1. Topic 8 Metabolism, Cell Respiration & Photosynthesis
Skills, Nature of science & applications

2. 8.1 Metabolism

3. Skill: Distinguishing different types of inhibition from graphs at specified substrate concentration
Red line = competitive inhibition
when substrate exceeds inhibitor concentration, max rate can be achieved, but takes much higher substrate conc to achieve it
Blue line = noncompetitive inhibition
enzyme doesn’t reach same max rate because inhibitor prevents some enzymes from reacting regardless of sub conc
follow same pattern as with no inhibitor
takes same conc of enzyme to reach max rate, but max rate is lower than uninhibited enzyme

4. App: End-product inhibition of the pathway that converts threonine to isoleucine
Amino acid threonine is converted to isoleucine
Series of 5 rxns
As conc. of iso builds up, it binds to allosteric site of 1st enzyme in chain (threonine deaminase)
Iso acts as non-comp inhibitor

5. NOS: Developments in scientific research follow improvements in computing: Developments in bioinformatics, such as the interrogation of databases, have facilitated research into metabolic pathways
Bioinformatics – multiple research groups can add info to a database, enabling other groups to query the database
Chemogenomics = bioinformatics technique for researching metabolic pathways
E.g. scientists developing new drugs test massive libraries of chemicals individually on a range of related organisms
When a drug binds to a target site, it can alter metabolic activity
For each organism a range of target sites are identified and range of chemicals which are known to work on those sites are tested
Chemogenomics = “the chemical universe tested against the target universe”

6. App: Use of databases to identify potential new anti-malarial drugs
Malaria = blood-borne disease caused by Plasmodium falciparum, carried by mosquito
3 reasons we need new drugs:
Increasing resistance
Narrow range of medicines
Global efforts to eradicate malaria
Research:
P. Falciparum strain 3D7 genome sequenced
310,000 chemicals screened against 3D7 & K1 (resistant) to see if chems inhibite metabolism
Related & unrelated organisms also screened (incl humans)
Results of research:
ID of 19 new chems that act as inhibitors
15 chems that bind to total of 61 different malarial proteins
Bioinformatics provided for scientists to continue study

7. Skill: Calculating & plotting rates of rxn from raw experimental results
How to determine rate of enzyme-controlled rxn?
Measure rate of disappearance of substrate
Measure rate of appearance of a product
May require conversion of units to yield a rate unit which should include s-1
DBQ p378 & 379

8. 8.2 Cell respiration

9. NOS: Paradigm shifts: The chemiosmotic theory produced a paradigm shift in the field of bioenergetics
Peter Mitchell Nobel Prize Banquet Speech:
…in the experimental sciences, the scientific fraternity must test a new theory to destruction, if possible. Meanwhile, the originator of a theory may have a very lonely time, especially if his colleagues find his views of nature unfamiliar, and difficult to appreciate.
The final outcome cannot be known, either to the originator of a new theory, or to his colleagues and critics, who are bent on falsifying it. Thus, the scientific innovator may feel all the more lonely and uncertain.
On the other hand, faced with a new theory, the members of the scientific establishment are often more vulnerable than the lonely innovator. For, if the innovator should happen to be right, the ensuing upheaval of the established order may be very painful and uncongenial to those who have long committed themselves to develop and serve it. Such, I believe, has been the case in the field of knowledge with which my work has been involved.
Naturally, I have been deeply moved, and not a little astonished, by the accidents of fortune that have brought me to this point…
Bioenergetics = study of energy flow through living organisms
Peter Mitchell, 1961 – proposed chemiosmotic hypothesis to explain the coupling of electron & H+ transport in mitochondria to ATP synthesis
Hypothesis was radical departure from previous hypothesis, accepted only after many years
Awarded Nobel Prize for Chemistry in 1978

10. Skill: Annotation of a diagram to indicate the adaptations of a mitochondrion to its function

11. Let’s do activity p 387!

12. App: Electron tomography used to produce images of active mitochondria
Electron tomography – technique that allows 3D images of interior of organelles
beam of electrons is passed through sample at incremental degrees of rotation around center of target sample, assembling 3D image
Leader: Dr. Carmen Mannella – “cristae are not simple infoldings but are invaginations, defining micro-compartments in the organelle. The membranes are not only very flexible but also dynamic.”
Inner membrane is dynamic! = intermembrane space increases in volume when mito is active in e- transport

13. 8.3 Photosynthesis

14. NOS: Developments in scientific research follow improvements in apparatus: Sources of 14C & autoradiography enabled Calvin to elucidate the pathways of carbon fixation
Sometimes progress in bio research suddenly becomes possible because of other discoveries!
Kamen & Ruben discovered 14C in 1945
Half-life of 14C makes it ideal for use in tracing pathways of photosynthesis
Melvin Calvin’s “lollipop apparatus”
algae growing in lollipop
replaced 12CO2 with 14CO2
Took samples of algae at very short time intervals to find what % of C compounds contained 14C

15. Calvin used radioactive C as a tracer to see where it goes during the light-independent rxn, hence figured out the order of products in the Calvin Cycle!

16. App: Calvin’s experiment to elucidate the carboxylation of RuBP
cycle.html

17. Skill: Annotation of a diagram to indicate the adaptations of a chloroplast to its function
Structure determines function!
Chloroplasts absorb light.
Large SA of thylakoid membranes allows for large amount of light-absorption
Leaves in sun have deep grana, allowing more light to be absorbed
Chloroplasts produce ATP by photophosphorylation.
Small volume inside thylakoids, so proton gradient develops quickly
Chloroplasts carry out the many chem rxns of the Calvin cycle.
Stroma is compartment in which enzymes needed for Calvin cycle are kept together with their substrates and products, so this concentration speeds up cycle
ATP & NADPH needed for Calvin cycle are easily available because the thylakoids where they are made are distributed throughout the stroma.