Proteins

Question 1

explain initiation in translation

Answer 1

Initiation
Ribosome binds to the start codon (AUG) on mRNA

The first tRNA, carrying methionine (Met), pairs with AUG

Question 2

explain elongation in translation

Answer 2

Ribosome moves along the mRNA

tRNAs bring amino acids that match the codons

The ribosome links amino acids with peptide bonds, forming a growing chain

Question 3

explain termination in translation

Answer 3

ribosome reaches stop codon, completed pp is released and folds into functional protein

Question 4

what are the 2 things that make up a ribosome?

Answer 4

large subunit (50S) small subunit (30S)

Question 5

what site does mRNA binding occur at?

Answer 5

30S

Question 6

p site

Answer 6

peptidyl-tRNA site, tRNA binds to growing peptide chain

Question 7

A site

Answer 7

aminoacyl-tRNA, incoming aminoacyl-tRNA binds new amino acid

Question 8

E site

Answer 8

exit site for empty tRNA to leave ribosome

Question 9

where does initiation start?

Answer 9

starts with binding 30S to correct site on mRNA (start codon)

Question 10

what is the initiator amino acid?

Answer 10

methionine / Met, binds to start codon (AUG)

Question 11

how is initiation complex formed?

Answer 11

50S binds to 30 S subunit

Question 12

Q: Why do cells need to make polypeptides of defined length and sequence?

Answer 12

A: To ensure proteins have the correct structure and function necessary for cellular processes

Question 13

Q: What are the key components required for translation (protein synthesis)?

Answer 13

A:

Machinery: Ribosome

Raw materials: Aminoacyl-tRNAs

Instruction tape: mRNA`

Question 14

Q: What defines the association of codons with anti-codons?

Answer 14

A: The genetic code, which specifies how triplet codons in mRNA match with tRNA anti-codons to direct amino acid addition.

Question 15

Q: Why must proteins be processed and targeted after translation?

Answer 15

A: To ensure proper folding, modification, and transport to correct cellular locations for functional activity.

Question 16

Q: What specific mutation causes sickle cell anemia?

Answer 16

A: A missense point mutation in the HBB gene, where the codon GAG (glutamic acid) is changed to GTG (valine) at the 6th position of the β-globin chain in hemoglobin.

Question 17

Hydrogen Bonds

Answer 17

Form between a hydrogen atom and an electronegative atom (like O or N).

Important in α-helices and β-sheets (secondary structure).

Question 18

Ionic Bonds (Salt Bridges)

Answer 18

Form between oppositely charged side chains (e.g. Lys⁺ and Glu⁻).

Question 19

Hydrophobic Interactions

Answer 19

Nonpolar side chains cluster away from water in the protein’s interior.

Drives protein folding by minimizing contact with the aqueous environment.

Question 20

Van der Waals Forces

Answer 20

Weak attractions between all atoms when they are very close together.

Question 21

Q: What is the primary structure of a protein?

Answer 21

A: The sequence of amino acids in a polypeptide chain, held together by peptide bonds.

Question 22

Q: What is the secondary structure of a protein?

Answer 22

A: Local folding into α-helices and β-pleated sheets, stabilized by hydrogen bonds between backbone atoms.

Question 23

Q: What is the tertiary structure of a protein?

Answer 23

A: The overall 3D shape of a single polypeptide, stabilized by hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.

Question 24

Q: What is the quaternary structure of a protein?

Answer 24

A: The structure formed when two or more polypeptide chains (subunits) come together, held by similar interactions as in tertiary structure.

Question 25

Q: What is the general formula for an amino acid?

Answer 25

A: A central carbon (C) bonded to: an amino group (–NH₂) a carboxyl group (–COOH) a hydrogen atom a variable side chain (R group)

Question 26

Q: How is a peptide bond formed between amino acids?

Answer 26

A: A condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing water (H₂O) and forming a C–N bond.

Question 27

Q: What are proteins?

Answer 27

A: Polymers of amino acids (polypeptides) with a defined length and sequence.

Question 28

Q: How do proteins fold in solution?

Answer 28

A: They fold into unique 3D structures with hydrophobic cores and hydrophilic surfaces.

Question 29

Q: What is a protein domain?

Answer 29

A: An independently folding unit of a protein that can evolve, function, and exist independently of the rest of the protein.

Question 30

Q: How do proteins recognize and bind other molecules?

Answer 30

A: Via specific binding sites involving multiple weak interactions like hydrogen bonds and hydrophobic contacts.

Question 31

Q: How is haemoglobin’s structure related to its function?

Answer 31

A: Its quaternary structure allows cooperative oxygen binding and release.

Question 32

Q: How is the structure of membrane proteins related to their function?

Answer 32

A: They have hydrophobic regions that embed in membranes, allowing signal reception or transport.

Question 33

Q: How is the structure of fibrous proteins like collagen related to their function?

Answer 33

A: Their triple helix structure gives strength and flexibility, ideal for connective tissues.

Question 34

structure of antibodies

Answer 34

2 heavy and 2 light chains, joined by disulfide bridges, chains have variable and constant regions

Question 35

membrane protein structure

Answer 35

part exposed to membrane is hydrophobic, part exposed to outside is hydrophilic

Question 36

disulfide bonds

Answer 36

strong covalent links formed between the sulfur atoms of two cysteine amino acids in proteins.