Week 9 Flashcards
What are the two main products of photosynthesis?
ATP and NADPH
What are ATP and NADPH then used to make?
Used to synthesize carbohydrates from CO2 and H20
Which two ways can ATP be made?
Take lipids/sugars out of the cytosol and move them to the mitochondria, make pyruvate, ATP made through electron transport chain
Or
Sunlight and chloroplasts
How do chromophores lose their energy and form the ground state?
Lose energy through heat, flourescence, exiton transfer or charge transfer
Red photons have _____ wavelengths and ____ energy
Longer wavelengths
Less energy
Why doesn’t photosynthesis occur in the UV range?
Photosystems are easily damaged by UV
T/F:
Light reactions occur in the thylakoid membranes and carbon-assimilation occurs in the stroma
True
T/F:
In the light reactions, protons are being pumped from the lumen of the thylakoid to the stroma
False
From the stroma to the lumen of thylakoid
What do thylaokoids stack to form?
Grana
Optimises photosynthesis
Which part of the chlorophyll contains the Mg atom?
Tetraphyrrole cage
T/F:
Cyanobacteria and red algae use phycobilins as their light harvesting pigments
True
What is the role of caratenoids?
They absorb light at wavelengths not absorbed by chlorophyll a and b
also protect the machinery from ROS
What is the benefit of pigments having a variety of absorbance spectra?
Can absorb more light with a variety of different types
More efficient
What occurs at the photochemical reaction centre?
In spinach, a special pair of chlorophyll molecules convert light energy into chemical energy
Explain how antenna molecules are positioned in terms of the photochemical reaction centre
Some are a part of the core complex
Some are around the periphery and form light-harvesting complexes
Electron acceptor acquires a ____ charge
Negative
Light absorption leads to ______
Charge separation
What initiates a proton gradient to be formed ie protons to be pumped across the thylakoid membrane?
Flow of electrons through the electron transport chain
How do photosynthetic bacteria gain electrons?
They use H2S instead of water
How can a photosystem degrade to its ground state?
Through internal conversion
The reactions are rapid and thermodynamically _____.
Downhill
-ve delta g, irreversible
In plants, photosystem 1 absorbs strongly at _____
700nm (far red)
Electrons are transferred from ___ to ___
From water to NADP+
T/F:
In plants,
photosystem goes first in the process and then photosystem goes after
False
other way round
If electrons are passed from ferrodoxin to cytochrome bcf complex what is the result?
More ATP is produced by less NADPH
One electron is transferred from H20 to NADP+ for every ___ photons absorbed
2
One molecule of )2 is formed for every __ photons absorbed
8
The manganese complex is found in which photosystem?
Photosystem II
T/F:
PSII is a trimer and PSI is a dimer
False
Other way round
What products are used from photosynthesis for carbon assimilation?
NAPH and ATP
In the CO2 assimilation cycle, __ enters, ___ leaves and ____ is produced
CO2 enters
Phosphate leaves
Glyceraldehyde 3-phosphate is produced
What are the three reactants needed for cabon assimilation?
Oxygen, ATP and NADPH
T/F:
Carbon assimilation requires 2NADP and 3ATP
True
List one photoautotroph and one chemotroph
Photo=plant
Chemo= human
What to plants reduce to produce trioses?
They reduce CO2 to produce trioses which is the precursor for cellulose, starch, lipids, proteins etc
What are pentose phosphates used for?
Metabolic intermediates - DNA, RNA, Protein and Lipids
What are hexose phosphates used for?
Cellulose
Starch
Sucrose
Which process is used for carbon dioxied assimilation?
Calvin Cycle
What are the three stages of the Calvin Cycle?
Fixation of CO2
Reduction of 3-phosphoglycerate to a triose
Regeneration of Rubisco
T/F:
Most of the triose molecules made in the calvin cycle are used to make sugars
False
5/6 is used to regenerate Rubisco
Where are the enzymes needed for the calvin cycle located?
In the chloroplast stroma
What is the main job for rubisco?
Fixes CO2 to RuBP
Cleaves the unstable 6-C product to two 3-C molecules
T/F:
Rubisco is made of 8 large subunits encoded by the nuclear genome and 8 small subunits encoded by the chloroplast genome
FAlse
large= encoded by chloroplast genome
Small= encoded by nuclear genome
T/F:
Rubisco has a high Kcat
False
low kcat
Need heaps of rubisco to fix sufficient amounts of carbon
Which two ions are critical in the rubisco active site?
Mg2+ ion and Lys that is carbamoylated
T/F:
Starch is made in the chloroplast and sucrose is made in the cytosol
True
T/F:
The Calvin Cycle doesn’t occur in animals
False
It does but 3 enzymes are absent in animals and therefore they cant convert CO2 into glucose
How many NADPH and ATP are needed to synthesize triose phosphate?
6 NADPH and 9 ATP
T/F:
Fixation of CO2 into triose phosphate occurs in the light and dark
False
cease in the dark
What is the side reaction of photosynthesis that has a metabolic cost?
Photorespiration
What does photorespiration consume and produce?
Cosumes O2
Produces CO2
Dependent on light
Explain how photorespiration occurs ie what is produced
Occurs due to oxygenation of RuBP by Ribisco
Forms one molecule of 3-phosphoglyerate and one molecule of wasteful 2-phophoglycolate
Why does the wasteful photorespiration occur? Why doesn’t Rubisoco NOT oxygenate RuBP?
Although Rubisco is specific for CO2 compared to O2, there is greater concentrations of O2 in the air than CO2
The higher the temperature, the higher the ratio of O2 to CO2 in solution and the lower the affinity for CO2
As CO2 is consumed in carbon assimilation, the ratio of O2 to CO2 increases
Photorespiration occurs via the ______ cycle
Oxidative photosynthetic carbon cycle
Which organelles are invovled in the oxidative photosynthetic carbon cycle?
Chloroplast
Peroxisome
Mitochondrion
What does glycine decarboxylase complex do?
Oxidised glycine to CO2 and NH3
