Proteins Flashcards
Unit 2: Biomolecules
What do proteins contain?
Carbon, Hydrogen, Oxygen, NItrogen and sometimes Sulphur
What are proteins composed of?
They are cmoposed of long chains of monomers called amino acids
What do each amino acids contain?
They contain a central alpha carbon linked to an amine group, carboxyl group, and variable (R) group and a hydrogen atom.
What do amino acids differ by?
Amino acids differ in the composition of their variable side chain (R)
How are dipeptide formed?
Two amino acids joined by condensation
How are polypeptide formed?
They are formed by more amino acids being added to the dipeptide
What catalyzes the condensation reactions?
Ribosomes
What is a peptide bond?
Bond linking amino acids together (C-N bond, -NH2 of one amino acid and -COOH of the other)
Define essential amino acid
Acids that animals cannot synthesize (make) and must be obtained from diet
Define non-essential amino acids
Acids that can be made by animals using pathways that transform one amino acids into another
What can shortage of one or more essential amino acids in diet cause?
They can prevent the production of specific proteins
Ribosome’s function in amino acids?
Ribosomes can join amino acids between any pair of the 20 different amino acids
Functions of R groups?
R groups stabilize the 3D shape of proteins
Define denaturation
When there is a conformational change in a protein, they don’t normally return to their original structure, it’s usually permanent
What can cause denaturation?
Heat, due to vibrations in the molecule
Extreme pH
What do R groups determine?
They determine the vehicle properties of amino acids
Define Conformation
3D shape
What decides which level the proteins conforms to
It’s decided by it’s amino acid structure
What do each proteins conforms into determine
It deterines the fuction of the protein?
What are four levels of protein structure?
Primary Structure
Secondary Structure
Tertiary Structure
Quaternary Structure
Primary Structure
Sequence of amino acids
Formed by peptide bonds
Determines/controls the other levels
Secondary Structure
Folds/turns of amino acid sequence upon themselves
Pattern of H bonds between amine and carboxylic groups creates the secondary structure
H bonds give stability
Fibrous proteins
Tertiary Structure
3D folding pattern due to side chain interactions
Polypeptide folds and coils (complex)
Caused by interactions between R groups
Tertiary shape is very important for function
Globular proteins
Quaternary Structure
Interaction between multiple polypetides
Sometimes prosthetic (part that is not an amino acid) groups involved
Classified as fibrous or globular
Define Alpha helix
The structure when the chain coils
Define beta-pleated sheet
The structure when teh chain pleats
Is C=O polar or non-polar
Polar
Is N-H polar or non-polar
Polar
Where are H bonds formed
H bonds are formed readily along a polypeptide chain
Functions of H bonds in polypeptide chain
Although individually H bonds are weak, there are so many that it helps to stabilize
Types of bonds in tertiary structure
Ionic bonds - between + and - R groups
Hydrogen bonds - between polar R groups
Disulfide bridges
Hydrophobic interactions
What can amino aicds in proteins broadley be catagorized as?
They can be catagorized as being either hydrophobic (non-polar) or hydrophilic (polar/charged)
Example of polar and non-polar amino acids on tertiary structure of globular proteins
Globular proteins need to be soluble in water so the outside/surface amino acids are hydrophilic where they contact water and center is hydrophobic
What do the arrangement of polar and non polar amino acids affect?
Tertiary structure, they help them stabilize and ensure position is maintained that suits the proteins function
Define non-conjugated proteins
They have only polypeptide subunits
Example of non-conjugated proteins
Insulin is 2 polypeptides joined by a disulphide bridge
Define conjugated proteins
Have one or more non-polypeptide chains called prosthetic groups, in addition to teh polypeptides
Example of conjugated proteins
Haemoglobin - 4 polypeptide chains and each with a haem group. Increasing the diversity of the protein, allowing more function
Define fibrous proteins
Contain elongated polypeptides that lack folding or alpha helices
Example of fibrous proteins
Collagen, rope like structure giving high tensile strength
Define Globular proteins
Rounded shape due to folding, intricate shape stabilized by R group bonds, exact shape closely related to its function
Example of globular proteins
Enzymes, receptor sites.
Only insulin hast he right shape to connect to the insulin receptor
What does the connection between insulin and insulin receptor cause
They cause signals to be sent that open channels to move glucose into cells
