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Which substrate is released into the blood by exercising muscle and is involved in gluconeogenesis? A) Glycerol B) Lactate C) Glucose D) Fatty acids E) Ketone bodies
B) Lactate Explanation: Lactate is released into the blood by exercising muscle and plays a crucial role in gluconeogenesis, particularly in the context of the Cori Cycle, where it is converted back to glucose in the liver.
What is the primary function of glycogen synthesis? A) To break down glucose B) To store glucose for energy C) To convert fatty acids into glucose D) To produce insulin E) To synthesize proteins
B) To store glucose for energy Explanation: Glycogen synthesis primarily serves the function of storing glucose in the form of glycogen, which can be readily mobilized for energy when needed.
1/106
p.20
Gluconeogenesis: Pathway and Substrates

Which substrate is released into the blood by exercising muscle and is involved in gluconeogenesis?
A) Glycerol
B) Lactate
C) Glucose
D) Fatty acids
E) Ketone bodies

B) Lactate
Explanation: Lactate is released into the blood by exercising muscle and plays a crucial role in gluconeogenesis, particularly in the context of the Cori Cycle, where it is converted back to glucose in the liver.

p.10
Glycogenesis: Process and Enzymes

What is the primary function of glycogen synthesis?
A) To break down glucose
B) To store glucose for energy
C) To convert fatty acids into glucose
D) To produce insulin
E) To synthesize proteins

B) To store glucose for energy
Explanation: Glycogen synthesis primarily serves the function of storing glucose in the form of glycogen, which can be readily mobilized for energy when needed.

p.22
Glycogen Storage Disorders: Types and Symptoms

What are Glycogen Storage Disorders (GSD)?
A) Disorders caused by excess glucose in the blood
B) A group of inherited metabolic disorders due to enzyme deficiencies for glycogen synthesis or breakdown
C) Disorders related to fat metabolism
D) Conditions caused by vitamin deficiencies
E) Disorders affecting only the heart

B) A group of inherited metabolic disorders due to enzyme deficiencies for glycogen synthesis or breakdown
Explanation: GSDs are specifically defined as inherited metabolic disorders that arise from deficiencies in enzymes necessary for the synthesis or breakdown of glycogen in muscle or liver cells.

p.16
Glycogenesis: Process and Enzymes

What is the primary function of glycogen synthase?
A) To break down glycogen
B) To phosphorylate glucose
C) To synthesize glycogen
D) To regulate blood sugar levels
E) To convert glucose to pyruvate

C) To synthesize glycogen
Explanation: Glycogen synthase is primarily responsible for the synthesis of glycogen, converting glucose into glycogen for storage.

p.8
Glycogenesis: Process and Enzymes

How does glycogen synthase attach glucose to the glycogen chain?
A) By forming α-1,6 linkages
B) By forming α-1,4 linkages
C) By forming β-1,4 linkages
D) By forming β-1,6 linkages
E) By hydrolyzing glucose

B) By forming α-1,4 linkages
Explanation: Glycogen synthase creates α-1,4 linkages between UDP-Glucose and the non-reducing end of a glycogen chain, which is essential for glycogen elongation.

p.1
Hormonal Regulation: Insulin and Glucagon

What is the primary physiological switch in the body during fed and fasting states?
A) Cortisol
B) Insulin and glucagon
C) Thyroid hormones
D) Growth hormone
E) Estrogen

B) Insulin and glucagon
Explanation: The fed and fasting states are primarily mediated by insulin and glucagon, which play crucial roles in regulating energy storage and utilization in the body.

p.3
Hormonal Regulation: Insulin and Glucagon

Which hormone decreases during fasting?
A) Glucagon
B) Insulin
C) Adrenaline
D) Cortisol
E) Thyroxine

B) Insulin
Explanation: In the fasting state, insulin levels decrease, which helps facilitate the metabolic adaptations necessary for energy production from stored nutrients.

p.8
Glycogenesis: Process and Enzymes

What role does glycogenin play in glycogen synthesis?
A) It breaks down glycogen
B) It initiates glycogen chains
C) It transports glucose
D) It regulates insulin
E) It synthesizes fatty acids

B) It initiates glycogen chains
Explanation: Glycogenin is a protein that initiates glycogen synthesis by adding the first glucose molecule to a specific tyrosine residue, allowing glycogen synthase to elongate the chain afterward.

p.3
Energy Sources: Role of Glucose and Fatty Acids

What is the role of muscle during fasting?
A) It stores glucose for later use
B) It exports glucose to the bloodstream
C) It uses fatty acids and ketone bodies as fuel
D) It synthesizes triglycerides
E) It increases insulin sensitivity

C) It uses fatty acids and ketone bodies as fuel
Explanation: During fasting, muscle tissue utilizes fatty acids and ketone bodies for energy, while also undergoing proteolysis to supply amino acids for gluconeogenesis.

p.21
Cori Cycle: Lactate to Glucose Conversion

What process occurs after lactate is converted into pyruvate in the Cori cycle?
A) Glycolysis
B) Gluconeogenesis
C) Glycogenesis
D) Glycogenolysis
E) Fermentation

B) Gluconeogenesis
Explanation: After lactate is converted into pyruvate, it undergoes gluconeogenesis to produce glucose, which is a key step in the Cori cycle.

p.20
Gluconeogenesis: Pathway and Substrates

From where are amino acids sourced for gluconeogenesis?
A) Dietary carbohydrates
B) Tissue protein breakdown
C) Fatty acid oxidation
D) Blood glucose
E) Muscle glycogen

B) Tissue protein breakdown
Explanation: Amino acids used in gluconeogenesis are sourced from the breakdown of tissue proteins, providing essential building blocks for glucose synthesis, especially during periods of fasting or intense exercise.

p.16
Regulation of Glycogen Metabolism: Allosteric and Hormonal

Which enzyme is responsible for dephosphorylation in glycogen metabolism?
A) Protein Kinase A
B) Glycogen phosphorylase
C) Protein Phosphatase 1
D) Glycogen synthase
E) Protein Kinase B

C) Protein Phosphatase 1
Explanation: Protein Phosphatase 1 is responsible for dephosphorylation, which activates glycogen synthase and inhibits glycogen phosphorylase, thus promoting glycogen synthesis.

p.4
Energy Sources: Role of Glucose and Fatty Acids

What is the primary function of glycogen in the body?
A) To store fat
B) To provide a constant source of blood glucose
C) To produce hormones
D) To transport oxygen
E) To synthesize proteins

B) To provide a constant source of blood glucose
Explanation: Glycogen serves as a crucial energy reserve, providing a constant source of blood glucose necessary for life, especially for organs like the brain and cells without mitochondria.

p.3
Glycogenolysis: Mechanism and Regulation

What is the primary response of the liver during fasting?
A) Glycogenesis
B) Glycogenolysis
C) Lipogenesis
D) Protein synthesis
E) Glucose uptake

B) Glycogenolysis
Explanation: During fasting, the liver primarily responds through glycogenolysis, gluconeogenesis, β-oxidation, and ketogenesis to provide energy and maintain blood glucose levels.

p.22
Glycogen Storage Disorders: Types and Symptoms

Which of the following is NOT a symptom of Glycogen Storage Disorders?
A) Enlarged liver
B) Muscle fatigue
C) Cramps
D) Increased energy levels
E) Chronic hypoglycemia

D) Increased energy levels
Explanation: Increased energy levels are not a symptom of GSDs; rather, symptoms include enlarged liver, muscle fatigue, cramps, and chronic hypoglycemia due to metabolic dysfunction.

p.10
Hormonal Regulation: Insulin and Glucagon

What role does insulin play in glycogen synthesis?
A) It inhibits glycogen synthesis
B) It has no effect on glycogen synthesis
C) It promotes glycogen synthesis
D) It converts glycogen to glucose
E) It activates glycogen phosphorylase

C) It promotes glycogen synthesis
Explanation: Insulin plays a crucial role in promoting glycogen synthesis by facilitating the uptake of glucose into cells and activating glycogen synthase.

p.2
Physiological States: Fed and Fasting

What are the plasma levels like during the fed state?
A) Low plasma glucose and high plasma triglycerides
B) High plasma glucose, amino acids, and triglycerides
C) Low plasma amino acids and triglycerides
D) High plasma glucose and low plasma amino acids
E) Low plasma glucose and high plasma amino acids

B) High plasma glucose, amino acids, and triglycerides
Explanation: During the fed state, there are high levels of plasma glucose, amino acids, and triglycerides, indicating an abundance of nutrients available for metabolism.

p.2
Hormonal Regulation: Insulin and Glucagon

What happens to insulin and glucagon levels during the fed state?
A) Insulin decreases and glucagon increases
B) Both insulin and glucagon increase
C) Insulin increases and glucagon decreases
D) Both insulin and glucagon decrease
E) Insulin remains constant while glucagon decreases

C) Insulin increases and glucagon decreases
Explanation: In the fed state, insulin levels increase to facilitate the uptake of nutrients, while glucagon levels decrease, reflecting the body's shift towards storing energy.

p.4
Energy Sources: Role of Glucose and Fatty Acids

Which organ greatly prefers glucose as its energy source?
A) Liver
B) Muscle
C) Brain
D) Kidney
E) Skin

C) Brain
Explanation: The brain has a high preference for glucose as its primary energy source, highlighting the importance of glycogen in maintaining adequate glucose levels for brain function.

p.14
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What is the role of Glycogen Phosphorylase in glycogen metabolism?
A) It synthesizes glycogen
B) It degrades glycogen
C) It regulates glucose uptake
D) It converts glucose to pyruvate
E) It inhibits glycogen synthesis

B) It degrades glycogen
Explanation: Glycogen Phosphorylase is the enzyme responsible for the degradation of glycogen, facilitating the release of glucose when energy is needed by the cell.

p.1
Physiological States: Fed and Fasting

Which of the following statements is true regarding the fed state?
A) Glucagon levels are high
B) Insulin promotes the breakdown of stores
C) Nutrients are plentiful
D) The body enters a fasting state
E) Adrenaline levels are low

C) Nutrients are plentiful
Explanation: In the fed state, nutrients are abundant, leading to increased insulin levels that promote the storage of energy rather than its breakdown.

p.23
Glycogen Storage Disorders: Types and Symptoms

What is the incidence rate of GSD I?
A) 1/50,000 live births
B) 1/75,000 live births
C) 1/100,000 live births
D) 1/150,000 live births
E) 1/200,000 live births

C) 1/100,000 live births
Explanation: The incidence of GSD I is approximately 1 in 100,000 live births, indicating its rarity in the general population.

p.13
Glycogen Metabolism: Synthesis and Degradation

What is the primary function of phosphoglucomutase?
A) To synthesize glycogen
B) To convert glucose to glucose-6-phosphate
C) To convert glucose-6-phosphate to glucose-1-phosphate
D) To degrade glycogen
E) To transport glucose across membranes

C) To convert glucose-6-phosphate to glucose-1-phosphate
Explanation: Phosphoglucomutase is an enzyme that catalyzes the conversion of glucose-6-phosphate (G6P) to glucose-1-phosphate, playing a crucial role in glycogen metabolism.

p.11
Glycogenolysis: Mechanism and Regulation

How many separate domains does the debranching enzyme have for its activities?
A) One
B) Two
C) Three
D) Four
E) Five

B) Two
Explanation: The debranching enzyme has two separate domains, each responsible for different activities: one for transferring glucose residues and another for releasing free glucose from the α-(1,6) bond.

p.19
Gluconeogenesis: Pathway and Substrates

What is the energy requirement for gluconeogenesis compared to glycolysis?
A) Requires more energy than glycolysis
B) Requires the same amount of energy as glycolysis
C) Requires less energy than glycolysis
D) Does not require energy
E) Requires energy only in the presence of oxygen

A) Requires more energy than glycolysis
Explanation: Gluconeogenesis requires more energy than glycolysis, as it involves the conversion of pyruvate back to glucose, which consumes ATP and GTP.

p.6
Glycogen Metabolism: Synthesis and Degradation

What does the term 'glycogen flux' refer to?
A) The static nature of glycogen
B) The dynamic resource of glycogen
C) The breakdown of glucose
D) The synthesis of fatty acids
E) The storage of proteins

B) The dynamic resource of glycogen
Explanation: Glycogen flux indicates that glycogen is not a static storage form but a dynamic resource that can be synthesized and degraded as needed by the body, reflecting its role in energy metabolism.

p.16
Hormonal Regulation: Insulin and Glucagon

What is the role of protein kinases in glycogen metabolism?
A) They promote glycogen synthesis through dephosphorylation
B) They inhibit glycogen breakdown through phosphorylation
C) They promote glycogen breakdown through phosphorylation
D) They have no effect on glycogen metabolism
E) They convert glycogen synthase to its inactive form

C) They promote glycogen breakdown through phosphorylation
Explanation: Protein kinases are responsible for the phosphorylation of enzymes, which activates glycogen phosphorylase, promoting glycogen breakdown.

p.16
Glycogenolysis: Mechanism and Regulation

What is the inactive form of glycogen phosphorylase called?
A) Active 'a' form
B) Inactive 'b' form
C) Phosphorylated form
D) Dephosphorylated form
E) Glycogen synthase

B) Inactive 'b' form
Explanation: Glycogen phosphorylase exists in an inactive 'b' form, which is converted to the active 'a' form through phosphorylation.

p.1
Physiological States: Fed and Fasting

What occurs in the body when nutrients are limited?
A) The body increases nutrient absorption
B) The body builds up stores
C) The body uses stores to maintain functions
D) The body enters a fed state
E) The body decreases metabolic rate

C) The body uses stores to maintain functions
Explanation: In a state of limited nutrients, the body utilizes its stored energy to maintain essential functions, primarily regulated by glucagon and adrenaline.

p.1
Hormonal Regulation: Insulin and Glucagon

Which hormone is NOT primarily involved in the physiological switch between fed and fasting states?
A) Insulin
B) Glucagon
C) Adrenaline
D) Cortisol
E) All of the above are involved

D) Cortisol
Explanation: While cortisol plays a role in metabolism, it is not one of the primary hormones mediating the physiological switch between fed and fasting states, which mainly involves insulin and glucagon.

p.18
Gluconeogenesis: Pathway and Substrates

Which tissues specifically require glucose for their function?
A) Liver and pancreas
B) Muscle and skin
C) RBC, brain, testes, lens of eye
D) Heart and lungs
E) Stomach and intestines

C) RBC, brain, testes, lens of eye
Explanation: Certain tissues, including red blood cells (RBC), the brain, testes, and the lens of the eye, have a specific requirement for glucose, highlighting the importance of gluconeogenesis in maintaining glucose levels for these critical functions.

p.7
Glycogenesis: Process and Enzymes

What is synthesized from UDP and glucose during glycogenesis?
A) Glucose-6-P
B) Glycogen
C) Glucose-1-P
D) Fructose-1,6-bisphosphate
E) Pyruvate

B) Glycogen
Explanation: UDP-glucose is synthesized by UDP-glucose pyrophosphorylase and is then used as a substrate by glycogen synthase to form glycogen.

p.3
Gluconeogenesis: Pathway and Substrates

Which fuel sources does the brain utilize during fasting?
A) Only glucose
B) Only fatty acids
C) Glucose and ketone bodies
D) Triglycerides and amino acids
E) Glycogen and lactate

C) Glucose and ketone bodies
Explanation: The brain primarily uses glucose for energy during fasting, and later on, it can utilize ketone bodies as an alternative fuel source.

p.4
Glycogen Metabolism: Synthesis and Degradation

What is the approximate amount of glycogen stored in the liver?
A) 50g
B) 100g
C) 200g
D) 300g
E) 400g

B) 100g
Explanation: The liver stores approximately 100g of glycogen, which is crucial for maintaining blood glucose levels, especially during fasting or low dietary intake.

p.9
Glycogenesis: Process and Enzymes

What type of bond does the branching enzyme break to create branches in glycogen?
A) α-1,6 bond
B) β-1,4 bond
C) α-1,4 bond
D) β-1,6 bond
E) α-1,2 bond

C) α-1,4 bond
Explanation: The branching enzyme breaks the α-1,4 bond to release a chain of glucose residues, which are then reattached via an α-1,6 bond, facilitating the branching of glycogen.

p.7
Glycogenesis: Process and Enzymes

Where does glycogenesis occur in the cell?
A) Nucleus
B) Mitochondria
C) Cytosol
D) Endoplasmic reticulum
E) Golgi apparatus

C) Cytosol
Explanation: Glycogenesis occurs in the cytosol of the cell, which is the fluid component where various metabolic processes take place.

p.1
Physiological States: Fed and Fasting

What happens in the body when nutrients are plentiful?
A) The body uses stores to maintain functions
B) The body builds up stores
C) The body enters a fasting state
D) The body decreases insulin production
E) The body increases glucagon levels

B) The body builds up stores
Explanation: When nutrients are plentiful, the body focuses on building up energy stores, primarily facilitated by insulin, which promotes the storage of glucose and fats.

p.23
Glycogen Storage Disorders: Types and Symptoms

What is the deficiency associated with GSD I (Von Gierke's Disease)?
A) Glucose-6-phosphate dehydrogenase deficiency
B) Glucose-6-phosphatase deficiency
C) Glycogen synthase deficiency
D) Phosphorylase deficiency
E) Glucose-1-phosphate deficiency

B) Glucose-6-phosphatase deficiency
Explanation: GSD I, also known as Von Gierke's Disease, is primarily caused by a deficiency in glucose-6-phosphatase, which is crucial for glycogen metabolism.

p.23
Glycogen Storage Disorders: Types and Symptoms

What is a common symptom of GSD I?
A) Hyperglycemia
B) Hypoglycemia
C) Hypertension
D) Hyperlipidemia
E) Hyperkalemia

B) Hypoglycemia
Explanation: Hypoglycemia is a common symptom of GSD I, along with lactic acidosis and ketosis, due to the impaired ability to release glucose from glycogen stores.

p.10
Glycogenesis: Process and Enzymes

Which molecule is formed as a result of glycogen synthesis?
A) Glucose
B) UDP-glucose
C) Fructose-1,6-bisphosphate
D) Pyruvate
E) Acetyl-CoA

B) UDP-glucose
Explanation: During glycogen synthesis, glucose is activated by being converted into UDP-glucose, which is then used to elongate the glycogen molecule.

p.18
Gluconeogenesis: Pathway and Substrates

How long can glycogen stores typically last?
A) 1-2 hours
B) 10-18 hours
C) 24-36 hours
D) 48-72 hours
E) 5-7 days

B) 10-18 hours
Explanation: Glycogen stores in the body can last approximately 10 to 18 hours, after which gluconeogenesis becomes essential for glucose production from other precursors.

p.21
Cori Cycle: Lactate to Glucose Conversion

What happens to the glucose produced in the Cori cycle?
A) It is stored as glycogen in the liver
B) It is converted back to lactate
C) It is exported into the blood and taken up by the muscles
D) It is excreted from the body
E) It is used to produce ATP in the liver

C) It is exported into the blood and taken up by the muscles
Explanation: The final step of the Cori cycle involves the export of glucose into the bloodstream, where it can be taken up by muscle cells for energy.

p.18
Gluconeogenesis: Pathway and Substrates

How can gluconeogenesis be conceptualized in relation to glycolysis?
A) As a completely different pathway
B) As a reversal of glycolysis
C) As a faster process than glycolysis
D) As a process that only occurs in the liver
E) As a pathway that does not share any enzymes with glycolysis

B) As a reversal of glycolysis
Explanation: Gluconeogenesis can be conceptualized as a reversal of glycolysis, sharing several enzymes, although it also involves unique steps to bypass the irreversible reactions of glycolysis.

p.2
Glycogen Metabolism: Synthesis and Degradation

What is the primary response of the liver during the fed state?
A) Breaks down glycogen
B) Makes glycogen, triglycerides, and protein
C) Converts triglycerides to glucose
D) Increases gluconeogenesis
E) Releases glucose into the bloodstream

B) Makes glycogen, triglycerides, and protein
Explanation: The liver responds to the fed state by synthesizing glycogen, triglycerides, and proteins, utilizing the available nutrients for storage and metabolism.

p.8
Glycogenesis: Process and Enzymes

What is the primary enzyme responsible for elongating glycogen chains?
A) Glycogen phosphorylase
B) Glycogen synthase
C) Glycogenin
D) Hexokinase
E) Phosphofructokinase

B) Glycogen synthase
Explanation: Glycogen synthase is the enzyme that makes α-1,4 linkages between UDP-Glucose and the non-reducing end of a glycogen chain, facilitating the elongation of glycogen.

p.21
Cori Cycle: Lactate to Glucose Conversion

What is the first step of the Cori cycle?
A) Glucose is exported into the blood
B) Lactate is transported to the liver through the blood
C) Pyruvate is converted into lactate
D) Lactate is processed into glucose
E) Lactate is produced by muscle cells

B) Lactate is transported to the liver through the blood
Explanation: The first step of the Cori cycle involves the transport of lactate from muscle cells to the liver via the bloodstream, initiating the cycle.

p.14
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What types of regulation are involved in glycogen metabolism?
A) Only allosteric regulation
B) Only hormonal regulation
C) Both allosteric and hormonal regulation
D) Genetic regulation only
E) Environmental regulation only

C) Both allosteric and hormonal regulation
Explanation: Glycogen metabolism is regulated through both allosteric and hormonal mechanisms, allowing the cell to respond effectively to changes in energy requirements.

p.18
Gluconeogenesis: Pathway and Substrates

What is the primary purpose of gluconeogenesis?
A) To store excess glucose as glycogen
B) To convert fatty acids into glucose
C) To form glucose from other precursors when glycogen is depleted
D) To break down glucose for energy
E) To synthesize amino acids

C) To form glucose from other precursors when glycogen is depleted
Explanation: The main purpose of gluconeogenesis is to synthesize glucose from non-carbohydrate precursors when glycogen stores are depleted, ensuring a continuous supply of glucose for vital tissues.

p.9
Glycogenesis: Process and Enzymes

What happens to the number of non-reducing ends in glycogen after branching occurs?
A) It decreases
B) It remains the same
C) It doubles
D) It triples
E) It increases by one

C) It doubles
Explanation: After branching occurs, the number of non-reducing ends available for glycogen synthase increases, effectively doubling the number of non-reducing ends, which enhances the efficiency of glycogen synthesis.

p.2
Energy Sources: Role of Glucose and Fatty Acids

How do adipose tissues respond during the fed state?
A) They break down triglycerides
B) They make glucose
C) They make triglycerides
D) They release fatty acids
E) They increase protein synthesis

C) They make triglycerides
Explanation: Adipose tissues respond to the fed state by synthesizing triglycerides, storing excess energy from the nutrients available in the bloodstream.

p.19
Gluconeogenesis: Pathway and Substrates

Which enzyme is involved in the final step of gluconeogenesis, converting glucose-6-phosphate to glucose?
A) Pyruvate kinase
B) Fructose-1,6-bisphosphatase
C) Glucose-6-phosphatase
D) Hexokinase
E) Phosphofructokinase

C) Glucose-6-phosphatase
Explanation: Glucose-6-phosphatase is responsible for converting glucose-6-phosphate to free glucose, completing the gluconeogenesis pathway.

p.14
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What happens to glycogen metabolism during the fed state?
A) Increased degradation and decreased synthesis
B) Decreased degradation and increased synthesis
C) No change in synthesis or degradation
D) Increased synthesis and increased degradation
E) Decreased synthesis and decreased degradation

B) Decreased degradation and increased synthesis
Explanation: In the fed state, glycogen metabolism is characterized by increased synthesis and decreased degradation, as the energy requirements of the cell dictate the storage of glucose as glycogen.

p.7
Glycogenesis: Process and Enzymes

Which two molecules are required for the synthesis of glycogen?
A) NADH and FADH2
B) ATP and UTP
C) ADP and GDP
D) AMP and cAMP
E) GTP and NADPH

B) ATP and UTP
Explanation: Glycogenesis requires both ATP and uridine triphosphate (UTP) as energy sources for the synthesis of glycogen.

p.10
Glycogenesis: Process and Enzymes

Which enzyme is primarily responsible for the synthesis of glycogen?
A) Glycogen phosphorylase
B) Glycogen synthase
C) Hexokinase
D) Phosphofructokinase
E) Glucose-6-phosphatase

B) Glycogen synthase
Explanation: Glycogen synthase is the key enzyme involved in the synthesis of glycogen, facilitating the addition of glucose units to the growing glycogen chain.

p.10
Glycogenesis: Process and Enzymes

What is the initial substrate for glycogen synthesis?
A) Fructose
B) Glucose-6-phosphate
C) Lactate
D) Pyruvate
E) Acetyl-CoA

B) Glucose-6-phosphate
Explanation: Glycogen synthesis begins with glucose-6-phosphate, which is converted into UDP-glucose before being added to the glycogen chain.

p.17
Hormonal Regulation: Insulin and Glucagon

What triggers the secretion of glucagon from the pancreas?
A) High blood sugar levels
B) Low blood sugar levels
C) Exercise
D) Stress
E) High insulin levels

B) Low blood sugar levels
Explanation: Glucagon is secreted from the pancreas when blood sugar levels are low, particularly during fasting states, to help increase glucose availability in the body.

p.4
Energy Sources: Role of Glucose and Fatty Acids

Why is dietary intake of glucose considered unreliable?
A) It is always too high
B) It is often too low
C) It varies greatly
D) It is only available in certain seasons
E) It is not needed by the body

C) It varies greatly
Explanation: The dietary intake of glucose can be inconsistent, making it essential for the body to store glucose in the form of glycogen for reliable energy supply.

p.8
Glycogenesis: Process and Enzymes

What happens to UDP during the synthesis of glycogen?
A) It is converted to ATP
B) It is released
C) It is reused immediately
D) It is hydrolyzed
E) It is phosphorylated

B) It is released
Explanation: During the synthesis of glycogen, UDP is released when glycogen synthase forms linkages between glucose molecules, indicating that it is a byproduct of the reaction.

p.8
Glycogenesis: Process and Enzymes

Which end of the glycogen chain does glycogen synthase elongate?
A) Reducing end
B) Non-reducing end
C) Both ends
D) Neither end
E) Only the middle

B) Non-reducing end
Explanation: Glycogen synthase elongates the glycogen chain by adding glucose to the non-reducing end, which is crucial for the proper structure and function of glycogen.

p.13
Glycogenolysis: Mechanism and Regulation

What is the role of glucose-6-phosphatase?
A) To convert glucose to glucose-6-phosphate
B) To convert glucose-6-phosphate to glucose
C) To synthesize glycogen
D) To transport glucose into cells
E) To degrade glycogen

B) To convert glucose-6-phosphate to glucose
Explanation: Glucose-6-phosphatase is an enzyme that hydrolyzes glucose-6-phosphate to release free glucose, which is essential for maintaining blood glucose levels.

p.5
Glycogen Metabolism: Synthesis and Degradation

What type of polymer is glycogen?
A) A heteropolymer of proteins
B) A homopolymer of glucose
C) A polymer of lipids
D) A polymer of amino acids
E) A homopolymer of fructose

B) A homopolymer of glucose
Explanation: Glycogen is specifically described as a homopolymer of glucose, meaning it is composed entirely of glucose units linked together.

p.23
Glycogen Storage Disorders: Types and Symptoms

How many different glycogen storage disorders (GSDs) have been described?
A) 5
B) 8
C) 10
D) 12
E) 15

D) 12
Explanation: A total of 12 different glycogen storage disorders (GSDs) have been described, indicating the variety of conditions that can affect glycogen metabolism.

p.7
Glycogenesis: Process and Enzymes

What is the first step in the conversion of glucose to glycogen?
A) Glucose → Glucose-1-P
B) Glucose → Glucose-6-P
C) Glucose-6-P → UDP-glucose
D) UDP-glucose → Glycogen
E) Glucose-1-P → Glucose-6-P

B) Glucose → Glucose-6-P
Explanation: The first step in glycogenesis involves the conversion of glucose to glucose-6-phosphate (glucose-6-P), which is a crucial intermediate in the pathway.

p.7
Glycogenesis: Process and Enzymes

Which enzyme converts glucose-6-P to glucose-1-P?
A) Glycogen synthase
B) Phosphoglucomutase
C) UDP-glucose pyrophosphorylase
D) Hexokinase
E) Glucose-6-phosphatase

B) Phosphoglucomutase
Explanation: Phosphoglucomutase is the enzyme responsible for converting glucose-6-phosphate to glucose-1-phosphate, an important step in glycogenesis.

p.21
Cori Cycle: Lactate to Glucose Conversion

What enzyme processes lactate into pyruvate in the Cori cycle?
A) Glucose-6-phosphatase
B) Lactate dehydrogenase (LDH)
C) Pyruvate kinase
D) Hexokinase
E) Phosphofructokinase

B) Lactate dehydrogenase (LDH)
Explanation: Lactate is converted into pyruvate by the enzyme lactate dehydrogenase (LDH) during the second step of the Cori cycle.

p.11
Glycogenolysis: Mechanism and Regulation

What is the primary function of glycogen phosphorylase in glycogenolysis?
A) To synthesize glycogen
B) To cleave the α-1,4 bond at the non-reducing end
C) To convert glucose-1-phosphate to glucose-6-phosphate
D) To release free glucose from the α-(1,6) bond
E) To transfer glucose residues to a reducing end

B) To cleave the α-1,4 bond at the non-reducing end
Explanation: Glycogen phosphorylase is responsible for cleaving the α-1,4 bond at the non-reducing end of a glycogen branch, generating glucose-1-phosphate, which is a key step in glycogenolysis.

p.12
Glycogenolysis: Mechanism and Regulation

What role does glucose-6-phosphate translocase play in glycogenolysis?
A) It breaks down glycogen
B) It converts G-1-P to G-6-P
C) It moves G-6-P into the endoplasmic reticulum
D) It releases free glucose into the bloodstream
E) It phosphorylates glucose

C) It moves G-6-P into the endoplasmic reticulum
Explanation: Glucose-6-phosphate translocase is responsible for transporting glucose-6-phosphate into the endoplasmic reticulum, where further processing occurs.

p.12
Glycogenolysis: Mechanism and Regulation

What is the function of glucose-6-phosphatase in the liver?
A) To convert G-1-P to G-6-P
B) To release free glucose into the bloodstream
C) To store glucose as glycogen
D) To phosphorylate glucose
E) To transport glucose into muscle cells

B) To release free glucose into the bloodstream
Explanation: Glucose-6-phosphatase in the liver converts glucose-6-phosphate to free glucose, which can then be released into the bloodstream, playing a vital role in maintaining blood glucose levels.

p.11
Glycogenolysis: Mechanism and Regulation

What does amylo-α-(1,6) glucosidase do during glycogenolysis?
A) It synthesizes glycogen
B) It cleaves α-1,4 bonds
C) It releases free glucose from the α-(1,6) bond
D) It phosphorylates glucose-1-phosphate
E) It transfers glucose to a reducing end

C) It releases free glucose from the α-(1,6) bond
Explanation: Amylo-α-(1,6) glucosidase is responsible for releasing free glucose from the α-(1,6) bond during glycogenolysis, which is essential for the complete degradation of glycogen.

p.16
Glycogenesis: Process and Enzymes

What is the active form of glycogen synthase?
A) Inactive 'b' form
B) Active 'a' form
C) Phosphorylated form
D) Dephosphorylated form
E) Glycogen phosphorylase

B) Active 'a' form
Explanation: Glycogen synthase exists in an active 'a' form, which is responsible for glycogen synthesis, contrasting with the inactive 'b' form.

p.14
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What occurs during the fasting state regarding glycogen metabolism?
A) Increased synthesis and decreased degradation
B) Decreased synthesis and increased degradation
C) No change in synthesis or degradation
D) Increased synthesis and increased degradation
E) Decreased degradation and decreased synthesis

B) Decreased synthesis and increased degradation
Explanation: During the fasting state, glycogen metabolism shifts to decreased synthesis and increased degradation to meet the energy needs of the cell, as glucose is released from glycogen stores.

p.22
Glycogen Storage Disorders: Types and Symptoms

What is a common symptom of Glycogen Storage Disorders?
A) Chronic hypoglycemia
B) Increased appetite
C) High blood pressure
D) Weight gain
E) Insomnia

A) Chronic hypoglycemia
Explanation: One of the hallmark symptoms of GSDs is chronic hypoglycemia, which results from the body's inability to properly manage glycogen stores due to enzyme deficiencies.

p.12
Glycogenolysis: Mechanism and Regulation

What is the main direct product of glycogen breakdown?
A) Fructose-1,6-bisphosphate
B) Glucose-1-phosphate
C) Glucose-6-phosphate
D) Lactate
E) Pyruvate

B) Glucose-1-phosphate
Explanation: The primary product of glycogenolysis, or glycogen breakdown, is glucose-1-phosphate, which is crucial for further metabolic processes.

p.17
Hormonal Regulation: Insulin and Glucagon

What is the primary effect of glucagon on glycogen metabolism?
A) It promotes glycogen synthesis
B) It activates glycogen phosphorylase
C) It inhibits glucose release
D) It decreases cAMP levels
E) It activates insulin receptors

B) It activates glycogen phosphorylase
Explanation: Glucagon activates glycogen phosphorylase, leading to the breakdown of glycogen and the release of glucose into the bloodstream.

p.11
Glycogenolysis: Mechanism and Regulation

What does the debranching enzyme do during glycogenolysis?
A) It synthesizes new glycogen
B) It cleaves α-1,4 bonds only
C) It removes the last 3 glucose residues and releases free glucose
D) It phosphorylates glucose-1-phosphate
E) It transfers glucose to the reducing end

C) It removes the last 3 glucose residues and releases free glucose
Explanation: The debranching enzyme has two activities: it removes the last 3 glucose residues from a branch and transfers them to a non-reducing end, and it releases free glucose from the α-(1,6) bond.

p.11
Glycogenolysis: Mechanism and Regulation

What is the role of oligo-α-(1,4)-α-(1,4) glucan transferase in glycogenolysis?
A) To synthesize glycogen
B) To release free glucose
C) To transfer glucose residues to a non-reducing end
D) To cleave α-1,6 bonds
E) To phosphorylate glucose

C) To transfer glucose residues to a non-reducing end
Explanation: Oligo-α-(1,4)-α-(1,4) glucan transferase is part of the debranching enzyme that removes the last 3 glucose residues from a branch and transfers them to a non-reducing end, facilitating further degradation of glycogen.

p.17
Hormonal Regulation: Insulin and Glucagon

What mixed effects does cortisol have on glycogen metabolism?
A) It only promotes glycogen synthesis
B) It only promotes glycogen breakdown
C) It increases glycogen synthesis in liver and promotes breakdown in muscle
D) It has no effect on glycogen metabolism
E) It activates insulin receptors

C) It increases glycogen synthesis in liver and promotes breakdown in muscle
Explanation: Cortisol has mixed effects on glycogen metabolism, increasing glycogen synthesis in the liver while promoting glycogen breakdown in muscle, reflecting its complex role in energy regulation.

p.20
Gluconeogenesis: Pathway and Substrates

What is the source of glycerol used in gluconeogenesis?
A) Muscle tissue
B) Liver glycogen
C) Fat stores (triglycerides)
D) Blood glucose
E) Dietary carbohydrates

C) Fat stores (triglycerides)
Explanation: Glycerol, which is derived from the breakdown of triglycerides in fat stores, serves as a substrate for gluconeogenesis, contributing to glucose production during fasting or low-carbohydrate conditions.

p.14
Regulation of Glycogen Metabolism: Allosteric and Hormonal

Which enzyme is primarily responsible for glycogen synthesis?
A) Glycogen Phosphorylase
B) Glycogen Synthase
C) Hexokinase
D) Glucose-6-phosphatase
E) Phosphofructokinase

B) Glycogen Synthase
Explanation: Glycogen Synthase is the primary enzyme responsible for the synthesis of glycogen, playing a crucial role in regulating glycogen metabolism based on the energy state of the cell.

p.23
Glycogen Storage Disorders: Types and Symptoms

What percentage of all glycogen storage disorders does GSD I account for?
A) 10%
B) 15%
C) 20%
D) 25%
E) 30%

D) 25%
Explanation: GSD I accounts for 25% of all glycogen storage disorders, highlighting its prevalence among these metabolic conditions.

p.22
Glycogen Storage Disorders: Types and Symptoms

How many types of Glycogen Storage Disorders are known?
A) 5 types
B) 8 types
C) 10 types
D) 12 types
E) 15 types

D) 12 types
Explanation: There are 12 known types of Glycogen Storage Disorders (GSD I - XII), with the severity of the disease depending on the specific enzyme affected and its distribution in tissues.

p.22
Glycogen Storage Disorders: Types and Symptoms

Which tissues can be affected by Glycogen Storage Disorders?
A) Only the liver
B) Only the muscles
C) Both the liver and muscles
D) Only the brain
E) Only the skin

C) Both the liver and muscles
Explanation: GSDs can affect both the liver and muscle tissues, leading to a variety of symptoms depending on the specific disorder and the enzymes involved.

p.21
Cori Cycle: Lactate to Glucose Conversion

Who are the discoverers of the Cori cycle?
A) Watson and Crick
B) Carl and Gerty Cori
C) Louis Pasteur
D) Albert Einstein
E) Gregor Mendel

B) Carl and Gerty Cori
Explanation: The Cori cycle is named after its discoverers, Carl and Gerty Cori, who identified this metabolic pathway in 1929.

p.18
Gluconeogenesis: Pathway and Substrates

What is a key characteristic of the irreversible steps of glycolysis in relation to gluconeogenesis?
A) They are the same in both pathways
B) They are bypassed in gluconeogenesis
C) They are accelerated during gluconeogenesis
D) They do not exist in gluconeogenesis
E) They are only present in the liver

B) They are bypassed in gluconeogenesis
Explanation: The irreversible steps of glycolysis are bypassed in gluconeogenesis, which requires specific enzymes to facilitate the conversion of precursors into glucose.

p.19
Gluconeogenesis: Pathway and Substrates

What is the role of PEP-carboxy kinase in gluconeogenesis?
A) Converts glucose to glucose-6-phosphate
B) Converts oxaloacetate to phosphoenolpyruvate
C) Converts fructose-1,6-bisphosphate to fructose-6-phosphate
D) Converts pyruvate to lactate
E) Converts ADP to ATP

B) Converts oxaloacetate to phosphoenolpyruvate
Explanation: PEP-carboxy kinase catalyzes the conversion of oxaloacetate to phosphoenolpyruvate, which is a key step in gluconeogenesis.

p.5
Glycogen Metabolism: Synthesis and Degradation

What types of glycosidic bonds are present in glycogen?
A) β-1,4 and β-1,6
B) α-1,4 and α-1,6
C) α-1,2 and β-1,4
D) β-1,3 and α-1,6
E) α-1,4 and β-1,6

B) α-1,4 and α-1,6
Explanation: Glycogen is characterized by the presence of α-1,4 and α-1,6 glycosidic bonds, which are crucial for its structure and function as a storage form of glucose.

p.3
Physiological States: Fed and Fasting

What happens to plasma glucose levels during fasting?
A) They increase
B) They remain constant
C) They decrease
D) They fluctuate wildly
E) They become undetectable

C) They decrease
Explanation: During the fasting state, plasma glucose levels are reduced, which is a key characteristic of the body's metabolic response to fasting.

p.12
Glycogenolysis: Mechanism and Regulation

Which enzyme converts glucose-1-phosphate to glucose-6-phosphate?
A) Glycogen phosphorylase
B) Phosphoglucomutase
C) Glucose-6-phosphatase
D) Hexokinase
E) Phosphofructokinase

B) Phosphoglucomutase
Explanation: Phosphoglucomutase is the enzyme responsible for converting glucose-1-phosphate to glucose-6-phosphate, facilitating the next steps in glucose metabolism.

p.4
Glycogen Metabolism: Synthesis and Degradation

Where is glycogen primarily stored in the body?
A) Heart and lungs
B) Liver and muscle
C) Brain and skin
D) Kidneys and intestines
E) Blood and plasma

B) Liver and muscle
Explanation: Glycogen is primarily stored in the liver (approximately 100g) and muscle (approximately 400g), serving as a readily mobilizable form of glucose.

p.9
Glycogenesis: Process and Enzymes

What enzyme is responsible for creating branches in glycogen?
A) Glycogen phosphorylase
B) Glycogen synthase
C) Branching enzyme
D) Amylase
E) Glucose-6-phosphatase

C) Branching enzyme
Explanation: The branching enzyme is specifically responsible for breaking a chain of 5-8 glucose residues off the non-reducing end of glycogen and attaching it via an α-1,6 bond, creating branches in the glycogen structure.

p.12
Glycogenolysis: Mechanism and Regulation

Why do muscle cells not release glucose into the bloodstream?
A) They lack glycogen
B) They do not have glucose-6-phosphatase
C) They only store glucose
D) They convert all glucose to lactate
E) They do not metabolize glucose

B) They do not have glucose-6-phosphatase
Explanation: Muscle cells lack the enzyme glucose-6-phosphatase, which prevents them from converting glucose-6-phosphate to free glucose, thus they do not release glucose into the bloodstream.

p.15
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What is the effect of Glucose-6-P in the liver on Glycogen Synthase?
A) Inhibits Glycogen Synthase
B) Activates Glycogen Synthase
C) Has no effect on Glycogen Synthase
D) Degrades Glycogen Synthase
E) Converts Glycogen Synthase to Glucose

B) Activates Glycogen Synthase
Explanation: In the liver, Glucose-6-P allosterically activates Glycogen Synthase, promoting the synthesis of glycogen.

p.17
Hormonal Regulation: Insulin and Glucagon

How does insulin affect glycogen synthesis?
A) It activates glycogen phosphorylase
B) It inactivates protein kinase A
C) It activates PP1
D) It increases cAMP levels
E) It promotes glucagon release

C) It activates PP1
Explanation: Insulin activates PP1, which in turn activates glycogen synthase and inhibits phosphorylase, promoting glycogen synthesis and glucose storage.

p.17
Hormonal Regulation: Insulin and Glucagon

What role does adrenaline play in glycogen metabolism during exercise?
A) It decreases cAMP levels
B) It promotes glycogen synthesis
C) It activates glycogen phosphorylase
D) It inhibits glucagon release
E) It activates insulin receptors

C) It activates glycogen phosphorylase
Explanation: Adrenaline, released during exercise, activates glycogen phosphorylase, leading to glycogen breakdown and glucose release for energy.

p.15
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What role does AMP play in muscle glycogen metabolism?
A) It inhibits Glycogen Synthase
B) It activates Glycogen Synthase
C) It activates Glycogen Phosphorylase
D) It has no effect on glycogen metabolism
E) It converts glycogen to glucose

C) It activates Glycogen Phosphorylase
Explanation: AMP, generated during ATP depletion, activates Glycogen Phosphorylase in muscle, promoting glycogen breakdown to meet energy needs.

p.15
Glycogenesis: Process and Enzymes

What is the primary function of Glycogen Synthase in the liver?
A) To break down glycogen
B) To synthesize glycogen
C) To convert glucose to pyruvate
D) To regulate blood sugar levels
E) To produce ATP

B) To synthesize glycogen
Explanation: Glycogen Synthase is primarily responsible for the synthesis of glycogen in the liver, facilitating the storage of glucose.

p.2
Physiological States: Fed and Fasting

What is the primary fuel source for tissues during the fed state?
A) Fatty acids
B) Ketones
C) Glucose
D) Amino acids
E) Lactate

C) Glucose
Explanation: During the fed state, tissues primarily use glucose as their fuel source, taking advantage of the high plasma glucose levels resulting from nutrient intake.

p.19
Gluconeogenesis: Pathway and Substrates

Which enzyme is responsible for converting pyruvate to oxaloacetate in gluconeogenesis?
A) Fructose-1,6-bisphosphatase
B) Pyruvate carboxylase
C) PEP-carboxy kinase
D) Glucose-6-phosphatase
E) Hexokinase

B) Pyruvate carboxylase
Explanation: Pyruvate carboxylase is the enzyme that catalyzes the conversion of pyruvate to oxaloacetate, a crucial step in the gluconeogenesis pathway.

p.15
Regulation of Glycogen Metabolism: Allosteric and Hormonal

What is the effect of Glucose-6-P on Glycogen Phosphorylase in the liver?
A) Activates Glycogen Phosphorylase
B) Inhibits Glycogen Phosphorylase
C) Has no effect on Glycogen Phosphorylase
D) Converts Glycogen Phosphorylase to Glucose
E) Degrades Glycogen Phosphorylase

B) Inhibits Glycogen Phosphorylase
Explanation: Glucose-6-P in the liver inhibits Glycogen Phosphorylase, which reduces the breakdown of glycogen.

p.15
Regulation of Glycogen Metabolism: Allosteric and Hormonal

Which substances activate Glycogen Phosphorylase in muscle?
A) Glucose-6-P and ATP
B) Ca2+ and AMP
C) Insulin and Glucose
D) Glycogen and Fructose
E) Lactate and Pyruvate

B) Ca2+ and AMP
Explanation: In muscle, Ca2+ released during contraction and AMP generated by ATP depletion activate Glycogen Phosphorylase, facilitating glycogen breakdown during energy-demanding situations.

p.13
Glycogen Metabolism: Synthesis and Degradation

What does G6P translocase do?
A) Synthesizes glycogen
B) Transports glucose-6-phosphate across membranes
C) Degrades glycogen
D) Converts glucose to glucose-6-phosphate
E) Regulates insulin secretion

B) Transports glucose-6-phosphate across membranes
Explanation: G6P translocase is responsible for transporting glucose-6-phosphate across the endoplasmic reticulum membrane, facilitating its conversion to glucose by glucose-6-phosphatase.

p.13
Glycogenolysis: Mechanism and Regulation

Which molecule is primarily involved in the conversion of glycogen to glucose during glycogenolysis?
A) Glucose
B) Glucose-6-phosphate
C) Glycogen synthase
D) Phosphoglucomutase
E) Glucose-6-phosphatase

B) Glucose-6-phosphate
Explanation: Glucose-6-phosphate is a key intermediate in glycogenolysis, as it is produced from glycogen breakdown and can be further converted to glucose by glucose-6-phosphatase.

p.13
Glycogenolysis: Mechanism and Regulation

What is glycogenolysis?
A) The synthesis of glycogen
B) The degradation of glycogen
C) The conversion of glucose to glucose-6-phosphate
D) The transport of glucose into cells
E) The regulation of blood sugar levels

B) The degradation of glycogen
Explanation: Glycogenolysis refers to the biochemical process of breaking down glycogen into glucose-6-phosphate and glucose, which is crucial for energy production during fasting or intense exercise.

p.9
Glycogenesis: Process and Enzymes

What is the function of the enzyme amylo-α-1,4-α-1,6-transglucosidase?
A) It breaks down glycogen
B) It synthesizes glucose
C) It creates branches in glycogen
D) It transports glucose
E) It converts glycogen to glucose-6-phosphate

C) It creates branches in glycogen
Explanation: The enzyme amylo-α-1,4-α-1,6-transglucosidase, also known as the branching enzyme, facilitates the branching of glycogen by breaking α-1,4 bonds and forming α-1,6 bonds, which is crucial for glycogen structure.

p.19
Glycolysis: Process and Enzymes

Which enzyme is a key regulatory step in glycolysis and is inhibited by ATP?
A) Glucose-6-phosphatase
B) Pyruvate carboxylase
C) Phosphofructokinase
D) PEP-carboxy kinase
E) Hexokinase

C) Phosphofructokinase
Explanation: Phosphofructokinase is a key regulatory enzyme in glycolysis that is inhibited by high levels of ATP, indicating sufficient energy availability.

p.9
Glycogenesis: Process and Enzymes

What is the role of glycogen synthase in glycogen metabolism?
A) To break down glycogen
B) To create branches in glycogen
C) To synthesize glycogen
D) To convert glucose to pyruvate
E) To transport glucose into cells

C) To synthesize glycogen
Explanation: Glycogen synthase is the enzyme responsible for synthesizing glycogen by adding glucose units to the growing glycogen chain, utilizing the non-reducing ends created by the branching enzyme.

Study Smarter, Not Harder
Study Smarter, Not Harder