5- anaerobic respiration Flashcards
anaerobic respiration
The partial breakdown of glucose to produce a limited yield of ATP in the absence of oxygen.
overall products from anaerobic respiration
- 2x ATP from glycolysis
- lactate in animals
- ethanol and CO2 in yeast
why so little ATP products from anaerobic respiration
• Without oxygen, there is no terminal electron acceptor in the electron transport chain. Therefore, the electron transport chain stops, and so does the Krebs cycle.
• No ATP is produced in the anaerobic steps.
• Only 2 ATP are made via glycolysis.
lactic acid fermentation in mammals
• Occurs during strenuous exercise when the ETC is unavailable due to insufficient oxygen.
• Pyruvate conversion: Pyruvate, the end product of glycolysis, is reduced to lactate by gaining hydrogen from NADH. This reaction is catalysed by lactate dehydrogenase.
• NAD+ regeneration: NADH is oxidised to NAD+, which is then available for use in glycolysis, allowing anaerobic respiration to continue.
effect of lactate
• The accumulation of lactate in muscle tissue can lead to muscle fatigue.
• pH reduction: High lactate levels lower pH in cells, making the environment more acidic.
• Enzyme inhibition: The lowered pH can inhibit the function of enzymes involved in energy production and muscle contraction, leading to reduced muscle function and fatigue.
• Decreased calcium binding: Acidic conditions can also affect the ability of muscle fibres to bind to calcium, which is essential for muscle contraction.
lactic acid clearance
Post-exercise, the body clears lactate from the muscles.
gluconeogenesis
• Lactate is converted to pyruvate and then to glucose.
• This process occurs in the liver and is known as gluconeogenesis.
• The produced glucose is released into the blood plasma and can be respired or stored as glycogen.
oxidation in well oxygenated cells
• In well-oxygenated brain, muscle, and heart cells, lactate is oxidised back to pyruvate.
• Pyruvate then enters the link reaction and subsequently the Krebs cycle.
alcoholic fermentation in plants and yeast cells
• Occurs due to insufficient oxygen.
1. Glycolysis: Glucose is broken down in glycolysis, producing 2 molecules of pyruvate, 2 molecules of ATP, and 2 molecules of NADH.
2. Pyruvate to acetaldehyde: Each pyruvate is then decarboxylated (loses one molecule of carbon dioxide) to form acetaldehyde. This reaction is catalysed by the enzyme pyruvate decarboxylase.
3. Acetaldehyde to ethanol:
Acetaldehyde is reduced by NADH to form ethanol, regenerating NAD + in the process. This reaction is catalysed by the enzyme alcohol dehydrogenase.
4. Continuation of glycolysis: The regeneration of NAD+ allows glycolysis to continue producing ATP even in the absence of oxygen.
