Week 3_dark reactions

Question 1

dark reactions require…

Answer 1

1) NADPH from light reactions

2) ATP from light reactions

3) CO2

Question 2

what are the 3 phases of the dark reactions?

Answer 2

1) carbon fixation

2) reduction of PGA

3) regeneration of RuBP

Question 3

what is carbon fixation?

Answer 3

1st phase of the dark reactions

converts inorganic CO2 into an organic form (PGA)

is catalyzed by the enzyme Rubisco

1 RuBP + 1 CO2 —(catalyzed by Rubisco) —-> 6-C molecule (unstable)

the 6-C compound immediately breaks down into two 3-C molecules (PGA)

1 6-C compound –> 2 PGA molecules

Question 4

what is reduction of PGA?

Answer 4

2nd phase of the dark reactions

adding electrons to PGA from NADPH

Question 5

what is regeneration of RuBP?

Answer 5

3rd phase of the dark reactions

RuBP is the CO2 acceptor –> binds to CO2 at the beginning of the dark reactions

Question 6

what is Rubisco?

Answer 6

the enzyme that catalyzes the addition of CO2 to RuBP

Question 7

what is RuBP?

Answer 7

a 5-C molecule that gets combined with CO2 during carbon fixation (addition is catalyzed by Rubisco)

Question 8

what is the fate of PGA?

Answer 8

using NADPH as an electron source and ATP as an energy source

PGA is reduced and converted:
- PGA –> G3P

G3P has 2 functions:
- used to make glucose
- used to regenerate RuBP

Question 9

how does RuBP get regenerated?

Answer 9

some G3P test used to make more RuBP

some G3P gets used to make glucose

Question 10

intermediate molecules from the dark reactions can be used in the production of…

Answer 10

lipids

ribose sugars for DNA and RNA

Question 11

how much energy does glucose contain?

(delta) G = ___ kcal/mol

ATP hydrolysis = ___ kcal/mol

Answer 11

glucose contains lots of energy

(delta) G = -686 kcal/mol

ATP hydrolysis = -7.3 kcal/mol

Question 12

how do organisms extract the energy from glucose?

Answer 12

glycolysis and cellular respiration

Question 13

oxidation of glucose takes place in ___ phases

the phases are…

Answer 13

4 phases

1) glycolysis

2) oxidation of pyruvate

3) citric acid cycle (aka TCA, Krebs cycle)

4) electron transport chain / chemiosmosis

Steps 2-4 are all called Cellular Respiration –> happens in the mitochondria

Question 14

the stepwise process in oxidation of glucose allows for a…

Answer 14

controlled and regulated release of energy

Question 15

during glycolysis and cellular respiration, ATP can be generated in ___ ways

those ways are:

Answer 15

2

chemiosmosis

substrate level phosphorylation

Question 16

what is chemiosmosis?

Answer 16

the flow of protons thru ATP synthase

Question 17

what happens during substrate level phosphorylation?

Answer 17

an enzyme:

1) takes a phosphate from 1 molecule

2) adds the phosphate to ADP
- ADP –> ATP

Question 18

what happens during glycolysis?

where does glycolysis occur?

Answer 18

glucose is converted to pyruvate

cytoplasm

Question 19

what are the inputs and outputs of glycolysis?

Answer 19

inputs:
- 1 glucose
- 2 NAD+
- 2 DP

outputs:
- 2 NADH
- 2 ATP
- 2 pyruvates

Question 20

how does oxidation of pyruvate occur in presence of oxygen?

where does this occur?

Answer 20

aerobic respiration –> cellular respiration

in mitochondria

Question 21

describe cellular respiration

Answer 21

• complete oxidation
• produces CO2 and H2O
• can make 36 ATP (max)
• ~38% efficiency (max)

Question 22

how does oxidation of pyruvate occur in absence of oxygen?

where does this occur?

Answer 22

anaerobic respiration –> fermentation

in cytoplasm

Question 23

describe fermentation

Answer 23

• incomplete oxidation
• produces organic products
• produces NAD+, 2 ATP (from glycolysis)
• ~2% efficiency

Question 23

describe fermentation

Answer 23

• incomplete oxidation
• produces organic products
• produces NAD+, 2 ATP (from glycolysis)
• ~2% efficiency