Test 2 (Chapters 12-21) Flashcards
(110 cards)
What is the major source of cellular energy?
Oxidation of carbon fuels
What is is the function of common intermediates, like NADH, in the oxidation of carbon fuels?
Electron carriers - higher affinity for activated group than carbon fuels, but a lower affinity for electrons than O2.
What is the ultimate electron acceptor in the oxidation of carbon fuels?
O2
What are five (5) common activated carriers in metabolism, and what is their activated group?
- ATP (phosphoryl)
- NADH (electron)
- NADPH (electron)
- FADH2 (electron)
- CoA (acyl)
What are three (3) mechanisms of metabolic regulation?
- the amount of enzymes
- their catalytic activities
- the accessibility of substrates
How is the amount of enzymes regulated?
Its rate of synthesis and its rate of degradation; adjusted primarily by its rate of transcription.
What are four (3) ways catalytic activity is regulated?
- Feedback inhibition (allosteric regulation of the first reaction in a pathway by the ultimate product)
- Reversible covalent modification (reduce catalytic activity by structural changes, such as phosphorylation)
- Energy status of the cell (measured by energy charge or phosphorylation potential), which is buffered (catabolic reactions take place when there is low amounts of ATP, anabolic reactions take place when there is high amounts of ATP)
What are the activated and deactivated forms of the nicotinamide adenine dinucleotide?
Deactivated: NAD+
Activated: NADH
NAD+ is an electron acceptor in what types of reaction? (3 components)
- a C-H hydride and a C-OH proton are removed forming a C=O bond
- NAD+ itself accepts a hydride, forming NADH, and a proton is added to the solvent.
- called dehydrogenation because protons accompany the electrons
What are the activated and deactivated forms of the flavin adenine dinucleotide?
Deactivated: FAD
Activated: FADH2
FAD is an electron acceptor in what types of reaction? (2 components)
- C-H hydrogens on adjacent carbons are removed along with two electrons (homolytic) forming C=C bond
- FAD accepts two electrons and two protons forming FADH2
What is the structural and functional difference between NADP+ and NAD+?
(1) NADP+ uses its electrons for the reductive biosynthesis (anabolism that creates fuels that can later be oxidated). (2) It contains an additional phosphoryl group tag, not on it’s active site, that tells enzymes that it should be used for reductive biosynthesis.
What are three molecules with a higher phosphoryl-transfer potential than ATP?
- 1,3-BPG (1,3-biphosphoglycerate)
- PEP (phosphoenolpyruvate)
3 Creatine Phosphate
What is Glycolysis?
The sequence of reactions that converts one molecule of glucose into two molecules of pyruvate while generating ATP.
What is gluconeogenesis?
The sequence of reactions that converts end products of biochemical pathways into glucose.
Where does glycolysis take place?
In the cytoplasm
What are three (3) factors that contribute to a high phosphoryl-transfer potential?
- Electrostatic repulsion of phosphoryl groups (ATP less stable than ADP)
- Resonance stabilization (inorganic phosphate resonance more stbale than ATP)
- Stabilization due to hydration (hydrogen bonds stabilize ADP and phosphate better than ATP)
How many reactions are in glycolysis?
Ten
What are the two stages of Glycolysis?
- Stage 1 cleaves glucose into two three-carbon aldehyde fragments
- Stage 2 oxidizes the each aldehyde to pyruvate while generating two ATP.
List the reactions, including substrates and products, of Stage 1 of glycolysis and the enzymes and cofactors involved.
- Glucose -> Glucose 6-phosphate [Hexokinase, ATP]
- Glucose 6-phosphate Fructose 6-phosphate [Phosphoglucose isomerase]
- Fructose 6-phosphate -> Fructose 1,6-biphosphate [Phosphofructokinase, ATP]
- Fructose 1,6-biphosphate -> Glyceraldehyde 3-phosphate + Dihydroxyacetone phosphate [Aldolase]
- Dihydroyacetone phosphate Glyceraldehyde 3-phosphate [Triose phosphate isomerase]
List the “big picture” steps of Stage 1 of Glycolysis
- Kinase phosphorylates glucose
- Isomerase prepares phosphorylated-glucose to be phosphorylated again
- Second phosphorylation occurs
- 6-carbon sugar is cleaved into a usable aldehyde and an unusable ketone
- Ketone product is converted to aldehyde product by an isomerase.
What is the important step that commits glucose to glycolysis?
Phosphorylation by Hexokinase
What irreversible reaction of Stage 1 of glycolysis uses a key regulatory enzyme?
Fructose 6-phosphate -> Fructose 1,6-biphosphate [Phosphofructokinase, ATP]
List the reactions, including substrates and products, of Stage 1 of glycolysis and the enzymes and cofactors involved.
- Glyceraldehyde 3-phosphate 1,3-Biphosphoglycerate + NADH [inorganic phosphate, NAD+, glyceraldehyde 3-phosphate dehydrogenase]
- 1,3-Biphosphoglycerate 3-Phosphoglycerate + ATP [ADP, Phosphoglycerate kinase]
- 3-Phosphoglycerate 2-Phosphoglycerate [Phosphoglycerate mutase]
- 2-Phosphoglycerate Phosphoenolpyruvate + H2O [Enolase]
- Phosphoenolpyruvate -> Pyruvate + ATP [Pyruvate kinase]