Photosynthesis (chapter 7)

Question 1

define autotroph

Answer 1

an organism that makes its own food (often through photosynthesis) i.e. plants, algae, and numerous bacteria

Question 2

define heterotroph

Answer 2

an organism that cannot make its own organic food molecules. must consume or decompose other organisms and their organic food products

Question 3

equation for photosynthesis

Answer 3

6 CO2+ 6 H20+light —-> glucose (C6H12O6) + 6 O2

Question 4

what becomes of the CO2 by the end of photosynthesis

Answer 4

the C becomes fixed (reduced) in glucose (C6H12O6). the O goes into glucose

Question 5

what becomes of the H2O by the end of photosynthesis

Answer 5

it is oxidized and is released as O2. the H’s go into glucose

Question 6

how is the O2 gas produced in photosynthesis

Answer 6

by splitting the water

Question 7

what are the two main parts of photosynthesis

Answer 7

light reactions and Calvin cycle

Question 8

explain the processes of the light reaction (generally)

Answer 8

light energy is converted to split H2O into H+ and O2. the H+ is added to NADP+ making NADPH. also generates some ATP from ADP

Question 9

where is does the light reaction take place

Answer 9

in the thylakoids

Question 10

explain the process of the Calvin cycle (generally)

Answer 10

assembles sugars from CO2 and the energy-rich products from the light reaction through carbon fixation. after that it makes more sugars through reduction

Question 11

where does the Calvin cycle take place

Answer 11

the stroma

Question 12

how is light energy converted to the energy of excited electrons, and what are the roles of photosystem II, photosystem I, and chlorophyll in this process

Answer 12

pigment absorbs photons which excite the electrons in the pigment, these excited electrons are transferred to other pigment molecules, until it reaches a pair of special chlorophyll molecules that can pass the energy onto a neighboring molecule

Question 13

how are pigments is involved in photosynthesis

Answer 13

the pigments absorb the visible light in the chloroplast. for example chlorophyll a is green because it can’t absorb green light as well

Question 14

what is water’s role in light reactions

Answer 14

the water is oxidized and its H’s are passed from photosystem II to photosystem I to replace the electrons lost. O’s just become O2 and are released

Question 15

what are the products of light reaction

Answer 15

ATP, NADPH, O2

Question 16

how is ATP produced in the light reaction

Answer 16

in the stroma there is a low concentration of H+, while in the thylakoid space there is a high concentration of H+. this means there is a proton gradient. the electron transport chain (using the sun’s energy to fuel it) pumps the H+ against the gradient. photosystem I causes the photophosphorylation of NADP+ (NADP+ is the final electron acceptor). the force of the concentration gradient forces the H+ through ATP synthase, creating ATP with that energy

Question 17

where are the high energy products of light reactions

Answer 17

in the stroma, so they can be used to fuel the Calvin cycle

Question 18

describe the Calvin cycle

Answer 18

3 CO2 and 5 RuBP go through the protein rubisco to make 6 3-PGA. 6 ATP and 6 NADPH are oxidized to give enough energy so the 6 3-PGA become 6 G3P. 1 G3P leaves the Calvin cycle at its product. the rest are used to regenerate the store of RuBP

Question 19

define carbon fixation

Answer 19

when C from the atmosphere is incorporated into organic compounds

Question 20

how does photosynthesis moderate climate change

Answer 20

while a lot of CO2 that’s absorbed is just reemitted, a significant portion of it stays trapped in the plant. also biofuels could be used to make a cycle of CO2 (not introducing any new CO2 to environment like the burning of fossil fuels)