Photosynthesis 5.2.1

Front 1

Photosynthesis

Back 1

Light energy from the sun is transformed into chemical energy and used to synthesis large organic molecules from inorganic substances.

Front 2

Autotroph

Back 2

Organisms that use light energy or chemical energy and inorganic molecules to synthesise complex organic molecules

Front 3

Heterotroph

Back 3

Organisms that ingest and digest complex organic molecules from other organisms, releasing the chemical potential energy stored in them

Front 4

Chloroplast Structure

Back 4

Front 5

Chloroplast Adaptations

Back 5

Inner membrane is selectively permeable and has transport proteins, Stroma is the fluid that fills chloroplasts and contains enzymes for Light Independent Reactions. Thylakoids are stacked (Grana) to increase SA.

Front 6

Photosynthetic Pigments

Back 6

Molecules which absorb light energy, each pigment absorbs a range of wavelengths in the visible region. Each pigment has its own distinct peak of absorbtion.

Front 7

Pigment Arrangement

Back 7

The pigments that absorb light are found in a photosystem.A photosystem contains the reaction centre which contains the primary pigment. The reaction centre is surrounded by a light harvesting system/complex, which contains accessory pigments.

Front 8

Photosystem

Back 8

The reaction centre (containing the primary pigment) and the accessory pigments.

Front 9

Photosystem II

Back 9

PSII, Chlorophyll a P680 at its centre, therefore peak absorbtion is light at wavelenght 680nm.

Front 10

Photosystem I

Back 10

PSI, Chlorophyll a P700 at its centre. Therefore peak absorbtion is light at wavelength 700nm.

Front 11

Light Dependent Stage

Back 11

PSII is excited by photons causing electrons to be excited, the electrons are passed down the ECT. Photolysis of H2O replaces these electrons. Electrons of PSI are also excited and passed down the ECT, these electrons are replaced by the PSII electrons. H+ ions are pumped into the lumen of Thylakoid from energy of the ECT. H+ ions move through ATP synthase forming ATP.

Front 12

Photolysis

Back 12

Splitting of water with light in PSII, Oxygen is a waste product and is released. H+ undegoes chemiosmosis and flow through ATP Synthase. Electrons replace lost electrons from PSII (Cyclic Photophosphorylation).

Front 13

Light Independent Stage

Back 13

Takes place in the stroma, organic molecules like glucose are produced in a series of reactions known as the Calvin Cycle.

Front 14

Calvin Cycle (Stages)

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1. Fixation, 2. Reduction, 3. Regeneration.

Front 15

Carbon Fixation

Back 15

Carbon dioxide is combined with Ribulose Bisphosphate (RuBP). This forms a 6C molecule. This reaction is catalysed by the enzyme RuBisCO. The unstable 6C compound splits to form 2 x GP.

Front 16

Reduction

Back 16

GP is reduced, gaining Hydorgen and phosphorylated, forming triose phosphate.

Front 17

Regeneration

Back 17

5/6 TP produced reform 3 RuBP. 1/6 is used to form glucose and other hexose sugars.

Front 18

Factors affecting Photosynthesis

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Light Intensity, CO2, Temperature

Front 19

Photorespiration

Back 19

Mainly occurs during periods of water stress when plants close stomata to conserve water. Carbon dioxide can no longer enter . Carbon dioxide levels fall as it is used up in the Calvin cycle. Oxygen levels rise as it is still produced via the light reactions. Photorespiration is inefficent and does not lead to the production of sugars.