Cellular respiration - unit 3 AOS 2 Flashcards
cellular respiration
the process by which cells create energy in the form of ATP from a series of biochemical reactions involving the breakdown of glucose.
aerobic cellular respiration
Cells convert glucose into energy in the form of ATP in the presence of oxygen
cellular respiration equation
C6H12O6 + 6O2 → 6H2O + 6CO2 + 30-32ATP
the role of the mitochondria in cellular respiration
- the mitochondria is a double membrane bound organelle that is the site of the second and third stages of cellular respiration
- mitochondrial matrix - the space inside the inner membrane of the mitochondria which is the site of the Krebs cycle
- Cristae - the folds of the inner membrane and the site of the electron transport chain.
stage 1: glycolysis
- involves the breakdown of glucose into two pyruvate molecules, creating two ATP and two NADH molecules
- the pyruvate molecules will be moves to the mitochondria at the end of glycolysis.
- occurs in the cytosol of the cell
inputs and outputs of glycolysis
- inputs - glucose, 2ADP + 2Pi and 2NAD+
- outputs - 2 pyruvate, 2 ATP and 2 NADH
stage 2: the Krebs cycle
- the Krebs cycle involves the production of carbon dioxide and the loading of high energy coenzymes FADH2 and NADH which can be used in the electron transport chain.
- occurs in the mitochondrial matrix
Krebs cycle inputs and outputs
inputs
- 2 acetyl-CoA derived from 2 pyruvate
- 2 ADP + 2Pi
- 6 NAD+
- 2 FAD
outputs
- 4Co2 (+2 from link reaction)
- 2 ATP
- 2FADH2
- 6 NADH (+2 from link reaction)
Krebs cycle - link reaction
- pyruvate produced in glycolysis is oxidised to form acetyl-CoA. This releases carbon dioxide and produces a small amount of NADH.
stage 3: the electron transport chain
- electrons from the loaded coenzymes NADH and FADH2 are unloaded, crearting a proton gradient across the inner mitochondrial membrane.
- As protons are then pumped back across the membrane, it drives significant ATP production
- it occurs in the cristae or inner membrane of the mitochondria
- oxygen acts as the final electron acceptor, forming water
electron transport chain inputs and outputs
inputs
- 6 O2
- 26ADP +26 pi
- 10 NADH
- 2 FADH2
outputs
- 6H20
- 26 ATP
- 10 NAD+
- 2 FAD
enzymes in cellular respiration
- pyruvate kinase catalyses the final step in glycolysis producing pyruvate and ATP
Coenzymes in cellular respiration
- NAD+, FAD and ADP
- these will cycle between their loaded and unloaded form, helping catalyse reactions in cellular respiration.
- unloaded in reactions that need energy and loaded in reactions that produce energy
anaerobic fermentation
- a metabolic pathway involving the breakdown of glucose and ATP production in the absence of oxygen
- begins with glycolysis, producing 2 pyruvate, 2 NADH and 2 ATP
- this is followed by add on stages to regenerate NAD+
- all stages occur in the cytosol
anaerobic fermentation in animals
- lactic acid fermentation involves breaking pyruvate down into lactic acid, while cycling NADH back into NAD+
anaerobic fermentation in yeast
- involves converting pyruvate into carbon dioxide and ethanol, while cycling NADH back into NAD+
enzymes in anaerobic cellular respiration (edrolo)
factors affecting the rate of cellular respiration- temperature
- as temperature increases, the rate of cellular respiration will increases to a certain point
- this is because there is more kinetic energy between particles and so more collisions occur between enzymes and substrates
- above the optimal temperature, enzymes will begin to denature and cellular respiration will decrease
factors affecting the rate of cellular respiration- oxygen
- as the concentration of oxygen increases, the rate of cellular respiration will increase until a certain point
- aerobic cellular respiration requires oxygen for the electron transport chain as it is the final acceptor of electrons
- the presence of oxygen encourages cells to respire aerobically
- the absence of oxygen causes cells to respire anaerobically
- its rate will eventually plateau when enzymes reach their saturation point.
factors affecting the rate of cellular respiration- glucose concentration
- as glucose concentration increases, so does the rate of photosynthesis up until a certain point
- this is because glucose is an input of cellular respiration
- it will eventually plateau when enzymes reac their saturation point
biofuel
- a renewable fuel source derives from biomass such as organic material including lant and animal by-products
- they are typically carbon neutral because the carbon dioxide released during combustion is taken back in by plants during photosynthesis.
production of bioethanol
- sourcing and deconstruction of the biomass
- breaking down starch and cellulose into glucose molecules via enzymatic hydrolysis
- ethanol production via anaerobic fermentation
- dehydration and purification of bioethanol.
biofuels advantages
- biofuels help to reduce carbon emissions and lower the greenhouse effect
- biofuels are more sustainable as they are renewable meaning they can be produced at the rate they are consumes. They reduce the reliance on fossil fuels which are non- renewable.
biofuel disadvantages
- using agricultural land for biofuel production conflicts with growing food demands
- carbon emissions can still occur due to the fossil fuels used to produce bio fuels.
