Photosynthesis & Cell resp.

two parts of photosynthesis

• light dependent

• light independent(calvin cycle)

where does light dependent reaction take place (in plants)

thylakoid membrane of chloroplasts

Photosystems

• large complexes of proteins & pigments

• pigments absorb E from sun & convert it to chem E

steps of light dependent reaction

1. E from sun energizes e- in photosystem 2 while hydrolysis occurs forming H+ ions, releasing e- & forming O₂

2. e- in photosystem 2 moves down chain releasing E as it goes to photo system 1 in process provides E to pump H+ ions across membrane → establish proton gradient

3. e- from photosystem 2 travels onwards and is passed to NADP+ to form NADPH

4. the proton gradient causes H+ ions to want to go back to other side but to do so they have to pass through ATP synthase which provides the E for synthesizing ATP (chemiosmosis)

what does calvin cycle (light independent reaction) do

synthesize sugars

where does calvin cycle take place

stroma

phases of the calvin cycle

1. carbon fixation

2. reduction

3. regeneration

carbon fixation

• CO₂ molecule combines with RuBP molecule

• forms unstable 6 carbon molecule

• unstable molecule splits into 2 3-phosphoglycerate (3-PGA) molecules

reduction

ATP & NADPH are used to convert 3-PGA molecules to G3P

regeneration

some of the new G3P molecules go on to make glucose while others are recycled

recycled G3P molecules are turned back into RuBP

for one G3P to exit 3 CO₂ must enter cycle when 3CO₂ enter the cycle 6 G3P are made one gets to leave and the rest are recycled

takes 6 cycles to make 1 glucose

what does cell resp do

convert glucose to energy

steps of cell resp

1. glycolysis

2. Pyruvate Oxidation (link reaction)

3. citric acid cycle (krebs cycle)

4. oxidative phosporylation (Electron transport chain)

glycolysis

glucose converted to 2 pyruvate

• small amount of ATP is made

• NAD+ converted to NADPH

• anaerobic

pyruvate oxidation aka link reaction

• pyruvates converted into acetyl CoA

• CO₂ released

• NADH generated

citric acid cycle (krebs cycle)

• regenerates 4 carbon starting molecule

• ATP NADH and FADH₂ produced and CO₂ is released

oxidative phosphorylation (Electron transport chain)

• the previously made NADH and FADH₂ deposit their electrons in e- transport chain & revert to original forms

• as electrons move down chain E is released & used to pump protons out of matrix→ concentration gradient

• protons flow back into matrix through ATP synthase

  • makes ATP

• at end of chain O accepts electrons and takes protons to form water

cell resp w/out air →

fermentation

fermentation

• glycolysis as normal

• e- transport chain doesn’t work so NADH can’t get rid of its electrons and turn back into NAD+

• 2 types of fermentation

  • lactic acid

  • ethanol (alcohol)

lactic acid fermentation

• NADH transports its elections to pyruvate

• lactic acid is formed as biproduct

• regenerates NAD+

alcohol fermentation

• carboxyl group removed from pyruvate & released as CO₂

• forms 2 acetaldehyde

• NADH drops off electrons produces alcohol

• NADH converted back to NAD+

thermoregulation

endothermic organisms can decouple the electron transport chain from ATP synthase to produce heat

uncoupling protein

• embeds in inner mitochondrial membrane & lets protons back into matrix

• cancels out work of ETC proton pumps

• decreases ATP produced → resp is exothermic to compensate