Chapter 6 Lipids Flashcards
Triglyceride
甘油三酸酯
Three types of lipids
Triglycerides, phospholipids, and sterols
What can lipid solute in?
Lipids cannot solute in water, but can dissolve in organic solvent, like chloroform, benzene, and ether.
The most common type of lipid
Triglyceride, most common in food and body. 95% of the fat we eat and stored in body is triglyceride.
Structure of triglyceride
Three fatty acids attached a glycerol as backbone.
Esterification
The process of attaching fatty acids to glycerol is called esterification. One water molecule will be released when each fatty acid bonds to glycerol.
Hydrolysis
The release of fatty acids from glycerol.
Basic structure of free fatty acids
Long chains of carbon atoms linked together and surrounded by hydrogen atoms.
Carbon Chains vary in three ways
The number of carbon in one chain, the extent to which the chain is saturated with hydrogen, and the shape of chain (straight or bent).
Long-chain fatty acid
Have 12 or more carbon atoms. Fatty acid in beef, lamb, pork, and most plant oil is long-chain fatty acid. It need longest time to digest and transport via lymphatic system.
Medium-chain fatty acid
Have 6 to 10 carbon atoms. It digest as quickly as glucose, and it transport via portal system. Coconut and palm kernel oil is example of it.
Short-chain fatty acid
Less than 6 carbon atoms. They are rapidly digested and transported via portal system. 3% of the fat in butter is short-chain fatty acid.
How many bonds can carbon, oxygen, and hydrogen form?
Carbon: 4
Oxgen: 2
Hydrogen: 1
Number of double bonds or polyunsaturated fatty acid
at least 2
The shape of (un)saturated fatty acid
The shape of saturated or trans fatty acid is straight, and the shape of unsaturated fatty acid is bent or kinked.
The shape of trans fatty acid
The double bonds of it zigzag back and forth across the carbon chain. It has hydrogen next to the double bonds on opposite sides of the carbon chain, is straight and resembles a saturated fatty acid.
Hydrogenation
Hydrogenation adds hydrogen to carbon chain of unsaturated fat. As the amount of added hydrogen increases, the unsaturated acid becomes more and more saturated and increasingly solid.
PUFAs
Polyunsaturated fatty acids
Essential fatty acids
Linoleic acids(omega-6) and Alpha linoleic acids(omega-3)
Why we can only get EFAs from food?
Because human’s body cannot synthesize essential fatty acids with double bond before the 9th carbon in the chain, counting from the omega end.
What identify the fatty acid’s family?
The location of the first double bond closest to the omega carbon (methyl ends) identified the fatty acid’s family. If the first double bond occurs after the 6th carbon on the chain, it is called an omega-6 fatty acid.
EPA and DHA are made from
Alpha linoleic acid
Eicosanoids
Are hormone like compounds that affect the region of body where it is produced. They are called of local hormones, because they are produced and used at the same place.
Hidden fat
In some foods, hidden fat is invisible like whole milk, cheese, cookies, cakes. We need to read the nutrient label to get more information.
Replacement of fat
In order to reduce the fat intake of consumers and still enjoy the mouthfeel, food companies use water, protein, or forms of carb such as fiber, starch derivatives, and gums to replace the fat. Those things are made of fat and sucrose, but contain few or no calories, because they are hard to digest and absorbed.
trans fatty acids
反式脂肪酸
Source of saturated fatty acid
Coconut oil, butter, palm oil, lard or beef fat.
Source of monounsaturated fatty acid
Olive oil, Canola oil, peanut oil.
Source of polyunsaturated fatty acid
Safflower acid, Sunflower acid, Corn oil, Soybean oil.
Source of trans fatty acid
Tub margarine, stick margarine, shortening
Functions of triglycerides
Provide energy, provide compact energy storage, insulate and cushion vital organs, help transport nutrients to bloodstream.
How much energy can triglycerides provide per gram
9 cal/g