PhotosynthesisWhere does all that glucose come from?

Chapter 3Chapter 3

How does it do that?

Photosynthesis uses radiant energy from the sun to fix carbon dioxide into carbohydrates

The captured radiant energy is stored within the bonds of the carbohydrate as chemical energy

What is it?

CO2

CO2

CO2

CO2

CO2

CO2

radiant energy

Photosynthesisglucose

Photosynthesis is used by many autotrophs Photosynthesis is used by many autotrophs to make their own foodto make their own food egs. vascular plants, algae, cyanobacteriaegs. vascular plants, algae, cyanobacteria

That’s a lot of photosynthesis

http://www.smhi.se/weather/baws_ext/info/2004/Baltic_algae_2004_en.htm

Overall (Net) Equation

O2

glucose

CO2 H2OH+H+ EnergyCO2 + H2O + energy glucose + O2

Photosynthesis

glucose + O2 CO2 + H2O + energy

Overall (Net) Equation

CO2 H2OH+H+ Energy

O2

glucose

Cellular RespirationPhotosynthesis

Photosynthesis and Cellular Respiration appear to be reverse processes, but they

use very different mechanisms

Similarities

Both cellular respiration and Photosynthesis are similar in that both use:

1. electron transport chains

2. dissolved enzymes

3. membrane-enclosed space for chemiosmosis

Plant Tissues

Plants are made of various types of tissues egs. Stem, leaves, roots,

reproductive organs

The main site of photosynthesis is the leaves, although chloroplasts are found in all green plant parts

Leaves

vascular bundle

palisade mesophyll

spongy mesophyll

epidermis

cuticle

stomate

EpidermisMesophyllVascular Bundles

Leaves

Leaves have 3 main types of tissues:

1. Epidermis Usually one cell thick and secrets a waxy

cuticle to prevent water loss Pores called stomata found in lower

epidermis

epidermis

vascular bundle

palisade mesophyll

cuticle

spongy mesophyll

stomate

Leaves

2. Mesophyll Most photosynthesis occurs here Two layers of parenchyma cells

• Palisade layer◦ Cell arrangement maximizes exposure to light

• Spongy layer◦ Loose arrangement of cells leaving air spaces for gas exchange

epidermis

vascular bundle

palisade mesophyll

cuticle

spongy mesophyll

stomate

Leaves

3. Vascular Bundles Transport system of the plants Contains xylem (water transport) and

phloem (sugar transport)

epidermis

vascular bundle

palisade mesophyll

cuticle

spongy mesophyll

stomate

Opening/Closing Stomata

The guard cells (stomata) can be opened and closed to regulate gas exchange and minimize water loss in leaves

Chloroplast Pore

Guard Cells

OPEN CLOSED

CLOSED

Opening Stomata

To open the stomata: Potassium ions (K+) are

actively pumped into the guard cells (uses ATP)

This causes the GCs to become hypertonic to their surroundings

Water is drawn into the GCs, increasing turgor pressure

OPEN

ATP

ATP

ATP ATP

ATP

ATPK+

K+

K+

K+

K+

K+

H2

O

H+

H+ H2

O

H+

H+

Cell is now hypertonic to surroundings

Closing Stomata

To close the stomata: K+ pumps deactivated

allowing ions to diffuse out Water drawn back out of the

GC with the K+ ions Decrease in turgor

pressure makes GCs go limp (flacid)

ATPATP

ATP

ATP

ATP

ATP

K+

K+

K+

K+

K+

K+

OPEN

Closing Stomata

To close the stomata: K+ pumps deactivated

allowing ions to diffuse out Water drawn back out of the

GC with the K+ ions Decrease in turgor

pressure makes GCs go limp (flacid)

K+

K+

K+

K+

K+

K+

OPEN

H2OH+H+

H2OH+H+

Cell is now hypotonic to surroundings

Closing Stomata

To close the stomata: K+ pumps deactivated

allowing ions to diffuse out Water drawn back out of the

GC with the K+ ions Decrease in turgor

pressure makes GCs go limp (flacid)OPEN

H2

OH+

H+

H2

O H+

H+

CLOSED