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Biology > Chapter 4: Photosynthesis > Flashcards

Chapter 4: Photosynthesis Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

where do heterotrophs get their energy from?

A

from the food they eat

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2
Q

where do autotrophs get their energy from?

A

from the food they make themselves

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3
Q

where do phototrophs get their energy from?

A

through photosynthesis

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4
Q

what do photoautotrophs do in photosynthesis?

A

take light energy and convert it to chemical energy

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5
Q

what are the three main functions of photosynthesis?

A

reduce atmospheric carbon, release oxygen, create chemical energy that can be transferred through food chains

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6
Q

what is the purpose of photons in photosynthesis?

A

to synthesize sugars (glucose)

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7
Q

what is carbon fixation?

A

process by which inorganic carbon (CO2) is converted into an organic molecule (glucose)

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8
Q

what is photolysis?

A

the process of splitting water molecules

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9
Q

what does photosynthesis do with electrons released from photolysis?

A

excites them using solar energy

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10
Q

what occurs after electrons are excited through solar energy?

A

they are used to power carbon fixation

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11
Q

in terms of their overall reactions, what process are photosynthesis and cellular respiration, to each other?

A

they are reverse processes of each other

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12
Q

what is the reaction of photosynthesis?

A

6CO2+6H2O —(solar energy)–> C6H12O6 + 6O2

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13
Q

as opposed to cellular respiration, what type of reaction is photosynthesis and why?

A

endergonic, non-spontaneous, because it produces glucose after an INPUT of solar energy

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14
Q

as opposed to photosynthesis, what type of reaction is cellular respiration and why?

A

exergonic, spontaneous, because it breaks down glucose to GENERATE energy in the form of ATP

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15
Q

what is the epidermis?

A

an outer layer of cells that provides protection and prevents water loss

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16
Q

what are palisade mesophyll cells?

A

cells located right below the upper epidermis, has MANY chloroplasts, MOST photosynthesis occurs here

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17
Q

what are spongy mesophyll cells?

A

cells found at bottom of leaf where there is space for gas exchange, space allows these cells to facilitate movement of gases within the leaf, has SOME chloroplasts for MODERATE amounts of photosynthesis

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18
Q

what are stomata?

A

pores on underside of leaf where gas can enter and exit

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19
Q

what are guard cells?

A

surround stomata and control their opening/closing

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20
Q

what are chloroplasts?

A

organelles found in plants and photosynthetic algae, but not in cyanobacteria; similar to mitochondria

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21
Q

what are the structures of chloroplasts, from outermost to innermost?

A

outer membrane, intermembrane space, inner membrane, stroma, thylakoids, thylakoid lumen

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22
Q

what is the outer membrane of chloroplasts made of?

A

phospholipid bilayer

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23
Q

what is the intermembrane space of chloroplasts?

A

space between the outer and inner membranes

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24
Q

what is the inner membrane of chloroplast made of?

A

phospholipid bilayer

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25
Q

what is stroma in chloroplasts?

A

fluid material that fills the area inside the inner membrane

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26
Q

where does the calvin cycle occur in chloroplasts?

A

stroma

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27
Q

what are thylakoids in chloroplasts?

A

organelle suspended within the stroma; individual layers are thylakoids while entire stack is granum

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28
Q

what reactions occur in the thylakoids?

A

light dependent reactions

29
Q

what is the thylakoid lumen in chloroplasts?

A

the interior of the thylakoid; H+ ions accumulate here, making it acidic

30
Q

what do light dependent reactions do?

A

harness light energy to produce ATP and NADPH (electron carrier) to be used ONLY in the calvin cycle

31
Q

what do photosystems contain?

A

special pigments, chlorophyll and carotenoids, that absorb photons

32
Q

what does chlorophyll do that gives plants their green color?

A

absorb red and blue lights, which reflects green light

33
Q

what is the reaction center?

A

in photosystems; holds a special pair of chlorophyll molecules in the center and a primary electron acceptor

34
Q

what is the structure of the head of a chlorophyll molecule?

A

porphyrin ring structure with a magnesium atom bound in its center

35
Q

what photosystems are used in photosynthesis?

A

photosystem II (P680) and photosystem I (P700)

36
Q

what is non-cyclic photophosphorylation carried out by?

A

light-dependent reactions

37
Q

non-cyclic photophosphorylation 1st step

A

photolysis: photosystem II absorbs photons to photolyze water into 2 e-, 2 protons (H+), and 1 oxygen atom; H+ released into the thylakoid lumen

38
Q

non-cyclic photophosphorylation 2nd step

A

power up electrons: e- passed to reaction center of photosystem II (P680), photons excite e-, high energy e- then passed to primary electron acceptor

39
Q

non-cyclic photophosphorylation 3rd step

A

use ETC to harness energy: primary electron acceptor sends excited e- to ETC in thylakoid membrane; energy released from e- pumps H+ from the stroma to thylakoid lumen

40
Q

non-cyclic photophosphorylation 4th step

A

chemiosmosis intermission: water photolysis and protons pumps created an electrochemical gradient in the thylakoid lumen; protons flow down gradient from lumen back to stroma through ATP synthase, generates ATP for calvin cycle

41
Q

non-cyclic photophosphorylation 5th step

A

rinse and repeat: e- leave ETC and are passed to photosystem I reaction center (P700); photons again excite pigments in photosystem I, energizing e- to be passed to another primary electron acceptor

42
Q

non-cyclic photophosphorylation 6th step

A

generate e- carrier: e- are sent to a second, short ETC that ends with NADP+ reductase to produce NADPH

43
Q

what is NADP+ reductase?

A

an enzyme that reduces NADP+ into NADPH using electrons and protons

44
Q

what occurs in cyclic photophosphorylation?

A

photosystem I passes its electrons back to the first ETC instead of the second ETC, causing more proton pumping and more ATP production, while no NADPH is generated

45
Q

what is the calvin cycle made up of and why?

A

reactions known as light-INdependent reactions; because they do NOT directly use light energy, BUT can only occur if the light-dependent reactions are providing ATP and NADPH

46
Q

light-dependent reactions are also known as?

A

dark reactions

47
Q

what exactly does the calvin cycle do in the stroma of plant mesophyll cells?

A

fixes carbon dioxide that enters stomata

48
Q

calvin cycle 1st step

A

carbon fixation: carbon dioxide combines with 5-carbon RuBP (ribulose-1,5-biphosphate) to form 6-carbon molecules, which quickly breaks down into 3-carbon PGA (phosphoglycerates), which occurs by being catalyzed by RuBisCo

49
Q

calvin cycle 2nd step

A

reduction: PGA is phosphorylated by ATP and subsequently reduced by NADPH to form G3P (glyceraldehyde-3-phosphate)

50
Q

calvin cycle 3rd step

A

regeneration: most of the G3P is converted back to RuBP

51
Q

calvin cycle 4th step

A

carbohydrate synthesis: some of the G3P is used to make glucose

52
Q

what is the chemical reaction of light independent reactions?

A

6CO2 + 18ATP + 12NADPH + H+ → 18ADP + 18Pi + 12NADP+ + 1glucose

53
Q

in addition to fixing carbon dioxide into RuBP, what else can RuBisCo (enzyme) do?

A

cause oxygen to bind to RuBP in a process called photorespiration

54
Q

where does photorespiration occur and what does it produce?

A

occurs in the stroma; produces a two-carbon molecule phosphoglycolate that is shuttled to peroxisomes and mitochondria for conversion into PGA

55
Q

what happens to fixed carbon during photorespiration?

A

gets lost as carbon dioxide

56
Q

what are the overall products of photorespiration?

A

net loss of fixed carbon atoms and no new glucose

57
Q

what else is photorespiration known as and why?

A

C2 photosynthesis; because it produces two-carbon phosphoglycolate

58
Q

photorespiration during hot and dry climate

A

stomata are closed to minimize water loss, leads to oxygen accumulation inside the leaf while carbon dioxide is used up, RuBisCo then binds with oxygen instead of carbon dioxide, leading to photorespiration

59
Q

what occurs in C3 photosynthesis (alternative photosynthetic pathway) and what is produced?

A

normal photosynthesis, where three-carbon PGA is produced

60
Q

what is produced in C4 photosynthesis (alternative photosynthetic pathway) and in what climate?

A

produces four-carbon oxaloacetate; occurs in plants living in hot environments

61
Q

what happens to carbon dioxide in C4 photosynthesis?

A

carbon dioxide is spatially isolated to prevent photorespiration

62
Q

C4 photosynthesis 1st step

A

PEP carboxylase fixes CO2 into a three-carbon PEP molecule, producing oxaloacetate, which is converted into malate in the mesophyll cell

63
Q

C4 photosynthesis 2nd step

A

malate is transferred to bundle sheath cells, which have lower concentrations of oxygen

64
Q

C4 photosynthesis 3rd step

A

Malate is decarboxylated → inorganic CO2, spatially isolating where CO2 is fixed by RuBisCo; only drawback is pyruvate is also produced and needs to be shuttled back to mesophyll cells via ATP hydrolysis

65
Q

C4 photosynthesis 4th step

A

pyruvate is converted back into PEP

66
Q

what does crassulacean acid metabolism (CAM) photosynthesis use and for what?

A

uses temporal isolation of carbon dioxide to prevent photorespiration in hot environments

67
Q

CAM photosynthesis 1st step

A

during the day: stomata are closed to prevent transpiration (evaporation of water from plants)

68
Q

CAM photosynthesis 2nd step

A

during the night: stomata are open to let carbon dioxide in; PEP carboxylase will fix CO2 into PEP, producing oxaloacetate and then malate; however, malate is stored in vacuoles instead of being shuttled to bundle sheath cells

69
Q

CAM photosynthesis 3rd step

A

during next day: stomata closed again and malate converted back into oxaloacetate, which releases CO2 and PEP; CO2 will accumulate in the leaf for use in the calvin cycle through temporal isolation

Biology (5 decks)

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