Chapter 6

Question 1

Photosynthesis

Answer 1

process that converts solar energy into chemical energy that is used by biological systems

Question 2

3 major events photosynthesis has

Answer 2

1. Sunlight is converted into chemical energy
2. water is split into oxygen
3. carbon dioxide is fixed into sugars

Question 3

photosynthesis reaction

Answer 3

Inputs: six CO2 molecules and 12 h2o molecules and sunlight

outputs: 1 sugar glucose molecule and 6 oxygen molecules

Question 4

Photosynthesis is carried out by

Answer 4

plants, algae, cyanobacteria, phytoplankton

• known as photoautotrophs or producers

Question 5

plants as photosynthesizers

Answer 5

green portions carry on photosynthesis
carbon dioxide enters leaves through stomata
roots absorb water
CO2 and H2O diffuse into mesophyll cells then into chloroplasts

Question 6

Chloroplasts

Answer 6

are a plastid or plant cell organelle
full of round flattened discs called thylakoids
where photosynthesis occurs

Question 7

thylakoids

Answer 7

found in chloroplasts
stack of thylakoids is called granum
main pigment of photosynthesis

Question 8

stroma

Answer 8

space inside chloroplasts
where calvin cycle takes place

Question 9

light reactions

Answer 9

light dependent reactions
capture light energy to power photosynthesis
occur during the day time
take place in thylakoids

Question 10

dark reactions

Answer 10

light independent reactions
do not need light energy to power their reactions and can occur day or night
also called the Calvin cycle
take place in the stroma of chloroplasts
fix carbon dioxide into glucose

Question 11

process of light reactions

Answer 11

Photosystem II happens before Photosystem I
energy absorbed by the chlorophyll is used to power photosystem 2 that breaks the bond of water absorbed through the plant’s roots.
o2 is released through the stomata
protons cross thylakoid membrane and power protein complex ATP synthase to make ATP.
NADP+ is powered up by photosystem I to make NADPH to be used in dark reactions
finish with charged NADPH, ATP, and released O2.

Question 12

stomata

Answer 12

little pores in leaves that open and close to let oxygen out and carbon dioxide in

Question 13

Wavelengths

Answer 13

red color has the least amt of energy but the greatest wavelength

violet has the most amt of energy but smallest wavelength

Question 14

photosynthetic pigments

Answer 14

chlorophyll a and b absorb violet, blue, and red wavelengths better than others - reflect green so leaves appear green
cartenoids appear yellow or orange because they reflect those colors - they absorb light in the violet-blue-green range

Question 15

Electron transport chain

Answer 15

located in thylakoid membrane
promotes efficient transfer of electrons
atp synthase complex also here
ATP production - thylakoid space is a reservoir for H+
establishes H+ gradient = large amt of potential energy
H+ gradient is used to produce ATP.
NADP+ is a coenzyme that accepts electrons and a H+ to become NADPH.

Question 16

Calvin cycle - making sugars

Answer 16

powered by ATP and NADPH generated by light reactions
occurs in stroma of chloroplasts
end product is glucose
three steps
1. Carbon dioxide fixation
2. Carbon dioxide reduction
3. regeneration of first substrate (RuBP)

Question 17

Process of calvin cycle

Answer 17

1. starts with RuBP molecules and carbon dioxide molecules
2. enzyme called Rubisco combines them into an unstable intermediate
3. this quickly splits in half and forms 2 molecules of 3 PGA which are stable
   RuBP start and end product of calvin cycle
4. atp and NADPH from light reactions provide energy to convert the two molecules of 3-PGA into their final form
5. 2 G3P are joined to make a glucose molecule

Question 18

8Regeneration of RuBP

Answer 18

1 G3P can be made into glucose or other organic molecules
5 G3P used to reform RuBP
utilizes ATP from light reactions

Question 19

fate of G3P

Answer 19

plants and algae can make any molecule they need from G3P
Form amino acids, fatty acid, and glycerol
form glucose for energy needs
form sucrose for transport through plant
form starch for storage
form cellulose for cell walls

Question 20

C3 plants

Answer 20

light and rainfall are moderate
has mesophyll cells arranged in parallel rows
carry out both reactions in mesophyll cells

Question 21

C4 plants

Answer 21

weather is hot and dry
where a C4 compound is formed first after CO2 fixation
layered arrangement around leaf veins
chloroplasts in mesophyll cells fix Co2 cells only, shield bundle sheath cells from buildup of O2
c4 plants partition reactions - allows stomata to stay closed while avoiding oxygen exposure to rubisco

Question 22

CAM Photosynthesis

Answer 22

crassulacean acid metabolism
most succulents in a desert environment, driest plants
partitioning in time
during the night, CAM plants open stomata when it is cooler
use c3 molecules to fix C4 molecules
release stored co2 when NADPH and ATP avaliable from light reaction
CAM plants compete well with C3 or C4 when the environment is extremely arid