Lipids Flashcards
Define hormone
Hormone is any chemical that can elicit a cellular response
Define paracrine
Hormones that act on tissues that are nearby
Define autocrine
Chemical that act on the tissue that has produced the chemical itself
Define juxtacrine
Chemical and it’s receptor are cell membrane molecules. Ligands is expressed by one cell, the receptor is expressed by another cell. When the two interact, we call it Juxtacrine signaling
Define pheromone
Volatile substance that is made by one individual and act on another individual
Name biologically active lipids
Glycerophospholipids
Sphingolipids
Sterol lipids
Prenol lipids
What are biologically active lipids
Lipids, that are involved in bio signaling
What is the other name for membrane lipids
Structural lipids
What are precursors of inositol-phosphates
Glycerophospholipids
What type of lipid is PIP2?
Glycerophospholipid
How is PIP2 turned into inositol-phosphates
Phosphotylinositol 4,5-bisphosphate –Hydrolysis by Phospholypase C–> IP3 + DAG
Phosphotylinositol 4,5-bisphosphate –phosphorylation by PI3Kinase–> PIP3
IP3 and DAG which one stays in the membrane, which one enters the cytosol
IP3 enters the cytosol
DAG stays in the membrane
What does IP3 do?
Stimulates glycogen breakdown
How does IP3 stimulate glycogen breakdown?
- GPCR interacts with a ligand-> goes to activate its target
- Its target is PLC which cleaves PIP2 into IP3 and DAG
- IP3 cuases a release of Ca2+. Ca2+ activate calmodulin
- Calmodulin is an effector which leads to a signaling cascade that activates an enzyme phosphorylase kinase
- Phosphorylase kinase activates glycogen phosphorylase
- Glycogen phosphorylase cleaves off glucose molecules from glycogen polymers.
– is the simplest form of sphingolipids
Ceramide is the simplest form of sphingolipids
Can sphingolipids be involved in signaling?
Sphingolipids are mainly structural lipids
Assists in signaling process, but not a signaling molecule itself
How do sphingolipids assist in signaling?
- Ceramide holds lipid rafts together
These rafts are fully mobile. As they move in the plasma membrane, they carry with them any receptors or signaling molecules within that region
That is how signal can be localized - Sphingomyelin insulate nerve axons
Important for action potential propagation
What are glycosphingolipids?
Sphingolipids with sugars
Describe how genetics determine the blood groups
Blood group depends on the additional sugars added to a oligosaccharide head groups (H-antigen_ of glycosphingolipids
These sugars are added by specific glycosyltransferases
Depending on a gene for a specific glycosyltransferases oyu can either have:
O antigen: H antigen only
A- antigen: H antigen+ N-acetylgalactosamine
B antigen: H antigen + N-acetylglucosamine
What are eicosanoids?
Lipids with 2o carbons
What is the most basic eicosanoid?
Arachidonic acid
How is Arachidonic acid produced
It is released from glycerophospholipids by enzyme Phospholipase A2
What are the functions of prostaglandins?
Function in paracrine signals, smooth muscle contractions/ Also regulate reproductive cycles. Uterine contractions. Sometimes used in labors to induce uterine contractions
What are the functions of thromboxanes? Where are they released from?
Form blood clots and reduce blood flow. Released from platelets - thrombocytes, hence the name
What are NSAIDs?
Nonsteroidal anti-inflammatory drugs
Inhibit cyclooxygenase enzymes (COX1 and 2) that are involved in production of prostaglandins and thromboxanes from arachidonate
These drugs reduce inflammation as prostaglandins are pro-inhibitory lipids
What are leukotrienes?
Cause airway smooth muscle contractions
They are produced by leukocytes- white blood cells.. In asthma and anaphylactic shock
What can inhibit leukotrienes? Uses of it
Prednisone
Used to treat asthma
Name eicosanoids (5)
Arachidonate Prostaglandins Thromboxanes Leukotrienes Lipoxin A
Leukotrienes and lipoxins are called ___ eicosanoids- no ____
Leukotrienes and lipoxins are called linear eicosanoids- no ring structure
Which enzyme should be targeted to inhibit production of all prostaglandins from arachidonate
Phospholipase A2
Which type of receptors is used by eicosanoids?
All of their receptors are GPCRs
Name the receptor of testosterone
Androgen receptor
Name the receptor of estradiol
Estrogen receptor
Name the receptor of cortisol
Glucocorticoidreceptor
Name the receptor of aldosterone
Mineralocorticoid receptor
Steroids- derived from __; carried in blood by ___
Steroids- derived from cholesterol; carried in blood by carrier protein
What is the structure of steroids
three 6 carbon rings, one 5 carbon ring
What do steroids mainly affect? How?
They mainly affect cellular transcription through their receptors- nuclear receptors
Vit D is both a ___ and __
Vit D is both a hormone and vitamin
What are the two form of Vit D3?
- Cholecalciferol - inactive
- 1,25-Dihydroxycholecalciferol (Calcitriol)- active
What does Calcitriol do?
- Plays a major role in calcium metabolism- Ca absorption (intestine) and excretion (kidney)
- Ca storage (bone)
How does Vit D signal?
Signals through Vit D receptor (VDR), which is a nuclear receptor
What are the consequences of Vit A deficiency?
Vit A deficiency leads to
growth retardation, night
blindness, etc
Describe how does beta-carotene acts as a precursor
It’s a precursor for Vit A
b-carotene can be cleaved into all-tans-retinal which can either be converted to all trans-retinoic acid or all-trans-retinol (Vit A)
What can be formed from all-trans-retinol (Vit A)? It importance?
Visual pigment rhodopsin which is converted to all-trans-retinal
This is the process by which our eyes sense light
What are the receptors associated with carotenoids?
Nuclear receptors: Retinoic acid receptor (RAR) for hormone signaling (change in gene expression) and Retinoid X receptor (RXR) for neuronal signaling (vision)
Name tocopherols and their general function
Tocopherols act as cofactors
- Vitamin E
- Vitamin K
- Warfarin
Function of ubiquinone
Mitochondrial electron carrier
Function of warfarin
Blood anticoagulant- a synthetic compound- inhibits prothrombin
Eicosanoids are __ hormones and ___ factors
Eicosanoids are paracrine hormones and paracrine factors
What produces thromboxanes
They are produced by platelets
Steps of Vit D3 formation
Active form is formed from 7-dehydrocholesterol to cholecalciferol (inactive D3)by UV light in skin. It is then converted in liver and kidney to 1α,25-dihydroxyvitamin D3
(calcitriol)
Through which receptor does Vit A act?
Retinoid acid receptor (RAR), Retinoid X receptor (RXR)
Name vitamins that are steroid hormones? Through which receptor do they act?
Vit A, D, K and E
Act through nuclear receptors
What are tocopherols?
Vitamin E is the collective name for a group of closely related lipids called tocopherols
What are the benefitial functions of Vit E, Vit K and Warfarin?
Vit E reacts with O2 radicals- antioxidant
Vit K is a co-factor for prothrombin- helps in blood clotting
Warfarin- Blood anticoagulant- a synthetic compound- inhibits prothrombin