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Biology, Module 5 OCR > 5.2.1 Photosynthesis > Flashcards

5.2.1 Photosynthesis Flashcards

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1
Q

Name the parts (8) and function of the chloroplast

A
  • Organelle responsible for the biological process of photosynthesis. Contains specialised pigments that absorb light.
  • Stroma
  • Ribosome
  • Thylakoids : Granum
  • Intergranal lamellae
  • chloroplast membrane
  • starch grains
  • lipid droplets
  • Free DNA
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2
Q

Stroma (3)

A
  • Matrix in chloroplast that supports the Granum
  • contains enzymes that catalyse light dependant reactions
  • Light independent reactions occur here
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3
Q

Thylakoids (2)

A
  • Discs that stack up to form Granum, which increases surface area for more absorption of light
  • Contains the photosystem where chlorophyll and accessory pigments are located to absorb different wavelengths of light
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4
Q

Ribosomes in Chloroplast

A
  • Translates proteins from its DNA

- usually enzymes to help catalyse reactions like ATP synthase

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5
Q

Accessory pigments (4)

A
  • Located in the thylakoids.
  • Specialised pigments that absorb light at different wavelengths
  • includes: Carotenoids and chlorophyll
  • transfers energy to primary pigments
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6
Q

Carotenoids (3)

A
  • Light harvesting complex that absorbs the wavelength of blue light (450-470nm)
  • Reflects yellow/ Orange light making its pigment yellow/ orange
  • Includes: Xanthophyll and Carotene
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7
Q

Chlorophyll a

A

An accessory pigment that absorb light wavelength at 680-700 nm

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8
Q

Chlorophyll b

A

Photosynthetic pigment that absorbs light at 500-640 nm

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9
Q

Light dependant stage of photosynthesis

A
  • The initial stage that requires photons from light to excite electrons in water
  • photolysis of water occurs which releases electrons and oxygen (waste product)
  • In this stage ATP, Oxygen and H+ ions are created.
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10
Q

Light independent stage of photosynthesis

A
  • Does not involve photons from light but still occurs in light
  • Occurs in the stroma to produce sugar
  • CO2 is used to form carbon sugars
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11
Q

P680

A
  • Photosytem 2 which is the reaction centre chlorophyll
  • Mainly absorbs light at 680 nm
  • Involved in the first stage of photosynthesis
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12
Q

P700

A
  • Photosystem 1

- group of pigments responsible for absorbing wave length of light at 700 nm which is red light

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13
Q

Non cyclic photosphorylation (7)

A
  • Part of the light dependant stage in photosynthesis where ATP and NADPH is produced
  1. Photolysis of water: H2O is broken up by photons into
    - 2 electrons
    - 2 H+
    - 1/2 O2
  2. The electrons from the photolysis of water is drawn into the electron deficient P680, therefore P680 is reduced.
  3. Photons hit P680 and excites the electrons by increasing its energy levels (Photoexcitation)
  4. The electrons are released which oxidises PSII. The electrons are then captured by electron acceptor and passed along electron transfer chain (ETC)
  5. Energy is released in the transfer chain which is used to create ATP by combining ADP and Phosphate
  6. Steps 2-5 happen again but with P700
  7. H+ from the photolysis of water reduces NADP+ to NADPH using the energy from the ETC
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14
Q

Cyclic photosphorylation (3)

A
  • Occurs in the light dependant stage in photosystem 1
  1. Photons from light excites electrons in P700 and raises them to a higher energy level.
    (When electrons leave P700 it is oxidised so it draws electrons from the previous ETC to continue process.)
  2. Electrons released from P700 is brought back to the first ETC to generate ATP
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15
Q

What process forms ATP from ADP and Phosphate?

A

Condensation reaction

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16
Q

Primary pigments

A
  • Acts as reaction centres where electrons are excited

- chlorophyll a: P680 and P700

17
Q

What is a limiting factor and what are the 3 main limiting factors for photosynthesis?

A

A component that reduces the inihbits the rate of a process due to it being insufficient.

Temperature

Light intensity

CO2 concentration

18
Q

Describe the Calvin cycle.

A

Light-independent stage that occurs in the stroma:

Carbon fixation:

  1. RuBP(5C) is fixed by CO2 using catalysed by the RuBisCo enzyme. This forms an unstable 6 carbon intermediate.

Reduction:

  1. The unstable 6 carbon intermediate splits into two—> Each a 3C chain: Glycerate-3-Phosphate (GP).
  2. GP is further reduced, using NADPH and converted into Triose phosphate using energy from ATP.
    Both NADPH and ATP were generated from the light dependant stage.

Regeneration:

  1. TP is used as the starting point of many organic molecules: lipids, amino acids, glucose.
    The majority of TP is used to regenerate RuBP.

6 CO2 molecules are needed to form one molecule of glucose.
Every 6 cycles, 10 TP molecules are regenerated to from RuBP.

19
Q

Photorespiration.

A

Oxygen is a competitive inhibitor of RuBisCo.

When the concentration of carbon dioxide is low and oxygen rises, this prevents GP from being produced.

Oxygen forms phosphoglycolate. This is a toxic molecule that requires ATP to break down

20
Q

How can triglycerides be used as a respiratory substrate.

A

Lipids are hydrolysed into fatty acids and glycerol.

Glycerol is converted into pyruvate molecules and under goes the link reaction —> Acetate —> Kreb’s cycle.

Fatty acids can be reduced to acetate, then combines with CoA to form acetyl CoA.

Lipids provide more energy than carbohydrates.

21
Q

Respiratory substrate

A

An organic molecule that is broken down to release energy in the form of ATP.

22
Q

Describe how proteins can be used as a respiratory substrate.

A

Proteins are hydrolysed into amino acids and deaminated.

They are then converted to pyruvate molecules and enter the link reaction.

23
Q

Similarities between oxidative phosphorylation and photophosphorylation. (4)

A
  • Both use the movement of protons across the membrane.
  • Both use the flow of electrons in the ETC.
  • Both processes synthesise ATP and use ATPase to do so.
  • Both use a series of electron carriers- for example cytochrome.
24
Q

Differences between oxidative phosphorylation (OP) and photophosphorylation (PP). (4)

A
  • OP takes place in the mitochondrial cristae, PP takes place in thylakoid membranes.
  • OP requires chemical energy, PP requires light energy (photons).
  • In OP oxygen is the final electron acceptor.
  • PP can be cyclic.
25
Q

What factors can affect the growth of bacteria.

A

Nutrient available

Oxygen concentration

Temperature

Change in pH

Build of waste.

26
Q

What is role of ATP in the calvin cycle.

A

ATP supplies energy to transform GP to TP, by being hydrolysed.

Release of Phosphate from the hydrolysis of ATP is also used in phosphorylation to form RuBP.

Biology, Module 5 OCR (7 decks)

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