Cellular Energy
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140 Terms
What is metabolism?
The sum of all chemical reactions occurring in an organism.
What is a metabolic pathway?
A series of enzyme-catalyzed chemical reactions
What are catabolic pathways?
Pathways that break down molecules and release energy.
What are anabolic pathways?
Pathways that build molecules and require energy
Which type of pathway generally increases entropy?
Catabolic pathways
Which type of pathway generally decreases entropy?
Anabolic pathways
State the First Law of Thermodynamics.
Energy cannot be created or destroyed, only transformed
State the Second Law of Thermodynamics.
Total entropy of the universe always increases.
State the Third Law of Thermodynamics.
Entropy of a substance at absolute zero is zero
What is entropy?
A measure of disorder or randomness.
During spontaneous processes, what happens to total entropy?
It increases
What does Q10 measure?
Change in reaction rate for every 10°C temperature change.
If Q10 = 2, what happens to reaction rate when temperature rises 10°C?
It doubles.
If Q10 = 1.5, what happens to metabolic rate after a 10°C increase?
It increases by 50%.
Which energy-generating pathway produces the most ATP?
Aerobic cellular respiration.
What does ATP stand for?
Adenosine triphosphate.
ATP is classified as what type of molecule?
RNA nucleoside triphosphate.
What nitrogenous base is found in ATP?
Adenine
What sugar is found in ATP?
Ribose
How many phosphate groups are present in ATP?
Three
What is the primary role of ATP?
Cellular energy currency
What molecule is produced when ATP is hydrolyzed?
ADP
What does ATP hydrolysis release?
Energy
Why is ATP less stable than ADP?
ATP has an extra negatively charged phosphate group
What is reaction coupling?
Using an energy-releasing reaction to drive an energy-requiring reaction
What does a negative ΔG indicate?
The reaction is spontaneous and exergonic.
What does a positive ΔG indicate?
The reaction is nonspontaneous and endergonic
Is ATP hydrolysis exergonic or endergonic?
Exergonic
Is ATP synthesis from ADP exergonic or endergonic?
Endergonic
Why is ATP ideal as a cellular energy currency?
It can rapidly store and release usable energy through phosphate transfer
Where does glycolysis occur?
Cytosol
Does glycolysis require oxygen?
No
What is the overall glycolysis reaction?
Glucose → 2 pyruvate + 2 ATP + 2 NADH.
How many pyruvate molecules are produced per glucose?
2
How many NADH are produced during glycolysis?
2
How many ATP are invested during glycolysis?
2 ATP.
How many ATP are produced during glycolysis?
4 ATP.
What is the net ATP yield of glycolysis?
2 ATP
What type of ATP production occurs during glycolysis?
Substrate-level phosphorylation
What is substrate-level phosphorylation?
Direct transfer of a phosphate group to ADP.
What is the first enzyme of glycolysis?
Hexokinase
What reaction does hexokinase catalyze?
Glucose → glucose-6-phosphate.
How many ATP are used by hexokinase?
1 ATP
Why is glucose phosphorylated immediately after entering the cell?
To trap it inside the cell.
What molecule does glucose become after phosphorylation?
Glucose-6-phosphate
Which enzyme converts glucose-6-phosphate into fructose-6-phosphate?
Isomerase
What is the product of isomerization of glucose-6-phosphate?
Fructose-6-phosphate.
Which enzyme catalyzes the committed step of glycolysis?
Phosphofructokinase (PFK).
What reaction does phosphofructokinase catalyze?
Fructose-6-phosphate → fructose-1,6-bisphosphate.
How many ATP are used by phosphofructokinase?
1 ATP.
What is considered the key regulatory enzyme of glycolysis?
Phosphofructokinase
Total ATP invested before the payoff phase?
2 ATP
Fructose-1,6-bisphosphate is split into what two molecules?
DHAP and G3P.
What does DHAP stand for?
Dihydroxyacetone phosphate
What does G3P stand for?
Glyceraldehyde-3-phosphate
Which glycolytic intermediate continues directly into the payoff phase?
G3P
What happens to DHAP?
It is converted into G3P
How many G3P molecules enter the payoff phase per glucose?
2
During the payoff phase, G3P oxidation reduces what molecule?
NAD⁺
What reduced electron carrier is produced during glycolysis?
NADH
How many NADH are produced per glucose during glycolysis?
2 NADH
How many ATP are generated during the payoff phase?
4 ATP
Why is the net ATP yield only 2 ATP if 4 ATP are produced?
2 ATP were invested earlier.
What are the final products of glycolysis per glucose?
2 pyruvate, 2 ATP (net), and 2 NADH.
Can glycolysis occur in both prokaryotes and eukaryotes?
Yes
Where does pyruvate oxidation occur in eukaryotes?
Mitochondrial matrix
Where does pyruvate oxidation occur in prokaryotes?
Cytosol
What enzyme complex performs pyruvate oxidation?
Pyruvate dehydrogenase
What is the overall pyruvate oxidation reaction?
2 pyruvate → 2 acetyl-CoA + 2 CO₂ + 2 NADH.
How many NADH are produced per glucose during pyruvate oxidation?
2 NADH.
How many CO₂ molecules are produced per glucose during pyruvate oxidation?
2 CO₂
What molecule enters the Krebs cycle?
Acetyl-CoA.
What is the first step of pyruvate oxidation?
Decarboxylation
What is removed during decarboxylation?
CO₂
Pyruvate contains how many carbons?
3 carbons
After decarboxylation, how many carbons remain?
2 carbons
What happens during the oxidation step?
NAD⁺ is reduced to NADH
What molecule binds the 2-carbon acetyl group?
Coenzyme A.
What is formed when CoA binds the acetyl group?
Acetyl-CoA.
Why is acetyl-CoA important?
It carries carbon into the Krebs cycle.
What are the other names for the Krebs cycle?
Citric acid cycle and TCA cycle.
Where does the Krebs cycle occur in eukaryotes?
Mitochondrial matrix
Where does the Krebs cycle occur in prokaryotes?
Cytosol
What is the overall Krebs cycle yield per glucose?
4 CO₂, 6 NADH, 2 FADH₂, 2 ATP.
How many times does the Krebs cycle turn per glucose?
Twice
Why does the Krebs cycle run twice per glucose?
One glucose produces two acetyl-CoA
What 4-carbon molecule combines with acetyl-CoA?
Oxaloacetate
What 6-carbon molecule is formed from acetyl-CoA and oxaloacetate?
Citrate
What is the first molecule formed in the Krebs cycle?
Citrate
What molecule is regenerated at the end of the Krebs cycle?
Oxaloacetate
How many NADH are produced per turn of the Krebs cycle?
3 NADH
How many FADH₂ are produced per turn of the Krebs cycle?
1 FADH₂
How many ATP are produced per turn of the Krebs cycle?
1 ATP.
How many CO₂ are produced per turn of the Krebs cycle?
2 CO₂
Total NADH produced by the Krebs cycle per glucose?
6 NADH
Total FADH₂ produced by the Krebs cycle per glucose?
2 FADH₂
Total ATP produced by the Krebs cycle per glucose?
2 ATP
Total CO₂ produced by the Krebs cycle per glucose?
4 CO₂
Which stages of cellular respiration produce ATP via substrate-level phosphorylation?
Glycolysis and the Krebs cycle
Which stages generate the majority of NADH?
Pyruvate oxidation and the Krebs cycle