5.5 photosynthesis Flashcards
(67 cards)
1
Q
how is energy stored?
A
in glucose
2
Q
where do animals take glucose from?
A
eating plants or other animals
3
Q
where do plants take glucose from?
A
make it in photosynthesis
4
Q
whats the photosynthesis equation?
A
6(CO2) + 6(H2O) = C6H1206 + 6(O2)
5
Q
define respiration
A
cell releasing energy from glucose
6
Q
what are the 2 types of respiration
A
anaerobic
aerobic
7
Q
aerobic respiration equation
A
C6H12O6 + 6(O2) = 6(CO2) + 6(H2O)
8
Q
which are the coenzymes used in photosynthesis?
A
NADP -transfers oxygen from one molecule to another (reduce/oxidise molecule)
9
Q
coenzymes used in respiration
A
NAD/FAD -transfers hydrogen from one molecule to another (reduce/oxidise molecule)
coenzyme A - transfers acetate between molecules
10
Q
chloroplast
A
- flattened structure in plant cells
- Double membrane
- inside contains thylakoid membrane stacked up into structures called grana linked together by bits of thylakoids, lamellae
- contain photosynthetic pigments
- contain stroma
11
Q
which are the 3 photosynthetic pigments?
A
chlorophyll a
chlorophyll b
carotene
12
Q
what are photosynthetic pigments?
A
coloured substances that absorb light energy
13
Q
where are photosynthetic pigments found
A
chloroplast, thylakoids membrane attached to proteins
14
Q
proteins + pigments =
A
photosystem
15
Q
what does a photosystem contain?
A
2 types of photosynthetic pigments
- PRIMARY
- ACCESSORY
16
Q
what is the role of primary photosynthetic pigment?
A
is the reaction centre
where electrons are excited in the light dependent reaction
17
Q
what is the role of accessory photosynthetic pigment?
A
make up light-harvesting system, surrounds reaction centre and transfer light energy to them to excite electrons
18
Q
how many photosystem are used to capture light energy?
A
2
- PI absorbs best at wavelength 700nm
- PII absorbs best at wavelength 680nm
19
Q
what is stroma?
A
gel-like substances
20
Q
where is stroma found?
A
surrounding thylakoids
21
Q
what does stroma contain?
A
- enzymes
- sugars
- organic acids
- DNA (often circular), there can be multiple copies
- carbohydrates not used straight away (produced in photosynthesis) stored in starch grains
22
Q
how many stages does photosynthesis have?
A
2
- light dependent reaction
- light independent reaction
23
Q
where does LDR occur?
A
thylakoids membranes
24
Q
describe LDR
A
- light energy absorbed by photosynthetic pigments in photosystem
- converted into chemical energy
- energy used to:
1. add an inorganic phosphate to ADP –> ATP (phosphorylation)
2. reduce NADP to form reduced NADP
3. split water into protons, electrons and oxygen (photolysis) - H2O oxidises to O2
25
where does LIR occur?
stroma
26
describe LIR
- doesn't use light energy directly but relies on products
| - ADP & reduced NADP supply energy and hydrogen to make glucose from CO2
27
experiment - to separate photosynthetic pigments
thin layer chromatography
28
two phases of thin layer chromatography
- mobile phase (liquid solvent)
| - stationery phase (chromatography plate)
29
process of thin layer chromatography
1. grind leaves + anhydrous sodium sulfate + propanone = liquid
2. liquid + petroleum ether - test tube, shake - 2 layers, top one is pigments
3. top layer + anhydrous sodium sulfate - test tube
4. pencil line - bottom of chromatography plate, concentrates spot of liquid (several drops, dry) point of origin
5. plate in beaker with a solvent (line little above)
different pigments move at different rates, they will separate
6. when solvent nearly reached the top take out and mark solvent front and separated pigments (coloured spots)
7. calculate Rf values
30
Rf formule
distance travelled by spot / distance travelled by solvent
31
which are the two types of phosphorylation?
- non cyclic
| - cyclic
32
how are photosystems linked in non cyclic phosphorylation?
```
electron carriers (proteins)
form electron transpost chain
```
33
describe non cyclic phosphorylation
1. - light energy absorber by PSII
- electrons in chlorophyll are exited, move along electron transport chain
2. - electrons must be replaced
- light energy splits water into protons and oxygen
H2O -> 2H+ + 1\2O2
3. - excited electrons lose energy in electron transport chain
- is used to transport protons in thylakoids via membrane proteins (proton pump)
- higher concentration of protons in thylakoids
- protons move down into stroma via an enzyme ( ATP synthase)
- energy from this movement combines ADP and inorganic phosphate to form ATP
4. light energy absorbed by PSI, excites electrons at a even higher energy level
- electrons transferred to NADP with a proton from the stroma to form reduced NADP.
34
what are protons
h ions
35
describe cyclic phosphorylation
only uses PSI
| -electrons from chlorophyll are passed back to PSI via electron carries (recycled)
36
what does cyclic phosphorylation produce?
small amount of ATP
| -no O2 or NADP
37
how is light independent reaction also called
Calvin cycle
38
where does Calvin cycle take place
in stroma
39
what does Calvin cycle need
ATP and protons
40
describe Calvin cycle
1. co2 enters stoma through stomata
- is combined with ribulose bisphosphate (RuBP), a 5C compound
- this gives an unstable 6c compound
- quickly breaks down into 2 molecules of 3c compound, glycerate 3 phosphate (GP)
- ribulose bisphosphate carboxylase (RuBisCO) catalyses reaction between co2 & RuBP
2. ATP (from LDR) gives energy to turn GP into a different 3c compound, triose phosphate (TP)
- this requires also h ions from red NADP (from LDR) recycled to NADP
- TP converted into useful substances , 5 every 6 are used to regenerate RuBP, where the rest of ATP (from LDR) is used.
41
how many turns of Calvin cycle to form an hexose sugar?
| why?
6
| two triose phosphate are needed to form an expose. sugar
42
how many molecules of triose phosphate are produced in 3 turns of Calvin cycle?
6
43
how many molecules of triose phosphate are used to regenerate RuBP every 6 molecules
5
44
what do 6 turns of Calvin cycle need
18 ATP
12 reduced NADP
froml LDR
45
what are triose phosphate and glycerate 3 phosphate converted into?
1. carbohydrates- hexose sugers, join 2 TP e.g. glucose
- larger carbohydrates (starch, cellulose) join hexose sugars in different ways
2. lipids
- TP synthesises glycerol
- GP fatty acids
3. some amino acids made from GP
46
why is important to maintain an optimum temperature during photosynthesis?
enzymes are involved
under 10 *C inactive
above 40*C denature
47
what happens in photosynthesis if temperature is too high?
1. -stomata close to safe water
- less carbon dioxide enters
- photosynthesis slow
2. -thylakoid membrane can be damaged
- rate of LDR decreases because less sites are available for electron transfer
3. membrane around chloroplast damaged enzymes needed in Calvin cycle are released into the cell
- reduce rate of LIR
4. -chlorophyll damaged
- reduce amount of pigment that can absorb light energy
- rate of LDR slows
48
which are the limiting factors in photosynthesis
-light intensity (wavelength)
-co2
-temperature
(water)
49
how does wavelength affect photosynthesis?
- higher intensity of light provides more energy
- only certain wavelength are used in photosynthesis, photosynthetic pigments only absorbs red and blue light (green is reflected)
50
how does carbon dioxide affect photosynthesis?
- makes up 0.04% of gases in atmosphere
- increased to 0.4% : higher rate of photosynthesis
- any higher stomata close.
51
how do limiting factors of photosynthesis interact ?
all need to be at the optimum level to have quicker photosynthesis
-if one is too low it will be limited
52
whats usually the limiting factor in sunny windless places?
co2
53
whats the limiting factor of photosynthesis at night?
light intensity
54
define metabolic pathway
a series of small reactions controlled by enzymes e.g. respiration and photosynthesis
55
phosphorylation
adding a phosphate to a molecule
56
photophosphorylation
adding a phosphate to a molecule using light
57
photolysis
splitting of a molecule using light energy
58
hydrolisis
splitting of a molecule using water
59
decarboxylation
removal of carbon dioxide from a molecule
60
dehydrogenation
removal of hydrogen from a molecule
61
redox reactions
reaction that involve oxidation and reduction
62
reduction
gained an electron, may have gained hydrogen or lost oxygen
63
oxidation
lost an electron, may have lost hydrogen or gained oxygen
| oxidation of a molecule always involves reduction of another molecule
64
how does light intensity affect tp gp and rubp levels?
short supply of LDR products (ATP and red NADP)
conversion of GP into TP and RuBP is slow
GP levels rise
TP and RuBP levels fall
65
how does temperature affect TP GP RuBP?
All reaction in Calvin cycle are catalysed byenzymes
reactions are slower
levels of GP TP RuBP fall
66
how does carbon dioxide concentrations affect GP TP RuBP levels?
conversion of RuBP into GP slower
level of RuBP rise
level of GP and TP fall
67
investigating rate of photosynthesis using pondweed
1. pondweed + water in a test tube connected to a capillary tube connected to a syringe
2. source of white light placed at a set distance
3. let photosynthesise for a set amount of time , oxygen is collected in the capillary tube
4. syringe move oxygen up along side a ruler, length is measured
5. variables (time temp.) must be controlled
6. repeated, average
7. repeat at different distances
