proteins Flashcards
what are proteins?
- functional capabilities of a cell
why is there more proteins than genes?
- because of processes changing isoforms of different proteins
what are the building blocks of proteins?
- amino acids
- determine genetic code
what determines the identification of amino acids?
- variable group/ side chain
what are amino acids joined by? what determines function?
- joined covalently by peptide bonds
- how they are folded determines function
what is a peptide?
- shortened parts of a protein
what is primary structure?
- describe the amino acid sequence of a protein
- base determinant of protein shape and function
where do peptide bonds form in the primary structure?
- form between carboxyl group and amino group
what is the secondary structure?
- how peptides are folded
- force responsible is hydrogen bonds (10-100x weaker than covalent)
what does abundance of H atoms give rise to?
- many connectors that stabilise the secondary structure
- makes up for the fact that hydrogen bonds are weak
how are hydrogen bonds formed in the secondary structure?
- created by a hydrogen atom with partial positive charge an atom usually O or N with partial negative charge
what are the most widely encountered structures in secondary structure?
- a helix
- b pleated sheet
what is the tertiary structure?
- confirmation of an entire polypeptide> peptide
- stabilised by H bonds but use other interactions; electrostatic bonds, van der whaals interaction, disulfide bonds and hydrophobic interaction
what are electrostatic bonds?
- ionic bonds formed between positive and negatively charged groups
what are van der whaals interactions?
- non- covalent attraction due to movement of ions in atomic or molecular orbitals
what are disulfide bonds?
- forms between sulfhydryl group of amino acid cystine
what are hydrophobic interactions?
- tendency for hydrophobic molecules to cluster together when immersed in water
- come together in a folded protein
- forces are a result of a mutual repulsion of surrounding water
what is the quaternary structure?
- interactions between sub- units of polypeptide chains
describe the universality of interactions
- H bonds, electrostatic bonds, van der whaals interactions and hydrophobic interactions develop both within+ across all classes of biomolecules
what is denaturation of a protein?
- breaking of bonds within a protein molecule
- usually irreversible; affects the function of proteins
- occurs due to environmental factors> heat, pH levels
what are enzymes?
- essential catalysts that target substrates
- accelerate metabolic reactions
- named after the substrate or type of reaction they catalyse
what are reactants called?
- substrates
what are the three main features of enzymes?
- speed up reactions (10^5- 10^17)
- display high specificity> each enzyme catalyses 1 or a group of reactions
- catalytic power is regulated
what is the active site?
- complementary structure of enzyme and substrate
- found at the surface of the enzyme
what is the lock and key theory?
- attraction is at a small area known as active site
- only complementary to one substrate
what is the induced fit model?
- not complementary to just one so enzyme undergoes conformation change on interaction with substrate
what do many enzymes need the presence of?
- need nonprotein chemical entities or cofactors in their active site
- usually metal ions or organic compounds
what are metalloenzymes?
- metalloenzymes are metal ions embedded in organic compounds
e.g., heme
how many enzymes need a coenzyme?
- 1800 of 5000
what is Michaelis constant?
- substrate concentration at half max rate
describe how substrate availability affects reaction
- increased substrate speeds up the reaction to a point
- when all active sites are occupied the rate plateaus
how does enzyme concentration affect reaction?
- more enzyme concentration increases rate of reaction
how does temperature affect reaction time?
- increased temperature causes increased kinetic energy to a point before denaturation
how does pH affect reaction time?
- around a pH of 8= ideal conditions for rate (below/ above - denaturation)
- changes in H+ cause removal or additions of proteins from active site
