Photosynthesis How producers use sun energy to make organic food! Campbell Ch 7

THE DISCOVERY OF PHOTOSYNTHESIS (Experiments on what plants “eat”)

Jan Baptiste van Helmont: 1648 Conclusion? plant doesn’t eat soil, but DOES require water & sun…

Joseph Preistley: 1772 Conclusions? Candles & animals require O 2 and give off CO 2 Plants require CO 2 and give off O 2

So, producers must do photosynthesis like this… CO 2 + H 2 O C 6 H 12 O 6 + O 2 sun Balanced: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2

Photosynthesis is an Endergonic Reaction Energy

What is light? Radiant energy composed of photons Categorized according to wavelength/energy Shorter wavelength = greater energy!

Categorized according to wavelength/energy Shorter wavelength = greater energy!

10 Question: During the fall, what causes the leaves to change colors?

Leaf colors vary

During the fall, the plant stops wasting energy to make chlorophyll to prepare for winter. The chlorophyll in the leaves is either broken down by the plant, or degraded by the sun. This leaves behind the more stable carotenoids resulting in more reds, oranges, and yellows.

Why might light color affect photosynthesis?

14 Fall Colors In addition to the chlorophyll pigments, there are other pigments presentIn addition to the chlorophyll pigments, there are other pigments present During the fall, the green chlorophyll pigments are greatly reduced revealing the other pigmentsDuring the fall, the green chlorophyll pigments are greatly reduced revealing the other pigments Chlorophyll is reabsorbed/degradedChlorophyll is reabsorbed/degraded The name chlorophyll comes from the Greek words chloros (green) and phyllon (leaf) Carotenoids are pigments that are either red, orange, or yellowCarotenoids are pigments that are either red, orange, or yellow

Why is it beneficial for plants to have several pigments? To absorb the most wavelengths of light possible! = MORE PHOTOSYNTHESIS

Different greens Why so many shades and depths of green?

Different elevations, same tree type:

Figure 2. Sun intolerant plants (left) will photooxidize when exposed to excessive light (right).

Plants respond to light conditions Plants with adequate light are bushy, with closely set deep green leaves. Plants in shade grow tall and spindly, with pale green leaves

HOW IS SUN ENERGY HARVESTED?

21 Photosynthesis Anabolic (small molecules combined)Anabolic (small molecules combined) Endergonic (stores energy)Endergonic (stores energy) Carbon dioxide (CO 2 ) requiring process that uses light energy (photons) and water (H 2 O) to produce organic macromolecules (glucose).Carbon dioxide (CO 2 ) requiring process that uses light energy (photons) and water (H 2 O) to produce organic macromolecules (glucose). 6CO 2 + 6H 2 O  C 6 H 12 O 6 + 6O 2 glucose SUN photons

22 Question: What parts of the plant help accomplish photosynthesis?

Whole leaf organ Leaf tissues Photosynthetic cell Chloroplast organelle Thylakoids (stacks of membranes studded with chlorophyll – lots of surface area for sun absorption!) The location of photosynthesis.

24 Plants Photosynthesis:Photosynthesis: Mainly occurs in the leaves:Mainly occurs in the leaves: a.stoma - pores b.mesophyll cells Stoma Mesophyll Cell Chloroplast

25 Stomata (stoma) Pores in a plant’s epidermis through which water vapor and gases (CO 2 & O 2 ) are exchanged between the plant and the atmosphere. Guard Cell Carbon Dioxide (CO 2 ) Oxygen (O 2 ) Found on the underside of leaves Stoma

26 Mesophyll Cell of Leaf Cell Wall Nucleus Chloroplast Central Vacuole Photosynthesis occurs in these cells!

How does the plant move water and glucose throughout the plant? Xylem – water and minerals flow up from the roots, then out through the stomata.

How does the plant move water and glucose throughout the plant? Phloem (“Phood”) – sugar moves up and down the plant. Things that could happen to the sugar? –Stored –Used for energy –Added to fruit to attract heterotrophs. –Make cellulose for strength/cell walls

29 Chloroplast Organellephotosynthesis Organelle where photosynthesis takes place. Granum Thylakoid Stroma Outer Membrane Inner Membrane Thylakoid stacks are connected together

30 Thylakoid Thylakoid Membrane Thylakoid Space Granum Grana make up the inner membrane