CITRIC ACID CYCLE Flashcards
Cyclic pathway; end and initial product is the Oxaloacetate
Important biochemical pathway in body; generates energy we need and generates CO2
The Citric Acid Cycle aka Kreb’s Cycle
Totality of biochemical reactions
Biochemical reactions: takes place in a living organism
Once food goes into the body they will undergo different biochemical reactions depends on what the body needs and will be used for different processes
Metabolism
Body: 6 tons of solid food, 10k gallon of water (70%)
Metabolic process: biochemical reactions happens inside the cell (intracellular)
releases energy during the process
All metabolic breaks large molecules into smaller molecules = energy is released
Ex: oxidation of glucose
Catabolism
small molecules are combined to form larger molecules
Requires energy during the reaction
Ex: Synthesis of proteins from monomer units (AA)
Anabolism
linear and cyclic pathway
Series of molecular or biochemical reactions organized in sequence
Converting starting material to an end product
Metabolic pathways
Metabolic pathways:
there is starting and specific final product
Starting point —> final product
Series of reactions that generates a final product
Linear pathway
Metabolic pathways:
first reactant during the pathway is also the final product
Series of reaction which generates the first reactant
End product is also first reactant used in the metabolic pathway
Cyclic pathway
A if only the first statement is true
B if only the second statement is true
C if both of the statements are true
D if neither of the statements is true
- Energy needed to run human body is obtained from food
- Multi-step process involves several different catabolic pathways
C
A if only the first statement is true
B if only the second statement is true
C if both of the statements are true
D if neither of the statements is true
- Nucleus is where most of the important biochemical process takes place
- Matrix of the mitochondria is the site of ATP production
B
Four general stages in the Biochemical Energy Production Process:
Stage 1: Digestion
Stage 2: Acetyl group formation
Stage 3: Citric acid cycle; Kreb’s cycle
Stage 4: Electron transport chain (respiratory chain; ETC) and oxidative phosphorylation
Begins in mouth (saliva; salivary amylase) contains starch digesting enzymes)
Continues in the stomach (gastric juice; pepsin)
Completed in small intestine (trypsin, other bile salts)
Results in small molecules that can cross intestinal membrane into the blood
Stage 1: Digestion
(not considered part of metabolism; extracellular)
End Products of digestion: monomer units of macromolecules
Glucose and monosaccharides from carbohydrates
Amino acids from proteins
Fatty acids and glycerol from fats and oils
(these end products are small enough to be absorbed by the body and pass across the intestinal membrane and go to the circulation
The digestion products are absorbed into the blood and transported to body’s cells)
Biochemical reactions start inside the cells; primarily mitochondria in most cases
Biochemical processes happen inside the cell
Small molecules from Stage 1 are further oxidized
Stage 2: Acetyl Group Formation
(metabolic processes starts)
End product of these oxidations is acetyl CoA: 2 C acetyl units and reduced coenzyme (NADH)
Involves numerous reactions: occur both in
Cytosol: glucose metabolism
Mitochondria: fatty acid metabolism of the cells.
First intermediate of the cycle is citric acid; Therefore designated as Citric acid cycle
First product formed during the process: citric acid = citrate
Acetyl group is oxidized to produce CO2 and energy (reduced coenzyme)
Reduced coenzyme (NADH and FADH2): have equivalent ATP molecules
The carbon dioxide (CO2) we exhale comes primarily from this stage
Stage 3: Citric Acid Cycle
(takes place inside the Mitochondria)
Most energy is trapped in reduced coenzymes NADH and FADH2 (flavin)
Some energy produced in this stage is lost in the form of heat
Final product: CO2 and NADH AND FADH2
There are different steps which could yield CO2 and reduced coenzymes
Takes place in Mitochondria
NADH and FADH2 (reduced coenzymes) are oxidized to release H+ and electrons
Needed to produce ATP molecules where are primarily the energy carriers in metabolic pathways
H+ are transported to the intermembrane space in mitochondria
Stage 4: Electron Transport Chain and Oxidative Phosphorylation
Electrons are transferred to O2 and O2 is reduced to H2O
H+ ion re-enter the mitochondrial matrix drive ATP- synthase reaction to produce ATP
Final product: ATP and H2O
ATP is the primary energy carrier in metabolic pathways
tricarboxylic acid cycle (TCA) or Krebs cycle
Named after Hans Adolf Krebs who elucidated this pathway: Nobel price guarantee in medicine
Series of biochemical reactions in which the acetyl portion of acetyl CoA is oxidized to carbon dioxide and the reduced coenzymes; FADH2 and NADH, are produced
Utilizes the final product of Stage 2 as the initial reactant with Oxaloacetate
Citric Acid Cycle
The citric acid cycle also produces 2 ATP by substrate level phosphorylation from GTP (guanosine triphosphate; similar to ATP)
Mainly a cycle with 8 steps: takes place in mitochondrial matrix is because enzymes needed is found there except enzymes used in Step 6
A if only the first statement is true B if only the second statement is true C if both of the statements are true D if neither of the statements is true Two important types of reactions in Citric Acid Cycle:
- Oxidation of NAD+ and FAD to produce NADH and FADH2 (reduced coenzymes)
- Hydrolysis of citric acid to produce carbon dioxide
A
