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respiration & photosynthesis > Photosynthesis > Flashcards

Photosynthesis Flashcards

1
Q

What is photosynthesis?

A

it is a way of making glucose from light energy, water and CO2
- light energy is converted into chemical energy in form of glucose

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2
Q

define metabolic pathway

A

a series of small reactions controlled by enzymes

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3
Q

define photophosphorylation

A

light energy used to add phosphate to a molecule

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4
Q

define photolysis

A

light energy used to split a water molecule into protons, electrons and 02

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5
Q

Which coenzymes are used?

A

NADP which transfers Hydrogen

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6
Q

What is the structure of chloroplasts?

A
  • they have a double membrane called chloroplast envelope
  • thylakoids are stacked into structures called grana
  • grana are linked together by parts of thylakoid membrane called lamellae
  • contain photosynthetic pigments
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7
Q

Name the photosynthetic pigments and what are they

A
  • coloured substances which absorbed light for photosynthesis
    chlorophyll a
    chlorophyll b
    carotene
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8
Q

Where are photosynthetic pigments found?

A

In the thylakoid membrane attached to proteins

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9
Q

What is a photosystem?

A

protein attached to photosynthetic pigment

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10
Q

What are the 2 types of photosynthetic pigments?

A

primary and accessory

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11
Q

What are primary photosynthetic pigments?

A
  • they are reaction centres

- electrons are excited during light dependent reaction

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12
Q

What are accessory photosynthetic pigments?

A
  • make up light harvesting systems
  • surround reaction centres
  • transfer light energy to them to increase energy available to make electrons excited
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13
Q

How many photosystems are there and what are they used for?

A

2 (I AND II)
they are used to capture light energy
PSI absorbs light best at wavelength of 700nm
PSII absorbs light best at wavelength of 680nm

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14
Q

Where are the stroma?

A
  • in the inner membrane of chloroplast
  • surround thylakoids is stroma
  • contains DNA, enzymes, organic acids and sugar
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15
Q

Where is the DNA?

A

in stroma
circular
multiple copies in each chloroplast

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16
Q

What else is stored in stroma?

A

carbohydrates that are produced but not used straight away are stored as starch grains in stroma

17
Q

What are the 2 stages of photosynthesis?

A
  • light-dependent reaction

- light-independent reaction

18
Q

Explain what happens in light dependent reaction?

A
  • occurs in thylakoids
  • requires light
  • absorbed by photosynthetic pigments in photosystems and it is converted into chemical energy
19
Q

What are the 2 types of phosphorylation in light dependent reaction?

A

non cyclic and cyclic

both have different products

20
Q

What do photosystems use the absorbed light energy for?

A
  • making ATP from ADP and P (photophosphorylation
  • making reduced NADP from NADP
  • Photolysis - splitting of H20 into electrons, protons and 02
21
Q

Explain what happens in noncyclic photophosphorylation

A
  • photosystems are linked by electron carriers
  • photosystems and electron carriers form electron transport chain
    stage 1
  • light energy is absorbed by PSII which is excites electrons in chlorophyll
  • electrons move to a high energy level so have more energy
  • high energy electrons move along transport chain to PSI
    stage 2
  • electrons need replacing as they leave PSII so photolysis occurs
    stage 3
  • excited electrons lose energy as they move along the chain
  • energy used to move protons across membrane into thylakoid via proton pumps
  • thylakoids have higher proton conc so form proton gradient
  • protons move down concentration gradient into stroma via ATP synthase
  • energy from movements combines ADP to P forming ATP
    stage 4
  • light energy absorbed by PSI which excites electrons to an even higher level
  • electrons transferred to NADP along with proton from stroma forming reduced NADP
22
Q

Explain cyclic photophosphorylation

A
  • only uses PSI
  • cyclic as electrons from chlorophyll aren’t passed to NADP but back to PSI via electron carriers
  • no reduced NADP or O2
  • produces small amounts of ATP
23
Q

Explain light independent reaction or calvin cycle

A
  • occurs in stoma
  • CO2 fixation is where C from CO2 is fixed into organic molecule
  • needs ATP and H ions to keep going
  • CO2 enters leaf via stomata and diffuses into stroma
  • combines RuBP (5C) forming 6C compound
  • unstable so quickly breaks into 2 molecules of GP (3C)
  • RuBisCo catalyses reaction between CO2 and RuBP
  • 2 ATP from dependent reaction provides energy to turn GP (3C) into TP (3C)
  • requires h ions from 2 reduced NADP from dependent reaction so NADP regenerated for next use
  • TP converted into useful organic compounds such as glucose
    cycle happens 6 times

respiration & photosynthesis (2 decks)

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