Lecture 13: Chapter 8 - Plant adaptations to the environment

Question 1

Describe how carbon cycles between terrestrial ecosystems and the atmosphere

Answer 1

-carbon enters the ecosystem through photosynthesis and it produces carbon that can be allocated to grow more plant matter or to be exuded through the roots into the soil.
-in the soil, the carbon can become soil organic matter, microbial biomass, etc.
-about 50% of all carbon that is fixed by plants through photosynthesis is lost to respiration because every living plant cell also produces CO2 in their mitochondria
-soil microorganisms can break down organic matter and respire it back to CO2
-carbon can also leave through leaching, erosion, combustion, or harvest
CARBON ENTERS THE TERRESTRIAL ECOSYSTEM THROUGH PHOTOSYNTHESIS AND GOES BACK TO THE ATMOSPHERE THROUGH PLANT OR MICROBIAL RESPIRATION

Question 2

autotroph/ producers

Answer 2

-like plants, they make their own food via photosynthesis
-autotrophic organisms (bacteria, archaea, plants) transform inorganic C (CO2) into organic C using energy obtained from the oxidation of inorganic molecules or sunlight.

Question 3

heterotroph

Answer 3

-like animals, they need to eat other organisms to get energy
-heterotrophs gain C by consuming other organisms.

Question 4

(net) photosynthesis

Answer 4

net photosynthesis = (gross) photosynthesis - respiration

Question 5

allocation

Answer 5

a plant is given an amount of resources at any point in time and it allocates these resources to different structures

Question 6

respiration

Answer 6

-how carbon is returned to atmosphere
-takes place in the mitochondria
-does not require sunlight
-involves oxidation of sugars and the reduction of oxygen to form CO2 and water and ATP

Question 7

Explain the process of C3 photosynthesis (light vs dark rxns) and photorespiration

Answer 7

-light dependent reactions: light energy in the form of PAR strikes the chlorophyll molecules. electrons are excited and then passed on along an electron transport chain in a series of reactions that eventually generates two energy carrier molecules, NADPH and ATP. the electron is replenished from H2O, releasing O2
-dark reaction (calvin benson cycle): 3 diff rxns. the carboxylation of RuBP to PGA via RuBisCO enzyme. the reduction of PGA to G3P. most of G3P is regenerated back into RuBP.

Question 8

Sketch the basic structure of a C3 plant (mesophyll, stomata, epidermis)

Answer 8

-epidermis is cell wall at the top and bottom
-in the leaf there is different types on mesophyll
-inside mesophyll has little green dots, those are chloroplasts
-pores on the bottom are the stoma/stomata

Question 9

Sketch how C3 photosynthesis responds to the availability of PAR

Answer 9

light compensation point should be on the x axis
rate of respiration should by on y axis
light saturation point is where is flattens out

Question 10

Sketch how C3 photosynthesis responds to the availability of CO2

Answer 10

curve same as light response curve
refer to picture for labels

Question 11

reactants of photosynthesis

Answer 11

6CO2 AND 12 H2O

Question 12

products of photosynthesis

Answer 12

C6H12O6 6H2O AND 6O2

Question 13

respiration reactants

Answer 13

C6H12O6 AND 6O2

Question 14

respiration products

Answer 14

6CO2 6H20 AND ATP

Question 15

all trees are ___

Answer 15

C3 plants

Question 16

photosynthesis occurs inside the ___

Answer 16

chloroplasts

Question 17

light reactions occur inside the ____

Answer 17

thylakoid inside chloroplast (green springy things)

Question 18

dark reactions occur inside the _____

Answer 18

stroma inside chloroplast (fluid filled internal space)

Question 19

NADPH is a reduction of

Answer 19

NADP+

Question 20

ATP is a ___ of ADP

Answer 20

phosphorylation

Question 21

reactants of light reaction

Answer 21

light (PAR) and water

Question 22

products of light reaction

Answer 22

O2 NADPH AND ATP

Question 23

why is it called c3 photosynthesis

Answer 23

because PGA is two 3-C molecules, 3 carbon

Question 24

drawbacks of C3 photosynthesis

Answer 24

RuBisCo is not only a carboxilase but also a oxygenase so it can either facilitate the reaction of RuBP and CO2 (carboxylation) or the reaction between RuBP and O2 which produces glycine. this process produces some carbon for the plant but it also produces CO2 and NH3 ammonia gas so it wastes nitrogen that the plant has available and the plant has to detoxify because of the ammonia gas.(photorespiration)

Question 25

when does photorespiration happen?

Answer 25

when the partial pressure of CO2 in the atmosphere and the cells is low

Question 26

where does photorespiration happen?

Answer 26

chloroplasts
-occurs only when light is available

Question 27

where does (aerobic) respiration happen?

Answer 27

mitochondria
-light independent