1.2b protein structure Flashcards
What determines protein structure?
amino acid sequence
What are proteins polymers of?
amino acid monomers
What are amino acids monomers of?
protein polymers
What are amino acids linked by and what do they form?
- linked by peptide bonds
- to form polypeptides
What are the 4 groups that amino acids are classified in according to their R groups?
- basic
- acidic
- polar
- hydrophobic
What classifies and amino acid as basic?
R group results in:
- positively charged
- hydrophilic
- key component of R group is an amine group(NH)
What classifies and amino acid as acidic?
R group results in:
- negatively charged
- hydrophilic
- key component of R group is a carboxylic acid group (COOH)
What classifies an amino acid as Polar?
R group results in:
- slightly charged
- forms hydrogen bonds
- hydrophilic
- key component of R group is hydrophilic group (carbonyl C=O, hydroxyl OH, amine NH)
what classifies an amino acid as hydrophobic?
R group results in:
- no charge, non-polar
- don’t form hydrogen bonds
- so don’t mix readily with water
- Key component of R group is hydrocarbon group CH
How does the structure of different amino acids vary?
they have the same basic structure differing only in R group
- R groups vary in:
- size
- shape
- charge
- hydrogen bonding capacity
- chemical reactivity
What is responsible for the wide range of functions carried out by proteins?
the diversity of the R groups
What is primary structure?
the sequence in which the amino acids are synthesised into the polypeptide
What causes secondary structure?
hydrogen bonding along the backbone of the protein strand results in regions of secondary structure
Give examples of secondary structure
- alpha helices
- parallel or anti-parallel beta-pleated sheets
- turns
Describe tertiary structure
the polypeptide folds into a tertiary structure
What stabilises tertiary structure?
interactions between R groups:
- hydrophobic interactions
- ionic bonds
- London dispersion forces
- hydrogen bonds
- disulfide bridges
What are disulfide bridges?
covalent bonds between R groups containing sulfur
What is quaternary structure?
Quaternary structure describes the spatial arrangement of subunits
When does quaternary structure happen?
Quaternary structure exists in proteins with two or more connected polypeptide subunits
What is a prosthetic group?
a non-protein unit tightly bound to a protein and necessary for its function
What is the ability of hemoglobin to bind oxygen dependent on?
the non-protein haem group
What is the effect of increasing temperature on interactions of the R groups?
- disrupts the interactions that hold the protein in shape
- the protein begins to unfold
- and eventually becomes denatured
What is the effect of pH on interactions between R groups?
- the charges on acidic and basic R groups are affected by pH.
- as pH increases or decreases from the optimum
- the normal ionic interactions between charged groups are lost
- which gradually changes the conformation of the protein until it becomes denatured
