Chapter 10: photosynthesis

Question 1

Photosynthesis

Answer 1

when chloroplasts capture light energy and convert it to chemical energy and store it in sugar and other organic molecules

Question 2

Autotrophs

Answer 2

“self feeders”; sustain by producing organic molecules from CO2 and other inorganic raw materials obtained from the environment; also called producers

Question 3

Photoautotrophs

Answer 3

use sunlight as a source of energy for the production of organic molecules; plants, algae, some protists, some prokaryotes

Question 4

Heterotrophs

Answer 4

obtain organic material by consumption; also called consumers

Question 5

Decomposers

Answer 5

use organic litter such as carcasses, feces, and leaf litter for nourishment; animals, many prokaryotes, fungi, etc

Question 6

Chlorophyll

Answer 6

green pigment within chloroplasts

Question 7

Mesophyll

Answer 7

issue in the interior of the leaf; main area where chloroplasts are located

Question 8

Stomata

Answer 8

pores in the leaf through which carbon dioxide enters and oxygen exits

Question 9

Veins

Answer 9

deliver water and export sugars

Question 10

Stroma

Answer 10

dense fluid within the chloroplast

Question 11

Thylakoids

Answer 11

interconnected membranous sacs; stacks are called grana

Question 12

Where is chlorophyll found?

Answer 12

within the thylakoid membranes

Question 13

Equation for photosynthesis

Answer 13

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

Question 14

What happens in the redox reaction in photosynthesis?

Answer 14

water is split, electrons are transferred along with hydrogen ions from water to CO2, reducing it to sugar

Question 15

why does the redox reaction reguire light?

Answer 15

electrons increase in potential energy as they move from water to sugar, so the process requires energy input (light)

Question 16

Light reactions

Answer 16

convert solar energy to chemical energy; water is split, providing electrons and hydrogen ions (protons), and give off of O2 as a by-product; light absorbed by chlorophyll drives the transfer of the electrons and hydrogen ions from water to NADP+ (becomes NADPH); also generates ATP through photophosphorylation

Question 17

Calvin Cycle (dark or light-independent reactions)

Answer 17

CO2 from the air is incorporated into organic compounds in the chloroplasts (carbon fixation); fixed carbon is reduced to carbohydrate by the addition of electrons

Question 18

What does the Calvin cycle use from the light reaction?

Answer 18

the ATP

Question 19

Where does the light reaciton ocur?

Answer 19

thylakoid

Question 20

Where does the calvin cycle occur?

Answer 20

stroma

Question 21

What is light and how does it travel?

Answer 21

electromagnetic energy; in rhythmic waves

Question 22

Wavelength

Answer 22

distance between the crests of the waves

Question 23

the shorter the light wave,

Answer 23

the higher the energy

Question 24

Electromagnetic spectrum

Answer 24

entire range of electromagnetic radiation

Question 25

Visible light

Answer 25

what you can see; most important to life – drives photosynthesis

Question 26

photons

Answer 26

discrete particles of light, each with a fixed quantity of energy; shorter wavelengths yield photons with greater energy

Question 27

Pigments

Answer 27

substances that absorb visible light; wavelength that is absorbed disappears

Question 28

if all wavelengths are absorbed,

Answer 28

surface appears black

Question 29

the color reflected is

Answer 29

NOT absorbed by the pigments

Question 30

Why are leaves green?

Answer 30

they reflect back the green wavelengths of light

Question 31

Absorption spectrum

Answer 31

what wavelengths of light a pigment can absorb; use a spectrophometer to measure

Question 32

What are the two pigments of chlorophyll?

Answer 32

chlorophyll a and b; chlorophyll a participates directly in the light reactions while b is an accessory pigment

Question 33

Carotenoids

Answer 33

accessory pigments in leaves; various shades of yellow and orange; absorb more light; more importantly, are photoprotection

Question 34

function of carotenoids

Answer 34

absorb and dissipate excessive light energy that would damage chlorophyll or interact with oxygen forming oxidative molecules that ware dangerous to the cell

Question 35

What happens when a molecule of proton absorbs a photon of light?

Answer 35

one of the molecule’s electrons is elevated to an orbital where it has more potential energy; pigment molecule is excited

Question 36

what happens to the excited pigment molecule?

Answer 36

are unstable; electrons release the excess energy and drop back down to their ground (normal) state; release energy as heat and light

Question 37

Photosystem

Answer 37

a protein complex called a reaction-center complex surrounded by several light-harvesting complexes; includes a special pair of chlorophyll a molecules

Question 38

Light harvesting complex

Answer 38

consists of various pigment molecules bound to proteins; number and variety of pigment molecules enable a photosystem to harvest light over a larger surface and a larger portion of the spectrum

Question 39

CAM plants

Answer 39

crassulacean acid metabolism; used in plants that close their stomata during the day; store carbon at night for use during the day

Question 40

C4 plants

Answer 40

preface the Calvin cycle with an alternative method of carbon fixation that produces a 4-carbon molecule; used in hot regions with intense sunlight where plants have to partially close there stomata during the day; minimize the use of O2

Question 41

What happens during phase 1 (carbon fixation) of the the calvin cycle?

Answer 41

each CO2 is attached to a five-carbon sugar molecule (RuBP) using the enzyme rubisco produces 6-carbon intermediate that splitsin half, forming two 3-carbon molecules

Question 42

What happens during phase 2 (reduction) of the the calvin cycle?

Answer 42

each 3-carbon molecule receives and additional phosphate group from ATP, then a pair of electrons from NADPH, transforms into the 3-carbon sugar that exits the cycle

Question 43

What happens during phase 3 (regeneration) of the the calvin cycle?

Answer 43

Regenergation of the CO2 acceptor (RuBP) – three molecules of ATP are used to regenerate three molecules of RuBP; cycle can begin again

Question 44

photorespiration

Answer 44

what we have just discussed; plants that use this are called C3 plants because the first product of carbon fixation is a three-carbon molecule

Question 45

What is used during the Calvin cycle?

Answer 45

nine molecules of ATP and six molecules of NADPH

Question 46

In what form does carbon enter and leave the calvin cycle?

Answer 46

enters in the form of carbon dioxide and leaves as sugar

Question 47

How many times must the Calvin Cycle be repeated to make one molecule of 3 carbon sugar (RuBP) into glucose?

Answer 47

three times

Question 48

What does the Calvin cycle use for energy?

Answer 48

ATP

Question 49

What does the Calvin Cycle use as a reducing power? Why?

Answer 49

NADPH; adding high-energy electrons to make the sugar

Question 50

Difference between Chemiosmosis in Chloroplasts and Mitochondria

Answer 50

oxidative phosphorylation in mitochondria uses organic molecules to provide electrons; photophosphorylation in plants uses water

Question 51

Similarities between Chemiosmosis in Chloroplasts and Mitochondria

Answer 51

use energy harvested to form an H+ gradient, then use ATP synthase channels to produce ATP as the H+ ions flow through them