8.2: The light reactions convert solar energy to the chemical energy of ATP and NADPH

Question 1

Where do the light reactions occur?

Answer 1

The light reaction occurs in the thylakoids where the light is transformed into chemical energy of ATP and NADPH

Question 2

wavelength

Answer 2

the distance between crests of electromagnetic waves can range from less than a nanometer to more than a kilometer

Question 3

electromagnetic spectrum

Answer 3

the entire range of radiation

Question 4

visible light

Answer 4

the segment most important to live is about 380 nm to 750 nm which is this light, drives photosynthesis

Question 5

photons

Answer 5

the discrete nontangible particle that makes up light

Question 6

What signifies a high amount of energy?

Answer 6

the shorter the wavelength, the more energy there is, less nm = more energy for electrons

Question 7

pigments

Answer 7

absorption spectrum: a graph plotting a pigment’s light absorption versus wavelength

Question 8

absorption spectrum

Answer 8

a graph plotting a pigment’s light absorption versus wavelength

Question 9

chlorophyll a

Answer 9

the key light-capturing pigment that participates directly in the light reactions

Question 10

chlorophyll b

Answer 10

accessory pigment, broadens spectrums

Question 11

carotenoids

Answer 11

another accessory pigment, absorbs damaging lights

Question 12

photoprotection

Answer 12

absorb and dissipate excess light energy that would otherwise damage chlorophyll or interact with oxygen

Question 13

What happens when the chlorophyll absorbs the light

Answer 13

When the chlorophyll absorbs the light(not all) and reflects the others in the spectrum, one of the electrons goes to a new level/electron shell

Question 14

fluorescence

Answer 14

when electrons go back to their ground state, photons are given off, goes to the ETC

Question 15

Photosystems

Answer 15

where chlorophyll molecules are organized along with other small organic molecules and portion into these complexes

Question 16

reaction-center complex

Answer 16

surrounded by light-harvesting complex, composes the middle photosystems, proteins holding chlorophyll a, and primary electron acceptors

Question 17

light-harvesting complex

Answer 17

consists of various pigment molecules ,within this complex, the energy goes from one pigment to another

Question 18

primary electron acceptor

Answer 18

molecule capable of accepting electrons and becoming reduced

Question 19

Why doesn’t the energy released from the excited electrons dissipate as heat energy

Answer 19

excited electrons are not dissipated as light and heat due to the readily available electron acceptor

Question 20

What are the two types of chlorophyll a

Answer 20

photosystem 2: P680(680 nm)

photosystem 1: P700(700 nm)

photosystem 2 works first

Question 21

What do these 2 systems work to achieve?

Answer 21

these 2 photosystems work together to generate ATP and NADPH

Question 22

linear electron flow?, cyclic electron flow?

Answer 22

the flow of electrons through photosystems and other molecular components built into the thylakoid membrane

photosystems cycle between each other

Question 23

What are the 4 enzymes used in the light reactions ?

Answer 23

Pq and Pc help carry out redox reactions as electrons flow down the ETC

Fd accepts electrons from the primary electrons

NADP+ reductase, uses electrons from PS 2 in order to make NADPH

Question 24

Differences between Chemiosmosis in the Chloroplasts and Mitochondria

Answer 24

One notable difference is that the energy drop in chloroplasts start with water while mitochondria start with organic compounds

One starts with light while the other starts with organic compounds

Question 25

Explain how light is reflected

Answer 25

Certain light is absorbed while the rest are reflected.

Question 26

8 steps of light reactions

Answer 26

1. The photons from light cause a chain reaction of exciting electrons in each pigment of photosystem 2 until P680 is reached
2. P680 is then oxidized since the electron leaves to go to the primary electron acceptor
3. H2O is split into 2xH+, Oxygen, and 2 electrons, the
   2 electrons reduce the oxidized P680 and the H+ are in the thylakoid space, the Oxygen combines with one another and makes O2
4. The photoexcited electrons pass from the primary electron acceptor of PS2 to PS1 through an ETC, Pq, and Pc carry out redox reactions as electrons flow down the ETC, releasing free energy that is used to pump H+
5. the potential energy stored in the proton gradient is used to make ATP through chemiosmosis
6. P700 in PS 1 is now oxidized due to its exciting electron being taken, the oxidized P700 accepts electrons from PS 2
7. protein Fd accepts electrons from the primary electrons
8. NADP+ reductase catalyzes the transfer of electrons from Fd to NADP+, the 2 electrons added then create NADPH, and H+ is also removed from the stroma

Question 27

action spectrum

Answer 27

profiles the relative effectiveness of different wavelengths of radiation in driving the process