Lecture 8 - Photosynthesis Flashcards
1
Q
What are autotrophs?
A
- use inorganic carbon as a carbon source to fix carbon into organic compounds
- photoautotroph = uses light energy to fix carbon
- chemoautotroph = uses redox reactions to fix carbon
2
Q
What are heterotrophs?
A
- use organic carbon as a carbon and energy course
- chemoheterotroph = use organic carbon as the main nutrient
- photoheterotroph = uses light energy and organic carbon (RARE)
3
Q
Where does photosynthesis occur?
A
- the chloroplast
- arose from endosymbiosis theory
- double membrane-bound with stacks of internal membrane called thylakoids
4
Q
What is the reaction of photosynthesis?
A
6 carbon dioxide + 6 water –> glucose + 6 oxygen
5
Q
Where do light reactions and light-independent reactions occur?
A
light = thylakoids light-independent = stroma and carbon fixation
6
Q
What is the point of light reactions?
A
use energy carried by light and convert it into chemical energy in the form of ATP and NADPH that will be used to power the Calvin cycle
7
Q
What happens to light that is absorbed?
A
- released as heat or fluorescence
- absorbed light can be captured and used as an energy source
- photosystems capture light energy and convert it into chemical energy
8
Q
What are photosystems?
A
- composed of a protein complex called the reaction center
- surrounded by several light-harvesting complexes
- sit in the thylakoid membrane and contain pigments
- pigments within the photosystem can absorb light, excite electrons, and pass those electrons through the photosystem
- convert light energy into chemical energy in the form of an excited electron
- review diagram**
9
Q
What is the ETC?
A
- electron transport chain
- a set of increasing strength of electron acceptors
- allows energy from excited electrons to be converted into a proton gradient and released in small discrete steps
- exists between photosystem 2 and 1
- excited electron is passed down the ETC and releases energy from the redox reactions that are used to pump H+ into the thylakoid lumen
- excited electron from photosystem one is the used to reduce NADP+
10
Q
What is chemiosmosis?
A
- formation of ATP in photosynthesis using ATP synthase powered by a [H+] gradient
- in photosynthesis = photophosphorylation
- in cellular respiration = oxidative phosphorylation
11
Q
What is ATP synthase?
A
- an enzyme complex that couples an endergonic reaction with an exergonic process
12
Q
What is NADPH?
A
- an electron carrier, sources of energy because they can reduce molecules
- carries electrons between redox reactions (from light reactions to Calvin cycle)
13
Q
What is the Calvin Cycle or Dark Reactions?
A
- uses energy from light reactions (ATP and NADPH) to convert carbon dioxide to sugar
14
Q
What is the point of dark reactions?
A
- fix carbon
- “fixation” is the conversion of an atmospheric nutrient to organic form = highly endergonic
- anabolic
15
Q
What are the three phases of the Calvin Cycle?
A
1) Carbon Fixation
2) Reduction
3) Regeneration
