Download - Photosynthesis
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