Lecture #13 - Generation of chemical energy in plants Flashcards
Oxygenic photosynthesis is ____ ____ _____ and is ……..
Photosynthesis is “synthesis using light” and is responsible for a large proportion of the planet’s energy resources.
You can have photosynthesis without no oxygen but oxygenic is most popular
Appreicate this
What is this slide basically saying?
The demand for food is increasing because population is increasing but we can’t meet the required demand so needa improve photosythesis
Look at this slide and explain the shizzzz
That drop in the top graph is around green so that’s why plants are green. So absorbing more light that’s not green may increase productivity (?)
The second graph; shows what wavelength supports photosynthesis (and again, green not included). I think if they absorbed all the energy and were black, they’d get way too hot.
Third graph - bacteria didn’t do well in green light
The two primary pigments invilved in photosynthesis are ……….
Okay so looking at this image; the ______ is the light harvesting complex. It’s where the ______ are which absorb light.
That _______ ______ is what absorbs energy from photon.
Chlorophyll a and chlorophyll b (a is bigger player though)
Okay so looking at this image; the circle is the light harvesting complex. It’s where the pigments are which absorb light.
That porphyrin ring is what absorbs energy from photon.
Talk about every black label in this diagram
Yeah
- Where is that photon absorbed?
- What about that transfer of energy?
- Comment on number 4
- That photon is absorbed by light harvesting complex
- Transfer of energy: can pass from one to another chlorophyll molecule and light harvesting complex has heaps of a and b chloro.
- So the e- transferred is high energy. It’s the first molecule that accepts e- from the special chloro
So which of the two photosystems was discovered first?
Photosystem I was but it actually comes after II but they didnt wanna change shit.
Remember this and the names of the five complexes
- 2e- from Photo I go to another protein complex called NADP+ Reductase and this allows NADPH to form (our first product)
- But these 2e- have come from Photo II so these need to be replaced and they’re replaced from H2O. This is an energetically unfavourable reaction bc water stable af and required heaps of energy to get that energy - there is a special catalytic centre in Photo II that enables that to happen (big area of research). This reaction gives us oxygen - another product.
- H+ ions move through cytochrome complex when e- transferred but they also come from when water slipts. These H+ go through ATP synthase since there is a build up of H+ inside membrane to give ATP - last product.
Appreciate this
- Photon of light strikes one of the pigment molecules and excites one of its e- to high state. When e- falls back down, it realeases energy which excites another pigment molecule’s e-. Keeps going until you reach the special chloro a molecules
- The excited e- of special chloro is is transferred to primary acceptor. This e- is replaced by the 2e- from H20 (one by one replaced). The 1/2O2 combines with another O atom made by another split of H20 and goes off.
Appreciate this too
Okay so in the light reactions, water has been split and O2 has been produced - what ther two things have been produced? What are these two used to do in the C____ C_____?
ATP and NADPH - these are used to fix CO2 and produce carbohydrate in the Calvin Cycle
Remember this plz
CALVIN CYCLE:
1) Carbon fixation:
The Calvin cycle incorporates CO2 molecules by attaching them to a five-carbon sugar (RuBp). This reaction is catalysed by the enzyme Rubisco (Dr Summerfield referred to this as the most abundant protein on Earth). This makes a six-carbon sugar, which very quickly splits in half to make two three-carbon sugars.
2) Reduction
Each of the three-carbon sugars is processed in various ways, which requires the input of ATP (energy) and NADPH (electrons), and the output is that one three-carbon sugar (G3P) leaves the cycle. This is the main output of the Calvin cycle, and the three-carbon sugars produced can be put together to form different carbohydrates (e.g. glucose).
3) Regeneration of RuBp
In a series of complex reactions, the remaining carbon compounds are rearranged to form RuBp (the five-carbon sugar). This requires the input of more ATP. It is very important that the RuBp is regenerated, so that it can receive more CO2 and the cycle can begin again.
What is chloroplast development triggered by? And what are the 5 stages of development?
a. Prolamellar body within an ETIOPLAST (highly UNDIFFERENTIATED)
b. Prolamellar body after a one minute exposure to light.
c. DISPERSION of the prolamellar body within the primary layer of lamellas.
d. Formation of GRANA after 24 hours of continuous light exposure.
e. Granum of a fully differentiated CHLOROPLAST (48 hours).
Explain this shizz
A photosystem is composed of a reaction-centre complex surrounded by light-harvesting complexes that funnel the energy of photons to the reaction-centre complex.
When a special pair of reaction-centre chlorophyll a molecules absorbs energy, one of its electrons is boosted to a higher energy level and transferred to the primary electron acceptor.
A photosystem is composed of a reaction-centre complexes surrounded by several light-harvesting complexes.
Reaction centre complex = organized association of various pigment molecules (which may include chloro a, chloro b and multiple carotenoids) bound to proteins.
The number and variety of pigment molecules enable a photosystem to harvest light over a larger surface area and larger portion of the spectrum than any single pigment.
The special pair of chloro a molecules = special bc environment (boost e- to higher lvl but also to a diff molecule - primary e- acceptor).
