Proteins Flashcards
Features and structures of fibrous proteins
- formed from long insoluble molecules, due to high proportion of hydrophobic R-group amino acids
- small amino acid range, with small R groups
- repetitive primary structure amino acid sequence
- make strong, long, complex molecules which AREN’T folded into 3D shapes
Examples of fibrous proteins
- elastin
- keratin
- collagen
Function of elastin
- found in elastic fibres within vessel walls and alveoli
- flexible- allows expansion and return
- quaternary protein made of stretchy molecules or tropoelastin
Features of keratin
- present in hair, skin, nails
- large proportion of sulphur containing amino acids, resulting in strong, inflexible, insoluble materials
- degree of bonds determines flexibility
- unpleasant smell when burnt
structure of collagen, where found
- connective tissue found in skin, tendons, ligaments
- made of 3 polypeptides wound in a long, rope like structure
Structure of globular proteins
- compact
- water soluble
- roughly spherical
- form when proteins fold into tertiary structures, and R groups kept away from aqueous environment
Examples of globular proteins
insulin
function of insulin
- hormone involved with blood glucose concentration
- solubility and shape required
Structure of conjugated proteins
- globular proteins that contain a prosthetic group (a non protein component)
- prosthetic groups lipids or carbs= glycoprotein, lipoprotein
Examples of conjugated proteins
- Haemoglobin
- Catalase
Function and structure of haemoglobin
- oxygen carrying pigment in RBC
- quaternary protein made of 4 polypeptides
- 4 subunits, each containing a prosthetic haem group
What is catalase
- quaternary
- enzyme= hydrogen peroxide breakdown
What is a peptide
- polymers made up of amino acid monomers
What do proteins consist of
- carbon, hydrogen, oxygen and nitrogen elements only
- 1 polypeptide arranged as a complex macromolecule
Amino acids- what is an R group, how many amino acids are there
-R group= variable groups, relative position and type determines the amino acid
- 20 different amino acids
How do amino acids join
- amine and carboxylic acid groups react
- the hydroxyl in the carboxylic acid group of 1 amino acid reacts with the hydrogen in the amine group of another amino acid
What is a peptide bond
- forms between 2 amino acids when they join
- condensation reaction
- results in a dipeptide
What is a polypeptide
- when many amino acids are joined
- catalysed by enzyme peptidyl transferase
How is a protein formed
- different R groups interact with each other forming different types of bond which lead to long polypeptide chains folding into complex proteins
What is the primary structure of a protein
- the sequence in which the amino acids join
- contained within DNA
- Peptide bonds only
What is the secondary structure of a protein
- O, N, H atoms of amino acids interact
- H bonds can form within an amino acid chain- pull it into a coil shape, ALPHA HELIX
- Polypeptide chains can lie parallel to each other, patterns of each acid causes pleats= BETA PLEATED SHEET
- secondary structure result of hydrogen bonds
What is the tertiary structure of a protein
- folding of the protein into its final shape
- coiling/ folding brings different R groups closer to interact
- interactions produce a variety of complex shaped proteins with specialised characteristics and functions
What are the interactions between R groups
- hydrophilic/ phobic reactions
- hydrogen bonds
- ionic bonds
- disulfide bonds
What is the quaternary structure of a protein
- results from association of 2+ individual, different protein molecules (subunits)
What enzyme breaks down peptide bonds into amino acids, type of reaction
- proteases
- hydrolysis (requires water)
