Week 6

chemiosmosis theory

high-energy intermediate powering ATP production is electrochemical proton gradient

ATP synthase

know how it rotates

note that The H+ enters, and neutralizes a carboxy group, when then allows the whole unit to rotate into the hydrophobic area of the membrane and At the end the carboxy group is reionized, and the H+ is lost

Engelmann experiment

Engelmann used prism to split light into its component colors and directed it onto a strand of Spirogyra (algae) under a microscope. He then introduced oxygen-seeking bacteria into the water. The bacteria clustered around regions of the algal strand exposed to blue and red light, where oxygen production was highest due to photosynthesis

Since bacteria move toward higher oxygen concentrations, this indicated that oxygen (a byproduct of photosynthesis) was produced only in the presence of certain light wavelengths.

Van niel experiment

Experiment by labeling the O in H2O in one and CO2 in another chloroplast revealed labelled O in H2O remains but CO2 is used up to produce oxygen

Chloroplasts have…

• Three membranes (outer, inner, thylakoid)

• Three spaces (intermembrane, stroma, thylakoid)

Photosystems are in thylakoid membrane to harvest light energy

Consists of antenna complexes to collect as much light as possible

Reaction center where light is converted to chemical energy

Photons hit pigments embedded in antennae complexes and each pigment absorbs different wavelengths of light

antenna complexes

lots of chl & pigment molecules arranged with proteins embedded in thylakoid membrane • energy from one chl* (excited by a photon of light) can move to a nearby chl molecule

Electrons in the pigments…

absorb the energy and reach a higher energy state. (energy released as heat, light, or given to nearby molecule)

reaction center has “special pair” of chlorophyll molecules

The special pair is situated between an electron acceptor and an electron donor in the reaction center

reaction center

where light energy converted to chemical energy, surrounded by antennae complexes funneling light to RC. Multiple antenna complexes make up photosystems embedded in thylakoid membrane (innermost membrane of chloroplast)

light dependent

photosystem I and II

light independent (calvin)

carbon fixation, reduction, regeneration

chloroplasts

inside is thylakoids which stacked are granum (multiple grana) and leftover space is stroma. inside thylakoid is chlorophyll

cyclic electron flow

feredoxin donates electrons to Q instead of complex that reduces NADP+ to NADPH so electrons recycled to pump H+, generating more ATP

mitochondria vs chloroplasts

Electron donor: pyruvate vs H2O

Electron acceptor: O2 vs NADP+

energy source: organic C vs light

how is energy harvested: ETC, GTP, ATP vs ETC, ATP, NADPH

inputs: pyruvate, O2 vs H2O, CO2

outputs: CO2, H2O, ATP vs sugars, O2

carbon fixation

• Calvin and Benson introduced radioactive carbon (C-14) into the atmosphere around green algae or plant cells in a controlled environment then exposed the plants to light and allowed them to photosynthesize

• Exposed plants harvested at diff time intervals

• used chromatography and radioactive tracing techniques to identify and track the radioactive carbon as it was incorporated into various molecules.

• discovered that the carbon dioxide was fixed into a 3-carbon compound known as 3-phosphoglycerate (3-PGA).

• They identified the intermediate compounds formed in the Calvin Cycle, such as ribulose bisphosphate (RuBP), glyceraldehyde-3-phosphate (G3P), and others.

rubisco

enzyme that catalyzes carbon fixation for light independent reaction BUT not efficient bc can accidentally use O2 instead of CO2; prevents this by being selective but slow process