Enzymes and Vitamins Quiz

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Questions and Answers

What is a primary function of coenzymes in the body?

To enhance the absorption of minerals

To synthesize proteins

To prepare the active site for catalytic activity (correct)

To store vitamins for later use

What is the primary cause of pernicious anemia?

Lack of iron in the diet

Insufficient vitamin C intake

Destruction of stomach cells that produce intrinsic factor (correct)

Excess levels of vitamin B12

Which vitamin is involved in the coenzyme thiamin pyrophosphate and is essential for decarboxylation processes?

Niacin

Cobalamin

Riboflavin

Thiamin (correct)

Which of the following is a consequence of vitamin C deficiency?

Weakened connective tissue and slow-healing wounds Signup and view all the answers

What symptoms may arise from a deficiency of niacin?

Dermatitis and muscle fatigue Signup and view all the answers

Which vitamin is necessary for the synthesis of coenzyme A and related to energy production?

Pantothenic Acid Signup and view all the answers

What is the role of folic acid in the body?

Required for the synthesis of nucleic acids Signup and view all the answers

What condition can occur as a result of pyridoxine deficiency?

Fatigue and dermatitis Signup and view all the answers

What is biotin primarily known for?

Acting as a co-enzyme in carboxylation reactions Signup and view all the answers

Cobalamin is essential for which of the following functions?

Transfer of methyl groups and red blood cell production Signup and view all the answers

Which of the following vitamins is classified as fat-soluble?

Vitamin D Signup and view all the answers

Which of the following vitamins is fat-soluble and can be stored in the body?

Cobalamin Signup and view all the answers

Which dietary source is particularly rich in biotin?

Whole hens egg Signup and view all the answers

Which condition can result from folic acid deficiency?

Megaloblastic anemia Signup and view all the answers

What common food sources provide pantothenic acid?

Salmon, meat, eggs, whole grains, and vegetables Signup and view all the answers

Which of the following vitamins is NOT fat-soluble?

Vitamin C Signup and view all the answers

What is the primary reason for the development of jaundice in the man described?

Impaired secretion of direct bilirubin Signup and view all the answers

What role does albumin play in the transport of bilirubin?

It transports indirect bilirubin to the liver Signup and view all the answers

What happens to the total bilirubin level in the blood during hepatitis?

It increases due to impaired bilirubin excretion Signup and view all the answers

How is bilirubin excreted from the body after its formation in the liver?

It is secreted into bile and some is excreted by the kidneys Signup and view all the answers

What effect does impaired secretion of water-soluble bilirubin have in hepatitis?

It leads to a build-up of bilirubin and darkened urine Signup and view all the answers

What is the primary function of Vitamin A in the human body?

Bone formation and vision Signup and view all the answers

Which dietary source is rich in Vitamin D?

Egg yolk Signup and view all the answers

What are the two forms of Vitamin K and their primary distinctions?

K1 has a saturated side chain, K2 has an unsaturated side chain Signup and view all the answers

Which vitamin plays a significant role as an antioxidant in the body?

Vitamin E Signup and view all the answers

In the case of a Vitamin D deficiency, which of the following symptoms is most likely?

Weakened bones Signup and view all the answers

What is the primary role of Vitamin K2 in the body?

Synthesis of zymogens for blood clotting Signup and view all the answers

What is one consequence of elevated levels of Alanine aminotransferase (ALT) observed in liver function tests?

Possible liver damage or disease Signup and view all the answers

How is Vitamin A primarily obtained from plant sources?

Through beta-carotene conversion Signup and view all the answers

What mechanism of inhibition does glucose-6-phosphate employ on hexokinase?

Allosteric interaction and competitive inhibition Signup and view all the answers

What is the primary consequence of glucose-6-phosphate accumulation within a cell?

Trapping of glucose, preventing its exit Signup and view all the answers

In which organ does the metabolic regulation involving hexokinase primarily take place?

Liver Signup and view all the answers

At what point is hexokinase activity prevented to avoid excessive glucose accumulation?

When glucose-6-phosphate concentration is adequate Signup and view all the answers

What role does hexokinase play in glucose metabolism?

Phosphorylation of glucose to form glucose-6-phosphate Signup and view all the answers

What is one of the primary fates of dietary glucose in the human body?

Oxidised to produce ATP Signup and view all the answers

What is the end product of glycolysis?

Pyruvate Signup and view all the answers

What specific role does hexokinase play in the reaction involving glucose?

It facilitates the phosphorylation of glucose. Signup and view all the answers

Under anaerobic conditions, what happens to pyruvate?

It is reduced to lactate Signup and view all the answers

Which component of ATP is directly attacked by the hydroxyl group of glucose in the reaction catalyzed by hexokinase?

The terminal phosphate group. Signup and view all the answers

Which of the following tissues primarily performs glucose catabolism to produce ATP?

Brain, muscle, and kidney Signup and view all the answers

How does Mg++ contribute to the process involving ATP and hexokinase?

It stabilizes the negative charges of phosphate groups. Signup and view all the answers

What role does NAD play in glycolysis?

It acts as an electron acceptor Signup and view all the answers

Where is glycogen primarily stored in the human body?

In liver and muscle Signup and view all the answers

What is the outcome of the reaction catalyzed by hexokinase?

Production of glucose-6-phosphate and ADP. Signup and view all the answers

Which statement about the active site of hexokinase is accurate?

It provides a favorable conformation for ATP to interact. Signup and view all the answers

Which metabolic pathway begins with the conversion of glucose into pyruvate?

Glycolysis Signup and view all the answers

In the metabolism of glucose, what is the role of lactate during intense exercise?

It is converted back to glucose Signup and view all the answers

During the reaction catalyzed by hexokinase, what happens to ADP?

It is released as a product. Signup and view all the answers

Which feature of ATP's structure is important for its role as an energy carrier?

The high-energy bonds between its phosphate groups. Signup and view all the answers

What type of chemical reaction is facilitated by hexokinase?

Phosphorylation reaction. Signup and view all the answers

Which molecule is essential for facilitating the interaction between hexokinase and ATP?

Mg++. Signup and view all the answers

In the hexokinase reaction, what functional role does the C6 hydroxyl group of glucose play?

It acts as a nucleophile that attacks ATP. Signup and view all the answers

Which compound is produced from the oxidation of pyruvate inside the mitochondria?

Acetyl CoA Signup and view all the answers

What is the primary role of the electron transport chain in aerobic metabolism?

Synthesis of ATP and re-oxidizing NADH Signup and view all the answers

What happens to lactate produced during glycolysis in heavily exercising muscle?

It can be converted back to pyruvate or glucose Signup and view all the answers

Which substance is produced as a result of the TCA cycle?

NADH Signup and view all the answers

What causes a reduction in intracellular pH during heavy exercise?

Accumulation of lactate Signup and view all the answers

During glycolysis, how does glucose initially enter the metabolic pathway?

By conversion to glucose-6-phosphate Signup and view all the answers

Which muscle fiber type predominantly utilizes the process described as the first mechanism of ATP synthesis?

Fast twitch muscle fibers Signup and view all the answers

What type of reaction occurs when pyruvate is converted to acetyl CoA?

Oxidation reaction Signup and view all the answers

What is the main byproduct of anaerobic metabolism of glucose during intense exercise?

Lactate Signup and view all the answers

Which biochemical pathway occurs in the cytosol of cells and initiates the breakdown of glucose?

Glycolysis Signup and view all the answers

How does glucose binding to hexokinase influence the enzyme's catalytic action?

It stabilizes a conformation that excludes water. Signup and view all the answers

What role does the C6 hydroxyl of bound glucose play in the activity of hexokinase?

It promotes catalysis by being close to the terminal phosphate of ATP. Signup and view all the answers

What would likely occur if water were allowed to enter the active site of hexokinase?

Hexokinase would hydrolyze glucose instead of phosphorylating it. Signup and view all the answers

Which statement best describes the induced fit mechanism in the context of hexokinase activity?

It stabilizes a transition state that enhances substrate conversion. Signup and view all the answers

What is the primary consequence of the induced fit during glucose binding to hexokinase?

It allows for a more effective phosphate transfer. Signup and view all the answers

What might be the effect of a mutation in hexokinase that alters the active site's shape?

Decreased efficiency in catalyzing phosphate transfer. Signup and view all the answers

Why is the exclusion of water from the active site critical for hexokinase function?

Water weakens enzyme-substrate interactions. Signup and view all the answers

Which functional group of glucose plays a significant role in the phosphorylation reaction catalyzed by hexokinase?

C6 hydroxyl group. Signup and view all the answers

What is the ultimate result of hexokinase's action on glucose in terms of metabolic pathways?

It creates a byproduct that is further metabolized in glycolysis. Signup and view all the answers

Study Notes

Vitamins and Coenzymes

Coenzymes prepare the active site for enzyme catalytic activity.
Water-soluble vitamins include B1, B2, B3, B5, B6, B12, C, and folate, which are not stored in the body and serve as cofactors for various enzymes.

Thiamin (Vitamin B1)

First B vitamin identified; crucial for the coenzyme thiamin pyrophosphate (TPP).
TPP is essential in decarboxylation of α-keto carboxylic acids.
Deficiency leads to beriberi, characterized by fatigue, weight loss, and nerve degeneration.

Riboflavin (Vitamin B2)

Composed of ribitol and flavin; part of coenzymes FAD and FMN.
Important for maintaining good vision and skin health.

Niacin (Vitamin B3)

Integral part of coenzyme NAD+; involved in oxidation-reduction reactions.
Deficiency can cause dermatitis, muscle fatigue, and appetite loss.
Found in meats, rice, and whole grains.

Pantothenic Acid (Vitamin B5)

Essential component of coenzyme A for energy production and synthesis of glucose and cholesterol.
Deficiency can lead to fatigue, cramps, and anemia.
Found in salmon, meat, eggs, whole grains, and vegetables.

Pyridoxine (Vitamin B6)

Exists in two forms, converted to coenzyme pyridoxal phosphate (PLP).
PLP is needed for amino acid transamination and carboxylic acid decarboxylation.
Deficiency may cause dermatitis, fatigue, and anemia.

Cobalamin (Vitamin B12)

Composed of four pyrrole rings with a Co2+ ion; coenzyme for methyl group transfers and red blood cell production.
Deficiency results in pernicious anemia and nerve damage, often due to loss of intrinsic factor from stomach cells.
Pernicious anemia leads to inadequate healthy red blood cells.

Ascorbic Acid (Vitamin C)

Necessary for collagen synthesis; deficiency causes weakened connective tissue, slow healing, and anemia (scurvy).
Found in blueberries, citrus fruits, tomatoes, and vegetables.

Folic Acid (Folate)

Contains pyrimidine, p-aminobenzoic acid, and glutamate; forms coenzyme THF for carbon group transfers and nucleic acid synthesis.
Deficiency may result in abnormal red blood cells, anemia, and hindered growth.

Biotin

Functions as a coenzyme in carboxylation reactions like pyruvate to oxaloacetate conversion.
Plays a role in carbohydrate and fat metabolism, protein synthesis, and the urea cycle, though the exact contributions are complex.
Rich sources include brewers yeast, liver, eggs, nuts, and green vegetables.

Fat-Soluble Vitamins

Comprise vitamins A, D, E, and K; soluble in lipids.
Important for vision, bone formation, antioxidants, and blood clotting; stored in the body.

Vitamin A

Obtained from animal liver and beta-carotenes from plants; liver converts beta-carotenes into retinol (vitamin A).

Vitamin D

Synthesized from skin exposure to sunlight; regulates calcium and phosphorus absorption during bone growth.
Deficiency causes weakened bones; sources include cod liver oil, egg yolk, and enriched milk.

Vitamin E

Acts as an antioxidant, preventing oxidation of unsaturated fatty acids.
Found in vegetable oils, whole grains, and green vegetables.

Vitamin K

Vitamin K1 (in plants) has a saturated side chain; vitamin K2 (in animals) features a long unsaturated side chain.
Vitamin K2 is vital for the synthesis of zymogens necessary for blood clotting.

Clinical Example: Hepatitis

A 36-year-old man presented with nausea, vomiting, and jaundice; liver function tests revealed elevated ALT and AST levels.
Diagnosis of hepatitis confirmed by symptoms and abnormal liver function tests.

Bilirubin

Produced from hemoglobin breakdown; insoluble in water, converted to water-soluble bilirubin diglucuronide in the liver for excretion.
Indirect bilirubin is transported to the liver, while direct bilirubin is excreted into bile and urine.
In hepatitis, the formation and secretion of direct bilirubin is impaired, leading to increased bilirubin levels and darkened urine, followed by jaundice.

Carbohydrate Metabolism Overview

Major dietary carbohydrate source is starch from plants, supplemented by animal glycogen, disaccharides (sucrose), and lactose.
Carbohydrates are digested into monosaccharides, primarily glucose, which is transported to the liver.
Glucose has three metabolic fates:
- Catabolized for ATP production
- Stored as glycogen in liver and muscle
- Converted to fatty acids and stored as triglycerides in adipose tissue.

Glycolysis

Glycolysis takes place in the cytosol, converting one glucose molecule (C6H12O6) into two pyruvate molecules (C3H3O3-).
This process yields a net production of two ATP molecules per glucose.
NAD+ is the electron acceptor used in oxidation reactions during glycolysis, which must be regenerated.

Anaerobic Glycolysis

In the absence of oxygen, pyruvate is reduced to lactate, facilitating ATP production in exercising muscle.
This lactate formation leads to a decrease in intracellular pH and can accumulate in muscles.
Lactate can be converted back to pyruvate for further oxidation or to glucose in the liver.

Aerobic Metabolism of Glucose

Pyruvate enters mitochondria and is oxidized to acetyl CoA using NAD+.
Acetyl CoA undergoes further oxidation in the citric acid cycle (TCA), ultimately producing CO2 and generating ATP via the electron transport chain.
Fast twitch muscle fibers primarily rely on anaerobic glycolysis, especially during high-intensity activities.

Hexokinase and Glycolysis Initiation

Hexokinase catalyzes the phosphorylation of glucose to glucose-6-phosphate using ATP.
This reaction relies on the nucleophilic attack of glucose's C6 hydroxyl group on ATP’s terminal phosphate.
Magnesium ions (Mg++) are crucial for stabilizing ATP and promoting a favorable reaction conformation.

Induced Fit Mechanism

The binding of glucose to hexokinase stabilizes a conformation that facilitates transfer of the phosphate group from ATP to glucose.
Water exclusion from the active site prevents hydrolysis of ATP, ensuring correct catalysis.

Regulation of Hexokinase

Hexokinase is inhibited by the product glucose-6-phosphate through competitive and allosteric mechanisms.
This product inhibition prevents excessive glucose accumulation when intracellular glucose-6-phosphate levels are sufficient, maintaining glucose homeostasis.

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Description

Test your knowledge on enzymes and vitamins, focusing on their functions and interactions. This quiz covers water-soluble vitamins and the role of coenzymes in enzymatic activity. Dive into the details of Thiamin and its importance in biochemical processes.