Levels of organisation and structure

what are the levels of protein organisation from smallest to largest?

primary

secondary

tertiary

quaternary

what is the primary structure of a protein?

the linear arrangement of amino acids (linked together by peptide bonds between carboxyl and amino groups)

what forms the backbone of the primary structure

repeating nitrogen, ⍺ carbon, carbonyl carbon and oxygen atoms

where is the N terminus and C terminus of an amino acid located?

N terminus on the left

C terminus on the right

what is the secondary structure of a protein?

stable spatial arrangements of polypeptide chain segments

what holds polypeptide chain segments together in secondary structure?

hydrogen bonds between carbonyl and amide groups in the backbone

what types of structures are found in secondary organisation

alpha helices

beta pleated sheets

beta turns

what is tertiary level of organisation?

the overall 3D conformation of a polypeptide chain (folded protein)

what types of bonds and interactions can be found in tertiary proteins?

hydrophobic interactions

van der Waal’s forces

hydrogen bonds

disulfide bridges

backbone and side chain interactions

what determines and defines the tertiary structure of a protein?

R groups (side chains) of amino acids in the primary structure

what is quaternary structure of a protein?

spatial arrangement of multiple polypeptide subunits

each subunit has its own primary, secondary and tertiary structure

what does sequence mean?

the sequence amino acids

what does structure mean?

what the protein looks like (influenced by sequence)

what does function mean?

what a protein does and how (influenced by structure)

what is an example of the influence of sequence on structure on function?

haemoglobin

• contains 4 subunits, each with an iron atom that binds oxygen (sequence)

• one subunit binds to oxygen, which causes conformational change of other subunits, making it easier for them to bind to oxygen (structure)

• this helps oxygen bind quicker to haemoglobin (function)

what is the impact of a mutation on a protein?

mutation affects sequence which can have cascading effect on structure and function

what is an example of a mutation that has cascading effects?

sickle cell anaemia

• point mutation in β chain of haemoglobin causing HBB gene changed to HbS gene

• GAG → GTG (DNA) -—→ GUG (RNA)

• amino acid is changed to valine (instead of glutamic acid)

• valine causes deoxygenated haemoglobin to stick together due to sickled shape - this can block capillaries

what are examples of some of the functions that proteins can have?

• defense

• storage

• communication

• enzymes

• structural

• transport