Ribosome + Protein Synthesis + ER

Question 1

What is the structure of a ribosome

Answer 1

1. Small subunit - decodes genetic information from mRNA
2. Large subunit - catalyses formation of peptide bonds between amino acids to form a polypeptide chain
   - 4 binding sites = one for mRNA and three (A,P,E) for tRNA

Question 2

What do rRNA molecules do in a ribosome

Answer 2

Direct the catalytic steps of protein synthesis

Question 3

What are ribosomes made out of

Answer 3

1. Proteins
2. rRNA

Question 4

What are tRNA molecules used for

Answer 4

Adaptors to add each amino acid in the correct sequence

Question 5

What is protein synthesis driven by

Answer 5

Elongation factors, using GTP hydrolysis

Question 6

What happens after a ribosome reaches a stop codon during translation

Answer 6

1. Release factor binds to the ribosome - terminating translation and the polypeptide is released
2. The folding of the newly synthesized proteins is assisted by chaperones
3. Control mechanisms destroy any incorrectly folded proteins

Question 7

Do all genes code for proteins?

Answer 7

• No
• For minority of genes, final product is the RNA molecule itself

Question 8

Can genes code for more than one copy of a protein

Answer 8

• Yes
• Many identical RNA copies can be made from the same gene
• Genes can be transcribed and translated with different amounts of proteins

Question 9

What are the 3 RNA types and what do they do

Answer 9

1. mRNA - carry the coding sequences for protein synthesis called transcripts - goes from DNA to cytoplasm
2. rRNA - forms the core of cell’s ribosomes
3. tRNA - carry amino acids to the ribosomes during protein synthesis
   - Each class of RNA has its own polymerase - polymerase I, II, and III