lipids Flashcards
Functions
-energy source
-energy storage
-insulation/protection
-cell membrane structure
-transport of fat-soluble vitamins
-hormones and signal molecules
-vitamin D, bile, sex, pros
-regulators of appetite and satiety
Triglycerides
95% of what we consume
-energy source and storage
(9cal/g and fuel source is secondary to glucose)
-fat as fuel is preferred by heart, liver, and resting muscle
-spares glucose for use by nervous and RBC
-stored in adipocytes
adipose tissue
subcutaneous= tissue for thermoregulation
visceral= surrounds and protects organs
Not enough fat
skin issues, depression, compromised immune, infections, slow wound, anemia, diarrhea
Fatty acids
long carbon chains with a carboxyl and a methyl group
-building bloxk of nutritional lipid
n= any even number from 2-24
FA vary by
-length of chain, degree of satuartion, shape
Length of chain
Acetic acid (C2:0)
Palmitic Acid (C14:0)
Stearic Acid (C18:0)
-short chain <8 C
Medium chain 8-14 C
Long 16 or more
very long >22C
Saturation
saturated=no double bonds
ex: stearic acid
unsaturated= one or more double bond
Ex: Monosaturated=oleic acid (c18:1)
-Polyunsaturated= Linoleic (C18:2) or Linolenic (C18:3)
Omegas
Omega number: position of the double bond closest to the methyl end
-MUFA: Omega-9=oleic acid
-PUFA(2): Omega-6= linoleic
-PUFA (3): Omega-3=Linolenic
Essential FA
Unsaturated, essential to human health and cannot be manufactured in the body
-linolenic omega 3
-linoleic omega 6
Firmness
PUFA are oils, SFA are solids
-shorter chains are softer at room temperature
-some shorter saturated chains are oils
Stability of FA
Rancidity- spoiling of fats through oxidation (oils go bad faster)
-double bonds are less stable than single bonds
can prevent by: add antioxidants, limit oxygen, heat, and light, and hydrogenation
hydrogenation
adding H atoms to double bonds to make saturated fatty acids
-can cause trans FA (behave like saturated FA and increase cholesterol)
Triglycerides
FAs attached to OH groups, gives off H2O
-ester bond
Phospholipids
one fatty acid gets replaced with choline
-used as emulsifiers
average cell membrane
50% lipids, 75% phospholipids, 20% cholesterol, and 5% glycolipids
Sterols
four fused C rings
-cholesterol is most well known
-plant sterols interfere with cholesterol absorption and can lower blood cholesterol
*starting material for : Vit D3, Estrogen, testosterone, bile, cholesterol
Digestion mouth
chewing breaks down fat
-some hard fats melt at body temp
-food mixes with saliva and lingual lipase
-hydrolyzes the medium-chain FA
Digestion Stomach
strong muscular contractions (grinds solid pieces, disperses fat
-gastrin stimulates release of gastric juices, rich in gastric lipase
-gastric lipase hydrolyzes one fatty acid from tri, and makes a diglycerides
Digestion SI
fat in the duodenum stimulates the release of Cholecystokinin (CCK)- stimulates gallbladder to release bile
Bile-made from cholesterol and amino acid
-bile emulsifies fat droplets into smaller fat droplets
-pancreatic lipase digest the lipids
-monoglycerides and FAs are emulsified by bile to form micelles
Absorption
-glycerol and short and medium chain FA are directly absorbed by diffusion
-monoglycerides and long-chain FA merge into micelles
-once inside the intestinal cells, micelles diffuse and mono and FA are reassembled into TG
Chylomicrons facilitate lipid absorption
long chain fatty acids combine with phospholipids and cholesterol to form chylomicrons
-transport triglycerides from SI through lymph into blood and body cells which remove the lipids
-travel through lymph system, exit lymph and enter bloodstream near the heart
-as chylomicrons move through the the body they pick up TG
bile
most bile is reabsorbed and sent back to liver, but some is excreted because its trapped by soluble fibers (reduces blood choledterol)
Lipoporteins
lipid transport structures
-blood is 55% water
-lipids and proteins help transport lipids through the blood and tissues
Liver
-site of lipid synthesis
-removes remnants of the chylomicrons from the blood and reassembles them into new triglycerides
-new lipids go into a lipoprotein to be transported
VLDL
very low density lipoprotein
-made in liver about 50% of transport
-travel through body and cells remove TGs from them
-as they lose TGs they become more dense
LDL (not bad)
low density lipoprotein- mostly cholesterol
-circulate through body and release TGs, cholesterol and phospholipids to cells
-liver removes LDL from circulation
-delivers lipids to tissue cells
HDL
High density lipoprotein
-transports cholesterol from cells back to liver for disposal
