3-3 Vocab

Question 1

Stroma

Answer 1

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 2

Chlorophyll

Answer 2

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 3

Rubisco

Answer 3

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

Question 4

Calvin Cycle

Answer 4

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

Question 5

Heterotrophs

Answer 5

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

Question 6

Thylakoids

Answer 6

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 7

Photosystem II

Answer 7

(PS II) 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 8

Photosystem I

Answer 8

(PS I) 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 9

Chloroplasts

Answer 9

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 10

CAM Plants

Answer 10

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

Question 11

Stomata

Answer 11

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 12

Autotrophs

Answer 12

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 13

C3 Plants

Answer 13

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

Question 14

C4 Plants

Answer 14

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

Question 15

Photorespiration

Answer 15

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 ratio of oxygen to carbon dioxide in the leaf increases, favoring the binding of oxygen rather than carbon dioxide by rubisco

Question 16

Primary Electron Acceptor

Answer 16

In the thylakoid membrane of a chloroplast or in 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 17

Photophosphorylation

Answer 17

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 18

Glyceraldehyde 3-Phosphate

Answer 18

(G3P) A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis

Question 19

Photons

Answer 19

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

Question 20

Photosynthesis

Answer 20

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