FUN Quiz 4 Flashcards
What are the two types or modes of metabolism?
Catabolic reactions
Anabolic reactions
Briefly describe the two modes of metabolism
Catabolic reactions involve the breakdown of organic matter, ultimately to produce energy by cellular respiration
Anabolic reactions involve the synthesis of complex compounds essential for life but consume energy
What are the 3 steps of anabolism?
- Forming Precursors
- Form complex molecules from simple precursors
- Linking of complex molecules
Examples include proteins, RNA/DNA, lipids, and carbs
What are the 3 steps of catabolism?
- Hydrolysis of complex molecules into monomers
- Conversion of monomers into acetyl CoA
- Oxidation of acetyl CoA followed by oxidative phosphorylation
What are the energy sources of metabolism and where do they come from?
ATP, NADH, NADPH, FADH2
They come from catabolic reactions
How does ATP release energy
Cleavage of ATP into ADP
Describe how the change in free energy predicts whether a reaction is favorable or not
If G is positive => unfavorable => endergonic
If G is negative => favorable => exergonic
What is the first step in glucose metabolism? Is it endergonic or exergonic?
Glucose + ATP -> Glucose-6-Phosphate + ADP
Enzyme used is Glucokinase/Hexokinase
Exergonic
What are the main coenzymes in cellular respiration?
NAD+ and FAD
Differentiate between oxidation and reduction
Oxidation is the gain of oxygen or the loss of electrons or H+
Reduction is the loss of oxygen or the loss of electrons or H+
What is the final electron acceptor in cellular respiration?
O2
What is the role of O2 in the electron transport chain
It is the final acceptor of electrons. NADH and FADH2 are reoxidized.
The TCA cycle is amphibolic. Define Amphibolic
Involved in anabolic and catabolic pathways
Define Gluconeogenesis
Synthesis of glucose from non-carbohydrate precursors.
What are the mechanisms of regulating energy metabolism? Give examples
- Feedback inhibition: NADH can inhibit enzymes involved in it’s production and NAD+ can stimulate
- Phosphorylation/dephosphorylation: Hormones such as insulin and glucagon
- Availability of substrates: Availability of oxaloacetate regulates citrate synthase activity.
- Oxygen availability: Hypoxia - Failure of oxidative phosphorylation
Briefly explain inborn Errors of Metabolism and their consequences
A mutation in a gene can cause the formation of a defective protein with impaired function causing disease/disorder.
In addition to that, these errors can form an alternative product. This would cause:
- Accumulation of substrate
- Deficiency of product
- Diversion to alternate product
How does glucose enter the cell? Describe the energy consumption or lack there of when glucose is transported into the cell
Glucose is carried into cells by one of two active transport mechanisms:
- Facilitated diffusion through GLUT transport proteins in cell membranes
- Na+-dependent co-transport: SGLT
What is meant by the iOS forms of GLUT transport?
GLUT transporters are tissue specific.
Once glucose is in the cell, how is it prevented from leaving?
Once inside, glucose is trapped by phosphorylation converting it to glucose-6-phosphate
Phosphorylation in the first step of glycolysis is carried out by which enzyme(s)?
Hexokinase and Glucokinase
Differentiate between Hexokinase and Glucokinase and describe their regulation
Hexokinase is present in most cells types. Hexokinase has a low Km => high affinity for glucose even at low concentrations as well as a low Vmax => limited capacity. It is regulated allosterically by its product (Glucose-6-P) which inhibits it
Glucokinase is present in liver parenchyma cells and pancreatic islet cells. Glucokinase has a high Km => only kicks in at high glucose concentrations as well as a high Vmax => high capacity allowing it to handle high glucose levels occurring after digesting food. Glucokinase also helps Beta-cells in the pancreas to sense rising glucose concentrations leading to insulin release and allows the liver to break down the high concentration of glucose in the portal circulation after a meal. It is regulated by it’s substrate, glucose, as well as being inhibited by glucose-6-phosphate (it’s product)
What is the end product of glycolysis?
2x Pyruvate, 2 NADH, 4 ATP (2 net)
How much ATP is produced as a result of glycolysis and how much ATP is required for glycolysis to take place?
4 ATP is produced and 2 is required for it to take place
What is the rate-limiting step in glycolysis?
Phosphofructokinase 1 is the rate-limiting step
How is the process of glycolysis regulated?
- Feedback and allosteric inhibition of enzymes: PFK1 (phosphofructokinase 1) is inhibited by ATP; Glucokinase is inhibited by fructose-6-Phosphate
- Hormonal regulation: Insulin and Glucagon control PFK 2 activity
What is more efficient; Aerobic or anaerobic metabolism? Why?
Aerobic metabolism is more efficient as it produced much more ATP
What are the two ways that ATP is produced?
- Directly through substrate-level phosphorylation (glycolysis)
- Indirectly through oxidative phosphorylation (electron transport chain)
How much NET ATP is produced from:
- Glycolysis
- 1 NADH+H+
- 1 FADH2
- Aerobic Respiration
- Anaerobic Respiration
2 3 2 38 2
What are the products of glycolysis in aerobic and anaerobic glycolysis?
Aerobic: 2 Pyruvate, 2 ATP, 2 NADH
Anaerobic: 2 Pyruvate, 2 ATP
Why does Anaerobic glycolysis not form any NADH?
Anaerobic glycolysis does not undergo oxidative phosphorylation and hence the NAD+ is regenerated at the end of glycolysis
Do humans perform anaerobic respiration? Is it normal? What are the consequences?
Yes
Yes
Lactic acid accumulation occurs during vigorous and extended exercise. Excessive buildup can cause lactic acidosis which can cause several CVDs (Cardiovascular diseases)
Where do the following occur?
- Glycolysis
- TCA cycle
- Link Reaction
- ETC (electron transport chain)
Cytoplasm
Matrix (Mitochondria)
Matrix (Mitochondria)
Cristae
The mitochondrial membrane is impermeable to charged molecules. How does pyruvate enter the mitochondria?
Pyruvate Dehydrogenase is a specific Pyruvate Transporter that exists in the inner mitochondrial membrane.
Describe the link reaction. Is it reversible or irreversible?
Occurs in the matrix. Pyruvate Dehydrogenase Complex is a multi-enzyme complex that converts pyruvate into Acetyl-CoA:
Pyruvate + NAD+ + CoA -> Acetyl CoA + NADH + CO2
It is an irreversible reaction
Is it possible to form glucose from Acetyl CoA
Nope lmao
What are the metabolic fates of Pyruvate?
- Conversion to Acetyl-CoA which can either enter the TCA cycle or serve as a precursor for Fatty-acid Synthesis
- Conversion to Oxaloacetate which can enter the TCA cycle or serve as a precursor for Gluconeogenesis
- Reduction to Ethanol (No need to include)
Give 2 Clinical problems associated with Pyruvate Dehydrogenase
- Pyruvate Dehydrogenase Deficiency: Pyruvate converted to lactic acid instead of Acetyl-CoA due to a genetic defect
- Arsenic Poisoning: Inhibits pyruvate dehydrogenase
- Vitamin Deficiencies: Deficiency in vitamins B1,2,3, and/or 5 will impair pyruvate dehydrogenase function
Describe the drug discovery process
Conduct the basic and relevant research for the drug
Customize and synthesize the drug
Screen the drug for it’s efficacy, toxicity, and in vivo efficacy
Explain how diseases are characterized
Diseases are characterized based on how it defines the target disease
Identify commercial factors involved in drug development
Market research is involved in drug development as pharmaceutical companies are for-profit businesses which focus on getting enough market support
What are orphan drugs
A pharmaceutical agent developed to treat medical conditions which, because they are so rare, would not be profitable to produce without government assistance
Distinguish between hit compounds, lead compounds, and candidate compounds
Hit compound: A compound from high-throughput screen with activity on the target
Lead Compound: The most promising hit compound selected for further work. Derivatives of these compounds can be screened to be optimized
Candidate compound: Best compound selected for clinical development
Define QALY
QALY is a key pharmacoeconomic measure but not the only one
1 QALY is a year of life with perfect health
What is pharmacoeconomics mainly focused on?
Pharmacoeconomics looks at the value of pharmaceuticals and total cost
Define Drug Toxicity
A drug where it’s specific target produces toxic effects
What are unwanted effects for OPIATES and ANTI-HISTAMINES?
When using opiates to treat pain, constipation is an unwanted effect
When using anti-histamines to treat allergies, drowsiness is an unwanted effect
Explain the difference in detecting predictable/pharmacological adverse effects vs. unpredictable/non-pharmacological adverse effects?
Predictable: These effects occur when you see excessive pharmacological action, which is seen with a class of drugs
Unpredictable: These effects are seen with only a specific member of a drug class
Explain how idiosyncratic/dose-independent adverse effects are shown
These effects will only be shown in drugs that are dose-dependent and can be immunological. These effects can occur due to polymorphism
Give 1 example of a drug that expresses the following effects:
- Predictable/pharmacological adverse effects
- Un-predicatable/nonpharmacological adverse effects
- Idiosyncratic/dose-independent effects
- Thalidomide
- Diethylstilbestrol or paracetamol
- Coumarin
Give 4 types of drugs that show predictable adverse effects
Antibiotics
Anticoagulants
Opioid Analgesia
Insulin
What are the main sources of adverse drug effects?
- Active pharmaceutical ingredients (toxicity is due to metabolites and species-specific effect)
- Contaminants
- Excipients
Why does coumarin produce dose-independent effects in rats?
Toxicity is dose dependent and coumarin is shown to produce high levels of hepatotoxicity in rats
Define Pharmacovigilance
This occurs when patients undergoing treatment provide a large source of information on adverse effects
Explain contaminants and how its effects degrade over time
Contaminants are very pure forms of active pharmaceutical ingredients that may be produced by by-products from drug synthesis. This causes it to degrade based on storage condition which has two major effects:
- Reduced dose of API
- Increased presence of toxic by-products
Define Bioequivalence
Absence of significant difference in the rate and extend to which the active ingredient or moiety in pharmaceutical equivalents or alternatives becomes available at the site of drug action when administered at the same molar dose under similar conditions in an appropriately designed study
How is bioequivalence measured?
Measured by comparing Cmax and AUC between two products
Explain the concept of risk management plans. Give one example of a drug being used in the plan?
Risk management plans are used to allow the use of a drug but reduce the risk of an adverse effect
- Natalizumab
- Thalidomide
Explain the types of studies used in Preclinical, Clinical, and Post-market Study Designs
Preclinical: Discovery followed by preclinical studies are used. The patent is then granted to allow the investigation of new drugs
Clinical: Phase 1-4 are included. New drug applications are assessed in phase 4
Post Market: Post market studies are conducted. When the patent expires, generics are branded
Describe the drug discovery process:
Basic research is conducted, followed by customizing and synthesizing the drugs. It is then screened for its efficacy, toxicity, and in vivo efficacy
Explain how diseases are characterized
Diseases are characterized based on how it defines the target disease
Identify commercial factors involved in drug development
Market research is involved in drug development because pharmaceutical companies are for-profit businesses and focus on getting enough market support
What are the stages in clinical development?
Phases 0-IV
How are the stages of clinical development classified in the design of clinical studies?
The phases are classified by function
In Phase 0 studies, describe the doses used, the sample size, and its importance in clinical studies
The doses used has no biological effect. There are a small number of volunteers. Phase 0 studies are used to assess pharmacokinetics/pharmacodynamics and is used to identify potential candidates for clinical development
What’s another name for Phase 0 studies?
Microdosing studies
When Identifying volunteers for Phase 1 studies, what are the requirements?
Healthy male volunteers
Why are females not included in phase 1 studies?
Females can’t take part because they need to undergo developmental toxicology studies first
What is measured and assessed in Phase 1 studies?
Tolerability through measuring drug concentrations. The results from this can assess pharmacokinetics, pharmacodynamics, metabolism, and potency
What type of patients are recruited for Phase 2 studies?
Patients with the appropriate disease, all gender, generally older population
Differentiate between the two types of Phase 2 studies
Phase 2a repeats much of phase 1
Phase 2b monitors the surrogate endpoint (measure of effect of specific treatment that correlates to a clinical endpoint), where the estimate dose is required
What is a surrogate endpoint? Where is it used in clinical studies?
It is a measure of the effect of a specific treatment that correlated to a clinical endpoint. Used in phase 2b
In phase 3 studies, describe its function and sample size. What can be concluded from Phase 3?
Therapeutic confirmation is the main focus of Phase 3 studies. Large patient populations are assessed.
Phase 3 establishes efficacy, safety, the dose-response relationship, and the benefit-risk relationship
What kinds of studies are used in Phase 3 studies?
Pivotal studies
Explain the function and conclusions that are drawn from phase 4 studies
Function: Determine therapeutic use of drugs and studies approved drugs
Conclusions after approval: Refine benefit/risk, pharmoeconomics, adverse effects (i.e. low incidence, long term use)
What are the different types of names drugs can have?
Chemical name, drug name, brand name, generic names, trade names
What are the two trade names for the drug Sildenafil?
Viagra and Revatio
Define drug distribution
Drug distribution is the process by which a drug reversible leaves the blood stream and enters the extracellular fluid and/or cells of the tissue (intracellular fluid)
Define Volume of Distribution Vd, what it indicates, and what it determines
Definition: Theoretical volume of fluid a drug would occupy if the total amount of drug in the body was in solution at the same concentration as in the plasma.
Indication: Measure of the extent of distribution of a drug from plasma into tissues
Determines:
- The relationship between plasma concentration and total amount of drug in the body
- The amount of a drug that has to be administered in order to produce a particular plasma concentration
Define Loading Dose and give it’s function or use case
Loading dose is a high dose a drug given to reach therapeutic levels faster
Compare the clinical usefulness of Vd for:
Large Vd drug
Low Vd drug
Vd reflects the size of distribution space. A large Vd indicated that we will need a higher dose to load and a small Vd needs a lower dose to load.
How is the loading dose calculated?
LD = Vd x Desired plasma concentration
What are the 2 processes the body uses for drug elimination?
Metabolism and Excretion
In Drug elimination, metabolism usually converts ___ into ___
Lipid soluble chemical
Water soluble species
Drug Metabolism primarily occurs in the _____ and involves two types which are ______ that deals with the ____, ____, and ____ of drugs as well as ____ which involved ____
Liver Phase 1 Oxidation Reduction Hydrolysis Phase 2 Conjugation
Outline the types of excretion that the body utilizes for eliminating drugs
- Renal: Fluids (Urine, sweat, tears, milk)
- Biliary/Gastrointestinal: Solids (Feces, hair)
- Pulmonary: Gases (Expired air)
- Mammary
- Salivary, Skin, and Hair
Can excretion of an already metabolized drug occur?
Yes
What are the 3 renal processes accounting for renal drug excretion?
Glomerular filtration
Active tubular secretion
Reabsorption
What is the main importance of Urinary/Renal Excretion
Elimination of low molecular weight polar substances
What is the main function of glomerular filtration
Only allows molecules under 20 kDa to enter the filtrate in the nephron
Why can’t protein-bound drugs not enter the filtrate?
Many drugs bind to plasma proteins while circulating which increase their molecular weight hence preventing them from entering the filtrate of the nephron
Explain the process of Urinary Excretion
Urinary excretion is crucial for low molecular weight polar substances. It involves 3 main processes:
1. Glomerular Filtration: Filters molecules in the blood only allowing for molecules less than 20 kDa to enter the filtrate of the nephron. Protein bound drugs are not filtered in.
- Tubular secretion: Active carrier mediated elimination involving secretory mechanisms for both acidic and basic compounds against their concentration gradient
- Reabsorption: Passive re-absorption of lipid-soluble un-ionized drug.
Lipid soluble drugs are more likely to be reabsorbed and hence last longer in the body whereas water-soluble drugs are more likely to be excreted in urine.
How are lipid-soluble, ionized, and high molecular weight drugs excreted?
Biliary/Gastrointestinal Excretion
Explain the process of Biliary Excretion and the concept of Entero-hepatic Circulation
Hepatocytes in the liver uptake lipid-soluble drugs, metabolize them, and excrete them into bile. This process does not sufficiently excrete the drug as it is then reabsorbed through the Entero-hepatic Circulation once the drug is released into the intestine through the bile duct. Here, drug conjugates are Hydrolyzed mainly by bacteria in the lower intestine. This causes the active drug to be released once more.
What is the most signification route of excretion for Glucoronide Conjugated
Bile Excretion
Briefly explain Pulmonary Excretion of drugs
Excretion occurs via the lungs and breath. It is a significant route for some volatile molecules such as anesthetics and ethanol
Compare concentration of molecules in breast milk to that off free concentration in maternal blood
Concentration in milk is similar to the free concentration in maternal blood
What is the clinical relevance for the effect of a drug on a breast-feeding baby? Give one example
Babies should not be exposed to the same levels as mother and hence the drugs the mother takes should be at a safe concentration for the baby.
Tetracyclines for example when incorporated into the baby’s teeth will weaken them
Most drugs are eliminated through which order process
First
Compare and contrast First order and zero order kinetics giving one example for each
First order elimination is where the amount of drug eliminated is directly proportional to the serum (blood plasma) concentration. The fraction of the drug eliminated and not the amount of the drug eliminated is constant. Example: Glomerular Function
Zero Order Kinetics: Elimination occurs at a fixed maximum rate that is independent of drug concentration. Example: metabolism of ethanol and protein mediated reaction
What is meant by the half life and which order of elimination kinetics does it follow?
The half life is the time for plasma concentration of a drug to fall by 50%. It follows the 1st order elimination kinetics
What is the plasma half-life determined by?
- Activity of metabolizing enzymes or excretion mechanism clearance
- Distribution of drug between blood into tissues => High Vd (drugs mainly located in tissue) results in prolonged half life
What is the general rule for Plasma Half life when administering surgery?
4 or 5 half lives
Briefly explain what is meant by Steady-State of a drug as well as it’s aim
With infusion and first order elimination, at a certain point in therapy, the amount of drug administered during a dosing interval exactly replaces the amount of drug excreted.
When this equilibrium occurs, (rate in = rate out), steady state is achieved
The aim is to maintain the steady-state concentration of a drug within therapeutic range
Compare between Thalidomide and Diethylstilbestrol in terms of its functions. Why are they withdrawn?
Thalidomide was approved as an immunomodulator to treat leprosy, host diseases in children, and HIV mouth ulcers. Diethylstilbestrol is a non-steroidal estrogen that was approved by FDA to prevent miscarriage, estrogen deficient states, and post-coital contraceptives. It was withdrawn due to tetragenic effects.
Briefly describe the synthesis of paracetamol
- Requires replenishing glutathione (GSH) which is not orally active
- N-Acetylcysteine is orally active and converted to GSH
- GSH is the orally active form of GSH
Which clinical study design phase allows for more data to be collected? Why?
Phase 4 studies allow for more data to be collected because there’s an increase in patient population and allows for a better estimate of low incidence adverse effects
How is bio equivalence measured and defined?
- Measured by comparing Cmax and AUC between two products
- Defined as CI of test within 0.8 and 1.25 of reference
What are the two requirements that must be met in forced degradation studies
- Extreme conditions must be met
2. Identify Degredation by-products and test them for toxicity
Explain the difference between EMA risk management plans and FDA risk evaluation/mitigation strategies
EMA risk management plans use summary of product characteristics to communication precautions with drugs
FDA Risk evaluation and mitigation strategies are used for specific company communication plans
Define the summary of product characteristics
Source of all information regarding the use of drugs and adverse effects
Which phase in a clinical study does a drug get approved for use?
Phase 3
Define the criteria drug companies use to choose patients in Phase 3 studies
Drug companies choose patients most likely to respond to drugs. Patients must have a clearly defined diagnosis with a disease in early stages, no other diseases, no other medications, and over 18 years of age
Give 3 population groups that require specific investigations
Children Women Pregnant women Elder Ethnic groups Patients with other diseases Patients on other medications
What are the 4 causes that differentiate between populations?
Different pharmacokinetics (PK)
Different rate of clearance
Different metabolism
Different pharmacodynamics
Briefly describe the crusade study
30k patients were given anti-thrombotic and 42% received excessive doses. It was concluded that excessive dosing was associated with a higher risk of major bleeds
What four factors in the crusade study were predicted when patients were excessively dosed
Older age
Gender (female)
Renal insufficiency
Low body weight
What are three differences in drug effects amongst the elderly population?
Changes in body composition
Changes in clearance
Changes in metabolism
Identify how changes in body composition differentiate the elderly from other special population
The elderly have decreased lean mass and increased fat content. They also have decreased serum albumin and water content
Why does the rate of clearance distinguish the elderly population from other special populations?
The elderly have decreased renal function
Explain the pharmacokinetic changes that occur in the elderly population
Elimination half-life is increased and the volume of lipid-soluble drugs being distributed increases
Explain the pharmacodynamic changes that occur in the elderly population
There is an increase in the sensitivity to CNS depressants and adverse effects of drugs. This is often due to impaired compensatory mechanisms
What are the factors that influence the different effects drugs have on females vs. males
The effects drugs have on females are different due to the effect of hormones on drug metabolism and changes in PK parameters due to an increased % body fat in women
Which special population is excluded from P3 studies and why?
Pregnant women due to the problems that may occur during pregnancy such as:
- Adverse effects on fetus
- Adverse effects on pregnancy
- Changes in PK parameters
Explain the different types of pregnancy categories established by the FDA
A: no risk from clinical studies during pregnancy
B: No clinical studies but no risk in animal studies
C: Adverse effects in animals + no clinical studies or no studies at all
D: Risk in clinical studies but some benefits
X: Refrained during pregnancy because the studies indicate risk
Explain how drug clearance develop in children starting from neonates until adult life
Neonate drug clearance is less than adults but by 1 years old, clearance rates increase higher than that of adults. Puberty causes the clearance rates to fall and equal adult levels
How do drug responses distinguish ethnic groups?
Drug responses show genetic variability, which is often ethnic-based. As a result, ethnic groups need adjustment of dose or are at greater risk to adverse effects
What are the two diseases that cause metabolism/clearance problems?
- Liver disease
2. Renal disease
What is Mycophenolate?
An immunosuppressant used to prevent rejection during a kidney transplant
What is the major site of drug metabolism?
Liver
How do kidney diseases affect drug action?
Kidney diseases reduce kidney function,causing drug elimination to reduce and causes toxicity. This is because drugs are eliminated in urine
What liver enzyme is crucial in Phase 1 metabolism?
CYP1A2
How can drug-drug interactions be identified?
Adverse reaction reporting
How do drugs lose its effect?
When it is bound to a plasma protein
Define Personalized medicine
Use of a medicine and dosage that is tailored for the specific patient rather than the population as a whole
Why is precision medicine important?
Precision medicine is important to improve outcomes for all patients, as the current model is used on a one-dose-fits-all basis. It allows drugs that failed at population levels to be revived for use in sensitive populations
Pharmacogenetics Learning Outcome: Describe how the response to a drug is affected by the genetic variation in drug metabolic pathways.
In general, individuals will show a range of responses to a specific administered drug dose. For example, some individuals may have a fully positive response while others may have verry little to no positive response. We need to be able to identify the groups of people who would have adverse reactions to these doses.
Responses are very complex since they are influenced by both genetic (as coded for by DNA) and environmental factors (age, diet, organ function, underlying disease, concomitant therapy, drug interactions etc).
It is important to note however that not all genetic risk factors are clinically relevant. We only look for large or noticeable odds ratios.
An example which shows this is the prescription of mercaptopurine (purinethol) and azathioprine to reduce white blood cell division and dampens the inflammatory response and cell division by inhibiting DNA replication. It is commonly used to treat conditions with overreactive immune responses, for example leukaemia, inflammatory. Bowel disease, organ transplants and rheumatoid arthritis. If too high of a dosage is prescribed to a patient, they may experience myelosuppression which may lead to an infection due to a decrease in the number of white blood cells or even anaemia due to a decrease in the red blood cell level.
The azathioprine metabolizes into 6-mercatopurine (6-MP) which is an active metabolite which then further metabolizes into 2 inactive metabolites which are:
1. Oxidized metabolites by the enzyme xanthine oxidase or XO
2. 6-methyl mercaptopurine but the enzyme thiopurine methyl transferase or TPMT
The active metabolite can then further breakdown into 6-thioguanine nucleotides (6-TGN) which is the major metabolite responsible for activity. When incorporated into DNA, there is the inhibition of cell division.
NOTE: As the activity of the enzymes increase, so does the drug activity level; the converse is also true.
For the TMPT, there are different genetic variants and the genotype would influence the enzymatic activity. There are 3 genotypes:
1. Homozygote l/l or v/v (low or slow activity) ——— LEAST COMMON
2. Heterozygote l/h or wt/v (mid activity) —– [wt – wild type]
3. Homozygote h/h or wt/wt (high or fast activity) ——— MOST COMMON
The low activity genotype would usually struggle to metabolize the drug and hence there would be a high active metabolite level if a high dosage was given (myelosuppression). Therefore, a lower dosage would need to be prescribed for a similar effect of an individual with the h/h genotype.
Pharmacogenetics Learning Outcome: Describe how the response to a drug is affected by the genetic variation in drug targets.
An example which demonstrates this in the metabolism of warfarin. Warfarin is an anticoagulant which is used in the prevention of thrombosis and embolism. There is a narrow therapeutic range and as the dose increases, there may be a further risk of bleeding and haemorrhaging however with a decrease in the dosage, there is a risk of thrombosis or embolism. Further complications can be caused by diet, disease state and drug interactions. The dosing or warfarin is monitored via the international normalized ratio (INR) which monitors the clotting tendency of blood.
Warfarin is metabolized by the enzyme CYP2C9 which results in the formation of active warfarin. This inhibits vitamin k epoxide reductase or VKOR which causes a reduced rate of chemical reduction of vitamin K. This leads to the inhibition of carboxylation and the clotting pathway.
The genetic variation of the metaboliser (CYP2C9) accounts for approximately 6% of dose variability whereas, the variation of the VKORC1 or target can explain about 25%. There are 3 genotypes:
- A/A —– least common – would receive the lowest dosage of the drug
- A/B
- B/B —- most common – would receive the highest dosage of the drug
Hence, there was a development of a website which determines the correct dosage of the warfarin to be prescribed, taking both genetic and environmental factors into consideration.
What part of glucose metabolism involved the bulk of ATP production?
ETC: Electron transport chain
How many reactions are involved in the TCA cycle?
8
State the first step of the TCA cycle that occurs after glycolysis
The cycle starts with the condensation of Acetyl-CoA with oxaloacetate and ends with the regeneration of oxaloacetate.
How many carbons enter the TCA and what is the fate of these carbons?
2 Cs enter as acetyl CoA and leaves as 2 CO2
What is the rate limiting step of the TCA cycle?
The isocitrate dehydrogenase reaction is the rate limiting step in the TCA cycle
State the role of fumerase
Fumerase hydrates fumerate converting it to malate
What enzyme catalyzes the final reaction of the TCA cycle and what does it generate?
Malate dehydrogenase catalyses the final reaction of the TCA cycle generating oxaloacetate as well as reducing NAD+ into NADH + H+
What are the energy-producing molecules of the TCA? How many molecules of each are formed from 1 Acetyl-CoA that enters the cycle? What is the total potential ATP produced as a result?
The energy producing molecules are 3 NADH (9), 1 FADH2 (2), and 1 GTP (1).
How many electron pairs are transferred during the cycle? What molecules are they transferred to?
4 electron paris are transferred during the cycle. 3 pairs NAD+ and one pair to FAD
What is the ultimate fate of the electrons in the TCA cycle?
Ultimately, these will donate their electrons to the electron transport chain to make ATP.
During anaerobic metabolism, how many reactions are included in the TCA cycle?
There is no TCA cycle
What is the total amount of ATP produced during anaerobic respiration?
2 ATP
What is the total amount of ATP produced as a result of aerobic respiration per glucose molecule? Per pyruvate?
38
19
What are the three points where the TCA cycle is regulated?
Citrate synthase, Isocitrate dehydrogenase, and alpha-ketoglutarate dehydrogenase
What are the allosteric activators and inhibitors of the TCA cycle?
Allosteric activators: ADP and Ca2+
Allosteric inhibitors: ATP, GTP, NADH, and Succinyl-CoA
Briefly describe the 4 methods of regulation in the TCA with examples
Feedback inhibition (allosteric effectors): High NADH/NAD+ ratio where NADH inhibits and NAD+ stimulates. Another example is the ratio of ATP/ADP (energy ratio). ATP inhibits, ADP stimulates.
Phosphorylation/dephosphorylation: Pyruvate dehydrogenase regulation (phosphorylation is inactive and dephosphorylation is active). Prevents acetyl CoA from entering the TCA cycle
Availability of intermediates: Oxaloacetate affects the rate of citrate synthesis
Availability of Oxygen: Hypoxia is insufficient O2 and anoxia is lack of O2. O2 is the final acceptor of electrons. The most common cause of this is Ischemia which is the interruption of blood supply
What happens to the energy that is not converted to ATP during cellular respiration?
Energy not converted to ATP is used to transport Ca2+ and generate heat
Where does the TCA cycle occur?
In the mitochondrial matrix
What is the permeability of the outer membrane of the mitochondria?
Permeable to small molecules
What is the permeability of the inner membrane of the mitochondria?
It is impermeable to most ions, small molecules, and large molecules
State all reactions involved in the TCA cycle starting with the entry of Acetyl CoA.
There are 8 reactions involved in this cyclic pathway:
Oxaloacetate + acetyl CoA —> citrate enzyme: citrate synthase
Citrate ——> Isocitrate enzyme: aconitase
Isocitrate ——> alpha ketoglutarate enzyme: isocitrate dehydrogenase (RLS)
NAD+ ——> H + NADH
Alpha ketoglutarate ——> succinyl CoA + CO2 enzyme: Alpha - KGDH (alpha-ketogluterate dehydrogenase)
NAD+ ——> H + NADH
Succinyl CoA ——> succinate + Pi enzyme: succinate thiokinase
GDP +Pi ——> GTP
Succinate ——> Fumarate enzyme: succinate dehydrogenase
FAD ——> FADH2
Fumarate + H2O ——> malate enzyme: fumarase
Malate ——> oxaloacetate
enzyme: malate dehydrogenase
NAD+ ——> H + NADH
Where does the ETC occur?
This happens in the inner mitochondrial membrane or the cristae
Explain the passage of NADH from the cytosol into the mitochondrial membrane. Include the names of the shuttles.
Substrate shuttles, or transport proteins, permit the passage of specific molecules from the cytosol to the mitochondrial matrix.
The inner mitochondrial membrane lacks NADH transport proteins. Only electrons from the cytosolic NADH are transported into the mitochondrion.
Electrons from cytosolic NADH are transferred to an intermediate which crosses the mitochondrial membrane and then transfers back into mitochondrial NAD+ or FAD
Glycerol 3-phosphate shuttle transfers electrons to mitochondrial FAD
Malate-aspartame shuttle transfers electrons to mitochondrial NAD+.
How many H+s make up an ATP molecule, how many H+s are released from 1 NADH, and how much ATP is produced as a result of that?
4 H+ = 1 ATP
10 H+ = 2.5 ATP or 3
How many complexes and carriers are present in the ETC?
There are 4 complexes and 2 carriers in the ETC
When electrons ultimately combine with oxygen and Hydrogen, what is produced?
H2O
Name ETC Complexes I, III, and IV indicating their metallic components. State the significance of these metal ion.
All members of the chain except Coenzyme Q are large protein complexes coupled to metal ions in order to make them good electron carriers.
I- NADH Dehydrogenase or NADH-Q reductase or NADH-Ubiquinone Oxidoreductase: Fe-S
III- Cytochrome C reductase: Fe ion
IV- Cytochrome C oxidase: Copper and cytochrome
Name the 4 complexes of the ETC giving their role.
Complex I: NADH Dehydrogenase or NADH-Q reductase or NADH-Ubiquinone Oxidoreductase: Catalyzes the transfer of electrons from NADH to Co-enzyme Q
Complex II: Succinate Dehydrogenase: Transfers electrons from succinate to Co-enzyme Q
Complex III: Cytochrome C Reductase: Transfers electrons from ubiquinone to Cytochrome C
Complex IV: Cytochrome C oxidase: Transfers electrons from cytochrome C to O2
What is the free energy that is released as electrons used for?
It is used to pump protons across the membrane
Give a reason as to why NADH yields 3 ATP and FADH2 yields 2
The protein complexes are proton carriers that move protons across the inner membrane to create a gradient.
NADH has 3 sites where it’s electrons enter from => 3ATP
FADH2 has 2 sites => 2ATP
Discuss the Chemiosmotic theory and the coupling of electron transport to ATP synthesis.
Step 1: The sites of proton pumping are the 3 complexes of ETC. The inner mitochondrial membrane in impermeable to protons, this when protons are pumped out a gradient is created. This gradient is known as the proton motive force.
Step 2: H+ move back into the mitochondrial matrix through a specific protein channel, complex V: F0 unit. It is an integral membrane protein that contains the proton channel attached to the F1 unit which is the ATP synthase. H+ passage through F0 causes rotation which is a conformational change that generates energy allowing the binding of ADP + Pi into ATP.
ETC: Explain Uncoupling proteins with reference to Synthetic uncouplers
Uncoupling proteins create a proton leak allowing protons to renter the mitochondrial matrix without capturing ant of the energy as ATP. Energy is hence released as heat (thermogenesis). Thermogenin is responsible for heat production in brown adipose tissue which uses this respiratory energy in cold conditions. Humans have little brown fat except for neonates.
Synthetic uncouplers are compounds that increase permeability of the inner mitochondrial membrane. This leads to no ATP synthesis and energy is released as heat. An example of this is Aspirin which uncouple oxidative phosphorylation leading to a fever.
Explain mitochondrial diseases giving an example.
Mitochondrial diseases are defects that occur as a result of mutations in genes encoding various complexes of the ETC. This impairs oxidative phosphorylation in Parkinson’s disease Alzheimer as well as cardiomyopathies. This shows that these diseases tend to affect tissues with the highest energy demand such as the heart, muscle, nervous tissue, and eyes.
One prime example is Leber Hereditary Optic Neuropathy. These are point mutations in one of the subunits for NADH-Q reductase which causes a sudden onset of blindness in young adults. As a result, there is impaired electron flow through the respiratory chain leading to a severe decrease in ATP synthesis.
Explain the effects of vitamin deficiencies on the cellular respiration.
NAD relies on B3 and FAD relies on B2 for their synthesis. Deficiency leads to severe fatigue and complications affecting the cardiovascular, nervous, muscular, and gastrointestinal systems.
Define Gluconeogenesis
Synthesis of glucose from a non-carb origin
How is glucose stored in the body and for how long?
Glucose is stored in the body in the form of glycogen. It is stored in the body for 10-18 hours
What are the substrates for Gluconeogenesis?
Lactate, Glycerol, and amino acids.
Briefly outline Gluconeogenesis with the substrate lactate
When lactate is produced from pyruvate in anaerobic metabolism, it is then metabolized in the liver back into glucose.
Explain Gluconeogenesis with glycerol as the substrate
In fasting, glycerol is released from adipose tissue into the blood by hydrolysis of triglycerides. Glycerol kinase catalyzes the glycerol to form glycerol phosphate consuming 1 ATP molecule. Glycerol phosphate is then oxidized into dihydroxyacetone with is then converted into G3P in glycolysis to ultimately form glucose.
Explain the role of Acetyl CoA in Gluconeogenesis regulation
Acetyl CoA is generated from the breakdown of fatty acids but is not a substrate for Gluconeogenesis. Triglyceride breakdown produces increased glycerol and Acetyl CoA. High levels of acetyl CoA indicates that energy needs are met and hence activates pyruvate carboxylate which stimulates Gluconeogenesis and inhibits glycolysis
Briefly state the role of AMP in gluconeogenesis regulation.
high levels of AMP indicate that energy needs are not met and hence it inhibits fructose 1,6 Bisphosphatase => inhibiting gluconeogenesis and consequently activating phosphofructokinase 1 which activates glycolysis.
Explain gluconeogenesis with amino acids as the substrate
Amino acids converted to TCA intermediates via the TCA cycle eventually become oxaloacetate which is a direct precursor of PEP which then undergoes gluconeogenesis to become glucose.
Specific enzymes bypass the irreversible reactions of glycolysis. What are they? What steps are irreversible? And how is each of these reactions bypassed in gluconeogenesis?
- Dephosphorylation of G6P by Hexokinase/Glucokinase which affects the reaction where Glucose becomes glucose-6-phosphate. In gluconeogenesis it is bypassed by Glucose-6-phosphatase in the ERs of the liver and kidney which releases the phosphate. This also requires glucose-6-phosphate translocations which transports G6P to the ER.
- Dephosphorylation of fructose-1,6-bisphosphate by phosphofructokinase which affects the reaction where fructose-6-phosphate becomes fructose-1,6-bisphosphate. In gluconeogenesis, it is bypassed by Fructose 1,6 bisphosphatase which releases the phosphate group.
- Carboxylation of Pyruvate by pyruvate kinase which affects the reaction where phosphoenolpyruvate (PEP) becomes pyruvate. In gluconeogenesis, pyruvate carboxylate catalyzes the reaction forming oxaloacetate from pyruvate and then PEP carboxykinase produces PEP from oxaloacetate which is then able to produce glucose.
What are the effects of the presence of the hormones glucagon and insulin on the rate of glycolysis and gluconeogenesis?
Glucagon increases rate of gluconeogenesis
Insulin increases the rate of glycolysis
What are the entry points of gluconeogenesis substrates?
Glycerol enters the cycle where dihydroxyacetone becomes G-3-P
Lactate enters the cycle through pyruvate
Amino acids enter the cycle through oxaloacetate
Explain, without going into detail, the Pentose Phosphate Pathway.
The pentose phosphate pathway is an anabolic process which generates NADPH and 5-carbon sugars for bio synthetic processes. It produces the majority of the body’s NADPH from its oxidative reactions. It is divided into two phases where the first phase is the oxidative phase responsible for NADPH production and the second phase is the cyclical phase responsible for 5-carbon sugar production.
During the oxidative phase, there are 2 irreversible reactions where overall, 1 molecule of glucose-6-P forms ribulose-5-P, CO2 and NADPH. This reaction is catalyzed by glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconolactone hydrolase.
This is then followed by a series of reversible non-oxidative reactions that form 3,4,5,6, and 7 carbon sugars (Cyclical phase).
What is the main source of the ATP and NADH that is required for gluconeogenesis?
Fatty acid oxidation
Explain the role of NADPH along with the regulation of the pentose phosphate pathway.
NADPH functions as a biochemical reductant used in fatty acid synthesis as well as steroid synthesis and antioxidant reactions.
Rate and direction of reversible reactions depend on supply and demand of intermediates. It is regulated mainly at glucose-6-P dehydrogenase reaction which is the rate-limiting-step. Insulin increases G6PD gene expression and hence pathway activity increases.
What are alpha-keto acids
They are ketogenic amino acids without an amino group
State the synthesis of amino acid biosynthesis from alpha-keto acids
Ketogenic amino acids can be deaminated to produce alpha keto acids
What is glucose in breakdown and what is ketogenic breakdown?
Glucose is breakdown yields TCA cycle intermediates which can be used to make glucose.
Ketogenic breakdown yields Acetyl CoA
Outline the basics of nucleotide biosynthesis stating their common intermediates
Purine nucleotides are involved in de novo biosynthesis and in salvage or the reusing purine bases. The common intermediate between ATP and GTP synthesis in this case is IMP
Pyrimidine nucleotides are mainly produced by de novo synthesis with UMP as the common intermediate in DTMP synthesis
Outline nucleotide degredation as well as their clinical relevance
Pyrimidines are broken down to simple carbon skeletons and degraded. Many chemotherapy drugs act by inhibiting DTMP synthesis which prevents cell division by inhibiting DNA replication
Purines are either salvaged or degraded by being broken down into Uric acid to be excreted. Excessive breakdown of purine bases can lead to Gout which is an excess of uric acid which precipitate as crystals causing inflammation of joints and kidneys with severe pain.
Giving 2 examples state the biosynthesis of physiologically active amines
GABA and histamine are all amino acid derivatives.
Histidine is decarboxylated by Histidine decarboxylate to form histamine
Glutamate is decarboxylated to gamma-aminobutyric acid by glutamate decarboxylase
Define Isoenzymes and Isoforms
Isoenzymes are enzymes of different molecular form but catalyze the same reaction
Isoforms are forms of enzymes created through posttranslational modifications of enzyme molecules
What is the relationship between onset and severity of IEMS
Errors in metabolism tend to be more severe on early onset and less severe when shown later
What is a prime example of a newborn screen test and when is it administered? Why is it administered?
Heel prick test administered at 3-5 days old. It allows for early detection before clinical signs or symptoms which allows for early treatment => better clinical outcomes
Give the types of disorders that newborn screening tests for giving an example of each.
Disorders of carbohydrate metabolism: Galactosemia
Amino Acid Disorders: PKU, MSUD (Maple syrup urine disease), and Homocystinuria
Disorders of fatty acid oxidation: Medium chain acyl CoA dehydrogenase deficiency (MCADD)
Organic Acidurias: Glutaric Aciduria Type 1 (GA1)
What are the classifications of inborn errors of metabolism? Give a brief description of each along with an example
Group 1: Disorders causing intoxication: Leads to progressive accumulation of toxic compounds e.g. PKU, MSUD, Organic Acidurias
Group 2: Disorders of energy metabolism: IEM of intermediary metabolism: IEM of intermediary metabolism, symptoms due in part to energy deficiency e.g. mitochondrial or cytoplasmic energy defects
Group 3: Disorders involving complex molecules: Involved cellular organelles including diseases associated with disturbed synthesis or catabolism of complex molecules. E.g. Lysosomal storage disorders, peroxisomal disorders, and intracellular trafficking disorders.
What are the clinical similarities within disorders which give rise to intoxication?
- They do not interfere with embryo-fetal development
- Present after a symptom-free interval
- Clinical signs of intoxication may be Acute (vomiting, coma, liver failure) or chronic (failure to thrive, developmental delay etc…)
- Most are treatable with removal of toxin
Give 3 examples of Amino Acidopathies
PKU, Maple syrup urine disease, homocystinuria, Tyrosinemia
Discuss PKU as a disorder of amino acid metabolism
- PKU is an autosomal recessive disease involving a defect in the phenylalanine hydroxylase enzyme. This enzyme catalyzes the reaction that forms tyrosine from phenylalanine.
- It is diagnosed using the Newborn Screen (heel-prick) test
- Clinical symptoms if not detected involved irritability, vomiting, seizures, mental retardation, reduced melanin production (pale skin, fair hair, blue eyes), and frequently generalized eczema.
- It is treated with a diet low in phenylalanine supplemented with tyrosine.
Discuss Tyrosinemia Type I as a disorder of amino acid metabolism
It is the deficiency in fumarylacetoacetate hydrolase which is an enzyme that catalyzes the reaction that produces Fumerate and Acetoacetate from Fumarylacetoacetic acid.
This defect causes the accumulation of fumaryl acetoacetate and its metabolites in urine. An important one to note is succinylcholine acetone which is toxic.
Symptoms include cabbage-like odor, liver failure, and renal tubular acidoses
Treatments involve a dietary restriction of phenylalanine and tyrosine as well as a drug called nitisinone. This drug inhibits 4-hydroxylphenylpyruvic acid oxidase earlier in the reaction hence preventing the formation of succinylacetone.
Is it common to have a drug that treats IEMs?
Nope
Discuss Alkaptonuria as a disorder of amino acid metabolism
Alkaptonuria involves the deficiency of homogentisic acid oxidase which causes the buildup of homogentisic acid oxidase.
Alkaptonuria is characterized by dark urine and pigmentation of ears and eyes called Onchronosis
Discuss Maple Syrup Urine Disease as a disorder of amino acid metabolism
It is a defect in the metabolism of leucine, isoleucine, and valine. This causes the buildup of alpha amino acids and their alpha-ketoanalogs in plasma and urine.
Symptoms include progressive lagarthy, weight loss, hypertonia, and hypotonia. Also a maple syrup odor to the urine
Treatment involves dietary restriction of branched chain amino acids
Define Renal Tubular Acidosis
Failure of the kidney to excrete acids into the urine which causes a person’s blood to remain too acidic
Define Lethargy
Lack of energy, fatigue. It is a pathological state of sleepiness, unresponsiveness, or inactivity.
Define Hypertonia
Condition where there is too much muscle tone making them stiff and difficult to move
State 3 disorders of amino acid metabolism
PKU, Maple syrup urine disease, Alkaptonuria, and Tyrosinemia Type I
State 2 disorders of amino acid transport
Homocystinuria (Cystinuria) and Lysinuric protein intolerance
Discuss Homocystinuria as a disorder of amino acid transport
It is a defect in cystathionine synthase which leads to the accumulation of homocysteine in urine. Methionine and metabolites are also elevated in the blood.
Symptoms include CVD, deep vein thrombosis, mental retardation, and osteoporosis
Amino acids can be moved using specific transport system. In this case, Cystinuria prevents the uptake of cystine leading to the precipitation of stones of cystine in the urinary tract. Accumulation of Orn, Arg, and Lys also occurs in the urine but plasma concentration of Cys, Orn, Arg, and Lys remains normal
Treatment involves increased fluid intake and alkalinisation of urine.
What is cystine composed of
it is a dimer of cysteine
Discuss Lysinuric Protein Intolerance as a disorder of amino acid transport.
It is a defect in the absorption of dibasic amino acids (Lys, Arg, and Orn) which impairs the function of the Urea Cycle and causes lysine deficiency.
Plasma concentrations of NH3 (ammonia) increases in the plasma while concentrations of Arg, Lys, Orn decrease. Concentration of these amino acids increase in the urine.
Symptoms include failure to thrive, poor appetite, renal failure, and osteoporosis.
It is treated through protein restriction with citrulline replacement to enhance urea.
Discuss Hyperammonemia
It is characterized by high levels of ammonia in the blood which is toxic to the CNS.
Ammonia intoxication leads to tremors, slurred speech, vomiting, cerebral edema, and blurred vision.
It is caused either by Acquired hyperammonia due to liver insufficiency or congenital hyperammonemia which is due to urea cycle disorders.
Discuss Organic Aciduria Type I as a disorder due to intoxication
Organic Aciduria is the accumulation of organic acids in blood an urine. Type I is a defect in the metabolism of lysine, hydroxylysine, and tryptophan due to deficiency in glutaryl CoA dehydrogenase.
This leads to harmful organic acids accumulation causing dystonia, dyskinesia, brain damage, and death
It is treated through dietary restriction of protein and Carnitine.
What is dystonia
It is a movement disorder in which a person’s muscles contract uncontrollably
What is Diskinesia
Refers to a category of movement disorders characterized by involuntary muscle movements
Discuss Medium Chain Acyl-Coenzyme A dehydrogenase deficiency (MCADD) as a disorder of lipid metabolism
It is a disorder of fatty acid oxidation due to impaired breakdown of medium chain fatty acids into acetyl CoA.
Symptoms include intolerance to fasting, hypoketotic hypoglycemia, liver dysfunction, lethargy, seizures, and coma.
MCAD is responsible for the dehydrogenation step of fatty acids with chain lengths between 6 and 12 carbons as they undergo beta-oxidation in the mitochondria. => every 2 carbon units yield acetyl-CoA and 1NADH and 1FADH2
When discussing disorders involved in energy metabolism, what are the types of mitochondrial and cytoplasmic defects.
Mitochondrial defects:
- Congenital lactic acidemias (Pyruvate dehydrogenase deficiency, pyruvate carboxylate deficiency, TCA cycle deficiencies)
- Respiratory chain disorders (ETC)
- Fatty acid oxidation and ketone body disorder
Cytoplasmic defects: Glycolysis, gluconeogenesis, glycogen metabolism
State 3 disorders of gluconeogenesis that are associated with hypoglycemia
Pyruvate carboxylase deficiency
Fructose bisphosphatase deficiency
PEP carboxykinase deficiency
What are the diagnosis or Pyruvate carboxylase deficiency and Fructose-1,6-bisphosphatase deficiency?
Increased lactate and Ketosis
Define Homoplasmy and Heteroplasmy with regards to mtDNA.
Most mtDNA mutations are of which type?
When do heteroplasmic mitochondrial disorders often show symptoms?
Homoplasmy is when all copies of mtDNA are identical
Heteroplasmy is the presence of a mixture of more than one type of mtDNA.
Most mtDNA mutations are heteroplasmic
Symptoms of heteroplasmic mitochondrial disorders frequently do not appear until adulthood as many cell divisions are required for the cell to receive enough mitochondria containing mutant alleles to cause symptoms
What type of disease is pyruvate dehydrogenase complex deficiency? What does this deficiency cause? What is it’s diagnosis?
This disease is a mitochondrial disease that prevents the catalysis of Acetyl CoA causing increased lactate production. The diagnosis is increased plasma lactate.
With regards to the mitochondrial respiratory chain, where is gene expression originated from? Mitochondrial or nuclear?
Gene expression is mitochondrial and nuclear
With regards to the mitochondrial respiratory chain, are the complexes composed of a single polypeptide or multiple polypeptide chains?
Multiple
Discuss Glycogen storage disorders stating 3 examples along with a basic overview of the enzyme involved.
Glycogen storage disorders involve the abnormal synthesis or degradation of glycogen due to a defect in the genes coding for the enzymes involved in glycogen metabolism. They affect the liver and the muscle. Patients with these disorders often exhibit hypoglycemia along with muscle pain, cramps, and weakness
GSD V - McArdle Disease
Muscle glycogen phosphorylase deficiency
GSD I - Von Gierke’s Disease
Glucose-6-phosphatase deficiency causing the accumulation of glycolysis intermediates
GSD II - Pompe
Lysosomal alpha 1,4-glucosidase deficiency
What is hypoglycemia
Low blood sugar
What are the main glycogen stores in the body?
Liver
Muscle
In terms of disorders involving complex molecules, Give the general symptoms, treatments and types of disorders.
Symptoms: Permanent, progressive, independent of intercurrent events, unrelated to food intake (mention 2)
Treatment: Limited to enzyme replacement or bone marrow
Disorders:
Lysosomal storage disorders
Peroxisomal disorders
What are the two categories of lysosomal storage disorders
Sphingolipidoses, Mucopolysaccharidosis
What organelle is involved in the breakdown of very long and branched fatty acid chains generating hydrogen peroxide?
Peroxisomes
Briefly outline Sphingolipidoses
It is a lysosomal lipid storage disease that involves a defect in the degradation of sphingolipids hence accumulating sphingolipids
Easy no?
Briefly outline Mucopolysaccharidoses
It is a deficiency in lysosomal enzymes involved in the breakdown of carbohydrate molecules (most notably glycosaminoglycans)
Briefly outline peroxisomal disorders
It is a defect in peroxisomal assembly or synthesis => failure to make functioning peroxisomes. This leads to the accumulation of VLCFA and Phytanate
What organelle is involved in protein glycosylation? Briefly outline this function
Golgi apparatus
It aids in protein folding protecting proteins against proteases
What groups do vitamins fall into?
Fat soluble
Water-soluble
List the water-soluble and fat-soluble vitamins
Fat soluble: A, D, E, and K
Water-soluble: B group and C
Discuss Vitamin A including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Retinoids: Retinol, retinal, retinoids acid, and beta carotene (not active)
Function: Essential to vision. Promotion of growth, differentiation, and maintenance of epithelial cells, gene expression, and maintenance of reproduction
Deficiency: leads to infertility, night blindness causing dryness of eyes and bitot’s spots
Toxicity: Yes, excess leads to hypervitaminoses which can increase the incidence of fractures
Can water-soluble vitamins be taken in excess?
No, since they are excreted through the urine frequently
Discuss Vitamin D including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Cholecalciferol, Ergocalciferol
Function: Regulation of calcium uptake in the body
Deficiency: Leads to rickets in children and osteomalcaia in adults. Causes soft, bow shaped legs
Toxicity: Yes
Discuss Vitamin E including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoform: Alpha (a) tocopherol (Derivatives of tocopherol are the active forms)
Function: Antioxidant, protects polyunsaturated fatty acids from peroxidation.
Deficiency: Red blood fragility leads to hemolytic anemia and skeletal pain
Toxicity: None
Discuss Vitamin K including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Menadione, menaquinone, and phylloquinon (all active)
Function: Major role in the coagulation cascade
Deficiency: Bleeding (hemorrhagic disease of the newborn). Rare in adults
Toxicity: Rare but can happen
How is Vitamin K produced?
Intestinal bacteria
What is the active form of Vitamin D
Calcitriol
Outline the absorption of fat soluble vitamins
The fat soluble vitamins are cleaved from carrier proteins by pancreatic enzymes in the small intestine.
Bile salts then solubilise them for absorption into micelles and chylomicrons.
They are then transported to the liver for storage via the lymph system
Discuss Vitamin B1 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical isoform: Thiamine
Function: Involved in the conversion of pyruvate to acetyl CoA in the TCA and branched amino acid oxidation
Deficiency: Wernicke-Korsakoff syndrome (common in alcoholics).
Symptoms: Leads to tachycardia, vomiting, convulsion, loss of memory, and loss of eye movements
Toxicity: None
What is convulsion
Medical condition where body muscles contract and relax repeatedly => uncontrolled movements
Discuss Vitamin B2 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Riboflavin
Function: Electron transfer
Deficiency: Ariboflavinosis
Symptoms: Causes inflammation of the lips, cracking of skin at the corner of the mouth.
Toxicity: None
What is the active form of Vitamin B1?
Thiamine pyrophosphate
Discuss Vitamin B3 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Niacin
Function: Electron transfer. Form the coenzymes NAD+ and NADP
Deficiency leads to Pellagra (3D disease): Diarrhea, Dermatitis, Death
Toxicity: None
List all the B vitamins (Just the numbers)
B1,2,3,5,6,7,9,12
Discuss Vitamin B5 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Pantothenic Acid
Function: Required for the synthesis of Coenzyme A. It is the Acyl carrier.
Deficiency: Numbness, tingling of hands and feet, vomiting and fatigue.
Toxicity: None
Discuss Vitamin B6 including it’s biochemical isoform(s), active forms, function, deficiency, and toxicity
Biochemical Isoform: Pyridoxine, pyridoxamine
Active forms: PLP, PMP
Function: Coenezyme for enzymes, particularly in amino acid metabolism
Deficiency: Glossitis, neuropathy, microcytic hypochromic anemia
Toxicity: Yes, sensory neuropathy at high doses
What is Glossitis
Inflammation of the tongue
What is Neuropathy
Damage or dysfunction of nerves resulting in numbness, tingling, weakness, and pain
Discuss Vitamin B7 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Isoforms: Biotin
Active form: Enzyme bound biotin
Function: Attached at the active site of carboxylases
Deficiency: Scaly red rash around eyes, nose, mouth, and genital area
Toxicity: None
Discuss Vitamin B9 including it’s biochemical isoform(s) active form, function, deficiency, and toxicity
Biochemical Isoforms: Folic acid, Folate
Active form: Tetrahydrofolic acid
Function: Coenzymes in single carbon transfer reaction, biological methylation reaction, synthesis of methionine from homocysteine, purines, and thymidine monophosphate
Deficiency: megaloblastic anemia, Neural tube defects
Symptoms: Anemia, higher than normal levels of plasma homocysteine, low birth weight
Toxicity: none
What does the administration of high levels of folic acid lead to?
Masking of vitamin B12 deficiency
Discuss Vitamin B12 including it’s biochemical isoform(s), function, deficiency, and toxicity
Biochemical Form: Cobalamin
Function: Biological methylation reactions: Homocysteine to methionine: synthesis of succinyl-CoA
Deficiency leads to pernicious anemia, dementia, and spinal degradation. Deficiency also leads to increased levels of homocysteine causing megaloblastic anemia
Toxicity: none
How is Vitamin B12 absorbed in the body?
Vitamin B12 needs to bind to an intrinsic factor to be absorbed in the gut.
Discuss Vitamin C including it’s biochemical isoform(s) active form, function, deficiency, and toxicity
Biochemical Isoform and Active form: Ascorbic Acid
Function: Antioxidant, coenzyme for hydroxylation reactions such as the synthesis of collagen
Deficiency leads to scurvy due to impaired collagen synthesis where there will be sore spongy gums, loss of teeth, and poor wound healing.
Toxicity: Yes. At risk for calcium oxaloacetate stones.
