Chap 10: Photosythesis Flashcards
Photosynthesis
Occurs in plants, algae, certain other protists, & some other prokaryotes
The ability to use sunlight to combine CO2 & H2O to make food
Redox process in which H2O is oxidized and CO2 is reduced
Heterotrophs
Get their food from eating others
Eat food energy other organisms+organic molecules
Make energy directly through respiration
Glucose + Oxygen—> CO2+ H2O+ ATp
Autotrophs
Produce their own energy
Convert energy of sunlight
Build organic molecules (CHO) fromCO2
Make energy & synthesize sugars through photosynthesis
CO2 + H2O + light energy —> glucose + oxygen
What does it mean to be a plant?
Collect light energy
- transform it into chemical energy
Store light energy
-in a stable form to be moved around the plant or stored
Need to get building block elements from the environment
- C, H, O, N, P, K, S, Mg
Produce all organic molecules needed to growth
- carbs, proteins, lipids, nuclei acid
What parts of the plant obtains raw materials ?
Sunlight: Leaves: solar collectors
CO2: stomates: gas exchange
H2O: uptake from roots
Nutrients: N, P, Fe etc. : uptake from roots
Chlorplasts
Double membrane
Stroma
- fluid-filled interior
thylakoid sacs
grana stacks
Splits H2O into hydrogen and oxygen, incorporating the electrons of hydrogen into sugar molecules
Structurally similar to and likely evolved from photosynthetic bacteria
The structural organization allows chemical reactions of photosynthesis
What does the thylakoid membrane contains ?
Chlorophyll molecules
Electron transport chain
ATP synthase
What are the 2 parts of photosynthesis?
Light reactions(photo part)
Calvin Cycle(the synthesis part)
Light Reactions
In the thylakoids
- split H2O
-Release O2
-Reduce NADP+ to NADPH
-Generate ATP from ADP by photophosphorylation
Calvin Cycle
Forms sugar from CO2, using ATP and NADPH
Begins w/ carbon fixation, incorporating CO2 into organic molecules
Light
A form of electromagnetic energy a.k.a electromagnetic radiation
Travels in rhythmic waves
Wavelength
Distance b/tw crests of waves
Determines the type of electromagnetic energy
Photosynthetic Pigment
substances that absorb visible light
different pigment absorbs different wavelengths of light
wavelength that are not absorbed are reflected or transmitted
leaves appear green b/c chlorphyll reflects and transmitts
Spectrophotometer
measures a pigments ability
What did Theodor W. Englelmenn 1st demonstrate?
the action spectrum of photosynthesis
How did Theodor demonstrate the action spectrum of photosynthesis?
He exposed different segments of filamentous alga to different wavelengths
areas that received wavelengths favorable to photosynthesis produced excess O2
used the growth of aerobic bacteria cluster along the alga as a measure of O2 production
What is the main photosynthetic pigment?
chlorophyll a
What do accessory pigments do for plants?
Broadens the spectrum used for photosynthesis
Carotenoids
accessory pigment excessive light that would damage chlorophyll
What happens to a pigment that absorb light?
The pigment goes from a ground state to an excited state, which is unsable
What is the role of sunlight?
moves the electrons, runs the pumps , pumps the proton, builds the gradient, drives the flow of protons through the ATP synthase, bonds P to ADP, generates the ATP
Where are the pigments found?
embedded in the thylakoid membrane
How are pigments arranged?
in a photosystem, collection of molecules
What does chlorophyll a absorb the best & the worst?
Best: red & blue wavelengths
Worse: green wavelenghs
How many photosystems are in thylakoid membranes
2
Photosystem II
chlorophyll a , absorbs 680 nm, wavelengths red light
Photosystem I
chlorophyll b, absorbs 700, wavelengths red light
What happens when the PS II absorbs light ?
excited electrons passes through the chlorophyll to “primary electron acceptor”
need to replace the electron in chlorophyll
enzymes extracts electrons fromH2O & supplies them to chlorophyll
- splits H2O
-O combines w/ another O creating O2
-O2 is release to the atmosphere
What does the EC produce w/ light energy
ATP & NADPH
Cyclic photophosphorylation
If PS I can’t pass electron to NADP…it cycles back to PS II & makes more ATP, but no NADPH
coordinates light reactions to Calvin cycle
Calvin cycle uses more ATP than NADPH
Noncyclic Photophosphorylation
Light reactions elevate electrons in
2 steps (PS II & PS I)
-PS II generates energy as ATP
- PS I generate reducing power as NADPH
Calvin Cycle
Occurs in stroma
The ATP and NADPH made in light reactions are used to power the process of carbon fixation
CO2 combines with 5C ribulose biphosphate (RuBP) to make a very unstable 6C compound which splits immediately into 2 3C G3P.
For every 1 CO2 which enters the Calvin cycle, 1 G3P molecule is created.
After 3 CO2 enter into the Calvin cycle (and 3 “turns” of the Calvin Cycle), 2 G3P molecules will be made.
The G3P that leaves will be reduced to glucose
The 5CO2 that stay in the Calvin cycle are rearranged using ATP to reconstruct RuBP
