Week 9 Proteins and their synthesis

Question 1

What is a peptide bond?

Answer 1

A covalent bond of the amino
end (NH2) of one amino acid with the carboxyl end (COOH) of another amino acid. One water
molecule is removed during the reaction.

Question 2

What is the primary protein structure?

Answer 2

Linear sequence of amino acids

Question 3

Secondary structure

Answer 3

local regions of the protein fold together, aloha or beta sheets - non covalent interactions

Question 4

Tertiary structure

Answer 4

3D shape of the entire polypeptide
Each enzyme has an ACTIVE SITE into which its substrate(s) fit

Question 5

Quaternary structure

Answer 5

4 subunits

All come together to form a functioning protein

Held together by hydrophobic interactions, forces, H bonds
these are weak bonds

Question 6

What are the two general types of proteins

Answer 6

Globular: compact and round, play functional roles
Fibrous: long and narrow, play structural roles

Question 7

The features of the genetic code

Answer 7

1. Degenerate (amino acid can be encoded for with more than one set of codons)
2. codon of 3 nucleotides make up an amino acid
3. Non overlapping
4. Continuous
5. cotains 64 codons, enough for 20 amino acids

Question 8

What do tRNAs do?

Answer 8

Link mRNA codons to specific amino acids and birng them to the ribosome

Question 9

In tRNA, the amino acid attachment site is always

Answer 9

5’CCA3’, at the very 3’ end

Question 10

Amino acids are attached to tRNA by enzymes called

Answer 10

aminoacyl-tRNA-synthetases
- have 2 binding sites

Question 11

What is charged tRNA

Answer 11

tRNA with an amino acid on it

Question 12

2 proofreading steps of aminoacyl-tRNA-synthetases

Answer 12

1. Amino acid and ATP
2. tRNA and amino acid

Question 13

The wobble position and wobble base pairing

Answer 13

the third position of the codon, allows tRNAs to recognize more than one codon

Question 14

Key sites of interaction in the ribosome

Answer 14

A site: binds incoming aminoacyl-tRNA whose anti codon matches the codon
P site: binds the growing peptide chain
E site: exit releases tRNA back into the cell
Decoding center: in the 30S subunit (ensures only tRNAs with matching anticodons enter)
Peptidyl transferase center: in the 50S subunit where the peptide bond is made

Question 15

How is the initiator codon properly placed in the P site for translation to begin?

Answer 15

The shine dalgarno sequence that precedes the start codon base pairs with the 16S rRNA in the 30S subunit of the ribosome
This correctly positions AUG in the P site where the initiator tRNA will bind

Question 16

How is translation stopped?

Answer 16

Release factor proteins recognize stop codons, and will bind in the A site. This recruits a water molecule to come in and release the peptide chain

Question 17

What is a nonsense suppressor mutation?

Answer 17

A mutated allele of the tRNA gene that allows the tRNA to recognize the stop codon in the mRNA an synthesis continues

Question 18

stop codons are recognized by ____, not the anticodon

Answer 18

amino acids in RF proteins

Question 19

List the posttranslational modifications of amino acid side chains

Answer 19

1. addition of chemical groups to amino acids
2. addition of complex molecules to amino acids
3. modifications of amino acids
4. additions of polypeptides to amino acids
5. cleavage of peptide bonds (pre-protein inactive to active protein)

Question 20

the three types of enzymes involved in chemical modifications

Answer 20

writers, erasers, readers (strutural proteins)

Question 21

Phosphorylation

Answer 21

Adding of a phosphate group to cataluze rapid conversion of signals. - like a light switch, makes proteins active or inactive

Question 22

Ubiquitination

Answer 22

Targets proteins for degredation (Ubiquitin serves as a signal for proteasome to consume it down into its constituents), can add polypeptides