Metabolic Physiology Flashcards
Oxidative phosphorylation occurs in the nucleus of cells
False. Oxidative phosphorylation takes place in the inner membrane of the cells mitochondria.
Acetyl CoA is the only route into the Kreb’s cycle
False. Lactate (via oxygenation to pyruvate), ketoacids and amino acids gain access to the Kreb’s cycle via various intermediate molecules, not through the acetyl CoA route.
Fats undergo β-oxidation to produce glycerol and free fatty acids (FFA)
False. β-oxidation of fats produces only FFA, not glycerol.
Glycolysis of glucose produces a net yield of 2 ATP
True. 4 ATP molecules are produced but 2 ATP are required in the glycolytic process, leaving a net yield of 2 ATP.
The yield of ATP from FFA depends on the size of the FFA
True. In β-oxidation two-carbon units are sequentially cleaved from the FFA chain. From each of these two-carbon fragments an acetyl CoA molecule is formed. The longer the FFA chain the more acetyl CoA and hence more ATP is synthesized.
For every glucose molecule, a lactate molecule is produced
False. For every glucose molecule, 2 pyruvate and therefore 2 lactate molecules are produced.
There is a net yield of 2 ATP for every glucose molecule metabolized
True. 4 ATP are created, but the initial reaction requires 2 ATP therefore there is a net gain of only 2 ATP.
Lactate enters the Krebs Cycle
False. The Kreb’s cycle requires oxygen and is therefore isn’t part of anaerobic metabolism.
Anaerobic glycolysis produces the same net yield of ATP as glycolysis in aerobic metabolism
True. Glycolysis produces a net yield of 2 ATP regardless of whether it is aerobic or anaerobic.
Anaerobic metabolism takes place in the cytoplasm of muscle cells
True. Anaerobic metabolism occurs in the cytoplasm of all of the bodies cells.
Lactic acid
Is formed from pyruvate in the absence of oxygen
True. In anaerobic metabolism pyruvate is converted to lactate rather than acetyl CoA.
Lactic acid
Is converted to glucose by the Cori cycle
True. Lactate is transported to the liver to be converted back to glucose in the presence of oxygen in a process called the Cori cycle.
Lactic acid
Can be increased in the blood even if inhaling an FiO2 of 1.0
True. Hypoxia may still be present in cells even when breathing 100% oxygen.
Lactic acid
Is not formed in red blood cells
False. Anaerobic metabolism can occur in red blood cells.
Lactic acid
Can enter the Kreb’s cycle directly via the cycle’s intermediate molecules
False. Lactic acid cannot enter the Kreb’s cycle directly unless converted back to glucose first via the Cori cycle (the vast majority) or through conversion back to pyruvate.
The end products of full aerobic metabolism of glucose are ATP, H2O and CO2
True. The equation is: C6H12O6 + 6O2 → 6H2O + 6CO2 + 38ATP
Acetyl CoA combines with citric acid to enter the Kreb’s cycle
False. Acetyl CoA combines with oxaloacetate to produce citric acid in the first step of the Kreb’s cycle.
Amino acids only gain access to metabolic pathways via pyruvate
False. They can also gain acces via the Krebs cycle intermediate molecules (oxaloacetate, fumarate, succinate, α-ketoglutarate).
Glycolysis is anaerobic
True. Glycolysis occurs in the cytoplasm and requires no oxygen.
Proton pumps are essential in the aerobic generation of ATP
True. Proton pumps are essential in the electron transport chain to create a hydrogen ion gradient across the inner membrane of the mitochondrion. The hydrogen ions (protons) then flow through ATP synthetase channels, thus generating ATP.
Starvation causes:
Increased protein breakdown
True. Protein breakdown increases to maintain blood glucose levels though gluconeogenesis.
Starvation causes:
Increased glycogen synthesis
False. This synthetic reaction is decreased.
Starvation causes:
Decreased lipid metabolism
False. Lipid metabolism is increased to create energy.
Starvation causes:
Increased plasma glucose levels
False. Plasma glucose levels decrease over the first few days to about 3.5, but is then maintained at this new lower level by gluconeogenesis.
Starvation causes:
Increased cellular glucose uptake
False. Cells begin to use ketoacids rather than glucose for their energy needs.
In starvation:
The renal cortex converts to using ketoacids as its main substrate
True. However glucose remains the renal medulla’s primary substrate.
In starvation:
Death occurs due to protein malnutrition
True. Once the body’s fat stores are depleted, protein metabolism accelerates and death will follow.
In starvation:
Athletes tend to live longer than obese people
False. Once the body’s fat stores are depleted, protein metabolism accelerates and death will follow.
In starvation:
Glycogen stores only occur in the liver
False. Glycogen also occurs in muscle.
In starvation:
Glycogen is broken down to ketoacids
False. Glycogen is broken down to glucose.
Starvation causes:
Metabolic alkalosis
False. The pH status is kept within the normal range in the face of increased ketoacid load.
Starvation causes:
Rapid exhaustion of carbohydrate stores
True. Carbohydrate stores in the form of glycogen are exhausted within the first day of the last food intake.
Starvation causes:
Increase in urinary nitrogen excretion
True. Increase in protein breakdown for gluconeogenesis causes an increase in urinary nitrogen excretion.
Starvation causes:
Rapid neuroglycopaenia
False. Blood glucose levels are kept constant up towards the terminal phase of starvation and death although at a lower set level of 3.5 mmol/l.
Starvation causes:
Increased utilization of glucose by the brain
False. 50% of the CNS converts to ketoacid metabolism to conserve glucose stores.
In starvation:
Enterocytes convert to ketoacid metabolism
True. Enterocytes do convert to ketoacid metabolism (erythrocytes don’t).
In starvation:
Full ketoadaptation takes only a few days to implement
False. Full ketoadaptation takes up to two weeks to implement.
In starvation:
There is increased fat breakdown
True. This occurs to preserve the protein.
In starvation:
There is a negative nitrogen balance
True. This can be used in intensive care units to determine a patient’s nutritional status. If the amount of nitrogen in a patient’s feed is less than the amount of nitrogen being excreted in the patient’s urine, the patient is in negative nitrogen balance.
In starvation:
The renal medulla converts to ketoacid metabolism
False. The renal medulla remains unable to metabolise ketoacids, using only glucose as an energy substrate.
Consider the following statements regarding the regulation of blood glucose.
Blood glucose concentration is increased by cortisol
True. Cortisol stimulates gluconeogenesis and decreased glucose utilization by cells and therefore increases blood glucose concentration.
Consider the following statements regarding the regulation of blood glucose.
Hypoglycaemia may result from alpha-adrenergic stimulation
False. Alpha-adrenergic stimulation causes inhibition of insulin secretion. Beta-adrenergic stimulation causes glucagon secretion. Both cause an increase in blood glucose levels.
Consider the following statements regarding the regulation of blood glucose.
Insulin inhibits entry of potassium into cells
False. Insulin increases potassium entry into cells and is a common treatment for hyperkalaemia.
Consider the following statements regarding the regulation of blood glucose.
Insulin is anabolic
True. Insulin stimulates synthesis of glycogen, protein and fat (all anabolic processes).
Consider the following statements regarding the regulation of blood glucose.
Growth hormone and insulin have opposite effects on fat metabolism
True. Insulin causes fat synthesis, and growth hormone causes fat breakdown.
Consider the following statements regarding insulin secretion.
Occurs from the alpha cells of the pancreas
False. It occurs from the beta cells of the islets of Langerhan in the pancreas
Consider the following statements regarding insulin secretion.
Is increased during surgery
False. The stress response that occurs during surgery causes a decrease in insulin levels.