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Important Enzymes and Macro Molecules of Life

Description: This test will help thestudents to revise their topics thoroughly.
Number of Questions: 15
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Tags: proteins Properties of Enzymes Enzymes Lipids Proteins
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Which among the following is a manganese containing enzyme which is also considered as ubiquitous to all domains of life?

  1. Nitrilase

  2. Adenosine deaminase

  3. Arginase

  4. Urease

  5. Metalloendopeptidase


Correct Option: C
Explanation:

Arginase is a manganese-containing enzyme. The reaction catalyzed by this enzyme is: arginine + H2O → ornithine + urea. It is the final enzyme of the urea cycle. It is ubiquitous to all domains of life.

The glycosylase released by the tips of the villi of the epithelium in the small intestine in humans is _________________.

  1. amylase

  2. sucrase

  3. chitinase

  4. β-galactosidase

  5. lactase


Correct Option: B
Explanation:

Sucrase is secreted by the tips of the villi of the epithelium in the small intestine. Its levels are reduced in response to villi-blunting events such as celiac sprue and the inflammation associated with the disorder. The levels increase in pregnancy/lactation and diabetes as the villi hypertrophy.

Which among the following enzymes plays a vital role in plasmid recombination and in DNA repair processes in prokaryotes?

  1. DnaB helicase

  2. RecQ helicase

  3. Transmembrane ATPases

  4. ATP synthase

  5. Kynureninase


Correct Option: B
Explanation:

In prokaryotes, RecQ is necessary for plasmid recombination and DNA repair from UV-light, free radicals and alkylating agents. This protein can also reverse damage from replication errors. In eukaryotes, replication does not proceed normally in the absence of RecQ proteins, which also function in aging, silencing, recombination and DNA repair.

Which among the following fatty acids integrates frequently into the phospholipid bilayer of mammalian cells?

  1. Oleic acid

  2. Punicic acid

  3. Nervonic acid

  4. Rumenic acid

  5. α-Parinaric acid


Correct Option: E
Explanation:

α-Parinaric acid occurs naturally in the seeds of the makita tree. Both the alpha and beta (all trans) isomers of parinaric acid are used as molecular probes of lipid-lipid interactions by monitoring phase transitions in bilayer lipid membranes. α-Parinaric acid was shown to integrate normally into the phospholipid bilayer of mammalian cells.

Which among the following statements does not characterise enzymes?

  1. Enzymes are regarded as the environmentally friendly solution to industrial problems.

  2. The arrangement of amino acids determines the enzyme's function.

  3. Enzymes neither live nor die.

  4. No two enzymes are alike.

  5. The two-dimensional structure of the enzyme determines the appearance of the active site.


Correct Option: E
Explanation:

The three-dimensional structure of the enzyme determines the appearance of the active site. The active site accommodates the shape of the biological substrate that requires transformation. They fit like a key in a lock. This is what makes enzymes specific in their actions. Only substances of the right shape will be transformed.

The protein involved in the transfer of oxygen from arterial blood to the brain is ______________________.

  1. chlorocruorin

  2. hemoglobin

  3. cytoglobin

  4. myoglobin

  5. neuroglobin


Correct Option: C
Explanation:

Cytoglobin is a globin molecule ubiquitously expressed in all tissues and most notably utilized in marine mammals. It is thought to protect against hypoxia. The function of cytoglobin is the transfer of oxygen from arterial blood to the brain.

Which of the following monosaccharides is an important constituent of the exoskeletons of crustaceans?

  1. Sulfoquinovose

  2. N-Acetylglucosamine

  3. Sialic acids

  4. Glucosamine

  5. Galactosamine


Correct Option: D
Explanation:

Glucosamine is an amino sugar and a prominent precursor in the biochemical synthesis of glycosylated proteins and lipids. Glucosamine is part of the structure of the polysaccharides chitosan and chitin, which compose the exoskeletons of crustaceans.

Which of the following lipid molecules is capable of activating new platelets as well as increasing platelet aggregation?

  1. Prostaglandins

  2. Leukotrienes

  3. Thromboxane A2

  4. Arachidonic acid

  5. Docosahexaenoic acid


Correct Option: C
Explanation:

Thromboxane A2 is a thromboxane. It is produced by activated platelets and has prothrombotic properties. It stimulates activation of new platelets as well as increases platelet aggregation.

Antioxidants protect the body cells from damage caused by free radicals. The lipids capable of functioning as an antioxidant and as a precursor of vitamin A in the human body are _______________.

  1. glycerolipids

  2. prenol lipids

  3. sterol lipids

  4. glycerophospholipids

  5. sphingolipids


Correct Option: B
Explanation:

Prenol lipids are synthesized from the five-carbon-unit precursors isopentenyl diphosphate and dimethylallyl diphosphate. Carotenoids are important simple isoprenoids that function as antioxidants and as precursors of vitamin A.

Which of the following is the protein governing the coordination of cell–cell adhesion and gene transcription in mammals?

  1. Alpha-catenin

  2. Beta-catenin

  3. Delta-2-catenin

  4. Gamma-catenin

  5. Gelsolin


Correct Option: B
Explanation:

It is a dual function protein, regulating the coordination of cell–cell adhesion and gene transcription. Mutations and overexpression of β-catenin are associated with many cancers, including hepatocellular carcinoma, colorectal carcinoma, lung cancer, malignant breast tumors, ovarian and endometrial cancer.

Which among the following proteins helps the human skin in regaining its original position after being poked or pinched?

  1. Actin

  2. Nuclear lamins

  3. Elastin

  4. Elaunin

  5. Spongin


Correct Option: C
Explanation:

Elastin is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting. Elastin helps skin to return to its original position when it is poked or pinched.

Bile acid synthesis occurs in liver cells. The enzyme participating in bile acid biosynthesis is _____________________.

  1. pancreatic lipase

  2. phospholipase D

  3. sterol esterase

  4. chymotrypsinogen

  5. trypsinogen


Correct Option: C
Explanation:

This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. This enzyme participates in bile acid biosynthesis.

The amino acid inhibiting the growth of hair and nails in the human body is _________________________.

  1. cysteine

  2. glycine

  3. glutamine

  4. cystine

  5. asparagines


Correct Option: A
Explanation:

It provides resistance to our body and inhibits the growth of hair, nails etc.

The enzymes being secreted in the human stomach are called gastric enzymes. Which among the following is secreted by the stomach to destroy the bacteria and viruses?

  1. Pepsin

  2. Intrinsic factor

  3. Mucin

  4. Gastrin

  5. Gastric lipase


Correct Option: C
Explanation:

The stomach has a priority to destroy the bacteria and viruses using its highly acidic environment but also has a duty to protect its own lining from its acid. The way that the stomach achieves this is by secreting mucin and bicarbonate via its mucous cells, and also by having a rapid cell turn-over.

The enzyme produced in the duodenum is known as a significant brush border. This enzyme is _________________.

  1. secretin

  2. cholecystokinin

  3. gastric inhibitory peptide

  4. motilin

  5. lactase


Correct Option: E
Explanation:

This is a significant brush border enzyme.This enzyme decreases with age, and as such lactose intolerance is often a common abdominal complaint in the older population, manifesting with bloating, abdominal pain and osmotic diarrhea.

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