Chapter 5 - Lipids Flashcards
What are the classes of lipids? (7)
- Fatty acids
- Triglycerides
- Phospholipids
- Sterols
- Fat soluble vitamins
- Wax
- Glycerophospholipids
What are triglycerides?
Glycerol + 3 fatty acids
What are phospholipids?
Glycerol + 2 fatty acids + phosphate group
What are the functions of lipids? (5)
SHIPS
* Storage and source of energy
* Hormonal roles
* Insulation
* Protection
* Structural components (cell membrane)
What is the components/structure of fatty acids?
- Hydrocarbon chain
- Non-polar
- Omega carbon is the terminal carbon
- COOH Carboxyl (acid end)
- CH3 Methyl end
Common fatty acids have _ number of carbons
even
How many carbons are in a short chain fatty acid?
<6 carbons
How many carbons are in medium chain fatty acids?
6-10 carbons
How many carbons are in long chain fatty acids?
12-24 carbons
What does omega mean?
Omega-n refers to the number of the carbon with the first double bond from the methyl end
What is the difference between monounsaturated and polyunsaturated?
Mono has one double bond, while poly has >2
What is the result of oxidized fatty acids in foods?
off/rancid flavours and/or odours
What is the result of oxidized fatty acids in the body?
DNA, cellular damage, macromolecular damage
What fatty acids are most susceptible for oxidation?
Polyunsaturated fatty acids
Oxidation catalysts
- Light
- Heat
- Iron
How are lipid radicals formed?
When hydroxyl radical attack PUFA
LH + OH —> L + H2O
How are lipid peroxyl radicals formed?
When lipid radicals react with oxygen
What does lipid peroxyl radicals do?
Abstract hydrogen atoms from other organic lipid compounds to form lipid peroxides and lipid radicals
How can you prevent oxidation of fatty acids in foods?
- Minimize oxygen exposure
- Add antioxidants
- Blocking light exposure
- Reducing stroage temperature
What reaction occurs to synthesize triglycerides?
Condensation
What type of bond is between glycerol and fatty acids?
Ester bond
How does chain length and # of double bonds affect fluidity?
The shorter the chain length, and the greater amount of double bonds = more fluid
How does chain length and # of double bonds affect stability?
The shorter the fatty acid, and the lower # of double bonds = more stable
What occurs in hydrogenation of triglycerides?
Adds hydrogen to unsaturated fatty acids
What is the bi-product of hydrogenation of triglycerides in foods?
Trans fatty acids
(also changes the cis arrangement of hydrogen to trans arrangement)
What does the trans fat on food labels mean?
what is the source of TFA
It includes both natural fats and industrial hydrogenated fats
Examples
Natural trans fatty acids
- Trans vaccenic acid
- Conjugated linoleic acid
What are the functions of phospholipids? (3)
- Cell membrane structure
- Intracellular messengers
- Emulsifers in foods
Structure of sterols
4 ringed steroid nucleus
-3 rings cyclohexane
-1 ring cyclopentane
What are the sources of sterols?
Cell membranes of
Animals: Cholesterol
Plants: Phytosterols (sitosterol, stigmasterol)
How does cholesterol affect cell membrane fluidity?
High temp: acts to stabilize the cell membrane and increase its melting point
Low temp: nserts into phospholipids and prevents them from interfering with each other
What is cholesterol a precursor for? (4)
- Vitamin D
- Androgens (testosterone and estrogen)
- Corticosteroids (cortisol)
- Bile acids
How is cholesterol transported?
By lipoproteins (VLDL, LDL, CM, HDL)
What are essential fatty acids?
- Linoleic 18:2w6 (omega-6)
- Linolenic 18:3w3 (omega-3)
What are the functions of essential fatty acids?
- Growth and development of braina nd retina
- Prevention of atopic disease
What are essential fatty acids a precursor for?
Inflammatory and cardiovascular modulators: eicosanoids
How are eicosanoids synthesized?
Linoleic acid or linolenic acid turned into Arachidonic acid or Eicosapentaenoic acid; dioxygenases turn it into different eicosanoids
What is the ideal Omega-6:omega-3 ratio?
2-4:1
What is the omega-6:omega-3 ratio found in Western diet?
5-6-10:1
What does lingul/gastral lipase do?
Hydrolyzes medium chain fatty acids or fatty acids at sn-3 on glycerol
What does pacreatic lipase/co-lipase do?
Hydrolyze fatty acids at position sn-1, sn-3
How are lipids absorbed? (3)
- Passive diffusion
- Micelle diffusion
- Carrier mediated transporters on the brush border membrane
When does gastrin release?
When food bolus enters the stomach; releases HCl from parietal cells in the stomach
When does secretin release?
When chyme enters duodenum; targets the pancreas to release neutralizing HCO3 + digestive enzymes
When does CCK release?
When lipids or protein enter the duodenum; targets the gall bladder or pancrease to release bile, or digestive enzymes
When does gastric-inhibitory peptide release?
When glucose/lipid enters the duodenum; targets B-cells in the pancreas which causes insulin secretion
What is enterohepatic circulation?
The movement of bile acid molecules from the liver to the small intestine and back to the liver
Where does cholesterol synthesis occur?
In intestinal cells
Which foods have cholesterol?
Only foods of animal origin contain significant cholesterol
What is the most common form of CVD?
Coronary heart disease
How does corornary heart disease develop?
Atheroschlerosis in the coronary arteries
What are the risk factors of atherosclerotic plaques?
- Raise blood pressure
- Abnormal blood clotting
- Heart attacks
- Strokes
What are the recommendations for preventing or treating CVD?
- Dietary interventions
- Quitting smoking
- Engaging in regular physical activity
How does atherosclerosis develop?
LDL/CM-remnants (chylomicrons) considered atherogenic, and deposit cholesterol in artery walls
How do blood clots develop in CVD?
Platelets cover the damaged area and form a clot
What are platelets are under control of?
Eicosanoids, made from omega-3 and omega-6 fatty acids
Define
Thrombosis
a blood clot that sticks to an artery and grows large enough to restrict or close off a blood vessel
Define
Embolism
When a blood clot breaks free, travels, and lodges in a small artery and shuts off blood flow to tissues
What are the unmodifiable risk factors for CVD?
- Increasing age
- Male
- Family history of premature heart disease
What are the modifiable risk factors for CVD?
- High LDL
- Low HDL
- Hypertension
- Diabetes
- Obesity
- Physical inactivity
- Cigarette smoking
- High SF diet, low in vegetables and whole grains
What are the risk factors for metabolic syndrome?
- Abdominal obesity
- High TG
- Low HDL
- High blood pressure
- High fasting glucose
What type of omega FA synthesis promotes the production of pro-inflammatory eicosanoids?
Omega-6
What type of omega FA synthesis promotes the production of lower bio-activity eicosanoids?
Omega-3
What is the daily recommendation for cholesterol?
<300mg/day
How much cholesterol is in an egg?
200mg
How does dietary fat increase Asthma/IBD/Rheumatoid Arthritis risk?
- Eicosanoid dysregulation and inflammation
- n-3 PUFA beneficial in decreasung risk
How does dietary fat increase Alzheimer’s risk?
- Total fat, SFA, industrial TFA, cholesterol has an increased risk due to neuron function
- n-3 PUFA beneficial in decreasing
ADMR Fat
20-35%
Daily recommendations for SFA and TFA
<10% of energy intake (20g)
What is the AI for n-6 EFA?
- Female: 12g
- Men: 17g
What is the AI for n-3 EFA?
- Female: 1.1g
- Male: 1.6g
Food sources of n-3 EFA
- Flax seeds
- Chia seeds
- Salmon
- Walnuts
- Tofu
- Canola
- Oysters
Food source of n-6 EFA
- Walnuts
- Safflower oil
- Hemp seeds
- Peanut butter
- Eggs
- Almonds
What is the recommendation for fish consumption?
2 servings of fatty fish/week
What fish are high risk for toxicity?
- Fresh/frozen tuna
- Shark
- Swordfish
- Marlin
- Orange rough
- Escolar
