30 and 31 - Nutrition and Hormones Flashcards Preview

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Flashcards in 30 and 31 - Nutrition and Hormones Deck (55)
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What are three types of hormones (based on derivatives, eg. polypeptides)?

Amino acid derivates (catecholamines)


What three broad functions that hormones carry out through receptor signalling?

- Maintenance of homeostasis across organism
- Response to external stimuli
- Follow cyclic programs, sleep wake cycle, menstrual etc.


What do endocrine cells do?

Secrete hormone molecules into the bloodstream to trigger target cells any distance away


What do paracrine cells do?

Secrete hormone molecules to peripheral cells, only affecting tissue around them


What do autocrine cells do?

Secrete hormone molecules to bind to receptors on same cell. They affect themselves.


What are four peripheral endocrine organs?

Gastrointestinal tract
Adrenal cortex
Adrenal medulla


What three types of cells are there in the pancreas and what do they secrete?

- alpha cells secrete glucagon
- beta cells secrete insulin
- delta cells secrete somatostatin


What 5 hormones does the gastrointestinal tract secrete?

- Gastrin and secretin (acid production)
- Cholecystokinin (gallbladder emptying)
- Gastric inhibitory peptide (GI motility)
- Ghrelin (appetite stimulant)
- GLP (crosstalk with pancreas)


What 3 hormones does the adrenal cortex secrete? Which type of hormone are they?

Adrenal cortex steroids
- Glucocorticoids
- Mineralocorticoids
- Sex steroids


What 2 hormones does the adrenal medulla secrete? What type of hormones are these?

Adrenal Medulla Catecholamines
- Epinephrine
- Norepinephrine


What are the 5 types of hormon receptors?

- Ionotropic receptors
- G-protein coupled receptors
- Cytokine receptors
- Receptor tyrosine kinases
- Nuclear hormone receptors


What are ionotropic receptors?

Gated ion channels, used by neurotransmitters often.


Which hormones use G-protein coupled receptors?

MANY, over 800 different receptors.
- Adrenergic (epinephrine)
- Glucagon
- Used in vision, taste and smell


What do cytokine receptors do?

- Respond to cytokines (Intracellular signalling molecules)
- Respond to tumour necrosis factor, type of cytokine that causes apoptosis
- Respond to interleukins (immune signalling from leukocytes)


What do receptor tyrosine kinases respond to?

- Insulin
- Growth factors


What do nuclear hormone receptors do?

Class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules. In response, these receptors work with other proteins to regulate the expression of specific genes, thereby controlling the development, homeostasis, and metabolism of the organism. Can bind to DNA.
- Respond to membrane-permeable ligands
- Vitamins A and D
- As well as some fatty acids and bile acids


What is slow signal transduction?

Involves altered protein synthesis by affecting gene expression. Takes minutes to hours.


What is fast signal transduction?

Intracellular signalling pathway that leads to altered protein function (often allosterically), leading to altered cytoplasmic machinery. This is quick and takes seconds to minutes


What are the steps of the G-protein cycle?

1. Ligand binds to receptor
2. G-protein activated by GTP exchanging with GDP
3. Alpha subunit of G protein with GTP bound (active) dissociates and activates adenylate cyclase
4. Adenylate cyclase synthesizes cAMP from ATP as long as GTP-Gα is bound.
5. cAMP activates protein kinase A, which causes cellular effects.


How is a G-protein coupled receptor signal terminated?

1. G protein has GTPase activity, it hydrolyzes GTP to GDP and inactivates itself.
2. Additional regulatory proteins can hydrolyze the GTP and shorten the signal
3. cAMP is hydrolyzed and removed by phosphodiesterase
4. The receptor is endocytosed and can be degraded (fewer receptors on suface leads to less signal)


What type of hormone receptor is the insulin receptor?

Receptor tyrosine kinase, similar to other growth factor receptors.
- Dimer


What is the structure of a receptor tyrosine kinase?

It is a dimer
- There are two α-subunits in the extracellular space
- Each α-subunit is attached to a β-subunit, which is intracellular and contains the tyrosine kinase domains.
- Ligands (like insulin) bind to the α-subunits


What are the steps of insulin receptor activation and termination? (receptor tyrosine kinase activation)

1. Insulin binds to the α-subunits of the receptor
2. Phosphorylation of tyrosine on receptor and IRS (insulin receptor substrate)
3. Cellular response

1. Dephosphorylation of receptor and IRS by a tyrosine phosphatase
2. Internalization of receptor

PIP2 and PIP3 are special lipids in the membrane that are used in receptor tyrosine kinase signalling


What are the 11 water-soluble vitamins?

- ascorbic acid (vitamin C)
- thiamine (vitamin B1)
- riboflavin (vitamin B2)
- Niacin (vitamin B3)
- Biotin
- Pantothenic acid
- Folic acid
- Vitamin B12
- Pyridoxine (vitamin B6)
- Pyridoxal
- Pyridoxamine


What are the four fat soluble (water insoluble) vitamins?

- Vitamin A (retinal, beta-carotenes)
- Vitamin D (cholecalciferol)
- Vitamin K (phylloquinones, menaquinones)
- Vitamin E (tocopherols)


What is the non-B complex, water soluble vitamin?

Ascorbic acid (vitamin C)


What are the 5 B-complex and water soluble, energy releasing vitamins?

- Thiamine (vitamin B1)
- Riboflavin (vitamin B2)
- Niacin (vitamin B3)
- Biotin
- Pantothenic acid


What are the two hematopoietic, B-complex, water soluble vitamins?

- Folic acid
- Vitamin B12


What is the only vitamin that is non B-complex and ALSO water soluble?

Ascorbic acid (vitamin C)

Vitamin A, D, K and E are all fat soluble (water insoluble). The rest of the water soluble vitamins are B-complexes


What types of vitamins can accumulate in the body and therefore have an upper limit for daily intake?

Fat soluble vitamins can accumulate in the body.