Metabolism Flashcards
The liver produces all the following except?
A Coagulation factors
B Albumin
C Gamma Globulins
D Fibrinogen
C
Explanation
Gamma globulins are produced in plasma cells
Regarding vitamin D production, which of the following statements is false?
A Previtamin D3 to Vitamin D3 occurs in the skin
B 1-hydroxylation occurs in the liver
C 25-hydroxylation occurs in the liver
D 24,25 dihydroxycholecalciferol occurs in the kidney
B
Explanation
Vitamin D3 is produced in the skin from 7-dehydrocholesterol by the action of sunlight. Vitamin D3 is metabolised by enzymes of the cytochrome P450 superfamily. 25-hydroxylation occurs in the liver, converting Vitamin D3 into 25-Hydroxycholecalciferol. In the kidney, 25-hydroxycholecalciferol is converted into 1,25 dihydroxycholecalciferol (Calcitriol) by 1∝ alpha hydroxylation, and also into the less active 24,25 dihydroxycholecalciferol by 24-hydroxylation.
Note: 24, 25 dihydroxycholecalciferol and 1,25 dihydroxycholecalciferol both occur in the kidney
All of the following plasma proteins are synthesised in the liver except?
A Complement
B Plasminogen
C Albumin
D Platelet-activating factor (PAF)
D
Explanation
Platelet-activating factor (PAF) is produced by neutrophiles, basophiles, platelets, and endothelial cells
Regarding carbohydrate homeostasis in exercise, which of the following is incorrect?
A Initially muscle utilizes glycogen stores
B Muscle utilizes fatty acids for its metabolism after exercise
C plasma glucose rises due to increased gluconeogenesis
D Insulin secretion increases during exercise
D
Explanation
During exercise, the caloric needs of muscle are initially met by glycogenolysis (glycogen breakdown) in muscle and increased uptake of glucose. Plasma glucose initially rises with increased hepatic glycogenolysis but may fall with strenuous, prolonged exercise. Gluconeogenesis (synthesis of card from non-carb substrates) is increased, plasma insulin falls, plasma glucagon and adrenaline rise
After exercise, liver glycogen is replenished by additional gluconeogenesis and a decrease in hepatic glucose output.
Note: resting muscle utilizes fatty acids for its metabolism and so does muscle after exercise.
Regarding the respiratory quotient (RQ), which of the following is false?
A RQ of carbohydrate is 1.00
B Average is about 0.82 for proteins
C RQ of brain tissue is approximately 0.99
D RQ of fat is 0.90
D
Explanation
RQ of the brain is regularly 0.97-0.99, indicating that its principal but not its only fuel is carbohydrate.
RQ of fat is 0.7
RQ for carbohydrates (CHO) is 1.00. This is because H and O are present in carbohydrates in the same proportion as in water, whereas in the various fats, extra O2 is necessary for the formation of H2O.
RQ of proteins has an average of 0.82.
Which of the following has the highest molecular weight (daltons)?
A Alpha globulin
B Beta 1 globulin
C Fibrinogen
D Albumin
C
Explanation
Fibrinogen: 340,000
Alpha globulin: 90,000-150,000
Albumin: 69,000
HB: 64,450
Beta 1 globulin: 64,450
Immunoglobulins (Antibodies): For example, immunoglobulins (IgG, IgA, IgM, IgE, and IgD) typically have molecular weights ranging from about 150,000 to 900,000 Daltons, with IgG being approximately 150,000 Daltons.
Alpha and Beta Globulins: Other globulins, such as alpha-1-antitrypsin and transferrin, have molecular weights generally ranging from 40,000 to 150,000 Daltons.
Fibrinogen is noted to have a molecular weight of approximately 340,000 Daltons (or 340 kDa).
The majority of heat lost by the body at 21 degrees is by which of the following mechanisms?
A Radiation
B Sweating
C Defaecation
D Urination
A
Explanation
At 21 C body heat is lost by;
- radiation/conduction (70%)
- vaporization of sweat (27%)
- respiration (2%)
- urination and defecation (1%)
In relation to adenosine triphosphate (ATP), which of the following statements is correct?
A ATP is a stable chemical compound that is present in all cells
B ATP is a combination of adenine ring, ribose sugar and 2 phosphate group radicals
C ATP is present everywhere in the cytoplasm and nucleoplasm
D ATP becomes guanosine triphosphate (GTP) after the loss of one phosphate radical
C
Explanation
ATP consists of 3 phosphate groups, an adenine ring and a ribose sugar. ATP becomes adenosine diphosphate (ADP) after the loss of one phosphate radical.
ATP is an unstable molecule which hydrolyzes to ADP and inorganic phosphate when it is in equilibrium with water. The high energy of this molecule comes from the two high-energy phosphate bonds. The bonds between phosphate molecules are called phosphoanhydride bonds. They are energy-rich and contain a ΔG of -30.5 kJ/mol.
Resonance stabilization of ADP and of Pi is greater than that of ATP. The oxygen molecules of the ADP are sharing electrons. Those electrons are constantly being passed back and forth between the oxygens, creating an effect called resonance. This stables the ADP. Resonance does not occur in ATP; therefore, it is a more unstable molecule.
Source: https://chem.libretexts.org
Which of the following is not produced in the Kreb’s (citric acid) cycle?
A ATP
B CO2
C H+ ions
D NAD+
D
Explanation
In the Kreb’s cycle NAD changes to NADH + H
Note: a review of the Kreb’s cycle (citric acid cycles) in web sources do not have NADH + H becoming NAD (in the step form Isocitrate 6C to alpha Ketoglutarate 5C. I dare say the figure in the prescribed TB may be wrong?
The total numbers of molecules generated in the oxidation of pyruvate and the Krebs Cycle is:
8 NADH
2 FADH2
2 ATP
6 CO2
Net Engergy Production from Aerobic Respiration
Glycolysis: 2 ATP
Krebs Cycle: 2 ATP
Electron Transport Phosphorylation: 32 ATP
Each NADH produced in Glycolysis is worth 2 ATP (2 x 2 = 4) - the NADH is worth 3 ATP, but it costs an ATP to transport the NADH into the mitochondria, so there is a net gain of 2 ATP for each NADH produced in gylcolysis
Each NADH produced in the conversion of pyruvate to acetyl COA and Krebs Cycle is worth 3 ATP (8 x 3 = 24)
Each FADH2 is worth 2 ATP (2 x 2 = 4)
4 + 24 + 4 = 32
Net Energy Production: 36 ATP- Actually it is 38!-see below.
Extra: During the Krebs cycle - the sequence of chemical reactions in which the acetyl portion of acetyl-CoA is degraded to carbon dioxide and hydrogen atoms. The released hydrogen atoms are not simply let loose in the intracellular fluid. Instead they are released in packets of two, and in each instance, the release is catalyzed by a specific protein enzyme called dehydrogenase. Twenty of the 24 hydrogen atoms immediately combine with nicotinamide adenine dinucleotide (NAD+), a derivative of the vitamin niacin, leading to NADH & H+. The remaining four hydrogen atoms released between succinic and fumaric acid stages combine with FAD to make FADH2.
Neither GTP nor NAD + are products of the Kreb’s cycle
Note- actually, when succinyl-CoA is converted to succinate (this reaction actually produces guanosine triphosphate (GTP), but the GTP is converted to ATP, making the net production of ATP per mol of blood glucose metabolised aerobically by via the Embden- Myerhof pathway and citric acid cycle 38 ATPs
Which is true regarding the secretion and action of calcitonin?
A Calcitonin is secreted by the follicular cells of the thyroid
B Calcitonin has a half life of 20minutes
C Calcitonin decreases excretion of calcium in the kidney
D Calcitonin decrease serum phosphate levels
D
Explanation
Calcitonin is found in the parafollicular cells of the thyroid (also called C or clear cells). It is secreted in the presence of a high calcium concentration. Calcitonin lowers circulating calcium and phosphate levels. It exerts it calcium lowering action by inhibiting bone resorption. It also increases calcium excretion in the urine. B-adrenergic agonists, dopamine, oestrogens, gastrin, CCK, glucagon and secretin have all been reported to stimulate calcitonin secretion. Gastrin being the most potent
Human calcitonin has a half life of less than 10 minutes
NOTE: ISSUE:
In the current TB: it reads: unlike PTH and 1,25 dihydroxycholecalciferol, calcitonin does not appear to be involved in phosphate homeostasis.”
However a websource extra: Source: Calcium and phosphate haemostasis
I am going to leave the questions as is, but would follow the TB findings in the exam
Renal Morphogenesis and Development of renal function. Jean Pierre Guignard
Which is true regarding temperature regulation?
A The temperature is lowest at about 06:00 and highest in the evenings
B Decreased metabolic states lower the core temperature by up to one degree
C Physiological normal adults cannot have a raised body core temperature
D During exercise, the body core temperatue can rise to 42C
A
Explanation
The normal human core temperature undergoes a regular circadian fluctuation of 0.5-0.7C. In people who are awake in the day and sleep at night, the temperature is lowest at about 06:00 and highest in the evenings. It is slightly higher in the awake but relaxed state, and rises with activity. An additional monthly cycle of temperature variation occurs at the time of ovulation. In children tempreture regulation is less precise and is normally 0.5C above the established norm. During exercise, the body core temperatue can rise to 40C. It is chronically raised about 0.5C in conditions such as hyperthroidism (conditions where metaboic rates are high). and lower in states where the metabolic state is low (hypothyroidism). There are normal adults who have raised temperature (constitutional hyperthermia)
After prolonged fasting, the body’s energy is derived from?
A Glycogenolysis
B Lypolysis
C Amino acids and glycerol
D Glycogen and gluconeogenesis of fat
C
Explanation
Plasma glucose level is determined by the amount entering the bloodstream and the amount leaving it. The principal determinants are therefore dietary intake, rate of entry into muscle cells, adipose tissue, other organs and the glucostatic activity of the liver. 5% of ingested glucose is promptly converted to glycogen in the liver, 30-40% is converted into fat. The remainder is metabolised in muscle and other tissues. During fasting, liver glycogen is broken down and added to the bloodstream. With more prolonged fasting, glycogen is depleted and there is increased gluconeogenesis from amino acids and glycerol in the liver. Plasma glucose declines modestly during prolonged starvation in normal people, but symptoms of hypoglycaemia do not occur because of gluconeogenesis
Which hormones DO NOT stimulate gluconeogenesis?
A Epinephrine
B Growth hormone
C Cortisol
D Insulin
D
Explanation
Diabetogenic hormones: glucagon, growth hormone, epinephrine, and cortisol, stilulate gluconeogenesis
Insulin inhibits gluconeogenesis, as does alcohol.
