Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BIOL 1101 > Lecture 6: Photosynthesis > Flashcards

Lecture 6: Photosynthesis Flashcards

1
Q

Photosynthetic organisms

A
  • photoautotrophs
    primary producers that convert SOLAR energy into CHEMICAL energy through complex organic molecules
  • use some of organic molecules as own energy sources
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two stages of photosynthesis

A

1) Light dependent (z cycle)
- pigment molecules capture light energy which is used to synthesize ATP and NADPH

2) Light independent reactions (Calvin cycle)
- uses energy in NADPH (form light dependent) and ATP to convert CO2 from inorganic to organic form (glucose), or other carbon skeletons needed in macromolecules
*** VIA CARBON FIXATION

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The process of photosynthesis is the opposite of…

A

etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Light reactions

A

Photosystem II (PSII) absorbs light, exciting electrons from water molecules, splitting them into oxygen, protons, and electrons. The excited electrons are passed to the electron transport chain.

Electrons lose energy as they move down the chain, and this energy is used to pump protons across the membrane, creating a proton gradient for ATP synthesis.

Photosystem I (PSI) absorbs more light, re-exciting the electrons. These high-energy electrons are used to reduce NADP+ to NADPH.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Calvin cycle

A

Carbon fixation: CO₂ combines with RuBP (ribulose bisphosphate) to form 3-PGA.

Reduction: 3-PGA is converted into G3P (glyceraldehyde-3-phosphate) using ATP and NADPH.

Regeneration: Some G3P molecules are used to regenerate RuBP, allowing the cycle to continue.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where does photosynthesis take place for pro/euk

A

euk=chloroplasts

pro=plasma membrane/cytosol, lack chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Structure of chloroplast

A
  • double membraned

stroma- fluid filled environment in the inner membrane

thylakoid membrane: complex of flattened internal membrane compartments
- stacks: grana
- connections between grand: lamellae
- compartment enclosed by thylakoids: thylakoid lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

lumen means

A

space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

purpose of thylakoids

A
  • absorb light through chlorophyll and carotenoids (pigments)
  • electron transfer
  • ATP synthesis by ATP synthase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Purpose of stroma

A

space around thylakoids..
- site of Calvin cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The photosynthetic Apparatus

A

a) electrons in pigment molecules absorb light energy
b) chlorophyll and carotenoid pigments cooperate in light absorption
c) photosynthetic pigments are organized into photosystems (that catalyze the conversion of light energy to chemical energy)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Excitation

A
  • electron at ground state will move to excited state which is unstable
    absorbs energy If moving away from nucleus
    releases energy when moving towards nucleus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Fate 1 of excitation

A

1) energy released as heat or as light (fluorescence), electron returns to ground state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

fluroscence

A
  • Light of a longer wavelength:

IN EXCITATION FATE 1:
-electron can just release that energy as light
- emmitted won’t have an equal amount of energy (longer wavelength) than what was absorbed, meaning the electron will return to ground state by emitting a less energetic photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Fate 2 of excitation

A

energy transferred to a neighbouring pigment molecules by inductive resonance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Inductive resonance:

A

transfer excites second pigment and the first pigment returns to ground state

The transfer of solar energy from one pigment molecule to other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Fate 3 of excitation

A

Excited state electron itself is transferred to nearby electron accepting molecule, the primary acceptor
- complete transfer of excited electron and energy so it can energize other molecules such as NADP+ or pump protons to increase membrane potential
* chlorophyll a is the only pigment that can do this *

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Pigments

A

chlorophylls- major photosynthetic pigment

carotenoids- accessory pigments that absorb light energy and pass it to chlorophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Chlorophyll a

A
  • harvests light in blue/violet/red light (absorbs these wavelengths the strongest)
  • only one to give excited electrons to primary acceptor (fate 3)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What do chlorophyll and carotenoids do together

A
  • absorb photons during photosynthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Englemen’s Experiment

A
  • most growth of aerobic algae (spirogyra) in
    violet/blue wavelength and red wavelength because the algae is doing the most photosynthesis (O2 is a byproduct)
  • least growth in green/yellow wavelength, meaning the least amount of photosynthesis would occur which is why its reflected and plants appear green
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

As more plants enter dormancy, pigments

A

die off, hence the colour of leaves during fall and winter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

photosystems

A
  • photosynthetic organisms that capture solar energy (photons of light to oxidize a reaction centre chlorophyll with the electron being transferred to primary electron acceptor)
  • each photosystem is composed of a large antenna complex of pigments that surrounds a central reaction centre (primary electron acceptor)

PSII with P680
PSI with P700
* numbers indicate the wavelength of light they absorb the most *

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Linear electron transport

A

IN thylakoid membrane
1) Light energy is absorbed by chlorophyll, exciting electrons to a higher energy state.

2) Excited electrons are transferred to an electron transport chain (ETC), starting with Photosystem II (PSII).

3) Electrons lost by PSII are replaced by splitting water molecules, releasing oxygen as a byproduct.

4) As electrons move through the ETC (which includes plastoquinone, cytochrome b6f, and plastocyanin), protons (H⁺) are pumped into the thylakoid lumen, creating a proton gradient.

  • use photon to re-excite electrons because they lost 1/2 their energy at this point (when meeting with P700 *

5) Electron sits on Ferredoxin (outer membrane of thylakoid) and donates electrons to NADP+ to NADPH which is catalyzed by NADP+ reductase (brought to krebs) ** using 2e- from etc and proton from aq environment **

6) ATP Synthase: Driven by H+ force via electrochemical gradient: three things contribute:

1) Splitting of water in lumen
2) PQ (hydrophobic core) picks up electrons and protons for neutrality, and give up H+ in lumen
3) NADPH redox forms NADP+ by losing H+ to strong side

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Summarized Transport

A

1) P680 Redox
2) Plastoquinone Pool Redox
3) Electron transfer from cytochrome complex and shuttling by plastocyanin
4) Redox of P700
5) Electron transfer to NADP+ by ferradoxcin (NADP+ Reductase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Chemiosmotic synthesis of ATP

A
  • uses proton motive force established across thylakoid membrane to synthesize ATP
  • H+ force (via osmosis)
  • uses atp synthase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

The linear use of light to synthesize ATP

A
  • not spontaneous since you use light energy
  • Positive enthalpy: since the e- energy in NADPH is greater than in H2O
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

To get 1 electron down the ETC from PS2 to NADP+ takes…

A

2 photons of light
- one photon absorbed by each photosystem

2H2O = 4H+ + 4e-+ O2

  • For 4 electrons, need a total of 8 photons of light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Cyclic electron transport

A
  • PS1 can operate independently of PS2 by using cyclic electron flow (to get extra ATP)
  • electron transport from PS1 to ferredoxin is not followed by electrons going to NADP+ reductase complex
  • reduced ferredoxin donates electrons back to the plastoquinone pool
  • USE THIS TO MAKE MORE ATP WHICH IS IMPORTANT IF THE ORGANISM UNDERGOES CHANGES TO ENVIRONMENT
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

which comes first in the transport chain: PS1 OR PS2

A

PS2, named based on time they were discovered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Cyclic E- Transport summarized

A

NO NADPH
YES ATP

32
Q

What happens to CO2 in Calvin cycle

A

reduced and converted into organic substances (because co2 is an inorganic form)
- NADPH = provides electrons and H+
- ATP = provides additional energy

33
Q

What is carbon fixation

A

Capturing CO2 molecules with the key enzyme RUBISCO
- Rubisco acts as a carboxylase in Calvin cycle
- will do either carboxylation or oxygenation

34
Q

Calvin cycle summary

A

1) carbon fixation: CO2 will be fixated onto RUBP via rubisco enzyme to form a 6 C intermediate that is too unstable and will break down to form 2 3-PGA

2) ATP and NADPH from the light dependent reactions will convert the 3-PGAs into G3P

3) ATP and NADPH will be used to regenerate RUBP to keep the cycle going

4) G3P can be used to form glucose and other carbohydrates for fuel

35
Q

How many times is Calvin undergone

A

three times to produce a single three-carbon GA3P molecule (check textbook)

and six times to produce a six-carbon glucose molecule.

36
Q

G3P

A

starting point for synthesis of
- sucrose
- starches
- cellulose
- amino acids
- fatty acids and lipids
- proteins
- nucleic acids

37
Q

photorespiration

A

Rubisco binds to 02 instead of con leading to a wasteful by product forming and u d in photosynthetic efficiency bc of ROS

38
Q

O2 is a

A

competitive inhibitor

39
Q

Glycolate is

A

toxic

40
Q

Limit photorespiration

A
  • pump bicarbonate anion into cells (converting into co2) ALGAE
  • spatially separate c4 cycle from Calvin cycle (do them in diff spaces) [C4]
  • temporally separate c4 cycle from carbon cycle (not at same time) [C4]
41
Q

Photosynthesis Dilemma

A

problem: photorespiration and water loss
- leaf covered in waxy cuticle: prevents water loss BUT prevents rapid diffusion of gases into leaf
- stomata: control high rates of gas exchange + minimizes h2o loss [pores] CO2 IN O2 OUT

DILEMMA: need to open stomata to let in CO2 but need to keep them closed to conserve water

42
Q

C4 Photosynthesis

A
  • increases concentration of CO2 relative to O2 near Rubisco to minimize photorespiration
  • CO2 is combined with PEP to produce 4-C intermediate (oxyloacetate)
  • PEP enzyme has no oxygenate activity
  • When O2 conc is low, oxyloacetate is oxidized to release CO2 (converted to malat–bundle sheath cells–decarboxylated)
  • CO2 enters Calvin by binding to rubisco
43
Q

type of cycle: Calvin

A

C3 cycle because a 3C intermediate is produced first (3PGA)

44
Q

Example of spatial separation of C4 and Carbon cycle

A
  • CO2 is captured in mesophyll cells close to the surface of leaves where PEP carboxylase is NOT affected by high O2 conc
  • Malate goes deeper in tissue (converted from OAA) and then decarboxylates in bundle sheath cellsoxidized to pyruvate
  • This is a place where O2 is less abundant and CO2 is more concentrated, photorespiration is reduced and the Calvin cycle is enhanced
45
Q

Temporal separation of C4 and carbon

A

CAM PHOTOSYNTHESIS

  • night: plants open stomoata to capture co2 with c4 cycle
  • day: plants close their stomata to conserve water, and malate is oxidized to release CO2 in chloroplasts
    +use o2 to cellular respiration
    + stomata close as temp increases
    + conc of o2 is lower
46
Q

Z scheme summarized

A

NOTE: chlorophyll a will absorb light energy that excites electrons that are brought to ETC starting with PS2

1) H2O will split at PS2 where they will release O2, H+, and electrons that will be used for the ETC

2) PS2 will excite the electrons by using light energy

3) Electrons move to PQ where they will be held

4) Electrons will be sent to cytochrome complex where they will be used in the etc to pump H+ into the thylakoid lumen

5) Electrons will be sent to another intermediate, PC

6) Electrons will be brought to PS1 where they will be re-energized with light energy

7) Electrons will be used to reduce NADP+ to NAPDH

47
Q

bundle sheath cells

A

photosynthetic cells around leaf

48
Q

mesophyll cells

A

tissue located between the two epidermal cell layers of the leaf

49
Q

shorter wavelength blue light vs red light

A

red light has longer wavelengths and thus photons of less energy

50
Q

3 possibilities when light interacts with matters

A

1) reflected off the object
2) transmitted through the object
3) absorbed by the object
- light is absorbed when the energy of a photon is transferred to an electron within a molecule which excites the electron

51
Q

molecules that are efficient at absorbing photons of specific wavelengths

A

pigments
- they have a region of carbon atoms are covalently bonded to each other with alternating single and double bonds (conjugated system)
- results in delocalization of electrons=electrons are available to absorb energy

52
Q

autotrophs

chemoautotrophy

A

drive conversion of co2 into organic form through light

chem…- bacteria version, use chemical compounds for energy like H2S and Fe2+

53
Q

photosynthesis is not present in which domain

A

arches, but halo bacteria do harvest light energy to pump protons across membrane for ATP synthesis

  • but light energy isn’t use to convert CO2 to organic form so they aren’t photosynthetic
54
Q

the energy of a photon

A

must match the amount of energy needed to move a delocalized (not associated with an atom) electron from its ground to a specific excited state

55
Q

if energies of photon and electron don’t match

A

photon of light isn’t absorbed or reflected and it instead transmitted through the molecule or reflected off molecule

56
Q

what determines the colour of pigments

A

ability to absorbed specific wavelengths

57
Q

how can we measure the rate of photosynthesis

A

rate of O2 produced or CO2 consumed

58
Q

where are the enzymes of the Calvin cycle found

A

cytosol

59
Q

absorption spectrum

A

plot of how much light is intercepted by the pigment (absorbed) as a function of wavelength

60
Q

chlorophyll has 2 excited states

A

1) one that matches energy of a blue photon
2) matches energy of a red photon

61
Q

action spectrum

A

plot of effectiveness of light of a particular wavelength in driving a process

62
Q

what process gets a chlorophyll molecule into a state where it readily gives up an electron (oxidized)

A

absorption of light

P680, P700 are examples

63
Q

NADPH production does what

A

enhances the gradient across the thylakoid membrane

64
Q

the process of using light to generate ATP

A

photophospohrylation

65
Q

P1 can function independently of P2

A

cyclic electron transport

-Fd donates electrons back to PQ pool so its continually reduces and oxidized to keep moving P+ across membrane

66
Q

unlike linear electron transport, NADPH is not formed

A

during cyclic electron transport

67
Q

How does the plant control which pathway electrons should be sent out

A

sensory proteins in chloroplast control ratio of ATP and NADPH

68
Q

how many photons of light are required to generate 1 molecule of NADPH by linear electron transport

A

2 photons

69
Q

the Calvin cycle is what type of reaction

A

endergonic, needs light to occur
- requiring abundance of energy supplied by ATP and electrons in NADPH

70
Q

3 turns of Calvin

A

= 3 CO2 into 3 RuBp to produce 6 3-PG

  • 6 ATP and NADPH are consumed
  • 5 G3P are used to regenerate 3 RuBP, requiring 3 ATP
71
Q

what role does the chloroplast genome play in the synthesis of RuBisCo

A

The chloroplast genome encodes the large subunit of RuBisCo, essential for assembling the enzyme complex, while the nuclear genome encodes its small subunits.

72
Q

O2 binds to RuBisCo

A
  • makes enzyme act as an oxygenate instead of carboxylase
  • forms toxic glycolate which leads to reactions releases co2 (wasteful)
73
Q

algae pump bicarbonate ion purpose

A

prevention of rubisco binding to O2 (photorespiration)
- because in aquatic environment there isn’t enough CO2 to saturate RuBisco, algae use bicarbonate to prevent photorespiration (converted in cytosol)

even though solubility of gas decrease as temperature increases, co2’s solubility decreases faster

74
Q

which photosystem makes o2

A

2

75
Q

CHECK GRADE 12 BIOLOGY PHOTOSYNTHESIS FLASHCARDS FOR C3,C4,AND CAM

A

ok

76
Q

difference of g3p in cell resp and photosynthesis

A
  • cell resp: product of catabolic pathways
  • photo: is used by anabolic pathways

BIOL 1101 (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions