B1.2 Proteins Flashcards
What are proteins? What are their main functions?
Organic compounds made of amino acids arranged in linear chains.
- Growth and repair
- Metabolic reactions (enzymes)
- Transport
- Maintain pH and fluids
- Energy store
- Hormones
Monomer of protein? How many are there? What are the two sub types? How does this affect diet?
Amino acids
20 amino acids
- non-essential can be synthesized
- essential need to be acquired through food
Veganism and vegetarianism can be dangerous if your aren’t getting the nutrients you need (essential amino acids).
Structure of an amino acid:
CHON:
NH3 - CH - C=O
R OH
Amine group, R group and carboxyl group
Where does protein synthesis occur?
How are amino acids joined? What bond do they form between them? What is another name for a protein?
In the ribosomes
Condensation reactions
Peptide bonds
Polypeptide = many
Dipeptide = two
What properties can an R group have? How does this affect the peptide chain?
- polar or non-polar
- hydrophilic or hydrophobic
- positive or negative charge
- can contain sulphur/cysteine (disulphide bridges)
This effects the folding of the protein, its structure and therefore its function.
Creates diversity in protein form and function.
What controls the protein being made? How?
Sequences of amino acids are determined by genes and DNA.
What is the primary structure of a protein?
A linear chain/sequence of amino acids.
It determines the folding/protein being made based on the order of the amino acids and the R groups.
It is non-functional
What is the secondary structure of a protein?
Alpha helixes or Beta pleated sheets
Form from hydrogen bonds between amine and carboxyl group.
Non functional
What is the tertiary structure of a protein?
The 3D folding of a protein (depends of primary sturcture and aa sequence)
- polar/hydrophilic on the outside
- non-polar/hydrophobic on the inside
- cysteines form di-sulphide bridges
- ionic bonds form between + and -
Folding is important for enzymes
What bonds can be made between amino acids in a protein?
- covalent / peptide bonds
- hydrogen bonds
- ionic bonds
- disulphide bridges
What is the quaternary structure of a protein?
A tertiary structure protein joined with another molecule:
Non-conjugated:
- protein + protein
Conjugated:
- protein + other molecule
Examples of conjugated and non conjugated proteins:
Conjugated:
- Haemoglobin
Non-conjugated:
- insulin, collagen
- enzymes (most)
Types of proteins + example:
Fibrous (collagen, keratin, elastin)
Globular (insulin, haemoglobin, hormones)
Properties of fibrous proteins:
- insoluble
- structural (support and strength)
- less sensitive to change (pH, temp, etc.)
Properties of globular proteins:
- can be soluble
- functional
(enzymes, transport, antibodies) - more sensitive to changes
