Lec 4: Lipids Flashcards
are lipids…
polymers?
non-polar/polar?
soluble/insoluble?
lipids are not polymers
they are non-polar
they are largely insoluble in water (but soluble in non-polar solvents)
what interactions cause lipids to group together in water?
hydrophobic
*NOTE*: Examples of lipids (5)
Fats
Oils
Waxes
Phospholipids
Steroids
what does a triglyceride contain?
3x fatty acids chains and 1x glycerol
what bonds link the fatty acid chains to the glycerol back bone ?
ester bond
in what process are triglycerides formed?
dehydration synthesis
in what reactions are triglycerides broken down?
what enzyme does this require?
hydrolysis
requires the enzyme: triglyceride lipase and H2O
where is triglyceride lipase found? what does it do?
found in the intestine
breaks down triglycerides
what is the difference between a saturated and unsaturated fatty acid?
give examples
Saturated = contain single [C-C] bonds e.g palmitate
Unsaturated = contain 1 or more double [C=C] bond e.g Oleate
*a diagram of a saturated fatty acid looks
what are FFAs?
free fatty acids that are not part of a triglyceride
how do you name Omega FFAs?
go from the location of the first double bond, cound from the methyl end
what FFAS are essential (=cannot be synthesised in the body)
Omega-3 (ω-3) fatty acids (e.g. α-linolenic acid)
Omega-6 (ω-6) fatty acids (e.g linoleic acid)
what do saturated and unsaturated fatty acids form?
SFAs form compact, closely packed triglycerides that are solid at toom temp e.g Palmitic acid (16 C) present in plant and animal fats
UFAs form loosely packed triglycerides due to cis double bonds, liquid at room temp e.g Olive oil (80% oleic acid (18 C)
what is the basic structure of steroids?
four fused carbon rings with various side groups attached
what is lanosterol and how is it formed?
lanosterol is the building block for all steroids
it is formed by the cyclization of sqaulene
give examples of steroids
- cholesterol
- sex hormones: Oestrogen, Progesterone, Testosterone
- Corticosteroids: Aldosterone (mineralocorticoid), Cortisol (glucocorticoid)
- Vitamin D (cholecalciferol) = a secosteroid
what is the name of this steroid? what type type of steroid does it fall under?
oestrogen *oest to the OHgen*
a sex hormone
what is the name of this steroid? what type of steroid does it fall under?
aldosterone *a lot of =O*
corticosteroids
what is the name of this steroid? what type of steroid does it fall under?
Vitamin D
a secosteroid
what are phospholipids?
Lipids with a phosphate group (PO42-) covalently bonded to the glycerol backbone instead of a fatty acid
which groups on a lipid molecule are polar and non polar
Phosphate group:
Polar Soluble in water (hydrophilic)
Head
Fatty acid groups:
Non-polar Insoluble
in water (hydrophobic) Tail
what are some examples of phospholipids
H (phosphatidic acid)
Ethanolamine (phosphatidylethanolamine)
Serine (phosphatidylserine)
Choline (phosphatidylcholine)
Inositol (phosphatidylinositol)
what is micelle?
a spherical arrangement of lipid molecules
what is bilayer?
composed of two layers of lipids organised as a sheet
what is a glycolipid?
a lipid covently attached to an oligosaccharide
It forms part of the cell membrane and glycocalyx
It determines ABO blood group
what are lipoproteins?
Soluble complexes that transport lipids and synthesized in the liver
they are
what is the glycocalyx
The glycocalyx, also known as the pericellular matrix, is a glycoprotein and glycolipid covering that surrounds the cell membranes of some bacteria, epithelia and other cells.
what is the central hydrophobic core of lipoprotein made up of?
Triglycerides
Esterified cholesterol (cholesteryl ester)
Small amounts of other lipids and fat soluble vitamins
what is the external hydrophllic layer of a lipoprotein?
- Phospholipids
- Cholesterol (OH functional group outermost)
- Apoproteins - stabilise structure and regulate enzymatic activity at the lipoprotein interface
Order the following lipoprotein in terms of size and density;
chylomicron, VLDL (Very Low Density Lipoprotein), IDL (Intermediate Density Lipoprotein), LDL (Low Density Lipoprotein), HDL (High density lipoprotein)
Increasing in size order:
HDL, LDL, IDL, VLDL, chylomicron
density:
Chylomicron, VLDL, IDL, LDL, HDL
what does chylomicrons do? what apoprotein does it contain?
Chylomicrons carry dietary fat from small intestine to the liver
contains the app: B-48
what does a VLDL do? what apoprotein does it contain?
Produced in liver from synthesised triglycerides and chloestrol esters and carry fat to target tissues
appo E
what is a IDL and LDL? which apoproteins do they contain?
they are VLDLs which have had their triglycerides removed
so they then become LDLs then IDLs
LDL apo: Apo E
IDL apo: Apo B-100
what does a HDL do? which apoprotein does it contain?
HDL carries cholesterol to the liver (“good cholesterol” reducing atherosclerosis)
apo A-1
what do apoproteins do?
- stabilise structure and regulate enzymatic activity at the lipoprotein interface
what is the name given to a condition where the arteries become clogged with fatty material forming sites of fatty deposition called plaque? what can this condition trigger?
atherosclerosis
heart attack/stroke
how is atherosclerosis caused?
- Development of atheroma (sits of plaque in your arteries)
- deposition where hard scar forms ontop of the plaque
- this narrows the vessel in which blood flows
- this increases shear stress (friction from blood flow)
- so if the plaque ruptures, it triggers thrombosis
- closing of the vessel
Could result in ishemic heart attack/ischemic stroke
where are triglycerides stored and what are they stored as?
TGs stored as lipid droplets
in the cytoplasm of adipocyte cells
in adipose tissue
what is white adipose tissue and what is it’s function?
- made up of white fat cells which have a lipid droplet in the cytoplasm
- cushions internal organs like a shock absorber
- gives insulation, protecting internal organs from temperature changes and reducing skin heat loss
what is brown adpisose tissue and what is it’s function?
brown adipose tissue is made up of brown fat cells
which arise because off the mitochondria that generate heat and the numerous fat vacuoles
-therefore they are useful for warmth
where are the white adipose tissue locatated?
where is the brown adipose tissue located?
*Image shows Brown adipose depots in patients identified by deoxy-2-[18F]fluoro-Dglucose ([18F]FDG)-positron emission tomography (PET)
what diseases are excess adipose tissue involved in?
atherosclerosis-narrowing of blood vessel
thrombosis- clotting of circulating blood
stenosis- abnormal narrowing of blood vessel
aneurysms - blood filled bulge in a blood vessel wall
excess adipose tissue is now considered to be a major endrocine organ. What does this mean?
produces pro-inflammatory hormones such as leptin (affects appetite) and the cytokine TNFa (affects tissue)
what part of a nerve cell does a phospolipid form? how does this cell affect the function of the cell?
-phospholipids form the myelin insulation around nerve fibres
myelin increases the speed of nervous impulses
what cells produce myelin and how do they produce it?
Schwann cells produce myelin peripherally (nerves and ganglia outside cns)
Oligodendrocytes produce myelin centrally (brain/spinal cord)
what do vitamin A,D,E and K have in common?
they are all fat soluble
what are examples of Vitamin A and how does it benefit the body?
retinol/retinoic acid/carotenoids
gives you healthy teeth, skin, sight
what are examples of vitamin D and how does it benefit the body?
cholecalciferol and derivatives
Helps body absorb Ca2+ for healthy bones
what is vitamin E and how does it benefit the body?
a tocopherol (antioxidant) found in oils Anti-oxidant,
protects cells from damage
what are examples of vitamin K? how does it benefit the body?
phylloquinone and menaquinone Important for coagulation of blood
what are eicosanoids?
they are 20 carbon fatty acids
dervied from omega-3 and omega-6 fatty acids
what are the three types of eicosanoid hormones?
Prostaglandins (inflammation, vascular tone)
Leukotrienes (asthma and allergy)
Thromboxanes (vascular tone, platelet aggregation)
how do lipids prevent moisture loss?
- skin moisture loss is prevented by lipid layers
- comeocytes (skin cells) are held together by lipid rich matrix (like a glue) that holds the skin together
how do lipids reduce moisture loss from the cornea?
- the eye has several different layers
- the lipid (oil) layer is hyrdophobic which lubricates and prevents evaporation from the eye
- then you have the meibormian gland which create a lipid tear film
what benefits do lipids have?
phospholipid bilayer- provides protection from surrounding environment and anchoring to extracellular structures and other cells required for tissue formation
TGs and FFAs- energy rich C-H bonds available for chemical reactions
WAT- insulators and protection from temperature changes
BAT- generating body heat
phospolipid- form myelin which increase speed of nerve impulses
lipids- reduce skin moisture
