Biology · Chemistry

Lipids, Fats, and Biochemistry

1,130 Questions

Lipids, fats, and biochemistry explore the structure and function of biological molecules. This includes fatty acids, cholesterol, trans-fats, and cellular membranes. Questions on this topic frequently appear in science sections of competitive government exams.

Types of fats and lipidsCholesterol and human bodyFatty acidsCellular membranes

Lipids, Fats, and Biochemistry Questions

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Essential fatty acids occur in

  1. Animal fat

  2. Plant oils

  3. Fish and fowl

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Essential fatty acids are those fatty acids that body cannot produce on its own and therefore must be supplied from the diet. Two primary essential fatty acids are linoleic acid and alpha-linoleic acid. Linoleic acid (omega-6) occurs in plant oils like corn oil, palm oil, soybean oil, sunflower oil. Alpha-linoleic acid (omega-3) occurs in fowl and fish like salmon, sardines, tuna.

Thus, the correct answer is option D.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Content of unsaturated fatty acid linolenic acid is highest in

  1. Sunflower oil

  2. Cotton seed oil

  3. Groundnut oil

  4. Coconut oil
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Unsaturated fatty acid is those which contain one or more double bond in their fatty acids. Generally, it is found in plants fats. It also lowers blood cholesterol. Linoleic is unsaturated fatty acid containing two double bonds. Sunflower oil contains highest linoleic acid. Thus, the correct answer is A.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Unsaturated fatty acids have

  1. No double bonds

  2. High melting point

  3. One or more double bonds

  4. Disulphide bonds
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Fats or fatty acid which has at least one double bond in the chain is called as an unsaturated fatty acid. They are liquid at room temperature as they have double bonds. With the increase in the double bond, the intermolecular interaction gets weak and the melting point decreases.
So, the correct answer is option C.
Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Number of fatty acid residues present in one molecule of fat is

  1. $4$
  2. $3$
  3. $2$
  4. $1$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Fat is stored reserve for the body which provides energy. These are triesters of glycerol. It is obtained from fatty acids and glycerol. It consists of one glycerol molecule and three fatty acid molecules. The carboxyl end of the fatty acid combines with the three -OH groups of the glycerol to form the ester. So, the correct answer is option B.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

A fatty acid not synthesised in human body is

  1. Cholesterol

  2. Linoleic acid

  3. Glycerol

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Essential fatty acids are that fatty acids which play an important role in the biological process and they can be metabolized easily. These acts as a fuel rather getting deposited as fat in the body. The human body cannot synthesize essential fatty acids. Alpha-linolenic acid and linoleic acid are the two essential fatty acid. Unsaturated fats are liquid at room temperature as they have double bonds. Saturated fatty acids have the single bond and are solid at room temperature. 
So, the correct answer is option B.
Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

The most essential of the fatty acids is

  1. Arachidonic acid

  2. Palmitic acid

  3. Linoleic acid

  4. Oleic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fatty acids are of two types, the saturated fatty acids that have single bond across the carbon chain and the unsaturated fatty acids that have one or more double bond across the carbon chain. When there are more than one double bonds, they are called the polyunsaturated fatty acids. These are called the essential fatty acids as they cannot be synthesized in the body and must be supplied through the external source. Linoleic acid and linolenic acid are the essential fatty acids.

A. Arachidonic acid is also a polyunsaturated acid but it can be synthesized through the linoleic acid in the human body.
B. Palmitic acid is saturated fatty acid found in waxes and palm oil.
C. Linoleic is an essential fatty acid.
D. Oleic acid is saturated fatty acid found in vegetables and animal fats.
Hence, the correct answer is 'Linoleic acid'

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Which alcohol is present in fats?

  1. Glycerol

  2. Butanol

  3. Ethanol

  4. Octanol
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Butanol can be used as a biofuel. Molecular formula is C$ _4$H$ _{10}$O.
Ethanol is used for drinking. Molecular formula is C$ _2$H$ _6$O.
Octanol is used in perfumes and flavorings. The molecular formula is C$ _8$H$ _{18}$O.
Fat is stored reserve for the body which provides energy. These are triesters of glycerol. Glycerol has the chemical formula of  C$ _3$H$ _8$O$ _3$. It consists of one glycerol molecule and three fatty acid molecules. The carboxyl end of the fatty acid combines with the three -OH groups of the glycerol to form the ester. 
So, the correct answer is option A.
Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Unsaturated fatty acids have

  1. Palmitic acid

  2. Stearic acid

  3. Oleic acid

  4. One or more double bonds
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

An unsaturated fat is a fat or fatty acid in which there is one or more double bond in the fatty acid chain. A fat molecule is monounsaturated if it contains one double bond, and polyunsaturated if it contains more than one double bond. Where double bonds are formed, hydrogen atoms are eliminated.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

An essential fatty acid is

  1. Palmitic acid

  2. Arachidonic acid

  3. Stearic acid

  4. Arachidic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Arachidonic acid is not one of the essential fatty acids. Rather it is conditionally essential fatty acid which, becomes essential if its precursor, linoleic acid is deficient thereby resulting in the inability to convert linoleic acid to arachidonic acid. However, some mammals lack the ability or have a very limited capacity to convert linoleic acid to arachidonic acid, making it an essential part of their diets. So, the correct answer is 'Arachidonic acid'.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Higher animals cannot synthesise a few essential fatty acids; these are typically

  1. Saturated

  2. Branched

  3. Unsaturated

  4. Cyclic
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Unsaturated fats are liquid at room temperature as they have double bonds. Those unsaturated fatty acid which are not synthesized by the body are essential amino acid. Higher animals cannot synthesize a few essential fatty acids which are typically unsaturated because they lack desaturases that introduce double bonds beyond the ninth carbon atom. 
So, the correct answer is option C.
Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Higher animals cannot synthesize few fatty acids which are very essential for their growth and development. These fatty acids are typically

  1. Saturated

  2. Cyclic

  3. Unsaturated

  4. Branched
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Essential fatty acids are those which our body cannot synthesize but we need them for good health. Alpha-linolenic acid and linoleic acid are the two fatty acids which are essential for humans. These are long chain polyunsaturated fatty acids. Desaturase enzyme removes two hydrogen atoms from a fatty acid, creating a carbon-carbon double bond (unsaturation). Due to the absence of this enzyme in humans, they cannot synthesize the unsaturated essential fatty acids.
Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

An essential fatty acid is 

  1. Arachidonic acid

  2. Arachidic acid

  3. Palmitic acid

  4. Stearic acid.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Essential fatty acids are those compounds which cannot be synthesized by human and must be ingested externally. Examples of essential fatty acid include linoleic (omega-6 fatty acid) and alpha-linolenic acid (omega-3 fatty acid). Linoleic acid is converted to arachidonic acid. Arachidonic acid is an omega-6 unsaturated fatty acid required by proper functioning of body. 

Stearic acid, oleic acid, palmitic acid are nonessential fatty acids. They are synthesized by a human.
Thus, the correct answer is option A.

Multiple choice bio-chemistry biological molecule lipids and their function some biomolecules lipids

Number of fatty acid residues found in one molecule of fat is 

  1. 1

  2. 2

  3. 3

  4. 4
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fatty acids are long, straight chain carboxylic acids. A fat (or oil) is formed when three fatty acid molecules react with a glycerol molecule to yield a triglyceride. Fats in the body are transported and stored as triglycerides.

So, the correct answer is option C.