Light and Photosynthesis

Question 1

theory for the evolution of photosynthesis

Answer 1

theory of endosymbiosis

Question 2

endosymbiosis theory explained

Answer 2

1. photosynthetic cyanobacterium enters simple non photosynthetic eukaryote
2. turns into chloroplast
3. evolves into green algae
   4.evolves into plants

Question 3

properties of light with plants

Answer 3

-Plants sense light with photosynthetic pigments, phytochrome, and blue light receptors
* Light affects many aspects of plant life, including stomatal movements, timing of leaf loss,
germination (in some plants), and growth.

Question 4

Electromagnetic radiation

Answer 4

Shorter wavelength = higher energy and
vice versa.

Question 5

what type of radiation does the sun create? what does it include

Answer 5

-The sun creates electromagnetic radiation, which includes visible light, UV, infrared, X-rays etc.

Question 6

UV properties
what does it do to DNA and what blocks it

Answer 6

-UV damages DNA and proteins; partly blocked by atmosphere

Question 7

who said light is made of particles of energy, what are these particles called?

Answer 7

Einstein, photons,

Question 8

what did newton discover about light

Answer 8

-When visible light travels through a prism, the wavelengths separate into the colors of the rainbow ().
-Each color is a different wavelength.

Question 9

Which color has the greatest havelength and lowest energy

Answer 9

red because big wave = low energy and low frequency

Question 10

chlorophyll vs carotenoids

Answer 10

chlorophyll absorb blue-red region of the light spectrum while carotenoids absorb maximum light in the blue-green region and violet region

Question 11

carotenoids

Answer 11

-accessory pigments in photosynthesis, just like chlorophyll b, absorbing wavelengths that chlorophyll a does not

-prevent damage to chlorophyll molecules by light.

-The human body converts beta-carotene into vitamin A, which we need for eye health etc.

Question 12

what is special about the light absorbing parts of pigments

Answer 12

The light-absorbing parts of the chlorophyll and carotenoid molecules have conjugated double bonds, which is common
among pigments.

Question 13

Chlorophyll a

Answer 13

Chlorophyll a is the essential pigment of photosynthesis, in cyanobacteria, algae, and plants. It’s been around for >3 billion years

Question 14

where is chlorophyll and carotenoids embedded?

Answer 14

Chlorophyll and carotenoids are embedded in the thylakoids, in units called photosystems

Question 15

Anthocyanins

Answer 15

Anthocyanins may provide photoprotection during the breakdown of chlorophyll, but this is just a hypothesis.

Question 16

Antenna complex and reaction center

Answer 16

-energy transferred molecule to molecule as long as they are close enough to each other.
-then hits the reaction center, then the ETC

Question 17

how is light energy converted to chemical energy

Answer 17

When photosynthetic pigments absorb light, their electrons become excited and move to a higher energy level. When the electron return to their original energy levels (orbits), 3 things may happen

Question 18

what are the three things that may happen after the electron returns to original energy levels

Answer 18

a) Fluorescence
b) Heat
c) Resonance energy transfer

Question 19

Resonance energy transfer

Answer 19

occurs in the antenna complex and energy is transferred to two molecules of Chl a in the reaction center.

Question 20

how do electrons go from reaction centre to ETC
(1)

Answer 20

1) The amount of energy that the two Chl a’s in the reaction centre of PS II is so great that one electron is ejected from each Chl a.
2) These electrons are accepted by the primary electron acceptor and transported through the electron
transport chain to PS 1

Question 21

how do Chl a’s in reaction center get their electrons back from water? (2)

Answer 21

oxygen is split producing oxygen and protons. Oxygen is released and protons accumulate inside the thylakoid space.

Question 22

while photosystem 2 is taking place

Answer 22

-Chl a’s in PSI also lose electrons due to light energy transferred to them by PSI antenna pigments that they receive from the antenna pigments.
-They get back the electrons that come to them from PSII through the electron transporters and the ejected electrons are transported to be finally accepted by NADP+ to form NADPH

Question 23

when is a proton gradient established?

Answer 23

-A proton gradient is established when protons accumulate from water splitting and during electron transport.

-This gradient is dissipated when protons flow into the stroma.

-The energy of this proton gradient dissipation
is used to produce ATP.

Question 24

calvin cycle shit

Answer 24

Products of the light-dependent reactions (NADPH and ATP) drive carbon-fixation
-In the first step of carbon fixation, a 5-C acceptor molecule (RuBP) reacts with a molecule of CO2
-The new 6-C molecule produced breaks into two 3-C molecules (PGA)
-The enzyme that carries out this reaction is RUBISCO. This is the key enzyme of the Calvin cycle.
-The cycle must run 6 times to make a 6-C sugar like glucose, i.e., RUBISCO must fix 6 CO2
molecules for that.