CHAPTER 10

Question 1

photosynthesis

Answer 1

energy from sunlight is captured and used to convert CO2 to more complex carbon compounds

Question 2

autotrophs

Answer 2

organisms that carry out photosynthesis

Question 3

heterotrophs

Answer 3

must consume other organisms, such as autotrophs or other heterotrophs, to obtain food

Question 4

photosynthesis formula

Answer 4

6 CO2 + 12 H2O produces
C6H12O6 + 6 O2 + 6 H2O

Question 5

How is photosynthesis a redox process?

Answer 5

-O atoms in H2O are in a reduced state; they are oxidized to O2
-C atoms in CO2 are in the oxidized state; they are reduced to a carbohydrate

Question 6

non-oxygenic photosynthesis

Answer 6

other molecules donate the protons and electrons
-PURPLE SULFUR bacteria use H2S
-GREEN SULFUR bacteria use sulfide ions, hydrogen, or ferrous iron as electron donors

Question 7

light reaction

Answer 7

converts light energy to chemical energy as ATP and NADPH

Question 8

carbon-fixation reaction

Answer 8

uses the ATP and NADPH plus CO2 to produce carbohydrates

Question 9

electromagnetic radiation

Answer 9

form of energy that defines light

Question 10

electromagnetic spectrum

Answer 10

the entire range of electromagnetic energy, or radiation

Question 11

wavelength

Answer 11

light is propagated as waves - the amount of energy is inversely proportional to this

Question 12

visible light

Answer 12

consists of wavelengths that produce colors we can see

Question 13

photons

Answer 13

light also behaves as these particles, certain molecules absorb them at a specific wavelength
WHEN IT HITS A MOLECULE, IT CAN:
-BOUNCE off - scattered or reflected
-PASS through - transmitted
- be ABSORBED, adding energy to the molecule (excited state)

Question 14

pigments

Answer 14

molecules that absorb specific wavelengths in the visible range (the major one in photosynthesis is chlorophyll a)

Question 15

spectrophotometer

Answer 15

measures a pigment’s ability to absorb various wavelengths

Question 16

chlorophyll

Answer 16

absorbs blue and red light and scatters green

Question 17

mesophyll

Answer 17

interior tissue of the leaf; where chloroplasts are mainly found (each contains 30-40 chloroplasts)

Question 18

stomata

Answer 18

microscopic pores in the leaf where CO2 enters and O2 exits

Question 19

absorption spectrum

Answer 19

plot of wavelengths absorbed by a pigment

Question 20

action spectrum

Answer 20

plot of photosynthetic rate against wavelengths of light (can be measured by the amount of O2 released)

Question 21

photosystem

Answer 21

protein complex where chlorophyll a’s hydrocarbon “tail” is anchored in, located in the thylakoid membrane (has chlorophyll b, carotenoids, and phycobilins as well)

Question 22

light-harvesting complexes

Answer 22

where the pigment molecules are arranged (also called antenna systems)

Question 23

reaction center

Answer 23

what several complexes surround in the photosystem; where light energy is converted to chemical energy

Question 24

redox reaction with chlorophyll

Answer 24

chlorophyll gets oxidized to ChI+ and the acceptor molecule is reduced; the electron acceptor is the first in a chain of carriers in the thylakoid membrane; the final electron acceptor is NADP+, which gets reduced:
NADP+ + H+ + 2e- produces NADPH

Question 25

noncyclic electron transport

Answer 25

uses two photosystems

Question 26

photosystem I

Answer 26

has P700 chlorophyll - absorbs best at 700 nm; an excited electron from the ChI* reduces an acceptor; the oxidized ChI+ takes an electron from the last carrier in photosystem II, the energetic electron is passed through several carriers and reduces NADP+ to NADPH

Question 27

photosystem II

Answer 27

has P680 chlorophyll - absorbs best at 680 nm; when excited chlorophyll (ChI*) gives up its electron, it is unstable, and grabs another electron form water; the water becomes oxidized; H+ from H2O and electron transport capture energy for the chemiosmotic synthesis of ATP

Question 28

cyclic electron transport

Answer 28

uses photosystem I and electron transport to produce ATP instead of NADPH; cyclic- the electron from the excited chlorophyll passes back to the same chlorophyll

Question 29

linear electron flow

Answer 29

the primary pathway, involves both photosystems and produces ATP and NADPH using light energy

Question 30

photophosphorylation

Answer 30

how ATP is formed in a chemiosmotic mechanism; H+ is transported across the thylakoid membrane into the lumen, creating an electrochemical gradient

Question 31

noncyclic photophosphorylation

Answer 31

photosystem II regains electrons by splitting water, leaving O2 gas as a by-product

Question 32

CO2 fixation

Answer 32

CO2 is reduced to carbohydrates; occurs in the stroma; energy in ATP and NADPH is used to reduce CO2

Question 33

14C radioisotope

Answer 33

Calvin and Benson used it determine the sequence of reactions in CO2 fixation; they exposed Chlorella to it, then extracted the organic compounds and separated them by paper chromatography

Question 34

3PG (3-Phosphoglycerate)

Answer 34

the first compound formed, a sugar phosphate

Question 35

Calvin cycle

Answer 35

CO2 fixation pathway; CO2 binds to 5-C RuBP, catalyzed by ribulose bisphosphate carboxylase/oxygenase (rubisco); the 6-C compound immediately breaks down into two molecules of 3PG
- CO2 to 3PG
- 3PG to G3P
- RuBP
For every turn of the cycle, one CO2 is fixed and one RuBP is regenerated
Stimulated by light
-induces pH changes in the STROMA that favors ACTIVATION of RUBISCO
-light-induced electron transport reduces DISULFIDE bonds in Calvin cycle enzymes to ACTIVATE them, via FERREDOXIN and THIOREDOXIN

Question 36

G3P (Glyceraldehyde 3-phopshate)

Answer 36

product of the Calvin cycle -some is exported to the cytoplasm and converted to glucose and fructose
-can be used in respiration or converted to sucrose and transported to other parts of the plant for energy or to build other molecules
-some is used to synthesize glucose and starch within the chloroplast

Question 37

photorespiration

Answer 37

rubisco is a CARBOXYLASE, but can also act as an OXYGENASE, adding O2 to RuBP instead of CO2
RuBP + O2 produces
phosphoglycolate + 3PG

Question 38

phosphoglycolate

Answer 38

inhibits reactions in the Calvin cycle and has to be eliminated (in a series of reactions that involves peroxisomes and mitochondria, it is converted to 3PG, which enters the Calvin cycle, but there is a loss of CO2)

Question 39

C3 plants

Answer 39

first product of CO2 fixation is 3PG (3 carbons); on hot days, photorespiration occurs; in cool conditions they don’t expend energy concentrating CO2 around rubisco

Question 40

C4 plants

Answer 40

first product of CO2 fixation is oxaloacetate (4 carbons); no photorespiration on hot days; in mesophyll cells, PEP carboxylase catalyzes the reaction of CO2 and PEP to form oxaloacetate, which is converted to malate; PEP carboxylase has no oxygenase activity and fixes CO2 even when levels are low; use energy to increase CO2; in warm, dry climates photorespiration doesn’t occur and photosynthesis rates don’t fall

Question 41

bundle sheath cells

Answer 41

malate diffuses to these, which have modified chloroplasts that concentrate CO2 around rubisco; malate is decarboxylated to pyruvate and CO2 then pyruvate moves back to mesophyll cells to regenerate PEP; the CO2 enters the Calvin cycle

Question 42

CAM (Crassulacean acid metabolism

Answer 42

stomata are open at night and closed during the day to conserve water
NIGHT: CO2 is fixed by PEP carboxylase, and malate is stored in vacuoles
DAY: malate moves to chloroplasts and is decarboxylated and the CO2 goes into the Calvin cycle

Question 43

partitioning of G3P

Answer 43

some enters glycolysis and cellular respiration or is used to make other compounds while some enters gluconeogenesis (sucrose is formed and transported to other parts of the plant)