Week 3

Question 1

what are the energy states in ATP?

Answer 1

adenosine triphosphate –> highest G state

adenosine diphosphate –> middle G state

adenosine monophosphate –> lowest G state

Question 2

how does ATP store energy?

Answer 2

a lot of free energy stored in the bonds connecting the phosphate groups

Question 3

describe the ATP cycle:

Answer 3

ATP synthesis is endergonic

ATP hydrolysis is exergonic

Question 4

describe difference b/n kinetics and thermodynamics

Answer 4

kinetics == rate at which reaction occurs

thermodynamics == whether energy Is released or absorbed by the reaction
- TDs say nothing about rates of reaction

Question 5

rate of reaction is dependent on…

Answer 5

activation energy

Question 6

activation energy is…

Answer 6

the amount of G required to start a chemical reaction

Question 7

reactions with high AE == ___ rate of rxn

reactions with low AE == ___ rate of rxn

Answer 7

high AE == low rate of rxn

low AE == high rate of rxn

Question 8

what are the 2 components of AE?

Answer 8

collision energy of reactants

orientation of reactants during collisions

Question 9

how catalysts affect activation energy and rate of rxn?

Answer 9

lower AE and increase rate of rxn

Question 10

what are enzymes?

Answer 10

biological catalysts that can

1) hold reactants in favorable orientations

2) stress the chemical bonds of reactants

Question 11

why are redox reactions important?

Answer 11

a chain of redox reactions result in a “flow” of electrons called an electron transport chain (ETC)

Question 12

what are electron carriers?

Answer 12

molecules and enzymes that make up the ETC

accept electrons (become reduced) and donate electrons (become oxidized)

Question 13

describe affinity of electron carriers for electrons

Answer 13

the first EC in the ETC has the lowest affinity for electrons

the last EC in the ETC has the highest affinity for electrons

Question 14

what occurs during photosynthesis?

Answer 14

light powers the production of glucose

Question 15

how efficient is photosynthesis?

Answer 15

efficiency of energy transfer is low (30%)

30% of photon energy ends up stored as chemical energy (glucose)

Question 16

where does photosynthesis occur?

Answer 16

chloroplast of plant cell

Question 17

describe importance of chloroplast structure

Answer 17

thylakoid membranes
- contain the pigments (chlorophylls) that capture photon energy

stroma
- contains enzymes for sugar manufacturing

Question 18

what are the 2 parts to photosynthesis?

Answer 18

light reactions

dark reactions

Question 19

light reactions:

• where do they occur?
• what do they require?
• what do they produce?

Answer 19

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

Question 20

dark reactions AKA ___

• where do is occur?
• what does it require?
• what does it produce?

Answer 20

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)

Question 21

describe the steps of photon capture in a single photosystem

Answer 21

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

Question 22

where does PS2 get its replacement electrons?

where does PS1 gets its replacement electrons?

Answer 22

from H2O

from PS2

Question 23

when electrons reach PS1, what happens to their energy?

what happens to the energy?

Answer 23

they have lost their energy

energy stored in the electrons is used to power a H+ pump –> creates a proton gradient across the membrane

Question 24

what happens as electrons are transferred across the ETC from PS2 to PS1?

Answer 24

the energy is used to power a proton pump that pumps H+ from the stroma into the thylakoid membrane

Question 25

how do the light reactions make ATP?

Answer 25

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

Question 26

how is NADPH made in the light reactions?

Answer 26

photon energy from light is used to re-energize the electrons in PS1

the re-energised electron is used to reduce NADP+ to NADPH

Question 27

the flow of protons across the membrane to generate ATP is called ___

Answer 27

chemiosmosis