The Cellular Basis of Hormone Action

Question 1

Endocrine System Def.

Answer 1

Secretes hormones. Coordinates slower but long acting responses. Eg growth, reproduction and behavior

Question 2

Hormone Def.

Answer 2

Biochemical messenger, released from endocrine gland. Impacts gene expression and state of proteins

Question 3

Feedback Def.

Answer 3

How hormones are regulated in endocrine system

Question 4

Negative Feedback Def.

Answer 4

Hormone conc. is kept in a narrow range

Question 5

Positive Feedback Def.

Answer 5

Amplifies hormone response

Question 6

Endocrine Signalling Def.

Answer 6

Hormones act mainly on distant sites but can also act locally (both paracrine and autocrine)

Question 7

Paracrine Def.

Answer 7

Target cells are adjacent to secreting cells (hormone travels)

Question 8

Autocrine Def.

Answer 8

Hormone acts on secreting cell (hormone doesn’t travel)

Question 9

Factors that receptors shape and frequency on cell membrane influence

Answer 9

Type of substrate and potency of substrate on cell

Question 10

Hormone Formation (outline)

Answer 10

Stimulus received + processed by endocrine gland. Hormones secreted into blood. Carried to receptors with specific binding site

Question 11

Examples of hormones altering cell conditions

Answer 11

Opening closing membrane channels (permeability), gene activation/suppression (functional protein expression), enzyme activation/deactivation, secretory products (suppression/induction) , cell division

Question 12

Hormone Action (outline)

Answer 12

Receive stimulus, hormone secretion, receptor binding, tissue condition change and feedback

Question 13

2 Main Factors Effecting Cellular Response Degree

Answer 13

How hormone’s delivered and receptor’s/tissue’s status

Question 14

Hormone Delivery Considerations

Answer 14

hormone synthesis/secretion rate, target cell proximity, transport proteins dissociation constants (hydrophobic hormones), inactive to active conversions and liver/kidney clearance rate

Question 15

Receptor/ Tissue Status Considerations

Answer 15

Receptors density + state of occupancy, receptor’s hormone affinity and receptor desensitization

Question 16

Hormone Classification Categories

Answer 16

Chemical composition, solubility, binding site location, receptor basis

Question 17

Chemical Compositions of Hormones

Answer 17

Steroids, peptides and glycoproteins

Question 18

Solubility of Hormones

Answer 18

Hydrophobic vs Hyrdrophillic

Question 19

Binding site locations

Answer 19

Intracellular vs cell surface

Question 20

Receptor bases

Answer 20

G-protein + second messengers and kinase

Question 21

Steroid Hormone Outline

Answer 21

Derived from lipid cholesterol, hydrophobic (non water soluble) and thus bind to transport proteins in blood. Eg testosterone

Question 22

Amine Hormones Outline

Answer 22

Derived from trytophan and tyrosine (amino acids). Can be hydrophillic or hydrophobic. Eg thyroxine

Question 23

Peptide/ Protein Hormones

Answer 23

Multiple amino acids forming chain. Peptides = short chain. Protein is polypepptide chain

Question 24

Hydrophobic (Lipophilic) Hormones Outline

Answer 24

Non-water soluble. Bind to transporter proteins in circulation

Question 25

Hydrophillic (/lipophobic) hormone outline

Answer 25

Water soluble. Travel independently in circulation

Question 26

How hydrophilic hormones bind to cell

Answer 26

Extracellular. Can’t move through lipid bi-layer. Creating a signalling cascade controlled by a second messanger

Question 27

How hydrophobic hormones bind to cell

Answer 27

Intracellular. Can diffuse across lipid bi-layer. Binds to DNA segment causing transcription

Question 28

Steps of hydrophobic hormone binding

Answer 28

Diffusion, Binding, Translocation, Hormone Response Elements, delta expression

Question 29

Hydrophobic Hormone Response Elements (HRE)

Answer 29

Receptor with hormone binds to HRE on DNA

Question 30

Delta Expression Def.

Answer 30

Binding derives change in mRNA and resulting protein expressions

Question 31

Hormone Response Elements

Answer 31

Regions of DNA, consensus sequence and close to initiation (transcription) siteHREs associate with activated receptor and nuclear receptor proteins. More complex

Question 32

Hydrophilic Hormones Outline

Answer 32

Binding, Intracellular Signaling, PKA activation and Phosphorylation

Question 33

How message from Hydrophilic crosses membrane

Answer 33

G-protein receptors

Question 34

Intracellular Signaling

Answer 34

G proteins activate adenylate cyclase (converts ATP to cAMP(cyclic adenosine mono phosphate)). Propagates signal through cell

Question 35

PKA (protein kinase A) Activation

Answer 35

cAMP targets and activates protein kinase A within cytosol

Question 36

Phosphorylation

Answer 36

PKA triggers selective phosphorylation of cellular proteins eg nuclear transcription factors

Question 37

Phosphodieterase Outline

Answer 37

Activated by protein kinase A. Deactivates cAMP forming negative feedback loop for phosphorylation

Question 38

Examples of 2nd messangers

Answer 38

cAMP, calcium, cGMP

Question 39

Ligand-Activated Protein Kinase Activity

Answer 39

Aggregate and phosphorylate eachother at specific tyrosine residues in cytoplasmic tail. Propagate signals by autophosphorylation (no 2nd messenger)

Question 40

Hormone Biological Processes Example

Answer 40

Gene transcription, transporter channels, protein translocation (hydrophilic only), protein modification (hydrophilic only)

Question 41

Insulin Receptor

Answer 41

Ligand-activated, tyrosine-specific protein kinase

Question 42

Type 2 Diabetes Cause

Answer 42

Insulin receptor develops insensitivity results in deficient signaling and thus an increase in blood glucose levels

Question 43

Graves’ Disease Cause

Answer 43

Autoimmune. Antibody binds to thyroid stimulating hormone receptor causing increase thyroid hormone production (hyperthyroidism)

Question 44

Enzyme Linked Immuno-Sorbent Assay (ELISA) Outline

Answer 44

Measure hormone concentrations in blood. The darker the colour in the say = the higher the conc. of hormone. Used in diagnosis and pregnancy tests. Can be quantative (exact conc) or qualative (yes/no)