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BI157 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

What is photosynthesis?

A

conversion of sunlight to chemical energy in sugars and other organic molecules

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2
Q

How did photosynthesis originate?

A

Originates in a group of bacteria that had infolded regions of the plasma membrane

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3
Q

What are autotrophs? (2)

A

AKA producers produce their organic molecules from CO2

sustain themselves without eating anything derived from other living beings

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4
Q

what are photoautotrophs?

A

organisms that use light to synthesize organic substances

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5
Q

what are heterotrophs? (2)

A

aka consumers, includes decomposers

obtain organic material through compounds produced by other animals

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6
Q

what is the endosymbiont theory for chloroplast?

A

original chloroplast was a photosynthetic prokaryote that lived inside an ancestor of eukaryotes

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7
Q

where does photosynthesis take place?

A

in the mesophyll

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8
Q

What is mesophyll? (3)

A

tissue of the interior leaf

where chloroplasts are found

30-40 chloroplasts between 2-4 um by 4-7 um

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9
Q

what is the stomata? (2)

A

microscopic pores in leaves

where CO2 enters and O2 leaves

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10
Q

what is the stroma?

A

a dense fluid surrounding the envelope of two membranes in a chloroplasts

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11
Q

what are thylakoids?

A

sacs that segregate the stroma from the thylakoid space in the stroma

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12
Q

what is granum?

A

stacks of thylakoids

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13
Q

what is chlorophyll? (2)

A

green pigment in the thylakoid

absorbs light energy

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14
Q

how does photosynthesis work? (3)

A

plants produce organic compounds and oxygen from carbon dioxide and water in the presence of light

produces a three C sugar used to make glucose

chloroplast splits water into oxygen and excess water, while CO2 is used to form sugar

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15
Q

Photosynthesis vs Cellular Respiration (4)

A

both are redox

photosynthesis reverses direction of electron flow

splits water, and electrons are transferred with H+ to reduce sugar

photosynthesis is endergonic, requiring energy in the form of light

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16
Q

what are the stages of photosynthesis?

A

Light reaction and Calvin cycle

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17
Q

What is the light reaction? (2)

A

steps that convert solar energy to chemical energy

occurs in the thylakoids

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18
Q

What occurs during the light reaction? (4)

A

Water is split

O2 is given off as a by-product

light drives e- and H+ to an acceptor called NADP+

generated ATP using chemiosmosis

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19
Q

What occurs during the calvin cycle? (4)

A

synthesis of sugar

occurs in the stroma

incorperates CO2 from the air into organic molecules in the chloroplast (carbon fixation)

reduces fixed carbon using NADPH to carbohydrates by adding electrons using ATP

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20
Q

what is electromagnetic energy?

A

energy traveling in waves

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21
Q

What are wavelengths?

A

distance between crests of electromagnetic waves

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22
Q

What is visible light?

A

radiation in the band of 380 nanometers to 750 nanometers

23
Q

What are photons? (2)

A

discrete particles consisting of light

Shorter the wavelength, the higher the energy of the photon

24
Q

What are pigments? (5)

A

substances that absorb visible light

Different pigments absorb different wavelengths

White light- wavelength is reflected

If all wavelengths is absorbed, pigment is black

Color is whatever that is reflected

25
Q

What is a spectrophotometer?

A

instrument that measures how a pigment absorbs light

26
Q

what is an absorption spectrum?

A

pigment’s light absorption vs wavelength

27
Q

what is chlorophyll alpha? (3)

A

key light-capturing pigment in the chloroplast that participate in the light reactions

Violet blue and red light works best

Green is the least effective

28
Q

what is chlorophyll beta? (3)

A

hydrocarbons that are shades of yellow and orange

Broadens the action spectrum

photoprotection absorbs and dissipates excessive light energy that would damage chlorophyll

29
Q

what is an action spectrum?

A

profiles relative effectiveness of different wavelengths of radiation in driving a process

30
Q

What happens after the light is absorbed?

A

the electrons in the molecule are elevated to an orbital with more potential energy

pigment molecules are excited

energy transferred from pigment to pigment within a light-harvesting complex, until it is passed to a reaction center complex

31
Q

what is a photosystem? (2)

A

composed of a reaction center surrounded by several light-harvesting complexes (organized association of proteins holding chlorophyll alpha molecules)

thylakoid consists of two photosystems

32
Q

what is a light-harvesting complex?

A

consists of various pigment molecules bound to a protein

33
Q

What happens in the reaction complex?

A

contains a molecule capable of accepting e- and becoming reduced

electron is transferred from the reaction-center chlorophyll alpha to said molecule

34
Q

What is Photosystem 2? (2)

A

reaction center complex aka P680

Absorbs wavelengths of 680 and 700 nanometers

35
Q

what is the linear electron flow?

A

Flow of electrons through the two photosystems which synthesizes ATP

36
Q

What are the first four steps of the linear electron flow?

A
  1. photon strikes pigment molecules in PS2. chain of pigments excited until it reaches the P680 pair of chlorophyll alpha
  2. electron is then transferred to the primary electron acceptor
  3. enzyme splits water int two electrons. these are supplied to the P680. H+ is released into the thylakoid. Photoezcited e- is passed through an ETC to PS1
37
Q

What are the last four steps in the LEF?

A
  1. fall of electrons provide energy for ATP synthesis. the electron si passed through the cytochrome complex
  2. light energy is transferred to the PS1 to excite an electron of the P700 pair of chlorophyll alpha, which is then passed to a primary electron acceptor.
  3. electron is passed in a series of redoc reactions to a second ETC
    the enzyme NADP+ reductase catalyzes electrons transfer to NADP+ to form NADPH
38
Q

what is the cyclin electron flow? (4)

A

An alternate path for photoexcited electrons

Uses PS1 only

Does not produce NADPH or oxygen

Generates ATP

39
Q

what is chemiosmosis in chloroplast? (4)

A

In chloroplast, the e- dropped down the transport chain come from water

Chloroplast do not need molecules from food to make ATP
I
n light, the pH of the thylakoid space is about 5

pH of the stroma is 8 in light

40
Q

what occurs in the calvin cycle? (5)

A

anabolic reaction, building carbohydrates from smaller molecules using energy

carbon eters the cycle through CO2 and leaves as sugar

spends ATP and consumes NADPH

provides glyceraldeyhyde 3 Phosphate (G3P)

for one G3P, it takes 3 cycles and fixes 3 CO2

41
Q

Phase 1 of the calvin cycle (3)

A

aka carbon fixation

incorporates each CO2 one at a time, attaching to a 5 C sugar called RuBP (catalyzed by Rubisco)

product splits in half to form 2 molecules of 3-phosphoglycerate

42
Q

Phase two of the Calvin cycle (6)

A

aka reduction phase

each molecule of 3-phosphoglycerate receives an additional P group from ATP and becomes 1,3-bisphosphoglycerate

the electron from NADPH reduces the above molecule

above molecule loses its p group and becomes G3P

the carboxyl group gets reduced to an aldehyde group

for every 3 CO2, 3 G3P is formed, but 5 G3P is used during the process

43
Q

Phase 3 of the Calvin cycle (3)

A

aka regeneration of RuBP

Carbon skeleton of five molecules of G3P are rearranged in the last steps into three RuBP

spends three more molecules of ATP

44
Q

What are C3 plants? (2)

A

plants that fix carbon using rubisco to add CO2 to RuBP

during hot temperatures, stomata closes and prevents CO2 intake

45
Q

what is Photorespiration (6)

A

when plants bind using O2 instead of CO2

results with a 2C being released, where peroxisomes and mitochondria rearrange it to release as CO2

Uses ATP

Produces no sugar

decreases photosynthetic output

prevent damage due to excessive light

46
Q

Where did photorespiration originate?

A

ancient times having much less O2 in the atmosphere, so excluding O2 in the cycle made little difference

47
Q

What are C4 plants?(5)

A

during carbon fixations, produces a four-carbon compound as its first product

contains two types of photosynthetic cells- bundle-sheath and mesophyll

Calvin cycle is confined to the chloroplasts in bundle-sheath cells

Preceded by incorporation of CO2 into mesophyll cells

contains only PS1

48
Q

what are bundle-sheath cells?

A

bundles around veins of leaves

49
Q

What are mesophyll cells?

A

found between bundle-sheath cells and leaf surfaces

50
Q

Calvin cycle in C4 plants part 1 (4)

A

Carried out by PEP carboxylase found in mesophyll cells

Adds CO2 to PEP forming 4C product oxaloacetate

PEP has no affinity for O2

PEP carboxylase is more efficient than rubisco because it cannot fix O2

51
Q

Calvin cycle in C4 Plants part 2

A

The C4 product is exported to bundle sheath cells through plasmodesmata

4C compounds release CO2 which is reassimilated into organic material by rubisco

regenerates pyruvate, transported to mesophyll

ATP is used to convert pyruvate to PEP

52
Q

How is ATP regenerated in C4 cells?

A

bundle-sheath cells carry out cyclic electron flow

53
Q

How do rising CO2 levels affect plants? (3)

A

Advantages to C3 plants as it prevents photorespiration
- Temperatures rise as well though, so it can induce an opposite effect

C4 plant remain unaffected

BI157 (21 decks)

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