Chapter 10 - Photosynthesis Flashcards
autotrophs
“self-feeders” (ex: plants), producers, they generate food from non-living sources
photoautotrophs
organisms that use light energy to synthesize organic compounds (unicellular organisms)
chemoautotrophs
organisms that use chemical energy/inorganic energy sources (ex: H2S, CO2, etc.) to synthesize organic compounds
heterotrophs
consumers, they live on compounds produced by other organisms
photosynthesis
captures light energy, stores the energy in stable forms (ex: light => carbs)
cellular respiration
oxygen is used as energy to make sugar/food
converts energy into usable forms (carbs => ATP)
chloroplasts
sites of photosynthesis
has three compartments: inter-membrane space, stroma, and thylakoid space
the outer membrane is freely permeable to molecules while the inner membrane is selectively permeable
What two steps are involved in photosynthesis?
1.) light reaction (photo) = happens in the thylakoid, reactions convert solar energy to chemical energy (stable to unstable)
2.) dark reaction (synthesis) = the Calvin Cycle, happens in the stroma, reactions convert unstable chemical energy to stable chemical energy
What happens in the light reaction of photosynthesis?
energy from the sun stored in the form of ATP (light energy) is converted into chemical energy
chemical energy + broken water molecules are used to produce ATP and NADPH (both energy-storing molecules)
What happens in the “dark” reaction of photosynthesis? The Calvin Cycle.
carbon enters a plant through the stomata and the Calvin cycle turns it into sugar
steps:
1.) carbon fixation = the enzyme Rubisco takes the carbon that is in the plant and attaches RuBP onto it to create a 6-carbon molecule, hence turning it into an organic molecule
2.) reduction = requires ATP and NADPH which we get from the light-dependent reaction (redox reaction) reduces carbon (carbon gains electrons) which oxidizes NADPH
3.)
What happens in the “dark” reaction of photosynthesis? The Calvin Cycle.
carbon enters a plant through the stomata and the Calvin cycle turns it into sugar
steps:
1.) carbon fixation = the enzyme Rubisco takes the carbon that is in the plant and attaches RuBP onto it to create a 6-carbon molecule, hence turning it into an organic molecule
2.) reduction = requires ATP and NADPH which we get from the light-dependent reaction (redox reaction) reduces carbon (carbon gains electrons) which oxidizes NADPH (NADPH loses electrons) and turns it into NADP+
=> and the whole process makes G3P
3.) regeneration = changing 5 3-carbon molecules into 3 5-carbon molecules (basically just rearranging the carbons so that it can regenerate RuBP, continuing the cycle)
Why is G3P important?
it is the prime end product of photosynthesis, photosynthesis won’t occur without G3P
it is also the source of carbohydrates that plants require for both cell maintenance and cell growth
What is ADP?
when ATP splits off one of its 3 phosphate molecules it makes ADP
pigments
molecules that absorb light (ex: chlorophyll is a green pigment)
Why do various pigments exist in chloroplasts?
different pigments absorb light of different wavelengths so having different pigments means that the plant can absorb more energy
What are the various pigments that exist in chloroplasts?
chlorophyll a and chlorophyll b
color
light(s) that aren’t absorbed (ex: a plant is green because it absorbs every color except green)
What are the various pigments that exist in chloroplasts?
chlorophyll a and chlorophyll b
photosystem
it is a protein + pigment complex in the thylakoid membrane that is used to funnel light energy into chlorophyll
(excites e-)
What are the 2 photosystems that convert light energy into electron movement?
photosystem II (PSII) and photosystem I (PSI) (both are protein complexes)
PSII (photo) = starts the initial reaction of photosynthesis, a water-splitting photosystem that produces O2 and replenishes electrons
PSI (synthesis) = NADPH-producing photosystem, it transfers excited electrons to NADP+ in order to make NADPH so NADPH (which is an electron transport carrier molecule) can transport electrons
PSI => transfers e- => NADP+ = makes NADPH = NADPH high energy electron transport carrier (so it can carry on its role which is to transfer e- to other molecules)
(photosystems related) linear electron flow
H2O => PSII => ETC => PSI => NADPH
(photosystems related) cyclic e- flow
PSI => ETC => PSI
only occurs when 1 photosystem is present (ex: purple bacteria)
electron transport chain (ETC)
generates H+ electrochemical gradient (PMF = proton motive force), is used to make ATP, leads to oxidative phosphorylation
4 series of protein complexes that are involved in both photosynthesis and cellular respiration
pump H+ = stroma to thylakoid
ATP synthase
a protein complex that couples H+ diffusion to ADP phosphorylation
converts proton motive force (PMF) to ATP production
What are the steps to glucose oxidation?
1.) glycolysis = “sugar splitting”, happens in the cytosol
2.) pyruvate oxidation = decarboxylation, oxidation, and attach to CoA, happens in the matrix
=> oxidizes pyruvate (losing electrons) to create acetyl CoA
3.) citric acid = completes the oxidation of organic fuel
2acetyl-CoA + 2ADP + 6NAD+ + 2FAD => 4CO2 + 2ATP + 6NADH + 2FADH2
4.) electron transport chain = “cash in” electrons that were removed during glycolysis, pyruvate oxidation, and the citric acid cycle to form ATP
H+ increase = intermembrane creates proton motive force
proton motive force (PMF)
the electrical potential and concentration gradient of protons (H+) across a biological membrane, which is used by cells to produce ATP and drive other cellular processes
part of ETC
substrate-level phosphorylation
when a phosphoryl group is transferred from a substrate to ADP or GDP to form ATP or GTP coupled with a release of free energy
“direct ATP” production
occurs in the cytoplasm, glycolysis and citric acid cycle
