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HORT 1102 - Botany > 10: Photosynthesis > Flashcards

10: Photosynthesis Flashcards

1
Q

Which two factors affect photosynthetically active radiation in plants?

A
  1. type of light received

2. wavelengths received

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2
Q

What are the 4 main pigments in plants?

A
  1. Chlorophyll A
  2. Chlorophyll B
  3. Carotenoids
  4. Anthocyanin
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3
Q

Which are the 2 photosynthetically active pigments?

A

Chlorophyll a and b - predominantly a

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4
Q

Describe chlorophyll as photosynthetically active pigments

A

(A & B) Green pigments that help capture the sun’s energy by absorbing a lot of blue and red light and reflecting the other light wavelengths

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5
Q

Describe carotenoid pigments and list the two kinds

A

Orange pigments that are leftover in the leaf after the chlorophyll exits in the fall
- absorb mostly blue light and reflect the rest

  1. carotene
  2. xanthophyll
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6
Q

Describe anthocyanin pigments

A

Red pigment located inside the vacuole that does NOT contribute to the light dependent reactions and is purely a colour

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7
Q

Where is chlorophyll located?

A

Embedded in stacked membrane sacs (thylakoids) within chloroplasts of mesophyll cells

Also located in guard cells

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8
Q

T or F: Chlorophyll is a green pigment that reflects green light and absorbs blue and red light?

A

TRUE photosynthesis does not use green light

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9
Q

Which chemical is the key component of the chlorophyll molecule? What is attached to it?

A

Magnesium in the centre of the chemical rings with CH2 and CH3s attached

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10
Q

What is the chemical formula for photosynthesis?

A

6CO2 + 6H2O inputted into the chlorophyll and in the presence of light energy and enzymes –> C6H12O6 (glucose) + 6O2 + water

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11
Q

What are the inputs required for photosynthesis?

A

Carbon dioxide
Water
Sunlight
Enzymes

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12
Q

What are the products of photosynthesis?

A

Oxygen gas
Glucose (sugar)
Water

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13
Q

What are the two distinct steps of photosynthesis?

A
  1. Light reactions

2. Light independent reactions

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14
Q

What are thylakoids?

A

Stacked membrane sacs inside the chloroplasts of mesophyll cells that contain chlorophyll

The site of the light reaction step of photosynthesis

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15
Q

Describe the light reaction step of photosynthesis

A
  • Rxns take place in the thylakoid membranes (Grana)
  • light energy is captured and converted to ATP and NADPH
  • Oxygen is produced by the water burning and released out the stoma into the atmosphere
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16
Q

Describe the light independent reaction step of photosynthesis

A
  • The Calvin Cycle (C3 cycle) take place in the stroma of chloroplasts
  • ATP & NADPH produced by the light runs are fed into the calvin cycle to fix the atmospheric CO2 into a 3-Carbon compound
  • This requires RuBisCO ENZYME
  • products of the CC = starch and glucose
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17
Q

What is ATP?

A

Adenosine Triphosphate

  • temporarily, short-lived stored energy of biological systems
  • the energy produced the light rxn stage of photosynthesis that cells need to do their work - cells cannot use the sugar directly, it needs to be converted into ATP
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18
Q

Describe how photosynthesis happens in leaves?

A

Light passes through the transparent epidermal cells on the surface of the leaves and into the thylakoid membranes in the chloroplasts

and CO2 comes in through the stoma and diffuses into the liquid environment inside the cells and moves into the chloroplasts

water is produced by PS and transpiration can also leave the stoma

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19
Q

Describe the stroma

A

The liquid filling of the chloroplasts that surrounds the thylakoids

Where the high energy compounds (ATP & NADPH) and CO2 enter to be converted into sugar

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20
Q

What are the 2 structures of chloroplasts?

A
  1. Grana: all the thylakoids

2. Stroma: fluid filling in chloroplasts

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21
Q

Where does the light dependent reaction occur?

A

In the grana (all the thylakoids)

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22
Q

How are solar panels similar to leaves?

A

They capture solar energy and convert it to a form of energy that can be used or stored just like plants

23
Q

What are C3 plants? How does photosynthesis occur?

A

Plants that contain 3-carbon compounds where photosynthesis, carbon fixation and the Calvin cycle occur in a SINGLE chloroplast

24
Q

When does photorespiration occur?

A

When temperate plants close their stomata early in the afternoon due to periods of very hot dry weather because the threat of water loss is too high

25
Q

What is photorespiration?

A

When the stomata is closed early causing a lack of CO2 intake, the enzyme RuBisCO which usually captures CO2 in the Calvin cycle to produce sugar will use O2 instead –> up to half of the fixed carbon produced is returned as free CO2 and not sugar (CO2 is a waste product)

26
Q

What are the damages of photorespiration?

A

Loss of CO2 intake can lead to damage because it’s required for photosynthesis

27
Q

What are C4 & CAM plants? Give examples of each

A

Plants adapted to environments where CO2 may be limited (hot and dry) so they STORE CO2 in a chemical form inside the ‘leaf’ cells to be available for photosynthesis even if the stomata is closed

ex C4: corn, tropical grasses
ex CAM: cacti, jade, stonecrops, orchids, bromeliads

28
Q

How does photosynthesis occur in C4 plants?

A

C4 plants have 2 distinct kinds of chloroplasts:

  1. mesophyll chloroplasts
    - CO2 is quickly converted into malate or aspartate (C4 intermediate)
    - occurs in the thin-walled mesophyll cells and is then passed to the thick-walled bundle sheath cell
  2. bundle sheath chloroplasts
    - Surrounds the vascular bundle (different physically)
    - where the Calvin cycle occurs
    - takes the 4-C acid to make CO2 as in the regular CC by RuBisCO enzyme creating sugar
29
Q

T or F: C4 plants can have photosynthetic rates 2-3x higher than those of C3 plants in hot sunny environments? Why/why not?

A

True because the stomata will be closed in the temperate plants and photorespiration will occur rather than the regular photosynthesis that will be happening in the C4 plants

30
Q

How does photosynthesis occur in CAM plants?

A
  • Photosynthesis and initial carbon fixation occurs at NIGHT and a 4-C acid is stored in the cell’s vacuole during the daytime
  • Calvin Cycle operates as usual in the chloroplasts during the day using the stored 4-C acid (malic acid) to convert it into CO2 to be used for photosynthesis during the daytime when stomata are closed
  • oxygen is released in the daytime when the sun burns the water and the stomata are open
31
Q

What are the main differences between C3, C4, & CAM photosynthesis?

A

C3:

  • 1 type of chloroplast with CO2 conversion in the stroma
  • most temperate climate plants

C4:

  • 2 distinct types of chloroplast
  • MC: produces C4 molecules
  • BSC: does the CC
  • hot and dry climates

CAM:

  • 1 chloroplast where malic acid is produced and the CC occurs
  • hot and dry climates
32
Q

T or F: There is approximately 400ppm CO2 in our atmosphere currently? And plants extract huge amounts daily?

A

True

33
Q

How much water is needed for photosynthesis? And is it a limiting input?

A

less than 1% is required so no, it is not limiting

34
Q

What are the 6 different light qualities?

A
  1. Daylight
  2. Incandescent
  3. fluorescent
  4. halogen
  5. Cool white LED
  6. warm white LED
35
Q

Describe the quality of daylight

A
  • broadspectrum light (all visible wavelengths)
  • intensity is even across the wavelengths
  • direct sunlight is highly intense
36
Q

Describe the quality of incandescent light

A
  • Most of the colder wavelengths are low intensity
  • Produce high intensity red lights
  • Produce heat
37
Q

Describe the quality of fluorescent light

A

Provide good light but intensity is focused in green-red
Green light is useless to plants
Orange is slightly useful
Not bad light for us, but NOT GOOD for plants

38
Q

Describe the quality of Halogen light

A

Burn a lot more power - more red

More of the red wavelengths, not much blue

39
Q

Describe the quality of cool white LED light

A

Produce a lot of blue light - high intensity
And in green range
Little in the red light

40
Q

Describe the quality of warm white LED light

A

High green light intensity

More red light intensity

41
Q

What is light quality?

A

describes the wavelengths present (ex. red, blue, green)

42
Q

What is light intensity?

A

How much energy is contained in the wavelengths

43
Q

How does a clear summer day compare to the brightest indoor lights being on in terms of light intensity?

A

Sunlight on a clear day has 70,000 lux vs. the 1200 lux of the indoors

44
Q

What is the unit for light intensity?

A

lux

45
Q

T or F: Most plants need more than 30% of full sunlight to survive

A

FALSE. Most plans ONLY need 30% of the full sunlight

46
Q

What are the two terms for sugar transport in plants?

A
  1. Source-to-sink translocation

2. Pressure Flow Hypothesis

47
Q

What are the sources of sugar and what are the sinks for sugar?

A

Source: chloroplast
Sink: roots or fruits

48
Q

Describe the pressure flow hypothesis

A
  1. Sugar is produced by PS and is loaded into the phloem and unloaded where it is needed (sinks) with help from the companion cells
  2. Water will move from the xylem to the phloem by OSMOSIS to dilute the sugar, creating osmotic pressure to drive the phloem sap (sugars) downward to the roots or fruits to be stored as starch
49
Q

Where is sugar stored if the rate of photosynthesis is higher than the translocation of sugar?

A

Sugar is stored as starch in the chloroplasts of the leaves TEMPORARILY

50
Q

Describe starch

A

A complex carbohydrate consisting of many glucose units joined together

a storage form of glucose

51
Q

What is the process that converts starch back into glucose?

A

Digestion

52
Q

Explain the process of digestion of starch into glucose

A

Starch molecules are digested by enzymes (AMYLASE) to be converted back into glucose

53
Q

At which temperature will enzymes become ineffective and why?

A

32 degrees because they are proteins so they will melt

54
Q

What controls the activity of enzymes?

A

Temperature

HORT 1102 - Botany (11 decks)

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