Integration of Metabolism Flashcards
What is the primary energy source for the brain?
glucose
How much of the body’s total oxygen consumption does the brain use?
over 20%
What are the main byproducts of brain metabolism?
carbon dioxide and lactate
How does the brain adapt to low glucose levels?
The brain can adapt to low glucose levels by using ketone bodies as an alternative energy source.
Discuss the astrocyte-neuron-lactate shuttle.
✔ Astrocytes take up glucose from the blood and convert it to lactate through glycolysis. The lactate produced by astrocytes is then released into the extracellular space.
✔ Neurons take up the lactate and convert it back to pyruvate, which enters the mitochondria to produce ATP through oxidative phosphorylation.
What is the normal range for glucose levels in the blood?
60 - 90 mg/ml
What is the primary metabolic pathway in erythrocytes?
glycolysis
Why do erythrocytes rely on anaerobic glycolysis?
They lack mitochondria and hence cannot perform oxidative phosphorylation.
Fed state metabolism
What triggers the release of insulin in the fed state?
elevated glucose levels in the bloodstream
Fed state metabolism
What is the primary glucose transporter in the liver during the fed state?
GLUT2 (insulin-independent)
Further notes:
GLUT2 has a high capacity for glucose transport but a low affinity, meaning it efficiently transports glucose when glucose levels are high.
Fed state metabolism
Which tissues use GLUT4 transporters for glucose uptake in the fed state?
Skeletal muscle and adipose tissue
How is GLUT4 regulated?
It is regulated by insulin. When insulin binds to its receptors on the cell surface, it triggers a cascade of events that leads to the translocation of GLUT4 from intracellular compartments to the cell membrane, allowing glucose to be taken up from the bloodstream into the cells.
Fed state metabolism
What is the main metabolic process in the liver during the fed state?
Glycogenesis (conversion of glucose to glycogen).
Fed state metabolism
How does insulin affect lipid metabolism in adipose tissue?
It promotes lipogenesis (fat storage)
Fed state metabolism
What is the role of insulin in protein metabolism in muscles?
It stimulates protein synthesis.
Fed state metabolism
Which glucose transporter is predominant in the brain during the fed state?
GLUT1 and GLUT3 (insulin-independent).
Fed state metabolism
What is the role of insulin in the brain during the fed state?
Insulin has minimal direct effect; glucose uptake is insulin-independent.
Fed state metabolism
Outline the effects of insulin on:
(a) Glucose metabolism
(b) Lipid metabolism
(c) Protein metabolism
(a) Glucose metabolism
✓ Increased Glucose Uptake: Insulin promotes the uptake of glucose into cells, especially in muscle and adipose tissue, via GLUT4 transporters.
✓ Glycogenesis: In the liver and muscle, insulin stimulates the conversion of glucose to glycogen for storage.
✓ Inhibition of Gluconeogenesis: Insulin suppresses the production of glucose from non-carbohydrate sources in the liver.
(b) Lipid metabolism
✓ Lipogenesis: Insulin promotes the synthesis of fatty acids and triglycerides in adipose tissue and the liver.
✓ Inhibition of Lipolysis: Insulin inhibits the breakdown of stored fats, reducing the release of free fatty acids into the bloodstream.
(c) Protein metabolism
✓ Protein Synthesis: Insulin stimulates the uptake of amino acids into cells and promotes protein synthesis, particularly in muscle tissue.
✓ Inhibition of Proteolysis: Insulin reduces the breakdown of proteins, preserving muscle mass.
Fasted state metabolism
What triggers the fasted state metabolism?
Decrease in serum glucose levels and insulin production, leading to an increase in glucagon, cortisol and epinephrine
Fasted state metabolism
What is the primary hormone that increases during the fasted state?
glucagon
Fasted state metabolism
What metabolic process is stimulated by glucagon in the liver during fasting?
glycogenolysis
Fasted state metabolism
Which metabolic pathway is activated to produce glucose from non-carbohydrate sources during fasting?
gluconeogenesis
Fasted state metabolism
What are the primary substrates for gluconeogenesis?
amino acids, lactate, and glycerol
Fasted state metabolism
What happens to fatty acids during the fasted state?
They are mobilized from adipose tissue and undergo beta-oxidation.
Fasted state metabolism
What is beta-oxidation?
The process of breaking down fatty acids to produce acetyl-CoA.
In which part of the cell does fatty acid synthesis occur?
Cytoplasm
Fasted state metabolism
What role does cortisol play in the fasted state?
It promotes gluconeogenesis and proteolysis to form amino acids.
Fasted state metabolism
How does epinephrine affect metabolism during fasting?
It stimulates glycogenolysis and lipolysis.
Fasted state metabolism
What happens to acetly-CoA produced from beta-oxidation in the liver?
It is converted to ketone bodies.
Fasted state metabolism
Which tissues primarily use ketone bodies during prolonged fasting?
brain, heart, skeletal muscles
Fasted state metabolism
What happens to muscle protein during prolonged fasting?
It is broken down to provide amino acids for gluconeogenesis.
Insulin Transduction Pathway
What is the primary function of the insulin transduction pathway?
The insulin transduction pathway increases glucose uptake into fat and muscle cells and reduces glucose synthesis in the liver, maintaining glucose homeostasis.
Insulin Transduction Pathway
What happens when insulin binds to its receptor?
✔ Insulin binding to its receptor triggers autophosphorylation of the receptor’s intracellular tyrosine residues, initiating a cascade of downstream signaling events.
✔ One of the key outcomes of this signalling cascade is the translocation of glucose transporter proteins (such as GLUT4) to the cell membrane, allowing glucose to enter the cell.
What is the role of insulin receptor substrate 1 (IRS-1) in the pathway?
IRS-1 is phosphorylated by the activated insulin receptor, creating docking sites for downstream signaling molecules like Phosphoinositide 3-kinase (PI3K).
How does the PI3K/Akt pathway contribute to glucose uptake?
The PI3K/Akt pathway promotes the translocation of GLUT4 vesicles to the plasma membrane, facilitating glucose uptake into cells.
What is the significance of GLUT4 in the insulin signaling pathway?
GLUT4 is a glucose transporter that moves to the cell surface in response to insulin signaling, allowing glucose to enter muscle and adipose cells.
What is diabetes mellitus?
Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia due to defects in insulin secretion, insulin action or both.
What are the main types of diabetes mellitus?
Type 1 diabetes (insulin-dependent)
Type 2 diabetes (non-insulin dependent)
What causes Type 1 diabetes?
Type 1 diabetes is caused by autoimmune destruction of pancreatic beta cells, leading to an absolute deficiency of insulin.
What causes Type 2 diabetes?
Type 2 diabetes is caused by insulin resistance and relative insulin deficiency, often associated with obesity and genetic factors.
How is glycated haemoglobin (HbA1c) formed?
It forms when glucose in the blood binds to haemoglobin in red blood cells.
How is HbA1c used as a diagnostic tool?
It is used to diagnose and monitor diabetes. Higher HbA1c levels indicate poorer blood sugar control.
(a) What is the normal range for HbA1c levels?
(b) What HbA1c levels indicate prediabetes?
(c) What HbA1c levels are diagnostic of diabetes?
(a) HbA1c levels below 5.7% are considered normal.
(b) Levels between 5.7% and 6.4% indicate prediabetes.
(c) 6.5% or higher
List 6 strategies for management of diabetes mellitus.
(1) Administering insulin itself in the case of Type 1 diabetes mellitus
(2) Increasing insulin secretion by the pancreas in Type 1 diabetes mellitus
(a) by use of secretagogues e.g. sulfonylureas such as Glimepiride and Glipizide. They increase release of insulin from the pancreas. (b) Non-sulfonylureas e.g. Repaglinide, Nateglinide and Mitiglinide. They inhibit (close) K-ATP channels and open calcium channels of beta cells causing release of insulin. Reduces glucagon secretion in alpha cells. They are generally known as Glinides.
(3) Increase sensitivity of target organs to insulin
Use of sensitizers which address the core problem of insulin resistance in Type II diabetes mellitus…
(a) Biguanides e.g. metformin (Glucophage) which decrease glucose output by inhibiting gluconeogenesis in the liver and also increase the uptake of glucose by tissues. Acts mainly in the liver. (b) Thiazolidinediones e.g. Pioglitazone which regulate glucose and fat metabolism by making better use of glucose by cells. They increase sensitivity by acting mainly on adipse tissue and muscle. They promote glucose entry.
(4) Decrease the digestion and absorption of glucose from the GIT
By use of alpha-glucose inhibitors e.g. Glucobay (Acarbose). They are antihyperglycemic agents. They lower blood glucose by delaying the digestion and absorption of complex CHOs. They are competitive inhibitors of the enzymes (lysosomal glucosidases) in the brush border of enterocytes that cleave complex carbohydrates to monosaccharides.
(5) Increase sugar loss through urination
Use oral Glycosurics which inhibit SGLT-2 in kidneys i.e. SGLT-2 inhibitors aka. Gliflozins. Remove sugar through urine by providing lower glucose reabsorption in the kidneys. They are hypoglycemic drugs.
(6) Use of peptide analogues (injectable)
They are GLP-1 and GIP agnoists. They are incretin mimetics e.g. semaglutide. They are agents that act like incretin hormones such as GLP-1. They bind to GLP-1 receptors and stimulate insulin release. They suppress appetite and inhibit glucagon secretion. They are called Gliptins.
Rapoport-Leubering Cycle
What is the Rapoport-Leubering cycle?
It is a metabolic pathway in red blood cells that produces 2,3-bisphosphoglycerate (2,3-BPG), which regulates oxygen release from hemoglobin.
[Diagram]
Rapoport-Leubering Cycle
What enzyme catalyzes the formation of 2,3-BPG in the Rapoport-Leubering cycle?
Bisphosphoglycerate mutase.
[Diagram]
Rapoport-Leubering Cycle
What is the main function of 2,3-BPG in red blood cells?
It decreases the affinity of haemoglobin for oxygen, facilitating oxygen release to tissues.
Rapoport-Leubering Cycle
How does the Rapoport-Leubering cycle affect ATP production?
One mole of ATP is lost in the formation of 2,3-BPG from 1,3-BPG. [Diagram]
Rapoport-Leubering Cycle
What conditions can increase the levels of 2,3-BPG?
Hypoxia, high altitude, and certain types of anemia. [Diagram]
Rapoport-Leubering Cycle
Which enyzme converts 2,3-BPG to 3-phosphoglycerate in the Rapoport-Leubering cycle?
bisphosphoglycerate phosphatase
[Diagram]
Further notes:
Phosphatases remove phosphate groups from proteins or other molecules, a process called dephosphorylation.
Kinases add phosphate groups to proteins or other molecules, a process known as phosphorylation.
Which of the following pathways would not occur in the in the liver mitochondria?
(a) FA oxidation
(b) FA synthesis
(c) Ketone body (KB) synthesis
(d) Urea synthesis
(e) FA metabolism
(b) FA synthesis
Which of the following tissues is most dependent upon a constant blood supply of glucose?
(a) adipose tissue
(b) liver
(c) brain
(d) pancreas
(e) skeletal muscle
(c) brain
The following substrates may be used for brain energy metabolism, except ________.
(a) fatty acids
(b) ketone bodies
(c) glycogen
(d) lactate
(e) glucose
(a) fatty acids
A 22-year old student has been fasting for religious reasons for several days. His brain has reduced its need for glucose by using which of the following compounds as an alternative source of energy?
(a) Glycerol
(b) Fatty acids
(c) Acetoacetate
(d) Alanine
(e) Fructose
(c) Acetoacetate
During starvation, the brain utilizes ________.
(a) glucose
(b) glycerol
(c) ketone bodies
(d) fatty acids
(e) all of the above
(c) ketone bodies
________ which is localized on the blood-brain barrier moves glucose from capillary lumen to the brain interstitium.
(a) GLUT4 (55kd form)
(b) GLUT2 (55kd form)
(c) GLUT3 (60kd form)
(d) GLUT3/GLUT1 (45kd form)
(e) GLUT1 (55kd form)
(e) GLUT1 (55kd form)
Explanation:
GLUT3 (60kd form): GLUT3 has a high affinity for glucose and is found primarily in neurons. While it’s important for neuronal glucose uptake, it’s not the transporter responsible for moving glucose across the blood-brain barrier from the capillary lumen to the brain interstitium. GLUT1 does that job.
Liver glycogen is used in fasting to provide glucose for use by other ussues including brain. However, muscle glycogen is not. What is the explanation for this?
(a) Muscle cannot degrade glycogen further than GIP.
(b) The liver provides all the glucose necessary for metabolism and there is no need for muscle to do the same.
(c) Muscle lacks glucose-6-phosphatase.
(d) Muscle lacks the debranching enzyme.
(e) None of the above.
(c) Muscle lacks glucose-6-phosphatase.
Further notes:
Muscle cells store glycogen for their own use during times of increased activity and do not release glucose into the bloodstream. This is because muscle cells lack the enzyme glucose-6-phosphatase, which is necessary to convert G6P into free glucose that can be released into the blood.
Which of the following is true of brain metabolism in starvation?
(a) The brain can only use glucose as fuel.
(b) Up to a quarter of the energy requirements of the brain can come from fatty acids.
(c) Up to half of the energy requirements of the brain can be met by ketone bodies.
(d) The brain can use glucogenic amino acids for energy.
(e) None of the above is correct.
(c) Up to half of the energy requirements of the brain can be met by ketone bodies.
Mohammed Ali has been fasting for religious reasons for several days. His brain has reduced its need for glucose by using ________ as an alternative source of energy.
(a) fatty acids
(b) glycerol
(c) alanine
(d) beta carotene
(e) beta hydroxybutyrate
(e) beta hydroxybutyrate
The following two compounds can be used by the brain for energy production when glucose is unavailable.
(a) fumarate and oxaloacetate
(b) acetoacetate and beta-hydroxybutyrate
(c) pyruvate and phosphoenolpyruvate
(d) glyceraldehyde-3-phosphate and dihydroxyacetone phosphate
(e) citrate and malate
(b) acetoacetate and beta-hydroxybutyrate
Which of the following is not associated with the red blood cell (RBC)?
(a) It plays a role in adaption to high altitude.
(b) Under high oxygen tension, it modifies its glycolytic pathway.
(c) It utilizes exclusively glucose.
(d) Its energy is dependent on glycolysis.
(e) All the above are correct.
(e) All the above are correct.
In erythrocytes, the most abundant phosphoester is ________.
(a) G6P
(b) Fructose-1,6-biphosphate
(c) Fructose-6-phosphate
(d) 1,3-biphosphoglycerate
(e) 2,3-biphosphoglycerate
(e) 2,3-biphosphoglycerate
Which of the following is false about the Bohr’s Effect on red blood cells?
(a) Acidity increases.
(b) pH decreases.
(c) It is relevant to the lungs.
(d) There is reduced hemoglobin affinity for oxygen.
(e) All of the above.
(c) It is relevant to the lungs.
Further notes:
◾ The Bohr effect refers to the physiological phenomenon where haemoglobin’s oxygen binding affinity is inversely related to both acidity and the concentration of carbon dioxide.
◾ In simpler terms, haemoglobin releases oxygen more readily under conditions of lower pH and higher CO2 conditions.
Which of the following is false about the Haldane’s effect on red blood cells?
(a) It is relevant to the lungs.
(b) The presence of oxygen helps the release of CO2 from hemoglobin.
(c) It demonstrates the positive cooperativity binding of hemoglobin to oxygen.
(d) It demonstrates the role of O2 in lungs.
(e) All of the above.
(c) It demonstrates the positive cooperativity binding of hemoglobin to oxygen.
Explanation:
Positive cooperativity refers to the increasing affinity of haemoglobin for oxygen as more oxygen molecules bind. The Haldane effect is about the inverse relationship between oxygen binding and CO2 binding.
________ catalyzes a modified form of glycolysis in the human red blood cells.
(a) Phosphoglucomutase
(b) 2,3-biphosphoglucomutase
(c) 2,3-biphosphoglycerate mutase
(d) 1,2-BPG
(e) 1,3-BPG
(c) 2,3-biphosphoglycerate mutase
What is false regarding times of carbohydrate plenty?
(a) Net deposition of fat
(b) Much release of free fatty acids into blood
(c) High blood TGs
(d) Low blood ketone bodies
(e) Insulin/glucagon ratio is high
(b) Much release of free fatty acids into blood
Which of the following metabolic processes will occur during the post-prandial period [about two hours after ingestion of a high carbohydrate meal]?
(a) Insulin stimulates transport of glucose into the brain
(b) Adipose tissue and skeletal muscle will utilize glucose as their major fuel
(c) Skeletal muscle converts glucose to fatty acids
(d) Fatty acid synthesis in the liver decreases
(e) Glucagon is released from the pancreas
(b) Adipose tissue and skeletal muscle will utilize glucose as their major fuel
Repeatedly overloading the bloodstream with sugar can diminish the body’s ability to respond to ________.
(a) glucagon
(b) noradrenaline
(c) insulin
(d) epinephrine
(e) DOPA
(c) insulin
A particular pathogen is unable to synthesize glycine, what nitrogenous product other than proteins or peptides would the pathogen fail to synthesize?
(a) purine nucleotides
(b) insulin
(c) folic acid
(d) glycosaminoglycans
(e) glutathione
(a) purine nucleotides
A 14-year-old Type I diabetic faints after injecting himself with insulin. Luckily, he is administered glucagon and rapidly recovers consciousness. Glucagon induces the activity of:
(a) glucokinase
(b) hexokinase
(c) glycogen synthase
(d) glycogen phosphorylase
(e) phosphofructokinase 1
(d) glycogen phosphorylase
Explanation:
◾ Glycogen phosphorylase catalyses the rate-limiting step in glycogenolysis. It breaks down glycogen by removing glucose molecules one at a time from the non-reducing ends of glycogen chains.
◾ The product of this reaction is glucose-1-phosphate.
Which of the following is not a manifestation of insulin deficiency?
(a) Glycosuria
(b) Metabolic acidosis
(c) Keto acidosis
(d) Polydipsia
(e) Polyuria
(b) Metabolic acidosis
Which of the following is untrue about ketogenesis?
(a) It occurs in fasting and in starvation.
(b) It occurs in diabetes mellitus.
(c) It is meant to divert excess acetylCoA from the liver to the peripheral tissues.
(d) It occurs due to failure of the tissues to use glucose thereby tissues turn to burning more fatty acids.
(e) None of the above.
(c) It is meant to divert excess acetylCoA from the liver to the peripheral tissues.
Explanation:
Ketogenesis primarily occurs in the liver to produce ketone bodies, which are then used as an alternative energy source by peripheral tissues during periods of low glucose availability, such as fasting, starvation, or diabetes mellitus. It is not specifically meant to divert excess acetylCoA from the liver to the peripheral tissues.
Which of the following statements are not true regarding ketogenesis?
(a) It occurs in diabetes mellitus.
(b) It occurs due to failure of the tissues to use glucose thereby tissues turn to burning more fatty acids.
(c) The products of the pathway are used in the liver.
(d) It occurs in both fasting and in starvation.
(e) None of the above.
(c) The products of the pathway are used in the liver.
Which of the following statements is not true regarding ketogenesis?
(a) It occurs due to failure of the tissues to utilize glucose effectively thereby tissues turn to burning more fatty acids.
(b) It is mainly associated with obesity.
(c) It occurs in diabetes mellitus.
(d) It occurs in fasting and in starvation.
(e) None of the above.
(b) It is mainly associated with obesity.
Which of the following is not true about glucagon?
(a) It reinforces the effect of epinephrine.
(b) It has no effect on skeletal muscles.
(c) It promotes gluconeogenesis in liver.
(d) It promotes the activity of glycogen phosphorylase in liver.
(e) It promotes TG lipase activity in adipocytes.
(b) It has no effect on skeletal muscles.
Explanation:
While the effect is minimal and not the primary function of glucagon, skeletal muscles do have glucagon receptors, and there are some indirect effects. However, the direct effect of glucagon on muscle is insignificant compared to its action on the liver and adipose tissue.
Glucagon ________.
(a) does not promote gluconeogenesis in the liver
(b) is secreted in increased levels of glucose in plasma
(c) is synthesized by α-cells of pancreatic cells
(d) does not promote gluconeogenesis in the liver
(e) is composed of two polypeptide chains
(c) is synthesized by α-cells of the pancreas
Further notes:
Regarding (e): Glucagon comprises only one polypeptide chain.
Which of the following is least affected by the action of glucagon?
(a) kidney
(b) adipose tissue
(c) muscle
(d) liver
(c) muscle
Explanation:
Glucagon’s primary role is to increase blood glucose levels. It does this mainly by targeting the liver and adipose tissue.
Which of the following is false about the synthesis of a triacylglycerol?
(a) Esterification is insulin dependent.
(b) Esterification results in loss of 3 molecules of water.
(c) Fatty acids participate in form of fattyacylCoAs.
(d) Glycerol participates in the form of glycerol-3-phosphate.
(e) Occurs in the mitochondrial matrix of hepatocytes and adipocytes.
(e) Occurs in the mitochondrial matrix of hepatocytes and adipocytes.
Further notes:
Triacylglycerol synthesis actually occurs in the endopalsmic reticulum of cells, not in the mitochondrial matrix.
Which of the following strategies would not lower plasma cholesterol levels?
(a) Use of statins.
(b) Use of nicotinic acid.
(c) Use of fibrates.
(d) Use of resins.
(e) Ingestion of only proteins.
(e) Ingestion of only proteins.
________ takes place both in the cytosol and in the mitochondrial matrix of a hepatocyte.
(a) Gluconeogensis
(b) FA oxidation
(c) Ketogenesis
(d) Pentose phosphate pathway
(e) FA synthesis
(a) Gluconeogensis
2,3-BPG is synthesized from 1,3-BPG through the ________.
(a) uronic acid pathway
(b) Rapoport-Leubering pathway
(c) Krebs-Henseleit cycle
(d) PPP
(e) Glycolytic pathway
(b) Rapoport-Leubering pathway
In the fasting state, there is considerable release of ________ from the muscles.
(a) glutamate
(b) glutamine
(c) citrate
(d) glycine
(e) alanine
(e) alanine
Which of the following metabolic effects is not true of epinephrine?
(a) It promotes glycogenolysis in muscle and liver.
(b) It inhibits glycogenesis in liver and muscle.
(c) It promotes gluconeogenesis in liver and muscle.
(d) It promotes glycolysis in muscle.
(e) It promotes fatty acid mobilization in the adipose tissue.
(c) It promotes gluconeogenesis in liver and muscle.
Which of the following constitute Stage I of fatty acid catabolism?
(a) Fatty acid activation to fatty acyl CoA
(b) TCA cycle
(c) Oxidation of acetylCoA to CO2
(d) β-oxidation
(e) Hydrogenation reactions
(a) Fatty acid activation to fatty acyl CoA
Which of the following is false about Orlistat, the anti-obesity drug?
(a) It inhibits lipoprotein lipase
(b) It inhibits gastric lipase
(c) It inhibits pancreatic lipase
(d) It inhibits both gastric and pancreatic lipases
(e) It causes malabsorption in the gastrointestinal tract
(a) It inhibits lipoprotein lipase
Explanation:
✔ Orlistat works by inhibiting pancreatic lipase, which is responsible for breaking down fats in the intestine, leading to decreased fat absorption and causing malabsorption in the gastrointestinal tract. It does not inhibit lipoprotein lipase or gastric lipase.
✔ Lipoprotein lipase primarily hydrolyses triglycerides present in chylomicrons and very low-density lipoproteins (VLDLs) into free fatty acids and glycerol. This process takes place on the surface of capillary endothelial cells, particularly in adipose tissue, muscle and the heart.
The liver is unable to utilize ketone bodies because it lacks a ________.
(a) reductase
(b) kinase
(c) transferase
(d) dehydrogenase
(e) thiolase
(c) transferase
Explanation:
The liver lacks the enzyme thiophorase (also known as β-ketoacyl-CoA transferase).
Majority of phosphoglycerides are composed of ________.
(a) 2 FAs, 2 glycerol, a phosphate and a head alcohol
(b) 1 FA, glycerol, a phosphate and a head nitrogenous base
(c) 1 FA, glycerol, a phosphate and a head alcohol
(d) 3 FAs, 2 phosphates, glycerol and a head alcohol
(e) 2 Fatty acids (FAs), Glycerol, a phosphate and a head alcohol
(e) 2 Fatty acids (FAs), Glycerol, a phosphate and a head alcohol [Image]
The following pathways are important in RBCs energy metabolism except ________.
(a) glycolysis
(b) the TCA cycle and electron transport chain
(c) the phosphogluconate pathway
(d) 1,3-bisphosphoglycerate pathway
(e) Rapoport-Leubering pathway
(b) the TCA cycle and electron transport chain
No enzymatic steps in a hepatocyte would convert acetyl-CoA to ________.
(a) pyruvate
(b) CO2
(c) a fatty acid
(d) HMG-CoA
(e) malonyl-CoA
(a) pyruvate
Which of the following is not correct regarding 2,3-biphosphoglycerate?
(a) Its concentration increases during adaptation to high altitude (acclimatization).
(b) It is a positive allosteric effector of the oxygen affinity of haemoglobin.
(c) It decreases the oxygen affinity of deoxyhaemoglobin.
(d) It has a less effect on HbF than on HbA.
(b) It is a positive allosteric effector of the oxygen affinity of haemoglobin.
Which of the following is true about HbA1c?
(a) It is separated from free Hb by cation-exchange chromatography.
(b) It is formed by a condensation reaction between glucose and the N-end of the alpha chain of Hb.
(c) It is formed by a condensation reaction between glucose and a residue of Hb.
(d) It is a glycated Hb.
(e) It is a glycosylated hemoglobin (Hb).
(d) It is a glycated Hb.
The characteristic color of urine in a patient suffering from phenylketonuria is due to the compound ________.
(a) phenyllactate
(b) phenylpyruvate
(c) phenylmercapturic acid
(d) phenylacetylglutamine
(e) phenylacetylglycine
(b) phenylpyruvate
During adaptation to high altitude, a ________ replaces a kinase in the cytosol of a RBC.
(a) transferase
(b) mutase
(c) mutase and a phosphatase
(d) phosphatase
(e) oxidase
(b) mutase
Which of the following metabolic pathways is exclusive to the liver?
(a) glycolysis
(b) gluconeogenesis
(c) glycogen metabolism
(d) amino acid metabolism
(e) fatty acid metabolism
(b) gluconeogenesis
The adipose tissue (AT) carries out the following function except:
(a) Triacylglycerol (TG) synthesis
(b) Lipolysis
(c) TG breakdown
(d) Esterification
(e) None the above
(e) None the above
Which of the following factors does not affect which energy system operates during exercise?
(a) Intensity
(b) Whether or not oxygen is present
(c) Duration
(d) The depletion of chemical and food fuels during exercise
(e) None of the above
(e) None of the above
