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Gymnastics and tumbling > Chapter 20.1 (Photosynthesis) > Flashcards

Chapter 20.1 (Photosynthesis) Flashcards

1
Q

Key parts of chlorophyll structure?

A

Long hydrocarbon tail - is lipid soluble and anchors molecule in thylakoid membrane.
Porphyrin hydrophilic head (contains Mg2+) - lies on surface of the membrane next to the stroma
flat head - Lies parallel next to the membrane surface to capture light
Modified side chains - alters absorption spectrum

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2
Q

Advantages of possessing many different pigments

A
  • Wider range of wavelengths of light can be absorbed
  • More light energy is absorbed
  • More LDRs - more ATP - more red. NADP produced - more LIR - more glc produced.
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3
Q

Types of photosynthetic pigments?

A

Chlorophyll
- Chlorophyll a, chlorophyll b

Accessory pigments

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4
Q

Chlorophyll a P680 information

A

Appears yellow- green
P680. (pigment 680) - can absorb wavelengths of 450nm (blue), and peak absorption at 680nm.
Found in photosystem II
Usually embedded in granal lamellae

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5
Q

Chlorophyll a P700 information

A

P700 - can absorb 450nm (blue), and peak absorption at 700nm.
Appears yellow-green
Found in photosystem I
Usually embedded in intergranal lamellae

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6
Q

Accessory pigments information

A

Called Carotenoids
Reflect yellow and orange light
Absorb blue light
Don’t have a porphyrin group
Absorb wavelengths of light not absorbed by chlorophyll and pass energy to chla at the base of the photosystem.
Eg, carotenoids (orange), xanthophylls (yellow)

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7
Q

Chlorophyll b information

A

Absorbs light between 500-640nm. Appears blue-green

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8
Q

Photosystems information

A

Arranged as funnel-shaped structures that are held in place by extrinsic proteins.

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9
Q

Where are photosynthetic pigments found?

A

In thylakoid membranes
of lamellae and grana
and contain different collections of photosynthetic pigments.

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10
Q

3 general types of changes to cells when they differentiate to become specialised cells?

A
  • Change in Shape
  • Change in Organelles present
  • Change in Chemical Composition in cell

SOC

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11
Q

How are the palisade mesophyll tissue adapted to increase efficiency of PHS?

A

NOT FINISHED!!!

COME BACK TO!!!

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12
Q

2 phases of PHS?

A

Light dependent reactions

  • Photolysis of water
  • Electron Transport chain
  • Chemiosmosis.

Light independent reactions/ Calvin cycle

  • Carboxylation/carbon fixation
  • reduction
  • regeneration
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13
Q

What is photolysis?

A

Light energy is absorbed by chlorophyll and splits water into oxygen, H+ and e-.

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14
Q

What are the protons from photolysis used for?

A
  • Used in Chemiosmosis to produce ATP when they are pumped from thylakoid space into stroma.
  • Used to reduce NADP In stroma to form reduced NADP (which is later used in light independent reactions) with electrons from photosystem 1.
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15
Q

What are electrons from photolysis used for?

A
  • Used to reduce magnesium ion in the chlorophyll molecule in photosystem II.
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16
Q

What is O2 from photolysis used for?

A

Used in the plant cell for aerobic respiration. Some diffuses out the stomata to atmosphere.

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17
Q

What is water also responsible for in the plant?

A
  • Maintaining turgidity of plant cell (ensuring plant is erect to maximise light absorption for PHS)
  • Translocation of sucrose
  • Transpiration
  • Opening and closing of stomata via turgidity of guard cells.
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18
Q

How does Carbon dioxide move through the leaf?

A
  • Co2 in atmosphere
  • via stomata
  • substomatal space
  • air spaces between PMC.
  • Across cell wall and c.s.m of PMC
  • Across cytoplasm of PMC
  • Across chloroplast envelope
  • CO2 in stroma of chloroplast
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19
Q

Inputs for the Calvin cycle?

A

3 ATP per turn of the Calvin cycle.

NOT FINISHED

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20
Q

Outputs for Calvin cycle?

A

NOT FINISHED

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21
Q

Factors that affect the Calvin Cycle?

A

pH
Temperature
[CO2]
[RuBisCO]

22
Q

What does RuBisCO stand for?

A

ribulose bisphosphate carboxylase oxygenase

23
Q

What does RuBP stand for?

A

Ribulose bisphosphate

24
Q

How does pH affect the Calvin cycle?

A

Extreme pH changes denatures RuBisCO - disrupts ionic and hydrogen bonds within tertiary structure - allostery - change shape of active site - no/less ESC from - decrease in rate of reaction.

25
Q

How does [CO2] affect Calvin cycle?

A

More CO2 - more ESC - more product made in a given period of time.
- rate will continue to increase until another factor becomes limiting.

26
Q

How does temperature affect Calvin cycle?

A
  • Low temps - decreased number of collisions between AS of RuBisCO and Co2 - less ESC - decr. rate of reaction
  • High temps - disrupts ionic and hydrogen bonds within tertiary structure - allostery - change shape of active site - no/less ESC from - decrease in rate of reaction.
  • Temps above 25C - incr. oxygenase activity of RuBisCO - photorespiration - less carbon fixation and reduced rate of Calvin cycle.
27
Q

Products from GP from photosynthesis?

A

G3P is reduced to TP
Can be converted to aCoA which can then be converted to fatty acids and amino acids.
Production of amino acids requires Nitrates for -NH2 group, and sulphates for R group in cysteine and methionine.

28
Q

Products from TP from photosynthesis?

A

The 2 molecules of Tp can be converted to hexose, eg, glucose.
Glucose can be converted into fructose
Glucose and fructose converted to sucrose: also translocation in phloem sieve tube.
Hexoses polymerised (via condensation reactions) to other polysaccharides, eg, cellulose, amylose, amylopectin (via formation of glycosidic bonds)
TP can be converted into glycerol, which is combined with fatty acids to form triglycerides (lipids)

29
Q

Differences between cyanobacteria and plant cells?

A

Plant cells have thylakoids in chloroplasts arranged as stacks forming grana.
Cyanobacteria have photosystems near their c.s.m and cell wall.

30
Q

Definition of compensation point?

A

The level of light intensity on the light curve where the rate of photosynthesis exactly matches the rate of respiration ( in terms of both O2, CO2 input + output)

31
Q

Similarities between chemiosmosis in a mitochondria to a chloroplast?

A
  • Both involve ATP synthase and both produce ATP
  • Both rely on pumping of H+ across internal cell membrane
  • Both rely on concentration gradient and electrochemical gradient of protons
  • Both require ADP and Pi as substrates.
32
Q

Differences between chemiosmosis in a mitochondria to a chloroplast?

A

Mitochondria

  • ATP produced in mitochondrial matrix, whereas ATP produced in stroma of chloroplast
  • ATP synthase is in inner membrane of mitochondrial envelope whereas it’s in thylakoid membrane of chloroplast
  • Occurs at end of aerobic respiration, whereas PHS for chloroplasts
  • Dependent on O2, whereas dependent on CO2 in chloroplast.
33
Q

Action spectra info?

A

Plots relative rate of photosynthesis against wavelength.

34
Q

Absorption spectra info?

A

Plots intensity of light energy absorbed against wavelength
Determined by spectrometer.
Show that the wavelengths that are most strongly absorbed are red and blue, so they cause photosynthesis to proceed at the fastest rate. Green isn’t strongly absorbed, it is reflected.

35
Q

Short wavelength light information?

A

The shorter the wavelength, the more energy it contains. During photosynthesis, the light energy is converted into chemical potential energy. The absorbed light excites electrons in the pigment molecules and the energy can be passed onto be used by the plant.

36
Q

At the compensation point info?

A

The uptake of CO2 through photosynthetic pathways is exactly matched to the respiratory release of CO2
AND
The uptake of O2 by respiration is exactly matched to the photosynthetic release of oxygen.

37
Q

When is compensation point best achieved?

A

During early mornings and late evenings
Respiration is relatively constant, whereas photosynthesis depends on intensity, wavelength and duration of sunlight.
The products of photosynthesis (glc) are used up in respiration so the plant is neither consuming nor building biomass

38
Q

How is carbon dioxide a limiting factor in photosynthesis?

A

CO2 is used in light independent reactions
Lack of CO2 -> reduced production of G3P -> reduction in TP -> reduced regeneration of RuBP.

CO2 levels can be increased by use of a paraffin heaters or burning methane.

39
Q

How is light a limiting factor in photosynthesis?

A

Light affects light dependent reactions
It causes:
- stomata to open
- Photolysis of water
- Excitation of electrons in chlorophyll molecules.
It affects photophosphorylation, so affects the quantity of ATP and reduced NADP produced for Calvin cycle.

WAVELENGTH - Aquatic plants/ plants grown underwater may not receive all wavelengths of light
INTENSITY - at VERY high light intensities, chlorophyll can be bleached -> decrease in PHS.
DURATION -> As duration Increases, rate of PHS increases.

40
Q

How is chlorophyll a limiting factor in photosynthesis?

A 
Rarely a limiting factor
A reduction of chlorophyll production may occur as a result of a lack of mineral ions such as:
- nitrates
- Phosphates
- Magnesium
41
Q

How is oxygen a limiting factor in photosynthesis?

A

High levels of oxygen increase the oxygenase activity of RuBisCO

42
Q

How is temperature a limiting factor in photosynthesis?

A
  • Temp MAINLY affects light independent reactions
  • it affects any enzyme controlled reaction
  • low temp - inactive
  • high temp - denature

If temp rises too high, it will increase water loss, so stomata will close as a result of plant being under stress, so a decrease in availability of carbon dioxide.

43
Q

Possible limiting factors of photosynthesis?

A 
Carbon dioxide
Light....
Temperature
Chlorophyll
Oxygen
44
Q

Determining the rate of photosynthesis?

A

Use a Photosynthometer to measure the effects of external conditions on rate of photosynthesis.

45
Q

How are the palisade mesophyll specialised to increase the efficiency of Photosynthesis?

A

PMC

  1. Closely packed to absorb maximum light
  2. Large vacuole pushes chloroplasts to edge of cell to absorb maximum light
  3. Chloroplasts at the edge have a short diffusion path for CO2
  4. Large number of chloroplasts to absorb maximum light
  5. Large Surface area for diffusion of gases.
  6. Moist surface area for diffusion of gases
  7. Thin cell walls for maximum light penetration/diffusion of gases.
46
Q

Evidence for the Calvin cycle information?

A

Radioactive carbon-14 is added in the form of hydrogen carbonate to a ‘lollipop’ apparatus containing green algae. (chlorella spp)
Light shone on apparatus
After different periods of time, algae is killed by running it in solution of methanol.
Dead algal samples are analysis using 2D chromatography, which separates out different carbons.
Any radioactive carbon compounds on chromatogram were identified using autoradiography.

By comparing different periods of light exposure, the order by which different carbon compounds are generated was determined.

47
Q

Info on the Lollipop apparatus

A

Light - Shone on apparatus to ensure algae are photosynthesising. Needed for photolysis of water and photoionisation of water -> carry out LDR.

Hydrogen carbonate acts as source of CO2 to prevent it becoming a limiting factor. It’s radioactive. Allows the carbon to be tracked.

Heat shields (water filled tanks) placed between lights and lollipop to prevent heat emitted from light bulb overheating chlorella suspension and killing algae by denaturing photosynthetic enzymes.

Methanol - immediately stops cell metabolism and respiration and other photosynthetic reactions.

48
Q

Engelmann’s Experiment info?

A

Engelmann exposed a filamentous algae, Spirogyra, to a colour spectrum produced by passing light through a prism.
He estimated the rate of photosynthesis indirectly by observing movement of aerobic bacteria towards portions of algal filament emitting the most oxygen.
The most bacteria aggregates along the cells in the blue-violet and red portions of the spectrum.
This shows the wavelengths of light absorbed by the different types of chlorophyll pigments.

49
Q

Info on RuBisCO

A

Optimum pH = 8
Quaternary (as prosthetic groups)
Globular
Can catalyse two different types of reactions: COOH, O

High turnover rate.

50
Q

What is the light saturation point?

A

The intensity at which additional increases in light do not increase photosynthesis

51
Q

Investigating the rate of the LDR?

A

Hill Reaction
DCPIP used. Is an artificial electron acceptor. (replaces NADP)
It does no harm when added to chloroplasts in a buffer solution.
changes colour from blue to colourless when reduced.

Chloroplasts isolated from green plant leaves and suspended in buffer solution of same concentration as cytosol.
Control - water and DCPIP, to prove decolorisation won’t occur without light.

Grind spinach with pestle and mortar, then spin in centrifuge at high speed. Pellet will form at base of centrifuge, so decant supernatant into cuvette.
Use red filter to absorb green light. Colorimeter will detect blue colour of oxidised DCPIP.
The splitting of water by light energy (photolysis) is source of hydrogen that turns DCPIP colourless.

2DCPIP + 2H20 –> 2DCPIPH2 + O2.

Gymnastics and tumbling (29 decks)

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