FOOD20003 Chapter Notes - Chapter 5: Avocado, Cardiovascular Disease, Very Low-Density Lipoprotein
28 Jun 2018
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TUTE 6 – LIPIDS (CHAPTER 5)
1. Why are fats called fatty acids? (p. 123)
Lipids has more C & H in proportion to O provides more energy than carbs
Fatty acid = organic acid
Fat = 3FA + glycerol molecule
2. What chemical features distinguish fatty acids from each other? (pp. 123–129)
Length of carbon chain
oFrom 4 carbons to 24 carbons
Degree of unsaturation – influence firmness & stability
oSaturated = fully loaded with hydrogens NO DOUBLE BONDS
Usually solid
oUnsaturated = has double bonds
Can be mono-unsaturated or poly-unsaturated
Usually liquid
Poly-unsaturated are usually unstable react readily
Location of first point of unsaturation
oi.e. next to third carbon from omega carbon (omega-3)
oor next to the sixth carbon (omega-6)
3. What does the term omega mean with respect to fatty acids? Describe the roles of the omega fatty
acids in disease prevention. (pp. 124–125, p. 144)
Omega-3 fats – memory, cognition, blood lipids, heart diseases
oReduces risk of heart disease & stroke
oHelp prevent blood clots, protect against irregular heartbeats
oLower blood pressure (esp. people with hypertension/atherosclerosis)
oEssential in the development of the brain
Neurotransmitter function
Hence, important to supply optimal levels of omega-3 during pregnancy
4. What are the differences between alpha-linolenic acid and linoleic acid? PUFA family (pp. 139–140)
Alpha-linolenic:
oOmega-3
o3 double bonds
Linoleic acid: precursor for omega-6 (arachidonic acid)
oOmega 6
o2 double bonds
Both acids are essential cannot be made in the body
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oMust be supplied by foods in diet
5. What does hydrogenation do to fats? What are trans-fatty acids and how do they influence heart
disease? (pp. 128–129)
Adding hydrogens break up the double bonds
Advantages:
oProtect against oxidation by making polyunsaturated more saturated
Prolongs shelf life
oAlters the texture of foods by making liquid more solid (harder)
i.e. making margarine spreadable etc
usually fat = partial hydrogenated
othe double bond that remains can be cis or trans
oa small % changes to trans-fatty acids (more linear)
these arrangements result in different configuration of the FA
behaves more like a saturated fat than unsaturated (increases LDL, reduce HDL)
has health effects similar to a saturated fat (heart diseases)
6. How do phospholipids differ from triglycerides in structure? How does cholesterol differ? How do
these differences in structure affect function? What are their roles? (pp. 129–132)
Phospholipids has a glycerol backbone + 2 fatty acid + phosphate group
oPhosphate group = hydrophilic & fatty acid = hydrophobic (emulsifiers)
oAssembled into an orderly formation cell membrane
oHelp move fat-soluble substances across the cell membrane (in watery environment)
in/out of cell
Help mix fat and water
Cholesterol = type of sterol (produced in liver)
oCompounds with a multiple-closed-ring structure
oServes as starting material for bile acids, steroid hormones & vitamin D
oAlso, structural component of cell membrane
oHarmful only when it forms deposits in the artery walls
Leads to atherosclerosis (causes heart attacks/strokes)
7. What do lipoproteins do? What are the differences among the chylomicrons, VLDL, LDL and HDL?
(pp. 136–138)
Lipoproteins = lipids + proteins
oMore lipids = lower density
oMore proteins = higher density
Role: Transports fat through the watery bloodstream
Chylomicrons (low density)
oTransport diet-derived lipids (triglycerides) from the intestine (via lymph) to the rest of the
body
oCells from the body remove triglycerides from the chylomicrons as they pass-by
Hence, chylomicrons get smaller and smaller
After ~14hrs, most triglycerides have been removed from chylomicrons
Special protein receptors on membrane of liver cells recognised & remove
these chylomicrons remnants from the blood
They are dismantle for re-use/recycle
Very-low-density lipoproteins (VLDL)
oLipids made in liver + those collected from chylomicrons packaged with protein as VLDL
oAs VLDL travel through the model, cells remove triglycerides
oAs triglycerides = lost VLDL shrinks density increases
oThe remaining cholesterol-rich lipoprotein eventually becomes LDL explains why LDL
contains little amounts of triglycerides but has lots of cholesterol
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find more resources at oneclass.com
Document Summary
Tute 6 lipids (chapter 5: why are fats called fatty acids? (p. 123) Lipids has more c & h in proportion to o provides more energy than carbs. Fat = 3fa + glycerol molecule: what chemical features distinguish fatty acids from each other? (pp. Length of carbon chain: from 4 carbons to 24 carbons. Degree of unsaturation influence firmness & stability: saturated = fully loaded with hydrogens no double bonds. Usually solid: unsaturated = has double bonds. Describe the roles of the omega fatty acids in disease prevention. (pp. Linoleic acid: precursor for omega-6 (arachidonic acid: omega 6, 2 double bonds. What are trans-fatty acids and how do they influence heart disease? (pp. Adding hydrogens break up the double bonds. Advantages: protect against oxidation by making polyunsaturated more saturated. What are the differences among the chylomicrons, vldl, ldl and hdl? (pp. Lipoproteins = lipids + proteins: more lipids = lower density, more proteins = higher density.
