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lipids - cj
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lipids - cj
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1
Question
What are lipids?
Answer
Lipids are organic compounds found in living organisms that are insoluble or sparingly soluble in water but soluble in nonpolar organic solvents such as ether, acetone, and carbon tetrachloride. They contain C, H, and O2, and sometimes contain N and P. Most lipids yield fatty acids on hydrolysis or combine with fatty acids to form esters. They also serve as food for the body and take part in plant and animal metabolism.
2
Question
How can the carbohydrates be hydrolyzed?
Answer
Hydrolyzing a carbohydrate will result in monosaccharides.
3
Question
What is the result of hydrolyzing proteins?
Answer
Hydrolyzing proteins will yield free amino acids.
4
Question
What happens when lipids are hydrolyzed?
Answer
When lipids are hydrolyzed, fatty acids are obtained. Not all lipids are composed of fatty acids, but the presence of fatty acids is common on hydrolysis.
5
Question
How are lipids characterized since they do not have a common structural feature?
Answer
The characterization of lipids is based on their solubility characteristics since they do not have a common structural feature.
6
Question
What functions do lipids serve in the body?
Answer
1. Store chemical energy and C atoms in the body (approx 36 kJ/gram). 2. Surround and insulate vital body organs as a shock absorber. 3. Prevent excessive loss of energy. 4. Act as components of cell membranes, including phospholipids, glycolipids, and cholesterol. 5. Serve as chemical messengers and hormones.
7
Question
What are the five categories of lipids based on lipid functions?
Answer
1. Energy Storage Lipids (Triacylglycerols). 2. Membrane Lipids (Phospholipids, Sphingoglycolipids, and Cholesterol). 3. Emulsification Lipids (Bile acids). 4. Messenger Lipids (Steroid hormones and eicosanoids). 5. Protective Coating Lipids (Biological waxes).
8
Question
What are fatty acids and what are the types of fatty acids?
Answer
Fatty acids are organic acids found in natural fats. The types of fatty acids include: 1. Saturated Fatty Acids (SFAs) - Fatty acids with a carbon chain where all carbon-carbon bonds are single bonds, without any double bonds. 2. Monounsaturated Fatty Acids (MUFAs) - Fatty acids with a carbon chain containing one carbon-carbon double bond in cis configuration. 3. Polyunsaturated Fatty Acids (PUFAs) - Fatty acids with a carbon chain containing two or more carbon-carbon double bonds.
9
Question
How is the shorthand system used to specify fatty acids?
Answer
A shorthand system using two numbers separated by a colon is used to specify the number of carbon atoms and the number of carbon-carbon double bonds present in a fatty acid. For example, 18:3 refers to a fatty acid with 18 carbon atoms and 3 carbon-carbon double bonds.
10
Question
What are the different families of unsaturated fatty acids based on double bond position?
Answer
The different families of unsaturated fatty acids are denoted by using the Greek lower case letter omega. The families include: - Omega-3 fatty acids (double bond position starts at omega-3 from the methyl end). - Omega-6 fatty acids (double bond position starts at omega-6 from the methyl end).
11
Question
How do saturated and unsaturated fatty acids differ in their physical properties?
Answer
Saturated fatty acids fit closely together in a regular pattern with many dispersion forces between the carbon chains, requiring more energy and higher temperatures to separate before melting. Unsaturated fatty acids, with double bonds causing the chain to bend or kink, have fewer dispersion forces, resulting in lower energy requirements for separation and lower melting points.
12
Question
What are triacylglycerols and how do they function in the body?
Answer
Triacylglycerols are lipids formed by esterification of three fatty acids to a glycerol molecule. They function as energy storage materials in the body, concentrated primarily in special cells called adipocytes. Triacylglycerols can be simple (composed of the same fatty acids) or mixed (composed of different fatty acids).
13
Question
What is attached to a sphingosine molecule and an alcohol attached to the phosphate group?
Answer
One fatty acid and one phosphate group are attached to a sphingosine molecule, and an alcohol is attached to the phosphate group.
14
Question
How is the fatty acid attached to the sphingosine NH2 group?
Answer
The fatty acid is attached to the sphingosine NH2 group via an amide linkage.
15
Question
How is the phosphate group attached to the sphingosine terminal OH group?
Answer
The phosphate group is attached to the sphingosine terminal OH group via an ester linkage.
16
Question
What is esterified to the phosphate group in addition to the alcohol?
Answer
An additional alcohol is esterified to the phosphate group.
17
Question
What is the structure of a sphingomyelin molecule?
Answer
A sphingomyelin molecule consists of a polar head, which is the phosphate group with its esterified alcohol, and two tails. One tail is a fatty acid, and the other tail is the long carbon chain of sphingosine.
18
Question
What happens in multiple sclerosis related to sphingomyelin?
Answer
In multiple sclerosis, sphingomyelin is lost from the myelin sheath, leading to the formation of scars on the neurons. These scars impair the transmission of nerve signals.
19
Question
Describe the structure of cholesterol and how it differs from other membrane lipids.
Answer
Cholesterol is a specific compound, not a family of compounds, and its structure differs from other membrane lipids in two main ways: 1) It does not contain fatty acid residues, and 2) It lacks glycerol or sphingosine as the platform molecule. Cholesterol is a C27 steroid molecule that is a component of cell membranes and a precursor for other steroid-based lipids.
20
Question
What is the role of low-density lipoproteins (LDLs) in the body?
Answer
Low-density lipoproteins (LDLs) carry cholesterol from the liver to various tissues in the body. They deliver cholesterol to organs for various functions.
21
Question
Explain the function of bile acids in the digestive tract.
Answer
Bile acids, cholesterol derivatives, function as lipid emulsifying agents in the aqueous environment of the digestive tract. They help in the digestion of water-insoluble substances and are essential for the absorption of fats and fat-soluble vitamins. Bile acids are stored in the gallbladder and released into the small intestine during digestion.
22
Question
What are the two major classes of steroid hormones?
Answer
The two major classes of steroid hormones are sex hormones and adrenocorticoid hormones. Sex hormones include estrogens, androgens, and progestins. Adrenocorticoid hormones are produced by the adrenal glands and include mineralocorticoids and glucocorticoids.
23
Question
What are eicosanoids, and what are the three principal types of eicosanoids?
Answer
Eicosanoids are oxygenated C20 fatty acid derivatives that function as messenger lipids. The three principal types of eicosanoids are prostaglandins, thromboxanes, and leukotrienes.
24
Question
What is a biological wax, and where is it found?
Answer
A biological wax is a lipid that is a monoester of a long-chain fatty acid and a long-chain alcohol. It is found on the surface of fruits, leaves, and stems of plants where it helps prevent water loss and damage from pests. It is also found on the skin, fur, and feathers of animals, providing a waterproof coating.