Struct. of Lipids Flashcards
Describe different kind of lipid structures
- hydrocarbon chain+ carboxyl group (COOH)
- Cholesterol:
- > polar head group (OH)
- > Steroid nucleus
- > Alkyl side chain
- triglyceride:
- has a glycerol backbone
- head-group substituent
What is the difference between saturated and unsaturated fatty acids?
- saturated fatty acids (s.a. palmitic acid) do not have a double bond
- unsaturated fatty acids (s.a. linoleum acid) do have at least one double bond
In what way are lipids storage of energy?
- Storage of energy:
- Reduced compounds: lots of available energy
- Hydrophobic nature: good packing
In what way do lipids help with the insulation from environment?
- Low thermal conductivity
- High heat capacity (can “absorb” heat)
- Mechanical protection (can absorb shocks)
In what way are lipids water repellant?
- Hydrophobic nature: keeps surface of the organism dry
- Prevents excessive wetting (birds)
- Prevents loss of water via evaporation (Verdunstung)
In what way do lipids help with Buoyancy control and acoustics in marine mammals?
- Increased density while diving deep helps sinking (just a hypothesis)
- Spermaceti organ may focus sound energy: sound stun gun?
What are some other functions of lipids? (Membrane structure, Cofactors for enzymes, Signaling molecules, Pigments, Antioxidants)
-Membrane structure
- Main structure of cell membranes
• Cofactors for enzymes
– Vitamin K: blood clot formation
– Coenzyme Q: ATP synthesis in mitochondria
• Signaling molecules
– Paracrine hormones (act locally)
– Steroid hormones (act body-wide)
– Growth factors
– Vitamins A and D (hormone precursors)
• Pigments
– Color of tomatoes, carrots, pumpkins, some birds
• Antioxidants
– Vitamin E
What are antioxidants?
-eine chemische Verbindung, die eine Oxidation anderer Substanzen verlangsamt oder gänzlich verhindert
What are canthaxanthin and zeaxanthin?
-are color
-> canthaxanthin: bright red
C40H52O2 (O bei stelle 3L und 0R ring)
-zeaxanthin: bright yellow
C40H56O2 (OH bei stelle 4L und 1R ring)
Which classification groups exist in lipids?
- lipids contain fatty acids/ do not contain fatty acids (cholesterol, terpenes)
- lipids contain fatty acids:
1. storage lipids
2. membrane lipids (1. Phospholipids, 2. Glycolipids, 3. Archaebacterial ether lipids)
How many carbons fo carboxylic acids with hydrocarbon chains contain?
- 4 to 36
(+ almost all natural fatty acids have an even number (grade Zahl of carbons)
->most natural fatty acids are unbranched
Give definition for monounsaturated and polyunsaturated
-Monounsaturated: one double bond between carbons in the
alkyl chain
• Polyunsaturated: more than one double bond in the alkyl chain
Give the nomenclature of greek alphabet
- Α α, alpha, 1
- Β, β, beta, 2
- Γ, γ, gamma, 3
- Δ, δ, delta, 4
- Ε, ε, epsilon, 5
- Ζ, ζ, zeta, 6
- Η, η, eta, 7
- Θ, θ, theta, 8
- Ι, ι, iota, 9
- Κ, κ, kappa, 10
Which role do Omega-3 fatty acids take in human’s life? Which are included?
-are essential nutrients
-Humans need them but cannot synthesize them
-Including ALA, DHA, and EPA
• Although DHA and EPA can be synthesized from ALA
->Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), Alpha-linolenic acid (ALA)
What can you say about the solubility and melting point of fatty acids?
- Solubility:
- decreases as the chain length increases
- Melting Point:
- decreases as the chain length decreases
- decreases as the number of double bonds increases
Conformation (räumliche Anordnung) of fatty acids (incl. saturated, unsaturated chain)
-The saturated chain tends to adopt extended conformations
- The double bonds in natural unsaturated fatty acids are
commonly in cis configuration, which kinks the chain
Why do unsaturated cis fatty acids have a lower melting point?
-It takes less thermal energy to disrupt disordered packing of unsaturated fatty acids ->disordered: due to the kink – less-extensive favorable interactions
Are the saturated fatty acids ordered or less ordered?
-Saturated fatty acids pack in a fairly orderly way
–> extensive favorable interactions
What determines the membrane fluidity?
-mainly by the fatty
acid composition
->More fluid membranes require shorter and more
unsaturated fatty acids:
-At higher temperatures cells need more saturated fatty
acids
– To maintain integrity
• At lower temperatures cells need more unsaturated
fatty acids
– To maintain fluidity
How is a trans fatty acid formed? What does it increase?
-by partial dehydrogenation of
unsaturated fatty acids
-Done to increase shelf life (Haltbarkeit) or stability at high temperature of oils used in cooking (especially deep frying (frittieren) )
->Trans fatty acids can pack more regularly and show
higher melting points than cis forms
What does a trans double bond allow a given fatty acid?
-to adopt an extended conformation
What are Triacylglycerols? How are solids/ liquids called? Solubility in comparison of fatty acids ; density in comparison of water
-Nonpolar
–The primary storage form of lipids (body fat)
-Majority of fatty acids in biological systems are found
in the form of triacylglycerols
-Solid ones are called fats
-Liquid ones are called oils
-Less soluble in water than fatty acids due to the lack
of charged carboxylate group
-Less dense than water: fats and oils float
What are the advantages of fats over polysaccharide?
-Fatty acids carry more energy per carbon because
they are more reduced
-Fatty acids carry less water per gram because they
are nonpolar
-Glucose and glycogen are for short-term energy needs,
quick delivery
-Fats are for long-term (months) energy needs, good
storage, slow delivery
What are waxes?
-Waxes are esters of long-chain saturated and unsaturated fatty acids with long-chain alcohols
What are waxes properties?
-Insoluble and have high melting points
Name variety of functions for waxes
- Storage of metabolic fuel in plankton
- Protection and pliability (Biegsamkeit) for hair and skin in vertebrates (Wirbeltiere)
- Waterproofing of feathers in birds
- Protection from evaporation (Verdunstung) in tropical plants and ivy (Efeu)
- Used by people in lotions, ointments, and polishes
Describe the structure of lipids in membranes
-are polar
-Contain polar head groups and nonpolar tails (usually
attached fatty acids)
Where can diversification in lipids in membranes come from?
- modifying a different backbone
- changing the fatty acids
- modifying the head groups
What does determine the surface properties of membranes?
-the properties of head groups
->Different organisms have different membrane lipid
head group compositions
->Different tissues have different membrane lipid
head group compositions
What is glycerophospholipids? How is it constructed?
-Primary constituents of cell membranes
-Two fatty acids form ester linkages with the first and second
hydroxyl groups of L-glycerol-3-phosphate
-Unsaturated fatty acids are commonly found connected to C2
-Head group is charged at physiological pH
(The highly polar phosphate group may be further esterified by an
alcohol; such substituent groups are called the head groups)
Name some examples of glycerophospohlipids
-Phosphoatidic acid : x= -H charge at ph7 (-2)
-Phosphatidylethanolamine: ethanolamine x= -NH3 charge at ph7 (0)
-Phosphatidylcholine choline : x= -NH3
charge at ph7 (0)
-phosphatidylserine serine
charge at ph7 (-1)
-phosphatidylglycerol
charge at ph7 (-1)
What is Phosphatidylcholine?
-the major component of most eukaryotic cell membranes
-Many prokaryotes, including E. coli, cannot synthesize this
lipid; their membranes do not contain phosphatidylcholine
What is Plasmalogen? Where is it common? What are the functions?
-Vinyl ether analog of phosphatidylethanolamine
-Common in vertebrate heart tissue
• Also found in some protozoa and anaerobic bacteria
• Function is not well understood
– Resistant to cleavage (Spaltung) by common lipases (feat spaltendes enzyme) but cleaved by few specific lipases
– Increase membrane rigidity (Steifigkeit) ?
– Sources of signaling lipids?
– May be antioxidants?
What is sphingolipids backbone?
-backbone is not glycerol it is a long-chain amino alcohol sphingosine
How is fatty acid joined to sphingosine? How is a polar head group connected to sphingosine?
- via an amide linkage (rather than en ester linkage (as usually seen in lipids))
- A polar head group is connected to sphingosine by a glycosidic or phosphodiester linkage
Where are the sugar- containing glycosphingolipids found?
-largely in the outer face of plasma membranes
How is a sphingomyelins constructed?
-Ceramide (sphingosine + amide-linked fatty acid) +
phosphocholine attached to the alcohol
Where is sphyingomyeling abundant?
-myelin sheath that
surrounds some nerve cells in animals
How are blood groups determine in parts?
- by the type of sugars located on the head groups in glycosphingolipids
How are the structure of sugar determined?
-by an expression of
specific glycosyltransferases
Which individual have the 0 antigen? Which have blood group A? Which have a blood group B?
-Individuals with no active glycosyltransferase will have the O antigen
– Individuals with a glycosyltransferase that transfers an N-
acetylgalactosamine group have A blood group
– Individuals with a glycosyltransferase that transfers a galactose
group have B blood group
What is the tay-sachs disease?
-(also known as GM2 gangliosidosis or hexosaminidase A deficiency ) is a rare autosomal recessivegenetic disorder (needed for GalNAc)
-In its most common variant (known as infantile Tay–Sachs disease), it causes a
progressive deterioration (Verschlechterung) of nerve cells and of mental and physical abilities that begins around 7 months of age
and usually results in death by the age of four
What is Gaucher’s disease?
-Gaucher's disease or Gaucher disease (GD) is a genetic disorder in which glucocerebroside (a sphingolipid, also known as glucosylceramide (Glc)) accumulates (anhäufen) in cells and certain organs -The disorder is characterized by bruising (blutergüsse), fatigue,anemia, low blood platelet count and enlargement of the liver and spleen (Milz)
What is the Sandhoff disease?
-also known as Sandhoff-Jatzkewitz disease, variant 0 of GM2- Gangliosidosis or Hexosaminidase A and B deficiency, is a lysosomal genetic, lipid storage disorder caused by
the inherited deficiency to create functional beta-hexosaminidases A and B -Accumulation of these metabolites leads to a progressive destruction of the central nervous system and eventually to death
What is the Fabry disease?
- also known as Fabry’s disease, Anderson-Fabry disease, angiokeratoma corporis diffusum, and alpha-galactosidase A deficiency
- is a rare genetic lysosomal storage disease, inherited in an X- linked manner
- Fabry disease can cause a wide range of systemic symptoms
What is the Niemann–Pick disease?
-is a group of inherited, severe metabolic disorders in which sphingomyelin accumulates in lysosomes in cells
-Accumulation of sphingomyelin in the central nervous
system (including the cerebellum) results in unsteady gait (ataxia) (Gangart), slurring of speech (dysarthria) (Sprachverwirrung), and difficulty in swallowing (dysphagia)
What do dysfunctions in Basal ganglia cause?
-causes abnormal posturing of the limbs, trunk, and face
dystonia
What do upper brainstem disease cause?
-disease results in impaired voluntary rapid eye movements (supranuclear gaze palsy)
What do more widespread disease involving the cerebral cortex and subcortical structures cause?
-causes gradual loss of
intellectual abilities, causing dementia and seizures (Anfall)
How is sterol constructed?
- Steroid nucleus: four fused rings
- Hydroxyl group (polar head) in the A-ring
- Various nonpolar side chains
- The steroid nucleus is almost planar
- ->many hormones are derivatives of sterols
Where are cholesterol and related sterols present? +functions
-Cholesterol and related sterols are present in the
membranes of most eukaryotic cells
From where do mammals obtain cholesterol?
-from food or synthesize it de novo in the liver
How is cholesterol transported and where?
-Cholesterol, bound to proteins, is transported to
tissues via blood vessels
-Cholesterol in low-density lipoproteins tends to deposit (abzuschneiden) and clog arteries
What do sterols and hopanols increase?
-membrane rigidity (steifigkeit) and permeability (Durchlässigkeit)
Cell membranes of which type contain sterols/ hopanols?
Cell membranes of many eukaryotes contain sterols – Cholesterol in animals – Phytosterols in plants – Ergosterol in fungi -Cell membranes of aerobic prokaryotes contain hopanols
What are steroid hormones? How are they carried in the body?
-Steroids are oxidized derivatives of sterols
-They are carried through the body in the
bloodstream, usually attached to carrier proteins
• Many of the steroid hormones are male and female sex hormones
How do steroid hormones differ form cholesterol?
–Steroids have the sterol nucleus, but lack the alkyl
chain found in cholesterol
-More polar than cholesterol
Name the types of steroid hormones
-testosterone, cortisol, prednisone, b-estradiol, aldosterone, prednisolone, brassinolide (a brassionsteroid)
What is created if arachidonic acid is metabolized? What does arachidonic acid yield if it is enzymatic oxidized?
- signaling lipids
- Prostaglandins (inflammation (entzündung) and fever)
- Thromboxanes (formation of blood clots)
- Leukotrienes (smooth muscle contraction in lungs)
What does PGH2 have twice?
-isoforms
-COX-1 catalyzes synthesis of prostaglandins that regulate gastric mucin secretion (Magenschleimsektion)
• COX-2 catalyzes synthesis of prostaglandins that mediate pain, inflammation, and fever
–> NSAIDs (Aspirin, Ibuprofen, Acetaminophen)
inhibit COX-2
What can block the formation of prostaglandins and thromboxanes
from arachidonate?
-Nonsteroidal antiinflammatory drugs (NSAIDs) such as aspirin and ibuprofen can block by inhibiting the enzyme cyclooxygenase (prostaglandin H2 synthase).
How does the blocking of the formation of prostaglandins and thromboxanes
from arachidonate exactly work?
-Aspirin (Acetylsalicylate) is an irreversible inhibitor -Acetylates a Ser in active site -Blocks active site in both COX isozymes •Ibuprofen and naproxen are competitive inhibitors -Resemble substrate, also block active site in both isozymes
Name a Few NSAIDs that Inhibit PGH2
-aspirin, salicylate, ibuprofen, naproxen
Tell a little bit about the story of COX-2 specific inhibitors history
-Developed to inhibit prostaglandin formation
without harming stomach
• Includes Vioxx, Bextra, and Celebrex
• Vioxx and Bextra removed from market due to
increased rates of stroke and heart attack
– May disrupt balance between blood-thinning
prostacyclin and blood-clotting thromboxanes
The importance of biologically active lipids
-Are present in much smaller amounts than storage or structural lipids
-Play vital roles as signaling molecules between nearby
cells
• Lipid soluble vitamins (A, D, E, and K)
What does Vitamin D regulate?
-the calcium uptake (Calciumaufnahme)
Vitamin A is involved in?
- Vitamin A (Retinol) is Involved in visual pigment
- Precursor for other hormones involved in signaling
What are Vitamin E,K and other lipid quinones (Lipidchione)?
- antioxidants
- Vitamin E an antioxidant
- vitamin K a blood clotting cofactor (phylloquinone)
- warfarin a blood anticoagulant
- ubiquinone a mitochondrial electron carrier N= 4 to 8
