Lecture 2

Question 1

Myoglobin and hemoglobin structure

Answer 1

Haemoglobin: total 4 subunits, 2 alpha and 2 beta. Each contains 8 alpha-helices

Myoglobin: one subunit

Question 2

What AA in hemoglobin chain?

Answer 2

histidine

Question 3

What are the 4 structures of protein?

Answer 3

Primary, secondary, tertiary and quaternary

Question 4

What is primary structure?

Answer 4

amino acid sequence

Question 5

What is secondary structure?

Answer 5

folding as a result of hydrogen bonding

Question 6

What is tertiary structure

Answer 6

Secondary folding caused by interactions within the polypeptide and its immediate environment

Question 7

What is quaternary structure?

Answer 7

the relationships between individual subunits

Question 8

What are the forces that hold the protein together?

Answer 8

Covalent bonds (peptide bonds + sulphide bonds)
Ionic bonds (between carboxyl and amino group)
Hydrogen bonds
hydrophobic interactions
Van der waals forces

Question 9

What are the 3 models of DNA replication

Answer 9

1. semiconservative model
2. conservative model
3. dispersive model

Question 10

In DNA replication, what is the purpose. of DNA pol I?

Answer 10

remove RNA stretches

Question 11

During DNA replication, which enzymes unwind DNA?

Answer 11

Helicase and gyrase

Question 12

In DNA replication, which enzyme ensures that there are no gaps in DNA fragents?

Answer 12

DNA ligase

Question 13

What are the 3 domains of living things?

Answer 13

Eubacteria, Archaebacteria, Eukarya

Question 14

What are the six kingdoms of life on earth?

Answer 14

EUbacteria, Archaebacteria, protista, fungi, plantae, animalia

Question 15

Physical description of a bacteria

Answer 15

1. No nucleus
2. flagellum is made of flagellin, for motility
3. pili is made of pilin, for adhesion
4. capsule made of polysaccharides to access to the membrane

Question 16

What does gram -ve bacteria have that gram +ve bacteria doesn’t?

Answer 16

-lipopolysaccharide
-porin
-outermembrane
-periplasmic space
-lipoprotein

Question 17

What test to distinguish between gram +ve and gram -ve bacteria?

Answer 17

Gram stain

1. crystal violet applied
2. grams iodine applied
3. alcohol wash applied
4. red dye applied (gram -ve bacteria gain red color)

Question 18

Why are prokaryotes indispensable to human health?

Answer 18

Fixation - reducing N2 to NH3

Symbiosis:
1. cellulose degrading bacteria in cattle
2. bacteria producing vitamin K and B12 in human colon

Question 19

Archaebacteria

Answer 19

they are not quite bacteria-like
Cell walls lack peptidoglycan
They live in extreme conditions:
Dead Sea (unusual salt composition)
Deep Sea Vents (>100ºC, >200 atmosphere)

Presence of unusual lipids isoprenes

Question 20

Difference between prokaryotes and eukaryotes

Answer 20

Prokaryotes:
-Unicellular
-one circular chromosome
-no nucleus and internal organelles
-generally no introns

Eukaryotes:
-unicellular and multicellular
-multiple linear chromosomes
-nucleus, ER, golgi apparatus, mitochondria
-most genes have introns

Question 21

How does transcription begin?

Answer 21

RNA polymerase with its sigma subunit slides along the DNA until it recognizes the promoter and binds to it. Upon binding, the sigma subunit begins unwinding the DNA double helix, exposing the template strand to be transcribed.

Question 22

Ribosomal RNA

Answer 22

Ribosomal RNA : four different RNA pieces in the gigantic RNA-protein complex ribosome where protein synthesis takes place; 28S, 18S, 5.8S and 5S.

Prokaryotes do not have the 5.8S rRNA.

Question 23

Regulatory RNA

Answer 23

play regulatory roles in controlling the protein contents of a cell

Question 24

For secreted and membrane bound proteins, how are they brought to Rough ER?

Answer 24

Signal recognition particle (SRP) recognizes the signal on the peptide and binds to it. It brings the peptide to rough ER and docks it there

Question 25

What is smooth ER for?

Answer 25

The SER are responsible for the synthesis of lipids, carbohydrates, and steroid hormones, among other functions

Question 26

What is the function of golgi apparatus?

Answer 26

1. Packaging and distribution of molecules within a cell as well as secretion. 2. addition of short carbohydrate chains, making them “glycoproteins

Question 27

Explain how protein secretion occurs?

Answer 27

1. Vesicles containing proteins buds from the RER diffuses through the cell, and fuses to the cis face of the Golgi 2. The proteins are modified and packaged into vesicles for transport. 3. The vesicles may travel to the plasma membrane, releasing its contents to the extracellular environment.

Question 28

What AA stops the membrane bound protein from threading through?

Answer 28

Arginine

Question 29

What are the additional features in mRNA of secreted proteins and type 1 membrane proteins?

Answer 29

For secreted proteins: There is a leader peptide region (before the coding region) with many hydrophobic amino acids Membrane anchoring sequence of hydrophobic amino acids followed by arginine or lysine

Question 30

How does prokaryotic transcription and translation differ from that of eukaryotic?

Answer 30

In prokaryotes, transcription and translation are coupled and not separated.

Question 31

What is the 5' cap composed of?

Answer 31

The 5' cap consists of a modified guanine nucleotide it plays diverse roles in mRNA processing, stability, translation initiation, and overall gene expression regulation.

Question 32

What is the consensus sequence found at the 5' splice site of intron and 3' splice site of the intron?

Answer 32

5' : GU 3' : AG

Question 33

How does splicing occur?

Answer 33

1. snRNA forms base-pairs with 5'end of intron 2. spliceosome and looped intron 3. exons spliced and spliceosome dissembles