Y1S2 002 II Biochem of Hypoglycin-A: Amino Acids and Polypeptides

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Questions and Answers

What is the result of brain cells lacking glucose?

Coma (correct)

Malnutrition

Diabetes

Death due to vomiting

What is the scientific name of the amino acid found in the ackee?

Cyclopropyl acid

Hypoglycin-B

L-α-amino-β-methylene cyclopropyl propionic acid (correct)

Amino acid-A

What is the fate of the carbon skeletons of amino acids when used as fuel?

Formation of hormones

Oxidation to CO2 via TCA and conversion into glucose (correct)

Conversion into proteins

Storage in the liver

What is the purpose of digestion in the context of amino acid metabolism?

To break down proteins into absorbable units Signup and view all the answers

What is the term for each amino acid in a polypeptide chain?

Residue Signup and view all the answers

What is the role of amino acids in higher animals?

Serving as building blocks of proteins and as precursors of other biomolecules Signup and view all the answers

Where does the formation of citrulline occur?

Mitochondria Signup and view all the answers

What is the enzyme responsible for forming arginino succinate?

Arginino succinate synthetase Signup and view all the answers

What is the source of the second amino group required for urea synthesis?

Aspartate Signup and view all the answers

What is the byproduct of the reaction that forms arginino succinate?

AMP and PPi Signup and view all the answers

What is the purpose of pyrophosphatase in the formation of arginino succinate?

To hydrolyze PPi to inorganic phosphate Signup and view all the answers

What is the total number of ATP molecules consumed in the formation of arginino succinate?

3 Signup and view all the answers

What is the primary function of transamination during the oxidative degradation of amino acids?

To remove the amino group and convert it into a single excretory group Signup and view all the answers

What is the result of transamination on an α-amino acid?

Formation of an α-keto acid and release of ammonia Signup and view all the answers

What is the role of transaminases in transamination?

To enzymatically transfer the α-amino group from an amino acid to an α-keto acid Signup and view all the answers

What is the fate of the amino group removed during transamination?

It is converted into urea for excretion Signup and view all the answers

How many amino acids are involved in transamination during their oxidative degradation?

At least 20 Signup and view all the answers

What is the reactant that receives the α-amino group during transamination?

α-Ketoglutarate Signup and view all the answers

What is responsible for the colour change in the urine of individuals with Alcaptonuria?

Autooxidation of homogentisate Signup and view all the answers

Which disease is characterized by eye and skin lesions and sometimes mental retardation?

Neurotyrosinaemia Signup and view all the answers

What is the effect of lack of pigmentation in the eyes of individuals with Albinism?

Photophobia Signup and view all the answers

What is the deficiency responsible for Albinism?

Tyrosinase Signup and view all the answers

Which disease is related to Phenylalanine?

Parkinson's disease Signup and view all the answers

What is the effect of skin sensitivity to sunlight in individuals with Albinism?

Carcinoma Signup and view all the answers

What is the primary source of thyroid-stimulating hormone (TSH)?

Pituitary gland Signup and view all the answers

What is the result of iodination of tyrosyl residues in protein?

Formation of monoidotyrosine (MIT) Signup and view all the answers

Which of the following is a characteristic of thyrotoxicosis?

Tremor Signup and view all the answers

What is the fate of monoidotyrosine (MIT) in the synthesis of thyroid hormones?

It is converted to diiodotyrosine (DIT) and then to thyroxine (T4) Signup and view all the answers

What is the significance of a low iodine content in the thyroid gland?

It leads to an underactive thyroid gland Signup and view all the answers

What is the significance of a higher proportion of triiodothyronine (T3) to thyroxine (T4)?

It indicates an overactive thyroid gland Signup and view all the answers

Study Notes

Amino Acids and Glucose Metabolism

Brain cells are highly dependent on glucose; lack of glucose can lead to energy deficits and neuronal dysfunction.
The scientific name for the amino acid found in ackee is hypoglycin A, known for its toxic effects when consumed in unripe fruit.

Amino Acid Fuel and Metabolism

Carbon skeletons of amino acids, when used as fuel, are converted into intermediates that enter the citric acid cycle for energy production.
Digestion is essential in amino acid metabolism to break down proteins into amino acids for absorption and subsequent usage in various bodily functions.

Polypeptide Structure and Function

Each amino acid in a polypeptide chain is termed a residue, contributing to the protein's structure and function.
Amino acids serve various roles in higher animals, including serving as building blocks for proteins, precursors for hormones, and involvement in metabolic pathways.

Citrulline Formation and Urea Cycle

Formation of citrulline occurs in the mitochondria, a key step in the urea cycle to remove excess nitrogen from the body.
The enzyme responsible for forming argininosuccinate is argininosuccinate synthetase, crucial for the urea synthesis pathway.

Urea Synthesis and Byproducts

The second amino group required for urea synthesis is sourced from aspartate.
Byproduct of the reaction forming argininosuccinate is fumarate, which is utilized in the citric acid cycle.

Role of Enzymes in Urea Cycle

Pyrophosphatase catalyzes the hydrolysis of pyrophosphate, driving the formation of argininosuccinate forward.
A total of 2 ATP molecules are consumed in the formation of argininosuccinate, reflecting energy investment in urea synthesis.

Transamination Process

Primary function of transamination during oxidative degradation of amino acids is to convert non-essential amino acids to other amino acids, enabling energy production.
Transamination results in the conversion of an α-amino acid to a corresponding α-keto acid, facilitating amino acid interconversion.

Enzymatic Roles in Transamination

Transaminases are specialized enzymes that facilitate the transfer of amino groups between amino acids and α-keto acids.
The fate of the removed amino group during transamination is to be incorporated into another α-keto acid, forming a new amino acid.

Alcaptonuria is characterized by a urine color change due to the accumulation of homogentisic acid, a byproduct of tyrosine metabolism.
A disease characterized by eye and skin lesions, sometimes resulting in mental retardation, is associated with phenylketonuria (PKU).

Lack of pigmentation in the eyes of individuals with albinism leads to increased sensitivity to light and risk of vision problems.
Deficiency of the enzyme tyrosinase is responsible for albinism, affecting melanin production.

Thyroid Hormone Synthesis

The primary source of thyroid-stimulating hormone (TSH) is the anterior pituitary gland, regulating thyroid function.
Iodination of tyrosyl residues in proteins is necessary for the synthesis of thyroid hormones, impacting metabolic regulation.

Thyrotoxicosis and Iodine Significance

Thyrotoxicosis is characterized by hypermetabolism, weight loss, and increased heart rate, reflecting excessive thyroid hormone levels.
Fate of monoidotyrosine (MIT) during thyroid hormone synthesis involves conversion to diiodotyrosine (DIT) and further coupling to form T3 and T4.

Importance of Iodine Levels

Low iodine content in the thyroid gland can lead to goiter and hypothyroidism due to inadequate hormone synthesis.
A higher proportion of triiodothyronine (T3) to thyroxine (T4) is significant for metabolic activity, as T3 is more biologically active than T4.

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Description

This quiz covers the structural and functional aspects of Hypoglycin-A, a toxic compound found in ackee fruit, and its relation to amino acids, polypeptides, and enzymes. Learn about the effects of Hypoglycin-A on the body, including hypoglycemia and its consequences. Test your knowledge of biochemistry and molecular biology!