Learning Outcomes (8-9-10-11)

Question 1

what is the equation for photosynthesis

Answer 1

6CO2+6H2O+light energy→C6H12O6+6O2

Question 2

light consists of [blank], which are packets of energy

Answer 2

photons

Question 3

which wavelengths of light does photosynthesis use, since different wavelengths of light carry different amounts of energy

Answer 3

blue (450 nm) and red (680 nm)

Question 4

Chlorophyll is a pigment that mainly absorbs light at which wavelenghts?

Answer 4

red (680nm) and blue (450 nm)

Question 5

what is the chemical structure of chlorophyll?

Answer 5

a porphyrin ring (allow chlorophyll to absorb light) and a phytol tail (anchors in the thylakoid membrane).

Question 6

how does chlorophyll trap light energy

Answer 6

it converts light energy, photon wavelengths into chemical energy during light reactions

Question 7

2 main types of accessory pigments

Answer 7

carotenoids and phycobilins

Question 8

what is the main function of accessory pigments (5 functions)

Answer 8

increase the range of light that a plant can aborb

when they absorb light, they pass off their energy to chlorophyll a, the reaction center of photosynthesis

protect chlorophyll a from photooxidizing

absorb and dissipate excess light energy

increase efficiency of light absorption and photosynthetic rate

Question 9

absorption spectrum shows what?

Answer 9

how well different wavelengths of light are aborbed by different pigments

Question 10

what does the action spectrum show

Answer 10

the rate of photosynthesis at different wavelengths, indicating which wavelengths are most effective.

Question 11

what is the absorption spectrum of chlorophyll (a and b) vs carotenoids

Answer 11

chlorophyll a absorbs in 430 - 660 (blue-violet - red), reflect green
chlorophyll b absorbs in (450 - 650) (torqoise blue - red orange), reflect greeen

carotenoids absorb in the 400 - 500 (absorb blue - green), reflect reds, yellows, oranges

Question 12

the reaction center is

Answer 12

A specialized pair of chlorophyll a molecules where energy from light (sun), in photons, is converted into electron transport.

it is found in Photosystem I and Photosystem II.

Question 13

quantum yield refers to

Answer 13

the efficiency of photosynthesis, defined as the number of CO₂ molecules fixed per photon absorbed.

Question 14

the general concept of a redox reaction involves

Answer 14

transfer of electrons; where oxidation is the loss of electrons, and reduction is the gain.

leo ger

Question 15

In Photosynthesis: Light energy drives the transfer of electrons from water

Answer 15

to NADP⁺, forming NADPH.

Question 16

light reactions occur where, and involve what

Answer 16

Occur in the thylakoid membranes (pigment molecules are here), involving electron transport, ATP, and NADPH production.

Question 17

dark reactions occur where and involve what

Answer 17

in the stroma, using ATP and NADPH to fix CO₂ into glucose.

Question 18

the Z scheme describes the flow of electrons in which reactions?

what happens in PSII vs PSI?

Answer 18

light reactions

Photosystem II (PSII): Absorbs light, splits water molecules, and releases O₂, drives ATP synthesis
Photosystem I (PSI): Absorbs light and transfers electrons to NADP⁺ to form NADPH.

Question 19

why is the ETC important in photosynthesis

Answer 19

converts light energy into chemical energy and moves protons across the thylakoid membrane into the lumen

Question 20

in the calvin cycle, what is carboxylation, reduction, and regeneration

Answer 20

Carboxylation: CO₂ is fixed to RuBP by rubisco.
Reduction: Produces G3P, a precursor for glucose.
Regeneration: RuBP is regenerated from G3P.

Question 21

what are the roles of Rubp and rubisco

Answer 21

RuBP (Ribulose-1,5-bisphosphate):
The CO₂ acceptor in the Calvin cycle.
Rubisco:
Catalyzes the first step of CO₂ fixation.

Question 22

what is the role of G3P

Answer 22

A 3-carbon sugar produced in the Calvin cycle, which can be used to form glucose and other carbohydrates.

Question 23

components of regeneration of Rubp from g3p in calvin cycle

Answer 23

• Regeneration of RuBP:
  
  • Conversion of G3P:
    
    • G3P (3-carbon) is converted into 5-carbon intermediates.
  • Sugar Rearrangements:
    
    • Involves enzymes like aldolase and transketolase.
    • Intermediates include ribose-5-phosphate and xylulose-5-phosphate.
  • Phosphorylation:
    
    • ATP is used by phosphoribulokinase to phosphorylate ribulose-5-phosphate into RuBP.
• Enzymes Involved:
  
  • Aldolase: Combines sugar phosphates.
  • Transketolase: Transfers carbon units between sugars.
  • Phosphoribulokinase: Final step, phosphorylates ribulose-5-phosphate to RuBP.
• Energy Requirement:
  
  • ATP is consumed during phosphorylation.
  • No NADPH used in this phase.
• Importance:
  
  • Regenerates RuBP, enabling the continuous fixation of CO₂ in the Calvin cycle.

Question 24

Know the products and understand the consequences of the dual carboxylation
and oxygenation functions of rubisco

Answer 24

Carboxylation:

CO₂ + RuBP → Two 3-phosphoglycerate (3-PGA) molecules.
Outcome: Leads to the Calvin cycle, producing sugars like G3P.
Oxygenation:

O₂ + RuBP → One 3-phosphoglycerate (3-PGA) + One 2-phosphoglycolate.
Outcome: Initiates photorespiration, which consumes energy and releases CO₂.
Consequences:
Carboxylation:

Efficient CO₂ fixation, leading to sugar production and plant growth.
Oxygenation:

Reduces photosynthetic efficiency by diverting RuBP and consuming ATP and NADPH without producing sugars.
Increases under high O₂/low CO₂ conditions (e.g., drought or high temperatures).

Question 25

where does photrespiration happen and what are the consequences

Answer 25

Occurs when rubisco fixes O₂ instead of CO₂, leading to the production of 2-phosphoglycolate.

Reduces photosynthetic efficiency.

Question 26

C4 Metabolism:

Answer 26

Spatially separates CO₂ fixation and the Calvin cycle, reducing photorespiration.
Involves Krantz anatomy.

Question 27

CAM Metabolism

Answer 27

Temporally separates CO₂ fixation and the Calvin cycle, storing CO₂ at night to minimize water loss.

Question 28

why can cacti grow in deserts

Answer 28

CAM Photosynthesis:
Crassulacean Acid Metabolism (CAM): Cacti open their stomata at night to take in CO₂, minimizing water loss during the hot daytime.
CO₂ is stored as malic acid in vacuoles and used during the day for photosynthesis when the stomata are closed.
**2. Water Storage:
Succulent Tissues: Cacti have thick, fleshy stems that store large amounts of water, allowing them to survive long periods of drought.
**3. Reduced Leaf Surface:
Spines Instead of Leaves: Spines reduce water loss by limiting transpiration and also provide shade and protection from herbivores.
**4. Efficient Root System:
Shallow and Widespread Roots: Quickly absorb water from light rains.
Deep Roots: Access deeper water reserves during prolonged dry periods.
**5. Thick Cuticle:
A waxy layer on the stem reduces water loss by minimizing evaporation.
**6. Slow Growth:
Reduced metabolic rates help conserve energy and water, allowing cacti to survive in nutrient-poor and water-scarce environments.

Question 29

main difference between chlorophyll a and chlorohpyll b by functional group

Answer 29

chlorophyll a has a methyl group, chlorophyll b has an aldehyde

Question 30

chlorophyll is found in the

lumen vs stroma

Answer 30

thylakoid

lumen is fluid inside thylakoid, stroma is fluid in chloroplast

Question 31

products and reactants of light dependent

Answer 31

h20 is oxidized into O2
NADP+ is reduced into NADPH
ATP is formed via ATP synthase by chemiosmosis via ADP and inorganic phosphate

Question 32

reactants and products of calvin cycle

Answer 32

ATP turns back into ADP + Pi and drives the calvin cycle, where NADPH is oxidized into NADP+ and then using those electrons, CO2 is able to reduce into glucose

Question 33

the electron transport chain is in the

Answer 33

thylakoid membrane

Question 34

krantz anatomy

Answer 34

bundle sheath cells surround vascular bundle (xylem and phloem), and is where calvin cycle takes place

mesophyll cells is where fixation occurs

important for c4 plants bc concentrating c02 in bundle sheaths allow for photosynthesis even in dry conditions when stomata remain closed