17.1 & 17.2

:

17.0 PHOTOSYNTHESIS

17.0 Photosynthesis

1) 17.1 Overview of photosynthesis 2) 17.2 Absorption spectrum of

photosynthesis pigments 3) 17.3 Light Dependent Reaction 4) 17.4 Light Independent Reaction/Calvin

Cycle 5) 17.5 Alternative mechanisms of carbon

Fixation : Hatch Slack (C4) and Crassulacean Acid Metabolism (CAM) pathways

Learning outcomes :

17.1 Overview of Photosynthesis

Give overall outline of photosynthetic

process that lead to the production of

glucose

PHOTOSYNTHESIS

• Photosynthesis is the synthesis of organic

compounds from simple inorganic materials,

namely carbon dioxide and water

• With the presence of chlorophyll that absorbs

the light energy

• Whereby the light energy is converted to

chemical energy that is stored in glucose or

other organic compound such as proteins and

lipids

Learning Outcomes : 17.1 : Give overall outline of photosynthetic process that leads to the production of glucose

• It occurs in plants, algae and certain prokaryotes

• The overall equation for photosynthesis is :

6CO2 + 12H2O + 18ATP + 12NADPH --->

C6H12O6 + 6O2 + 6H2O + 18ADP + 12NADP+ +

18Pi

• Oxygen is released as a by-product

• Photosynthesis is an endergonic process


CHLOROPLAST

• Any green part of a plant has chloroplasts.

• However, the leaves are the major site of photosynthesis

for most plants.

• There are about half a million chloroplasts per square

millimeter of leaf surface.

• The color of a leaf comes from chlorophyll, the green

pigment in the chloroplasts.

• Chlorophyll plays an important role in the absorption of

light energy during photosynthesis.


Structure of Chloroplast


• Chloroplasts are found mainly in mesophyll cells

forming the tissues in the interior of the leaf.

• O2 exits and CO2 enters the leaf through microscopic

pores, stomata, in the leaf.

• Veins deliver water from the roots and carry off sugar

from mesophyll cells to other plant areas.


• Each chloroplast has two membranes around a central

aqueous space, the stroma.

• In the stroma are membranous sacs, the thylakoids.

• These have an internal aqueous space, the thylakoid

lumen or thylakoid space.

• Thylakoids may be stacked into columns called grana


17.0 Photosynthesis

1) 17.1 Overview of photosynthesis 2) 17.2 Absorption spectrum of

photosynthesis pigments 3) 17.3 Light Dependent Reaction 4) 17.4 Light Independent Reaction/Calvin

Cycle 5) 17.5 Alternative mechanisms of carbon

Fixation : Hatch Slack (C4) and Crassulacean Acid Metabolism (CAM) pathways

Learning outcomes :

17.2 Absorption spectrum of

photosynthetic pigments

State the photosynthetic pigments

involved in photosynthesis

PHOTOSYNTHETIC PIGMENTS

• Photosynthesis occurs in the chloroplasts in which

chlorophylls are the most important pigments.

• It gives the green colour to the plants

• Chlorophyll is the green pigment that absorbs light

energy and it is a mixture of pigments that comprises :

Chlorophyll a (blue-green pigment) & chlorophyll b

(yellow-green pigment)

Some carotenoids : B-carotene (orange) & xanthophyll

(yellow)

Phaeophytin (grey)

Learning Outcomes : 17.2 : State the photosynthetic pigments involved in photosynthesis

• Chlorophylls a : mainly absorbs light in blue-violet

(430nm) and red (662 nm) region

• Chlorophylls b : absorbs light 453 nm and 642 nm

• Carotenoids : carotenes, xanthophylls, absorbs blue-

violet region (460-550 nm)

Light absorption spectrum

Learning Outcomes : 17.2 : State the photosynthetic pigments involved in photosynthesis

17.1 & 17.2

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