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Biology > Photosynthesis - Module 5 > Flashcards

Photosynthesis - Module 5 Flashcards

1
Q

Components of a chloroplast

A

-Outer membrane
-inner membrane
-Lamella
-Stroma
-Grana (made of thylakoids) (singular granum)
-Thylakoids

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2
Q

stroma

A

-gel-like substance
-contains sugars, enzymes, organic acids
-Contains circular chloroplast DNA
-Carbs produced by photosynthesis, then stored as starch grains in stroma if not used

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3
Q

Photosynthetic pigments

e.g

A

e.g, Chlorophyll a, chlorophyll b and carotene
Coloured substances, absorb light energy needed for photosynthesis

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4
Q

Photosystem

A

The collective light harvesting system And reaction centre

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5
Q

How can Water stress affect photosynthesis

A

When plants don’t have enough water, what will happen?
Stomata will close to preserve water
Less carbon dioxide will enter the leaf for the Calvin cycle and slow photosynthesis down

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6
Q

As light intensity ( at the correct wavelength) increases, The rate of photosynthesis…

Explain why

A

Increases

As the light intensity increases, more stomata are open. Therefore more carbon dioxide can diffuse into the leaf for the Calvin cycle.

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7
Q

As light intensity decreases, rate of photosynthesis ….

explain why

A

Decreases

As light intensity decreases, stomata close so less carbon dioxide. Less electrons excited in LD reactions.

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8
Q

Effect of reduced light intensity on Light dependent reaction

A

Less ATP and NADPH made-> less electrons excited, less go through ETC, less energy to pump protons, less protons pass through ATP synthase.

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9
Q

Effect of reduced light intensity on Light independent reaction:

Effect on GP,TP,RuBP

A

INITIALLY RuBP still combing with CO2 to make GP.

Levels of RuBP decreasing, levels of GP increasing.

GP can’t be reduced ( using NADPH and ATP) to make TP so level of TP decrease.
TP can’t be used to regenerate RuBP.

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10
Q

WHAT HAPPENS TO THE Relative concentrations of GP, RuBP, TP

when there is a reduced light intensity

A

Relative concentrations:

GP- increasing as still being made

RuBP- decreasing

TP- decreasing

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11
Q

Effect of Increased temperature on rate of photosynthesis

explain why

A

As temperature increases, so does rate of photosynthesis until optimum as molecules gain kinetic energy.

After this it decreases until no photosynthesis can take place.

High temperature – enzymes denature, stomata close and damage could occur to thylakoid membrane, chloroplast membrane and chlorophyll.

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12
Q

Effect of lower temperature on rate of photosynthesis

A

Low temperature – less kinetic energy, reactions slower, enzymes inactive under 10ºC

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13
Q

Effects of Low temps on relative conc. of RuBP, GP, TP

why

A

Low temps- all reactions will be slower
Levels of GP, TP and RuBP will all fall.

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14
Q

Effects of extreme high temps on relative conc. of RuBP, GP, TP

why

A

High temperatures- enzymes denature e.g ATP synthase, RuBisCO.
Less ATP produced to reduced GP to TP and regenerate TP to RuBP
RuBisCO can’t catalyse reaction between CO2 and RuBP, less GP made so less TP made and less TP to regenerate RuBP
Levels of RuBP, GP and TP will fall.

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15
Q

Effect of increased carbon dioxide concentration on rate of photosynthesis

A

As carbon dioxide concentration increases, so does rate of photosynthesis.

After 0.4%, stomata will close.

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16
Q

Effect of decreased carbon dioxide concentration on rate of photosynthesis

A

Decrease- less CO2 for light independent reaction.

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17
Q

Effects of decreased carbon dioxide concentration on relative conc. of RuBP, GP, TP

why

A

Less CO2 to combine with RuBP to form GP -> levels of GP fall.
Less GP to make TP, levels of TP fall.
Some RuBP still being made and not used so increases.

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18
Q

What is the compensation point?

A

When the rate of photosynthesis equals the rate of respiration

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19
Q

How would you describe the limits of a limiting factor graph with light intensity plotted against Rate of photosynthesis
(it increases and then plateaus)

(Point A is origin, Point B is where the graph plateaus)

A

Between A-B, rate of photosynthesis is limited by light intensity.
B= saturation point increasing light intensity at this point has no effect as something else is limiting.

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20
Q

Which wavelengths are mainly absorbed by chlorophyll?

A

chlorophyll absorbs light in the red (long wavelength) and the blue (short wavelength) regions of the visible light spectrum. Green light is not absorbed but reflected, making the plant appear green.

21
Q

Photosystem-

A

Photosystem- Photosynthetic pigment + protein- found in thylakoid membrane. Funnel shaped

22
Q

Primary pigment

A

Primary pigment- reaction centres where electrons are excited during light-dependent reaction. Mostly chlorophyll a

23
Q

Accessory pigments

A

Accessory pigments- Make up light-harvesting systems which surround primary pigments and transfer light energy to them. E.g chlorophyll b, carotenoids

24
Q

Photosystem 1- Absorbs light best at a wavelength of ______

A

700nm

25
Q

Photosystem 2- Absorbs light best at a wavelength of ____

A

680nm

26
Q

Chlorophyll a absorbs mainly ____ and ___ light but reflects ______- reason leaves look green

A

blue

red

green

27
Q

Chlorophyll is not produced when there is ____ or ___ sunlight e.g _______
This means you can see other pigments in leaves such as __(a colour)____ ________

A

little

no

Autumn

Orange

carotenoids

28
Q

Two stages of photosynthesis

A

Light Dependent

Light independent

29
Q

very Basic summary of Light Dependent Reaction

A

in thylakoid membrane
Light energy is absorbed by photosynthetic pigments in the photosystems and converted to chemical energy
Forms ATP and NADPH

30
Q

Basic summary of Light independent Reaction

A

in stroma
- ATP and NADPH supply energy and hydrogen to make glucose from carbon dioxide.

31
Q

Light energy absorbed by photosystems is used for:

A

Making reduced NADP from NADP

Photolysis- Splitting water into protons, electrons and oxygen using light energy.

Making ATP from ADP & Pi = photophosphorylation ( adding phosphate to a molecule using light energy)  non-cyclic and cyclic

32
Q

Non-cyclic photophosphorylation

A

Light energy absorbed by PSII and excites electrons

High energy electrons move along ETC to PSI

As excited electrons leave PSII, photolysis of water occurs giving protons, electrons and oxygen electrons re-enter PSII

Excited electrons lose(transfer) energy at each carrier in the ETC

The energy is used to pump protons from stroma to thylakoid space, forming a proton gradient.

Protons re-enter the stroma by facilitated diffusion through ATP synthase (chemiosmosis)

Energy from this movement combines ADP + Pi to form ATP. This is photophosphorylation

Light energy is absorbed by PSI which excites electrons again to a higher energy level

Finally electrons are transferred to NADP , alongside a proton from the stroma, to form NADPH.

33
Q

Cyclic photophosphorylation

A

Only uses PSI

Only forms ATP ( no NADPH or oxygen)

Electrons aren’t passed on to NADP but are passed back to PSI by electron carriers- cyclic

Electrons are recycled so can repeatedly pass back into PSI

ATP is still formed by chemiosmosis- less than non-cyclic

34
Q

Basic summary of The light-independent stage ( The Calvin cycle)

A

Takes place in the stroma of the chloroplasts.
Uses CO2 as a raw material.
Uses NADPH and ATP from the light-dependent stage.
Used to make organic substances.

35
Q

Calvin cycle summary

A

Carbon dioxide diffuses into stroma and combines with ribulose bisphosphate(5C)- catalysed by RuBisCO. FIXATION (CO2 is incorporated into an organic molecule)

Forms a 6C unstable intermediate compound which splits up into 2 x glycerate-3 phosphate (3C).

(GP can be used to make amino acids and Fatty acids)

The GP is reduced by NADPH to form 2x triose phosphate. Energy from ATP is also used. REDUCTION

1 out of 6 TP molecules is used to form organic substances e.g glucose.

(TP can also be used to make Glycerol which combines with Fatty acids made from GP to make Lipids)

5 out of 6 TP molecules are used to regenerate RuBP. REGENERATION

36
Q

What sugars + carbs are made from photosynthesis

A

-Hexose sugars- e.g Glucose

-Starch
-Cellulose
-Fructose
-Sucrose (glucose + fructose)

37
Q

Why would a leaf receiving only green light become more acidic/Lower the PH

A

-leaf reflects green light
-(green light) cannot be used in photosynthesis/no LD reaction
-little/no photolysis
-little/no CO2 taken up/fixed
-Some CO2 produced during respiration
-(slight) increase in CO2, increases acidity/decreases pH
-Accessory pigments absorb some green light

38
Q

How can factors other than light conditions be controlled in a glasshouse to increase the rate of photosynthesis and maximise production?

A

-photosynthesis controlled by photosynthetic enzymes.
-Temperature maintained via ___ (air con)
-Increased Co2 conc, so is not limiting factor
-easier to control water supply/irrigation/humidity/minerals/fertiliser
-Biological control e.g: pesticides

39
Q

Herbicides interfere with electron transport by accepting electrons

suggest how this may cause plants to die

A

no photophosphorylation, no ATP produced, no NADPH produced, no calvin cycle, no fixation of CO2

40
Q

When plants grow in glasshouse during winter, when natural light intensities are low, temperatures must be kept low too.

with reference to respiration and photosynthesis, WHY?

A

light intensity limiting factor
-low rate of photosynthesis
-rate of respiration increases at higher temperatures
-rate respiration close to/exceeds rate of photosynthesis
-Sugars broken down more quickly than formed

41
Q

chromatography is used to

A

separate dissolved substances

42
Q

Stationary phase of chromatography

A

Paper

43
Q

Mobile phase of chromatography

A

Solvent

44
Q

Adsorption - chromatography

A

interactions with stationary phase -> stronger the adsorption, the slower the molecules move

45
Q

TLC ->

A

Thin layer chromotography

46
Q

why does the rate pf plant respiration decrease st night

A

daytime temperature is higher than night time temperature

rate of respiration increases with higher temperatures as enzymes are temperature dependant

47
Q

when asked to describe how the student could improve the presentation of their data, what must you discuss

A

-Units shown

-table presentation
-headings

-graph

48
Q

where does the light independent reaction take place

A

stroma

Biology (45 decks)

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