Lecture 14 : Photosynthesis

Question 1

photosynthesis

Answer 1

process that converts light energy into chemical energy

Question 2

Autotroph

Answer 2

sustain themselves without eating anything derived from other organisms

Question 3

Heterotrophs

Answer 3

• obtain their organic material from other organisms

Question 4

in what organisms does photosynthesis occur?

Answer 4

plants, algae, certain other protists, and some prokaryotes`

Question 5

What are the components of the chloroplast?

Answer 5

Outer membrane, intermemebrane, innermembrane space, stroma, thylakoid, granum, and thylakoid lumen.

Question 6

Where are chloroplasts mainly found?

Answer 6

in the cells of the mesophyll (the interior tissue of the leaf)

Question 7

stomata

Answer 7

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

Question 8

Photosynthesis equation

Answer 8

6CO2 + 6H2O + light energy ——> C6H12O6 + 6O2

Question 9

What are the two stages of photosynthesis?

Answer 9

light reactions and calvin cycle

Question 10

Where do the light-dependent reactions take place?

Answer 10

thylakoid

Question 11

what are the main events of the light reactions?

Answer 11

H2O is split and O2 is released, NADP+ is reduced, ATP is made from ADP through photophosphorylation

Question 12

Where does the Calvin cycle take place?

Answer 12

stroma

Question 13

what does the Calvin cycle do?

Answer 13

makes sugar from CO2, using ATP and NADPH provided by light reactions

Question 14

absorption spectrum

Answer 14

graph plotting a pigment’s light absorption versus wavelength

Question 15

3 types of pigment

Answer 15

chlorophyll a, cholorphyll b, carotenoids

Question 16

primary electron acceptor

Answer 16

in chloroplasts, an acceptor of electrons lost from chlorophyll a; found in the thylakoid membrane

Question 17

what is the first step of the light reactions?

Answer 17

Solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor

Question 18

steps of the light reactions?

Answer 18

1. photon hits pigment and excites reaction center
2. excited electron from PSII (turned to PSII+) is transferred to primary electrons acceptor
3. H2O is split and electrons from the hydrogen atoms reduce PSII+ back to PSII and in the process release O2 and H+ into the thylakoid space
4. electrons “fall down” from PSII to PSI
5. Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane
6. transferred light energy excites P700, which loses an electron to an electron acceptor (now P700+ but then accepts an electron passed down from PS II via the electron transport chain)
7. Each electron “falls” down an electron transport chain from the primary electron acceptor of PS I
8. The electrons are then transferred to NADP+ and reduce it to NADPH in the stroma

Question 19

Chlorophyll molecules are not isolated, rather they are organized with other small molecules into a complex

Answer 19

photosystem

Question 20

a photosystem has what two complexes

Answer 20

reaction-center complex and light-harvesting complexes

Question 21

reaction-center complex

Answer 21

holds chlorophyll a and primary e- acceptor

Question 22

primary e- acceptor

Answer 22

molecule capable of accepting e- and becoming reduced

Question 23

light harvesting complex

Answer 23

antennae for the reaction center complex

Question 24

Photophosphorylation

Answer 24

Diffusion of H+ (protons) across the membrane from thylakoid space to stroma (chemiosmosis); drives ATP synthesis

Question 25

basic purpose of light reactions

Answer 25

generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH

Question 26

Steps of the Calvin cycle

Answer 26

1. 3 molecules of CO2 enter and combine with RuBP (rubisco used for carbon fixation) —> 6 molecules of a 3 carbon sugar
2. 6 ATP creates 6 ADP
3. 6 NADPH –> 6 NADP+ and 6P
   - Reduction (Phase 2)
   Output: 3C-1P
   - Phase 3: Regeneration
4. 3 ATP –> 3ADP + 2P
5. 1 G3P as output, 5 left are used to regenerate the 3 original molecules of RuBP

Question 27

very broad summary of calvin cycle

Answer 27

Carbon enters the cycle as CO2 and leaves in the form of sugar (CH2O)