7. Protein Folding, Processing And Sorting

Front 1

What is the definition of a protein?

Back 1

Unbranched polymers of the 20 common amino acids held together with polypeptide bonds with a specific 3D shape and function

Front 2

Why is protein structure important?

Back 2

Structure determines functionality

Front 3

What is a polypeptide?

Back 3

Unstructured, nonfunctional chain

Front 4

What is an unstructured, nonfunctional chain?

Back 4

A polypeptide

Front 5

What is the primary structure of a protein?

Back 5

Amino acid backbone of the protein

Front 6

What functional groups does a protein have?

Back 6

1. Amino group (NH2)

2. Carboxyl group (C=OOH)

3. Side chain (R group)

Front 7

What makes amino acids different?

Back 7

The side chain

Front 8

How is a peptide bond formed?

Back 8

Removing OH from the carboxylic acid of one AA and an H from the amine of the other (joins the C-N together)

Front 9

What are the two primary secondary structures?

Back 9

1. A helix: Primary structure coiled into a spiral structure stabilised by hydrogen bonds

2. B sheets: Primary chain zig-zags to form a "pleated" sheet w. adjacent strands H-bonded together

Front 10

How do secondary structures form?

Back 10

Maximising hydrogen bonding between polypeptide backbone (O from COOH and H from N-H)

Front 11

What does satisfying bonding in protein structures do?

Back 11

Ensure protein is stable and non-active parts cannot react inappropriately

Front 12

What is the tertiary structure of a protein?

Back 12

Overall 3D shape of globular protein resulting from interactions between AA side chains

Front 13

What bonds are present in tertiary protein structure?

Back 13

1. Hydrophobic collapse

2. Van der Waals interactions

3. Hydrogen bonds

4. Ionic bonds

5. Disulphide bridges

Front 14

What is hydrophobic collapse, why does it occur and what holds the result together?

Back 14

"Hiding" \hydrophobic (nonpolar) side chains in centre of protein during folding. Held together with VDW interactions.

Front 15

What are hydrogen and ionic bonds between in the tertiary protein structure?

Back 15

1. H-bonds between non-polar side chains

2. Ionic bonds between + and - charged SCs

Front 16

What is the disulfide bridge?

Back 16

Covalent bonds between the sulphur of two cysteine monomers which have sulfhydryl groups (¬SH) on their sidechains

Front 17

How are DNA and proteins inherently linked?

Back 17

DNA sequence governs RNA sequence
RNA sequence governs amino acid sequence
AA sequence governs protein sequence
Protein sequence governs protein structure
Protein structure governs functions

Front 18

Do all proteins remain in the cytoplasm?

Back 18

No. They can also be secreted, bound to the membrane or go to specific organelles.

Front 19

Where are membrane anchored and secretory proteins initially translated?

Back 19

Cytoplasmic ribosomes

Front 20

Describe further processing of membrane-bound and secreted proteins

Back 20

1. Signal peptide emerges at ribosome surface

2. SP recognised by signal recognition particle

3. SRP targets ribosome to ER m'brane receptors

4. Signal sequence inserts into ER membrane

5. Nascent chain translocated across

Front 21

What is the signal peptide made of?

Back 21

First 5-10 amino acids translated by ribosome

Front 22

What on the ER membrane surface recognises the signal recognition particle?

Back 22

SRP receptor protein