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Biology - A, Y13 > Photosynthesis- A11 > Flashcards

Photosynthesis- A11 Flashcards

1
Q

Why is photosynthesis an example of a metabolic pathway?

A

It is a series of small reactions controlled by enzymes.

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2
Q

What is ATP made from?

A

The nitrogenous base adenine, combined with a ribose sugar and 3 phosphate groups.

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3
Q

How is ATP formed?

A

-ATP is synthesised from ADP and an inorganic phosphate group using a condensation reaction and energy
-the energy is stored in the phosphate bond
-done by ATP synthase
-this is an example of phosphorylation-adding phosphate to a molecule

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4
Q

What happens when ATPis hydrolysed?

A

-ATP is hydrolysed into ADP and Pi
-done by ATP hydrolase
-ADP and Pi are then recycled and ATP can be formed again.

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5
Q

What are the properties of ATP?

A

-stores and releases small, manageable amounts of energy at a time - none wasted as heat
-small and soluble so can be transported around the cell
-easily broken down so instantaneous energy source
-quickly remade
-can male other molecules more reactive by phosphorylating them
-cant pass out of the cell so cells always have an immediate energy source

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6
Q

What are chloroplasts?

A

-where photosynthesis takes place
-small, flattened organelles, double membrane
-thylakoids are stacked in the chloroplast into grana
-grana linked together by thylakoid membrane called lamellae

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7
Q

What are photosynthetic pigments?

A

-chloroplasts contain photosynthetic pigments e.g. chlorophyll a/b and carotene
-they are coloured substances that absorb the light
-found in the thylakoid membrane attached to proteins

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8
Q

What is a photosystem?

A

a pigment+ a protein

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9
Q

What does chromatography do?

A

separates and identifies substances in a mixture

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10
Q

What is the mobile phase in chromatography?

A

where molecules can move(usually a liquid solvent)

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11
Q

What is the stationary phase in chromatography?

A

where the molecules can’t move
-paper in paper chromatography, and silica gel in TLC.

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12
Q

Why is the start line drawn in pencil and not pen in chromatography?

A

as pencil is insoluble and would stay in the same position, whereas if they were drawn in pen, the leaf pigments and ink would mix and the origin line would be in a different position from the start.

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13
Q

Describe the process of chromatography.

A

1)start line/origin line drawn in pencil
2)add solution
3)put the stationary phase into the mobile phase so that the solvent is below the origin line
4)remove the stationary phase before the solvent reaches the top.

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14
Q

What happens to pigments in chromatography?

A

-plants have various pigments in their leaves
-different plants have these pigments in different proportions
-separate these out using paper/TLC chromatography and identify the pigments by calculating the RF values

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15
Q

What is the equation for RF values?

A

Rf value= distance travelled by spot/ distance travelled by solvent

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16
Q

What is a redox reaction and what happens in them?

A

-reaction that involves both oxidation and reduction
-oxidation is gain of oxygen/loss of hydrogen/loss of electrons
-reduction is loss of oxygen/gain of hydrogen/gain of electrons

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17
Q

What is a coenzyme and what does it do?

A

-a molecule that aids the function of an enzyme
-transfer a chemical group from one molecule to another

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18
Q

Which coenzyme is used in photosynthesis and what does it do?

A

-NADP is a coenzyme used in photosynthesis
-it transfers hydrogen from one molecule to another

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19
Q

What are the two stages of photosynthesis?

A

-the light dependent reaction(light is needed). Across the thylakoid membrane.
-light independent reaction(light not needed).Also known as the Calvin cycle.

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20
Q

In the LDR, what is the energy from photoionisation used for?

A

1)making ATP from ADP and Pi - photophosphorylation
2) making reduced NADP from NADP
3) splitting water into protons(H+ ions), electrons and oxygen - photolysis

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21
Q

What is non-cyclic phosphorylation?

A

-2 photosystems
-produces ATP, NADPH, and oxygen
-photosystems are linked by electron transfer chain
-photosystems and electron carriers form an electron transport chain

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22
Q

What are electron carriers?

A

proteins that transfer electrons

23
Q

What is an electron trasnfer chain?

A

a chain of proteins through which excited electrons flow.

24
Q

What is the first step in the LDR?

A

-light energy excites electrons to a higher energy level in chlorophyll
-light energy is absorbed by chlorophyll in photosystem 2(PS II) and excites electrons to a higher energy level.
-high energy electrons are released from chlorophyll and move down the electron transport chain(ETC) via redox reactions to photosystem 1(PS I).
-The chlorophyll has become a positive ion as it has lost an electron
-this process is called photoionisation.

25
What is the second step in the LDR?
-photolysis of water produces protons, electrons, and oxygen -light energy is used to split water into protons(H+), electrons and oxygen -the electrons produced are used to recharge the chlorophyll -2H20->4H+ + O2 + 4e-
26
What is the third step in the LDR?
-energy from the excited electrons is used to make ATP -excited electrons move down the ETC via a series of redox reactions and lose energy -this energy is used to actively transport H+ into the thylakoid through a carrier protein -there is now a higher concentration of H+ in the thylakoid -H+ diffuse via chemo osmosis back into the stroma via the enzyme ATPsynthase, producing ATP from ADP+Pi
27
What happens in photosystem 2?
1)light energy is absorbed by the chlorophyll in PS2 and an electron is excited to a higher energy level- photoionisation 2)electrons pass down the electron transfer chain 3)(electrons) reduce carriers/passage involves redox reactions 4)ETC/ role of chain associated with chloroplast membranes/in thylakoid/grana 5)energy released/carriers at decreasing energy levels 6)energy is used to pump H+ from stroma across the thylakoid membrane through a carrier protein 7)H+ diffuses through ATP synthase via chemiosmosis 8)ATP generated from ADP and Pi/ phosphorylation of ATp
28
What is the fourth step in the LDR?
-energy from the excited electrons generate reduced NADP -light energy is absorbed by PS1, which excited electrons again to an even higher energy level -electrons are transferred to NADP along with a proton from the stroma, forming reduced NADP -the reduced NADP(NADPH2) and ATP produced are used in the light independent reaction
29
What happens in photo system 1?
1)light energy excites/raises energy’s level of electrons in chlorophyll 2)electrons pass down electron transfer chain 3)electrons reduce carriers/passage involves redox reactions 4)ETC/role of chain associated with chloroplast membranes/in thylakoids/grana 5)2e- joins with 2H+ ions and NADP 6)to form NADPH2/ reduced NADP
30
What is chemiosmotic theory?
The flow of electrons down the EtC and creating a proton gradient across the membrane to drive ATPsynthesis is called chemiosmosis
31
What is cyclical phosphorylation?
-produces ATP using only PS1 -called cyclic because the electrons from the chlorophyll molecule are passed back to the chlorophyll by electron carriers not onto NADP -electrons are recycled and repeatedly used in PS1 -no reduced NADP or oxygen produced, just small amounts of ATP
32
What is the Light independent reaction also known as?
The Calvin cycle
33
Where does the Calvin cycle occur?
Stroma(in chloroplasts)
34
What from the LDR is used in the LIR?
ATP and NADPH from the LDR
35
What are common mark points for the LIR?
1)carbon combines with ribulose bisphosphate(RuBP) 2)to produce two molecules of glycerate-3-phosphate(GP) 3)reduced to triode phosphate(TP) 4)requires reduced NADP 5)and energy from ATP
36
Explain the Calvin Cycle.
-RuBP combines with CO2 using the enzyme rubisco to make 2 GPs -each GP is reduced into a triose phosphate using the H+ from a reduced NADP and the energy from an ATP -1 carbon from the 2 triose phosphates are used to make glucose. The remaining 5 carbons are regenerated into RuBP using ATP.
37
How are heroes sugars created?
-1 hexose sugar is made from joining two molecules of TP
38
How many times must the Calvin cycle to create one hexose sugar?
-Calvin cycle must turn 6 times to make 1 hexose sugar -3turns makes 6 TPs -5 of these 6 are used to regenerate RuBP -so 3 turns makes only 1 TP that can be used to make a hexose sugar
39
What are some uses for hexose sugars?
-carbohydrates - hexose sugars made from 2 TPs, e.g. glucose. Larger carbohydrates are also made e.g. sucrose, cellulose, and starch, by joining hexose sugars together in different ways. -lipids - made using glycerol, which is synthesised from TP and fatty acids which are synthesised from GP -amino acids - some are made from GP
40
What are the optimum conditions for photosynthesis?
1) high light intensity of a certain wavelength 2)temperature around 25oC 3)carbon dioxide around 0.4% 4)water
41
What are the benefits of high light intensity of a certain wavelength
-light provides energy for the LDR - higher light intensity=more energy -only certain wavelengths are used - chlorophyll a/b, and carotene only absorb red and blue light
42
What is the benefits of temperature around 25oC in photosynthesis?
-enzymes are involved(ATPsynthase and rubisco) -below 10oC, enzymes become inactive as less kinetic energy.... -above 45oC, denaturation occurs -at high temps stomata close to avoid losing too much water so photosynthesis slows down because less CO2 enters the leaf when stomata are closed.
43
What is the benefit to photosynthesis when carbon dioxide is around 0.4%?
-CO2 is 0.04% of gases in the atmosphere -increasing to 0.4% increases the rate of reaction, any higher, the stomata start to close
44
Why is water a transpiration factor in photosynthesis?
-too little water - photosynthesis will stop - needed for photolysis in LDR -too much and the soil becomes waterlogged(reducing uptake of minerals such as Mg which is needed to make chlorophyll a)
45
true or false: if one of the limiting factors are too low or too high, it will limit photosynthesis
true -light, temp and CO2 can limit photosynthesis -e.g. at night light is the limiting factor - increasing the conc. of CO2 will not increase the rate of photosynthesis
46
What are some methods for increasing plant growth?
-farmers create environments in glasshouses where plants have everything they need(factors limit as little as possible) -CO2 conc. - CO2 us added to the air by burning a fuel -light - light shines through the glass and lamps provide light at night time -temperature - glasshouses trap heat energy from the sun which arms the air -heating and cooling systems keep the temp. at optimum -air circulation ensures temperature is even throughout the glasshouse
47
How do we measure rate of photosynthesis?
The rate of photosynthesis can be found by measuring the volume of oxygen produced per unit of time by using the apparatus called a photosynthometer
48
Why does the apparatus in the measuring photosynthesis practical need to be air tight?
Because any air escaping from or entering the apparatus will respectively decrease or increase the volume of gas measured, which will give and unreliable result
49
Why does the temperature of the water bath in the practical need to be kept constant?
Any changes in the rate of photosynthesis can be said to be the result of changes in light intensity and not changes in temperature
50
What is an advantage of providing an additional source of carbon dioxide in the practical?
To ensure there is sufficient CO2 and so that is does not limit the rate of photosynthesis
51
What is a reason for carrying out the experiment in a room that is dark except for the light source in the practical?
To prevent other light falling on the plant as this may fluctuate and will affect the light intensity and hence the rate of photosynthesis, leading to an unreliable result
52
Suggest why the plant is kept in the dark before the practical begins?
To prevent photosynthesis and allow any oxygen produced before the experiment begins, to disperse
53
Suggest a reason why measuring the volume of oxygen produced by the plant in this experiment may not be an accurate measure of photosynthesis in the practical?
Because the volume of oxygen produced will be less than that produced by photosynthesis as some of the oxygen will be used up in cellular respiration/dissolved oxygen(and other gases) may be released from, or absorbed by the water
54
Practical

Biology - A, Y13 (6 decks)

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