UNIT 2 - C1.3 - Photosynthesis

Question 1

what type of organisms do photosynthesis?

Answer 1

photoautotrophs

Question 2

what energy is used in photosynthesis to oxidize H2O to O2?

Answer 2

the sun’s

Question 3

what reactant is reduced in photosynthesis?

Answer 3

carbon dioxide

Question 4

what does reducing carbon dioxide allow the productio of?

Answer 4

glucose

Question 5

what does the oxygen produced by photosynthesis come from?

Answer 5

the splitting of water

Question 6

what are the two stages of photosynthesis?

Answer 6

light-dependent reactions and light-independent reactions

Question 7

what is the purpose of the light dependent reactions in photosynthesis?

Answer 7

pigment molecules to capture light energy and use the energy to synthesize NADPH and ATP through the oxidation of H2O

Question 8

what is the purpose of the light independent reactions in photosynthesis?

Answer 8

to reduce carbon dioxide into carbs using the energy carried by ATP and electrons carried by NADPH

Question 9

where does photosynthesis occur?

Answer 9

in the chloroplasts

Question 10

what is the purpose of the thylakoids?

Answer 10

to increase surface area for pigments and light absorption

Question 11

what is the main light absorbing pigment in leaves?

Answer 11

chlorophyll

Question 12

what is the purpose of accessory pigments?

Answer 12

to absorb different wavelengths of light which increases the light available for photosynthesis

Question 13

what are two examples of accessory pigments?

Answer 13

carotene and xanthophyll

Question 14

what are the wavelenghts which chlorophyll absorbs useful for due to their energy?

Answer 14

photolysis and light dependent reactions

Question 15

what is an absorption spectrum?

Answer 15

a graph showing the range of light wavelengths absorbed by a pigment

Question 16

what wavelengths does chlorophyll absorb best?

Answer 16

400nm-500nm (blue) and 650nm-680nm (red)

Question 17

what wavelengths does chlorophyll reflect?

Answer 17

500nm-570nm (green)

Question 18

what is an action spectrum?

Answer 18

a graph showing the overall rate of photosynthesis at each wavelength

Question 19

what is the main difference between absorption and action Spectra?

Answer 19

due to accessory pigments, action Spectra will show a higher rate of photosynthesis than green light absorbed

Question 20

where do light dependent reactions take place?

Answer 20

in the intermembrane space/lumen of the thylakoids

Question 21

what are the light dependent reactions?

Answer 21

1. photoactivation and photosystems
2. photolysis
3. electron transport chain
4. chemiosmosis and photophosphorylation
5. reduction of NADP to NADPH + H+
6. cyclic photophosphorylation

Question 22

what is photoactivation?

Answer 22

the excitation of electrons in a chlorophyll pigment from the energy of light

Question 23

what is the purpose of exciting electrons in photo activation?

Answer 23

so that the electrons can leave the pigment molecule and move through the ETC

Question 24

where does photoactivation occur?

Answer 24

in the photosystems and pigments within the thylakoid membrane

Question 25

what are photosystems?

Answer 25

large protein complexes

Question 26

what is the average wavelength of light that photosystem II absorbs?

Answer 26

680nm

Question 27

what is the average wavelength of light that photosystem I absorbs?

Answer 27

700nm

Question 28

what is found at the reaction centre (core) of the photosystems?

Answer 28

a special pair of chlorophyll molecules

Question 29

how does photoactivation happen?

Answer 29

when light is absorbed by one of the pigments in the photosystem, energy is passed inward from pigment to pigment until it reaches the reaction centre where an electron In the chlorophyll molecule is energized and moves to a higher energy level and is passed to an acceptor Molecule in the ETC

Question 30

what is the acceptor Molecule in photoactivation?

Answer 30

plastoquinone (Pq)

Question 31

what is photolysis?

Answer 31

the breaking apart of a water molecule using light energy

Question 32

what is the reaction for photolysis?

Answer 32

H2O ---> 2H+ + 2e- + 1/2 O2

Question 33

what is the purpose of photolysis?

Answer 33

to generate electrons and protons

Question 34

what do the electrons produced from photolysis do?

Answer 34

replace the electrons that the reaction centre chlorophyll lost during photoactivation of photosystem II

Question 35

what do the protons produced from photolysis do?

Answer 35

they become part of a proton gradient (proton motive force) that builds up in the thylakoid lumen which will be used in chemiosmosis to make ATP

Question 36

where does photolysis occur?

Answer 36

in photosystem II in the thylakoid

Question 37

how does photolysis happen?

Answer 37

water is activated by light energy and splits forming protons and electrons and oxygen

Question 38

what is the waste product of photolysis?

Answer 38

oxygen

Question 39

what is the electron transport chain?

Answer 39

a series of membrane bound molecules that transfer electrons via redox reactions

Question 40

what is the purpose of the ETC?

Answer 40

to create a proton gradient as the electron transfer fuels the pumping of protons across a membrane

Question 41

where is the ETC?

Answer 41

in the thylakoid membrane

Question 42

why are there 2 ETCs?

Answer 42

one for PSII and one for PSI

Question 43

what does the movement of the electrons from PSII allow?

Answer 43

the pumping of protons from the stroma to the thylakoid lumen, making a concentration gradient

Question 44

what does the movement of the electrons from PSI allow?

Answer 44

the reduction of NADP to NADPH

Question 45

what is chemiosmosis and photophosphorylation?

Answer 45

the movement of protons down their concentration gradient coupled with ATP synthesis

Question 46

what is the purpose of chemiosmosis and photophosphorylation?

Answer 46

to make ATP needed in the light independent reactions

Question 47

where does chemiosmosis and photophosphorylation take place?

Answer 47

at ATP synthase embedded in the thylakoid membrane

Question 48

how does ATP formation occur from chemiosmosis and photophosphorylation?

Answer 48

the protons flow down their gradient from the thylakoid lumen to the stroma through ATP synthase which creates ATP by combining ADP with an inorganic phosphate group

Question 49

what is used to reduce NADP to NADPH?

Answer 49

excited electrons from PSI

Question 50

what is the purpose of reducing NADP?

Answer 50

to make NADPH which will be needed in the light independent reactions

Question 51

where is NADP reduced?

Answer 51

at the end of PSI ETC

Question 52

How is NADP reduced?

Answer 52

The electrons that were excited out of the PS1 reaction center chlorophyll are transported between electron carrier molecules and eventually given to NADP

Question 53

What happens when the supply of NADP runs out?

Answer 53

PSII shuts down and electrons energized by PSI return to Pq where they are transferred down the chain to pump protons across the thylakoid membrane then get re energized by PSI again

Question 54

Where do the light independent reactions take place?

Answer 54

In the stroma of the chloroplast

Question 55

What are the 3 main steps of the Calvin cycle?

Answer 55

Carbon fixation by carboxylation of TuBP, reduction of GP to TP, and regeneration of RuBP using ATP energy

Question 56

What does RuBP stand for?

Answer 56

Ribulose bisphosphate

Question 57

What does GP stand for?

Answer 57

Glycerate-3-phosphate

Question 58

What does TP stand for?

Answer 58

Triose phosphate

Question 59

what is carbon fixation?

Answer 59

adding carbon from an inorganic molecule (CO2) to an organic compound

Question 60

what is the purpose of carbon fixation in the calvin cycle?

Answer 60

to build carbohydrates as the carbon from carbon dioxide is used to build them

Question 61

where does carbon fixation occur?

Answer 61

in the stroma

Question 62

how does CO2 get to the stroma of the chloroplast?

Answer 62

by entering through the stomata and diffusing into the stroma

Question 63

what does CO2 attach to once entering the stroma?

Answer 63

5-carbon RuBP

Question 64

what enzyme catalyzes the carboxylation of RuBP?

Answer 64

ribulose bisphosphate carboxylase, aka rubisco

Question 65

what happens to the 6-carbon molecule after RuBP is carboxylated?

Answer 65

in splits into two 3 carbon molecules

Question 66

what are the two 3 carbon molecules called after the 6 carbon molecule splits?

Answer 66

GP

Question 67

how is TP formed?

Answer 67

ATP and NADPH are used to reduce GP, forming TP

Question 68

what is the pupurpose of reducing GP into TP?

Answer 68

the electrons and hydrogens from the NADPH will become part of the carbohydrate as GP needs more hydrogens to reach the 2:1 H:O ratio

Question 69

what provides the hydrogen and energy to reduce GP to TP?

Answer 69

NADPH provide the hydrogen, ATP provides energy

Question 70

where does the reduction of GP to TP occur?

Answer 70

in the stroma

Question 71

how much NADPH and ATP are required by GP to form a TP?

Answer 71

one of each

Question 72

what is TP in terms of products in the calvin cycle?

Answer 72

the carbohydrate product

Question 73

what is regeneration in the calvin cycle?

Answer 73

some of the TP molecules are recycled to regenerate RuBP

Question 74

why does RuBP need to be regenerated?

Answer 74

so that carbon fixation can occur again

Question 75

where does regeneration occur?

Answer 75

in the stroma

Question 76

how does regeneration of RuBP occur?

Answer 76

remaining TP molecules stay in the cycle and are used to regenerate RuBP

Question 77

when is ATP used in the calvin cycle?

Answer 77

during the reduction of GP to TP and regeneration of RuBP

Question 78

how many turns of the calvin cycle are needed to produce one molecule of glucose?

Answer 78

6

Question 79

what can glucose produced by photosynthesis be used for?

Answer 79

respiration to produce ATP, storage after being converted to starch, cell walls after being converted to cellulose

Question 80

how can the rate of photosynthesis be measured?

Answer 80

by measuring the increase in oxygen produced by photosynthesis or by measuring the decrease in carbon dioxide used in photosynthesis

Question 81

what are the limiting factors for photosynthesis?

Answer 81

temperature, light intensity, carbon dioxide concentration

Question 82

if more than one factor is affecting the rate of photosynthesis, which one is the limiting factor?

Answer 82

the factor that is farthest from its optimal point

Question 83

what does the graph for light intensity as a limiting factor look like?

Answer 83

increases, then plateaus

Question 84

what does the graph for level of carbon dioxide as a limiting factor look like?

Answer 84

increases, then plateaus

Question 85

what does the graph for temperature as a limiting factor look like?

Answer 85

increases slowly until optimum point, then drastically decreases

Question 86

how can light intensity and rate of photosynthesis be investigated?

Answer 86

by changing the distance of a light source from the photosynthesizing organism

Question 87

how can carbon dioxide concentration and rate of photosynthesis be investigated?

Answer 87

in aquatic plants by changing the concentration of NaHCO3 (sodium hydrogen carbonate) dissolved in water

Question 88

how can temperature and rate of photosynthesis be investigated?

Answer 88

by changing the temperature of the water surrounding an aquatic plant