeptide

Question 28

what is the reaction to form polypeptides catalysed by

Answer 28

the enzyme peptidyl transferase present in ribosomes

Question 29

what can proteins consist of

Answer 29

a single polypeptide chain or more than one chain bonded together.

Question 30

how do different R groups interact with each other

Answer 30

to form different types of bonds

Question 31

what do the different sequences of amino acids lead to

Answer 31

different structures with different shapes being produced. the very specific shapes of proteins are vital for the many functions proteins have with living organisms

Question 32

why does the peptide bond have some properties of a double bond

Answer 32

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