Macromolecules: Proteins Flashcards
(27 cards)
Proteins are…
polymers/ bio macromolecules of amino acids
There are … different types of AA which form … bonds
20
Peptide
Structure of AA
Chiral carbon with a carboxyl group, Hydrogen atom, Amino group and a variable R group
In aqueous solutions AA behave as …
zwitterions as they ave both an acidic (COOH) and basic (NH2) group
2 types of proteins?
Globular - functional (enzymes, haemoglobin)
- Hydrophobic AA face inwards
- usually water soluble
Fibrous - structural (keratin, collagen)
- can form long chains
- may be insoluble
Primary structure of a protein
This is the sequence, number and type of amino acids that makes up a polypeptide chain bases on the sequence of triplet codons from mRNA.
A peptide bond forms via a condensation reaction between an amine group of one AA and and a carboxylic acid of another group
Secondary structure of a protein
The O in the COOH is delta negative, the H in the NH2 group is delta positive. Hydrogen bonds forms between these atom leading to alpha helix and beta pleats.
Describe an alpha helix
all the N-H bonds are on the same side of the chain
a spiral is formed
Describe a beta pleat
The N-H and C=O groups alternate from one side to the other
folded sheets
Tertiary structure of a protein
The beta pleats and alpha helixes are folded into a 3D structure with disulphide bridges, hydrogen bonds and ionic bonds.
The hydrophobic AA face inwards and hydrophilic acids face outwards.
Discuss disulphide bridges
Strong covalent bonds between S-S in cysteine AA
Ionic bonds
between charged R groups, these bonds can break with PH changes
Hydrogen bonds
H to N/O, numerous, very easily broken
Are there any other bonds in the tertiary structure
Yes - non covalent bonds:
van der Waals + hydrogen bonds - broken by temperature changes can led to denaturation.
Quaternary structure of a protein
Multiple 3D polypeptide structures (2+) join together
joined = formed oligomers
Functions of proteins (7):
Structure and movement
Enzymes
Signalling
Transport
Immunity
Regulation
Nutrition
Enzymes are…
biological catalysts for intra and extracellular reactions.
They have high specificity
Enzyme reactions were thought to occur through the lock and key model.
Each enzyme is only complementary to one substrate.
Rigid
Enzyme reactions occur through induced fit model
Enzymes are complementary to substrates but the active site is flexible.
When the specific substrates nears the site and bonds, the begin to slightly distort.
Lowers activation energy
Transport protein
example - haemoglobin transport oxygen to cells
Signalling protein
receptors on cell surfaces
or molecules like hormones - insulin
structure and movement protein
collagen for wound healing
actin and myosin for muscle movement
Immunity protein
antibodies and antigens
Regulation
Transcription factors/ promoters with DNA
