5.6 Photosynthesis Flashcards
(118 cards)
1
Q
What is autotrophic nutrition?
A
Process where chemical energy, from simple inorganic molecules such as water and carbon dioxide, synethsise large organic molecules that forms the biulding blocks of living cells.
2
Q
What are organisms that photosynthesise called?
A
Photoautotrophs.
3
Q
What are organsims that photosynthesise called photoautotrophs?
A
Because they use light energy as the source for autotrophic nutrition.
4
Q
What are photoautrotrophs also known as?
A
Producers- as they’re at the beginning (first trophic level) of the food chain and provide energy and organic molecules to other non-photoautotrophic, organisms.
5
Q
What is the general equation for photosynthesis?
A
6CO2 + 6H2O + light energy from photons -> C6H12O6 + 6O2
6
Q
What is the main products of photosynthesis?
A
A monosaccharide sugar (glucose) that can be turned into disaccharides for transport and then to storage.
7
Q
What process of photosynthesis an example of?
A
Carbon fixation- the process by which carbon dioxide is converted into sugars.
8
Q
What sort of reaction is carbon fixation?
A
Endothermic reaction, so it needs energy.
9
Q
What does carbon fixation help regulate?
A
The concentration of carbon dioxide in the atmosphere and oceans.
10
Q
Summarise what happens in plant respiration.
A
During respiration, the oxidise organic molecules that have previously sythesised by photosynethsis and stored, releasing chemical energy.
11
Q
What is a heterotroph?
A
Organism that obtains energy by digesting complex organic molecules of food or smaller molecules that they can use as respiratory substances. e.g. fungi, animals, many protoctists and many bacteria.
12
Q
Summarise what happens in respiration.
A
Gkucose and other organic compounds are oxidised to produce carbon dioxide and water- it releases chemical energy (exothermic) that can drive an organisms metabolism.
13
Q
What is the general equation for respiration?
A
C6H12O6 +6O2 -> 6CO2 + energy
14
Q
What is photosynthesis and aerobic respiration important for?
A
Cycling carbon dioxide and oxygen in the atmosphere.
15
Q
When do plants respire?
A
All the time
16
Q
When do plants photosynthesise?
A
During the daylight.
17
Q
Why do plants compete for light.
A
The intensity of the light must be sufficient to allow photosynthesis at a rate that replenishes the carbohydrate stores used up by respiration.
18
Q
What is the compensation point?
A
When photosynthesis and respiration proseed at the same rate so there is not net gain of carbohydrate.
19
Q
What is it called when photosynthesis and respiration proseed at the same rate?
A
Compensation point.
20
Q
At what point/s on the graph are the compenation point for a plant?
A
21
Q
What is the time taken for a plant by a plant to reach it compentation point called?
A
Commpenation period- this is different for every species of plant.
22
Q
What is the compenstation period like of shade plants compared to that of sun plants?
A
Shade plants can utalise light of lower intensity than sun plants can. When exposed to light after being in the darkness, shade plants reach their compensation point sooner, therefore, have a smaller compensation period.
23
Q
What is a granum?
A
An inner part of a chloroplast made of stacks of thylakoid membranes, where the light-dependent stange of photosynethesis takes place.
24
Q
What is photosynthetic pigment?
A
Pigment that absorbs specific wavelengths of light and traps the energy associated with the light; such as pigments include chlorophyll a and b , during the light-dependant stage of photosynthesis.
25
What is a photosystem?
**System of photosynthetic pigments found in thlakoids or cholorplasts** ; eah photosystem contains about 300 molecules of chlorophyll that trap photons and pass their energy to a primary pigment reaction centre , a molecule of chlorophyll a, during he light-dependant stage of pjotosynthesis.
26
What is a stroma?
A fluid filled matrix of chloroplasts, where the light-independant stage of photosynthesis takes place.
27
What is a thlakoid?
Flattened membrane-bound sac found inside chlorplasts; contains photosynthetic pigments/ photosystems and is the site of the light-dependant stage of photosynthesis.
28
What contains chlorplasts?
Plant cells
29
What are the 2 distinct reigions visable on an electron micograph of a chloroplast?
* The stroma- fluid filled matrix
* The grana- consists of thylakoid membranes.
30
What does the structure of a chloroplast look like?
31
What are the 3 different membranes a chloroplast has?
* Outer menbrane
* Inner membrane
* Thylakoid membrane
32
What is signficant about a chloroplast having 3 different membranes?
Creates 3 seperate internal compartments- the intermembrane space, stroma, and the thylakoid space.
33
What are the thylakoids within granum connected to other thylakoids by?
Intergranual lamellae.
34
What are interganual lamelle also known as?
Intergranual thylakoids.
35
What is the structure of the thylakoid membrane?
The thylakoid membrane of eaach chloroplast is less permeable and is folded into flattened disk-like sacs called thylakoids that forms stacks. Each stack is called a granum. One granum may contain up to 100 thylakoids.
36
Why is it significant that there are many grana in every chloroplast and with many chlorplasts in each photosythetic cell?
This provides a large surface area for:
* The **distribution of the photosystems** that contain the photosythetic pigments that trap sunlight energy.
* The **electron carriers and ATP synthase enzymes** needed to convert light energy to ATP.
37
What do proteins embeded in the thylakoid membranes do?
They hold the photosystems in place.
38
What is the grana surrounded by?
The stroma
39
Why is it important that the grana is surrounded by the stroma?
So the products of the light-dependant stage can easily pass into the stroma to be used in the light-independant phase.
40
What does the stroma contain?
* Enzymes needed to catalyse the reactions of the light independant stage of photosynthesis.
* Starch grains
* Oil droplets
* Small ribosomes
* DNA
41
What does the loop of DNA code for in the stroma?
Codes for proteins needed for photosynthesis- these proteins are assembled at the chloroplasts ribosomes.
42
What are the funnel-shaped structues within thylakoid membranes called?
Photosystems.
43
What do photosystems contain?
photosythetic pigments.
44
What does photosynthetic pigments in photosystems do?
Each pigment **absorbs light of a particular wavelength and reflects other wavelengths of light**- each pigment appears to pour eyes, the colour of the light it is reflecting.
45
What happens the wavelengths of light captured by the photosynthetic pigments?
The wavelength of light captured is funnelled down to the primary pigment reaction centre, consisting of chlorophyll, at the base of the photosystem?
46
What are the 2 types of chlorophyll?
* Chlorophyll a
* Chlorophyll b
47
Wgere ccan you find both types of chlorophyll a?
Botth are situated at the centre of photostems.
48
Describe chlorophyll a.
Theres 2 types oof chlorophyll a:
* P680 found in photostem II and it's peak absorbtion of light is wavelength 680nm.
* P700 found in photostem I and it's peak absorption is loght of wavelength 700nm.
49
When chlorophyll is found in photostem II and what is it's peak wavelength it will absorb?
P680 and has peak absorbtion of wavelength 680nm.
50
When chlorophyll is found in photostem I and what is it's peak wavelength it will absorb?
P700 and it's peak wavelength it will absorb is 700nm.
51
Chlorophyll a will also absorb some blue light, what is it's wavelength?
440nm
52
What colour does chlorphyll a appear?
Green
53
What colour does chlorophyll b appear?
yellow green
54
What wavelengths of light does chlorophyll b absorb?
Wavelengths 400-500nm and arounf 640nm.
55
Where are accessory pigments found?
In the walls of photostems.
56
What are some examples of accessory pigmeant?
* Carotoinds
* Xanthophylls
57
What wavelengths do cartenoids absorb and reflect in photostems?
They absorb blue light of wavelengths 400-500nm. They reflect yellow and orange light.
58
What wavelengths does xanthophyll absorb and reflect in photostems?
Absorb blue and green light with wavelengrths 375-550nm. They reflect yellow light.
59
Name 5 photosynthetic pigments.
* Carotene
* Phaeophytin
* Chlorophyll a
* Chlorphyll b
* Xanthophyll
60
Why is the Rf value of some photosynthetic pigments show a range rather than being a single figure?
There are different types of these, with slightly different molecular masses/sizes of molecules/solubilities in the
solvent.
61
How does the structure of chloroplasts enable them to carry out their functions?
* Many grana consisting of many thylakoid membranes gives large surface area for pigments
* electron carriers and ATP synthase enzymes for light-dependent stage.
* Stroma has enzymes for light-independent stage.
* Stroma close to grana so products of first stage can pass to stroma for second stage.
* Oil droplets in stroma as source of lipids
to make membranes.
* Ribosomes for protein synthesis of enzymes/electron carriers/anchoring proteins.
* DNA –genes coding for some chloroplast proteins.
62
Whats the Rf value of carotene?
0.91
63
What is the Rf value of phaephytin?
0.63-0.75
64
What is the Rf value of chlorophyll a?
0.63
65
What is the Rf value of chlorophyll b?
0.58
66
What is the Rf value of xanthophyll?
0.32-0.53
67
How do you work out the Rf value of a substance?
Rf value= x/y
(distance travelled by pigment/ distance travelled by the solvent)
68
Where does the light-dependant stange of photosynthesis occur?
In the grana (thylakoids) of chloroplasts and involves photosystems.
69
What does the light-dependant stage of photosynthesis consist of?
1. Light harvesting at the photosystems.
2. Photolysis of water.
3. Photophosphorylation- the production of ATP in the presence of light.
4. The formation of reduced NADP.
70
What by-product of photosynthesis is also produced in the lighht-dependant stange of photosynthesis.
71
What are the 2 types of photosystems?
* Photosystem I
* Photosystem II
72
Describe photosystem I.
The pigment at the primary reaction centre is a type of chlorphyll a, which has a peak absorbtion of red light of wavelength 700nm.
73
Describe photosystem II.
The pigment at the primary reaction centre is also a type of chlorophyll a, but this has a peak absorbtion of red light of wavelength 680nm.
74
What are electron carriers?
Molecules that accept one or more electrons and then donate tgose electrons to another carrier. Proteins embeded in thylakoid membranes are electron carriers, and form an electron transoport chain or system. Ferredoxin NAD and NADP are also electron carriers.
75
What is NADP?
Nictinamide adenine dinucleotide phosphate- a coenzyme and electron and hydrogen carrier.
76
What is photophosphorylation?
The generation of ATP and ADP and inorganic phosphate, in the presence of light.
77
What is another name for hydrogen ions?
Protons.
78
What is photolysis?
Splitting water in PSII, in the presence of light, inyo protons (hydrogen ions), electrons and oxygen.
79
What is the equation for photolysis?
2H2O-->4H+ + 4e- +O2
80
What is the oxygen produced in photolysis used for?
Some is used for respiration in the plant, but in periods of high light intensity the rate of photosynthesis is greater than the rate of respiratiom in the plant, so much of the oxygen by-product will diffuse out of the leaves, through the stoma, into the surrounding atomsphere.
81
What is the role of water in the light dependant stage of photosynthesis?
* It is the source of protons (hydrogen ions) that will be used in photophosphorylation.
* Donates elecrtons to chlorophyll to replace those lost when light strikes chlorophyll.
* Is the source of the by-product oxygen.
* Kepps plant cells turgid, enabling them to function.
82
What are the 2 types of photophosphorylation?
* Non-cyclic photophosphorylation
* Cyclic photophosphorylation
83
What is non-cyclic photophosphorylation?
It involves PSI ans PSII. It poduces ATP, oxygen and reduced NADP.
84
What is cyclic photophosphorylation?
Involoves PSI. It produces ATP (less than non-cyclic photophosphorylation).
85
What does both non-cyclic photophosphorylation and cyclic photophosphorylation have in common?
They both involove iron-containing proteins embedded in the thylakoid membranes that accept and donate electrons and form an electron transport system.
86
At the beginning of non-cyclic photophosphorylation, what happens when a photopn of light strike PSII?
The photons energy is channelled to the primary pigement reaction centre.
87
In non-cyclic photophosphorylation What does the light energy do after being channelled to the reaction centre?
The light energy excites a pair of electrons inside the chlorophyll molecule.
88
In non-cyclic photophosphorylation what happens to the pair of energied elecrons?
The energies electrons escape from the chlorophyll mooecule and are **captured by an electron carrier** , which is a protein with iron at it's centre, embeded in the thylakoid membrane.
89
In non-cyclic photophosphorylation what happens to the electrons captired by the electron carriers in the thylakoid membranes?
These elctrons are replaces by electrons derrived from photolysis.
90
In non-cyclic photophosphorylation what happens to an electron in the centre of an elecrton carrier?
The electron will combine with the iron ion becomine reduced (Fe^2+). It can then donate the electron, becoming reoxidised (Fe^3+), to the next electron carrier in the chain.
91
In non-cyclic photophosphorylation what occurs as electrons are passed al9ng a chain of elecron carriers embeded in the thylakoid membrane?
At each step some energy associated with the electrons is released.
92
In non-cyclic photophosphorylation what is the energy produced by the electron transport chain used for?
The energy is used to pump protons across the thylkoid membrane into the thylakoid space.
93
What eventually happens to the electrons after PSII in non-cyclic photophosphorylation?
Eventully the elecrtons are captured by another molecule of chlorophyll a is PSI. These electrons replace those lost from PSI due to excitation by light energy.
94
In photophosphorylation what happens when the electrons are initially captured by PSI?
The protein-iron-sulfur complex called **ferredoxin** accepts the elctrons from PSI abd passes them to NADP in the stroma.
95
In non-cyclic photophosphorylation what happens when protons accumulate in the thylakoid space?
A proton accumulate in the thylkoid space, a proton gradient forms across the membrane.
96
In non-cyclic photophosphorylation What happens when the protons gradient is formed?
Protons diffuse down their concentration gradient through special channels in the membrane associated with ATP synthase enzymes and, as they do so, the flow of protons cause ADP and inorganic phosphate to join, forming ATP.
97
In non-cyclic photophosphorylation what happens when the protons diffuse out though ATP synthase enzymes?
As protons pass through the chaannel they are accepted, alongz with electrons by NADP which become reduced. THe reduction of NADP is catalysed by the enzyme NADP reductase.
98
Summarise what happens in ono-cyclic photophosphorylation?
The light energy has been converted into chemical energy in the form ATP by photophosphorylation. ATP and reduced NADP are now in the stroma rady for the ligh dependant stange of photosynthesis.
99
Which PS does cyclic photophosphorylation occur at?
PSI (P700)
100
What is the process of cycic photophosphorylation?
As light strikes PSI, a pair of electrons in the chlorophyll molecule at the reaction centre gain energy and become excited. They escape from the chlorophyll and pass to an electron carrier system, then back to PSI.
101
What is produced in cyclic photophosphorylation?
**During the passage of electrons along the electron carriers, a small amount of ATP is generated. **
No photolysis of water occurs, so no protons or oxygen are produced. No reduced NADP is produced.
102
Which cells only only contain PSI in a plant? Why is this?
Chloroplasts in guard cells only contain PSI. They produce ATP ehich actively brings potassium ions into the cells, lowering the water potential so that water flows by osmosis- causing the gaurd cells to swell and open the stomata.
103
What is the Calvin cycle?
**Metabolic pathway of the light-independant stage of photosynthesis**, occuring. (in eukaryotic cells) in the stroma of chloroplasts where **carbon dioxide is fixed, with the products of the light-dependant stage, to make organic compounds.** The calvin cycle also occurs in many photoautrotrophic bacteria.
104
What is glycerate-3-phosphate (GP)?
An intermediate compound in the calvin cycle.
105
What is ribulose bisphosphate (RuBP)?
A 5-carbon compound present in chloroplasts; a carbon dioxide acceptor.
106
What is triose photophate (TP)?
A three-carbon compound, and the product of the calvin cycle; can be used to make other larger organic molecules.
107
Where does the light-independant stage of photosynthesis occur?
The stroma.
108
Whst does the light independant stage of photosynthesis need to occur?
It needs the products of the light dependant stage to occur.
109
What will happen to the light independant stage of phtotsynthesis if the plant is not illuminated?
The light independant stage will soon cease beacuse it depends on the products of the light dependant stage.
110
What is the role of carbon dioxide in caarbon-based life forms?
Carbon dioxide is the course of carbon for all organic molecules found in carbon based forms. e.g. cell membranes, antigens, enzymes ect.
111
How does carbon dioxide enter a leaf?
Carbon dioxide diffuses through the stomata and then diffuses throught the spongy mesophyll layer and palisade layer, into the palisade cell, through their thin cellulose walls and then through the chloroplast and into the stroma.
112
In what reaction in a plant is carbon converted into organic molecules?
The Calvin Cycle.
113
Whats the first step of the calvin cycle?
Co2 combines with a carbon dioxide acceptor, a 5 carbon compound called ribulose bisphosphate (RuBP). This reaction is catalysed by the enzyme RuBiCO (ribulose bisphosphate carboxylase oxygenase)
114
What enzyme catalyses Co2 combinind with the CO2 acceptor, ribulose bisphosphate?
Ribulose bisphosphate carboxylase-oxygenase
115
What is the carbon dioxide acceptor called in the first step of the carbon cycle?
Ribulose bisphosphate
116
What happens in the calvin cycle after Co2 combines with ribulose bisphosphate?
RuBP becomes carboxylated by accepting The COO- group, forming an unstable imtermidete six carbon compound that immediatly breaks down.
117
When RuBP breaks down in the calvin cycle, what is the product?
The product of this is 2 molecules of a 3-carbon compound, GP (glycerate-3-phosphate). **The acrbon dioxide has now been fixed**.
118
After carbon dioxide has been fixed in the calvin cycle by GP?
GP is now reduced, using hydrogens from NADP made during the light dependant stage, to **triose phosphate (TP).** Energy from ATP, also made during the light-dependant stage at the rate of 2 molecules of ATP for every molecule of ATP for every molecule of carbon dioxide.
