BIOLOGY UNIT 3 SAC 2

photosynthesis + cellular respiration

photosynthesis + purpose

a process where plants convert light energy into chemical energy stored in glucose

• 6CO2 + 6H2O —> ( sunlight + chlorophyll) C6H12O6 + 6O2

photosynthesis: anabolic or catabolic?

photosynthesis is an anabolic reaction as it builds complex molecules (glucose) from simpler molecules (carbon dioxide and oxygen)

2 jobs of chlorophyll

1. absorb sunlight energy (chlorophyll on thylakoid membrane)

2. convert inorganic CO2 + H2O into organic C6H12O6

chlorophyll a vs chlorophyll b

a (main pigment) - blue and red

b (accessory pigment) - blue

stroma

light independent stage

thylakoid

captures light energy

grana

light dependent stage + photolysis

light dependent stage

LOCATION: grana/thylakoid

INPUTS:

12 H2O

12 NADP+

18 ATP

OUTPUTS:

6 O2

12 NADPH

18 ATP

light independent stage

LOCATION: stroma

INPUTS:

6 CO2

12 NADPH

18 ATP

OUTPUTS:

C612O2

12NADP+

18 ADP+Pi

6H2O

light

provides energy for light dependent stage + photolysis

water

• split via photolysis

• H+ used to load coenzymes

• O2 is waste

NADP+

• electron acceptor

• can load H+ ions used for LI stage

• unloaded: LD —> NADPH IN LI

ADP+Pi

converted to ATP via energy transfer

• unloaded: LD —> ATP IN LI

ATP

• energy storage

• transport to convert CO2 into C6H12O6 in LI

CO2

inorganic CO2 —> converted via carbon fixation (rubisco) into organic C6H12O6

oxygen

waste product of LD stage

carbon fixation + why occur

enzyme rubisco converts inorganic CO2 into organic C6H12O6 to be used by cell/organism

• occurs in stroma of chloroplast (LI)

molecule that NADPH carries

H+ atoms and high energy electrons

role of NADPH in LI stage

• electron carrier

• unloads H+ ions to help convert CO2 to C6H12O6 in LI stage

role of ATP in LI stage

energy storage + transport to convert CO2 into C6H12O6 in LI stage

role of rubisco in photosynthesis of C3 plants

binds to inorganic CO2 from the atmosphere to convert/fixate into organic C6H12O6

where is rubisco found in chloroplast + why

• found in the stroma

• assists in LI stage (calvin cycle)

• catalyses first reaction in cc

molecules that can bind to rubisco

CO2 + O2

photorespiration + why wasteful to plants

occurs when rubisco binds to O2 instead of CO2

• forms a product which cannot be used to form glucose

• not an efficient pathway + wastes energy

what happens when a plant undergoes photorespiration

• if stomata is closed (to save water on hot day - C3 plants)

• more O2 in the atmosphere than CO2 (limited)

C3 plants

• most plants (wheat or rice)

• temp preference: 15-30 degrees

• separation of ps processes: mesophyll only

• location: moderate, cool and wet environment

• when stomata close: photorespiration

C4 plants

• corn or sugarcane

• temp preference: 30-40 degrees

• separation of ps process: between cells of mesophyll — bundle sheath cells

• location: hot and sunny

• when somata close: calvin cycle

CAM plants

• cactus and pineapple

• temp: 15-25 degrees to fixate carbon but have adaptions to survive hot temp.

• separation of ps process: night vs day (mesophyll cells)

• location: very hot, desert and dry

• when stomata close: calvin cycle

difference between C4 and CAM

C4:

• fixates carbon in

• mesophyll —> bundle sheath

• stomata activity depends on temperature

CAM:

• fixate carbon in

• mesophyll only

• stomata activity depends on time of day

strategy of C4 plants when stomata is closed to ensure glucose is still produced using calvin cycle by the cell

1. CO2 enters mesophyll cells and fixed + converted into malate (4 carbon molecule)

2. malate transported to bundle sheath cell to release CO2

3. calvin cycle —> glucose

4. Pyruvate formed (3 carbon) transported back to form malate

strategy of CAM plants to overcome hot weather

1. stomata open at night to let in CO2

2. CO2 is fixated + converted to malate (4C) and stored in mesophyll cell vacuole

3. during day, stomata closes to prevent water loss

   • malate transported out of vacuole and broken down to release CO2 —> calvin cycle —> glucose

factors that impact photosynthesis: amount of water

• reactant for photolysis + source of H+ ions

• influence opening/closing of stomata (C3/C4 plants)

factors that impact photosynthesis: amount of sunlight

affects rate of photolysis

• splitting of water

• production of H+ ions to load coenzymes

factors that impact photosynthesis: amount of CO2

• reactant for calvin cycle

• less CO2 —> more O2 —> more photorespiration

factors that impact photosynthesis: temperature

• increase rate of reaction (kinetic energy)

• affects stomata activity

aerobic respiration

create large amounts of useable energy (ATP) for the cell

• C6H12O6 + 6O2 —> 6O2 + 6H2O + 30-32 ATP

cellular respiration: catabolic or anabolic?

catabolic as it breaks down glucose into smaller components to produce ATP

where does aerobic respiration occur

cytosol + mitochondria

aerobic respiration: glycolysis

LOCATION: cytosol

INPUTS:

• 1 glucose C6H12O6

• 2 ADP+Pi

• 2 NAD+, 2 H+

OUTPUTS:

• 2 pyruvate

• 2 ATP

• 2 NADH

aerobic respiration: krebs cycle

LOCATION: mitochondrial matrix

INPUTS:

• 2 acetyl-coa

  • 2 pyruvate

• 2 ADP+Pi

• 6 NAD

• 2 FAD

OUTPUTS:

• 4 CO2

• 2 ATP

• 6 NADH

• 2 FADH2

aerobic respiration: electron transport chain

LOCATION: mitochondrial cristae

INPUTS:

• 26-28 ADP+Pi

• 10 NADH

• 2 FADH2

• 6 O2

OUTPUTS:

• 26-28 ATP

• 10 NAD+

• 2 FAD

• 6 H2O

role of NADH, FADH2 and oxygen in the electron transport chain

• transfers electrons and H+ to cytochromes in cristae to create proton gradient —> used to power ATP synthase to produce ATP from ADP+Pi

• oxygen is an electron acceptor

  • turns into H2O

final electron acceptor and what happens to it

oxygen is electron acceptor

• turns into H2O

anaerobic respiration + occur

occurs in the absence of O2

• still able to create ATP from glucose

• occurs in cytosol —> glycolysis only

benefit of anaerobic respiration

• happens without oxygen to generate small amounts of ATP

• faster ATP production

aerobic + anaerobic (animal) + anaerobic (in yeast)

oxygen: Y, N and N

number + name steps: 3 glycolysis, krebs and etc — 1 glycolysis (lactic acid fermentation) — 1 glycolysis (ethanol fermentation)

complete break down of glucose: Y, N and N

inputs: glucose + O2 — glucose only — glucose only

outputs: 30-32 ATP, CO2, H2O — lactic acid + 2 ATP — ethanol, CO2 + 2 ATP

rate: slow, fast, fast

ATP yield: 30-32 ATP, 2 ATP and 2 ATP

location: cytosol + mitochondria, cytosol, cytosol

aerobic lactic acid examples

• vigorous exercise

• limited oxygen (poor circulated rooms)

anaerobic yeast examples

• beer/wine fermentation

• bread making

2 factors that affect cellular respiration

glucose availability:

• input for glycolysis

• more glucose —> more reactant

oxygen conc:

• input for ETC

• accepts H+

• determines if one or aero pathway

bio fuels

liquid or gaseous fuels created from fermentation of organic materials (biomass)

advantages of using biofuels over traditional fuels

• reduces carbon footprint + effects of greenhouse gas/climate change

how does bio uel work

collection of feedstock/biomass —> processing (mechanical breakdown) —> hydrolysis —> fermentation (chemical breakdown) + distillation —> storage

reliability

consistency + responsibility of an experiment results

• if experiment is repeated —> similar results are produced

how to improve reliability

• replication of experiment

• control all variables —> clean/consistent equipment —> precision

continuous

measurable value

discrete

countable and distinct valuable