3.6-3.7 and 3.10 proteins Flashcards
(30 cards)
what are the 4 types of R group interactions between amino acids?
-hydrogen bonds
-ionic bonds between oppositely charged R groups
-disulphide bonds between R groups containing sulfur ( only cysteine ) , forms disulphide bridges
- between hydrophilic and hydrophobic R groups ( forms weak bonds )
why are there different levels of protein structure?
due to the way R groups interact within and between polypeptide chains
what are the different levels of protein structure?
primary, secondary, tertiary and quaternary
describe a primary protein
it is a linear protein that only has peptide bonds
describe a secondary protein
- has peptide bonds and hydrogen bonds
-hydrogen bonds form between adjacent carboxyl groups and amine groups between every 4th peptide bond
-coil into an alpha helix
-if the polypeptide chains are parallel they form a beta-pleated sheet
what is a simple protein?
a protein with no prosthetic group
describe a tertiary protein
-due to further conformational change of a secondary protein r groups are close enough to interact causing further folding
-have: peptide bonds, hydrogen bonds and R group interactions
describe a quaternary protein
-has 2 or more subunits (polypeptide chains)
-has peptide bonds
hydrogen bonds and R group interactions are between polypeptide chains rather than within a polypeptide chain
what is a globular protein?
a compact (usually spherical) water soluble ( due to hydrophillic R groups on the outside ) protein
what is an example of a globular protein?
insulin
what is a conjugated protein?
a globular protein that also has a non-protein component= prosthetic group
what are examples of a conjugated protein?
haemoglobin:
-prosthetic group = haem which has a Fe2+ ion
-quatenary protein with 2 alpha and 2 beta subunits
catalase:
- has 4 haem groups
the Fe2+ binds with the H2O2
what is a fibrous protein?
-amino acids in a primary structure arranged in a repetitive sequence
-long, insoluble molecule
what are three types of fibrous protein?
keratin, elastin, collagen
describe keratin
-in hair, skin and nails
-has a big portion of cysteine =strong disulphide bridges=strong, inflexible and insoluble
describe elastin
-contains elastic fibres i blood vessels and alveoli
-contains stretchy molecule ( tropoelastin ) making a flexible molecules
describe collagen
-in the connective tissue in skin, tendons, the nervous system and ligaments
-3 polypeptide chains wound together like a rope making it flexible
describe the structure of an amino acid
the central carbon atom is attracted to a hydrogen, an R group, an amine group and a carboxyl group
the R group differs in every amino acid- it has different chemical groups
how many types of amino acids are there?
20
How is a dipeptide formed?
Condensation reaction between two amino acids forming a peptide bond. The hydroxyl group from the carboxyl group and a hydrogen from the amine group bond to form a water. Catalysed by peptidyl transferase
What is the hydrolysis of a dipeptide catalysed by?
Protease
Outline the process of transcription
- A section of DNA is unzipped by helicase
- Free nucleotide will base pair with complementary bases exposed on the anti-sense strand
- RNA polymerase forms phosphodiester bonds between RNA molecules which forms mRNA
- mRNA detaches from the DNA and leaves through the nuclear pores to a ribosome
- The DNA recoils
Why does transcription occur?
Chromosomal DNA to big to leave the nucleolus to supply coding info
