3.1.4.1 GENERAL PROPERTIES OF PROTEINS Flashcards
What are proteins made out of?
Amino acids held together by peptide bonds
What determines a proteins function?
- sequence
- type and number of amino acids
What are amino acids and how many of them are there?
- monomers of proteins
- 20 amino acids found in proteins common to all living organisms
What is the general structure of an amino acid?
A central carbon atom bonded to:
- an amine group -NH2
- a carboxylic acid group- COOH
- a hydrogen atom
- an R group
What is an R group on an amino acid?
The only difference between amino acids and
How is a peptide bond formed?
- A hydroxyl (-OH) is lost form the carboxylic group of one amino acid and a hydrogen atom is lost from the amine group of another amino acid
- The remaining carbon atom from the first amino acid bonds to the nitrogen atom of the second amino acid
What kind of reaction is the formation of a peptide bond?
Condensation reaction
What are dipeptides?
Formed by the condensation of two amino acids
What are polypeptides?
Formed by the condensation of many (3 or more) amino acids
What are the four levels of protein structure?
- Primary
- Secondary
- Tertiary
- Quaternary
Describe the structure of a primary level of protein structure:
Order of amino acids in a polypeptide chain
Describe the structure of secondary level protein structure:
B- sheet
Folding alpha helixes
Describe the structure of a tertiary level protein:
B-sheets fold up to become 3D
Can be globular of fibrilous
Describe the structure of a quaternary level protein:
Association of two or more polypeptide charges and non- protein groups, to form a 3D structure
What type of bonds are in a primary level protein?
Peptide bonds
What type of bonds are in a secondary level protein?
Hydrogen bonds
What type of bonds are in a tertiary and quaternary level protein?
Ionic forces, disulphide bridges, hydrogen bonds, London forces
Where do the bonds form in a primary level protein?
Between amine and carboxylic groups of amino acids
Where do bonds form in a secondary level protein?
Resides of amine and carboxylic groups in the chain of amino acids
Where do bonds form in a tertiary and quaternary level protein?
Between R groups- type of bond/ IM force depends in properties of R group
Example of a globular protein?
Haemoglobin
Example of a fibrous protein?
Collagen
Why is it possible to form millions of different proteins?
20 amino acids- can form in loads of different orders
Are globular proteins soluble in water?
Yes
Are globular proteins soluble in water?
Yes
Why are globular proteins being soluble good?
They can be easily transported around around organisms involved in metabolic reactions
Do globular proteins have specific shapes?
Yes due to the folding of the protein due to the interactions between the R groups and therefore have specific shapes
Do globular proteins have specific shapes?
Yes due to the folding of the protein due to the interactions between the R groups and therefore have specific shapes
Why are the specific shapes of globular proteins good?
Enzymes can catalyse specific reactions and immunoglobulins can respond to specific antigens
What is a conjugated protein?
Contains a prosthetic group- haemoglobin contains haem
What are fibrous proteins?
Long strands of polypeptide chains that have cross-linkages due to hydrogen bonds
Do fibrous proteins have a structure?
They have little or no tertiary structure
Are fibrous proteins soluble or insoluble in water?
Insoluble due to the large number of hydrophobic R groups
Shape of fibrous proteins:
Long strands
Function of fibrous proteins:
Structural
Examples of fibrous proteins:
Collagen, keratin, myosin
Function of globular proteins:
Functional/ physiological
Example of globular proteins:
Haemoglobin, enzymes
