Key Knowledge 5 Flashcards
cellular respiration
the process by which cells create usable energy in the form of ATP from a series of biochemical reactions, involving the breakdown of glucose
cellular respiration equation
glucose + oxygen —> carbon dioxide + water + energy
C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O + 36 or 38 ATP
Animals: lactic acid fermentation
Glucose —> Lactic acid + ATP
C6H12O6 2 C3H6O3 2 ATP
Plants and yeast: alcohol fermentation
Glucose —> Ethanol + Carbon dioxide + ATP
C6H12O6 C2H5 H 2 CO2 2 ATP
glycolysis
the first stage of aerobic cellular respiration in which glucose is converted to two pyruvate molecules. location is in the cytosol
Krebs cycle
the second stage of aerobic cellular respiration, where multiple reactions occur to create ATP, NADH, FADH2, and the waste product CO2. Also known as the citric acid cycle or TCA cycle. The location is in the mitochondrial matrix
electron transport chain
the third stage of aerobic cellular respiration, in which a series of protein complexes embedded in the inner membrane of a mitochondrion harness the stored energy in NADH and FADH2 to generate large amounts of ATP. The location is the cristae of the mitochondria
Mitochondria
crucial to aerobic cellular respiration as they are the site of the second and third stages, with the first stage (glycolysis) occurring in the cytosol of the cell.
glycolysis inputs
- 1 glucose (C6H12O6)
- 2 ADP + 2 Pi
- 2 NAD+ + 2 H+
glycolysis outputs
- 2 pyruvate
- 2 ATP
- 2 NADH
krebs cycle inputs
- 2 acetyl-CoA (derived from 2 pyruvate)
- 2 ADP + 2 Pi
- 6 NAD + 6 H+
- 2 FAD + 4 H+
Krebs cycle outputs
- 4 carbon dioxide (CO2)
- 2 ATP
- 6 NADH
- 2 FADH2
overall results from krebs cycle
- By breaking down acetyl-CoA, protons and high-energy electrons are released. These protons and electrons are loaded onto NAD+ and FAD molecules to generate high-energy coenzymes NADH and FADH2.
- The Krebs cycle produces two CO2 molecules for every one acetyl-CoA molecule. When added to the single CO2 molecule produced from each of the two pyruvates undergoing the link reaction, this means a total of six CO2 molecules are produced for every original glucose molecule.
- The Krebs cycle produces a small amount of energy in the form of two ATP (one per acetyl-CoA molecule).
ETC inputs
- 6 oxygen (O2) + 12 H+
- 26 or 28 ADP + Pi
- 10 NADH
- 2 FADH2
ETC outputs
- 6 water (H2O)
- 26 or 28 ATP
- 10 NAD+ + 10 H+
- 2 FAD + 4 H+
ETC steps
- NADH and FADH2 unload electrons and protons at the first and second protein complexes of the electron transport chain that reside in the inner mitochondrial membrane. The following reactions take place:
(1) NADH —> NAD+ + H+ + 2 e–
(2) FADH2 —> FAD + 2 H+ + 2 e–. - The excited electrons (from NADH and FADH2) are transferred through a number of different protein complexes embedded in the electron transport chain, powering the active transport of protons (H+) from the mitochondrial matrix into the narrow intermembrane space.
- This leads to a build-up of protons in the intermembrane space.
- To move down their concentration gradient, these protons must travel through the specialised protein channel ATP synthase
- This process produces large amounts of ATP, but also leads to many free protons and electrons building up in the matrix.
Enzymes and coenzymes in cellular respiration
The tightly controlled sequence of biochemical reactions in cellular respiration relies heavily on the use of enzymes and coenzymes to ensure they happen at a fast rate.
unloaded coenzymes
- ADP
- NAD+
- FAD
loaded coenzymes
- ATP
- NADH
- FADH2
anaerobic fermentation
a metabolic pathway that occurs in the absence of oxygen. Involves glycolysis, followed by further reactions that convert pyruvate into lactic acid in animals, or ethanol and CO2 in yeasts
lactic acid fermentation
the process of anaerobic fermentation in animals, where pyruvate produced via glycolysis is converted to lactic acid
ethanol fermentation
the process of anaerobic fermentation in yeasts, where pyruvate produced via glycolysis is converted to ethanol and carbon dioxide. Also known as alcohol fermentation
temperature and pH
Temperature and pH have a large effect on the rate at which cellular respiration occurs due to their effect on enzymes, which are essential in cellular respiration
glucose
Increasing glucose availability increases the rate of cellular respiration until the enzymes reach the saturation point.
oxygen
Increasing the concentration of oxygen will increase the rate of aerobic respiration.
Enzyme inhibition
Enzyme inhibitors decrease the rate of cellular respiration by reducing the activity of enzymes involved in the process.
biofuel
Biofuels are made from organic material known as biomass, which is plant and animal material that can be sourced from many of our existing industries. They offer an alternative to traditional fossil fuels like coal and gas, which are non-renewable
The process of creating bioethanol
- Deconstruction
- Digestion by enzymes
- Ethanol fermentation
- Purification and dehydration
Deconstruction
a process that involves breaking down the cell wall and cellulose of wood, paper, plastic and other plant fibres.
Digestion by enzymes
the break down the starch and cellulose and convert them into glucose and other sugars. This breaking down of polysaccharides is aided by the presence of water in a process known as hydrolysis.
Ethanol fermentation
Ethanol diffuses out of the yeast cells and is harnessed for biofuel production. The ethanol is produced as a product of this process, rather than coming from within the plant.
Purification and dehydration
The ethanol is distilled via the removal of water, converting it into a usable form called biofuel. The biofuel is then purified and is ready to be used as liquid fuel.
