Chapter 10: Photosynthesis

Question 1

Photosynthesis

Answer 1

• Conversion of light energy to chemical energy that is stored in sugars or other organic compounds
• Occurs in plants, algae, and certain prokaryotes

Question 2

Autotroph

Answer 2

• Organism that obtains organic food molecules without eating other organisms or substances derived from other organisms
• Use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones

Question 3

Heterotroph

Answer 3

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, located between the upper and lower epidermis
• In C4 plants, they are located between the bundle-sheath cells and the epidermis

Question 5

Stomata

Answer 5

• Microscopic pores surrounded by guard cells

- In the epidermis of leaves and stems that allow gas exchange between the environment and the interior of the plant

Question 6

Stroma

Answer 6

• Dense fluid within the chloroplast surrounding the thylakoid membrane
• Contains ribosomes and DNA
• Involved in the synthesis of organic molecules from carbon dioxide and water

Question 7

Thylakoid

Answer 7

• Flattened membrane sac inside the chloroplast

- Used to convert light energy into chemical energy

Question 8

Chlorophyll

Answer 8

Green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes

Question 9

Light Reactions

Answer 9

• First of two major stages in photosynthesis
• Comes before the Calvin Cycle
• Occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes
• Convert solar energy into the chemical energy of ATP and NADPH
• Releases oxygen

Question 10

Calvin Cycle

Answer 10

• Second of two major stages in photosynthesis

- Involves the fixation of atmospheric carbon dioxide and the reduction of fixed carbon into carbohydrate

Question 11

NADP+

Answer 11

• Nicotinamide adenine dinucleotide phosphate
• Electron acceptor
• As NADPH, temporarily stores energized electrons produced during the light reactions

Question 12

Photophosphorylation

Answer 12

Process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis

Question 13

Carbon Fixation

Answer 13

Initial incorporation of carbon from carbon dioxide into an organic compound by an autotrophic organism (i.e. plant, other photosynthetic organism, chemoautotrophic prokaryote)

Question 14

Wavelength

Answer 14

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

Question 15

Electromagnetic Spectrum

Answer 15

• Entire spectrum of electromagnetic radiation

- Ranges in wavelength from less than a nanometer to more than a kilometer

Question 16

Visible Light

Answer 16

• Portion of the electromagnetic spectrum that can be detected as various colors by the human eye
• Ranges in wavelength from about 380 nm to about 750 nm

Question 17

Photon

Answer 17

Quantum/ discrete quantity of light energy that behaves as if it were a particle

Question 18

Spectrophotometer

Answer 18

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

Question 19

Absorption Spectrum

Answer 19

• 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

Photosynthetic pigment that participates directly in the light reactions

Question 21

Chlorophyll b

Answer 21

Accessory photosynthetic pigment that transfers energy to chlorophyll a

Question 22

Carotenoid

Answer 22

• Accessory pigment in the chloroplasts of plants
• Either yellow or orange
• Absorbs wavelengths of light that chlorophyll cannot
• Broaden the spectrum of colors that can drive photosynthesis

Question 23

Photosystem

Answer 23

• A light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes
• Consists of a reaction-center complex surrounded by numerous light-harvesting complexes
• Two types: I and II
• Absorb light best at different wavelengths

Question 24

Reaction-Center Complex

Answer 24

• Complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor
• Located centrally in a photosystem
• 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 25

Light-Harvesting Complex

Answer 25

- Complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) - Captures light energy and transfers it to reaction-center pigments in a photosystem

Question 26

Primary Electron Acceptor

Answer 26

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

Question 27

Photosystem II (PS II)

Answer 27

- One of two light-capturing units in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes - Occurs first - Has two molecules of P680 chlorophyll a at its reaction center

Question 28

Photosystem I (PS I)

Answer 28

- Light capturing unit in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes - Happens second - Has two molecules of P700 chlorophyll a at its reaction center

Question 29

Linear Electron Flow

Answer 29

- Route of electron flow during the light reactions of photosynthesis --Involves both photosystems (I and II) - Produces ATP, NADPH, and O2 - Net electron flow from H2O to NADP+

Question 30

Cyclic Electron Flow

Answer 30

- Route of electron flow during the light reactions of photosynthesis - Involves only photosystem I - Produces ATP but not NADPH or oxygen

Question 31

Glyceraldehyde 3-phosphate (G3P)

Answer 31

- Three-carbon carbohydrate - Direct product of the Calvin Cycle - An intermediate in glycolysis

Question 32

Rubisco

Answer 32

- Ribulose carboxylase - Enzyme that catalyzes the 1st step of the Calvin cycle (addition of CO2 to RuBP, or ribulose bisphosphate) - Can bind to oxygen when excess oxygen is present or carbon dioxide levels are low

Question 33

C3 Plant

Answer 33

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

Question 34

Photorespiration

Answer 34

- Metabolic pathway - Consumes oxygen - Releases carbon dioxide - Doesn't generate ATP - Decreases photosynthetic output - Generally on hot, dry, and bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide

Question 35

C4 Plant

Answer 35

Plant in which the Calvin cycle comes after reactions that incorporate CO2 into a four-carbon compound, the end product supplying CO2 for Calvin cycle

Question 36

Bundle-Sheath Cell

Answer 36

In C4 plants, a type of photosynthetic cell arranged into tightly packed sheaths around the veins of a leaf

Question 37

PEP Carboxylase

Answer 37

- Enzyme that adds CO2 to phosphoenolpyruvate (PEP) to form oxaloacetate in C4 plants - Acts prior to photosynthesis

Question 38

Crassulacean Acid Metabolism (CAM)

Answer 38

- Adaptation for photosynthesis in arid conditions - First discovered in the family Crassulaceae - Plant takes up CO2 and incorporates it into a variety of organic acids at night when stomata are open - During the day, CO2 is released from organic acids for use in the Calvin cycle while stomata are closed

Question 39

CAM Plant

Answer 39

-Plant that uses crassulacean acid metabolism (adaptation for photosynthesis in arid conditions)