Proteins Flashcards
list all 8 protein functions:
- enzymes
- defence
- storage
- transport
- hormonal
- receptor
- movement
- structural
how much dry mass do proteins account for:
50%
enzymes:
- accelerate chemical reactions
- lock and key mechanism
defensive:
eg. antibodies help inactivate and destroy bacteria and viruses
- recognise pathogens and target them
storage:
- store amino acids
- eg. casein protein of milk is major source of amino acids for baby mammals
- ovalbumin protein for egg white, amino acid source for developing embryo
transport:
transport substance
- haemoglobin: iron-containing protein
- carries molecules
hormonal:
- allows different components (organs or tissues) of an organism to communicate
eg. insulin, causes other tissues to take in glucose, to regulate blood sugar levels
receptor:
signals response to stimuli
- receptors in nerve cell detecting molecules
movement:
flagella, cilia and muscle
- proteins actin and myosin responsible for contraction of muscles
- motor proteins for cilia and flagella responsible for contraction of muscles
structural:
- support
- keratin protein in hair, skin, feathers
- collagen and elastin proteins provide framework in animal connective tissues
polypeptides:
polymers built from 20 amino acids (charged, hydrophobic, hydrophilic)
- unique linear sequence of amino acids
- proteins have one or more polypeptides
- 10 to 1000 amino acids in length
- amino acids linked by peptide bonds
amino acids:
organic molecules, carboxyl and amino groups
- amino acids differ in properties due to R groups (side chains)
peptide bonds:
to join amino acids together
- carboxyl (COOH) and amino (NH2( groups form peptide bonds, loses water in process
functional protein consists of:
1 or more polypeptides twisted and folded into 3D structure
- sequence of amino acids determines structure of protein
structure of protein determines? and what else affects function
its function,
- only some amino acids are exposed on surface of protein,
- physical and chemical properties of these also affect function
types of structural models
- space filling
- ribbon
- wire frame
primary structure:
unique sequence of amino acids
- determined by DNA
secondary structure:
coils and folds from hydrogen bonds btw amino acids in polypeptide
- alpha helix (coil)
- beta pleated sheet (fold)
list 4 chemical bonds:
- hydrogen bonds
- van der Waals interactions
- ionic bonds
- disulphide bonds
hydrogen bonds:
H atom + electronegative atom (eg. O or N)
van der Waals interactions:
uneven distrubution of electrons, dynamic positive/negative charge, allows weak bonding btw molecules
ionic bonds:
btw cation (positive) and anion (negative)
disulphide bonds:
covalent bond btw two sulphur atoms
tertiary structure:
interactions btw R groups
- H bonds, ionic, hydrophobic, van der Waals interactions
- strong disulphide bridges may reinforce protein structure
quaternary structure:
two or more polypeptide chains forming one macromolecule
chaperones:
chaperone proteins (chaperonins) aid in correct folding of protein - cap and hollow cylinder provide safe space for proper folding
protein structure: other conditions
physical and chemical can also affect protein structure
- pH
- salt conc.
- temperature
- environment
causes protein to unfold
- loss of native protein structure cause denaturation
- denatured protein in biologically inactive
eg. of denaturation
protein thermal denaturation (irreversible) egg white cooking, albumen denatures - cross links
eg. sickle cell haemoglobin
normal structure: proteins don’t associate with one another and carries O2 full capacity
vs sickle cell:
- proteins combine into fibre, greatly reducing oxygen carrying capabilities
eg. diseases from irregular protein folding
- Alzheimers
- Parkinson’s
- Huntington’s
