Question

1. The conditions that can cause a mismatch between lactate production and removal include: List those

2. Compare and contrast glucose and fat metabolism. Be sure to include oxygen consumption and ATP production during using each system. Why would someone use CHO when fat produces so much more ATP and why is CHO more efficient as a fuel?

Answer 1

1. The conditions that can cause a mismatch between lactate production and removal include:

Lactic acidosis is a condition when pH of blood falls due to the mismatch between lactic acid production and clearance. Increased lactate production results from impaired tissue oxygenation which might arise from decreased oxygen delivery or defect in mitochondrial oxygen utilization.

Hyperlactatemia arises when the rate of lactate secretion exceeds the rate of xlearancce leads to increased circulation level of lactate.

Causes:

Llactic acidosisis of two broad categories; Type A and Type B.

Type A: resulting from tissue

• Hypoxia
• Inadequate perfusion of tissues in hemorrhagic, cardiogenic and septic shock
• Volume depletion such as hypovolemic shock, severe blood loss
• Severe hypotension as a result of major trauma or acute medical conditions such as myocardial infarction, systemic infection
• Increase in muscular activity that occurs during seizures
• Local muscle tissue hypoxia consequent on a temporary mismatch between oxygen demand and oxygen supply (exercise induced or seizure induced)

Type B : Arises due to normal tissue perfusion and adequate global tissue oxygenation.

Causes:

• Very rare inherited disorders called congenital lactic acidosis
• The deficiency of enzymes of lactate metabolism (either gluconeogenesis or pyruvate oxidation).
• Might arise from carboxylase deficiency, glucose-6-phosphate dehydrogenase deficiency, fructose-1,6-diphosphatase deficiency and pyruvate dehydrogenase deficiency which is more predominant

2. Compare and contrast glucose and fat metabolism

Energy is necessary for normal body functions which can be obtained from macro molecules. Tissues like muscle can use fat or protein as an energy sources but brain and RBC depend on glucose for energy.Ingested carbohydrate is digested and excess glucose is stored in liver as glycogen which can be converted to glucose by gluconeogenesis when needed. Gluconeogenesis is crucial for maintaining blood glucose concentrations during exercise. Fructose and galactose are converted to glucose in liver.

Glucose can be metabolised either by aerobic (need oxygen) or anerobic respiration(doesn't need oxygen). Aerobic glycolysis is predominant which metabolize glucose and oxygen to release energy with carbon dioxide and water as byproducts. Anerobic glycolysis converts glucose to lactate when there is too low oxygen availability. It is efficient during intense short duration exercise. Theoretical yield of ATP per glucose molecule is 38 ATP (2 from glycolysis, 2 from the Krebs cycle, and about 34 from the electron transport system).

The connection between glucose and fat metabolism is that high insulin stimulates triglyceride storing in adipose tissue while low insulin favours release of fatty acids into the plasma. They both also connected via oxidation and gluconeogenesis.

Fat metabolism is the process of breaking down ingested fats into fatty acids and glycerol and then into simpler compounds that can be used by cells of the body. Fat metabolism involves,  hydrolysis of triglycerides into their two principal components, fatty acids and glycerol by lipolysis in cytoplasm. The FA are further oxidized by β-oxidation into acetyl CoA, which is used by the Krebs cycle.

The NADH and FADH₂ which is produced by both beta oxidation and the TCA cycle enters mitochondrial electron transport chain to produce ATP. Energy optained by fatty acis depends on the number of carbon molecule in the FA. For example, complete oxidation of 16C FA yield 129 ATP molecules.

Energy released per gram of fat = 9.3kcal/g; oxygen required- 1.96 O2/g and CO2- 1.39 CO2/g

Energy released per gram of CHO = 4.1kcal/g; oxygen required- 0.81 O2/g and CO2- 0.81 CO2/g

The major pools of CHO are muscle glycogen and liver glycogen along with glucose from the intestines. Muscle glucose can be easily combusted also used in aerobic condition. Though fat yield high energy, it requires more oxygen at the same intensity made it less efficient.