|
Reaction that
-requires light indirectly
-uses stored energy to convert(fix) CO2 into carbohydrates |
dark reaction |
|
|
Reaction that
-converts and stores energy in energy transfer molecules (ATP) |
light reaction |
|
|
define photophosphorylation |
-describes light dependent reactions
-use of light energy to phosphorylate a molecule( ie:ADP) |
|
|
Which evolved first, cyclic or non-cyclic photophosphorylation |
cyclic |
|
|
The reaction center for cyclic photophosphorylation |
P700 |
|
|
First and Last enzymes of the photosynthetic electron transport chain |
FeS is First
and PC (plastocyanin) is Last |
|
|
Cyclic Photophosphorylation |
-Excited (e-) releases energy in stepwise manner
-ezymatically aided (electron transport chain)
-released energy at (PQ->Cyt F) phosphorylates (ADP-> ATP)
-ground state electron returns to chlorophyll |
the steps of |
|
photosystem I (1) consists of |
- Antenna molecules
- P700 reaction center
- Electron transport chain (FeS to Fd to FAD) |
|
|
Non cyclic photophosphorylation |
-P700 (e-) leaves transport chain at Fd(ferredoxin)
-is passed to FAD -> NADP , energy released here makes ADP-> ATP
-NADP red. acts as electron donor in the reduction of CO2 to carbohydrate (carbon fixation)
-P680 (e-) fills electron holes in P700 |
|
|
electron holes |
Electron deficit in photosystem I caused by carbon fixation, that is corrected by addition of (e-) from H2O |
|
|
Photosystem II(2) consists of |
- antenna molecules
- P680 reaction center
- electron transport molecules |
|
|
H20 's role with P680 |
- passes (e-) through enzyme Z to P680
- forms 02 and 4H+ |
|
|
Can replace H2O in photosynthesis |
- strong electron donors
- ie: H2S - gives off sulfer not O2 as a product |
|
|
Chloroplast structure |
- inner membrane : smooth and flat, shaped to outer membrane
- third membrane inside stroma
forms flat interconnected compartments called thylakoids |
|
|
Contents of Thylakoid |
antenna pigments, Electron Transport chains, |
|
|
stromal thylakoids vs grana |
stromal - loose in stroma, ribbon-like, high surface area to absorb CO2
grana - densely packed, low CO2 absorption , high photon absorption |
|
|
Distribution of Charges in Chloroplasts |
- H+ accumulates in innermost compartment of chloroplast
- outer compartment ( stroma becomes negatively charged) |
|
|
Entrance point for H+ into thylakoid interior / inner compartment |
PQ and Z |
|
|
when is the cyclic pathway favored by (e-) |
-NADP ox. is in short supply
-Greater need for ATP than NADP red. |
|
|
(e-) that do not enter cyclic pathway make.... |
NADP red. |
|
|
Utilizes H+ gradient in thylakoid membrane |
CF-1 complex |
|
|
Calvin Cycle |
- CO2 combines with 5-Carbon sugar RuBP forming unstable 6-C compound
-broken down into two 3-Carbon PGA
- PGA phosphorylated by ATP and reduced by NADPred.
- two 3-Carbon PGAL form
- 5 of every 6 PGAL make RuBP and 1 combines with another to form 6-Carbon glucose |
|
|
Rubisco ( RuBP carboxylase) |
-catalyzes carboxylation of RuBP->
favored when CO2 is high, continues Calvin cycle
-catalyzes the oxidation of RuBP by O2->
favored when CO2 is low, or temperatures above normal, starts photorespiration |
|
|
photorespiration |
- breaks down intermediate molecules from the calvin cycle
- produces CO2 |
|
|
funtion of cuticle and epidermis |
-cuticle covers epidermis
-epidermis protects internal tissues, protect from excessive water loss, from invasion of fungi & from mechanical injury |
|
|
mesophyll |
-region between upper and lower epidermis |
|
|
stomata |
-holes in epidermis that open to atmosphere outside of the leaf
-size controlled by guard cells |
|
|
Vascular Bundle |
- veins in leaf
- act as transport pathway
- contain xylem and phloem
- |
|
|
Kranz anatomy - C4 plants |
-ringlike arrangement of phosynthetic cells ( contain enlarged chloroplasts) around leaf veins of C4 plants
-these cells accumulate starch in light
-reduced number of chloroplasts, and greater number of grana in spongy mesohpyll |
|
|
palisade mesophyll and spongy mesophyll |
palisade - upper,vertically arranged, cylindrical shaped
spongy- lower, irregular shaped |
|
|
Location of Kranz/C4 plants |
High temperature, intense light, when stomatal closure results in low CO2 and high O2 inside of leaf |
|
|
C4 photosynthesis |
-CO2 combines with 3-Carbon PEP -> forms 4-Carbon compound
-responsible enzyme cannot create O2 and is not inhibited by it |
|
|
Hatch-Slack pathway - C4 photosynthesis |
-CO2 combines with PEP, forms 4-Carbon compound
-reduced by NADPred.
-passes into bundle sheath cell
-oxidized by NADPox.
-Form 3-C compound and CO2
-3-C compound returns to mesophyll to form PEP
-CO2 enters Calvin Cycle |
|
|
Crassulacean Acid Metabolism (CAM) |
- succulent plants that store water in fleshy leaves
- close stomata during day, open them at night
- necessary CO2 stored as malic acid and isocitric acid
- release in cells during day |
|
|
CAM vs C4 |
C4- anatomical seperation of CO2 fixation
CAM - temporary seperation |
|
