Hormonal communication Flashcards
hormone solubility
water soluble (hydrophillic) and lipid soluble (lipophillic)
what are hyfrophillic hormones
peptide
proteins
amines
-catecholamines
-indoleamines
what are the lypophillic hormones
thyroid- catecholamines
steroids
hat are hydrophilic hormones and what are they typically composed of?
peptides or proteins, which are chains of amino acids. Short chains are referred to as peptides, while long chains are considered proteins. Hydrophilic hormones also include amines derived from amino acids, such as catecholamines and indoleamines.
What are catecholamines and where are they derived from?
Catecholamines are hydrophilic amines derived from the amino acid tyrosine. They are produced in the adrenal medulla and include hormones such as epinephrine (adrenaline) and neurotransmitters like dopamine.
hat is an example of an indoleamine, and where is it produced?
Melatonin
produced in the pineal gland. Indoleamines are derived from the amino acid tryptophan.
What distinguishes lipophilic hormones from hydrophilic hormones in terms of solubility?
: Lipophilic hormones are soluble in lipids and have low solubility in water, whereas hydrophilic hormones are water-soluble. This solubility difference affects how these hormones are processed, transported, and how they exert their effects on target cells.
What types of hormones fall under the category of lipophilic hormones?
ipophilic hormones include steroid hormones and thyroid hormones. Steroid hormones, such as cortisol from the adrenal cortex and sex hormones like testosterone and estrogen, are derived from cholesterol. Thyroid hormones are also classified as lipophilic and are derived from the amino acid tyrosine.
How are catecholamines and thyroid hormones similar in terms of their derivation, and how do they differ in terms of solubility?
Both catecholamines and thyroid hormones are derived from the amino acid tyrosine. However, catecholamines are hydrophilic and soluble in water, while thyroid hormones are lipophilic and soluble in lipids.
What role does hormone solubility play in its function?
The solubility properties of a hormone determine how it is processed by endocrine cells, how it is transported in the blood, and how it exerts its effects on target cells. Hydrophilic hormones travel freely in the bloodstream, while lipophilic hormones need carrier proteins for transport due to their low water solubility.
hat are steroid hormones derived from, and what are some examples?
neutral lipids derived from cholesterol.
cortisol from the adrenal cortex and sex hormones such as testosterone in males and estrogen in females.
Why do lipophilic hormones need carrier proteins in the blood?
ow solubility in water, so they cannot dissolve freely in the aqueous environment of the blood. Therefore, they require carrier proteins to be transported through the bloodstream to their target cells.
What are some functions of hormones secreted by the adrenal medulla and pineal gland?
adrenal medulla, such as epinephrine (adrenaline), are involved in the fight-or-flight response, increasing heart rate and blood flow to muscles. The pineal gland secretes melatonin, which regulates sleep-wake cycles and circadian rhythms.
steps in hormonal hydrophillic processing
- large prehormones (precursor proteins) synthesised by ribosomes on rough ER
- smooth ER packages proteins and hormones into transport vessicles that bud off and migrate to golgi complex
- during journy to golgi complex the preprohormones are modified to active hormones
- transport vessicles from ER fuse with golgi to release their contents
- golgi complex packages the finished product into secretory vesicles and stored in cytoplasm until signal trigger secretion
- on signal secretory vessicle fuse with plasma membrane to release contents into blood via exocytosis
- lysosomes also bud off from golgi
What is the precursor for all steroid hormones?
Cholesterol
Why can steroid hormones not be stored in cells like peptide hormones?
They diffuse immediately through the plasma membrane after synthesis
How is the rate of steroid hormone secretion controlled?
By the rate of hormone synthesis
What happens to steroid hormones after they are synthesized?
They diffuse immediately through the plasma membrane and enter the bloodstream
What role do enzymes play in the synthesis of steroid hormones?
modify cholesterol to form steroid hormones
true or false Steroid hormones can be stored in steroidogenic cells for later use.
false
true or false
The adrenal cortex produces cortisol because it has the necessary enzymes for its synthesis.
true or false Steroid hormones can undergo further modifications in the blood to form more potent hormones.
true
The synthesis of steroid hormones is controlled by the rate of hormone release, not the rate of synthesis. true or false
false
What is the main difference between the secretion of steroid hormones and peptide hormones?
Steroid hormones are synthesized and immediately diffuse through the plasma membrane into the bloodstream, whereas peptide hormones are stored in cells and released when needed.
Explain why steroid hormones cannot be stored in cells.
Steroid hormones cannot be stored because they diffuse immediately through the plasma membrane once they are synthesized.
How does the synthesis of steroid hormones differ from the release of peptide hormones?
Steroid hormones are synthesized as needed and are not stored, while peptide hormones are pre-synthesized and stored in cells until needed for release.
What happens to steroid hormones after they are synthesized and secreted into the blood?
After synthesis, steroid hormones diffuse through the plasma membrane, enter the blood, and may undergo further modifications in the blood or other organs to become more potent or form different hormones.
Name one steroidogenic organ and explain its role in steroid hormone production.
Adrenal cortex: It synthesizes cortisol because it has the enzymes required for the conversion of cholesterol into cortisol.
What percentage of catecholamines circulate as free hormones?
50
Why are hydrophilic hormones not typically administered orally?
They are digested by protein-digestive enzymes in the digestive system
How do hydrophilic hormones typically induce effects within cells?
Via second-messenger pathways like cAMP or Ca2+
What is the primary method by which lipophilic hormones produce their effects?
Activating specific genes to produce new proteins
true or false Hydrophilic hormones are usually bound to plasma proteins for transport in the blood.
false
true or false Steroid hormones can be taken orally because they are not affected by digestive enzymes.
true
true or false Lipophilic hormones mainly produce effects by changing existing intracellular proteins rather than by activating gene expression.
false
true or false Insulin is an example of a hormone that must be administered via injection because it is not absorbed effectively through the digestive system.
true
true or false he presence of hormone receptors varies depending on the solubility of the hormone.
true
What is the significance of protein binding in the transportation of hydrophilic hormones?
The significance of protein binding is not entirely clear, though it may help with hormone stability and prolonged circulation in the blood.
Why can steroid hormones be taken orally, while most other hormones cannot?
Steroid hormones (and thyroid hormones) can be taken orally because they are not digested by protein-digestive enzymes in the digestive system, unlike other hormones that are broken down.
What are the two main mechanisms by which hormones produce effects on their target cells?
Hydrophilic hormones alter pre-existing intracellular proteins via second-messenger pathways, while lipophilic hormones activate specific genes to produce new proteins.
How do hydrophilic hormones differ from lipophilic hormones in their method of action?
Hydrophilic hormones act through second-messenger pathways to alter pre-existing proteins, while lipophilic hormones act by activating gene expression, leading to the production of new proteins.
What is one example of a hormone that is administered through daily injections, and why is it administered this way?
Insulin is administered through daily injections because it is not absorbed effectively through the digestive system due to the presence of digestive enzymes.
describe hormonal mechanism of action using Gene stimulation to promote protein synthesis by lipophilic hormones:
- hormone diffuse through plasma membrane of target cell
- bind to specific receptor in cytosol or nucleus to form hormone- receptor complex
- complex translocate to nucleus to bind to DNA at attachment site (HRE)
- binding of complex to DNA activates specific gene within target cell
- each gene contains code of specific protein. code transcribed to mRNA
- mRNA leaves nucleus to enter cytoplasm where it binds to ribosomes
- mRNA directs synthesis of specific proteins according to DNA code in activated genes
- newly synthesised protein leaves ribosomes and processed into proper confirmation
- new protein produces target cells ultimate response to hormone
signal amplification- output is —– than input
greater
how does signal amplification lead to more molecules
extracellular chemical messanger bound to membrane receptor- 1 molecule
activated adenylyl cyclase- 10 mol
cyclic AMP- 1000 mol
activated PK- 1000 mol
phosphorilated- activated protein- 100000mol
products of activated enz- 10000000 mol
signal transduction pathway activated to ensure
Proper function
Growth
Survival
Reproduction
cells contain what built in pathway that triggers cell death
apoptosis
what is apoptosis
programmed cell death. components packaged into vessicles that are digested by scavvanger cells
role and function apoptosus
prevent lakage and damaging neighbor cells
control apoptosus
caspases are the product
apoptosis vs necrosis
programed vs traumatic
controlled vs not
vessicles vs rupture and release into ECM
WBC vs inflammatory response
how are hormonal receptors refulated
serve as links between extracellular first messsanger and intracellular second mesanger
- frequently regulated
Receptor number and affinity altered depending on circumstance
Eg. Chronic elevation of insulin in blood causes decrease in insulin receptors
name diseases linked to receptor malfunction or defect in signal transduction pathway
Defective receptors cause Laron dwarfism
Toxins released from bacteria causing whooping cough or cholera
Laron dwarfism
defective receotors
Abnormally short although normal growth hormone level, thus tissue does not respond normally to hormone
Contrasts usual dwarfism (growth hormone deficiency)
whoopiing cough
pertussis toxin prevents inhibition of adenyl cyclase
ensures continuously active 2nd-messenger pathway
cholera
toxin prevent G prtein from converting GTP to GDP
ensure continuously active G protein
The same hormone may have different effects on target cells that have:
Different receptors for the hormone
Different signal transduction pathways
Different proteins for carrying out the response
use epinepherine to explain how different receptors have different cell responses
alpha receptor leads to constriction of vessel and intestinal blood vessel\
beta recceptor lead to dialation of vessel- skeletal
use epinepherine to explain how different intracellular proteins have different cell responsenes
same receptor- beta and same hormone- epinepherine
skeletal muscle- vessel dialate
liver cell- glycogen break down and glucose released from cell
does hormone always have same effect in same species? give example
no- thyroid hormone- T4
how do pathways cross talk
