What were the earliest life forms?

Hetertrophs

What are hetertrophs?

Life forms that depend on an external source of organic compounds

How were hetertrophs formed?

Abiotically

What are autotrophs?

Life forms that produce their own organic nutrients from the simplest inorganic molecules such as CO2 and H2S.

Which life forms' appearance tremendously boosted the evolution of life?

Autotrophs

What are chemoautotrophs?

Life forms that use energy stored in inorganic compounds (H2S, NH3, etc.)

What is a photoautotroph

Life forms that use the radiant energy from the sun.

Why do photoautotrophs need more energy?

Because the oxygen atom has a stronger affinity for electrons.

______ provide the most of organic nutrients for the lives on the planet.

Photosynthetic plants.

What are the membranes of chloroplast?

-Outer -Inner -Internal

What is found in the outer membrane of a chloroplast envelope?

Contains porins; integral proteins that exhibit selective permeability towards various solutes.

The inner membrane is highly _____.

Impermeable.

What is in the internal membrane of chloroplast?

-Thylakoids -Stroma

What are thylakoids?

Flattened membranous sacs where the light dependent reactions take place.

What is the space inside a thylakoid sac called?

The lumen

What is the space outside of the thylakoid within the chloroplast envelope/inner membrane?

The stroma

What are grana?

The orderly stacks structures.

What is the space located in the outer membrane of the chloroplast?

Intermembrane space.

What kind of DNA is present in the chloroplast's stroma?

Small, double stranded, circular DNA

How many genes can chloroplast contain?

60-200.

What are the majority of chloroplast proteins encoded by?

Nuclear DNA.

How are chloroplast reproduced?

By fission from preexisting chloroplasts or proplastids

What are proplastids?

Chloroplast's nonpigmented precursors.

What is the order of reactions in photosynthetic metabolism?

1.CO2 + H2S to CH2O + S2 2.CO2 + H2A to CH2O + S2 3.CO2 + H2O to CH2O + O2

____ splits up H2O.

Light energy,

What is derived from H2O?

O2

In the Samuel Ruben experiment, wjat were the two different test of replacing isotope O 16?

1. Labeled C[18-O2] and unlabeled H2O 2. Unlabeled CO2 and labeled H2[18-O2]

Photosynthesis in chloroplast is essentially the reverse of _______.

Mitochondrial respiration.

What is light-dependent reactions?

Energy from sunlight is absorbed and stored as ATP and NADPH

What is light-independent (dark) reactions?

The energy from ATP and NADPH is used to synthesize carbohydrates from CO2.

What is the equation for energy content of a photon?

Energy = h*c/wavelength

What a photon absorbs enough energy it goes from _____ to ______.

Ground state; excited state

How do photons in an excited state go back into the ground state for chloroplasts?

Primary electron acceptors

What organisms have chlorophyll a?

All oxygen-producing organisms

What organisms have chlorophyll b?

All higher plants and algae

What organisms have chlorophyll c?

-Brown algae -Diatoms -Protozoa

What organisms have chlorophyll d?

Red algae

What organisms have bacteriochlorophyll?

-Green bacteria -Purple bacteria

What visible wavelengths does chlorophyll absorb?

Red and blue

What visible wavelengths does chlorophyll reflect?

Green

What are the primary photosynthetic pigments?

Chlorophyll

What visible wavelengths does carotenoids absorb?

Blue and green

What visible wavelengths does carotenoids reflect?

Yellow, orange, red

What are secondary pigments/secondary light collectors?

Carotenoids

What functions do carotenoids perform?

-Secondary light collectors -Draws excess energy away from excited chlorophyll -Produced heat from excess energy -Prevents formation of singlet oxygen

What is the structure of a chlorophyll?

-A porphyrin ring with conjugated double bonds -A hydrophobic phytol chain

What does the porphyrin ring in chlorophyll do?

Absorbs light

What does the hydrophobic phytol chain in chlorophyll do?

Keeps chlorophyll embedded in the photosynthetic membrane.

What is the chemical structure of beta-carotene?

A linear system of conjugated double bonds

What was found during the experiment of using green algae suspension and flashing light for short durations?

-1 molecule of oxygen was released for every 2500 molecules of chlorophyll present -A minimum of 8 photons must be absorbed to produce 1 molecule of O2.

Why do chloroplast contain 300x more chlorophyll molecules than is necessary to oxidize water for O2 production?

1. Only a small percentage of chlorophyll is involved in photosynthesis 2. Several 100s of chlorophyll act together as 1 photosynthetic unit and only 1 chlorophyll is capable of transferring electrons to an electron acceptor.

What is the reaction center?

The chlorophyll in the photosynthetic unit that transfer electrons to electron receptors.

What is the antenna?

Absorbs photon of varying wavelengths and transfer excitation energy quickly to the reaction center.

How are the chlorophyll molecules of an antenna kept close together?

Non covalent linkage to integral proteins

Antenna pigments energy can only be transferred to _____.

Equal or less than energy-requiring molecule.

What is the standard reduction potential of 1/2O2 + 2H+ + 2e- = H20?

E knot= +0.816V

What is the standard reduction potential of NADP + 2H+ +2e- = NADPH + H+

E knot= -0.324V

One mole of photons of 680 nm is equivalent to ______.

Change in redox potential = 1.8V

It is possible to boost an electron to an energy level for ______.

Reducing NAPD+

How much energy needs to be absorbed to remove an electron from water and pass it NADP+?

+1.14V

What helps accomplish the combined action of 2 different light-absorbing reactions?

Photosystems 1 (P700) and 2 (P680)

What is the reaction center for photosystem 1?

Chlorophyll dimer P700

What is the reaction center for photosystem 2?

Chlorophyll dimer P680

What do two photosystems act like?

In series, electrons flow from: 1. water to PS2 2. PS2 to PS1 3. PS1 to NADP+

What is the Z scheme?

The series of events of electrons moving from H20 to NADP+

PS2 complex contains ______ peptides.

20 different

What is special of proteins D1 and D2?

They bind with P680 and the cofactors in the electron transport.

What is outside the core of the photosystem?

LHC 2

What is step 1 of electrons going from PS2 to plastoquinone?

Light energy from antenna goes to P680.

What is step 2 of electrons going from PS2 to plastoquinone?

P680 transfer a single photo-excited electron to a closely associated pheophytin molecule.

What is step 3 of electrons going from PS2 to plastoquinone?

P680+ and Pheo- are generated

What is step 4 of electrons going from PS2 to plastoquinone?

Pheo- transfers electrons to plastoquinone (PQA)

What is step 5 of electrons going from PS2 to plastoquinone?

PQA transfers electrons to a 2nd PQA (PQB) to produce a semireduced form of PQB that remains bounded to D1 protein.

What is step 6 of electrons going from PS2 to plastoquinone?

A second photo sends a second energized electron along the P680 path to form PQB-2

What is step 7 of electrons going from PS2 to plastoquinone?

PBQ-2 combines with 2 protons to form PQH2 that's reduced and dissociates from D1 and diffuses into the lipid bilayer

What is step 8 of electrons going from PS2 to plastoquinone?

The displaced PQH2 is replaced by a fully oxidized PQ derived from a small group of plastoquinone in the bilayer.

What is the redox potential of P680+?

+1.17V

What is photolysis?

The process of using light energy to split a water molecule

What is the S-state hypothesis?

A cluster of 4 manganese ions and 1 Ca+2 are stabilized and protected by an oxygen evolving complex made of 4 oxidizing equivalents that are sent to P680+ one at a time.

What mediates the electron transfer between Mn and P680+?

Tyrosine residue on the D1 protein.

What must happen before O2 can be released?

4 individual photoreactions accumulate.

What is step 1 of electrons going from PS2 to PS1?

2 molecules of PQH2 are formed by accepting 4 electrons from PS2 and combines with 4 protons from the stroma

What is step 2 of electrons going from PS2 to PS1?

PQH2 diffuses through lipid bilayer and binds to a large multiprotein complex (cytochrome b6f).

What is step 3 of electrons going from PS2 to PS1?

Electrons are transferred from cytochrome b6f to peripheral protein plastocyanin (PC).

What is step 4 of electrons going from PS2 to PS1?

PC transfers electrons to P700+/

What is step 1 of electrons going from PS1 to NADP+?

P700 transfers an electron to a separate monomeric chlorophyll a molecule (A0)

What is step 2 of electrons going from PS1 to NADP+?

From Chlorophyll A the electron moves to phylloquinone molecule.

What is step 3 of electrons going from PS1 to NADP+?

From phylloquinone electron goes to an iron-sulfur cluster (Fx)

What is step 4 of electrons from PS1 to NADP+?

From iron-sulfur complex electron goes to 2 other iron sulfur clusters Fb and Fa

What is step 5 of electrons from PS1 to NADP+?

From clusters Fb and Fa to a small, water-soluble iron-sulfur protein ferredoxin.

What is step 6 of electrons from PS1 to NADP+?

Reduction of NADP+ by ferredox-NADP+ reductase

What drives the proton-motive force in chloroplast?

A pH gradient.

What is cyclic phosphorylation?

A process that provides additional ATP for carbohydrate synthesis and other ATP-requiring activities in the chloroplast.

What component is responsible to cyclic phosphorylation?

Carried out by PS1.

What makes up a photosynthetic unit?

-reaction center chlorophyll -light-harvesting antenna

What was used to study Chlorella green algae suspension?

1. Long time radioactive isotope carbon 2. 2D paper chromatography

What gave organisms the name of C3 plants?

Because these plants use an intermediate of 3 carbon chain to fix CO2.

What is ribulose 1,5-biphosphate (RuBP)?

An initial acceptor

RuBP condenses with what to produced a 6-carbon molecule?

CO2

What does 6-carbon molecule break down into?

2 PGA molecules.

Where are the reactions of produced 6-carbon molecule and PGA happen?

The stroma

What carries out the production reactions of 6-carbon molecules that convert into PGA?

Ribulose biphosphate carboxylase (Rubisco).

Rubisco is a _____ enzyme, so its present in ______.

very low efficient; large amounts.

What are the 3 main parts of the Calvin Cycle?

1. Carboxylation of RuBP to form PGA 2. Reduction of PGA to Glyceraldehyde 3-phosphate (G3P) 3. Regeneration of RuBP

What is the net reaction process of the Calvin Cycle?

3CO2 + 9ATP + NADPH = G3P + 9ADP +8Pi +6NADP+

What is light activated electrons linked to?

Pumping of H+ into thylakoid disks.

What activates stromal Calvin Cycle enzymes?

Alkaline pH

What are the different Calvin Cycle enzymes?

-RuBP Carboxylase -Fructose-1,6- Biphosphatase -Sedoheptulose -Bisphosphatase

What counters the light activated H+ shift?

Mg++ releasing from thylakoids to the stroma.

What requires Mg++ to its active site?

RuBP Carboxylase

What molecule is prevalent in light and activating several Calvin Cycle enzymes?

Reduced thioredoxin

How does reduced thioredoxin activate enzymes?

By reducing specific disulfides in those enzymes to thiols.

What happens when Rubisco binds to RuBP?

It adopts the enediol form.

What can attack the enediol form of RuBP?

CO2 or O2

What determines the direction of the Rubisco catalyzed reaction?

The ratio of CO2/O2 available.

What are examples of C4 plants?

-sugarcane -corn -sorghum

What are C4 plants?

Organisms that follow the C4 pathway using combination of CO2 with PEP for 4 carbon compounds.

What is the typical environment of C4 plants?

Hoy and dry.

What enzyme is responsible for the linkage of CO2 and PEP as well as fixing CO2 with closed stomata?

PEP carboxylase.

What are CAM plants?

C4 plants that separate the C4 and C3 pathways in time instead of segregating them.