Chapter 7: Photosynthesis: Using Light to Make Food

Question 1

autotroph

Answer 1

An organism that makes its own food (often by photosynthesis), thereby sustaining itself without eating other organisms or their molecules. Plants, algae, and numerous bacteria are autotrophs.

Question 2

C3 plant

Answer 2

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 3

C4 plant

Answer 3

A plant that prefaces the Calvin cycle with reactions that incorporate CO2 into four-carbon compounds, the end product of which supplies CO2 for the Calvin cycle.

Question 4

Calvin cycle/reactions

Answer 4

The second of two stages of photosynthesis; a cyclic series of chemical reactions that occur in the stroma of a chloroplast, using the carbon in CO2 and the ATP and NADPH produced by the light reactions to make the energy-rich sugar molecule G3P.

Question 5

CAM plant

Answer 5

A plant that uses an adaptation for photosynthesis in arid conditions in which 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 6

carbon fixation

Answer 6

The incorporation of carbon from atmospheric CO2 into the carbon in organic compounds. During photosynthesis in a C3 plant, carbon is fixed into a three-carbon sugar as it enters the Calvin cycle. In C4 and CAM plants, carbon is fixed into a four-carbon sugar.

Question 7

chlorophyll

Answer 7

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

Question 8

electromagnetic spectrum

Answer 8

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

Question 9

global climate change

Answer 9

Increase in temperature and change in weather patterns all around the planet, due mostly to increasing ­atmospheric CO2 levels from the burning of fossil fuels. The ­increase in temperature, called global warming, is a major aspect of global climate change.

Question 10

granum

Answer 10

(plural, grana) A stack of hollow disks formed of thylakoid membrane in a chloroplast. Grana are the sites where light energy is trapped by chlorophyll and converted to chemical energy during the light reactions of photosynthesis.

Question 11

greenhouse effect

Answer 11

The warming of the atmosphere caused by CO2, CH4, and other gases that absorb infrared radiation and slow its escape from Earth’s surface.

Question 12

light-dependent reactions

Answer 12

The first of two stages in photosynthesis; the steps in which solar energy is absorbed and converted to chemical energy in the form of ATP and NADPH. The light reactions power the sugar-producing Calvin cycle but produce no sugar themselves.

Question 13

mesophyll

Answer 13

The green tissue in the interior of a leaf; a leaf’s ground tissue system; the main site of photosynthesis.

Question 14

photoautotroph

Answer 14

An organism that obtains energy from sunlight and carbon from CO2 by photosynthesis.

Question 15

photon

Answer 15

A fixed quantity of light energy. The shorter the wavelength of light, the greater the energy of a photon.

Question 16

photophosphorylation

Answer 16

The production of ATP by chemiosmosis during the light reactions of photosynthesis.

Question 17

photorespiration

Answer 17

In a plant cell, the breakdown of a two-carbon compound produced by the Calvin cycle. The Calvin cycle produces the two-carbon compound, instead of its usual three-carbon product G3P, when leaf cells fix O2, instead of CO2. Photorespiration produces no sugar molecules or ATP.

Question 18

photosynthesis

Answer 18

The process by which plants, autotrophic protists, and some bacteria use light energy to make sugars and other organic food molecules from carbon dioxide and water.

Question 19

photosystem

Answer 19

A light-capturing unit of a chloroplast’s thylakoid membrane, consisting of a reaction center complex surrounded by numerous light-harvesting complexes.

Question 20

producer

Answer 20

An organism that makes organic food molecules from CO2, H2O, and other inorganic raw materials: a plant, alga, or autotrophic bacterium.

Question 21

stoma

Answer 21

(plural, stomata) A pore surrounded by guard cells in the epidermis of a leaf. When stomata are open, CO2 enters a leaf, and water and O2 exit. A plant conserves water when its stomata are closed.

Question 22

stroma

Answer 22

The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water; Sugars are made in the stroma by the enzymes of the Calvin cycle.

Question 23

thylakoid

Answer 23

One of a number of disk-shaped membranous sacs inside a chloroplast. Thylakoid membranes contain chlorophyll and the enzymes of the light reactions of photosynthesis. A stack of thylakoids is called a granum.

Question 24

wavelength

Answer 24

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