proteins

paper 1,2,3

importance of proteins?

growth + repair in cells/tissues

whats the importance of the shape of a protein?

specific to task

how many essential amino acids are there?

20

whats an important example of proteins?

enzymes

what do proteins contain?

carbon, hydrogen, oxygen, nitrogen, occasionally sulphur (dependent on amino acids contained)

what’s the monomer of a protein?

amino acids

polypeptides contain ___ amino acids

up to 50

proteins contain ___ amino acids

over 50

what does an amino acid glycine look like? what makes up the amino group and the acid group?

what’s a glycine?

simplest amino group

how many diff. r-groups are there?

20

what type of group differs between amino acids?

r-groups

show the formula for peptide bonds

what’s the function of proteins in relation to liver?

how many possibilities are there for a protein of x amino acids?

20^x amino acids

why are there so many different proteins?

as every amino acid position can be occupied by 1 of 20 amino acids

what is a primary structure?

• the sequence of amino acids that form a protein

  • connected by peptide bonds

whats a secondary structure?

• 2D/single structures

• the α-helices + β-pleated sheets formed from H bonding between amino acids

whats a tertiary structure?

connected by ionic/disulphide/H bonds which work together to form a 3D structure

whats a quaternary structure?

• protein complex made up of more than one polypeptide subunit

• e.g. insulin, haemoglobin

how to denature a protein

• heating

  • adding heat to protein = high KE

  • proteins move + unravel

  • break H bonds + hydrophobic interactions giving second/tertiary structures

• caused by:

  • heavy metal ions (charges interacting with ionic bonds)

  • pH extremes (H⁺ + OH^- interactions)

whats a globular protein

• “spherical”

• metabolic

• hydrophobic core + hydrophilic surface

• water soluble

• e.g haemoglobin

whats a fibrous protein

• long coiled polypeptide chains

• insoluble

• structural

• repeated amino acids

• e.g. collagen

describe the structure of haemoglobin using the stages of protein folding

• primary

  • chain of amino acids formed by peptide

• secondary

  • alpha helix + small region beta pleated sheets joined by H bonds

• tertiary

  • polypeptide chains undergo further folding

  • 3 bonds from disulphide/ionic/H bonds

  • hydrophobic r groups on inside of molecule, hydrophilic r groups on outside

• quaternary

  • 4 polypeptides - 2 alpha + 2 beta

  • 1 haem group per polypeptide

  • prosthetic group haem contains Fe²⁺

sickle cell

• the diff. between normal haemoglobin + sickle cell = 1 amino acid

• at position 6, glutamic acid changed for valine on beta strands

• glutamic acid = hydrophilic amino acid

• valine = hydrophobic amino acid