Chapter 10 - Photosynthesis

Question 1

photosynthesis

Answer 1

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

Question 2

autotroph

Answer 2

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 molecules from inorganic ones.

Question 3

heterotroph

Answer 3

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

Question 4

mesophyll

Answer 4

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 5

stoma

Answer 5

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 6

stroma

Answer 6

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 7

thylakoid

Answer 7

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

Question 8

chlorophyll

Answer 8

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 9

light reactions

Answer 9

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 membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.

Question 10

Calvin cycle

Answer 10

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 11

NADP+

Answer 11

Nicotinamide adenine dinucleotide phosphate, an electron acceptor that, as NADPH, temporarily stores energized electrons produced during the light reactions.

Question 12

photophosphorylation

Answer 12

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 certain prokaryotes during the light reactions of photosynthesis.

Question 13

carbon fixation

Answer 13

The initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism (a plant, another photosynthetic organism, or a chemoautotrophic prokaryote).

Question 14

wavelength

Answer 14

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

Question 15

electromagnetic spectrum

Answer 15

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

Question 16

visible light

Answer 16

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

Question 17

photon

Answer 17

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

Question 18

spectrophotometer

Answer 18

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

Question 19

absorption spectrum

Answer 19

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

Question 20

chlorophyll a

Answer 20

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

Question 21

action spectrum

Answer 21

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

Question 22

chlorophyll b

Answer 22

An accessory photosynthetic pigment that transfers energy to chlorophyll a.

Question 23

carotenoids

Answer 23

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 24

photosystem

Answer 24

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 25

reaction-center complex

Answer 25

A complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex 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 26

light-harvesting complex

Answer 26

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 27

primary electron acceptor

Answer 27

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

Question 28

photosystem II (PS II)

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 P680 chlorophyll a at its reaction center.

Question 29

photosystem I (PS I)

Answer 29

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

Question 30

linear electron flow

Answer 30

A route of electron flow during the light reactions of photosynthesis that involves both photosystems (I and II) and produces ATP, NADPH, and O2. The net electron flow is from H2O to NADP+.

Question 31

cyclic electron flow

Answer 31

A route of electron flow during the light reactions of photosynthesis that involves only photosystem I and that produces ATP but not NADPH or O2.

Question 32

glyceraldehyde 3-phosphate (G3P)

Answer 32

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

Question 33

rubisco

Answer 33

Ribulose biphosphate (RuBP) carboxylase, the enzyme that catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP).