Chapter 8

Question 1

Photosynthesis process

Answer 1

6 CO2 + 12 H2O + (Light energy) = C6H12O6 + 6 H20 + 6 O2

Question 2

Oxygenic Photosynthesis occurs in

Answer 2

Most plants (chloroplasts), almost all algae, cyanobacteria

Question 3

Thylakoid

Answer 3

small discs, Stacked grana

Question 4

Thylakoid membrane

Answer 4

Internal membrane
Contains chlorophyll and other photosynthetic pigments
Pigments clustered into photosystems

Question 5

Grana

Answer 5

Stacks of flattened sacs of thylakoid membrane

Question 6

Stroma

Answer 6

Semiliquid surrounding thylakoid membranes

Question 7

Stoma

Answer 7

gas exchange

Question 8

Mesophyll

Answer 8

Where photosynthesis occurs

Question 9

Chloroplast

Answer 9

Organelle holding thylakoid

Question 10

Light dependent reactions VS Carbon fixation reactions (Light independent reactions)

Answer 10

Light - Requires light. Capture energy from sunlight and makes ATP and NADPH (reduced NADP+)
Start: Sunlight, Water, NADP+ END: O2, NADPH, ATP

Dark/Carbon fixation - Does not require light. Use ATP and NADPH to synthesize organic molecules from CO2
Start: NADPH, ATP, CO2. END: Organic molecules (particularly sugars)

Question 11

Pigments

Answer 11

Molecules that absorb light energy in the visible light range

Question 12

Photon and wavelength

Answer 12

Particle of light. Acts as discrete bundle of energy
Energy content inverse proportional to wavelength of light. More energy=smaller wavelengths
Less energy = larger wavelengths

Question 13

Photoelectric effect

Answer 13

Removal of an electron from a molecule by light

Question 14

Electro Magnetic Spectrum

Answer 14

Light is for of electromagnetic energy.
Visible light 400-700 (or 740) nm

Question 15

Absorption spectrum

Answer 15

Range and efficiency of photons a molecule is capable of absorbing
When photon strikes a molecule its energy either:
1 lost as heat
2 Absorbed by the electrons of the molecule, boosts electrons into higher energy level (how photosynthesis begins)

Question 16

Two general pigments used in green plant photosynthesis

Answer 16

Chlorophylls
Carotenoids

Question 17

Chlorophyll a

Answer 17

Main pigment in plants and cyanobacteria. Only pigment that can act directly to convert light energy to chemical energy. Absorbs violet-blue to red light

Question 18

Chlorophyll b

Answer 18

Accessory pigment or secondary pigment absorbing light wavelengths that chlorophyll a does not absorb. Blue to light blue and yellows and oranges

Question 19

Structure of chlorophyll

Answer 19

Porphyrin ring (complex ring structure with alternating double and single bonds). Magnesium ion at the center of ring.
Photons excite electrons in the ring, shuttled away from the ring

Question 20

Action Spectrum

Answer 20

Relative effectiveness of different wavelengths of light in promoting photosynthesis. Corresponds with absorption spectrum for chlorophylls

Question 21

Carotenoids (tetraterpenoids)

Answer 21

Carbon rings linked to chains with alternation single and double bonds.
Can absorb photons with a wide range of energies. Also scavenge free radicals- antioxidants
Can capture UV and prevent damage.
Typically orange pigments that aren’t seen because of green

Question 22

Phycobiloproteins

Answer 22

Important in low-light ocean areas-algae
In cyanobacteria, absorb green light not absorbed by green algae at surface

Question 23

Antenna complex and Reaction center

Answer 23

Antenna complex - Hundreds of accessory pigment molecules (Carotenoids and Chlorophyll b). Gather photons and feed the captured light energy to the reaction center. Light harvesting complex
Reaction Center - 1 or more chlorophyll a molecules. Passes excited electrons out of the photosystem

Question 24

Excitation energy

Answer 24

(In antenna complex) Energy is transferred from one molecule to another until it encounters the reaction center (chlorophyll a) Now electron transfer is initiated

Question 25

Reaction Center

Answer 25

Transmembrane protein - pigment complex.
When a chlorophyll in the reaction center absorbs a photon of light, an electron is excited to a higher energy level. Light energized electron can be transferred to the primary electron acceptor (reducing it). Oxidized chlorophyll then fills its electron “hole” by receiving an electron from a donor molecule (Oxidizing the donor).

Question 26

Light dependent reactions (4 stages)

Answer 26

Primary photoevent - photon of light is captured by a pigment molecule
Charge separation - Energy is transferred to the reaction center
Electron transport - electron move through carriers to reduce NADP+
Chemiosmosis - Produces ATP

Question 27

Two types of light dependent reactions

Answer 27

Cyclic photophosphorylation - Utilizes one photosystem. Does not generate oxygen (Sulfur bacteria). Excited electrons goes to electron transport chain=ATP production

Non Cyclic photophosphorylation - Green plants produces oxygen. Uses two photosystems that work together (NOT a circle). Produces ATP and NADPH for use in carbon fixation

Question 28

2 photosystems noncyclic

Answer 28

Photosystem I (P700) transfers electrons ultimately to NADP+, producing NADPH. Electrons lost from photosystem I are replaced by electrons from photosystem II

Photosystem II (P680) oxidizes water to replace the electrons transferred to photosystem I.

Connected by electron transport chain (cytochrome/ b6-f complex)

Question 29

Ferredoxin

Answer 29

Fd = electron acceptor in step 3

Question 30

Non cyclic photophosphorylation 4 stages

Answer 30

1 photosystem II absorbs photons, exciting electrons are passed to ETC. Electrons lost are replaced by the oxidation of water, producing O2 (waste)
2 ETC pumps protons into thylakoid creates gradient
3 PS I absorbs photons, excited electrons passed to NADP+ to make NADPH. Lost electrons replaced from ETC.
4 ATP Synthase uses the proton gradient to make ATP. Chloroplast has ATP synthase enzymes in the thylakoid membrane, allows protons back into stroma

Question 31

Carbon fixation - Calvin Cycle (Dark reactions) [C3 photosynthesis]

Answer 31

Build carbohydrates in stroma cells use. 1 Energy (ATP) from light dependent reactions. Cyclic and noncyclic photophosphorylation. Drives endergonic reactions. 2 Reduction potential - NADPH from photosystem I, source of protons and energetic electrons
Key step is attachment of CO2 to RuBP (ribulose 1, 5 bisphosphate) to form PGA. Uses enzyme ribulose bisphosphate carboxylase/oxygenase or rubisco

Question 32

3 phases of Calvin Cycle

Answer 32

1 Carbon fixation - RuBP + CO2 = PGA
2 Reduction - PGA is reduced to G3P (Glyceraldehyde 3 phosphate)
3 Regeneration of RuBP - PGA regenerates RuBP
Three turns incorporate enough carbon to produce a new G3P (3 carbons). Six turns incorporate enough carbon for 1 glucose (or 2 G3P)
Output: Glucose NOT a direct product of Calvin Cycle. G3P is direct output. Used to form sucrose and starch.

Question 33

Photorespiration

Answer 33

Rubisco has 2 enzymatic activities - carboxylation (Addition of CO2 to RuBP) under normal conditions
Photorespiration - Oxidation of RuBP by the addition of O2. Favored when stoma are closed in hot conditions. Creates low CO2 and high O2.