Topic 9-10: Photosynthesis Flashcards
Differentiate between anabolism and catabolism
- Anabolism: producing large molecules from smaller ones and requiring energy input
- Catabolism: breaking large molecules into smaller ones and releasing energy
Different between oxidation and reduction
- Oxidation: losing or donating electrons
- Reduction: gaining or receiving electrons
Explain how ATP can be used to power cellular processes
Energy is stored in the bond between the 2nd and 3rd phosphate group of ATP. When ATP is used, the bond is broken, yielding ADP, Pi and energy which can be used to power cellular processes.
The amount of ATP in cells tends to be small, so how can it be used for many cellular processes?
ATP amount at any one time is small, but in general, a lot of ATP is produced in one day and it is constantly recycled to store as well as releasing energy.
High turnover rate
Identify and describe 2 main ways organisms can acquire energy
- Heterotrophy: consume ready form of energy/ other organisms and acquire energy from those
- Autotrophy: self-feeding organisms, have to process the incoming resources to make food
Write the equation showing the transformation of radiant energy into chemical energy by photosynthesis
6CO2 + 6H2O + energy –> C6H12O6 + 6O2
The input energy is sunlight and the output energy is in form of sugars/glucose.
Identify the 2 stages and their location in photosynthesis
Stage 1: Light reaction in chlorophylls located in thylakoid membrane
Stage 2: Calvin cycle or light-independent in chloroplast stroma
Explain the overall organisation of the light reactions in photosystems I and II
- PSII:
+ Light energy is captured by antenna complex then reaches P680 reaction center, in which the electrons are excited into higher energy levels.
+ The high-energy electrons are then passed to other proteins, losing energy during that process which is used to pump protons/H+ ions from stroma into the lumen, creating a proton gradient.
+ The electrochemical gradient drives H+ ions back into the stroma via ATP synthase, catalyzing phospholyration of ADP to produce ATP.
+ Water is split, then produce electrons to offset the lost electrons in P680 and also, O2. - PS1:
+ The high-energy electron after being passed through the electron transport chain arrive at P700 reaction center with low energy level.
+ Light energy is captured, causing the electron to be excited to an even higher energy level which makes the chlorophyll have a high redox potential.
+ That energy is then used to reduce NADP+ to NADPH, a reducing agent needed for Calvin cycle.
Describe the model of how chlroplasts are arranged to receive and transfer energy
Many pigment molecules, mostly chlrophylls, are grouped into what is called Antenna complex. This acts as a funnel to to capture light energy from a large area to focus it to the reaction center where electron transfer can happen.
What is a reaction center?
Reaction center refers to special pairs of chlorophylls
How is light energy transfered from 1 chlrophyll to another?
As light hits the 1st chlorophyll, the electrons are excited and jumping to a higher energy level. This electrons eventually falls down to previous energy level and during that, it transfers energy to the electrons of the next chlorophyll.
How does proton gradient result in ATP synthesis?
When protons or H+ ions are pumped from the stroma into lumen, they are going against the concentration gradient. So eventually, they diffuse out into the stroma again via ATP synthase, a protein integrated in the thylakoid membrane. The protons move creating energy to catalyze phospholyration of ADP to produce ATP.
Identify differences between cyclic and non-cyclic photophospholyration
- In cyclic photosynthesis, the electrons after going through the electron transport chain return to the previous chlrophyll without having the next step of arriving at P700 like in non-cyclic one.
- The reducing agent in cyclic process is produced by taking H2S from the atmosphere to reduce NADP+.
–> cyclic photosynthesis generates ATP and reducing agent in separate steps
How important is compartmentalism in photosynthesis?
- Keep the stages separated
- What makes proton gradient possible –> without proton gradient, ATP cannot be produced.
Rate evolutionary advantage of organisms undergoing cyclic photosynthesis, non-cyclic photosynthesis and heterotrophy
Organisms utilizing non-cyclis photosynthesis have advantage over those using cyclic process. Heterotrophs have the least evolutionary advantage because they depend on preformed organic matter which is depletable.
