MCAT BIOCHEM Part 2 Flashcards
__ is the substrate concentration at which the reaction velocity is half its maximum
Michaelis constant Km
If an enzyme-substrate pair has a low Km ___
it means that not very much substrate is required to get the reaction rate to half the maximum rate, the enzyme has high affinity for the substrate
An enzyme inhibitor that competes with substrate for binding at the active site of the enzyme. When the inhibitor is bound no product can be made
Competitive inhibitor
An enzyme inhibitor that can bind to the enzyme either in its free form or as enzyme-substrate complex
Mixed-type inhibition
An enzyme inhibitor that binds at a site other than the active site of an enzyme (binds to the allosteric site). This changes the three-dimensional shape of the enzyme such that it can no longer catalyze the reaction
Noncompetitive inhibitor
An enzyme inhibitor that can bind to the enzyme only after its substrate has bound. __appear to increase the affinity an enzyme has for its substrate because it effectively locks the two together
Uncompetitive inhibition
How can competitive inhibition be overcome?
Adding more substrate!!
How does adding more substrate overcome competitive inhibitors?
If the substrate concentration is high enough, the substrate can outcompete the inhibitor
Is Vmax affected by competitive inhibitor?
No the reaction just needs alot more substrate to get there
___ bind at an allosteric site, not the active site
Noncompetitive inhibitors
If the enzyme is only able to bind to the enzyme-substrate complex, it is referred to as an __
uncompetitive inhibitor
For competitive inhibitirion Vmax___ and Km____
Vmax is NOT CHANGED
Km increases
For noncompetitive inhibition Vmax___ and Km___
Vmax DECREASES
Km NO CHANGE
For uncompetitive inhibition Vmax___ and Km__
Vmax DECREASES
Km DECREASES
For mixed-type inhibition Vmax__ and Km__
Vmax DECREASES
Km varies in its change
The slope of a graph using lineweaver burk plot =
Km/Vmax
The y-intercept of a graph using lineweaver burk plot is
1/Vmax
The x-intercept using lineweaver burk plot is_
-1/Km
The first substrate in the Krebs cycle is__
Acetyl-CoA
___ is produced primarily from the oxidation of pyruvate by the pyruvate dehydrogenas complex
Acetyl-Coa
__ is produced during fatty acid oxidation and protein catabolism along with the Krebs cycle
Acetyl-Coa
A protein complex found in the inner membrane of the mitochondria that is essentially a channel that allows H+ ions to flow down from the intermembrane space to the matrix; as this occurs ATP is synthesized from ADP and Pi
ATP synthase
A small non-protein electron carrier in the electron transport chain
Coenzyme Q (ubiquinone)
The folds of the inner membrane of the mitochondrion
Cristae
A small iron-containing protein in the electron transport chain
Cytochrome C
A series of enzyme complexes found along the inner mitochondrial membrane. NADH and FADH2 are oxidized by these enzymes; the electrons are shuttled down the chain and are ultimately passed to oxygen to produce water. The electron energy is used to pump H+ out of the mitochondrial matrix; the resulting H+ gradient is subsequently used to drive the production of ATP
Electron transport chain
The reduction of pyruvate to either ethanol or lactate in order to regenerate NAD+ from NADH. ___ occurs in the absence of oxygen and allows glycolysis to continue under these conditions
Fermentation
A protein associated with FAD that is commonly involved in redox reactions
Flavoproteins
___ dephosphorylates fru-1,6-bisP in gluconeogenesis
fructose- 1,6- bisphosphatase
The simultaneous activation of metabolic pathways with opposing roles e.g. running glycolysis and gluconeogenesis at the same time. The tight regulation of metabolic pathways exists to prevent ___
futile cycling
A peptide hormone produced and secreted by the alpha cells of the pancreas__
glucagon
___ targets primarily the liver, stimulating the breakdown of glycogen, thus increasing blood glucose levels
Glucagon
A metabolic pathway that synthesizes glucose from non-carbohydrate precursors.
Gluconeogenesis
__occurs in the liver when dietary stores of glucose are unavailable and the liver has depleted its stores of glycogen and glucose
Gluconeogenesis
The enzyme that catalyzes the first step in the oxidative phase of the pentose phosphate pathway
glucose-6-phosphate dehydrogenase (G6PDH)
____ decarboxylates glucose-6-P to form ribulose-5-P and forms NADPH in the process
Glucose-6-phosphate dehydrogenase
The enzyme that decarboxylates glu-6-P in gluconeogenesis. This step is important so that glucose can exit the liver cell and enter the bloodstream
Glucose-6-phosphatase
The enzyme that catalyzes the phosphorylation and subsequent removal of one glucose monomer at the end of a glycogen polymer
Glycogen phosphorylase
The enzyme that catalyzes the addition of glucose monomers to the glycogen polymer
Glycogen synthase
The anaerobic splitting of a glucose molecule into 2 pyruvic acid molecules, producing two net ATP molecules and two NADH molecules.
Glycolysis
This is the first step in cellular respiration
Glycolysis
The bond holding two monosaccharides together
Glycosidic linkage
The enzyme that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis
Hexokinase
___ is feedback inhibited by glucose-6-P
Hexokinase
A peptide hormone produced and secreted by the B-cells of the pancreas
Insulin
__targets all cells in the body,especially the liver and muscle, and allows them to take glucose out of the blood (lowering blood glucose levels)
Insulin
The third stage of cellular respiration, in which acetyl-CoA is combined with oxaloacetate to form citric acid.
Krebs Cycle
What are the byproducts of Krebs cycle?
3 molceuls of NADH, 1 molecule of FADH2, and 1 molecule of GTP
The interior of a mitochondrion (the region bounded by the inner membrane).
Matrix
The __ is the site of action of the pyruvate dehydrogenase complex and the Krebs cycle
Matrix
This is the most common electron carrier in cellular respiration
NADH
A four-carbon molecule that binds with the two-carbon acetyl unit of acetyl-CoA to form citric acid in the first step of the Krebs cycle
Oxaloacetate
The oxidation of high energy electron carriers (NADH and FADH2) coupled to the phosphorylation of ADP, producing ATP. In eukaryotes this occurs in the mitochondria
Oxidative phosphorylation
A metabolic pathway that diverts glucose-6-P from glycolysis in order to form ribose-5-P, which can be used to synthesize nucleotides. It also produces NADPH, which can be used as reducing power in fatty acid synthesis
Pentose phosphate pathway
Decarboxylates and phosphorylates oxaloacetate to form phosphoenolpyruvate in the second step of gluconeogenesis
PEPCK Phosphpoenolpyruvate carboxykinase
The enzyme that catalyzes the phosphorylation of fructose-6 phosphate to form fructose-1-6-bisphosphate in the third step of glycolysis. This is the main regulatory step of glycolysis.
Phosphofructokinas (PFK)
Phosphofructokinase (PFK) is feedback-inhibited by __
ATP
A non-protein, but organic molecule (such as a vitamin) that is covalently bound to an enzyme as part of the active site
Prosthetic group
A group of three enzymes that decarboxylates pyruvate, creating an acetyl group and carbon dioxide
Pyruvate dehydrogenase complex
The ___is the second stage of cellular respiration
Pyruvate dehydrogenase complex
Catalyzes the final step in glycolysis, the conversion of PEP into pyruvate
`Pyruvate kinase
The product of glycolysis 2 of these are produced from a single glucose molecule
Pyruvic acid
Inb the absence of oxygen __ undergoes fermentation and is reduced to either lactic acid or ethanol
Pyruvic acid
In the presence of oxygen, ___ is oxidized to produce acetyl-CoA, which can enter the Krebs cycle
Pyruvic acid
The tight regulatory control exerted over opposing metabolic pathways in order to avoid futile cycling
Reciprocal control
The four steps in order for glucose oxidation to produce CO2 and ATP
- Glycolysis
- Pyruvate dehydrogenase complex (PDC)
- the Krebs cycle
- Electron trasport/oxidative phosphorylation
Glycolysis occurs in the __ and does NOT require oxygen
Cytoplasm
During this stage pyruvate produced in glycolysis is decarbozylated to form an acetyl group that is then attached to coenzyme A (Acetyl-CoA)
Pyruvate dehydrogenase complex
During pyruvate dehydrogenase a small amount of __ is produced
NADH
During ___ and____ can only occur when oxygen is available, but neither use OXYGEN directly
Krebs cucle or PDC
KRebs cycle and PDC occur in the __
innermost compartment of the mitochondria: the matrix
During this stage the high energy electrons carried by NADH and FADH2 are oxidized to produce ATP
Electron transport/oxidative phosphorylation
The ETC is in the __
inner mitochondrial membrane
The final stage in ETC is the __
reduction of oxygen to H20
__is the universal first step in glucose metabolism
Glycolysis
All cells from ALL DOMAINS possess the enzymes of this pathway
Glycolysis
What are the products of glycolysis?
2 Pyruvate 2ATP 2NADH 2H20 2 H+
___ is the key biochemical valve controlling the flow of substrate to product in glycolysis
Phosphofructokinase becasue its catalysis in the third step of glycolsis is very thermodynamically favorable
In oxidartive decarboxylation, pyruvate is changed from a 3-carbon molecule to a ___ while____is given off and ___ is produced
pyruvate is converted to a 2-carbon molecule, CO2 is given off, and NADH is made from NAD+
Citric acid is the first intermediate in the Krebs cycle formed from ___ and ___
Oxaloacetate (4 carbons)
Acetyl-CoA (2 carbons)
