Cellular energetics - Pt. 1

Photosynthesis

simplified equation of photosynthesis

H₂O + CO₂ + light → O₂ + glucose + H₂O

Enzymes

made up of proteins that acts as a catalyst - does not get consumed

sometimes needs ATP

do not change the free energy

active site

lock and key: where catalysis occurs - substrates binding exactly

induced fit: substrates bind and active site changes shape

conditions

pH: optimal 6-8

temperature: higher temp speeds up reactions but too hot will denature proteins

cofactors: non proteins helpers for catalytic activity (organic = coenzymes)

concentration of substrate and concentration of enzyme

inhibitors

competitive and non competitive, substances that decrease enzyme activity

competitive inhibition

looks simialr to the substrate

binds to active site

no reaction takes place because active site taken up

non-competitive inhibiton

binds to allosteric site (away from active site) and changes shape to change function and stop enzyme from working

forms of energy

kinetic: motion

heat/thermal: random movement of atoms or molecules

potential: location/structure

chemical: to release in reaction

laws of thermodynamics

1st: energy cannot be created or destroyed

2nd: every energy transfer increases the entropy

endergonic vs exergonic reactions

ender: energy absorbed

exer: energy released

ATP

energy for cellular processes

ribose, adenine, 3 phosphates

unstable, stored when stable ADP (phosphorylation)

OILRIG

oxidation is lost, reduction is gained

chloroplast

thylakoid membrane: light dependent reactions, first stage of photosynthesis, have grana

stroma: light independent reactions, calvin cycle

pigment

absorbs light at a particular wavelength

chlorophyll, carotenoids, and phycobilins

stomata & transpiration

stomata: CO₂ enters, water vapor and O₂ leave

transpiration: plants lose H₂O from their leaves by evaporation

plants close stomata to conserve water but also closes off CO₂ and locks too much O₂ in

Autotroph

self nourishing, producers

Bundle sheath cells

cells tightly wrapped around veins of a leaf

site for calvin cycle in C₄ plants

C₄ plants

adapted plant to hot and dry conditions

mesophyll & mesophyll cells

mesophyll: interior tissue of leaf

mesophyll cells: contain many chloroplasts and host majority of photosynthesis

photosytems

photosystem II = P680

photosystem I = P700

light dependent reactions (noncyclic) - sequence of events

1. photon strikes PII

2. captured by primary electron acceptor

3. water split into 2H and O, electrons go to PII

4. travels through ETC, creates ATP through active transport w/ cytochrome protein pump

5. 5. photon strikes PI

6. 2 electrons reduce NADP⁺ to NADPH

photolysis

water is broken up into hydrogen ions and oxygen during light dependent reactions

photophosphorylation

ATP produced during light dependent reactions

chlorophyll a and chlorophyll b

a: major pigment, passes excited electrons to primary electron acceptor

b: accessory pigment

oxygen from plants

produced from the intake of water (H₂O), not CO₂

cyclic light reaction

no water split

no oxygen produced

no NADPH

still produces ATP

just uses PI and recycle electrons in ETC

hydrogen ion gradient

made by cytochrome, used to power ATP synthase

H⁺ move from stomata to thylakoid

light-independent reactions (calvin cycle)

occur in stomata

inputs: ATP and NADPH from light dependent, CO₂

outputs: sugar, ADP, NADP⁺

carbon fixation

carbon from CO₂ + RuBp to form 3-phosphoglycerate (3-PGA) through the enzyme Rubisco

photorespiration

Rubisco uses oxygen instead of CO_2, no sugar produced

happens on hot dry days when stomata is closed

oxaloacetate

instead of two 3PGA molecules, produces one 4 carbon molecule, oxaloacetate during carbon fixation for C₄ plants

CAM (Crassulacean acid metabolism)

water storing plants, desert plants

stomata open at night to avoid transpiration

Calvin cycle occurs during day when CO₂ is released