Why is glycerol soluble in water?
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Because the hydroxyl groups can interact with water.
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Why is glycerol soluble in water?
Because the hydroxyl groups can interact with water.
What does the formation of a milky emulsion indicate in the ethanol emulsion test?
The presence of lipid.
What is the structure of triglycerides?
Triglycerides consist of glycerol and three fatty acids.
What is a characteristic of a triglyceride molecule with unsaturated fatty acids?
It has a kinked tail.
What should be done after adding ethanol to the solid sample?
Shake thoroughly and allow the solid to settle for 3 minutes.
What protective function do triglycerides serve?
They act as a protective layer for delicate internal organs.
What observation indicates that lipids are present in the test?
A layer of cloudy white suspension forms at the top of the solution.
What is a good long-term energy store for hibernating animals?
Triglycerides.
What is the typical carbon atom range in fatty acids?
Usually 14 to 22 carbon atoms.
What effect does the carbon-carbon double bond have on the structure of unsaturated fatty acids?
It creates a 'kink' or rigid bend in the hydrocarbon tail.
Are lipids soluble in water?
No, lipids are insoluble in water but soluble in organic solvents.
What is a triglyceride composed of?
1 glycerol and 3 fatty acids joined via ester bonds.
What is the melting point of Lauric acid?
44.2 °C.
What role do triglycerides play in thermal insulation?
They prevent excessive heat loss, important for aquatic mammals.
What advantage do triglycerides provide for migratory birds?
They reduce the weight of the animals since less triglycerides need to be stored to provide the same amount of energy.
Why are trans fatty acids considered unhealthy?
They are worse for heart health than saturated fats.
How do the hydrocarbon tails of phospholipids affect membrane fluidity?
The composition of the tails (saturated, unsaturated, or a combination) affects the fluidity of the membrane.
What is the hydrophilic part of a fatty acid?
The carboxylic acid group (-COOH).
What elements make up lipids?
Carbon, hydrogen, and oxygen.
Why are steroids grouped under lipids?
Due to their insolubility in water.
What type of reaction occurs when forming a triglyceride?
A condensation reaction.
What is the primary storage form of energy in the body?
Triglycerides.
What bond is formed during the creation of triglycerides?
Ester bonds are formed between glycerol and fatty acids.
What are the two types of fatty acids?
Saturated and unsaturated fatty acids.
How are the fatty acid chains joined to the glycerol in phospholipids?
Through condensation reactions, forming two ester bonds and producing two water molecules.
What are phospholipids major components of?
The cell surface membrane and membranes of organelles.
What is the first step in testing solid food samples for lipids?
Crush the food sample and place it in a dry test tube.
What is the purpose of adding deionized water in the lipid test?
To observe the formation of an emulsion.
What are the components of a phospholipid molecule?
A glycerol, two fatty acids, and a phosphate group.
What is the importance of biochemical tests for lipids?
Biochemical tests help identify and quantify lipids in biological samples.
What is the hydrophobic part of a fatty acid?
The long hydrocarbon chain (fatty acid tail).
How are simple lipids formed?
By joining fatty acids to an alcohol (e.g., glycerol) through ester linkages.
What is the melting point of linolenic acid?
-11.0 °C.
What happens to the hydroxyl group of glycerol during triglyceride formation?
It reacts with the carboxylic group of a fatty acid, removing a water molecule.
Can the fatty acids in a triglyceride be the same or different?
Yes, they can be the same or different, affecting the triglyceride's properties.
What does a colorless solution indicate in the lipid test?
Lipids are not present.
What is the primary function of triglycerides?
Triglycerides serve as energy storage molecules.
How do lipids differ from carbohydrates in terms of oxygen content?
Lipids have a lower proportion of oxygen to hydrogen compared to carbohydrates.
What are examples of simple lipids?
Triglycerides and waxes.
What are examples of complex lipids?
Phospholipids and glycolipids.
How are hydrocarbon chains of fatty acids represented?
By zigzag lines with a double line for carbon to carbon double bonds.
Why are triglycerides insoluble in water?
They lack polar groups due to the condensation reactions.
How does the length of the hydrocarbon chain affect the melting point of fatty acids?
As the length of the hydrocarbon tail increases, the melting point of the fatty acids increases.
What is the significance of glycerol in lipids?
Glycerol serves as the backbone for triglycerides and phospholipids.
What types of small molecules can be linked to the phosphate group in phospholipids?
Usually charged or polar molecules.
What is one function of triglycerides other than being an energy source?
Source of metabolic water.
Why are triglycerides a better source of metabolic water compared to carbohydrates?
They contain about two times more hydrogen atoms than carbohydrates.
What is the melting point of Stearic acid?
69.6 °C.
What are the two main types of lipids?
Simple lipids (e.g., triglycerides) and complex lipids (e.g., phospholipids).
What is the procedure for testing liquid food samples for lipids?
Add a few drops of the liquid sample to a dry test tube, then add ethanol and deionized water, and shake thoroughly.
What are fatty acids composed of?
A long hydrocarbon chain and a carboxylic acid group (-COOH).
What is a key structural difference between saturated and unsaturated fatty acids?
Saturated fatty acids do not possess carbon-carbon double bonds, while unsaturated fatty acids do.
What are fats and where are they commonly found?
Fats are solid at room temperature and are commonly found in butter and cheese.
What are the four basic groups of lipids?
Triglycerides, phospholipids, steroids, and waxes.
What distinguishes different triglycerides?
The types of fatty acid chains they contain.
What is the role of phospholipids in living organisms?
Phospholipids are essential for forming cell membranes.
How much energy do triglycerides yield compared to carbohydrates?
Triglycerides yield about twice the quantity of energy (38 J g-1) compared to carbohydrates (17.2 KJ g-1).
What happens to cis bonds in unsaturated fatty acids when oil is reused for frying?
Some cis bonds convert to trans bonds, which are worse for heart health.
What is glycerol?
An alcohol with three hydroxyl groups that is soluble in water.
What structure do phospholipids form due to their amphipathic nature?
A bilayer.
What is the significance of the hydrophobic core formed by phospholipids?
It allows for compartmentalization of cell contents from the external environment.
How do variations in phospholipids affect cell membranes?
They affect the fluidity and permeability of the membrane.
Why is metabolic water important to desert animals?
It is produced from the oxidation of food.
Why are triglycerides insoluble in water?
They are large and uncharged, allowing them to be stored without affecting the water potential of cells.
Why do lipids produce more energy than carbohydrates?
Lipids are more reduced, containing more C-H bonds and fewer C-OH or C=O bonds, requiring more oxidation steps to fully oxidize.
What type of bonds do naturally occurring unsaturated fatty vegetable oils predominantly have?
Almost all cis bonds.
What does it mean that phospholipids are amphipathic?
They have both a hydrophobic region (hydrocarbon tails) and a hydrophilic region (phosphate heads).
How does the degree of saturation affect fatty acids?
It affects their melting points.
How does the number of carbon-carbon double bonds affect the melting point of fatty acids?
The greater the number of carbon-carbon double bonds, the lower the melting point of the fatty acids.
What is a sterol?
A steroid nucleus with a hydroxyl group, such as cholesterol and sex hormones.
How do carbon-carbon double bonds affect the melting point of fatty acids?
More double bonds create kinks in hydrocarbon tails, leading to weaker intermolecular interactions and a lower melting point.
How much ethanol should be added to the solid sample in the lipid test?
2 cm³ above the level of the sample.
What is the general formula for the hydrocarbon chain of fatty acids in triglycerides?
R = (CH2)n CH3.
How do triglycerides provide buoyancy to aquatic mammals?
They are less dense than water.
What type of bond is formed between the phosphate group and glycerol in phospholipids?
A phosphoester bond.
What is the major function of phospholipids in cells?
They are the major component of cell membranes.
How do saturated fatty acids maximize hydrogen attachment?
Each carbon in saturated fatty acids has the maximum number of hydrogen atoms attached.
What is the melting point of stearic acid?
69.6 °C.
What is the melting point of linoleic acid?
-5.0 °C.
What do the polar, hydrophilic heads of phospholipids do?
They point outwards and make contact with water molecules.
How do the properties of fatty acids differ?
They differ in their degree of saturation and the length of the hydrocarbon chain.
What is the melting point of oleic acid?
13.4 °C.
What characterizes steroids?
A carbon skeleton consisting of four fused rings.
What are lipids?
A diverse group of organic molecules that differ widely in size, structure, and functions, and are nonpolar and hydrophobic.
What are oils and where do they come from?
Oils are liquid at room temperature and can come from nuts, seeds, and fish.
What defines complex lipids?
They consist of a lipid and a non-lipid component.
