NEET MDS Shorts
57919
BiochemistryThe formation of oxyhemoglobin is influenced by 1. pH 2. CO2 concentration 3. Temperature
41719
BiochemistryVitamin C deficiency is due to defect of Lysyl hydroxylase
41057
BiochemistryGlycine and proline introduce a bend in structure of protein, hence alpha helix disrupted
31789
Biochemistry
Gout is a form of arthritis caused by the accumulation of uric acid crystals,
specifically sodium urate crystals, in the joints. The body produces uric acid
as a waste product during the metabolism of purines, which are substances found
in certain foods and also synthesized by the body. High levels of uric acid can
lead to the formation of these crystals, which cause inflammation and pain in
the affected joints. Urea (Answer 1) is a waste product formed from the
metabolism of proteins and amino acids, while guanine (Answer 3) and
hypoxanthine (Answer 4) are purine bases involved in nucleotide metabolism, but
they do not directly form the crystals seen in gout.
38738
BiochemistryGlutamate-pyruvate trans-aminase is predominantly present In Liver
17726
Biochemistry
The correct sulfur-containing amino acid among the options provided is:
1. Cystine
Explanation:
Amino acids are the building blocks of proteins, and they are characterized by
the presence of an amino group (-NH2) and a carboxyl group (-COOH). Some amino
acids also contain a side chain that is unique to each amino acid and determines
its chemical properties. Sulfur is an important element in the structure and
function of certain amino acids.
Cystine is a sulfur-containing amino acid, which is formed by the oxidation of
two cysteine molecules. Cysteine is the amino acid that contains a sulfur atom
in its side chain as a thiol group (-SH). When two cysteine residues are
adjacent in a polypeptide chain and the thiol groups react with each other, they
form a disulfide bond (-S-S-), resulting in the formation of cystine. This
disulfide bond is crucial for the tertiary structure of proteins, contributing
to their stability and function, particularly in the context of protein folding
and maintaining the integrity of protein domains.
The other options listed are not sulfur-containing amino acids:
2. Proline is an imino acid, meaning it contains an -NH group instead of an -NH2
group. Its side chain is a cyclic secondary amine and does not contain sulfur.
3. Arginine is a basic amino acid with a guanidino group in its side chain,
which is composed of nitrogen, carbon, and hydrogen atoms but no sulfur.
4. Isoleucine is a branched-chain amino acid, with a methyl group and an
isobutyl group on its side chain. It is a hydrophobic amino acid and does not
contain sulfur.
46890
Biochemistryâ-oxidation of fatty acid occursin Mitochondria
64826
BiochemistryProthrombin production in the liver is dependent upon Vitamin K intake
82700
Biochemistry
Anemia is a condition characterized by a decrease in the number of red blood
cells or a reduction in their oxygen-carrying capacity. Vitamin B12 and folic
acid are essential for the production of red blood cells. Deficiencies in these
vitamins can lead to megaloblastic anemia, where the bone marrow produces
abnormally large and immature red blood cells.
41039
Biochemistry
The rate limiting step in cholesterol synthesis is HMG CoA reductase. Here's
a detailed explanation:
Cholesterol synthesis is a complex process that involves multiple enzymatic
steps. This process begins with the condensation of acetyl-CoA molecules to form
acetoacetyl-CoA, which is then converted into HMG CoA
(3-hydroxy-3-methylglutaryl-CoA) by the enzyme HMG CoA synthetase. HMG CoA is
further converted to mevalonate by the action of HMG CoA reductase. This
reaction is the rate limiting step of the cholesterol synthesis pathway. The
rate limiting step is the slowest step in a metabolic pathway and is responsible
for controlling the overall rate of the process.
HMG CoA reductase is a critical regulatory enzyme that is tightly controlled
because it is the first committed step in the synthesis of cholesterol from
acetate. This enzyme is responsible for reducing HMG CoA to mevalonate, which is
the precursor of all isoprenoids, including cholesterol, steroids, and other
important biological molecules. The rate limiting nature of this step is due to
the fact that HMG CoA reductase is subject to both allosteric regulation and
feedback inhibition.
Allosteric regulation involves the binding of regulatory molecules, such as ATP,
citrate, and NADH, which can either activate or inhibit the enzyme. For example,
when cellular ATP levels are high, the enzyme is inhibited, which reduces
cholesterol synthesis. Conversely, when ATP levels are low, the enzyme is
activated, leading to increased cholesterol production. Citrate, a molecule
derived from the citric acid cycle, inhibits HMG CoA reductase when it builds up
in the cytosol, indicating that the cell has enough energy and does not need to
synthesize additional cholesterol.
Feedback inhibition occurs when the end product of the pathway, cholesterol,
binds to the enzyme and reduces its activity. This is a form of negative
feedback regulation that helps to maintain homeostasis of cholesterol levels
within the cell. When cellular cholesterol levels are high, the enzyme is
inhibited, which slows down the synthesis of new cholesterol molecules.
Conversely, when cholesterol levels are low, the enzyme is less inhibited, and
the synthesis rate increases.
The other enzymes listed, HMG CoA synthetase and mevalonate synthetase, are
involved in the synthesis of HMG CoA and the subsequent transformation of
mevalonate, but they are not the rate limiting steps. HMG CoA lyase, on the
other hand, is part of an alternative pathway that breaks down HMG CoA into
acetyl-CoA and acetoacetate. This enzyme is not directly involved in the rate
limiting step of cholesterol synthesis.