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Biology Hope > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

what is the importance of photosynthesis

A
  • for plants to make their own food to gain energy
  • energy for metabolic reactions
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2
Q

what is the equation of photosynthesis

A

Carbon Dioxide + Water = Glucose + oxygen

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3
Q

what is the need for energy

A
  • metabolic reactions
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4
Q

what is a metabolic pathway

A

series of small reactions controlled by enzymes

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5
Q

what is phosphorylation

A
  • adding a phosphate to a molecule
  • ADP is phosphorylase to ATP
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6
Q

what is photophosphorylation

A
  • using light to add a phosphate to a molecule
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7
Q

what is photolysis

A

splitting of a molecule using light energy

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8
Q

what is hydrolysis

A

splitting of a molecule using water

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9
Q

what is decarboxylation

A

removal of carbon dioxide

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10
Q

what is dehydrogenation

A

removal of hydrogn

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11
Q

what is chemiosmosis

A
  • diffusion of protons from high to low concentration
  • movement of protons down the gradient releases energy that is used in the attachment of and inorganic phosphate to ADP to create ATP
  • energy to do this comes from excited electrons
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12
Q

what are excited electrons

A
  • excited in pigment molecules when absorbing light energy
  • high energy electrons released when chemical bonds are broken in respiratory substrate molecules
  • excited electrons pass into electron transport chain and used to generate a proton gradient
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13
Q

what is the electron transport chain

A
  • made of electron carriers
  • electrons move down the gradient from one carrier to another and release energy
  • pumps protons across creating a concentration difference and a gradient
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14
Q

what is the structure of a chloroplast

A

Chloroplast envelope = double membrane

Thylakoids = stacked up into grana and linked by thylakoid membranes called lamellae

Photosynthetic pigments = coloured substances that absorb light energy, in thylakoid membranes attached to a protein

Stroma = fluid-filled membrane, contains starch grains, oil droplets, DNA + Ribosomes, light-independent stage

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15
Q

what are photosystems

A
  • contains primary and secondary pigments
  • photosystem 1 and 2
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16
Q

what is chlorophyll what colours do each pigment represent

A

Chlorophyll A = yellow/green (Primary)
Chlorophyll B = blue/green
Carotene = yellow/ orange
Xanthophyll = yellow

17
Q

what is the light dependent stage

A
  • needs light energy
  • in thylakoid membranes
  • energy absorbed by photosynthetic pigments and converted to chemical energy
18
Q

what are the 4 stages of non-cyclic phosphorylation

A
  • light energy excites electrons
  • photolysis of water
  • energy makes ATP
  • energy generates reduced NADP
19
Q

how does light energy excite electrons

A
  • light energy absorbed by PSII
  • light energy excites electrons in chlorophyll
  • electrons move to a higher energy level
  • high energy electron move along the electron transport chain to PSI
20
Q

what happens in the photolysis of water

A
  • as excited electrons leave PSII to move along the ECT they must be replaces
  • light energy splits water into protons, electrons and oxygen
21
Q

how does energy from excited electrons create ATP

A
  • excited electrons lose energy as they move along the ETC
  • energy used to transport protons into the thylakoid via proton pumps
  • thylakoid has a higher concentration of protons than the stroma
  • proton gradient formed across membrane
  • protons move down the concentration gradient into the stroma via ATP synthase
  • energy combined ADP and Pi to form ATP
22
Q

how does energy from the excited electrons generate reduced NADP

A
  • light energy absorbed by PSI
  • excites electrons to a even higher level
  • electrons are transferred to NADP with a proton (H+ ion) from the stroma
  • reduced NADP formed (NADPH)
23
Q

What is cyclic photophosphorylation

A
  • only uses PSI
  • electrons from the chlorophyll aren’t passed onto NADP
  • passed back to PSI via electron carriers
  • electrons are recycled and repeatedly flow through PSI
  • doesn’t produce NADPH or oxygen only small amounts of ATP
24
Q

what is the light independent reaction

A
  • calvin cycle
  • doesn’t use light energy directly
  • relies on the products from the light independent reaction
  • takes place in the stroma
25
Q

what is the first stage of the calvin cycle

A
  • carbon dioxide enters the leaf through the stomata and diffuses into the stroma
  • CO2 combined with RuBP (5 carbon compound)
  • unstable 6 carbon compounds which break down into 2 molecules of 3 carbon compounds called GP
  • RuBisCO catalyses the reaction between CO2 and RuBP
26
Q

what is the second stage of the Calvin cycle

A
  • ATP from light dependent reaction provides energy to turn 3GP to 3 TP
  • reaction requires H+ ions from reduced NADP in LDR
  • reduced NADP recycled to NADP
  • TP converted to several organic compounds
27
Q

what is the third stage of the Calvin cycle

A
  • 5 out of every 6 molecules of TP produced used to regenerate RuBP which used the rest of the ATP produced by LDR
28
Q

what organic substances are made from the Calvin cycle

A

Carbohydrates
- hexose sugars made by joining 2 TP molecules together

Lipids
- made using glycerol synthesised from TP and fatty which are synthesised from GP

Amino acids
- made from GP

29
Q

how many times does the calvin cycle need to turn to make a hexose sugar

A
  • three turns produce 6 TP molecules
  • 5/6 TP molecules are used to regenerate RuBP
  • three turns produces 1 TP to make a hexose so two TP molecules needed
  • 6 turns are needed
  • 6 turns need 18 ATP and 12 NADH from LDR
30
Q

What are limiting factors of photosynthesis

A
  • light
  • temperature
  • carbon dioxide
31
Q

how can light be a limiting factor

A

high light intensity = high energy to excite electrons
Very high light intensity = photosynthetic pigments are damaged
low = products of LDR are in short supply

  • conversion of GP to TP and RuBP is slow
  • level of GP rises and levels of TP and RuBP fall
32
Q

how can temperature be a limiting factor

A
  • too high (above 45)
  • too low (below 10)
  • denaturing of enzymes
  • all reactions in the Calvin cycle are catalysed by enzymes
  • levels of RuBP, TP, GP fall + denature
33
Q

how can carbon dioxide levels be a limiting factor

A
  • low concentrations conversion of RuBP to GP is slow
  • level of RuBP rises and GP and TP fall

Biology Hope (26 decks)

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