3.1.4 Proteins Flashcards
What are the monomers that make up proteins called?
Amino acids
What is the formula for the amine group in an amino acid molecule?
NH2
What is the formula for the carboxyl group in an amino acid molecule?
COOH
What is the R group?
It represents a carbon containing side chain
How many amino acids are common in all organisms?
20
How many essential amino acids are there?
8
What is the name of the reaction that bonds amino acids?
Condensation
What type of bond is formed during the condensation reaction between two amino acids?
Peptide bonds
What is a dipeptide?
The protein formed by the condensation of two amino acids
What is a polypeptide?
The protein formed by the condensation of many amino acids
Name a property of a functional protein
Contain one or more polypeptide
What are the 6 elements found in proteins?
Carbon Hydrogen Oxygen Nitrogen Sulphur Phosphorus
What protein catalyses reactions?
Enzymes
What protein transports substances around the body?
Haemoglobin
What protein controls movement of the body?
Actin and myosin in muscles
Which proteins function is cell recognition?
Antigens
What transport across cell surface membranes?
Intrinsic protein channels
Which proteins form connective tissue and structural components of the body?
Keratin
Collagen
Which proteins protect against invasion by foreign bodies?
Antibodies
Which proteins are responsible for hormonal control?
Hormones (eg insulin)
Why is there an endless variety of protein structures?
The 20 different amino acid monomer units can be assembled in any order
What do you call the variable group of an amino acid?
R group
What is an optical isomer?
Mirror image molecules made from alpha and beta amino acids
Amino acids can act as both acids and bases, what is this called?
Amphoteric
Why are amino acids described as amphoteric?
The amino group can accept a hydrogen which makes it act as a base whereas the carboxyl group donates hydrogen which makes it act as an acid
Which group of an amino acid acts as a base?
Amino group
Which group of an amino acid acts as an acid?
Carboxyl group
What is removed when peptide bonds are formed?
Water
What is primary structure?
The sequence of amino acids which determines its shape and function
What is secondary structure?
Polypeptide chains can twist into a 3D shape, forming an alpha helix or beta pleated sheet
What is tertiary structure?
Precise 3D structure of protein formed by the coiling of secondary proteins
What is quaternary structure?
Large proteins can have many polypeptide chains associated together
Non protein groups can join to polypeptides (prosthetic group)
Having both makes a quaternary structure
What bonds are involved in primary structure?
Hydrogen bonds
What bonds are involved in secondary structure?
Hydrogen bonds
What bonds are involved in tertiary structure?
Hydrogen bonds
Ionic bonds
Disulphide bridges
What bonds are involved in quaternary structure?
Hydrogen bonds
Ionic bonds
Disulphide bridges
Describe hydrogen bonding.
Weak
Strong in large numbers
Describe ionic bonding.
Weak
Between any carboxyl and amino groups that are not involved in forming peptide bonds
Easily broken by changes in pH
Describe disulphide bridges.
Covalent
Strong
Describe the test for proteins.
Biuret test
Add equal parts sodium hydroxide and solution X to a test tube
Add a few drops of copper sulphate and mix
Purple/lilac indicates a protein is present (detects peptide bonds)
No change indicated protein is not present
What do you call a non-protein group starched to polypeptides?
Prosthetic group
How do hydrogen bonds hold successive coils in an alpha helix?
Fibres are formed by the bonds between the NH group in one amino acid and the CO group of another
Describe beta pleated sheets.
Hydrogen bonds between each parallel chain
It is a flat structure that folds
It has great strength (eg silk)
What are the two types of protein?
Globular- metabolic functions
Fibrous- structural materials
Describe globular proteins?
Rounded molecules Alpha helix’s and beta pleated sheets Unstable Irregular primary structure Conservative sequence and length between species/individuals Soluble (suspension)
Describe fibrous proteins?
Parallel strands
Lots of beta pleated sheets OR lots of alpha helixes
Stable
Regular, repetitive primary structure
Variable sequences and length between species/individuals
Insoluble
