Proteins Flashcards
Proteins are made of elements…
C,H,O,N and some S and P
Proteins are po…
polymer molecules.
There are millions of…
different proteins
Proteins make up more than…
50% of a cell’s dry mass.
How many essential amino acid is there?
8
General structure of protein
- carboxyl group (-COOH)
- amino group (-NH2) and H attached to C atom
- variable group R
Functions of proteins
- enzymes
- carrier proteins transport molecules across membranes
- antibodies
- structural proteins support cells and tissues
- transport proteins(hameoglobin)
- contractile proteins enable muscles to contract
Peptide bond
- by condensation reaction
- H2O is removed using OH from COOH group and H from the amino group of another amino acid.
Dipeptide
Two amino acids joined together.
Tripeptide
3 amino acids joined together
Polypeptide
Made of many amino acids joined together.
Proteins have 4…
structural levels.
Primary structure determines…
the eventual shape of the protein, hence its function
-peptide bonds
Primary structure
The particular amino acids contained in the chain and the sequence in which they are joined.
Secondary structure
Hydrogen bonds form between the amino acids in the chain between the O of -CO- group of one amino acid and the H of the -NH- group of the amino acid four places ahead.
Secondary structure due to hydrogen bonds…
coil into an alpha helix or fold into a beta sheet.
Hydrogen bonds are easily broken by…
high temperatures and pH changes.
Tertiary structure
Way in which a protein coils up to form a precise 3-D shape.
Tertiary structure is held in these shapes by…
bonds between amino acids in different parts of the chain.
In tertiary structure more bonds…
form due to interactions between R-groups of the polypeptide chain.
(Tertiary structure)For proteins formed from a single polypeptide chain…
this is the final 3D structure of the protein.
Bonds in tertiary structure
- hydrogen
- ionic
- disulfide
- weak hydrophobic interactions
Hydrogen bond
Between strongly polar groups
e.g. -NH-, -CO- and -OH groups
Ionic bonds
Between ionised amine (NH3+) groups and carboxylic acid (COO-) groups.
Can be broken down by pH changes.
Disulfide bonds
Between cysteine molecules
Strong covalent bonds
Can be broken down by reducing agents.
Weak hydrophobic interactions
Between non-polar R groups. Interactions are weak but groups tend to stay together as they are repelled by watery environment.
Quaternary structure
Made up of several polypeptide chains held together. It is how different chains are put together.
Hydrogen bonds are found in…
Secondary and tertiary
Ionic bonds are found in…
tertiary
Disulphide are found in
tertiary
Hydrophobic and hydrophilic interactions are found in
tertiary
Quaternary structure depends on the…
tertiary structure of the individual polypeptides, so it is influenced all these types of bonds.
