Photosynthesis

Front 1

Photosynthesis Equation

Back 1

light + 6H2O -> C6H12O6 + 6O2

Front 2

"Excited Electrons"

Back 2

energized electrons due to the light on the pigments

Front 3

Photophosphorylation

Back 3

process of making ATP from ADP + Pi using energy derived from light, Non cyclic starts with PS II

Front 4

Photosystem II

Back 4

First step of noncyclic photophosphorylation, electrons trapped by P680 in photosystem II are energized by light. There is an increse in their energy

Front 5

Primary Electron Acceptor

Back 5

2nd step in noncyclic photo..., two energized electrons are passed to this molecule. This electron is called "primary" because it is the first in a chain of electron acceptors

Front 6

Electron Transport Chain

Back 6

3rd step in noncyclic photo.. electrons pass through this which consists of proteins that pass electrons from one carrier protein to the next. Some carrier proteins, like ferredoxin and cytochrome, include nonprotein parts containing iron

Front 7

Ferredoxin and Cytochrome

Back 7

some of the carrier proteins in the electron transport chain whcin include nonprotein parts parts containing iron

Front 8

Phosphorylation

Back 8

4th step in noncyclic photo... as the two electrons move down the electon transport chain, they lose energy. The energy lost is used to phosphorylate, on average, about 1.5 ATP molecules

Front 9

Photosystem I

Back 9

5th step in noncyclic photo... gthe electron transport chain terminates with PS I (with P700). Here the electrons are again energized by sunlight and passed to a primary electron acceptor (different from the one associated with PS II)

Front 10

NADPH

Back 10

6th step in noncyclic photo... the two electrons pass through a short electron transport chain, and at the end the two electrons combine with NADP+ and H+ to form NADPH. It is a coenzyme, and since the electrons have a considerable amount of energy left, NADPH is an energy-rich molecule

Front 11

Photolysis

Back 11

7th step in noncyclic photo.. the two electrons from PSII are now in NADPH. The loss of these two electrons is replaced when water splits into 2H+ and .5 O2. This literally means decomposition by light and a manganese-containing protein complex catalyzes the reaction. THe two electrons replace the lost electrons and one of the H+ provides the H in NADPH.

Front 12

Light-Dependent Reactions equation

Back 12

H2O+ADP+Pi+NADP+ +light -> ATP + NADPH + O2 +H+

Front 13

Cyclic Photophosphorylation

Back 13

A second photophos. sequence that occurs when electrons energized in PSI are "Recycled". In this, the energized electrons join with protein carriers and generate ATP as they pass along the electron transport chin. They do not create NADPH but rather the electrons return to PSI to be energized again. It is a primitive form of photosynthesis but occurs simultaneously with noncyclic photophos.

Front 14

Calvin-Benson Cycle

Back 14

"fixes" CO2 to create a single molecule of glucose, and it must repeat 6 times and use 6 CO2 molecules

Front 15

Carboxylation

Back 15

6CO2 combine with 6RuBP to produce 12 PGA. The enzyne ReBP carboxylase, or rubisco, catalyzes the merging of CO2 and ribulose biphosphate. It is referred to as C2 photosynt. because the first product formed, Phosphoglycerate (PGA) contains three carbon atoms. It is also called the carbon reduction cycle

Front 16

Reduction

Back 16

12 ATP and 12 NADPH are used to convert 12 PGA to 12 PGAL, the erngy is incorported into PGAL (glyceride 3-phosphate) thus making PGAL a very rich energy molecule. ADP, Pi, NADP+ are released and then re-energized in noncylcic photophos. ( calvin cycle)

Front 17

Regeneration

Back 17

6 ATP are used to convert 10 PGAL to 6 RuBP, allows the calvin cycle to repeat

Front 18

Carbohydrate synthesis

Back 18

last step of calvin cycle, the remaining two PGAL are used to build glucose and other monosaccarides.

Front 19

light-independent/ dark reactions

Back 19

another name of the calvin-benson cycle because no light is used, but it cannot occur in the dark because it is dependent upon the enrgy from ATP and NADPH whcih can be created only from light-dependent photophosphorylation

Front 20

Calvin Cycle Equation

Back 20

takes CO2 from atomosphere and energy in ATP and NADPH to create a glucose molecule
6CO2 +18 ATP +12 NADPH + H+ -> 18 ADP + 18 Pi + 12 NADP+ + 1 Glucose

Front 21

Chloroplasts

Back 21

the sites where both the light-dependent and light-independent reactons of photosynthesis occur

Front 22

Stroma

Back 22

the fluid that is enclosed in the chloroplast's outside phospholipid bilayer membrane, enzymes are here for the Calvin Bension Cycle so this is where dark reactions occur

Front 23

Thlakoids

Back 23

individual membrane layers (the pancakes) that are in suspended stacks in the chloroplast's stroma. WIthin it are light-absorbing pigments and enzymes for the light-dependent reactions. Light reactions occur on these membranes

Front 24

Granum, Grana

Back 24

A stack of thylakoids in a chloroplast

Front 25

Chemiosmotic Theory

Back 25

describes the mechanism by which ADP is phosphorylated into ATP

Front 26

First Step of the Chemiosmotic Theory

Back 26

H+ ions (protons) accumulate inside thylakoids, photolysis creats H+'s inside the thylakoids and oxygen to the outside, and H+ accompanies the electrons as they pass along the electron chain between PSII and PSI, these protons come from the stroma and are released to the inside of the thylakoids

Front 27

Second Step of the Chemiosmotic Theory

Back 27

A pH and electrical gradient across the thylakoid membrane is created, as H+ accumalate inside the thylakoid, pH dereases. This creates a pH gradient where the stroma is an 8 and teh thylakoid is 5, so there is an electric gradient/coltage on the inside of the thylakoid

Front 28

Third Step in the Chemiosmotic Theory

Back 28

ATP syntases generate ATP, the pH and electrical grandient represent potential energy like water behind a dam. Channel proteins/ATP synthases, allow the H+ to pass through the thylakoid and out into the stroma, which generates energy for the ATP synthases to phosphorylate AFP to ATP. The passage of THREE H+'s i sneeded to make one ATP

Front 29

Channel Proteins

Back 29

ATP Synthases in the last step of the Chemiosmotic Theory

Front 30

Rubisco

Back 30

the most common protein found on earth

Front 31

Photorespiration

Back 31

the biosynthetic pathway that leads to the fixation of oxygen, but it leads to two problems, first is that the CO@ fixing effiecienty is reduced because rubisco will fix O2 as well and that products formed from O2 do not create energy rich molecules.

Front 32

Peroxisomes

Back 32

specialized cellular oraganelles found near chloroplasts where they function to break down photorespiration produces

Front 33

Peroxisomes

Back 33

specialized cellular oraganelles found near chloroplasts where they function to break down photorespiration produces

Front 34

C4 Photosynthesis

Back 34

To improve photosynthetic efficiency, and instead of CO2 being fixed by rubisco, it combines with PEP to form OAA, then turns into malate, and is shuttled to the bundle sheath cells where they become pyruvate and CO2 which improves the efficiency.

Front 35

PEP

Back 35

phosphoenolpyruvate, the first thing CO2 combines with in C4 photosynthesis to form OAA

Front 36

OAA

Back 36

oxaloacetate or oxaloacetic acid, the first product of the C4 pathway, it is then converted to malate

Front 37

PEP Carbolxylase

Back 37

fixing enzyme of PEP and OAA in C4 photosynthesis

Front 38

Malate

Back 38

formed from OAA during C4 photosynthesis and is then shuttled to the bundle sheath cells where it is converted to pyruvate and CO2

Front 39

Pyruvate and CO2

Back 39

resultants of malate in the bundle sheath cells during C4 photosynthesis, and the pyruvate goes back to the mesophyll cell where one ATP braks into AMP to convert the pyruvate back into PEP. Then the process repeats

Front 40

Efficieny of C4 photosynthesis

Back 40

moving C02 to bundle sheath cells helps start the calvin-benson cycle, because little oxygen is present, rubisco can fix CO2 without competition from O2, so little photorespiration takes place, the stomate doesnt have to be open long so water doesnt escape, so they are found in hot, dry climates and sugarcane and crab grass are examples

Front 41

CAM Photosynthesis

Back 41

Crassulacean Acid Metabolism, just like C4 photosynthesis but instead of malate, OAA is converted to malic acid, which is then shuttled to the VACUOLE of the cell. And stomata are open at night so malic acid accumalates, then the stomata are closed during the day (opposite) and malic acid is converted back to OAA, relaeasing CO2 for the calvin cycle

Front 42

efficiency of CAM photosynthesis

Back 42

photosynthesis can proceed during the day while stomate are closed, reducing water loss. This is found mostly in hot areas with cool nights, like deserts, and is found amoung the Crassulaceae family, and as well as CACTI