Lecture 6 - Lipids Part 1 Flashcards
Are lipids hydrophobic?
yes, hydrophobic/nonpolar parts
don’t usually mix with water
What are the functions of lipids?
energy sources and energy storage
membrane components (cell structure)
hydrophobic anchors for proteins in membranes
signaling molecules (intra and extracellular signaling)
regulators
light absorbing pigments (retinal)
electron carriers
enzyme cofactors (vitamin K)
waterproofing/lubricating compounds (waxes/oil)
insulation/protection
cushioning
What 2 functional groups are in fatty acids?
saturated and unsaturated
What is an aliphatic hydrocarbon tail?
open chain structure (not aromatic ring)
What has unsaturated fatty acids?
plant products (vegetable oil)
cannot pack together closely –> liquid at room temp
What is causing the kink in fatty acids?
1 or more double bonds
What are essential fatty acids and what is an example?
fatty acids that are required for biological processes but not made by human body
ex) omega 3 fatty acids, omega 6 fatty acids
What isomer form is the most natural form of fatty acids?
cis form - H on same side as DB
What are eicosanoids?
signaling molecules
made up of 20-carbon polyunsaturated fatty acids (PUFAs)
What are the 3 major eicosanoids and what processes do they regulate?
- prostaglandins (PG) lipid signaling molecule that regulates synthesis of cAMP
- thromboxane (TX) lipid signaling molecule that forms blood clots and reduces blood flow to clot site
- leukotriens (LT) mediates acute and chronic inflammation –> leads to asthma
How do eicosanoids influence cells? What are the 3 types of signaling (effector cells)?
autocrine signaling - self
paracrine signaling - to cell neighbors
endocrine - distant cells
What drugs affect the formation of PGs and TX by blocking which enzyme?
NSAIDs (aspirin, ibuprofen) inhibit COX enzyme - block formation of TX and PG
What do glycerides consist of?
esters formed from glycerol and fatty acids
What is glycerol?
carbohydrate alcohol with 3 -OH groups
What are triglycerols/triglyceride? What are they made of?
glycerol + 3 fatty acids
type of fat found in blood
body converted unused calories into triglycerides to store for later
What are simple and mixed triglycerides?
simple = 3 fatty acids are identical (stearing and pallmitin)
mixed = 3 fatty acids are different
What are phosphoglycerides made of and what are the features of these molecules?
have phosphoric acid and 2 fatty acid tails
phosphoric acid = hydrophilic
2 FA tails = hydrophobic
**amphiphilic
What major function do phospholipids have (where do we find them in a cell)?
key component of cell membranes
phospholipid bilayer
vesicles (exosomes)
What are 3 major phospholipid classes (determined by head group)?
- lecithin (head: choline)
- cephalin (head: ethanolamine, serine)
- insoitol phospholipids (head: inositol)
Phosphatidylcholine is found in what group of lipids?
lecithin
Which neurotransmitter is lecithin-based?
acetylcholine
Which retinal cells express acetylcholine?
amacrine cells in retina
What do sphingolipids consist of?
lipids with sphingoid base (aliphatic aka open chain amino alcohols with sphingosine - unsaturated hydrocarbon backbone)
Do sphingolipids contain glycerol?
no glycerol
How are the 2 major classes of sphingolipids (SLs) different?
- phosphosphingolipids (PSLs) = sphingomyelin + phosphate
- glycosphingolipids (GSLs) = glycolipid + sphingoid base (sugar component)
SLs are found predominantly in what part of the cell, and in which special structure?
found in cell membrane forming lipid rafts
What is a ceramide?
sphingosine + fatty acid
backbone of PSLL and GSL
What role do GSLs play in the blood?
specify cell identity
determinants of blood groups (A/B/O) - human blood groups determined by oligosaccharide head groups of GSLs
Phospholipids include which types (categories) of lipids?
phosphoglycerides and sphingomyelins
What are steroid lipids (sterol) made of??
4 fused rings
3rd C atom has -OH group
What is the steroid nucleus and what other names does this structure have?
4 ring core - 3 cycohexane rings, 1 cyclopentane ring
also called gonane structure
What are 2 major functions of steroid lipids?
important components of cell membranes that alter membrane fluidity
signaling molecules (steroid hormones)
Which molecule is the precursor of steroids in animals including us?
cholesterol is precursor of steroids
Are steroids amphipathic and if so, why or why not?
yes amphipathic/amphilic
nonpolar hydrocarbon body (nucleus and carbon side chain)
sterol = polar head (-OH group)
What function does cholesterol have in the membrane?
increases order of lipid packing –> lowers membrane permeability
regulator of membrane fluidity
In which membrane structures is cholesterol predominantly found?
cholesterol in plasma membrane
cholesterol + sphingomyelin = lipid raft formation
Which structures in nervous system are cholesterol-rich? To which cell types do these structures belong?
myelin sheaths cholesterol rich:
1. CNS oligodendrocytes (glial cells) make myelin for CNS axons
2. PNS Schwann cells (glial cells) make myelin for PNS axons
Cholesterol is turned into which vitamin when your skin is exposed to the sun?
UVB light converts cholesterol (precursor) to vitamin D
Which hormones derive from cholesterol (5)?
- progesterone
- aldosterone
- testosterone
- estrogen (estradiol)
- cortisol
What are corticosteroids, which are the 2 types called? Give an example.
corticosteroids - steroid hormones produced in adrenal cortex
glucocorticoids: cortisol
mineralocorticoids: aldosterone
Which side effects can glucocorticoids have on the eye?
long term use of glucocorticoids = cataracts and glaucoma
Which hormone (belonging to which class of steroid hormones) regulates ion transport in glands?
mineralocorticoids (aldosterone) regulate salt and water balance in glands
Which hormone is the stress hormone?
glucocorticoids (cortisol) stress hormone that increases sugar in bloodstream in response to danger
Isoprenoids (terpenoids) are building block of which 3 major compounds?
- sex hormones
- vitamins
- pigments
Which vitamin is essential for vision and why?
vitamin A (retinol) and its derivatives important for vision b/c chromophore 11-cis-retinal combines w/ opsin to make rhodopsin (light absorbing molecule)
What is the name of the chromophore found in photoreceptor cells? where is it found?
chromophore 11-cis-retinal found in rhodopsin in outer segment of discs of rod cells
Which 2 important pigments are found in the macula and what is their function?
lutein and zeaxanthin = antioxidants found in macula of retina - protective function against UV radiation and against AMD and cataracts
Lipid metabolism includes which processes (4)?
- hydrolysis of lipids by digestive enzyme
- absorption of fatty acids by intestinal epithelium and packaged into chylomicrons (amphipathic structures to transport digested lipids through blood to enter adipose and other cells)
- transoprtation: transported lipoproteins have varying densities
- storage: lipids stored in white adipose tissues as triglycerides (glycerol + 2 FAs)
Lipids are degraded during which reaction and catalyzed by which enzyme?
lipids degraded by hydrolysis with lipases
The primary 2 lipid types that are digested in our body are?
triglycerides and cholesterol broken down into individual FAs and glycerol
In which structures are triglycerides and cholesterol transported through the blood from the gut?
triglycerides and cholesterol transported in amphipathic chylomicrons from gut through blood
Which kinds of lipoproteins exist that transport digested fats (5)? Which one is the dangerous one and why?
- VLDL: very low density
- IDL: intermediate density
- LDL: low density **BAD b/c stores cholesterol in bloodstream = clogged pores
- HDL: high density
- chylomicrons (ULDL: ultra low density)
