lipids (b2- CVS)

Question 1

Define lipids LO

Answer 1

organic substances that are fatty acids or their derivatives and are insoluble in water but soluble in organic non-polar solvents

Question 2

Enlist biochemical functions of lipids LO

Answer 2

1. storage form of energy (triglycerides)
2. structural components of bio membranes
3. metabolic regulators (steroid hormones, prostaglandins, leukotrienes)
4. act as surfactants, detergents, & emulsifying agents (amphipathic lipids)
5. provide insulation against changes in external temp (subcutaneous fat)
6. protect internal organs (pads of fat)
7. help in absorption of fat-soluble vitamins (A, D, E, K)
8. give shape & contour to our body

Question 3

physical properties of lipids

asked in MCQs

Answer 3

• pure lipids are colorless, odorless, & tasteless
  (appearance of color/taste/smell in fats/oils is due to presence of impurities dissolved in them)
• insoluble in polar solvents (water)
• soluble in non-polar solvents like ether, chloroform, benzene, acetone
• lower density than water/lighter than water
• leave greasy marks on paper
• may either be liquid (oil) or non-crystalline solids (ghee) at room temp

Question 4

6 chemical properties of SEQs

asked in MCQs

Answer 4

1. hydrolysis: can be hydrolyzed by heating in water at high temp & pressure
   - yield glycerol & fatty acids
2. saponification: process of soap making (by boiling lipids w/ alkaline like NaOH & KOH)
3. hydrogenation: hardening of oils by breaking double bonds, adding H to unsaturated double bonds - converts liquid fats to solid fats
4. halogenation: adding halogens (usually iodine) to unsaturated double bonds
   - used as an index of degree of unsaturated of an oil/fat/iodine number
5. oxidation: unsaturated FA’s can easily react w/ oxygen in the air
   - when this happens, form a chitinous outer layer (tough covering) which is called drying of oils
   - useful for paints and varnishes
6. rancidity: slow spoiling process that affects fats/oils
   - overtime develop a bad smell/taste due to contamination w/ lipases in the presence of moisture
   - more on another card

Question 5

what enzyme is responsible for the hydrolysis of dietary fats in the human body?

Answer 5

pancreatic lipases

Question 6

iodine number/value of fatty acids (extra info on slides but prob good to know)

Answer 6

tells how unsaturated a fat or oil is (measures how many double bonds are present)

done by process of halogenation

more unsaturated = more halogen the fat can absorb

Question 7

how does chemical property of rancidity work in fatty acids?

Answer 7

contamination of moisture and lipase enzyme (enzymes from bacteria/molds) breaks down the fats into short chain fatty acids & aldehydes

they both have strong, unpleasant odors so rancidity causes the fatty acids to develop an unpleasant odor/taste

rancidity can be prevented by adding antioxidants in fats/oils like Vitamin E

Question 8

what are the 4 classifications of lipids? (just list the names not all the details)

Answer 8

1. simple lipids: simplest types of lipids, made of fatty acids + alcohol
   - fats/oils (TAGs), waxes
   - ex. butter, olive oil, beeswax
2. compound/complex lipids: in addition to fatty acids and alcohol, also contain other components like phosphate, sugar, or nitrogen
   - phospholipids, glycolipids, lipoproteins
3. derived lipids: lipid-like substances formed when simple or compound lipids are broken down (hydrolyzed)
   - fatty acids, steroids, eicosanoids (prostaglandins, leukotriene, lipoxin), ketone bodies
4. miscellaneous lipids: aren’t really lipids but act like them (have characteristics of lipids)
   - squalene, carotenoids

Question 9

subtypes of 1. simple lipids

Answer 9

triglyceride (TAGs): 3 fatty acid chains + glycerol
- the fat we mostly eat is TAG
- in liquid state is called oil

waxes: fatty acids + a long chain alcohol
- no nutritional value so mostly used in pharmaceuticals & cosmetics (lipstick, candles, etc.)

Question 10

subtypes of 2. compounds lipids

Answer 10

1. phospholipids: FA + Alcohol + Phosphoric acid + nitrogenous base
   - further divided into based on type of alcohol thats in them:
   a. glycerophospholipid: lechitin, cephalin, cardiolipin, phosphatidylserine, phosphatidylinositol
   b. sphingophospholipid: sphingomyelin
2. glycolipids: FA + sphingosine + carb
   - ex. cerebrosides, gangliosides
3. lipoproteins: lipid + protein
   - chylomicrons, VLDL, LDL, HDL

need to know all these subclassifications when asked for classification of lipids

Question 11

clinical correlates: diseases associated with abnormal lipid metabolism

Answer 11

1. atherosclerosis: fats, esp cholesterol builds up in the walls of arteries = arteries narrow & harden = can lead to heart attack, stroke, or high blood pressure
2. diabetes mellitus: body cant use glucose properly due to lack of insulin so body breaks down fats instead of sugars for energy = higher blood lipid levels
3. obesity: extra calories converted to triglycerides & stored in fat cells (increases risk for all these other issues)
4. fatty liver disease: fat accumulates in liver cells interfering w/ liver function
5. lipid storage disease (lysosomal storage diseases): lipids build up in cells b/c body can’t break them down properly
   - genetic causes

Question 12

Fatty acids belong to what classification of lipids?

Answer 12

Derived lipids

Question 13

define fatty acids LO

Answer 13

aliphatic mono-carboxylic acids that are mostly obtained from hydrolysis of natural fats & oils (derived lipids)

• most common component of lipids in the body
• mostly have straight chains (few exceptions have branched & heterocyclic chains)

Question 14

2 biochemical functions of fatty acids LO

Answer 14

1. building blocks of compound lipids (glycolipids, phospholipids, cell membrane)
2. major fuel for most cells (fatty acids taken to liver after being broken down in adipose & muscle tissues)

Question 15

essential fatty acids (diff from regular fatty acids)

Answer 15

fatty acids: general term for all types of long carbon chains with a carboxyl group

essential fatty acids: special fatty acids that your body needs but cannot make, so you must get them from your diet
- 2 main essential fatty acids: linoleic acid (omega-6) & α-linolenic acid (omega-3)

• from these, body can make other important fatty acids

Question 16

6 biochemical functions of essential fatty acids

Answer 16

1. synthesis of eicosanoids: these are signaling molecules made from essential fatty acids - helps regulate imp body processes
   - include: prostaglandins, prostacyclins, leukotrienes
2. synthesis of EPA & DHA (ω-3 PUFAs) from linolenic acid: linolenic acid (ALA) is essential omega-3 fatty acid that body converts into:
   - EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)
   - helps with proper development & functioning of the brain & nervous system)
3. maintenance of structural integrity: formation of healthy cell membranes
   - structural integrity of mitochondrial membrane
4. lipoproteins formation
5. prevent fatty liver (deposition of TAG in liver)
6. antiatherogenic effect (PUFA is cardioprotective)

essential fatty acids (arachidonic acid) increase esterification & excretion of cholesterol, thereby lowering serum cholestrol level

Question 17

4 classifications of fatty acids (imp!!!)

Answer 17

1. chain length: # of C atoms in the fatty acid chain
   - short (2-6)
   - medium (8-14)
   - long (14-24)
   - very long (24+)
2. total carbon atoms: total # of C atoms in the fatty acids, not just in the side chain
   - odd chain or even chain
3. nature of chain: type of bonds in the fatty acid chain
   - saturated, unsaturated (mono & poly), branched, hydroxy
4. synthesis in body: essential (not synthesized, need to get from diet) and non-essential

Question 18

examples of even & odd chain fatty acids

Answer 18

even chain saturated fatty acids:
- acetic acid (2 C - small chain) - vinegar
- myristic acid (14 C - medium chain) - coconut oil
- palmitic acid (16 C -long chain) - body (animal) fat

odd chain saturated fatty acid:
- propionic acid - metabolism