Biochemistry Lecture 8: Micronutrients

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Questions and Answers

What type of vitamins can lead to toxicity when consumed in excess?

Amino acids

Minerals

Lipid-soluble vitamins (correct)

Water-soluble vitamins

Which vitamin is primarily formed in the skin upon exposure to sunlight?

Vitamin D (correct)

Vitamin B12

Vitamin C

Vitamin A

What is the main function of B vitamins in the body?

Energy storage

Enzyme cofactors (correct)

Hormone production

Antioxidant activity

Which vitamin deficiency is associated with the disease beriberi?

Vitamin B1 (Thiamine) Signup and view all the answers

What type of compounds are lipid-soluble vitamins described as?

Hydrophobic Signup and view all the answers

What symptom is NOT characteristic of riboflavin (Vitamin B2) deficiency?

Anemia Signup and view all the answers

Which of the following is a source of preformed Vitamin A?

Foods of animal origin Signup and view all the answers

Which vitamin can be formed from the amino acid tryptophan?

Niacin Signup and view all the answers

What condition is primarily associated with vitamin D toxicity in adults?

Osteomalacia Signup and view all the answers

What is one of the three ways calcitriol increases calcium levels in the body?

Mobilizes bone minerals Signup and view all the answers

Which vitamin D precursor is converted to calcitriol through hydroxylation in the liver?

Ergocalciferol Signup and view all the answers

What happens to infants who consume vitamin D at very low doses?

They can develop elevated serum calcium levels Signup and view all the answers

What role does parathormone (PTH) play in calcium regulation?

Induces calcium mobilization from bones Signup and view all the answers

How does excessive exposure to sunlight affect the formation of vitamin D precursors?

Forms inactive compounds Signup and view all the answers

What is one consequence of elevated serum calcium related to vitamin D toxicity?

Hypertension Signup and view all the answers

What is the function of calcitonin in calcium regulation?

Inhibits bone resorption Signup and view all the answers

What is the role of retinoic acid in the body?

It regulates immune system cell differentiation. Signup and view all the answers

What occurs as a result of vitamin A deficiency?

Increased susceptibility to infectious diseases. Signup and view all the answers

Which process initiates a nerve impulse in photoreceptors?

Isomerization of 11-cis retinaldehyde to all-trans. Signup and view all the answers

What are some symptoms of vitamin A toxicity?

Liver issues and headache. Signup and view all the answers

What type of receptors does retinoic acid bind to?

Nuclear receptors that regulate DNA transcription. Signup and view all the answers

What is the significance of 11-cis-retinaldehyde in phototransduction?

It is involved in forming the holoprotein rhodopsin. Signup and view all the answers

In what way does vitamin D differ from retinoic acid?

Vitamin D does not bind to nuclear receptors. Signup and view all the answers

What is the consequence of unbound vitamin A in the body?

Potential for membrane lysis and tissue damage. Signup and view all the answers

Which compound is NOT a biologically active form of vitamin K?

Thiamine Signup and view all the answers

What is the role of thiamine diphosphate in metabolism?

Functions as a coenzyme for oxidative decarboxylation Signup and view all the answers

Which of the following factors is NOT part of the blood clotting system regulated by vitamin K?

Factor V Signup and view all the answers

Which vitamin is responsible for the synthesis of certain proteins in the blood clotting system?

Vitamin K Signup and view all the answers

What is a key feature of gamma-carboxyglutamate residues?

They chelate calcium ions. Signup and view all the answers

Which metabolic pathways are associated with thiamine in carbohydrate metabolism?

Pyruvate and alpha-ketoglutarate dehydrogenase processes Signup and view all the answers

Which vitamin is synthesized by intestinal bacteria?

Menaquinone Signup and view all the answers

What does thiamine specifically assist in regarding branched-chain keto acids?

Facilitates their oxidative decarboxylation Signup and view all the answers

What condition is primarily associated with vitamin D deficiency in young individuals?

Rickets Signup and view all the answers

What is the earliest sign of vitamin A deficiency?

Loss of sensitivity to green light Signup and view all the answers

Which vitamin is linked to the hemorrhagic disease of the newborn?

Vitamin K Signup and view all the answers

What is a potential consequence of vitamin A deficiency on vitamin D?

Impaired vitamin D function Signup and view all the answers

What function do Retinoid X Receptors (RXR) primarily serve?

Transcription regulation of fat-soluble vitamins Signup and view all the answers

How are the two isoenzymes of carotene dioxygenase differentiated?

By the cleavage method they utilize on beta carotene Signup and view all the answers

What vitamin deficiency can lead to hemolytic anemia in newborns?

Vitamin E Signup and view all the answers

What impairment occurs first due to vitamin A deficiency?

Inability to see in the dark Signup and view all the answers

Study Notes

Micronutrients: Vitamins Overview

Vitamins are essential organic compounds required in small amounts for metabolic integrity.
Water-soluble vitamins include B vitamins, C, Niacin, Folic Acid, Biotin, and Pantothenic Acid; they act primarily as enzyme cofactors.
Lipid-soluble vitamins comprise A, D, E, and K; toxicity can arise from excess intake.

Vitamin A (Retinol)

Retinol is important for vision, immune function, and cellular growth.
Deficiency leads to night blindness, impaired adaptation to darkness, and increased susceptibility to infectious diseases.
Sources include food of animal origin; carotenoids in plant sources can also be converted to retinoids via enzymatic processes.

Vitamin D

Synthesized in the skin from 7-dehydrocholesterol upon sunlight exposure.
Regulates calcium and phosphorus levels through calcitriol, increasing intestinal absorption and reducing excretion.
Deficiency results in Rickets in children and Osteomalacia in adults, characterized by softening of bones.

Vitamin E

Acts as an antioxidant and protects cell membranes.
Deficiency can cause hemolytic anemia in newborns due to oxidative stress.

Vitamin K

Exists as phylloquinone (plant source), menaquinone (bacteria), and synthetic forms.
Essential for synthesis of clotting factors in the blood including Factors II, VII, IX, and X.
Gamma-carboxyglutamate residues in clotting proteins allow for calcium ion binding, crucial for blood coagulation.

Thiamine (Vitamin B1)

Coenzyme for three multienzyme complexes involved in metabolic pathways such as carbohydrate metabolism.
Deficiency can lead to conditions like Beriberi, marked by neurological and cardiovascular issues.

Key Points on Toxicity

Excess vitamin A can cause neurological symptoms and liver toxicity.
High vitamin D intake may cause hypercalcemia, high blood pressure, and calcification of soft tissues, though sunlight exposure mitigates toxicity risks.
Balanced intake of vitamins is crucial for avoiding deficiency or toxicity-related disorders.

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Description

Explore the crucial role of vitamins as micronutrients in human metabolism. This quiz covers the types of vitamins, their sources, and the effects of vitamin toxicity. Understand the differences between lipid-soluble and water-soluble vitamins to enhance your biochemistry knowledge.

Biochemistry Lecture 8: Micronutrients - Vitamins

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