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Biology A2 > 3.2 - Photosynthesis > Flashcards

3.2 - Photosynthesis Flashcards

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1
Q

Formula?

A

Carbon dioxide + water — glucose + oxygen

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2
Q

What is photosynthesis divided into?

A

Light dependent + Light independent reaction

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3
Q

Light Dependent stage?

A

converts light energy to chemical energy
Photolysis of water releases electrons
Photolysis of water releases electrons + protons which creates a photo gradient on the thylakoid membrane
energy is needed to phosphorylate ADP to generate ATP whilst protons electrons reduce NADP

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4
Q

What happens in the light independent stage?

A

ATP and NADPH2 reduce CO2 and produce glucose

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5
Q

Label a Mitochondria

A

Granum - where light dependent reactions take place
Intergranal Thylakoid
Thylakoid
Starch Grain
Stroma ( fluid filled light independent stage)
Stained with osmium tetroxide binds to lipids not carbohydrates
appear white under microscope

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6
Q

Photosynthetic Pigments?

A

Chlorophyll a
Chlorophyll B
xanthophyll
carotene

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7
Q

Structure of a leaf?

A

Cuticle
Upper epidermis
Waxy - suberin
Transparent
Palisade layer
Spongy Mesophyll
Co2
H2o
stomata
stoma
guard cells

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8
Q

Large surface area?

A

captures as much light possible

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9
Q

Thin?

A

light penetrates through the leaf surface

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10
Q

Has stomatal pores?

A

allows CO2 to diffuse into the leaf

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11
Q

Air spaces?

A

allows CO2 to diffuse into the palisade layer

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12
Q

Cuticle + epidermis = transparent?

A

light to penetrate the mesophyll

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13
Q

Palisade cells have a large vacuole?

A

so chloroplasts form a single layer around the periphery
( this prevents them shading each other )

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14
Q

Palisade cells?

A

Cylindrical as this gives them a larger surface area
chloroplasts move within the palisade cell, maximum light absorption of light

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15
Q

How many times is the amount of chloroplast from a palisade cells in comparison to mesophyll?

A

5

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16
Q

What does a transducer do?

A

changes one form of energy to another
Biological transducers = more efficient than electrical devices + waste less energy

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17
Q

Chloroplasts?

A

transducers, turning energy in the photons of light into chemical energy which is made available through ATP and trapped in glucose molecules

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18
Q

when is Engelmann’s experiment?

A

1883 te

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19
Q

What is it?

A

trying to demonstrate the site of photosynthesis in cells
he was a german botanist
he carried out experiments on filamentous green algae
which has a ribbon like structure(chlorella)
O2 is released during photosynthesis so he used motile oxygen sensitive bacteria called pseudomonas which collects in high concentration of oxygen
Engelmann noticed that the bacteria collected at wavelengths of light ( 450 nm) ( blue) and 650 nm red)
At these wavelengths, there was an increased rate of bacteria

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20
Q

Pigment?

A

A molecule that absorbs specific wavelengths of light inside a chloroplast
in plants there are 2 main classes of pigments which act as transducers
Chlorophylls + caroteroids

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21
Q

Pigment in Chlorophyll?

A

Chlorophyll A and Chlorophyll B
Pigment colour =
Blue green for Chlorophyll A
yellow green for Chlorophyll B
A = found in mosses + ferns
B = found in conifers + flowering plants

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22
Q

Carteroids?

A

2 pigments
Beta Carotine
Orange
+ Xanthophyl
Yellow
Found in all plants

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23
Q

Chlorophyll A and B?

A

absorb light in the red and blue regions of the electromagnetic spectrum and they reflect green carotenoids absorb light in the blue/green region + reflect yellow/orange
All chlorophylls have a complex ring structure with a long hydrocarbon tail
if plants lack chlorophyll, they suffer chlorosis which is due to a lack of magnesium
Chlorophyll has a similar structure to haemoglobin
carotenoids could be referred to as accessory pigments.

24
Q

Action spectrum?

A

graph showing how much light is absorbed at different wavelengths

25
Q

Absorption spectrum?

A

graph showing the rate of photosynthesis at different wavelengths

26
Q

Seperating photosynthetic pigments?

A

chromatography
pigments are extracted by grinding up a leaf using a pestle and mortar
the solvent is propanone and the extract is placed on the origin line of the chromatography paper
the solvent rises up the paper and is moved when it reaches the solvent front
distance travelled by the dye + the distance travelled up by the solvent is measured in cm to calculate an Rf value

27
Q

Equation for Rf?

A

distance travelled by the pigment /
distance travelled by the solvent

value is always between 0 and 1

28
Q

Stages of Photosynthesis?

A

Light dependent stage
Light independent stage
Calvin cycle

29
Q

Describe it?

A

Chlorophylls A+ Band accessory pigments are found in the thylakoid membrane of the chloroplast
Pigments are grouped into clusters of hundreds of molecules
Group = the antenna complex
Photosystem consists of antenna complex, containing photosynthetic pigments
Chlorophyll + Carotenoids are anchored to the phospholipids of the thylakoid membrane
each pigment has a different pigment of ;ige to be absorbed
Photons of light are transferred through the antenna complex until they reach the molecules of Chlorophyll A in the reaction centre
When Chlorophyll A absorbs light, it becomes excited and emits an electron.

30
Q

What are the 2 types of reaction centre?

A

Photosystem 1 and Photosystem 2

31
Q

Photosystem 1?

A

arranged around 2 chlorophyll A molecules with an absorption of 700 nm

32
Q

Ps2?

A

arranged around 2 chlorophyll A molecules with an absorption around 680.

33
Q

Phosphorylation?

A

the addition of phosphate ion to ADP

34
Q

Photophosphorylation?

A

implies that energy comes from light

35
Q

Non cyclic photophosphorylation?

A

ATP can be synthesised by electrons which take a linear pathway from water through PS2 and PS1 to NADH2

36
Q

Cyclic photophosphorylation?

A

ATP can be synthesised b electrons that take a cylicial pathway and are recycled back to Chlorophyll A back to PS1
Electrons are transferred from an electron acceptor to oxidised NAD in the stroma
when protons are added to electrons, Hydrogen gas is formed when produces reduced NADP
The photolysis of water takes place in the thylakoid space
H20 absorbs light and dissociates into H+1/2O2+ 2e-
Electrons produced replace those lost from PS2
The protons from water and electrons from PS1 reduce NADP
Oxygen diffuses out of the chloroplast and into intercellular spaces and out through the stoma as a waste product

37
Q

Cyclic Phosphorylation?

A

PSI absorbs protons which excite electrons in the chlorophyll A molecule in the reaction centre
The electrons are admitted and picked up by the electron acceptor which passes them down a species of carriers to PSI
energy released by moving electrons provides 30.6 KJ of energy to Phosphorylate ADP to ATP
Cycle is continuous and non linear

38
Q

Chemiosmosis?

A

electrons pass through a proton pump in the thylakoid membrane and provides energy to the pumps so the protons can be pumped from the stroma to the thylakoid space
H+ ions are in high concentration and generates an electrochemical gradient which a source of potential energy
H+ diffuse through ATP synthetase in thylakoid membrane into the stroma

39
Q

What does the diffusion do?

A

makes energy available to phosphorylate ATP
H+ ions are passed to NADP causing it to be reduced
The removal of H ions from the stroma allows a proton gradient to be maintained

40
Q

Calvin cycle?

A

occurs in solution in the stroma of the chloroplast
involves a sequence of reactions each catalysed by a different enzyme
2 products from light dependent stage are ATP and NADPH2
waste of O2 products
a 5 carbon acceptor molecule called Ribulose Biphosphate combines with CO2 and is catalysed by the enzyme Ribulose Biphosphate (Rubisco)
this is an unstable 6c compound which splits into 2 3c carbons
Carbon compound splits immediately into 2 molecules of Glycerate 3 Phosphate ( 3 carbon sugar)
GP is reduced to triose Phosphate known as glyceraldehyde 3 phosphate
Triose Phosphate = the first carbohydrate to be made in photosynthesis
From the unstable 6c compound to TP energy is required in the form of ATP
TP is converted to glucose Phosphate which forms ht epolymer starch during condensation
5/6 glyceraldehyde - 3 phosphate is used to reform Ribulose Biphosphate
Cycle will need to be repeated 6 times to generate 1 molecule of glucose

41
Q

How do plants use carbohydrates?

A

Product synthesis
Carbohydrates
first hexose synthesises is fructose Biphosphate
This is converted to Glucose which combines with fructose to form sucrose
Sucrose is used to transport energy in the phloem vessel
Alpha glucose may be converted to starch for storage in roots and seeds
Alpha glucose is polymerised into cellulose for repair of cell walls

42
Q

Fats?

A

Acetyl Co enzyme A can be synthesised from glycerate 3 phosphate made in the calvin cycle + converted to fatty acids
TP can be converted directly to glycerol (3c)
Fatty acids + glycerol combine in a condensation reaction to form triglycerides

43
Q

Proteins?

A

Glycerate - 3 - phosphate is converted to amino acids which combine to form proteins

44
Q

Limiting factors of Photosynthesis?

A

Light of a specific wavelength, frequency + intensity
CO2 and water
Suitable temp
if any factor is lacking, Photosynthesis cannot take place
each factor has an optimumvalue

45
Q

Limiting factor def?

A

factor that limits rate of a physical process by being in a short supply

46
Q

CO2 concentration?

A

As CO2 concentration increases from O, the light reaction also increases
Rate of photosynthesis increases but if CO2 increases above 0.5 %, rate of photosynthesis remains constant
rate of photosynthesis decreases above 1 % CO2 concentration

47
Q

What do aquatic plants use CO2 from?

A

HCO3- ions which are formed when CO2 dissolves in CO2

H2O+C02—H2CO3—-H++HCO3-

algae - carbonic anhydrase

48
Q

Rate limiting step?

A

slowest reaction and is limited by enzyme rubisco

49
Q

Light intenisty?

A

If a plant is in darkness, the light independent reaction continues but the light dependent doesnt, so no O2 is involved
As light intensity increases, the efficiency also increases so the rate of Photosynthesis increases
At 10,000 Lux, the reactions of the light dependent stage at a maximum
( If the light intensity is increased, the rate of Photosynthesis remains constant so above 10,000, intensity is not a limiting factor)
If extreme light intensity, the photosynthetic pigments = damaged so the rate of Photosynthesis decreases

50
Q

Why is light intensity a limiting factor?

A

because it controls the rate of photosynthesis

51
Q

Temperature?

A

increasing the temp, increases the rate of photosynthesis
if temp increases significantly, the enzymes denature so it is a limiting factor

52
Q

Water?

A

If water is scarce, plant cells are plasmolysed, stomata close + wilting occurs.
Water availability is a limiting factor

53
Q

Light comonsenation point?

A

light intensity at which there is no net gas exchange the volume of gas from respiration is equal to the volume of gas from photsynthesis

54
Q

Mineral nutrition?

A

inorganic nutrients are needed by plants for structure, synthesis of enzymes and the synthesis of chlorophyll
macronutrients are N,K,Mg,Ca,NO3-,PO43-
Micronutrients = manganese and copper

55
Q

Nitrogen?

A

In the soil as humus
Inorganic N in the form of Ammonium ions and nitrate ions
Nitrogen = taken up by the roots in the form of nutrients which are transported in the xylem vessels to the cells.
Nitrate is converted to ammonium ions which are deaminated to produce amino acids which are transported in the phloem for the synthesis of proteins
Nitrogen is a component of chlorophyll and if its deficient, suffers from chloroysis

56
Q

Where is Mg2+ transported in?

A

the xylem
Mg2+ is a constituent of chlorophyll
Mg2+ is used as an enzyme activator in ATPase

57
Q
A

Biology A2 (9 decks)

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