Preview To Photosynthesis

Question 1

Give the summary equation for photosynthesis

Answer 1

6 CO2 + 12 H2O —(chlorophyll, sunlight)—> C6H12O6 + 6 H2O + 6 O2

Question 2

What are the stages of photosynthesis?

Answer 2

1. Capturing light energy
2. Synthesizing ATP and NADPH + H+
3. The Calvin Cycle (carbon fixation)

Question 3

What are stage one and two of carbon dioxide referred to as?

Answer 3

The light reactions

Question 4

What is light?

Answer 4

A form of energy that travels in wave packets called photons

Question 5

What pigments capture light energy in plants, and what colour are they?

Answer 5

Chlorophyll A and B (green), carotenoids (yellow-orange), xanthophyll (yellow), anthocyanins (red, violet, and blue)

Question 6

Where in the cell are these pigments?

Answer 6

They are embedded into the thylakoid membrane

Question 7

What is the name for the collection of pigments that absorb photons of particular wavelengths?

Answer 7

Photosystems

Question 8

In plants, what are the vast majority of pigments?

Answer 8

Chlorophyll A and B

Question 9

What are photosynthetic pigments?

Answer 9

Molecules that will absorb light of a particular wavelength and reflect or transmit light of a different wavelength

Question 10

Label the absorption spectrum for pigments in plants

Question 11

Why do plants shut down in the winter?

Answer 11

Because it can no longer absorb sunlight, so chlorophyll shuts down and the other pigments reflect different colours until they shut down too

Question 12

What are accessory pigments?

Answer 12

Pigments that absorb energy and transfer it to chlorophyll A

Question 13

Why are some visual spectra entirely covered?

Answer 13

Because the absorption of chlorophyll A and B are combined with those of the accessory pigments

Question 14

Describe photoexcitation

Answer 14

Before a photon of light strikes it, a chlorophyll molecule electrons are at the lowest possible potential energy called the ground state. During its interaction with a photon (light energy), the electron gains energy and is raised to a higher potential energy level. This is called excitation. This is an unstable position for the electron and it will soon return to its ground state. As it does so, it will lose the E gained from the photons as heat and light

Question 15

What is the term for the rapid release of energy in the form of light following photoexcitaiton?

Answer 15

Fluorescence

Question 16

What are photosystems?

Answer 16

Clusters of pigment molecules that are associated with proteins, contained by the thylakoids

Question 17

Which types of pigments does each photosystem have?

Answer 17

Antenna pigments, reaction center pigments

Question 18

What are antenna pigments?

Answer 18

Chlorophyll A and B, carotenoids, and other accessory pigments that absorb photons and transfer the energy from pigment to pigment until it reaches a chlorophyll A with a specific protein in an area called the reaction center

Question 19

What are reaction center pigments?

Answer 19

Special chlorophyll A molecules will absorb the transferred energy and its electron will be raised to a higher level. A redox reaction will transfer the excited electron from its chlorophyll molecule to the primary electron acceptor, leaving the chlorophyll molecule in an oxidized state. This begins the electron transport chain for photosynthesis

Question 20

Show a diagram of the light-capturing stage

Answer 20

Photons, chlorophyll molecules, reaction centre chlorophyll, electron acceptor, accessory pigments, electron donor, photosystem

Question 21

What are the types of photosystems that work together in photosynthesis?

Answer 21

Photosystem I (P 700) and II (P 680)

Question 22

What is different between photosystems I and II?

Answer 22

Photosystem I contains chlorophyll A P 700 because its absorption peaks at a wavelength of 700nm, whereas photosystem II contains chlorophyll A P 680

Question 23

What is the difference between P 680 and P 700?

Answer 23

They are identical chlorophyll A molecules, only their absorption spectra peak at slightly different wavelengths because of the effects of the proteins associated with the reaction centre

Question 24

Where is the ETC found in photosynthesis?

Answer 24

Along the thylakoid membrane

Question 25

Show a diagram for the photosynthesis light reaction

Answer 25

Stroma, thylakoid membrane, lumen
PSII reaction center, O2-evolving complex, cytochrome b6-f complex, Q cycle, PSI reaction center, F0F1 complex
Photons, chlorophyll, plastocyanin, ferredoxin, NADP-FAD reuctase, NADPH, H+, ATP