LIPIDS Flashcards
Lipids are ____ in water and ____ in non-polar solvents
Insoluble; Soluble
Type of linkage present in lipids
Glyceride linkage
How are lipids energy dense?
(kcal)
It provides 9kcal/g
Why are lipids energy dense?
The long fatty acid chains can be separated and used for glycolysis
Common animal sources of lipids
fatty meats, butter, lard, cheese, whole milk, cream, egg yolk
Common plant sources of lipids
vegetable oil, nuts, chocolate, avocado, durian, olives, margarine
Foods that are purchased and used as fats|
(ex. butter, margarine, cooking oil)
visible fats
Which part of the egg consists of lipids and which are for proteins
egg yolk for lipids (cholesterol), egg white for protein
Examples of invisible fats
egg yolk, cheese, milk, cream, and salad dressings
What is the difference of fats and oils
fats: solid at room temp. and came from animal sources
oils: liquid at room temp. and came from plants sources
What are the 6 main purposes of lipids
- Energy storage
- Transport of fat soluble vitamins
- Supply essential fatty acids
- Protect & support organs and bones
- Insulate from cold temperatures
- Provide satiety
Lipid Storage
what is the starting material for fatty acid synthesis
acetyl-CoA
Lipid Storage
Importance of malonyl-CoA
Inhibits fatty acid beta-oxidation to ensure storage of fat
Lipid Storage
What is the purpose of inhibiting fatty acid oxidation
(Importance of ensuring fat is stored)
To balance energy storage and utilization
Storage: ensure backup energy & prevents wasteful expenditure of energy
Lipid Storage
Raw material for synthesis of Malonyl-CoA
Acetyl-CoA
Lipid Storage
What specific enzyme does malonyl-CoA inhibits
carnitine acyl transferase
Transport of fat soluble vitamins
What are the fat-soluble vitamins
Vit. A, D, E, K
Essential fatty acids
What are the essential fatty acids
Omega 3 & Omega 6
Body Insulation
How does fat insulate the body
Cold temperature triggers brown adipose tissue to release stored energy in the form of heat
Lipid Family
3 main types of lipids in the body
- Triglycerides
- Phospholipids
- Sterols
basic structure of triglycerides
1 molecule of glycerol with 3 fatty acid chain attachments
why are triglycerides considered space saving efficient molecules for storing energy?
- energy dense
- Their neutrality and nonpolar characteristics allow them to be stored in anhydrous environment and they will not expand from water uptake
How are fatty acids classified?
- essentiality
- degree of saturation
- chain length
Differentiate essential from non-essential
Essential: cannot be synthesized by the body and must be supplied by diet
Non-essential: can by synthesized by the body
Difference of omega 3 and omega 6
Omega 3: first double bond located at 3rd carbon from methyl end
Omega 6: first double bond located at 6th carbon from methyl end
members of the omega 3 family
- alpha linolenic acid
- eicosapentoic acid
- docosahexaenoic acid
ALA (18:3)
EPA (20:5)
DHA (22:6)
food sources for ALA
flax seed (57%) meal and oils, canola (8%) oils, soybean (7%) oils, walnut, butternuts, red & black currant seeds
food sources of EPA and DHA
cod liver oil, fish oil capsules, mackerel, salmon, sardines, bangus, crab, shrimp, oysters
Benefits of omega 3 FAs
- growth and development of fetal CNS and retina
- CVD: decrease triglycerides
- precursore for prostaglandins
Purpose of prostaglandins
to cause inflammation, pain, and fever as part of the healing process. Can also causes muscle contraction to prevent blood loss
what does thromboxane do during the healing process
produced by platelets to stimulate blood clot
major food sources of omega 6
vegetable oils (corn, sunflower, cottonseed), salad dressings, margarine
(common in plants)
members of the omega 6 family
- linoleic acid
- gamma linoleic acid
- arachidonic acid
LA (18:2)
GLA (18:3)
AA (20:6)
benefits of omega 6 FAs
- CVD: associated with decreased levels of LDL and HDL
- Deficiency: growth retardation, skin lesions, reproductive failure, fatty liver, polydipsia
what are the two parent members of the omega 3 and 6 families
Omega-3: alpha linolenic acid
Omega-6: linoleic acid
what is the ratio of omega 3 and omega 6
1 omega 3: 4 omega 6
why is there a difference in amount of omegga 3 and 6 fatty acids
because omega 3 and omega 6 compete for the same enzyme for elongation
Difference of saturated and unsaturated fatty acids
Saturated: all carbons carry the max hydrogens possible; solid at room temp; usually from animal products
Unsaturated: contains double bonds; liquid at room temp; usually from plants
common food source of saturated fats
meat, egg yolks, whole milk, whole milk cheeses, cream, ice cream, butter, chocolate, coconut and palm oil
2 types of unsaturated fats
monounsaturated and polyunsaturated fats
difference of mono and polyunsaturated fat
monounsaturated: one double bond
polyunsaturated: more than one double bond
common food source of monounsaturated fats
olive oil, canola oil, avocados, cashew nuts
benefit of monounsaturated fats
may raise HDL without raising LDL
why is palm oil not environmentally friendly
plantation of palm trees require clearing massive lands leading to deforestations, habitat destruction, etc.
consistency or texture of polyunsaturated fats
usually soft or oily
examples of polyunsaturated fats
omega 3 and omega 6
why is omega 6 not 100% protective
may produce free radicals
must be taken with antioxidants to prevent this
__ is the process of adding hydrogen to polyunsaturated vegetable oils, forming __
Hydrogenation, Trans fats
purpose of hydrogenation
solidifying (semi-solid) oils at room temp.
why do we want the solid or semi-solid form of fats
prolong shelf life and makes it pliable to use
effect of trans fat
raise LDL and total cholesterol
common sources of trans fat
baked goods and restaurant foods
difference of the categories in classifying fatty acids by chain length
short: <6 carbons
medium: 6-10 carbons
long: 12-24 carbons
components of phospholipids
glycerol, fatty acids, choline (or nitrogen-containing compound), and a phosphate group
where are phospholipids synthesized
liver
functions of phospholipids
- emulsifies in food industry and body
- constituent of cell membrane
a momdel that describes the structure of the plasma membrane
fluid mosaic model
example of sterols
cholesterol
functions of sterols
- starting material for body compounds such as bile, sex hormones, adrenal hormones, vit. D and cholesterol
- structural component in cell membranes
T or F: cholesterol only exists in animal products
true
T or F: cholesterol is needed by every cell in the body
true
what materials from fats and lipids can be absorbed by the body
(when dismantled)
monoglycerides, fatty acids, glycerol
how are lipids digested in the mouth
- fat begins to melt in mouth
- lipase is secreted by salivary glands to start digesting medium and short chain fatty acids (milk)
type of lipase secreted by ____ salivary glands
lingual lipase from sublingual salivary glands
T or F: fat is digested stomach
true: but only very little amount
type of enzyme to digest lipids in stomach
gastric lipase
what hormone signals the release of bile from gallbladder
cholecystokinin (cck)
what triggers the release of cck to release bile from gallbladder
food containing lipids and proteins detected by the cells on the mucosal lining of the duodenum
how does bile help in digestion of lipids
bile acts as emulsifier
enzyme to digest cholesterol
cholesterol esterase
what is the mode of action of the enzyme to digest cholesterol
hydrolysis
enzyme secreted by pancreas for lipid digestion
pancreatic lipase
T or F: small intestines release enzyme to digest lipids
True: intestinal lipase
product of lipid digestion in mouth
diglycerides and free FA
product of lipid digestion in stomach
70% triglyceride, free FA, partially digested fats
product of the interaction between fat and bile
emulsified fat
product of cholesterol digestion
esters of cholesterol and fatty acids
product of lipid digestion in small intestine
monoglycerides, phospholipid fragments, sterols, and free FA
how are small units of lipids absorbed in the body
diffuses into intestinal cells into the bloodstream
how are larger units of lipids absorbed in the body
they merge into micelles to diffuse into the intestinal cells
what happens to large units of lipids once they diffuse into the intestinal cell?
assemble into triglycerides to be packed into chylomicrons which are released to the lymphatic system
(95-97% of dietary fat)
what is the basic unit for lipid catabolism
acetyl CoA
what does beta oxidation do
cleaves carbon at a time
what are the two molecules and their respective pathways in lipid catabolism
glycerol: glycolysis
fatty acids: beta oxidation
process of converting acetyl CoA and glyceraldehyde-3-phosphate to adipose tissue
lipogenesis
step before glyceraldehyde-3-phosphate undergoes lipogenesis
conversion to glycerol by removing 2 phosphates
what are the two possible products of acetyl CoA when turned into HMG CoA
cholesterol and ketone bodies
what happens if ketone bodies accumulate in the body
ketoacidosis (lowering of pH)
products of acetyl CoA after turning into malonyl CoA
triacylglycerides and phospholipids
what are the components of lipoproteins
triacylglycerols, phospholipids, cholesterol and protein
function of lipoproteins
main transport form of fat
why are VLDL, LDL, and HDL called density proteins
due to protein content (more protein, higher density)
%protein of each lipoprotein
chylomicron (2%)
VLDL (10%)
LDL (25%)
HDL (40%)
what do chylomicrons transport and what is the pathway of transport
transport diet-derived triglycerides; from small intestine to liver and other tissues
what do VLDL transport and what is the pathway of transport
triglyceride; from liver to body cells
what do LDL transport and what is the pathway of transport
cholesterol; from liver to body cells
what do HDL transport and what is the pathway of transport
cholesterol; from body cells and blood back to the liver
T or F: the density of lipoproteins is proportional to its size
False: the least dense is the chylomicron and is also the largest lipoprotein
why is HDL considered “good cholesterol”
HDL can carry cholesterol from the plaque deposits in the arteries
why are non-HDL considered “bad cholesterol”
serves as raw material for plaque in blood vessels
purpose and mechanism of calcium blockers
relieve pressure by blocking calcium channels into smooth muscle cells, making the muscles contract less
lipid functions when stored as adipose tissue
- insulation
- support vital organs
- generate heat
- energy reserve
what happens to lipids when in blood as lipoproteins
- excreted in feces (small amounts)
- converted to brain and nerve tissue
- oxidized for energy
- synthesized from carbohydrates and proteins
- stored as energy reserve
how much fat do adults need
(range)
15-30%
disadvantage of ketogenic diet
fat heavy diet and onset of gout
saturated fats that increase LDL
lauric, myristic, and palmitic acid
what are fat replacers
substitute fat in foods to give a similar taste, texture and mouth feel as a full fat food
purpose of fat replacers
reduce fat and calories in food
types of fat replacers
carbohydrate-based, protein-based, and fat-based
examples of carb-based fat replacers
guar gum, polydextrose (Litess), gum Arabic, xanthum gum, carrageenan (an extract from seaweed), dried plum paste, modified food starches, oat fiber, and wheat fiber
characteristic of carb-based fat replacer
they have the creaminess of fat
where do protein-based fat replacers come from
milk proteint and/or egg white protein
characteristic of protein-based fat replacer
give same mouth feel as fats
process of making protein-based fat replacers
microparticulaton
example of fat-based fat replacers
Caprenin, Benefat, Olean
If fat-based fat replacers are made of fat molecules, how does it become a “fat replacer”?
(for Olestra)
Extra fatty acids are added to increase molecule size, making it too large to be absorbed and simply passes through the intestines to be eliminated as waste
(Not all fat-based replacers. Some are only partially absorbed.)
T or F: all fat replacers are considered safe
True
Even though Olestra does contribute to fat and caloric intake, what are its disadvantages
- Not for people with disorders that interfere with nutrient absorption
- Reduces absorption of fat-soluble vitamins
- May cause loose stools and diarrhea
