Week 3 Flashcards
what are the energy states in ATP?
adenosine triphosphate –> highest G state
adenosine diphosphate –> middle G state
adenosine monophosphate –> lowest G state
how does ATP store energy?
a lot of free energy stored in the bonds connecting the phosphate groups
describe the ATP cycle:
ATP synthesis is endergonic
ATP hydrolysis is exergonic
describe difference b/n kinetics and thermodynamics
kinetics == rate at which reaction occurs
thermodynamics == whether energy Is released or absorbed by the reaction
- TDs say nothing about rates of reaction
rate of reaction is dependent on…
activation energy
activation energy is…
the amount of G required to start a chemical reaction
reactions with high AE == ___ rate of rxn
reactions with low AE == ___ rate of rxn
high AE == low rate of rxn
low AE == high rate of rxn
what are the 2 components of AE?
collision energy of reactants
orientation of reactants during collisions
how catalysts affect activation energy and rate of rxn?
lower AE and increase rate of rxn
what are enzymes?
biological catalysts that can
1) hold reactants in favorable orientations
2) stress the chemical bonds of reactants
why are redox reactions important?
a chain of redox reactions result in a “flow” of electrons called an electron transport chain (ETC)
what are electron carriers?
molecules and enzymes that make up the ETC
accept electrons (become reduced) and donate electrons (become oxidized)
describe affinity of electron carriers for electrons
the first EC in the ETC has the lowest affinity for electrons
the last EC in the ETC has the highest affinity for electrons
what occurs during photosynthesis?
light powers the production of glucose
how efficient is photosynthesis?
efficiency of energy transfer is low (30%)
30% of photon energy ends up stored as chemical energy (glucose)
where does photosynthesis occur?
chloroplast of plant cell
describe importance of chloroplast structure
thylakoid membranes
- contain the pigments (chlorophylls) that capture photon energy
stroma
- contains enzymes for sugar manufacturing
what are the 2 parts to photosynthesis?
light reactions
dark reactions
light reactions:
- where do they occur?
- what do they require?
- what do they produce?
occur at thylakoid membrane
requires:
- light as an energy source
- H2O as an electron source
produces:
- ATP (energy source)
- NADPH (electron carrier) (reduced form)
- O2 as a byproduct
dark reactions AKA ___
- where do is occur?
- what does it require?
- what does it produce?
Calvin benson cycle
occurs in stroma
requires:
- CO2 as a carbon source
- ATP (from light reactions) as an energy source
- NADPH (from light reactions) as an electron source
produces:
- glucose (energy storage molecule)
- ADP + Pi (from ATP hydrolysis)
- NADP+ (from oxidation of NADPH)
describe the steps of photon capture in a single photosystem
1) antenna chlorophylls capture photon energy
2) photon energy is radiated from antenna chlorophyll to antenna chlorophyll
3) finally, the energy is captured by the reaction center chlorophyll (RCC)
4) the energy is absorbed by an electron in the RCC
5) the energized electron is:
- ejected from the RCC
- captured by an electron carrier
- enters into an electron transport chain
6) the ejected electron is replaced
where does PS2 get its replacement electrons?
where does PS1 gets its replacement electrons?
from H2O
from PS2
when electrons reach PS1, what happens to their energy?
what happens to the energy?
they have lost their energy
energy stored in the electrons is used to power a H+ pump –> creates a proton gradient across the membrane
what happens as electrons are transferred across the ETC from PS2 to PS1?
the energy is used to power a proton pump that pumps H+ from the stroma into the thylakoid membrane
how do the light reactions make ATP?
the H+ that has accumulated in the thylakoid membrane then flows across ATP Synthase (enzyme/transport protein) back into the stroma
ATP Synthase uses the energy of H+ flow to make ATP
how is NADPH made in the light reactions?
photon energy from light is used to re-energize the electrons in PS1
the re-energised electron is used to reduce NADP+ to NADPH
the flow of protons across the membrane to generate ATP is called ___
chemiosmosis
