This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Keratin”.
1. What are passive type of protein?
a) Structural components
b) Proteins involved in biological function
c) Ribosomal protein
d) Non-functional protein
View Answer
Explanation: There are two types of proteins, passive and active. Passive components are the one which are involved in providing stability and strength to the cell. These constitute structural components of the cell. These components won’t have any particular biological function.
2. What are active type of proteins?
a) Ribosomal proteins
b) Non-functional protein
c) Structural components
d) Proteins involved in biological function
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Explanation: It is one of the two types of protein like passive and active. Active proteins are the one which are involved in biological function of the cell. These components will have specific function like synthesis or metabolism.
3. What is the common aspect between passive and active proteins?
a) Function
b) Structure
c) Secondary structure
d) Domains
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Explanation: Even though active and passive are two different types of proteins, they have one thing in common. That is there secondary structures. They have their secondary structures made of either alpha helices or beta sheets or both.
4. Choose the correct statement.
a) Domains of both active and passive proteins are same
b) Domains of both active and passive proteins are completely different
c) Domains of active and passive may or may not be same
d) Both active and passive proteins don’t have any domains
View Answer
Explanation: Even though both active and passive proteins are made of same secondary structures like alpha helices or beta sheets, they can have same or different domains depending on the chain of polypeptides. They can form different domains like alpha domains, beta domains, alpha/beta domains or alpha + beta domains out of same alpha helices and beta sheets.
5. The fibrous proteins will have specific repetitive sequences that are necessary for their ____________
a) 1D structure
b) 2D structure
c) 3D structure
d) 4D structure
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Explanation: The fibrous proteins will have a certain sequence of the amino acids repeating at several regions of a polypeptide chain. These repetitive sequence of amino acids makes the polypeptide chain to wind up with each other.
6. Fibrous proteins are divided into 3 groups depending on their secondary structures.
a) Primary structures
b) Secondary structures
c) Tertiary structures
d) Quaternary structures
View Answer
Explanation: The fibrous proteins are divided into three groups. This grouping is based on the types of secondary structures building the fibrous protein. Some fibrous proteins may contain only helices or some fibrous proteins may contain only pleats or some may contain both.
7. Which of the following is not a subgroup (type) of the fibrous proteins?
a) Coiled coil alpha helices
b) Coiled coil beta sheets
c) Triple helix
d) Beta sheets
View Answer
Explanation: The three types of fibrous proteins are coiled coil alpha helices, triple helix and beta sheets. There is no such structure called coiled coil beta sheets forming fibrous protein as beta sheets are rigid in nature and can not undergo complete coiling as alpha helices.
8. Which fibre can be extended to twice of their length?
a) Triple helix
b) Coiled coil alpha helices
c) Beta sheets
d) Coiled coil beta sheets
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Explanation: Coiled coil alpha helices are so flexible. They can be stretched twice their size when a certain pressure is applied on it. These types of proteins are elastic in nature. These can be brought to their original size by releasing the applied pressure.
9. Which of the following is not made up of keratin fibres?
a) Skin
b) Fingernails
c) Teeth
d) Hair
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Explanation: Keratin fibres are found in skin, hair and even in the feathers of the birds. These are coded by 60 genes of the human genome. These genes are of various differing sizes. They play an important role in forming a boundary which prevents the entry of foreign bodies into the host.
10. Which of the following does not found in keratins?
a) Globular domains
b) Gamma helical rod domains
c) Carboxyl end
d) Heptad repeats
View Answer
Explanation: Keratin fibres contain rod domains built up of of alpha helices rather than gamma helices. Since keratin is basically made up of amino acids, they should contain carboxyl and amino ends at the endings.
11. Which of the following is not a property of keratin?
a) Rigidity is greater than chitin
b) Protection from stress
c) Soluble
d) Bundles of monomers
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Explanation: Keratin is made up of bundles of keratin monomers. It is the key component in the formation of rigid materials like nails, claws and horns. So, their strength will be greater compared to the chitin. Hence you can easily predict the answer as solubility from the basic understanding that nails don’t dissolve in water.
12. Which of the following bonds can’t be seen in keratin?
a) Intermolecular H-bonds
b) Intramolecular H-bonds
c) Sulphur bonds
d) Calcium bonds
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Explanation: Keratin fibres are made of a sequence of amino acids. Hence there should be intermolecular as well as intramolecular hydrogen bonds. This helps to keep the side chains and the different amino acids together. Keratin contains a large number of sulphur containing amino acids such as cysteine. These form sulphur bridges between them making it more stable.
13. What is the reason for the pungent smell on burning of hair or skin?
a) High arginine
b) High cysteine
c) Less tyrosine
d) High tyrosine
View Answer
Explanation: The pungent smell usually indicates the presence of sulphur compounds in the surrounding atmosphere. The skin or hair is made up of keratin fibres. These keratin fibres has almost 13% to 20% of cysteine in it. When the skin or hair is burnt then the sulphur bridges of the cysteine breaks and resulting free sulphur forms its compounds with the atmospheric oxygen.
14. The keratin present in both humans and mammals/aves are same.
a) True
b) False
View Answer
Explanation: The fingernails or hair or skin of humans is softer and elastic in nature. While claws, horns of mammals/aves are harder and not so flexible in nature. This is because human skin/hair/nails are made up of alpha keratins whereas claws and horns are made up of beta-keratins. As the name suggests, alpha keratins are made by twisting the bundles of alpha helices. Whereas beta-keratin contains beta strands which get twisted to form beta-keratins.
15. Rapunzel syndrome is caused by keratins.
a) False
b) True
View Answer
Explanation: Keratins are highly insoluble and it can not be digested even by concentrated acids like HCl which is found in the stomach. Hence when the hair containing keratins is ingested it cannot be digested and gradually results in the formation of a hairball inside the stomach. This phenomenon can be seen in cats. In the case of humans, it causes serious complications.
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