Chapter 10 - Anabolism with Emphasis on Photosynthesis Flashcards
What is anabolism?
The set of metabolic pathways that construct molecules from smaller units. These reactions require energy.
Monomer -> Polymer
Opposite of catabolism, intermediates of glycolysis and ceulluar respiration can be used to form larger carbon chains.
Where does photosynthesis occur?
Chloroplast
Plants contain specialized organelles called plastids
Plastids are used for storage and photosynthesis
Plastids involved in photosynthesis contain large quantities of green pigment called chlorophyll- hence plastids containing chlorophyll are called chloroplasts.
What is an autotroph?
Autotrophs sustain themselfs without eating anything derived from other organisms.
Photoautotrophs not only feed themselfs- but feed the world, like plants.
What is a spectrophotometer?
Measures a pigment’s ability to absorb various wavelengths by sending light through pigments and measuring the fraction of light trasmitted at each wave length.
What are the two stages of photosynthesis?
1. The light reations (energy captured from sun) -
Light energy absorbed by chlorophyll causes the transfer of electrons and hydrogen from water to NADP+ (nicotinamide adenine dinucleotide phosphate)
ATP is produced, via photophosphorylation
Occurs in the thylakoids
2. Calvin Cycle
there are numerous different pigments that absorb light at different wavelengths that can drive the light dependent reactions, what are the two main pigments for a plant?
What is the difference between the two?
Chlorphyll a
has a CH<strong>3</strong> group
Chlorphyll b
has a CHO group
Chlorophyll b transfers its energy to chlorophyll a.
During photosynthesis, how does chlorophyll become excited ?
The light energy absorbed by the pigment molecules causeschlorophyll to jump up into an excited state.
The excited state is unstable and has higher potential energy. When excited electrons fall back to ground state, photons are given off which create and afterglow called fluorescence.
What system is used to harvest light?
A Photosystem
Light-harvesting Complexes (pigment molecules bound to proteins) funnel the energy of photons to the reaction center.
Reaction-center Complexes (a protein complex) surrounded by light-harvesting complexes.
What are the two photosystems ?
1) Photosystem II (PS II)
2) Photosystem I (PS I)
What are the the 2 possible routes for electron flow during light reactions ?
A. Linear electron flow
B. Cyclic electron flow
Explain the steps to the linear electron flow (9 steps)
(Hint *Z PATH)
Linear Electron Flow
1) Light hits PSII
2) Water is oxidized by PSIPI
* 2 H+ released
* 2 e- move to P680 reaction centre chlorophyll molecules
* 1 Oxygen atom combines with another to form O2 gas.
3) At PSII reaction centre, electrons are excited and passed to..
4) Platoquinones (Pq), then passed to…
5) Cytochrome complex
* H+ pumped across membrane
* Then e- passed to…
6) Plastocyanin, then passed to…
7) At PSI reation centre, electrons excited AGAIN, passed to…
8) Ferredoxin, then passed to…
9) Enzyme “Ferredoxin NADP+ reductase”
* NADP+ is reduced to NADPH
Explain the steps to the Cyclical electron flow (4 steps).
Cyclical electron flow
Uses only photosystem
Happens concurrently with linear electron flow
1) At PSI electrons are excited and pass to Ferredoxin (FD) BUT!
Instead of Fd -> NADP+ reductase (linear electron flow)
2) Ferredoxin passes electrons back to Cytochrome complex (Cyclic Electron Flow), then electrons are passed to…
3) Plastocyanin (Pc), then passed to…
4) PSI again to be excited by light energy again.
Main purpose: pumps H+ across thylakoid membrane.
Cyclic electron flow generates surplus ATP, satisfying the higher demand in the Calvin cycle.
What is the main purpose to the Cyclical electron flow?
Pumps H+ across thylakoid membrane.
Highlight the key differences between Linear and Cyclic Electron flow.
Linear Electron Flow produces NADPH and ATP
Cyclic electron flow only produces ATP
Calvin cycle needs more ATP than NADPH
Cyclic electron flow is though to have evolved before linear electron flow. Cyclic electron flow may also protect cells from light-induced damage.
Briefly explain the process in which Mitochondria and the Chloroplast act on photosynthesis.
Mitochondria: proteins are pumped to the intermembrane space and drive ATP synthesis as they diffuse back into the mitochondria matrix.
Chloroplasts: protons are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma.
What are the three steps to the calvin cycle?
1) Carbon Fixation
2) Reduction
3) Regeneration of CO2 acceptor
Summarize how light is harvested
