Kreb's Cycle Flashcards
What are the other two names for the Kreb’s cycle?
TCA cycle
Citric acid cycle
What can enter the Kreb’s cycle?
Fatty acids, glucose as pyruvate, amino acids
What is the purpose of the Kreb’s cycle?
Biosynthesis and energy production
What are the products of the energy production in Kreb’s cycle?
3 NADH, FADH2, 2 CO2, GTP
What are the products of the biosynthesis in Kreb’s cycle?
Glucose, fatty acids, non-essential amino acids, succinyl CoA precursor for porphyrins
What stimulates fatty acid production?
High carb diet with no exercise
What two amino acids are the easiest to make?
Aspartate and glutamate
What intermediate is required to make heme?
Succinyl CoA
What needs heme?
Hemoglobin, cytochromes
What must the Kreb’s cycle be paired with to make energy?
Electron transport chain
What is the starting molecule of Kreb’s cycle?
Acetyl CoA
What is the first equation of the Kreb’s cycle?
Oxaloacetate + acetyle CoA -> citrate
What two things can leave the Kreb’s cycle?
Citrate and malate
How do carbs enter the Kreb’s cycle?
Glycolysis
What do carbs enter the Kreb’s cycle as?
Pyruvate
What is the pre-Kreb’s step for pyruvate?
Pyruvate to acetyl CoA
What coenzymes are needed for pyruvate to acetyl CoA?
B1, B2, B3, B5/CoA, lipoic acid
How do fatty acids enter the Kreb’s cycle?
Beta oxidation into acetyl CoA
What is the purpose of the aconitase enzyme in step two?
No glucose production of fat
What two minerals support the function of the aconitase enzyme?
Iron and sulfur
What foods are rich in iron?
Spinach, red meat, raisins
What foods are rich in sulfur?
Cruciferous vegetables, eggs, asparagus, onions
What is the allosteric enzyme in the TCA cycle?
Isocitrate dehydrogenase
What two compounds, if they build up, inhibit isocitrate dehydrogenase?
NADH and ATP
What is the name of the enzyme that uses all the same co-enzymes as pyruvate dehydrogenase?
Alpha ketoglutarate dehydrogenase
Name a compound that can be made from succinyl coA
Heme
Name the enzyme that converts pyruvate to OAA
Pyruvate carboxylase
Name the high energy compound made in the step succinyl CoA -> succinate
GTP
What complex in the cytochrome chain contains the enzyme succinate dehydrogenase?
Complex II
What is the significance of succinate dehydrogenase?
Succinate dehydrogenase anchors Kreb’s to the inner mitochondrial matrix
What does succinate dehydrogenase allow for?
Kreb’s to couple to the electron transport chain
What is the location in the mitochondria of most Kreb’s cycle enzymes?
Mitochondrial matrix
What is the coenzyme for the enzyme fumarase?
Water
What is the name of the enzyme that converts malate to OAA?
Malate dehydrogenase
What coenzyme is needed for malate dehydrogenase to convert malate to OAA?
NAD+
What do ketogenic compounds enter Kreb’s cycle as?
Acetyl CoA
Name the ketogenic only compounds
Fatty acids, lysine, leucine
Name the amino acids that are both ketogenic and gluconeogenic
Phenylalanine, isoleucine, tyrosine, tryptophan
Where do gluconeogenic amino acids enter the Kreb’s cycle?
Other intermediates
What amino acids enter as pyruvate?
Alanine, glycine, cysteine, serine, threonine, tryptophan
What amino acids enter as alpha ketoglutarate?
Histidine, arginine, proline, glutamate, glutamine
What enzyme is used for the amino acids entering as alpha ketoglutarate?
SGPT
What amino acids enter as succinyl CoA?
Valine, isoleucine, methionine
What amino acids enter as fumarate?
Phenylalanine, aspartate, tyrosine
What amino acids enter as oxaloacetate?
Aspartate, asparagine
What enzyme is used for amino acids entering as oxaloacetate?
SGOT/aspartate transaminase
What is the energy yield for 1 acetyl CoA when Kreb’s and ETC are combined without accounting for heat?
12
What is the energy yield for 1 acetyl CoA when Kreb’s and ETC are combined with accounting for heat?
10
What is the total energy yield for aerobic glycolysis (depending on shuttle) without accounting for heat?
36 or 38
What is the total energy yield for aerobic glycolysis (depending on shuttle) with accounting for heat?
30 or 32
What three substances decrease the action of pyruvate dehydrogenase by end product inhibition?
NADH, acetyl CoA, ATP
What type of diet increases the concentration of OAA?
High carbohydrates
What is the impact of high carbohydrates in the diet on the rate of the TCA cycle?
Increases the rate
Why does a high alcohol diet slow the rate of the Kreb’s cycle?
Lots of NADH with alcohol dehydrogenase
What is the impact of high levels of citric acid on glycolysis?
Shuts off phosphofructokinase
What pathway is turned on by high levels of citrate in the cytoplasm
Fat synthesis
What is the impact of lack of exercise on the Kreb’s cycle?
Increases ATP which turns off the cycle
What cycle in the liver is connected with the Kreb’s cycle?
Urea cycle
