chapter 7: photosynthesis

Question 1

What is a chloroplast

Answer 1

Green portion
Mesophyll tissue
Chloroplast: organelle in algae & plants with chlorophyll-containing membranous thylakoids
Produces glucose

Question 2

What is the role of NADP+/NADPH

Answer 2

-Electrons are needed to reduce CO2
-Carried by NADP+ coenzyme of oxidation-reduction reaction
-Water splits during photosynthesis
-Oxygen is released
-Hydrogen atoms & electrons taken up by NADP+
-NAPDH reduces CO2 to carbohydrate

Question 3

how do plants convert solar energy

Answer 3

Wavelength & energy contents
Most radiation reaching Earth is within the visible-light range, the rest is filtered out
-ozone layer
Organisms evolved to use them

Question 4

what is the absorption spectrum

Answer 4

For photosynthetic pigments, a graph of how much solar radiation is absorbed versus the wavelength of light
Plants contain chlorophylls a and b

Question 5

what are carotenoids

Answer 5

accessory photosynthetic pigment of plants & algae often yellow or orange in color

Question 6

what is the photosystem

Answer 6

consists of pigment complex & electron acceptor molecules within thylakoid

Question 7

how do electrons flow in light reactions

Answer 7

-Two photosystems: photosystem I (PS I) and photosystem II (PS II)
-Electrons typically follow noncyclic pathway -> begin with PS II

Question 8

what are the ways plants fix carbon dioxide

Answer 8

1. CO2 fixation
2. CO2 reduction
3. Regeneration of RuBP

Question 9

how does co2 fixation work

Answer 9

CO2 is attached to 5-carbon RuBP by the enzyme RuBP carboxylase
Results in 6-carbon molecule
Splits into two 3-carbon molecules (3PG)
Accelerated by RuBP carboxylase (Rubisco)

Question 10

how does co2 reduction work

Answer 10

Each two 3PC undergoes reaction to G3P two steps
1. Energy is required in the form of ATP, which is hydrolyzed to ADP
2. Substrate BPG is reduced, while the coenzyme NADPH is oxidized

Question 11

how does the regeneration of RuBP work

Answer 11

Calvin cycle reactions multiplied by 3
Three turns to allow one G3P molecule to exit
Takes five G3P to reform three RuBP
ATP

Question 12

what is the importance of G3P

Answer 12

-most important molecule to sustain for life
-molecule used to make glucose, phosphate groups, synthesize fatty acids, produce amino acids

Question 13

what are C3 plants

Answer 13

C3 plant: plant that fixes carbon dioxide via the Calvin cycle; the first stable product of C3 photosynthesis is a 3-carbon compound

Question 14

what is photorespiration

Answer 14

Photorespiration: series of reactions that occurs in plants when carbon dioxide levels are depleted but oxygen continues to accumulate; enzyme RuBP carboxylase fixes oxygen instead of carbon dioxide
-stomata close to conserve water
-Disadvantageous ☹
-3PG produced at reduced rate
-Much higher metabolic cost

Question 15

how does C4 photosynthesis work

Answer 15

Fix CO2 to PEP (3 carbon molecule) using enzyme PEPCase
Result is 4 carbon molecule
Pumped into bundle sheath cells
Partitioning CO2 uptake & fixation

Question 16

how does CAM photosynthesis work

Answer 16

Night: CAM plants use PEPCase to fix some CO2 Stored in large vacuoles
Day: C4 molecules release CO2 to Calvin Cycle when NADPH and ATP are available
Conserves water; stomata only open at night

Question 17

difference between c3 and c4 plant

Answer 17

c3
-no interbundle sheath cells with chloroplasts
c4
-more cyclically organized
-more packed together
-strictly palisade mesophyll cells
-interbundle sheath with chloroplasts

Question 18

c4 plants advantages

Answer 18

C4 high light intensity, high temperatures, limited rain fall

Question 19

c3 plants advantages

Answer 19

C3 plants rain, wide range of temperatures (better than C4 below 25 °C) and humid environments

Question 20

CAM plants advantages

Answer 20

CAM plants do well in arid environments

Question 21

What is the ultimate destination for the energized electrons during the light reactions of photosynthesis?

a.
They are taken up by NADPH to produce NADP+

b.
They are taken up by NAD+ to produce NADH

c.
They are taken up by NADP+ to produce NADPH

d.
They are taken up by NADH to produce NAD+

Answer 21

c.
They are taken up by NADP+ to produce NADPH

Question 22

Which is most closely associated with the Calvin cycle?
a.
Oxygen production

b.
Carbon dioxide fixation

c.
Carbon dioxide production

d.
ATP production

e.
Removal of electrons from water for passage through an electron transport system

Answer 22

b.
Carbon dioxide fixation

Question 23

The function of sunlight in photosynthesis is to
a.
Reduce NADPH to NADP

b.
Fix O2 in the Calvin cycle

c.
Combine carbon dioxide and water to form ATP and NADPH

d.
Excite electrons in chlorophyll

e.
Split water releasing oxygen

Answer 23

d.
Excite electrons in chlorophyll

Question 24

The fixation of carbon dioxide in the first step of the Calvin cycle is facilitated by which enzyme?
a.
RuBP carboxylase

b.
PEP carboxylase

c.
Glyceraldehyde-3-phosphate (G3P)

d.
Lactate dehydrogenase

Answer 24

a.
RuBP carboxylase

Question 25

Photorespiration occurs mainly in
a.
CAM plants

b.
C4 plants

c.
All of the answer choices

d.
C3 plants

Answer 25

d.
C3 plants