chapter 10: photosynthesis

Question 1

what is an autotroph?

Answer 1

an organism that produces its own food using light, water, or carbon dioxide

Question 2

what is a heterotroph?

Answer 2

an organism that cannot produce its own food, instead they eat other plants/animals for energy

Question 3

how did fossil fuels develop?

Answer 3

they formed from remains of organisms that died hundreds of millions of years ago

Question 4

what is photosynthesis and why is it important?

Answer 4

the conversion of light energy to chemical energy that is stored in sugars, photosynthesis is important because it is critical or the existence of the vast majority on life on Earth

Question 5

what are the parts of a leaf? where does gas exchange occur?

Answer 5

gas exchange occurs on the stomata

Question 6

what are the parts of a chloroplast?

Answer 6

outer membrane, inner membrane, thylakoid membrane, grana, lumen, and stroma

Question 7

what is CO2 being reduced to during the process of photosynthesis?

Answer 7

sugars (glucose)

Question 8

why is photosynthesis considered an endergonic reaction?

Answer 8

photosynthesis is endergonic because plants cannot initiate the process until they absorb light energy (energy is needed)

Question 9

what are the two major phases of photosynthesis? what comes in and goes out?

Answer 9

• light reactions: inputs are sunlight, water, ADP, NADP+ and its outputs are ATP, NADPH, and O2
• dark reactions (Calvin cycle): inputs are ATP, NADPH, and CO2 and its outputs are ADP, G3P, and NADP+

Question 10

what is the source of electrons in the light reaction? what is the waste product?

Answer 10

water provides electrons for light reactions, oxygen is the waste product

Question 11

what is NADP+ and NADPH?

Answer 11

NADP+: the oxidized form that acts as an electron carrier
NADPH: the reduced form that temporarily stores energized electrons produced during the light reactions

Question 12

which phase of photosynthesis does not require light?

Answer 12

Calvin cycle (dark reactions)

Question 13

what is visible light?

Answer 13

the portion of the electromagnetic spectrum that can be detected by the human eye

Question 14

what is a photon?

Answer 14

light energy that behaves as if it were a particle

Question 15

what is a pigment?

Answer 15

substances that absorb visible light

Question 16

why do plants look green to our eye?

Answer 16

light absorbs every other color and only reflects green out

Question 17

ground state vs excited state

Answer 17

• when electrons are in a ground state, they have lower energy and are more stable
• when electrons are in a excited state, they have more energy and are not stable

Question 18

how does a pigment molecule excite an electron?

Answer 18

when electrons in the pigment absorb energy, the energy move the electrons to an excited state

Question 19

what is a photosystem?

Answer 19

light capturing units, consisting of a reaction center complex surrounded by numerous light-harvesting complexes

Question 19

what is photosystem II?

Answer 19

a light capturing unit in a chloroplast’s thylakoid membrane (contains two molecules of P680 chlorophyll a)

Question 20

what is photosystem I?

Answer 20

a light capturing unit in a chloroplasts thylakoid membrane (contains two molecules of P700 chlorophyll a)

Question 21

where does the light reaction take place in chloroplasts?

Answer 21

the thylakoid

Question 22

what is noncyclic (linear) electron flow? what is produced?

Answer 22

• a route on electron flow during the light reactions of photosynthesis that involves both photosystems I and II
• produces ATP and NADPH

Question 23

how does energy move around from electron to electron in a photosystem?

Answer 23

through the electron transport chain

Question 24

what is a reaction center?

Answer 24

a complex of proteins associated with a pair of chlorophyll a molecules and a primary electron acceptor

Question 25

what is cyclic electron flow? what is produced?

Answer 25

• a route of electron flow during the light reactions of photosynthesis that involves only photosystem I
• produces ATP

Question 26

what is the main difference between linear electron flow and cyclic electron flow?

Answer 26

noncyclic electron flow uses both photosystems, while cyclic electron flow only uses photosystem I

Question 27

what is the point of the Calvin cycle?

Answer 27

the main function of the Calvin cycle is carbon fixation, making simple sugars (3 carbon sugar) from carbon dioxide and water

Question 28

what are the 3 phases of the Calvin cycle?

Answer 28

fixation, reduction, regeneration

Question 29

what is carbon fixation?

Answer 29

the process in which CO2 is incorporated into organic compounds by an autotrophic organism

Question 30

what comes into the Calvin cycle? what comes out of the Calvin cycle?

Answer 30

• CO2, ATP, and NADPH
• a 3 carbon sugar (G3P), ADP, and NADP+

Question 31

what is G3P?

Answer 31

a 3 carbon carbohydrate that is the direct product of the Calvin cycle

Question 32

where does the Calvin cycle take place?

Answer 32

the stroma