BIOCHEMICALS PATHWAYS

Photosynthesis

PHOTOSYNTHESIS

• PHOTOSYNTHESIS OCCURS WITHIN CHLOROPLASTS

• RADIANT ENERGY (SUNLIGHT) IS CONVERTED TO CHEMICAL ENERGY

• CHLOROPHYLL AND ENZYMES ARE INVOLVED IN THE CONVERSION

PHOTOSYNTHESIS

• The green colouring in chloroplasts derive from four different pigments

1 Chlorophyll - a green

2 Chlorophyll - b green

3 Xanthophyll - yellow

4 Carotene - orange

PHOTOSYNTHESIS

• The pigments appear green because

1.they reflect the green part of sunlight

2. they absorb the blue and red part of the sunlight

3.carotene reflects orange and absorbs blue light

4.xanthophyll reflects yellow and absorbs blue light

PHOTOSYNTHESIS

• a Chlorophyll is the most common of the plant pigments

• The formula is C55H72O5N4Mg

• It has ring structure with alternating single and double bonds

Chlorophyll

• Chlorophyll is found in plants and cyanobacteria

• Chloroplasts are organelles containing the pigment

• Chlorophyll is located on the surface of internal membranes

Chloroplast

Wavelengths

• Light has wave like properties• The frequency represents the number of

waves per second• The units are called Hertz (Hz)• The wave length is measured in nanometres

10-9 metres

ABSORPTION SPECTRA

ACTION SPECTRUM• Together all the pigments form the

ACTION SPECTRUM

PHOTOSYNTHESIS

• When electrons resonate between adjacent atoms through these bonds it is said to be EXCITED

• The energy from the excited state becomes available for biochemical reactions

• however Chlorophyll a misses some of the red and blue part of the spectrum

• Other pigments can help absorb that light

PHOTOSYNTHESIS formula

• Carbon dioxide + water

• light + chlorophyll

• glucose + water + oxygen• This is only the rough over all equation

PHOTOSYNTHESIS and ATP

• Photosynthesis is used to form the energy molecule

•ATP• Adenosine Triphosphate

PHOTOSYNTHESIS

• Photosynthesis is comprised of 2 stages

1. LIGHT REACTIONS (Light dependant)

2. DARK REACTIONS (Light independent)

Light Dependant

• Chlorophyll traps light to produce ATP• This ATP provides the energy to combine

the CO2 and hydrogen to form glucose• This takes place on the internal membranes

of the chloroplast• Water is split producing H+

• Oxygen is a by-product• 18 ATP molecules

Light Dependant2

Light Reaction 3

Light independent

• Does not require light to function• It mostly occurs in the stroma• Carbon dioxide diffuses into the chloroplast

and becomes involved in the CALVIN CYCLE or pathway

• The 18 ATP molecules provide the energy to fuse 3 carbon atoms

Carbon pathways

• There are two Carbon Pathways C3 and C4

• These represent the first stable Carbon molecule made in Photosynthesis

• C3 has 3 carbons

• C4 has 4 carbons

• The Calvin Cycle produces C3

Calvin Cycle

PHOTOSYNTHESIS Reactions

PHOTOSYNTHESIS Reactions

PHOTOSYNTHESIS Reactions

Dark Reaction 1

Dark Reaction 2

PHOTOSYNTHESIS Homework