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Bio > bio ch 7 photosynthesis > Flashcards

bio ch 7 photosynthesis Flashcards

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Biology 101 flashcards
1
Q

what is an autotroph

A

self feeders; make their own food and sustain themselves without consuming organic molecules derived from any other organisms

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2
Q

what are photoautotrophs

A

use the energy of light to make energy and sustain themselves

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3
Q

what is photosynthesis

A

process by which plants convert CO2 and H2O to their own organic molecules and release O2 as a byproduct

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4
Q

what are the ultimate source of organic molecules for almost all other organisms

A

photoautotrophs; referred to as producers of the biosphere because they produce its food supply

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5
Q

what are chemoautotrophs

A

prokaryotes that use inorganic chemicals as their energy source and are the producers in deep-sea vent communities

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6
Q

what are heterotrophs

A

consume other plants or animals or decompose organic material

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7
Q

where does photosynthesis occur

A

chloroplasts

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8
Q

what is chlorophyll

A

gives leaves their green color; light-absorbing pigment in chloroplasts that plays a central role in converting solar energy into chemical energy

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9
Q

what is the mesophyll

A

where chloroplasts are concentrated; green tissue in the interior of the leaf

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10
Q

what are stomata

A

tiny pores on the leaf’s surface where CO2 enters and O2 exits

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11
Q

how does water reach the leaves of a plant

A

it is absorbed by the roots and delivered to the leaves in veins

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12
Q

how many chloroplasts does a typical mesophyll cell have

A

30-40

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13
Q

how many membranes are on a chloroplast

A

2 (inner and outer)

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14
Q

what do the 2 membranes of the chloroplast enclose

A

an inner compartment filled with a thick fluid called stroma

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15
Q

what is stroma

A

the thick fluid that fills chloroplasts and holds thykaloids

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16
Q

what are thylakoids

A

a system of interconnected membranous sacs suspended in the stroma that enclose another internal compartment called the thykaloid space

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17
Q

what are grana

A

stacks of thylakoids

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18
Q

what are the functions of the thylakoid membranes

A
  • hold the chlorophyll molecules that capture light energy

- house much of the machinery that converts light energy to chemical energy

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19
Q

what is the equation for photosynthesis

A

6CO2 + 6H2O = C6H12O6 + 6O2

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20
Q

where does the O2 produced during photosynthesis come from

A

water

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21
Q

what reactant of photosynthesis becomes reduced

A

CO2; reduced into sugar

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22
Q

what reactant of photosynthesis becomes oxidized

A

H2O; oxidized into O2

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23
Q

is photosynthesis an energy producing process or an energy releasing process

A

energy producing

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24
Q

does photosynthesis require energy

A

yes

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25
Q

is photosynthesis endergonic or exergonic

A

endergonic

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26
Q

what are the two stages of photosynthesis

A

light reactions and the Calvin Cycle

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27
Q

where do the light reactions occur

A

the thykaloid membranes

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28
Q

what occurs in the light reactions

A

water is split, which gives a source of electrons and gives off O2 as a byproduct
electrons are transferred to the electron acceptor, NADP+, making it NADPH, which temporarily stores electrons and hydrogen ions
generates ATP

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29
Q

summarize what happens in the light reactions

A

solar energy is absorbed and converted to chemical energy that is stored in ATP and NADPH

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30
Q

where does the Calvin cycle occur

A

the stroma of the chloroplasts

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31
Q

what does the calvin cycle ultimately do

A

assembles sugar molecules using CO2 and the energy rich products of the light reactions

32
Q

what is carbon fixation

A

the incorporation of carbon from CO2 into organic compounds

33
Q

where do the electrons come from that are used for reducing carbon in the calvin cycle

A

NADPH from the light reactions

34
Q

where does the chemical energy come from that powers several of the steps of the calvin cycle

A

ATP from the light reactions

35
Q

why is the calvin cycle sometimes referred to as the dark reactions or light independent reactions

A

bc none of the steps requires light directly

36
Q

what happens when a pigment molecule absorbs a photon of light

A

one of the electrons jumps to an energy level farther from the nucleus where it has more potential energy. It is unstable and usually drop back down to their ground state, releasing their excess energy as heat

37
Q

what is special about chlorophyll as a pigment

A

it emits light as well as heat after absorbing photons

38
Q

how does chlorophyll behave in the thylakoid membrane

A

they transfer the energy to other pigment molecules and eventually to a special pair of chlorophyll molecules; this pair passes off an excited electron before it has a chance to drop back to its ground state

39
Q

what is a photosystem

A

consists of a number of light-harvesting complexes surround a reaction-center complex

40
Q

what happens in the light harvesting complexes in photosystems

A

they contain various pigment molecules bound to proteins; the pigments absorb photons and pass the energy from molecule to molecule until it reaches the reaction center

41
Q

what happens in the reaction center complex of a photosystem

A

contains the pair of special chlorophyll a molecules and a molecule called the primary electron receptor, which accepts electrons and becomes reduced; the electron is transferred from the reaction center chlorophyll a to the primary electron receptor

42
Q

what is the chlorophyll a in the photosystem II called

A

P680 bc thats the wavelength of light it absorbs

43
Q

what is the chlorophyll a in the photosystem I called

A

P700 bc thats the wavelength go light it absorbs

44
Q

what is the main result of the light reactions

A

light energy is transformed into the chemical energy of ATP and NADPH

45
Q

how is light energy transformed into the chemical energy of ATP and NADPH

A

electrons removed from water pass from photosystem II to photosystem I to NADP+. between the two photosystems the electrons move down an electron transport chain and provide energy for the synthesis of ATP

46
Q

what does photosystem II do with its electrons

A

passes them through an ATP mill; provides energy for synthesis of ATP; also replaces the lost electrons in p700

47
Q

what does photosystem I do with its electrons

A

hands its electrons off to reduce NADP+

48
Q

what replaces the lost electrons in P680

A

the splitting of water

49
Q

what replaces the lost electrons in P700

A

the electron that reaches the bottom of the electron transport chain from photosystem II

50
Q

what are the products of light reactions

A

O2, ATP, NADPH

51
Q

what is a photon

A

a discrete pack of energy of light; has a fixed quantity of energy, and the shorter the wavelength of light, the greater the energy of its photons

52
Q

what are carotenoids

A

pigments that are various shades of yellow and orange; responsible for fall foliage

53
Q

what are the two important functions of carotenoids

A
  • may broaden the spectrum of colors that can drive photosynthesis
  • photoprotection: some absorb and dissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen to form reactive oxidative molecules that could damage cell molecules
54
Q

what powers ATP synthesis in the light reactions

A

chemiosmosis

55
Q

what happens in chemiosmosis

A

the potential energy of a concentration gradient of H+ ions across a membrane powers ATP synthesis. This gradient is created when an electron transport chain uses the energy released as it passes electrons down the chain to pump H+ across a membrane

56
Q

how is a concentration gradient created across the membrane

A

H+ ions are pumped across the membrane from the stroma into the thylakoid space

57
Q

how does the H+ get back across the membrane

A

the energy of the concentration gradient drives the H= back across the membrane through ATP synthase, which completes the flow of H+ to the phosphorylation of ADP

58
Q

what is photophosphorylation

A

the chemiosmotic production of ATP in photosynthesis

59
Q

why is the chemiosmotic production of ATP in photosynthesis called photophosphorylation

A

because the initial energy input is light

60
Q

what are the inputs to the calvin cycle

A

CO2 (from the air) and NADPH and ATP (from the light reactions)

61
Q

what are the 4 steps of the calvin cycle

A

Carbon fixation
Reduction
Release of one molecule of G3P
Regeneration of RuBP

62
Q

what happens in carbon fixation

A

Rubisco, an enzyme, combines CO2 with a 5 carbon sugar called RuBP. It is unstable and splits into two molecules of 3PGA. When 3 CO2 enter, 6 3PGA result

63
Q

what happens in reduction

A

NADPH reduces 3PGA to G3P using the energy of ATP; energy is consumed from 6 molecules of ATP and oxidize 6 molecules of NADPH. 6 molecules of 3PGA are reduced, making 6 molecules of G3P

64
Q

what happens in release of one molecule of G3P

A

Five of the G3Ps remain in the cycle. One G3P leaves as the net product of photosynthesis. G3P is used to make glucose and other organic compounds

65
Q

what happens in regeneration of RuBP

A

energy from ATP rearrange the atoms in the 5 G3P molecules to form 3 RuBP molecules, which can start another turn of the cycle

66
Q

what are C3 plants

A

first product of carbon fixation is a 3 carbon compound

67
Q

what are examples of c3 plants

A

soybeans, oats, wheat, rice

68
Q

what is one problem farmers face in growing c3 crops

A

they can close their stomata on a hot dry day and prevent CO2 from entering the leaf, which results in photorespiration (water and CO2 are the products instead of glucose)

69
Q

what is photorespiration

A

occurs in the light and consumes O2 and releases CO2; uses ATP, yields no sugar, can drain away 50% of carbon fixed by the calvin cycle

70
Q

what are C4 plants

A

first product of carbon fixation is a 4 carbon compound; close their stomata in hot dry weather but can continue making sugars and going through the calvin cycle because it has an enzyme that can fix carbon even when the co2 concentration on the leaf is low

71
Q

what are examples of c4 plants

A

corn and sugarcane

72
Q

what are CAM plants

A

adapted to very dry climates; opens its stomata and admits CO2 only at night; CO2 is fixed into a 4 carbon compound that banks CO2 at night and releases it during the day so the calvin cycle can still operate even with the stomata closed during the day

73
Q

where do plants store excess food

A

roots, tubers, seeds, and fruits

74
Q

what are greenhouse gases

A

gases in the atmosphere that absorb heat radiation

75
Q

what does the ozone layer do

A

shields the earth from uv radiation

Bio (9 decks)

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