[8] Vocabulary - Photosynthesis

Question 1

absorption spectrum

Answer 1

the range of a pigment’s ability to absorb various wavelengths of light; also a graph of such a range

Question 2

action spectrum

Answer 2

a graph that profiles the relative effectiveness of different wavelengths of radiation in driving a particular process

Question 3

autotroph

Answer 3

an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms. Autotrophs use energy from the sun or from oxidation of inorganic substances to make organic molecule from inorganic ones.

Question 4

C3 plants

Answer 4

a plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a three-carbon compound as the first stable intermediate

Question 5

C4 plants

Answer 5

a plant in which the Calvin cycle is preceded by reactions that incorporate CO2 into a four-carbon compound, the end product of which supplies CO2 for the Calvin cycle

Question 6

Calvin cycle

Answer 6

the second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate

Question 7

CAM plants

Answer 7

a plant that uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. Im this process, carbon dioxide entering open stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day, when stomata are closed

Question 8

carbon fixation

Answer 8

the initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism

Question 9

carotenoid

Answer 9

an accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.

Question 10

chlorophyll

Answer 10

a green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Chlorophyll A participates directly in the light reactions, which convert solar energy to chemical energy.

Question 11

chlorophyll A

Answer 11

a photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy

Question 12

chlorophyll B

Answer 12

an accessory photosynthetic pigment that transfers energy to chlorophyll A

Question 13

chloroplast

Answer 13

an organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water

Question 14

crassulacean acid metabolism (CAM)

Answer 14

an adaptation for photosynthesis in arid conditions, first discovered in the family Crassulaceae. In this process, a plant takes up CO2 at night when stomata are open and incorporates it into a variety of organic acids; during the day, when stomata are closed, CO2 is released from the organic acids for use in the Calvin cycle

Question 15

glyceraledehyde 3-phosphate (G3P)

Answer 15

a three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis

Question 16

heterotroph

Answer 16

an organism that obtains organic food molecules by eating other organisms or substances derived from them

Question 17

light reactions

Answer 17

the first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on the membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.

Question 18

light-harvesting complex

Answer 18

a complex of proteins associated with pigment molecules (including chlorophyll A, chlorophyll B, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem

Question 19

linear electron flow

Answer 19

a route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, ANDPH, and O2. The net electron flow is from H20 to NADP+

Question 20

mesophyll

Answer 20

Leaf cells specialized for photosynthesis. In C3 and CAM plants, mesophyll cells are located between the upper and lower epidermis; in C4 plants, they are located between the bundle-sheath cells and the epidermis

Question 21

NADP+

Answer 21

the oxidized form of nicotinamide adenine dinucleotide phosphate, an electron carrier that can accept electrons, becoming NADPH. NADPH temporarily stores energized electrons produced during light reactions.

Question 22

NADPH

Answer 22

the reduced form of nicotinamide adenine dinucleotide phosphate, which temporarily stores energized electrons produced during the light reactions. NADPH acts as “reducing power” that can be passed along to an electron accept, reducing it.

Question 23

photon

Answer 23

a quantum, or discrete quantity, of light energy that behaves as if it were a particle

Question 24

photophosphorylation

Answer 24

the process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certian prokaryotes during the light reactions of photosynthesis

Question 25

photorespiration

Answer 25

a metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output. Photorespiration generally occurs on hot, dry, bright days, when the stomata close and the O2/CO2 ratio in the leaf increases, favoring the binding of O2 rather than CO2 by rubisco.

Question 26

photosynthesis

Answer 26

the conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes

Question 27

photosystem

Answer 27

a light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.

Question 28

photosystem I

Answer 28

one of two light-capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll A at its reaction center

Question 29

photosystem II

Answer 29

one of two light-capturing units in a chloroplast’s thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P680 chlorophyll A at it’s reaction center

Question 30

primary electron acceptor

Answer 30

In the thylakoid membrane of a the membrane of some prokaryotes, a specialized molecule that shares the reaction-center complex with a pair of chlorophyll a molecules and that accepts an electron from them.

Question 31

reaction-center complex

Answer 31

a complex of proteins associated with a special pair of chlorophyll A molecules and a primary electron acceptor. Located centrally in a photosystem, this triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.

Question 32

reduction

Answer 32

the complete or partial addition of electrons to a substance involved in a redox reaction

Question 33

rubisco

Answer 33

ribulose bisphosphate (RuBP) carboxylase-oxygenase, the enzyme that normally catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP). When excess O2 is present or CO2 levels are low, rubisco can bind oxygen, resulting in photorespiration

Question 34

spectrophotometer

Answer 34

an instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution

Question 35

stomata

Answer 35

a microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant

Question 36

stroma

Answer 36

the dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water

Question 37

electromagnetic spectrum

Answer 37

The entire spectrum of electromagnetic radiation, ranging in wavelength from less than a nanometer to more than a kilometer.

Question 38

thylakoid

Answer 38

a flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular machinery used to convert light energy to chemical energy.

Question 39

visible light

Answer 39

the portion of the electromagnetic spectrum that can be detected as various colors by the human eye, ranging in wavelength from about 380nm to about 750nm

Question 40

wavelength

Answer 40

the distance between crests of waves, such as those of the electromagnetic spectrum