Biochem - Inter and Intra Signalling

Question 1

Which hormones have intracellular receptors?

Answer 1

Steroids, thyroid hormones, retinoic acid, 1 alpha 25 dihydroxycholecalciferol

Question 2

Name an example of a catecholamine hormone and its function.

Answer 2

adrenaline - synthesised in adrenal medulla, increases pulse rate, smooth muscle contraction glycogenolysis in liver & muscle

Question 3

Describe relative homologies of domains in the steroid receptor superfamily.

Answer 3

From highest to lowest - heat shock protein binding site, DNA binding site, steroid binding site & N- terminal transcriptional activation domains

Question 4

What are zinc fingers?

Answer 4

Located on receptor, bind to bases and phosphate on DNA and forms dimers - forms grooves which match the DNA

Question 5

What is the hormone response element and where are they found?

Answer 5

2 identical sequences of 6 bases, each sequence bound by one of the two hormone receptor complexes located in the dimer.
They are located in the promoter region of a gene

Question 6

How do intracellular receptors down regulate in response to high hormone exposure?

Answer 6

1. Direct repression of receptor gene via binding hormone receptor complex to a responsive element in the promoter region of the gene (receptor down-regulates its own gene)
2. Activation of the expression of a gene coding for enzyme which catalyses the degradation of the receptor mRNA

Question 7

Which enzyme expression is enhanced by cortisol in the liver?

Answer 7

phosphoenolpyruvate carboxykinase, an enzyme involved in gluconeogenesis

Question 8

Which enzyme converts cortisol to cortisone in cells requiring aldosterone binding?

Answer 8

11-beta hydroxysteroid dehydrogenase

Question 9

What is mineralocorticoid excess syndrome?

Answer 9

hypertension & hyperkalemia due to congenital deficiency of the kidney form of 11-beta hydroxysteroid dehydrogenase/ eating too much liquorice

Question 10

what are the types of hormones with plasma membrane receptors?

Answer 10

catecholamines, & peptide/protein hormones

Question 11

What are the differences between endocrine, paracrine and autocrine hormone action?

Answer 11

Endocrine - hormones via blood stream act on effector organs far away
Paracrine - hormones released to act on effector organs close by
Autocrine - hormones released to act on cell that released them

Question 12

What are the two types of hormone?

Answer 12

Hydrophobic, which has intracellular receptors

Hydrophillic, which has intercellular receptors

Question 13

What are steroid hormones derived from?

Answer 13

Cholesterol

Question 14

What are thyroid hormones derived from?

Answer 14

Tyrosine residues that are part of the protein thyroglobulin

Question 15

How do hydrophobic hormone operate?

Answer 15

Regulate gene expression

Question 16

What do heat shock protein sites do?

Answer 16

Tether the receptors within the cytoplasm until the hormone binds, which displaces the HSPS, allowing the complex to go to the nucleus

Question 17

How can hormone receptors activate gene expression?

Answer 17

When there is a synergistic interaction between the hormone receptor complex dimer when it binds to the response element, and the transcription factor, which enhances transcription of the gene

Question 18

How can hormone receptors repress gene expression?

Answer 18

1) The hormone receptor complex binds to the response element and displaces the transcription factor
2) the hormone-receptor complex dimer binds to a protein like Ap 1, which is a positive regulator of transcription. This inhibits Ap1, repressing gene expression