WEEK 5: Lipids Flashcards
(57 cards)
1
Q
What are 3 types of lipids
A
- Triglycerides (fats and oils)
- Phospholipids
- Sterols
2
Q
5 Roles of triglycerides
A
- energy storage
- structural components of membranes
- secretes hormones
- insulates
- shock absorbers
3
Q
Describe the structure of a triglyceride
A
- glycerol + 3 fatty acids
-Fatty acids vary in carbon chain lengths, degree of unsaturation and number of double bonds. - Saturation affects the physical characteristics of the fat and its storage properties.
4
Q
What are the three types of fatty acids chain length
A
- Short(1–5C’s)
- Medium(6–12C’s)
- L o n g(13–21C’s
5
Q
What are the 3 types of bonds in fatty acids
A
- saturated
- monounsaturated
- polyunsaturated (omega-6; omega-3)
6
Q
What are the 3 essential fatty acids
A
- Saturated fats
- Monounsaturated fats
- Polyunsaturated fats
-> Linoleic Acid (omega 6)
-> Alpha -linolenic Acid (omega 3)
We cannot make these EFA so they must be supplied by the diet
7
Q
What is a fatty acids structure
A
- a chain of carbon and hydrogen atoms with an acid group (COOH) at one end and a methyl group (CH3) at the other end
8
Q
Describe the triglyceride formation
A
- H atom form glycerol +OH group from fatty acid = water
- # leaving O on glyceral + C at acid end of each fatty acid = form a bond3 fatty acids + glycerol form triglyceride and yield water
9
Q
What is an unstaruated fatty acid
A
lack hydrogen atoms and have at least one double bond.
10
Q
What is a double bond considered?
A
the point of unsaturation.
11
Q
What is a monounstaturated fatty acid + 3 food sources
A
lack two hydrogen atoms and have one double bond.
- avo, nuts, oils
12
Q
What is a polyunsaturated fatty acid
A
- lack four or more hydrogen atoms and have at least two or more double bonds.
13
Q
What does the omega number refer to
A
positionofthe first double bond.
14
Q
What is saturated fatty acid effect on the body
A
- often found in animal based food products eg bacon,meats, dairy
- when eaten in excess can lead to increased risk of heart disease and weight gain
15
Q
What is unsaturated fatty acid effect on the body
A
(mono and polyunsaturated) play an important role in a healthy diet and can help to reduce the risk of heart disease.
16
Q
What are 2 examples of fatty acids and there biochemical abbreviations?
A
Stearic acid, saturated fatty acid=C:18
Linoleic acid, polyunsaturated fatty acid=C:18:2 n-6
17
Q
How can Linoleic acid (omega-6 fatty acid) be supplied by diet
A
can be supplied by vegetable oils and meats.
- non hydrogenated margarine, mayo, nuts
18
Q
How can Linolenic acid (omega-3 fatty acid)be supplied by diet
A
must be supplied by food. It is important for the eyes, brain and heart. It is found in oils, nuts, seeds, fish and seafood.
19
Q
What are eicosanoids made from and what they include
A
- made from arachidonic acid and EPA are ‘hormone like’
- they include prostaglandins, thromboxanes and leukotrienes
- Require adequate long chain fatty acids for synthesis.
20
Q
Classic fatty acid deficiency symptoms include
A
growth retardation, reproductive failure, skin lesions, kidney and liver disorders
21
Q
4 Physical Properties of Saturated Fats
A
- Saturated fatty acids carry the maximum possible number of hydrogen atoms
-When most of the fatty acids are saturated it is called a saturated fat - Solid at room temperature
- Resistant to oxidation
22
Q
4 Physical Properties of Unsaturated Fats
A
- Poly unsaturated fats are liquid at room temperature
- Shorter fatty acid chains are softer at room temperature than longer chains
- MUFA - slightly less susceptible to spoilage, PUFA ->spoils most readily
- Hydrogenation -> Trans fats
-> Protects against oxidation, therefore prolonging shelf life.
-> Alters texture
23
Q
How does the degree of unstaruation influence fats and oils in foods
A
- firmness
- stability
24
Q
How does the degree of usntruartion affect the firmness of fats
A
- most polyunsaturated vegetable oils are liquid at room temp
- more saturated animal fats are solid
- Some oils are saturated= firmer than most vegetable oils because of their saturation/softer than most animal fats because of their shorter carbon chains (8-14 long)
25
How does the degree of unstarvation affect the stability of fats
- oxidation of fats prods a variety of compounds that smell and taste rancid
-PUFA spoil most readily because their double bonds are unstable
-MUFA are slightly less susceptible
- Saturated fats most resistant to oxidation and least likely to become rancid
- to preventL fat containing products sealed tightly+nolgiht+refiregerated
- add antioxidants
- products may undergo hydrogenation
26
What is hydrogenation and 3 advantages
- some or all of the points of unsaturation are saturated by adding hydrogen molecules
- protects against oxidation (prolonging shelf life) by making polyunsaturated fats more saturated.
- alters the texture of foods by making liquid vegetable oils more solid
- after fat is partially hydrogenated-> double bonds change from cis to trans
27
What are cis double bonds
hydrogens next to the double bonds are on the same side of the carbon chain
- molecules fold back in a u shape
- naturally occurring in unsaturated fatty acid foods
28
What are trans fatty acids + 3 food sources
- hydrogens next to the double bonds are on opposite sides of the carbon chain
- molecules more linear
- behave more like saturated fats, increasing blood cholesterol and the risk of heart disease
- fast foods, snacks, commercial foods, fried
29
What is the strucuture of phospholipids, function and found in what foods
- Structure generally consists of hydrophobic tails and a hydrophillic head
- Can be used as emulsifiers in food industry (e.g. lecithin)
- Food sources of lecithin include eggs, liver, soybeans, wheatgerm and peanuts.
- Enable transport of lipids across cell membranes.
30
Describe structure of lecithin
- contains only two fatty acids.
- third position is occupied by a phosphate group and a molecule of choline
31
What are sterols structure, most common and where found
- multiple ring structure.
- A well-known sterol is cholesterol.
- Found in plan stand animal foods.
- Cholesterol (asterol) is found in animal foods only – meat, eggs, fish, poultry and dairy products
32
What is the 3roles of sterol
- Starting material for bile acids, sex hormones, adrenal hormones and vitamin D.
- Structural component of cell membranes.
- Liver produces 800 to 1500 mg cholesterol per day
33
What is atherosclerosis
a disease that causes heart attacks. It occurs when cholesterol forms deposits in the artery wall.
34
How is lipids digested in the mouth
some hard fats beginning to melt when they reach body temp
- salivary gland at the base of the tongue releases lipase
- infants= this enzyme efficiently digests the short- and medium-chain fatty acids found in milk
35
How is lipids digested in the stomach
- fat float as a layer above the other components of swallowed food
- strong muscle contractions of the stomach propel the stomach contents towards the pyloric sphincter
- some chyme passes through the pyloric sphincter-> remaining partially digested food propelled back into the body of the stomach
- churning grinds the solid pieces to finer particles, mixes the chyme and disperses the fat into smaller droplets
- help to expose the fat for attack by the gastric enzyme lipase
36
How is lipids digested in the small intestine
- fat triggers the release of the hormone cholecystokinin (CCK), which signals to the gall bladder to release its stores of bile
- bile acids= made in the liver from cholesterol and have a similar structure
- pair up with an amino acid=end is attracted to water, and the sterol end is hydrophobic
- structure enables bile to act as an emulsifier, drawing fat molecules into the surrounding watery fluids
- fully digested fats encounter lipase enzymes from pancreas and small intestine
- pancreatic lipases remove each of a triglyceride’s outer fatty acids one at a time=monoglyceride
- ocassionaly enzymes remove all three fatty acids= free molecule of glycerol
- phospholipids fatty acids are removed by hydrolysis
- two fatty acids and the remaining glycerol and phosphate fragments are then absorbed
- sterols can be absorbed as is-> if any fatty acids are attached, they are first hydrolysed off
37
Describe the Enterohepatic circulation
- liver=bile made from cholestorol
- gallbladder= bile is stored
- small intestine = bile emulsifies fats
- bile reabsorbed into blood
- in the colon, bile that's been traped by soluble fibers lost in feces
38
How are lipids absorbed
- Small molecules of digested triglycerides (glycerol and short- and medium-chain fatty acids) can diffuse easily into the intestinal cells-> they are absorbed directly into the bloodstream.
- monoglycerides and long-chain fatty acids) merge into spherical complexes known as micelles
->diffuse into the intestinal cells, where the monoglycerides and long-chain fatty acids are reassembled
into new triglycerides
->then Packed with protein to become chylomicrons~> into lymph ~> blood via heart
39
How are lipids transported in the body
- group of vehicles known as lipoproteins
- Chylomicrons – largest of the lipoproteins.
-> Least dense
-> Get smaller as triglyceride portion is removed by the cells
-> Transport to the liver
40
The 3 types of lipoproteins in the liver, structure, function
-VLDL (Very-Low-Density Lipoproteins)
- composed primarily of triglycerides
- Made by the liver
-> transport lipids to the tissues
-> Get smaller and more dense as triglyceride portion is removed – then becomes LDL’s
- LDL (low-density lipoproteins) – composed primarily of cholesterol -> Transport lipids to the tissues
- HDL (high-density lipoproteins) – composed primarily of protein -> collect from blood and bring back to liver
-> Transport cholesterol from the cells to the liver
41
What percentage does ft provide to energyrequirements when body at rest
60%
42
Conversion of fat kg to kJ
1kg fat provides 30000kJ.
- Require carbohydrate or protein for complete breakdown of fat.
43
What are the 3 main products of the fermentation of fiber
- SCFA
-Gases
- Energy
44
What is SCFA
stimulate colonic blood flow and fluid and electrolyte uptake, growth of bacteria already in colon
45
What are 3 types of scfa
Acetate Propionate Butyrate
46
What is acetate
Enters circulation, metabolized by peripheral tissues, ? appetite reg
47
What is Propionate
Taken up by liver, lowers cholesterol
48
What is Butyrate
- Energy for cells lining the colon, anti- cancer/immune function
49
What is the macronutrient fat
commonly found in variety of foods and therefore getting enough fat in our diets is rarely an issue
- certain fats can contribute to the risk of chronic diseases, many fats are essential for good health
- vary in their chemical shape and form, saturation of chemical bonds with hydrogen atoms
- Saturation affects the physical characteristics of fat and its storage properties.
50
What is saturation based on
how many hydrogens are present in the chemical structure of the fatty acid.
51
What are blood profile levels, and the 4 desirable levels
Reveal concentrations of lipids in the blood
– Total cholesterol < 4 mmol/L
– LDL cholesterol < 2.5 mmol/L
– HDL cholesterol > 1 mmol/L
– Triglycerides < 2.0 mmol/L
52
What is cholesterol,
Elevated LDL/VLDL=CVD risk factor
- accumulates in blood essels and↑ BP
- However, cholesterol intake has much less effect on blood cholesterol than saturated fat and trans fat
-People with ↑ blood cholesterol may benefit from limited cholesterol to <200 mg/d
53
What is the impact of trans fat and food sources
increase LDL cholesterol and decrease HDL cholesterol
- ↑inflammation and insulin resistance
- Food sources:
– include deep-fried foods using vegetable shortening, cakes, biscuits, doughnuts, pastry, crackers, snack chips, margarine,
– meat and dairy products
54
What is the impact of omega 3+6
- EPA/DHA eicosanoids help↓BP,↓clotting, ↓inflammation
- Some n6 promote inflammation but only to apoint, other n6 reduce
- Potentially useful in arthritis,allergy,nervepain
55
What are omega 3 best sources: EPA/DHA, ALA
EPA/DHA: Atlantic salmon, mackerel, sardines, tuna (omega-3 rich)
Human breast milk
ALA: flaxseed, canola, walnut, wheat germ, soy bean oil, Nuts & seeds, soy bean
56
What is a plant cholesterol
- Can interfere with cholesterol absorption.
– Examples include Logicol and Flora Proactiv
- Needs to be taken in sufficient quantities
57
What are fat intake recommendations
-Limit intake of saturated fats
-Proportion of energy in the diet from saturated and trans fat together should be less than 8-10% of daily energy intake
- Moderate fat intake to maximum of 35% of daily total energy intake
- On an average daily intake of 8000kJ, this equals to 640-800kJ (17.5 to 21g) from saturated and trans fat combined
