Lecture 8 - Chapter 8

Plants take in Water, CO2, and light energy and use it to synthesize carbohydrates

6(CO2) + 12(H2 O) + light energy ---> (C6 H12 O6) + 6O2 + 6H2O

+685 kCal/mol. This makes it an endergonic reaction.

CO2 is reduced(gaining electrons) and H2O is oxidized(loosing electrons)

Endergonic - non spontaneous and energy is created.

Biosphere

Regions on the surface of the earth and in the atmosphere where living organisms exist

Heterotroph and Autotroph

Must take in organic molecules from the environment to sustain life. (animals)

Makes organic molecules from inorganic sources. Sub set of this is Photoautotroph.

Something that uses light as a source of energy

Hard part in the center of a leaf. Organelles in plants and algea that carry out photosynthesis.

Chlorophyll - the stuff responsible for the green pigment

The internal part of the leaf with cells containing chloroplast. This is where photosynthesis occurs. This is a big area.

Pores in the surface of leaf where carbon dioxide enters and oxygen exits.

3 layers

3rd membrane layer. It contains the pigment molecules.

A stack of thylakoids

Fluid filled region between thylakoid membrane and inner membrane.

Light reaction and the Calvin Cycle

Light energy comes into the thylakoid membrane. Produces ATP, NADPH, and 02.

Occurs in stroma. Uses ATP and NADPH to incorporate CO2 into organic molecules.

Energy in electric and magnetic fields.

In waves that have oscillations of electric and magnetic fields.

High energy

Low energy

absorb some light energy and reflect others.

They reflect green wavelengths and absorb the other colors.

It boosts electrons to a higher energy level.

The amount of energy needed to boost an electron to a higher orbital.

it is in an excited state and is usually unstable.

As light or heat

Chlorophyll a and chlorophyll b

yellows to reds in flowers

captured light energy that can be transferred to other molecules to produce energy intermeditaes

protein complexes and pigment.

Photosystem (I) - discovered first. .

Photosystem(II) - occurs first

Light excites the pigment molecules

Excited electrons travel to PSI

- water is oxidized generating O2 and H+- Release of electrons into the transport chain- energy used to make H+ electrochemical gradient

NADPH is made by the addition of H+ through the electrochemical gradient

There is an H+ gradient created by 3 things that is pushing H+ through the ETC using ATP Synthase. .

1. H+ in thylakoid lumen by splitting water.

2. H+ by ECT pumping H+ into lumen.

3. H+ from formation of NADPH in stroma

1. Chemiosmotic(relating to the movement of ions across a semipermeable membrane).

2. Driven by flow of H+ from thylakoid lumen into stroma via ATP synthase.

Electrons begin at PSII and eventually transfer to NADPH. Linear process produces ATP and NADPH in equal amounts.

PSI

1. Light excites electrons in PSI.

2. High energy electrons sent to ferrodoxin.

3. Cyclic electron flow favored when NADPH level is high

1. Electrons begin at PSII and eventually transfer to NADPH.

2. Linear process produces ATP and NADDPH in equal amounts.

ATP and NADPH are used to make Carbohydrates

1. Carbon from atmospheric CO2 is incorporated into carbohydrates.

2. Precursors to all organic molecules.

3. Energy is stored.

18 ATP and 12 NADPH

Glyceraldehyde-3-phosphate (G3P) is formed as starting materials for the formation of sugars. Glucose is not made directly, but this is where it is going.

Starch polymers

1. It is stored in chloroplast for later use.

2. Transported from leaf to other parts of the plant.

1. Carbon fixation.

2. Reduction and carbohydrate production.

3. Regeneration of RuBP

1. CO2 is incorporated into RuBP(5-Carbon Sugar) to form a 6-Carbon intermediate.

2. as soon as this is made it is immediately catalyzed by Rubisco.

3. 6 carbon intermediate splits into 2 3PG

1. ATP is used to convert 3PG into 1,3-BPG.

2. NADPH electrons reduce it to G3P.

3. 12 G3P molecules produced in phase 2.

1. 10 G3P converted into 6 RuBP using 6 ATP.

2. Regenerated RuBP molecules serve as acceptors for CO2. This allows for the cycle to continue.

Light intensity, temperature, and water availability.

a respiratory process in many higher plants by which they take up oxygen in the light and give out some carbon dioxide, contrary to the general pattern of photosynthesis.

Hot and Dry environments

Enzyme Rubisco functions as a carboxylase.

RuBP + CO2 ---> 2 3PG (3_carbon molecules)

It uses O2 and liberates CO2. This is wasteful and reverses the effects of Photosynthesis.

an Oxygenase.

O2 levels are high and CO2 levels are low.

CO2 enters via stomata and a 4 carbon compound is formed. Goes to the bundle-sheath cells

The 4 carbon made from the mesophyllc ells are transferred and release CO2