Vitamins and Enzymes Overview

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Questions and Answers

What is the role of NAD+ primarily associated with?

Synthesis of carbohydrates

Biosynthesis of lipids

Catabolic reactions (correct)

Anabolic reactions

How is FAD reduced to FADH2?

By donating an electron and a proton

By taking up a proton and two electrons (correct)

By accepting two protons only

By undergoing hydrolysis

Which vitamin is a precursor for Thiamine Pyrophosphate (TPP)?

Vitamin C

Vitamin B1 (correct)

Vitamin B2

Vitamin B6

What type of reactions is Coenzyme A (CoA) primarily involved in?

Acyl-group transfer reactions Signup and view all the answers

What is a key characteristic of FAD and FMN as prosthetic groups?

They are tightly bound, usually noncovalently Signup and view all the answers

What is the primary function of NADPH in biological systems?

Reducing agent in biosynthetic reactions Signup and view all the answers

Which type of reaction is primarily catalyzed by enzymes utilizing Pyridoxal Phosphate (PLP)?

Amino acid rearrangements Signup and view all the answers

Which enzyme class is associated with the transfer of functional groups to water?

Hydrolases Signup and view all the answers

What is the general function of cofactors in enzymatic reactions?

To convert inactive apoenzymes to active holoenzymes Signup and view all the answers

Which of the following classes of enzymes involves the addition of groups to double bonds?

Lyases Signup and view all the answers

What is the best description of the reaction catalyzed by hexokinase?

Phosphorylation of glucose using ATP Signup and view all the answers

Which statement about enzymes is true?

They do not affect equilibrium concentrations of substrates and products. Signup and view all the answers

What is the role of absolute requirement for added metal ions in metal-activated enzymes?

They are essential for achieving full catalytic activity. Signup and view all the answers

What type of reaction does the enzyme class transferases primarily catalyze?

Group transfer reactions Signup and view all the answers

Which enzyme class includes enzymes that catalyze the formation of C-C, C-S, C-O, and C-N bonds?

Ligases Signup and view all the answers

Which metal ions are most commonly found in metalloenzymes?

Iron and zinc Signup and view all the answers

What is a characteristic feature of cosubstrates compared to prosthetic groups?

They are substrates in enzyme-catalyzed reactions. Signup and view all the answers

Why do animals, including humans, require external sources of coenzymes?

They lack the ability to synthesize certain coenzymes. Signup and view all the answers

What is the purpose of the recommended dietary allowance (RDA) for vitamins?

To define the amount of vitamins needed to prevent deficiency-related illnesses. Signup and view all the answers

Which of the following is NOT a recognized cause of nutritional-deficiency diseases?

An excess of dietary fiber Signup and view all the answers

Which vitamin can be synthesized endogenously from 7-dehydrocholesterol?

Vitamin D Signup and view all the answers

What units are used to measure vitamin concentration in the diet?

mcg (µg) and IU Signup and view all the answers

During which of the following conditions might a nutritional-deficiency disease occur?

Pregnancy and lactation periods Signup and view all the answers

Which type of organisms are the ultimate sources of vitamins for mammals?

Microorganisms and plants Signup and view all the answers

What can be considered a provitamin?

A compound that the body converts into a vitamin Signup and view all the answers

Which vitamin deficiency is primarily associated with neural tube defects in developing embryos?

Vitamin B9 Signup and view all the answers

What is the primary cofactor form of Vitamin B9 in the body?

Tetrahydrofolate Signup and view all the answers

Which of the following sources is NOT recommended for acquiring Vitamin B12?

Legumes Signup and view all the answers

What process facilitates the absorption of lipid vitamins in the intestine?

Interaction with bile salts Signup and view all the answers

What deficiency leads to pernicious anemia?

Vitamin B12 deficiency Signup and view all the answers

Which function is NOT associated with Vitamin C?

Coenzyme in fatty acid metabolism Signup and view all the answers

What is the Recommended Daily Allowance (RDA) for Vitamin B9?

400 µg Signup and view all the answers

What binds Vitamin B12 in the ileum for cellular uptake?

Intrinsic factor Signup and view all the answers

Which type of anemia results from Vitamin B9 deficiency?

Megaloblastic anemia Signup and view all the answers

What role does Vitamin C play in the body?

Facilitates collagen hydroxylation Signup and view all the answers

What is one of the advanced symptoms associated with the Wernicke-Korsakoff syndrome?

Mental convulsion Signup and view all the answers

Which vitamin's deficiency is characterized by Pellagra, known for its three 'D's?

Vitamin B3 Signup and view all the answers

Which dietary source is rich in Riboflavin (Vitamin B2)?

Eggs Signup and view all the answers

What is the recommended daily allowance of Vitamin B6 (Pyridoxine)?

1.3 mg Signup and view all the answers

Which cofactor is associated with Vitamin B5 (Pantothenic acid)?

Coenzyme A Signup and view all the answers

What are the symptoms of riboflavin deficiency in the context of hypothyroidism?

Inflammation of the mouth and tongue Signup and view all the answers

What is a significant effect of alcohol on the body's vitamin metabolism?

Inhibits vitamin intake and metabolism Signup and view all the answers

Which of the following is a dietary source of Vitamin B7 (Biotin)?

Natural products and synthesized by bacteria Signup and view all the answers

What is the primary role of TPP in the body?

Cofactor involved in neurotransmission Signup and view all the answers

Which condition is indicated by the 'necklace' lesions on the skin?

Pellagra due to niacin deficiency Signup and view all the answers

Study Notes

Vitamins and Cofactors

Vitamins are essential compounds that animals often obtain from plants or microorganisms
Mammals and carnivorous animals might obtain vitamins from eating meat
Some vitamins are provitamins, meaning they need to be activated in the body
Some vitamins can be synthesized endogenously
Recommended daily allowances (RDAs) for vitamins are determined by international health organizations and vary based on age and gender

Enzymes

Organisms need enzymes to efficiently and selectively catalyze chemical reactions.
Enzymes are central to all biochemical processes
Enzymes are highly specific for their substrates
Enzymes accelerate chemical reactions significantly
Enzymes typically function at mild temperature and pH in aqueous solutions
All enzymes are proteins, except for a small group of catalytic RNA molecules (ribozymes)
Their catalytic activity relies on their native protein conformation
Molecular weights of enzymes range from 12,000 to more than one million Daltons
Some enzymes only require amino acid residues for activity, while others need additional cofactors

Cofactors

Cofactors are inorganic ions (e.g., Fe²⁺, Mg²⁺, Mn²⁺, Zn²⁺), or complex organic/metalloorganic molecules (coenzymes)
Coenzymes act as transient carriers of functional groups
A tightly bound coenzyme or metal ion is called a prosthetic group
The complete, active enzyme with its cofactors is called a holoenzyme
The protein part of the enzyme without the cofactor is called an apoenzyme or apoprotein

Enzyme Classification

Enzymes are categorized based on the reactions they catalyze
Many enzymes are named by adding "-ase" to the substrate name or a descriptor of their activity
Examples include: Urease (hydrolysis of urea); DNA polymerase (polymerization of nucleotides to form DNA); Pepsin (digestion); Lysozyme (lyse bacterial walls)
Enzymes may have different names or there may be different enzymes with the same name.
Enzymes are grouped into classes. An international classification system exists.

Essential lons

More than 25% of known enzymes require metal ions for full activity
Some enzymes have an absolute requirement for specific metal ions while others are stimulated by added metal ions
Examples of essential ions for enzyme activity include Mg2+ and Ca2+ for many metabolic reactions and K+ for some enzymes

Metalloenzymes

Metalloenzymes contain firmly bound metal ions at active sites
Common metal ions include iron (Fe) and zinc (Zn), with less common use of copper (Cu) and cobalt (Co)
Examples include carbonic anhydrase (erythrocytes) that catalyzes CO₂ + H₂O → H⁺ + HCO₃⁻

Inorganic elements

Many inorganic elements serve as cofactors for enzymes.
Several examples include Cu²⁺, Fe²⁺/Fe³⁺, K⁺, Mg²⁺, Mn²⁺, Mo, Ni²⁺, Se, and Zn²⁺, each with specific enzyme functions

Coenzymes

Cosubstrates: temporarily bind and dissociate from the enzyme during the reaction.
Prosthetic groups: tightly bind to the enzyme and remain associated throughout the reaction.
Animals require a source of coenzymes or precursors to survive because they cannot synthesize all of them.
Prokaryotes, protists, fungi and plants are capable of synthesizing coenzymes from simple precursors. But animals (including humans) cannot.

Structure and Function of Vitamins

Vertebrates typically rely on other organisms for vitamin supply.
Most vitamin sources are plants or microorganisms even though carnivorous animals can obtain them from meat.
Some vitamins are provitamins, which need to be activated in the body. .
Some vitamins can be synthesized endogenously by the body. This is true for vitamin D from 7-dehydrocholesterol and vitamin K from intestinal flora

RDA for Vitamins

RDAs or DRIs are defined as the amount of a vitamin needed to protect the body against illness
They differ based on a person's age and gender.
Units for vitamin concentrations are mcg (μg) and International Unit (IU)

Nutritional deficiency Diseases (Avitaminoses)

A deficiency of a vitamin or absence of vitamins in an animal's diet can result in nutritional or vitamin deficiency diseases
Some examples of vitamin-deficiency diseases include scurvy (vitamin C deficiency); pellagra (niacin deficiency); growth retardation (riboflavin deficiency); dermatitis (pantothenate deficiency), beri beri (thiamine deficiency)

Vitamin Classification

Water-soluble vitamins are excreted in urine, do not cause hypervitaminosis, and are often heat sensitive (except B12).
Fat-soluble vitamins are absorbed with fats, are stored in the body (and an overdose can cause toxicity), and are not as sensitive to heat.

Specific Vitamins

Detailed information about individual vitamins (B1, B2, B3, B5, B6, biotin, B9, B12, vitamin C, A, D, E, K) including their sources, functions, cofactors, and deficiencies are presented in the provided text.

How Enzymes Work

Active site: The location where the enzyme-catalyzed reaction occurs
Substrate: The molecule acted upon in the active site
Enzymes reduce the activation energy of a reaction (but do not change the overall free energy change or the equilibrium concentrations).

Cofactor Requirements

Cofactors are often essential for converting inactive apoenzymes to active holoenzymes.

Nucleotide-sugar coenzymes

Provide detailed examples of nucleotide-sugar coenzymes, such as UDP-glucose, and their involvement in biosynthetic reactions, particularly glycogen synthesis.

Other coenzymes

Detailed information is presented in the provided text about various coenzymes like NAD+, NADP+, FAD, FMN, CoA, lipoamide, Ubiquinone (Coenzyme Q). This information includes sources, functions, and the reactions they are involved in

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Description

This quiz explores the vital role of vitamins and enzymes in biological processes. It covers the sources of vitamins, their activation, and how enzymes function as catalysts in biochemical reactions. Test your knowledge on these essential compounds and their significance in health and metabolic functions.