Lipid Signalling Molecules Flashcards
Which of the following is NOT involved in the specificity of signal transduction?
A) Interactions between receptor and signal molecules
B) Location of receptor molecules
C) Structure of receptor molecules
D) Structure of signal molecules
E) Transmembrane transport of signal molecules by receptor molecules
Transmembrane transport of signal molecules by receptor molecules
Which of the following is not involved in signal transduction by the b-adrenergic receptor?
A) ATP B) Cyclic AMP C) Cyclic GMP D) GTP E) All of the above are involved
Cyclic GMP
What is a hormone?
Chemical produced from tissues that travel in the blood to distant tissue
What does paracrine mean?
- Cell produces a signal to induce changes in nearby cells
- Short-distance
- Paracrine messages/hormones
What does autocrine mean?
○ Cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the SAME cell
What does juxtacrine mean?
- Signalling that requires close contact (neighbor cells)
- Do not travel; no distance
- Immediate cells only
What does pheromone mean?
Secreted or excreted chemical factor that triggers a social response in members of the same species
What are the two types of signaling molecules? Give examples.
- Peptide (insulin)
- Lipids (estrogen, thyroid hormone)
What are the three types of lipids? How many categories are there?
- They are either structural, storage, or biologically active
- 8 categories
How do lipids usually act as signaling molecules?
Through nuclear receptors
What are precursors of inositol-phosphates?
Glycerophospholipids
The same lipid can form _______ metabolites leading to very _________ signalling cascades.
various, different
Where are sphingolipids found?
In the nervous system
How do sphingolipids differ from TG?
They have a sphingosine instead of glycerol
If X is an H in a sphingolipid, what is it? What does it do?
- Ceramide
- Stabilizes “lipid rafts”: islands on the cell membrane
What is the structure of sphingolipids?
- Sphingosine
- Fatty acids at the 2nd and 3rd carbon
- Hydrophilic domain at the 1st carbon
If X is phosphocholine in a sphingolipid, what is it? What does it do?
Sphingomyelin
How are sphingolipids involved in signaling?
- Sphingolipid (ceramide) stabilizes lipid rafts
- Lipid rafts are important for receptor dimerization
- Localization of signals
In what kind of signaling does receptor dimerization has to occur? What kind of lipid would you need?
- RTK signaling
- Ceramide (sphingolipid) - stabilizes lipid rafts
Which lipid determines blood groups?
- Glycosphingolipid
- When X is a carbohydrate in sphingolipids
How do glycosphingolipids determine blood groups?
- The type of sugar can form O, A, B, or AB antigens
- Structure of the sugar is determined by specific glycosyltransferases
Which lipid acts as paracrine factors?
Eicosanoids
How many carbons do eicosanoids contain?
20
Arachidonate is released from __________ by __________
glycerophospholipids by phospholipase A2
Arachidonate is the precursor for what? (2)
- Prostaglandins
- Thromboxanes
What are the two signaling mechanisms of prostaglandins?
- Smooth muscle contraction (labour)
- Regulates blood flow and body temperature
What is the signaling mechanism of thromboxanes?
Form platelets to reduce blood flow to the site of the blood clot
What are NSAIDs?
Nonsteroidal anti-inflammatory drug
How do NSAIDs work? Give an example.
- Inhibit cycloxigenase enzymes, which are necessary for the formation of both prostaglandins and thromboxanes
- Pain relief (Aspirin)
What is the signaling mechanism of leukotrienes?
Airway smooth muscle contraction (lung system)
How does Prednisome work?
- Inhibits phospholipase A2
- Used in astma, arthritis, organ transplantation
- Stops prostaglandins and thromboxanes
What is the common structure of sterol lipids?
- 4 rings
- Three are 6-carbon rings
- One is a 5-carbon ring
What is the precursor molecule for sterol lipids?
Cholesterol
How are sterol lipids carried in the blood?
By carrier protein
Which lipids act as hormones? What do they affect?
- Sterol Lipids
- Mainly affect cellular transcription (gene expression)
What are the specific receptors for the following sterol lipids: A) Testosterone B) Cortisol C) Aldosterone D) Estradiol
A) AR
B) GR
C) MR
D) ER
Explain how vitamin D gets activated.
- 7 dehydrocholesterol is cleaved by UV light in the skin, which turns into cholecalciferol (vitamin D3) - inactive
- Liver: becomes 1,25-dihydroxycholecalciferol
- Kidney: becomes 1,25-dihydroxyvitamin D3 - Active
What does vitamin D regulate? How?
- Through the vitamin D nuclear receptor (VDR)
- Calcium absorption (intestine)
- Calcium excretion (kidneys)
- Calcium storage (bone)
What does vitamin D3 deficiency lead to?
Rickets
Which lipids act as hormones and pigments?
Prenol lipids
B-carotene is the precursor for what? (3)
- Vitamin A1 (retinol)
- 11-cis-Retinal
- Retinoic acid
Where is 11-cis-Retinal found?
Found in rods and cones in the eyes
What is 11-cis-retinal converted to when it is hit by light? What is that responsible for?
- All-trans-retinal
- Sends a neuronal signal to the brain
What is retinoic acid converted from? What does it do?
- From 11-cis-Retinal
- Sends a hormonal signal to epithelial cells (nuclear receptors)
What does vitamin A deficiency lead to?
Growth retardation, night blindness, etc.
What is used to treat acne? What is it derived from?
- Tretinoin (Retin-A)
- Derived from retinol
What are the nuclear receptors involved in prenol lipid signaling?
- Retinoic acid receptor (RAR)
- Retinoid X receptor (RXR)
Which lipids act as cofactors?
Tocopherols (prenol lipids)
What are the 5 tocopherols?
- Vitamin E
- Vitamin K
- Warfarin
- Ubiquinone
- Plastoquinone
What is vitamin E?
- Tocopherol
- Acts as an antioxidant and reduces oxidative stress by reacting with O2 radicals
What is vitamin K?
- Tocopherol
- Blood-clotting cofactor to prothrombin (phylloquinone)
What is Warfarin?
- Tocopherol
- Synthetic compound that inhibits prothrombin
What is ubiquinone?
- Tocopherol
- Mitochondrial electron carrier (coenzyme Q)
- Acts as a coenzyme in the ETC for ATP sythesis
What is plastoquinone?
- Tocopherol
- Chloroplast electron carrier
