cellular respiration Flashcards
cellular respiration
breaks the energy stored in glucose into smaller packages stored in ATP. Glucose can be broken down to produce ATP via two different pathways: aerobic cellular respiration or anaerobic fermentation
- allows cells to break down large molecules and produce substantial amounts of the high-energy molecule ATP.
- Is a catabolic reaction → releases energy
cellular respiration equation
C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP
coenzymes in CR
Some cellular respiration enzymes require some extra help to catalyse their reactions.
Three key coenzymes in cellular respiration
ATP
NAD+
FAD
Coenzymes will cycle between unloaded (ADP, NAD+, FAD, CoA) and loaded (ATP, NADH, FADH2, acetyl-CoA) states as they help catalyse the reactions of cellular respiration
Some may require the loaded, while some require unloaded
Coenzymes are unloaded in reactions that need extra energy and become loaded in reactions that produce energy. This ensures that coenzymes can always be efficiently recycled
aerobic cellular respiration; equation and purpose
GLUCOSE + OXYGEN → CARBON DIOXIDE + WATER + ATP
Purpose: breakdown glucose and generate more ATP
* more efficient than anaerobic (30 OR 32 compared to 2 ATP)
mitochondria in relation aerobic cellular respiration
crucial, as site of both second and third stages of ACR
- mitochondria are the site of aerobic cellular respiration, which produces the majority of energy/ATP for the cell
structural features of mitochondria
DIAGRAM
Outer membrane (also composed of a phospholipid bilayer)
Inner membrane (composed of a phospholipid bilayer)
Space inside inner membrane → mitochondrial matrix (which is filled with a dense fluid containing many enzymes and solutes)
inner membrane folds into peaks and ridges → cristae (which facilitate the function of the third stage of aerobic cellular respiration)
The intermembrane space between the inner and outer membranes is narrow and has a small volume compared to the matrix. plays an important role in the electron transport chain.
glycolysis; stage, location and inputs and outputs
First stage of aerobic cellular respiration
location: cytosol
inputs:
1 glucose
2 ADP + Pi
2 NAD+ and 2H+
outputs
2 pyruvate
2 ATP
2 NADH
glycolysis role
- It involves the breakdown of 6-carbon glucose into two 3-carbon pyruvate molecules. A small amount of ATP is made in glycolysis
- This can be used to power cellular reactions
- Importantly, the pyruvate and NADH that are produced will go on to help make even more ATP in the next two stages of aerobic cellular respiration.
- The two pyruvate molecules will be transported to the mitochondria, where they will then be modified and broken down further in stage two of aerobic cellular respiration: the Krebs cycle.
krebs cycle; stage, location and inputs and outputs
second stage of aerobic cellular respiration
location: matrix of the mitochondria
inputs:
2 acetyl-coA (derived from pyruvate)
2 ADP + Pi
6 NAD+ and 2H+
2 FAD+ and 4H+
krebs cycle role
- The Krebs cycle generates lots of high-energy electron and proton carriers, NADH and FADH2, which can be used in the electron transport chain.
- Carbon dioxide is released, and small amounts of ATP are also produced.
electron transport chain; stage, location and inputs and outputs
third stage of aerobic cellular respiration
location: cristae of the mitochondria
- Energy from the electrons unloaded by NADH and FADH2 generates a proton gradient that drives significant ATP production.
inputs:
6 O2 and 12H+
26 or 28 ADP and 26 or 28 Pi
10 NADH
2 FADH2
outputs:
6 H2O
26 or 28 ATP
10 NAD+ and 10H+
2 FAD+ and 4H+
ETP role
- The electron transport chain is where the majority of ATP is produced in the process of aerobic cellular respiration.
H+ gradient across the inner mitochondrial membrane driving the electron transport chain enzyme ATP synthase.
The electrons released by NADH are collected by oxygen. - Also converts the high-energy coenzymes NADH and FADH2 back to their NAD+ and FAD forms, which are then recycled for continued use in glycolysis and the Krebs cycle
How to measure aerobic cellular respiration?
Measuring the rate of glucose consumption.
Measuring the rate of oxygen consumption.
Measuring the rate of carbon dioxide production.
Measuring the rate of ATP production.
Measuring the rate of water production.
anaerobic fermentation; purpose
involves the breakdown of glucose and ATP production via glycolysis in the absence of oxygen
allows for the replenishment of NAD+ for continued use in glycolysis
anaerobic fermentation; stages
Occurs in two stages (both in the cytosol):
Glycolysis – breaks down glucose into pyruvate, producing 2 ATP.
Fermentation – converts pyruvate (product depends on cell type).
when no oxygen, what do animals to produce ATP?
- When oxygen availability is insufficient, such as when working at high intensities, animals undertake lactic acid fermentation after glycolysis.
- This process breaks down pyruvate into lactic acid and cycles NADH back to NAD+ for reuse in glycolysis
- Lactic acid cannot accumulate indefinitely, as it lowers the pH of our cells and blood, and can be toxic in high amounts
- As it cannot be accumulated indefinitely, once oxygen is present again, lactic acid is metabolised back into pyruvate and used for aerobic cellular respiration.
KEY ROLE OF FINAL STAGES IN BOTH ANIMAL AND YEAST/PLANT CELLS: recycle NADH and generate NAD+ molecules for continued use in glycolysis when the electron transport chain is inactive.
when no oxygen, what do yeast/plants to produce ATP?
- In yeasts, pyruvate is converted to ethanol and carbon dioxide.
- This consists of a two-step process known as ethanol fermentation.
- Once again, these final steps allow the cycling of NADH back to NAD+ for continued use in glycolysis
- Yeasts are unable to metabolise ethanol into any useful products. Instead, ethanol diffuses out of cells, but the ethanol concentration of a yeast culture in a confined environment can eventually accumulate to toxic levels.
KEY ROLE OF FINAL STAGES IN BOTH ANIMAL AND YEAST/PLANT CELLS: recycle NADH and generate NAD+ molecules for continued use in glycolysis when the electron transport chain is inactive.
factors that affect rate of cellular respiration
temp, pH, glucose availability, oxygen availability, enzyme inhibition
temp in relation to rate of cellular respiration
DRAW DIAGRAM
Below the optimal temperature → enzymes and substrates have less kinetic energy so there are fewer reaction-inducing collisions.
Lower rate of cellular respiration, but still there
Above the optimal temperature → enzymes begin to denature
respiration rate drops rapidly due to the loss of enzyme function.
pH in relation to rate of cellular respiration
DRAW DIAGRAM
Different enzymes function optimally at different pHs.
The cytoplasm typically has a pH of around 7.2, so the enzymes involved in glycolysis (which occurs in the cytoplasm) function optimally under this condition.
The intermembrane space of the mitochondria usually has a pH of around 7.0-7.4, While the matrix has a pH of 7.8.
For this reason, the enzymes that support reactions at these locations may have slightly different optimal pH levels.
Above or below the optimal pH, enzymes begin to denature and the rate of respiration slows
saturation point
the point at which a substance (e.g. an enzyme) cannot receive more of another substance (e.g. a substrate)
glucose availability in relation to the rate of cellular respiration
Increasing glucose availability increases the rate of cellular respiration until the enzymes reach the saturation point. (there is another limiting factor preventing further increase, such as enzyme concentration)
Glucose is the input for glycolysis, the first stage of both aerobic respiration and anaerobic fermentation → meaning, an increase in glucose availability increases the rate of cellular respiration, thereby increasing the rate of ATP production.
A decrease in glucose availability reduces the rate of cellular respiration, thereby reducing the rate of ATP production.
oxygen availability in relation to the rate of cellular respiration
Increasing the concentration of oxygen will increase the rate of aerobic respiration
Aerobic respiration requires oxygen for the electron transport chain to function.
However, oxygen is not an input of anaerobic fermentation.
In animals, low oxygen will induce cells to switch to anaerobic fermentation, while the presence of oxygen will encourage cells to respire aerobically.
As oxygen levels rise, the rate of aerobic respiration increases.
Therefore, more oxygen results in faster ATP production.
enzyme inhibition in relation to the rate of cellular respiration
Enzyme inhibitors decrease the rate of cellular respiration by reducing the activity of enzymes involved in the process.
Competitive inhibitors bind to the active sites of enzymes to prevent the catalysis of substrates
Non-competitive inhibitors bind to the allosteric sites of enzymes. This results in a conformational change to the active site so that the substrate can no longer bind.
Effect of competitive reversible inhibitors CAN BE OVERCOME if the substrate concentration is increased
Increasing substrate concentration DOES NOT REDUCE THE EFFECT of irreversible inhibitors or reversible non-competitive inhibitors.
compensation point
DRAW DIAGRAM
When rate of cellular respiration and photosynthesis meet
