7.3 : Translation

Question 1

what occurs during the activation?

Answer 1

1) a specific amino acid & ATP bind to tRNA-activating enzyme –> bind –> amino acid is activate, causing the hydrolysis of ATP & the bonding of AMP.
2) tRNA specific to amino acid binds to the active site –> amino acid - AMP complex formed & a specific tRNA molecule is recruited.
3) amino acid binds to the attachment site on tRNA –> AMP released
4) activated tRNA and the attached amino acid are released from the enzyme & can be reused. = ‘charged’ tRNA produced.

Question 2

what happens after the activated tRNA & the attached amino acid is released from the enzyme?

Answer 2

they go to the ribosome, where protein synthesis takes place (three sites where tRNA interact = A,P,E site)

Question 3

what occurs in the A site?

Answer 3

a codon of incoming mRNA binds to a specific tRNA-amino acid complex through the tRNA anticodon (complementary base pairing)

Question 4

what occurs in the P site?

Answer 4

amino acid attached to the tRNA is condensed with the growing polypeptide chain –> formation of a peptide linkage (condensation) between adjacent amino acids.

Question 5

what occurs in the E site?

Answer 5

tRNA leaves the ribosome –> it’s amino acid (that was attached) is added to the growing protein chain –> continues until ‘stop’ codon is reached.

Question 6

what are the roles of ribosomes in 1) the cytoplasm and 2) the RER?

Answer 6

1) cytoplasm : for intracellular use of proteins
2) RER : for extracellular use of protein
- -> signal recognition attached to ribosome on RER –> secreted outside the plasma membrane = transported in tiny vesicles that contain the polypeptides –> these fuse/synthesise with the plasma membrane (subsequent secretion), then the polypeptide is released outside of the cell & goes where it is required.

Question 7

what is bioinformatics?

Answer 7

Storage, analysis and manipulation of biological information via computer science

Question 8

what is the proteome?

Answer 8

entire set of proteins expressed by the genome of an organism.

Question 9

what is the genome?

Answer 9

individually unique genetic information (hence proteome of individuals will be unique)

Question 10

what do amino acids with polar residual groups have? why are these important? what does this cause in the plasma membrane?

Answer 10

-have hydrophilic properties
-they are built into proteins in important positions –> which influence the properties & functioning of proteins in cells.
-cause a hydrophilic channel to form in the plasma membrane , which allow hydrophilic molecules to pass through (makes the surface of the protein hydrophilic & exposed to cytosol)
(polar amino acids = found at surface of water soluble proteins)

Question 11

what do amino acids with non- polar residual groups cause in the plasma membrane?

Answer 11

cause proteins to be embedded in the membrane as the bulk of the protein (hydrophobic) is compatible with the hydrocarbon (hydrophobic) tail of phospholipids in the membrane.
(non-polar amino acids = found at centre of water soluble proteins)

Question 12

what are examples of functional proteins & their roles?

Answer 12

• structural : collagen strengthens bones, skin and tendons
• movement : myosin (muscle fibres) causes contraction of muscles
• transport : haemoglobin transports oxygen from lungs to other tissues
• defence : immunoglobin acts as an antibody

Question 13

what is the difference between fibrous and globular proteins? exmaples?

Answer 13

FIBROUS :

• in the tertiary structure, a long and much coiled chain is formed.
• long & narrow
• insoluble
• collagen, keratin

GLOBULAR :

• in the tertiary structure, they take up a spherical structure.
• highly soluble in water
• enzymes, hormones (insulin)