Respiration - PP Exam 2 Flashcards
What are the four steps of aerobic respiration? (Slide9Lecture12)
glycolysis, oxidation of pyruvate to acetylCoA, citric acid cycle (Krebs cycle), and electron transport chain
What is the main form of carbon obtained by plant cells through the phloem?
sucrose
What two enzymes can break down sucrose into hexoses?
invertase and sucrose synthase
What does the conversion of sucrose to hexose phosphate regulate?
-carbohydrate metabolism
-allocation of fixed carbon dioxide to glycolysis and the pentose phosphate pathway
For glycolysis rxns that break hexose-P into triose-P, where can they occur?
both the cytoplasm and the plastids
Where does glycolysis occur?
cytosol
Where does the oxidation of pyruvate to acetyl-CoA occur?
mitochondria
Where does the Krebs Cycle occur?
mitochondria
Where does the ETC of respiration occur?
the inner mitochondrial membrane
Why is the Krebs cycle also called the “Citric Acid Cycle”?
because citric acid is the first intermediate formed in the cycle
Why is the Krebs Cycle also called the “Tricarboxylic Acid Cycle”?
because some intermediates produced are tricarboxylic acids
Explain how glycolysis occurs.
Glycolysis is the process where sucrose gets converted to pyruvate. It occurs in the following steps:
- sucrose is converted to hexoses by invertase or sucrose synthase
-hexoses converted to fructose-6-phosphate
-fructose-1-phosphate converted to fructose-1,6-bisphosphate by phosphofructokinase
-fructose-1,6-bisphosphate converted to triose-P
-triose-P converted to phosphoenolpyruvate
-phosphoenolpyruvate converted to pyruvate
What are the main products of glycolysis?
4 pyruvate molecules, 4 ATP molecules, 4 NADH molecules
What inhibits phosphofructokinase? How does it inhibit?
phosphoenolpyruvate
phosphoenolpyruvate is produced by triose-P later in glycolysis, so when the cell senses phosphoenolpyruvate it doesn’t want to waste ATP on making more triose-P’s, as it thinks it already did
What activates phosphofructokinase?
How does it activate?
high concentration of phosphate
because phosphates are at high concentration when ATP is being hydrolyzed (used), so the cell wants to complete glycolysis which produces more ATP
Explain how the oxidation of pyruvate to acetyl-CoA occurs.
-pyruvate is converted to acetly-CoA by pyruvate dehydrogenase
Explain how the Krebs Cycle occurs.
-acetyl-CoA is converted to CO2 by a series of reactions
-produces oxaloacetate, which is regenerated in the cycle and used again
-produces 2 CO2’s, 1 ATP, 3 NADH, and 1 FADH2 (all per 1 acetyl-CoA)
-the intermediates formed during the Krebs Cycle (specific names not important) used to synthesize other organic compounds
Explain the ETC of mitochondrial NADH to O2.
The electron (H+) flows in the following series:
NADH
complex I
ubiquinone
complex III
cytochrome c
complex IV
Explain the ETC of FADH2 to O2.
The electron flows in the following series:
FADH2
complex II (aka ‘succinate dehydrogenase’)
ubiquinone
complex III
cytochrome c
complex IV
How does the ETC of respiration fuel the synthesis of ATP?
The ETC forms a H+ gradient, which is used as an energy source for ATP synthase to synthesize ATP
Explain the ETC of cytoplasmic NADH to O2.
Explain the ETC of mitochondrial NADH.
NADH to ubiquinone to alternative oxidase to end products
What is the Pentose Phosphate Pathway?
What does pyruvate kinase do?
it converts phosphoenolpyruvate to pyruvate
How many ATPs are formed in glycolysis per sucrose?
4
How many pyruvate molecules are formed in glycolysis per sucrose?
4
How many NADHs are formed in glycolysis per sucrose?
4
What does pyruvate dehydrogenase do?
It converts pyruvate to acetyl-CoA
What inhibits pyruvate dehydrogenase? Why?
NADH
its a product, so inhibits
What activates pyruvate dehydrogenase? Why?
pyruvate
its a substrate, so activates
