Topic 2 - Hormone Biosynthesis and Receptors

Question 1

Transcription

Answer 1

Is the 1st step of gene expression, where a particular segment of DNA is copied into RNA
- by the enzyme RNA polymerase

Question 2

Splicing

Answer 2

Is the editing of the precursor mRNA. Introns are removed and exons are joined together

Question 3

Translation

Answer 3

mRNA is decoded by a ribosome, outside the nucleus, to produce a specific amino acid chain or ploypeptide

Question 4

Promoter

Answer 4

Is a region of DNA that initiates transcription of a particular gene

Question 5

Enhancer

Answer 5

Is a short region of DNA that can be bound by proteins to increase the likelihood that transcription of a particular gene to occur
- Usually referred to as TF (transcription factor)

Question 6

What do insulin and prolactin synergistically stimulate?

Answer 6

Beta-casein mRNA translation by cytoplasmic polyadenylation

Question 7

What kind of protein is beta- casein?

Answer 7

Milk protein

Question 8

What enzyme transcribes genes to mRNA?

Answer 8

RNA polymerase 2

Question 9

What does transcription initiation require?

Answer 9

Many general and specific transcription factor protein binding promoters

Question 10

Where does transcription start site usually occur?

Answer 10

Just after a TATA box

Question 11

What do activators do?

Answer 11

Then bind enhancer DNA sequences and increase transcription – hormone influence

Question 12

What do repressors do?

Answer 12

They bind silencer DNA sequences and decrease transcription – hormone influence

Question 13

How do chromatin remodelling complexes weaken histone DNA interactions and DNA folding?

Answer 13

They use ATP-driven conformational change

Question 14

HATs

Answer 14

Histone acetylases

Question 15

What do HATs do and whats the result?

Answer 15

They add acetyl groups to histones resulting in more open conformation

Question 16

HDACs

Answer 16

Histone deacetylases

Question 17

HRE

Answer 17

Hormone response element

Question 18

Hormone response element

Answer 18

Is a short sequence of DNA within the promoter of a gene that is able to bind a specific hormone receptor complex and therefore regulate transcription

Question 19

Does HRE influence RNA polymerase directly for indirectly?

Answer 19

Indirectly

Question 20

What do HRE influence?

Answer 20

Histone acetyl transferases

Question 21

What do hormones open up, and why?

Answer 21

The open up proteins to enhance transcription

Question 22

RNA processing steps (6)

Answer 22

1. Splicing introns, leaving exons
2. Cap 5’ end of RNA
3. Poly-A tail on 3’ end
4. Mature mRNA exported
5. Translation starts
6. Translation continues until stop codon is reached

Question 23

Protein synthesis steps (7)

Answer 23

1. Ribosomes translate mRNA; NAC binds
2. Signal sequence targets protein to signal recognition particle
3. SRP docks with receptor on ER and translocation channel forms
4. Translation & cotranslational modifications
5. Cleavage signal sequence peptide
6. Chaperones fold and control quality
7. Ribosomal subunits recycled; channels close; folded protein chain in ER

Question 24

What kind of energy drive protein synthesis? (2)

Answer 24

ATP and GTP hydrolysis

- But also need a functional mitochondria and respiration

Question 25

NAC

Answer 25

Nascent chain associated complex

Question 26

SRP

Answer 26

Signal recognition particle

Question 27

What makes up pre-hormone (non-functional; in ER)? (3) Example?

Answer 27

- single peptide + hormone + cryptic peptide | - Eg) Hepcidin pre-prohormone 85AA

Question 28

What makes up prohormone (non-functional; in ER)? (2) Example?

Answer 28

- hormone + cryptic peptide | - Eg) Hepcidin prohormone 60AA

Question 29

What is a mature hormone (functional; in Golgi)? Example?

Answer 29

- Processed hormone | - Eg) mature hepcidin 25AA

Question 30

How are hormones secreted outside of the cell?

Answer 30

Vesicular transport

Question 31

What does brefeldin A do?

Answer 31

It inhibits protein transport from the ER to the golgi body indirectly by preventing association of coat COP-II protein to the golgi membrane

Question 32

What are 3 types of coat proteins?

Answer 32

1. COP-I 2. COP-II 3. Clathrin

Question 33

What are coat proteins used?

Answer 33

In vesicular traffic in the secretory and endocytic pathways

Question 34

How can you monitor when using coat proteins?

Answer 34

By using fluorescents

Question 35

Coat associated protein - I

Answer 35

Mediates retrograde transport from the trans- to the medial- to the cis-Golgi/cis-Golgi network to the rough ER --> Bring back mature proteins that arent being released

Question 36

Coat associated protein - II

Answer 36

Mediates transfer of vesicles from the rER to the cis-Golgi /cis-Golgi network. --> Bring forwards motion in the golgi where they can be released, fused with lysosomes and broken down or recycled

Question 37

Clathrin

Answer 37

Mediates transfer of vesicles that bud from the trans-golgi netork and the plasma membrane and that then fuse with late endosomes

Question 38

COP

Answer 38

Coat associated protein

Question 39

Vesicular secretion steps (6)

Answer 39

1. Sorting hormones for secretion 2. COP and vesicle formation 3. Budding and trafficking (v/t-SNARE) 4. Uncoating 5. Docking 6. Fusion to target membrane

Question 40

What energy source drives vesicular secretion? (1)

Answer 40

GTP hydrolysis

Question 41

What 2 things influence the half-life of mRNA?

Answer 41

1. 5'cap | 2. Length of 3'poly A tail

Question 42

What factors affect protein stability? (4)

Answer 42

1. Glycosylation 2. Phosphorylation state 3. Metabolic degradation 4. Internalization (presence of proteolytic enzymes)

Question 43

How are vascular and non-vascular hormone secretion transported across the plasma membrane?

Answer 43

Directly

Question 44

What does the rER produce, and what is it used in?

Answer 44

- Produces oxidases | - Used in sER and are controlled by HRE that change the amount of P450