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Module 102: Molecular cell biology > Proteins > Flashcards

Flashcards in Proteins Deck (17)
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1
Q

Primary structure of a protein.

A

Composed of a chain of amino acids maintained by peptide bonds.

C-terminus is the start of the chain.

N-terminus is the end of the chain.

2
Q

Secondary structure of a protein

A

Composed of the primary folding of the polypeptide chain into an alpha helix or beta pleated sheet.

Maintained by hydrogen bonds.

3
Q

Alpha helix

A
  • Composed of a polypeptide chain coiled into a helical structure
  • Hydrogen bonds are formed between amine and carboxyl group 4 amino acids down.
  • This causes an outward turn every 3.6 amino acids and the sidechains to face outward.
4
Q

Beta pleated sheet

A
  • Polypeptide chain laterally packed into beta strands.
  • Hydrogen bonds are formed between the amine and carboxyl group of neighboring amino acids.
  • Causes the side chains of the amino acids to be above and below the beta sheets.
  • The sheets can run anti-parallel or parallel.
5
Q

Non-essential vs essential amino acids

A

Non essential: amino acids that are made in the body or obtained from breaking down other amino acids.

Essential amino acids:
Amino acids that are not made in the body and so can only be obtained from food.

6
Q

Protein domain

A

Globular unit of a protein from the same polypeptide chain.

Each domain is separated by an inner chain of the same polypeptide chain.

Each domain has a specific DNA sequence that performs a certain function even though it is from the same polypeptide.

7
Q

Signaling sequence in proteins

A

A sequence of 15-60 amino acids located in the polypeptide chain that signals for where the protein should go after synthesis.

8
Q

Creutzfelat-Jakob disease

A

(Also known as mad cow disease)

  • Neurodegenerative disease caused by mis-folding of prion proteins in the brain.
  • This causes subacute spongiform encephalopathy
9
Q

How does CFTR mutation affect protein structure?

A

The deletion of phenylamine at amino acid 508 causes an impaired Cl- transporter.

10
Q

Structures found in the protein that is not an alpha helix of beta pleated sheet.

A
  • Loops
  • Barrel: Where the first and last part of the strand closes
  • Random coils.
11
Q

R-group interactions

A
  • In an aqueous environment:
    Hydrophilic parts of the protein are external and exposed to the environment.

Hydrophobic side chains are internal, does not interact.

- Interactions included:
Hydrogen bonds
Van der Waal forces
Electrostatic attractions
Covalent bonds, Disulphide bonds
12
Q

Assisted folding of proteins

A
  • Certain proteins assist the folding of proteins are molecular chaperones:

Do so without altering the protein shape

Prevents protein aggregation and repairs incorrectly folded proteins.

Heat shocking proteins: Stabilises protein folding in response to elevated temperatures

13
Q

Quaternary structure of a protein

A

R-group interactions between more than one polypeptide chains to form sub-units.

14
Q

Disulphide bonds

A

Covalent bond formed between Sulphur atoms attached to a polypeptide.
Found in cysteine.

This is an oxidation reaction:
Causes proteins with this bond to be located extracellular as the cytosol has reducing conditions.

15
Q

Folding funnel

A

Idea that proteins will always fold into the configuration that gives then the lowest free energy.

Proteins will fold until entropy is very low, which allows a stable molecule so that the bonds do not move.

16
Q

How can protein activity be regulated.

A

Controlling the amount present:
Controlling the synthesis
Proteasomes
Controlling secretion

Controlling the activity of the protein:
Post-translational modification
Further interactions with other molecules: i.e cofactors

17
Q

Proteasome

A

Protein complex that degrades protein that is in excess or that has folded incorrectly.

Causes proteolysis, which breaks down the peptide bonds in proteins.