Cycle 5 - Integrated Metabolism Flashcards
Explain what is happening in this graph
- Nothing present, no change
- Mitochondria added: rate of oxygen is negative
- NADH added: substrate is added so the rate is steep negative
- ADP and Pi are added: rate becomes even more negative due to the function of cycling protons which clears them out of the intermembrane space and makes room for more
- Uncoupler is added: highest rate of consumption because the protons just flow back rapidly since they are not used to produce ATP
Define respiratory control
Respiratory control: the rate of ETS is influenced by the availability of ADP + Pi
State the metabolic link(s) between chloroplast and mitochondria.
- More light = more chlamy growth, so the chloroplast and mitochondria must be linked
- Light reactions make ATP, Calvin cycle consumes it - again, ATP cannot leave the chloroplast - but G3P can. G3P is the link that is brought to the cytoplasm, processed into pyruvate (or other useful items), and then enters the mitochondria into the citric acid cycle and then ETS.
Compare autotrophic growth versus heterotrophic growth
Autotrophs are organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis)
Heterotrophs cannot synthesize their own food and rely on other organisms — both plants and animals — for nutrition.
State the reasons why Chlamydomonas can grow as a heterotroph on certain reduced carbon compounds - but not others.
Chlamy can grow on a molecule called acetate. It has transporters on its plasma membrane for acetate and it uses the C-H bond in acetate to acquire the energy.
- It can’t grow on anything else in the environment (ex., glucose) because it doesn’t have a specified transporter for those substances
Describe CO2 and O2 production and consumption in respiration versus photosynthesis.
- Respiration: consumes O2 (for ETS combination with electrons as the final acceptor) and produces CO2 (Krebs cycle)
- Photosynthesis: consumes CO2 (for Calvin cycle) and produces O2 (light dependent reactions; splitting of water)
How is photosynthesis measured using gas exchange?
We can measure
- The rate of CO2 fixation in Calvin cycle
- The rate of O2 production
Explain this curve
CO2 fixation rate vs. light intensity
- At 0 light, only cell respiration occurs so the rate of CO2 fixation is negative (CO2 is being produced)
- Light limited phase: linear relationship because as light increases, NADPH and ATP production is proportionally increasing, therefore so is the Calvin cycle
- Light saturated phase: the limit of CO2 fixation is reached; eventually, something else becomes the limiting factor and prevents the Calvin cycle from inclining despite adequate light
Define light compensation point
The light intensity at which CO2 fixation rate is 0 (CO2 consumption by respiration = CO2 production by photosynthesis)
A plant will die if it is growing at the light compensation point
Growth means carbon gain (weight gain); thus the plant must be fixing more than it is respiring
How is enzyme activity measured?
By measuring product production or the disappearance of a substrate using a colorimetric assay that turns the media purple based on how much product there is
Explain this enzyme curve
Enzyme curve
- Velocity = rate of product production
- [S] = increasing substrate
- Vmax = velocity eventually saturates
- Km = a substrate concentration; the concentration required to get 1/2 the max velocity
- Higher affinity (interaction between the enzyme and the substrate) means a lower Km
What is a competitve inhibitor?
Draw the affinity curve
- A molecule resembles the substrate and so competes with the true substrate for the activation site
- Vmax is the same but the competitor does change Km (more substrate is required to reach Km with a competitor)
- Eventually, however, if enough substrate is added, it won’t have an effect
What is non-competitve inhibition and non-competitve activation?
Draw the affinity curve for non-competitive inhibition
- Non-competitive inhibition: the allosteric inhibitor binds to the allosteric site (somewhere other than the active site) and changes the shape of the enzyme so that the substrate can no longer bind to the substrate
- Non-competitive activation: the allosteric inhibitor binds to the allosteric site and changes the shape of the enzyme so that it can bind to the substrate
Due to non-competitive inhibition, there are less active enzymes present so Vmax decreases (Vkm remains the same)
