L25 Hormones & Intercellular Communication Flashcards
There are 4 main categories of intercellular communication, these are:
- GAP junctions
- Synaptic
- Paracrine and autocrine
- Endocrine
Under the classical definition, the endocrine system comprises of cell with endocrine glands which release hormones. However, it is now known that…
Many tissues can release hormones (not just endocrine glands)
Hormone
Chemical messenger synthesised by specialised cells secreted into the blood
Hormones have a high affinity. Thus they are effective…
At low concentrations!
Which of the following is not a property of hormones?
a) can be synergistic
b) can be permissive
c) can be polycistronic
d) can be antagonistic
c) can be polycistronic
Polycistronic described mRNA transcripts containing more than one gene (i.e. in prokaryotes)
If a hormone is permissive, the presence of one hormone is required…
For another to work
Competitive hormones compete for the same…
Receptors
There are 3 main classes of hormone…
- Steroids
- Peptides
- Amino Acids
Steroid hormones are synthesised by modification of…
Cholesterol
Steroid hormones are lipophilic, so they ( cannot / easily ) cross cell membranes
Easily
Because they are lipophilic, steroid hormones are ( easy / difficult ) to store
Difficult
This is why they are produced on demand and released immediately after synthesis
Because they are lipophilic, steroid hormones require:
a) Carrier protein in the blood
b) Secondary messenger systems
c) Storage molecules inside the cell
d) Synthesis in an inactive form (preprohormone)
a) Carrier protein in the blood💉
Steroid hormones characteristically have:
a) rapid but long lasting effects
b) slow but long lasting effects
c) rapid but transient effects
d) none of the above
b) Slow but long lasting effects
This is because they affect gene expression, which in turn must then influence protein production. This is a relatively slow process. 🐢
The most abundant class of hormones are…
Peptides
Peptide hormones are synthesised from…
Amino acids
Peptide hormones bind to cell surface receptors because they are…
Hydrophilic and so don’t cross cell surface membranes easily
Peptide hormones are synthesised as an inactive form prior to release, known as…
Preprohormone
Peptide hormones bind to cell surface receptors, which activate…
Secondary messenger systems to cause their effects
Amino acid hormones are synthesised from:
a) Peptides
b) Tyrosine
c) Phenylalanine
d) Glutamine
e) Cholesterol
b) Tyrosine
Amino acid hormones are:
a) Lipophilic
b) Hydrophilic
c) Can be either
d) None of the above
c) Can be either
If they are lipophilic they bind intracellular receptors, whereas the hydrophilic types bind cell surface receptors.
Which hormone types can be hydrophilic?
a) Amino acid and steroid
b) Amino acid and peptide
c) Peptide and steroid
d) Only peptides
b) Amino acids and peptides
Peptide hormones are hydrophilic and so are some amino acids hormones!
Amino acid hormones are:
a) Stored allowing instant release
b) Produced on demand and not stored
c) Synthesised from cholesterol
d) Stored but slow to release
a) Stored allowing instant release
Hormone release can be (4)…
- Continuous
- Pulsatile
- Circadian
- From exocytosis on stimulus
An example of a hormone with circadian release pattern is…
Melatonin
