Cell signalling and receptors Flashcards
What are the types of signals that can be produced?
- Mechanical
- Biochemical
For a biochemical signal, what is required?
A ligand and a receptor
What is a signal ligand?
a small molecule that forms a complex with a macromolecule typically a receptor protein that results in a conformational change in the receptor that then generates a signal
Tell me 3 different forms of signal
- Contact- dependent signals
- Cell-matrix signals
- soluble signals; Autocrine, Paracrine, Endocrine
Tell me about Contact- dependent signals (juxtacrine)
- require interaction between membrane molecules on two cells
- cells must be touching
- signals are transmitted through cell membranes via protein or lipid componenets integral to the membrane of the emitting cells
Tell me about Cell-matrix signals
Provide some examples of them
- insoluble signalling molecules
examples;
a. Mesenchymal cells (neurons, muscle cells, fibroblast) are surrounded by a matrix
b. Chondrocyte cell surrounded by matrix (cartilage)
c. Cell-matrix interactions can be organised at focal contacts
Where is an epithelial cells matrix found?
Only on one side
Tell me about Autocrine signals
Provide some examples
They are secreted and affect the target cell itself via its own receptors
Examples;
1. Interleukin-1; a cytokine released by macrophages. effects neighbouring cells and the secreting cell “activating them”
2. Interleukin-2; is released by T lymphocytes on meeting an antigen and causes them to proliferate

Tell me about intracrine signals
provide an example
They are produced by and stay within target cells (a version of autocrine signalling)
Examples
- adipose tissue
- some steroid hormones have their receptors in the cell so can act as intracrine (and paracrine and endocrine signals)

Tell me about Paracrine signals
Provide some examples
These signals target cells in the vicinity of the emitting cell
They are localised signals
Examples
- Immune cells; neurotransmitters at synapses

Tell me some local mediators of paracrine signals which are released into the interstitual fluid
- Histamine
- TGFß
- Growth factors
- cytokines
Are chemical synapses- neuronal signals paracrine signals?
yes
Tell me about Endocrine signals
Provide an examples
They target distant cells by producing hormones that travel through the circulation to reach all parts of the body
Examples
- adrenalin
- thyroid stimulating hormone

Tell me some hormones and their concentration at low concentration in the blood/interstitual fluid
Thyroxine 0.09-20 pg/ml
Oestrodiol 20-400 pg/ml
Prolactin 3-15 ng/ml
What is 1pg in grams…
1 Pg = … g
1 pg= 1x10-12 g
Tell me about the affinity of hormone receptor binding
Has a far greater affinity (low Kd) compared to others
What are hormone receptors part of?
amplification cascades
Tell me some chemical classification of external messengers and examples for each
Gases: NO, CO, H2S, CO2.
Nucleic Acids: ATP, ADP and adenosine.
Fatty acid derivatives: Eicosanoid e.g. prostaglandins, thromboxanes, leukotrienes, PAFs.
Cholesterol derivatives: steroids
Amino acids and derivatives: glycine, glutamate, thyroid hormones, catecholamines- e.g. adrenaline
Peptides: e.g. TRH
Proteins: e.g. Insulin
What are gases produced by ?
specific enzymatic pathways
Tell me about the solubility of gases and what this allows them to do/ not to do
They are highly soluble in water and lipids
Can cross plasma membrane
can’t be stored
Are gases only made when they are needed ?
yes
What type of local effects do gases produce?
Paracrine and autocrine effects
What type of responses do they produce?
Generally, cause vasodilation and may have immunological effects
Tell me what nucleic acids function as paracrine signalling molecules
The purinergic nucleotides ATP/ADP and their nucleoside adenosine




















