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SBI4UN > photosynthesis + Calvin cycle > Flashcards

photosynthesis + Calvin cycle Flashcards

1
Q

what are pigments

A
  • capture electromagnetic radiation to begin photosynthesis
  • located in membrane of thylakoids
  • found in clusters of photosystems
  • many kinds: chlorophyll, carotenoids, phycoerthyrin, and phycocyanin
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2
Q

what are pigments absorbing

A

specific wavelengths or photons of light

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3
Q

what are lanellae

A

membrane holding thylakoids and grant

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4
Q

what does the absorption spectrum show

A
  • shows which wavelengths (colours) of light are absorbed by the pigments and which are not
  • which are reflected or visible, ex. cholorphyll absorbs red and blue light and rejects green light
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5
Q

what is beta carotene

A

absorbs no yellow and red, so it appears orange

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6
Q

pigment: choloprhyll (a, b)
absorbs which wavelengths? and which wavelengths does it not absorb?

A

blue and red-absorbed

green- not absorbed

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7
Q

pigment: carotenoids
absorbs which wavelengths? and which wavelengths does it not absorb?

A

violet to green light is absorbed

wavelengths that aren’t absorbed are deeply coloured yellow, orange, or red.

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8
Q

pigment: phycobilins
absorbs which wavelengths? and which wavelengths does it not absorb?

A

blue and green light are absorbed

red light is reflected, appears red

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9
Q

what is chlorophyll?

A
  • pigment that provides the green colour to plants
  • helps the plants conduct photosynthesis by absorbing sunlight
  • helps the body treating hemoglobin deficiency disorders, such as anemia and thalassemia bc it has similar structure to hemoglobin
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10
Q

what is carotenoids?

A
  • pigments in bacteria, archae, fungi, plants, and algae
  • involved in photosynthesis and photo-protection
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11
Q

what is phycobilins?

A

any of a group of red or blue photosynthetic pigments present in some algae.

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12
Q

the structure of chlorophyll?

A

phytol tail, non polar” anchors pigment into the thylakoid membrane

porphyrin ring: central mg, absorbs light energy and transfers it to an electron

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13
Q

cholorophyll vs hemoglobin

A

– tbd

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14
Q

where does the Calvin cycle occur

A

in the storma (the inner part of the cholorplast)

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15
Q

how does eating too many carrots cause your skin to turn orange

A
  • carotenemia is present in carrots, and is a precursor (precedes) vitamin A and is stored in the fatty tissue of the body.
  • the excess beta-carotene can accumulate in the skin and subcutaneous fat.
  • The body uses beta-carotene to produce vitamin A, an essential nutrient for vision, immune function, and skin health. However, it only converts the necessary amount of beta-carotene into vitamin A and eliminates the excess. The leftover beta-carotene that’s not converted into vitamin A can build up and manifest as a yellowish or orange discoloration, especially in areas where the skin is thicker, like the palms of the hands, soles of the feet, or the face.
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16
Q

what is photo-protection

A

mechanisms that prevent light energy from inducing damage

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17
Q

what is the stroma

A

the inner part of the chloroplast

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18
Q

what do the light independent reactions of the Calvin cycle require?

A

atp and nadph, and the reactions also require atmospheric co2 from the air which enters the leaf through stomata

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19
Q

what will the Calvin cycle produce

A

these reactions will produce glucose

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20
Q

first step in the light independent reaction

A

A) the cycle begins with: CARBON FIXATION where 3 co2 molecules combine with 3 five carbon acceptor molecules called RuBP, which produces six 3 carbon molecules of 3PG

  • the enzyme rubisco catalyzes this reaction (is the most abundant protein in the world)
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21
Q

if the rubisco enzyme contains the most abundant proteins on earth, why does it catalyze so slowly?

A

Evolutionary heritage: Rubisco is an ancient enzyme that has been conserved through evolution. The enzyme evolved when the Earth’s atmosphere had a different composition than it does today. At that time, there were higher concentrations of carbon dioxide, which allowed for its relatively slower catalytic activity to be sufficient for the prevailing conditions.

Imperfect catalysis: Rubisco is known for its imperfections, which contribute to its slower catalytic rate. One of the major challenges of this enzyme is its tendency to also react with oxygen, a process called photorespiration, which competes with its primary function of fixing carbon dioxide. This inefficiency is known as the oxygenation reaction and leads to a loss of energy and carbon compounds, preventing co2 fixation

Complex structure: Rubisco has a relatively complex structure, which might also contribute to its slower catalytic rate. Its active site is not perfectly optimized for the catalysis of carbon fixation, which adds to its inefficiency.

22
Q

what is step 2 of light independent reactions

A
  • the 3pg molecules are phosphorylated by ATP to form 1,3BPG
  • these 1,3 BPG are then reduced by NADPH and dephosphorlayed to leave molecules of G3P
23
Q

what is step 3 of light independent reactions

A
  • ruBP regeneration molecules of G3P are phosphorylated by ATP to re-generate the initial electron acceptor molecules
  • it takes 2 molecules of G3P to make one molecule of ATP, thus, it takes 6 CO2 to make one glucose which can be:
    1) converted into Beta-glucose (used as structural materials)
    2) used in cellular walls (plant cells have mitochondria)
    3) stored as energy
    4) used as fructose for fruiting bodies
24
Q

what factors affect photosynthetic rate?

A
  • the rate at which photosynthesis occurs is affected by environmental factors

factors: light intensity, temperature, co2 concentration, and o2 concentration

25
Q

what is photorespiration

A
  • occurs under increased light/heat when rubisco reacts with oxygen rather than co2 (undergoing photosynthesis)
26
Q

what is transpiration

A
  • loss of h2o out of stomata (pores) of plants during gas exchange (o2 and co2) while photosynthesizing and respiring
27
Q

what is water use efficiency

A
  • how good a plant is at bringing in co2 without losing too much water
  • the ratio of rate of photosynthesis (energy generation) to rate of transpiration (h2o lost)
28
Q

what is adaptive value

A
  • all combined influences of characteristics that affect the fitness of an individual or wavelength: action spectrum for photosynthesis population
  • same concept as fitness

-“added ability to cope with environment”

29
Q

how many active sites does Rubisco have

A

2 active sites:
- as temperature increases it can grab oxygen instead of co2 and vice versa, sometimes rubisco gets confused between the two active sites

30
Q

how does rubisco get confused between the active sites?

A
  • when the concentration of oxygen is high or the carbon dioxide levels are low, RuBisCO can also bind oxygen instead of carbon dioxide due to their similar sizes and shapes. This results in the oxygenase activity, leading to the process of photorespiration, which is less efficient in terms of producing organic compounds.
31
Q

as temperature increases what happens to rubisco

A

makes mistakes with which molecule (Co2 vs o2) to bind with

32
Q

Light intensity vs rate of photosynthesis

A

As the light intensity increases, the rate of photosynthesis increases, and then levels off.
■ Light can be considered a SUBSTRATE, ultimate source of electrons
■ Enzymes: PI, PII, ETC, NADP+ Reductase
■ Leveling off represents maximum rate of photosynthesis.

33
Q

Temperature vs Rate of Photosynthesis

A

Initially, as temperature increases, the rate of photosynthesis increases.The rate peaks and then starts to decreases because:

■ Collisions
■ Enzymes become ineffective. Which ones?
Why?
■ Denaturation?
■ Transpiration & PhotoRespiration
■ Stomata may start to close, limiting water loss and entry of carbon dioxide.

34
Q

Level of CO2 vs Rate of photosynthesis

A

■ As the level of CO2 increases, the rate of photosynthesis increases, and then levels off.
■ Leveling off represents maximum rate of photosynthesis.
■ Effect of a substrate on Enzyme Rate
■ RuBisCO

35
Q

Limiting Factors vs Rate of Photosynthesis

A

Law of Limiting Factors: rate of a physiological process will be limited by the factor which is in shortest supply. Any change in the level of a limiting factor will affect the rate of reaction.

36
Q

What is cyclic flow vs non cyclic flow?

A

In cyclic photophosphorylation, the electrons get expelled by photosystem I and they return to the system. On the other hand, in non-cyclic photophosphorylation, the electrons that are expelled by the photosystems do not return.

37
Q

Is Calvin cyclic or non cyclic flow?

A

Cyclic**(?)

38
Q

What are sacs referring to

A

thylakoids

39
Q

what are Stacks referring to

A

grana

40
Q

what are photosystems

A

clusters that pigments are embedded in

41
Q

T/F: visible light is the main form of light energy?

A

F; only a small portion of light is coming from the sun

42
Q

what are the catching pigments called and what do they do?

A

antenna pigments; collect light energy from the sun and transfer it to reaction centers

43
Q

what happens when light hits a leaf

A

When light hits a leaf, it travels through the layers into the chloroplasts where it reaches the thylakoid membranes.

These have pigment molecules embedded in them, in bundles called photosystems, that absorb light energy. This pushes electrons from “ground state” to an excited state. The electrons are then grabbed into an electrons transport chain where they are used to pump H+ in from the stroma, to create an electrochemical gradient that produces ATP.

44
Q

what happens to the electrons that are used to pump protons

A

The electrons are then used to reduce NADP+ into NADPH. These electrons and ATP molecules are then used in the Calvin Cycle to make carbohydrates.

45
Q

how are electrons at P2 replaced?

A

This is done by oxidizing water to produce Oxygen gas. Photosynthesis is responsible for producing nearly all the oxygen in the atmosphere.

46
Q

What happens when electrons leave Photosystem 1

A

taken up by an electron acceptor

47
Q

is Calvin cycle a light or dark cycle?

A

dark cycle; CYCLIC PROCESS INVOLVED IN CARBON FIXATION → ABSORBING C02 FROM THE AIR AND ATTACHING IT TO ORGANIC MOLECULES

48
Q

stomata vs stroma

A

Stoma: Stoma (singular form of stomata) is a very small microscopic pore present on the surface of a leaf enclosed by a pair of guard cells.

Stroma: Stroma is the lumen of chloroplast which is a green-colored double-membranous cell organelle meant for photosynthesis.

49
Q

what is the final electron acceptor? in light vs dark

A

light: nadp+

dark: co2

50
Q

summarized version of calvin

A

The Calvin cycle is the second stage of photosynthesis, occurring in the stroma of chloroplasts, where atmospheric carbon dioxide is converted into glucose through a series of enzyme-driven reactions. The cycle involves carbon fixation, reduction, and regeneration of RuBP, ultimately producing sugars that serve as energy storage for the plant.

3RUBP AND 3CO2 FORM 6PGA- use 6 atp and 6 nadph (which store energy from light reactions to generate 6 molecules of g3p), which contain more electrons

the other 5 molecules of g3p and energy from 3 atp molecules produce 3 molecules of rubp

RUBISCO—CO2—RUBP= 2, 3-PGA atoms

ATP and NADPH are used in the reduction phase, 1 molecule of 3-PGA is phosphorylated by ATP and reduced by NADPH to form G3P

G3P will be used to regenerate RUBP, G3P molecules can be used to make carbs

3 CO2 released: 1 G3P will be released, glucose synthesis

51
Q

summarized light rcn

A

photons of light hit chlorophyll (which absorbs light) in photosystem 2
- electrons in the chlorophyll are excited and are passed to an electron carrier
- meanwhile, water splits and releases electrons which supply the electrons lost at photosystem 2, byproduct is oxygen and protons, protons are released to lumen

  • excited electrons move to cytochrome complex, and some of their energy is used to transport more protons into the lumen, the second carrier (a protein inside the lumen) transport electron to photosystem 1.
  • photons of light hit chlorophyll in photosystem 1 and excite electrons that are passed to the third carrier where they are then recycled or are used to form NADPH,
  • some of the electrons energy are used to create the proton gradient
  • absorption of light
  • P2: light energy will be used to excite electrons that are transferred along the ETC to aid with chemosmosis (drive of protons moving into the thylakoid space)
  • water will split to provide electrons for P2
  • P1: light energy will excite electrons again which will be transferred to another ETC–these electrons and protons that are from the second ETC will reduce NADP to NADPH
  • O2 generated by H2O is a byproduct, released into the atmosphere
  • final acceptor: NADP+ (reduction to occur, electrons will be transferred to form NADPH, then used in the Calvin cycle)

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