Unit 2 Quizzes

Question 1

Where on the earth does C4 photosynthesis dominate? What do these places have in common? Why are C4 grasses successful in those locations?

Answer 1

• C4 plants dominate in areas where there is sun, hot climate, arid, and coastal. All of these places have in common is that they are near the equator and have a higher intensity to the sun.
• C4 grasses are successful in those locations because they make their membranes through sterols to deal with the fluctuations of temperatures.
• -Make membranes more fluid

Question 2

What are the advantages of C4 over C3 synthesis? What is the cost?

Answer 2

Advantages: Less photorespiration, Less peroxides, More sugar, More efficient bc it uses the same amount of energy

Costs: Costs energy to fix and break down things, Two new enzymes to make and ATP to run both enzymes, Enzymes have to be synthesized, Internal energy lost - sun energy is the same

Question 3

What are the major differences between starch and sucrose? Where are they synthesized? What are they used for?

Answer 3

The differences between starch and sucrose is that starch is synthesized in the chloroplast and sucrose is synthesized in the cytosol. Starch is immobile and sucrose is mobile Starch is a very large molecule and can be made into a large molecule instead of individual ones, whereas sucrose is very small and can be transported via the phloem. During the day starch is produced and at night starch is broken down into smaller molecules to form sucrose. Lastly, sucrose is highly regulated in order to regulate solute potential. Starch is used for storage while sucrose is used for energy.
Starch is inert; sucrose is water soluble
Too much - mess up solute potential

Question 4

What are the ways in which the Calvin-Benson Cycle is regulated? How do they slow down or speed up carbon fixation?

Answer 4

The Calvin-Benson cycle is regulated by CO2 and light.

They can slow down or speed up carbon fixation by controlling the metabolic activity of enzymes

Question 5

What are the three components of the calvin-benson cycle? What are their inputs and what are their outputs?

Answer 5

Carboxylation, reduction, and regeneration
The inputs of carboxylation are water, CO2, and ribisco, and the outputs are 3 PGA molecules. The inputs of reduction are 3 PGA molecules, ATP, and NADPH, which produces ADP, NADP +, and 6 G3P molecules. One of those molecules is used to make starch, and the other five are used in regeneration to make ribisco. For regeneration, the inputs are ATP and 5 G3Ps to make the output of ribisco to continue the cycle. The net product of this cycle are 1 G3P, which splits off the make starch.
ATP and NADPH are from the light reactions and after being used and reduced they are put back into the light reaction cycle

Question 6

Chloroplasts are treated with a herbicide. Oxygen continues to be generated, but CO2 assimilation ceases. What is the herbicide?

Answer 6

Paraquat
The electrons can still be cycled back to keep producing oxygen because the photosynthetic cycle is disrupted at ferredoxin, which means that photosystem 2 is still able to cycle the electrons to make oxygen. The system is affected further down the line, which prevents the plant from making the necessary materials needed to produce carbon in the Calvin cycle that is later on in the cycle.

Question 7

what is the absorption spectrum? What is the quantum yield? Why do the graphs differ?

Answer 7

• The absorption spectrum is the amount of light that gets into the system that can be converted into energy. That is why the graph is high at the blue and red wavelengths and a dip in the green.
• Quantum yield is the magnitude of a biological response to different wavelengths of lights and the physical reaction. It is the amount of photons per quantum absorbed. Is only relative to the wavelengths that are absorbed.
• There is a dip in the absorption spectrum in the middle because it doesn’t absorb green well. The quantum yield dips because it is not as efficient at absorbing that color. Carotenoids are less efficient at turning light that is absorbed into O2 than chlorophyll.

Question 8

Based on this figure, which wavelengths of light do plants absorb? Which do they reflect?

Answer 8

Absorb: Red and blue
Reflect: Green because there is a dip in the figure
Bouncing back green light at us

Question 9

where do plants get energy?

Answer 9

• Plants get energy from the sun and use that energy in photosynthesis.
• The sun emits 3.6 x 1026 watts of energy
• illuminosity is 3.8 x 1026 Joules
• Total energy output is 4 million tons every second
• Density changes based on the curvature of the earth
• So actually 4.5 lbs of energy per second
• Photosynthesis produces CO2 from water and releases oxygen into the atmosphere.
• The ground provides nutrients, not energy

Question 10

what factors limit photosynthesis?

Answer 10

• Light, CO2, water, minerals and nutrition, and temperature.
• Can limit enzymes

Question 11

what specific predictions are made by Munch’s pressure flow model of phloem translocation?

Answer 11

1. sieve pores are open
2. flow is not bidirectional
3. flow does not require energy
4. a pressure gradient exists such that pressure is higher near the source and lower near the sink

Question 12

what is the driving force for movement in the phloem?

Answer 12

positive pressure gradient

Question 13

plants want light, water, nutrients, and CO2 for growth, developement, and reproduction. However, in excess these can be damaging. In what ways? What mechanisms do plants use to compensate for excess?

Answer 13

LIGHT

• limits rubisco regeneration
• water
• nutrients
• CO2