Proteins Flashcards
What are proteins also called?
Polypeptides/polymers
How are proteins structured?
Long chains of amino acids
What do all amino acids contain?
- carbon
- hydrogen
- oxygen
- nitrogen
What do many amino acids also contain?
Sulfur
How is an amino acid structured?
An amino group (NH2)
A central C with a H
A variable R group attached to the central C
A carboxyl group (COOH)
How many different R groups are there giving the same number of different amino acids?
20
What is the simplest amino acid?
Glycine: R=H
What is the the more complex amino acid example?
Cysteine- R=CH^2SH
What bonds amino acids?
Peptide bond
How is a peptide bond formed?
Condensation reaction
What do two amino acids combine to form?
A dipeptide
What groups does a peptide bond form between?
One amino acid’s carboxyl group and the other’s amino group.
Three or more amino acids joined by a peptide form what?
Polypeptide
What is the primary structure of a polypeptide?
A long chain of amino acids
What happens if the sequence changes due to DNA mutation in a primary structure?
The protein will be non-functional
What are the two secondary structures and how are they formed?
The polypeptide chain twists to form
- an alpha helix
- or a beta pleated sheet
What maintains the secondary structure’s shape?
Hydrogen bonds between the peptide bonds.
What make up proteins?
Amino acid monomers
What is a tertiary structure’s shape?
Secondary structure folded into a specific 3d shape
What 3 types of bonds hold together tertiary structure?
- Hydrogen bonds between R groups containing O- and H+
- ionic bonds between R groups containing oppositely charged ions.
- disulfide bonds between sulfur containing R groups. Very stable, occur least often.
What are hydrophobic interactions?
Interactions between two non-polar R gtoups. Within protein, amino acids with non polar R groups move away from aqueous environment to form hydrophonic centre at protein molecule interior.
How are quaternary formed?
2 or more polypeptide chains combined. Held by same bonds as tertiary.
What is an example of quaternary and what is it made up of?
Haemoglobin. 4 tertiary bonded together- 2 alpha and 2 beta chains
What are the two protein types and their functions?
Fibrous (structural)
Globular (biochemical)
What structure do fibrous proteins have?
Secondary
How are fibrous formed/structured?
Polypeptide chains twisted to form long strands
Are fibrous insoluble or soluble?
Insoluble- can’t dissolve
What is the structure of the fibrous protein collagen?
3 intertwined chains
What is the function of the fibrous protein collagen?
Main connective tissue in body, found in ligaments, tendons and cartilage
What is the fibrous protein keratin’s structure?
Two intertwined chains
What are keratin’s two functions?
- main component of hard structures such as hair, nails and hooves
- part of skin cells, preventing pathogen entry.
What structure do globular proteins have?
Tertiary or quaternary
Is globular soluble or insoluble?
Soluble
What are the possible biochemical functions of globular proteins? (4)
- Enzymes
- transport proteins such as haemoglobin and myoglobin.
- hormones- such as oestrogen and insulin.
- antibodies
What is denaturing?
If the bonds that maintain a protein’s shape are broken, the protein will stop working properly= denatured.
What factors can denature proteins?
Changes in:- -temp -pH -salt concentration (Specific conditions vary from protein to protein).
What effect does denaturing have on fibrous?
Loses structural strength
What effect does denaturing have on globular?
Becomes insoluble and inactive
What is the test for proteins?
Add biuret agent (copper sulfate and sodium hydroxide).
A change from pale blue to lilac/purple = positive.
