12.2 Proteins and Enzymes Flashcards
biology is the study of what
proteins and shapes fitting together
what elements do all amino acids and proteins contain
nitrogen, carbon, hydrogen, oxygen - some contain sulphur
what is special about proteins
different specific shape which allows different specific role / function
monomers of proteins
amino acids
how many types of amino acids are there
20 different types with same general structure linked by peptide bonds
protein structure
a carboxyl group, an amine group and a side chain
R groups can be…
positively charged
negatively charged
hydrophilic
hydrophobic
what do 2 amino acids join to form
dipeptide by condensation
what happens when 2 amino acids are condensed
water is removed and a peptide bond is formed
what do hundreds of amino acids join to form
a polypeptide chain
what are the 4 levels of protein structure
primary structure
secondary structure
tertiary structure
quaternary structure
primary structure of protein
- the number and sequence of amino acids in a polypeptide chain
- only involves peptide bonds
- responsible for overall structure of protein
- changing 1 amino acids might alter the structure / function of the protein
secondary structure of protein
- basic level of protein folding
- polypeptide chain either folds or coils
- alpha helix (coils)
- beta pleated sheet (zigzag)
- held together by weak H bonds only (between OH groups)
tertiary structure of protein
- folds into a specific complex 3D shape
- r group determines the specific 3D shape
- shape held together by bonds between r groups
- globular proteins
- 3 types of bonds between r groups
1 weak H bonds (OH)
2 ionic bonds weak (R)
3 disulphide bridges strong (S)
specific structure -> specific shape -> specific function
globular protein examples
haemoglobin
hormones
enzymes
function and factor (what can it do) of globular proteins
transport protein
compact and folded into spherical molecules -> soluble in water
quaternary structure of protein
- 2 or more polypeptide chains joined together
- haemoglobin 4 polypeptide chains
- collagen 3 polypeptide chains
- specific shape -> function
structural protein examples
keratin
collagen
actin + myosin
denaturation meaning
a permanent change to the specific 3D tertiary structure of a protein
when do proteins denature
at high temp and changes to the pH
denaturation process
- increase temp -> increases KE -> vibration -> breaks weak H bonds in 2nd + 3rd structure
- changing pH of environment -> breaks ionic bonds between R groups in 3rd structure
- binds break -> specific tertiary shape is lost
biuret test for proteins (detects the peptide bonds)
- place small volume of extract in a labelled test tube
- add 2cm3 of biuret solution
- positive blue to purple / violet
- negative stays blue