Photosynthesis Key Terms

Question 1

absorption spectrum

Answer 1

range of wavelengths of electromagnetic radiation absorbed by a given substance

Question 2

antenna protein

Answer 2

pigment molecule that directly absorbs light and transfers the energy absorbed to other pigment molecules

Question 3

calvin cycle

Answer 3

light-independent reactions of photosynthesis that convert carbon dioxide from the atmosphere into carbohydrates using the energy and reducing power of ATP and NADPH

Question 4

carbon fixation

Answer 4

process of converting inorganic CO2 gas into organic compounds

Question 5

carotenoid

Answer 5

photosynthetic pigment that functions to dispose of excess energy

Question 6

chemoautotroph

Answer 6

organism that can build organic molecules using energy derived from inorganic chemicals instead of sunlight

Question 7

chlorophyll a

Answer 7

form of chlorophyll that absorbs violet-blue and red light and consequently has a bluish-green color; the only pigment molecule that performs the photochemistry by getting excited and losing an electron to the electron transport chain

Question 8

chlorophyll b

Answer 8

accessory pigment that absorbs blue and red-orange light and consequently has a yellowish-green tint

Question 9

chloroplast

Answer 9

organelle in which photosynthesis takes place

Question 10

cytochrome complex

Answer 10

group of reversibly oxidizable and reducible proteins that forms part of the electron transport chain between photosystem II and photosystem I

Question 11

electromagnetic spectrum

Answer 11

range of all possible frequencies of radiation

Question 12

electron transport chain

Answer 12

group of proteins between PSII and PSI that pass energized electrons and use the energy released by the electrons to move hydrogen ions against their concentration gradient into the thylakoid lumen

Question 13

granum

Answer 13

stack of thylakoids located inside a chloroplast

Question 14

heterotroph

Answer 14

organism that consumes organic substances or other organisms for food

Question 15

light harvesting complex

Answer 15

complex that passes energy from sunlight to the reaction center in each photosystem; it consists of multiple antenna proteins that contain a mixture of 300–400 chlorophyll a and b molecules as well as other pigments like carotenoids

Question 16

light-dependent reaction

Answer 16

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

Question 17

light-independent reaction

Answer 17

second stage of photosynthesis, though which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH

Question 18

mesophyll

Answer 18

middle layer of chlorophyll-rich cells in a leaf

Question 19

photoact

Answer 19

ejection of an electron from a reaction center using the energy of an absorbed photon

Question 20

photoautotroph

Answer 20

organism capable of producing its own organic compounds from sunlight

Question 21

photon

Answer 21

distinct quantity or “packet” of light energy

Question 22

photosystem

Answer 22

group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy

Question 23

photosystem I

Answer 23

integral pigment and protein complex in thylakoid membranes that uses light energy to transport electrons from plastocyanin to NADP+ (which becomes reduced to NADPH in the process)

Question 24

photosystem II

Answer 24

integral protein and pigment complex in thylakoid membranes that transports electrons from water to the electron transport chain; oxygen is a product of PSII

Question 25

pigment

Answer 25

molecule that is capable of absorbing certain wavelengths of light and reflecting others (which accounts for its color)

Question 26

primary electron acceptor

Answer 26

pigment or other organic molecule in the reaction center that accepts an energized electron from the reaction center

Question 27

reaction center

Answer 27

complex of chlorophyll molecules and other organic molecules that is assembled around a special pair of chlorophyll molecules and a primary electron acceptor; capable of undergoing oxidation and reduction

Question 28

reduction

Answer 28

gain of electron(s) by an atom or molecule

Question 29

spectrophotometer

Answer 29

instrument that can measure transmitted light and compute the absorption

Question 30

stoma

Answer 30

opening that regulates gas exchange and water evaporation between leaves and the environment, typically situated on the underside of leaves

Question 31

stroma

Answer 31

fluid-filled space surrounding the grana inside a chloroplast where the light-independent reactions of photosynthesis take place

Question 32

thylakoid

Answer 32

disc-shaped, membrane-bound structure inside a chloroplast where the light-dependent reactions of photosynthesis take place; stacks of thylakoids are called grana

Question 33

thylakoid lumen

Answer 33

aqueous space bound by a thylakoid membrane where protons accumulate during light-driven electron transport

Question 34

wavelength

Answer 34

distance between consecutive points of equal position (two crests or two troughs) of a wave in a graphic representation; inversely proportional to the energy of the radiation