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Lecture 2.01: Introduction to Biochemical Processes

Terms in this set (80)

Glycolysis
A metabolic process that breaks down carbohydrates and sugars through a series of reactions to either pyruvic acid or lactic acid and release energy for the body in the form of ATP
Cytosol
Where does Glycolysis occur?
Glycolysis Reactants
Glucose, 2 NAD+, 2 ATP, 4 ADP, 4Pi
Glycolysis Products
2 Pyruvates, 2 NADH, 4 ATP (2 net), 2 H2O
Glycolysis Pathway (Energy-Requiring Phase)
Glucose + 2 phosphate groups (+2 ATP) => fructose-1,6-biphosphate => DHAP + glyceraldehyde-3-phosphate
Glycolysis Pathway (Energy-Releasing Phase)
1 Glyceraldehyde-3-phosphate + 2 ATP + 1 NADH => pyruvate
Gluconeogenesis
Process of synthesizing glucose or glycogen from non-
carbohydrate precursors

Mechanism used by humans and other animals to keep
blood from glucose from dropping too low
Location of Gluconeogenesis
Start: either mitochondria or cytosol depending on
the starting substrate

End: lumen ER
Gluconeogenesis Reactants
Non-carbohydrate carbon substrates (ex.
lactate, glycerol, propionate, and glucogenic amino acid)
Gluconeogenesis Products
Glucose
Gluconeogenesis Pathway
Pyruvate => Phosphoenolpyruvic acid (PEP) => 2-phosphoglycerate => 3-phosphoglycerate => 1,3-
biphosphoglycerate => glyceraldehyde => fructose-1,6-
biphosphate => fructose-6-phosphate => glucose-6-
phosphate => glucose
Glycogenolysis
Breakdown of glycogen into glucose

Function: regulation of glucose levels in the blood and in the adrenaline-induced fight-or-flight response
Cytosol
Where does Glycogenolysis occur?
Glycogenolysis Reactants
Glycogen (n) + Pi
Glycogenolysis Products
Glycogen (n-1) + Glucose-1-phosphate
Glycogenolysis Pathway
Glycogen (n glucose residues) + Pi => Glucose
1-phosphate + Glycogen (n-1 glucose residues)
Glycogenesis
Process of synthesizing glycogen from glucose

Mechanism in which excess carbohydrates are stored in the form of glycogen, which can then be broken into glucose when needed

Activated by insulin in response to high glucose levels
Liver and Muscle
Where is glycogen stored?
Cytosol
Where does Glycogenesis occur?
Glycogenesis Reactants
Glycogen
Glycogenesis Products
Glucose
Glycogenesis Pathway
Glucose => Glucose-6-phosphate => Glucose-1-
phosphate => Uridine-diphosphate glucose => 1->4 glucosyl
residues => glycogen
Fatty Acid Synthesis
Process of synthesizing fatty acids from acetyl-CoA and NADPH
Cytosol
Where does Fatty Acid Synthesis occur?
Acetyl-CoA, acyl carrier protein (ACP), NADPH
What are the reactants in Fatty Acid Synthesis?
Palmitate
What are the products in Fatty Acid Synthesis?
Fatty Acid Synthesis Pathway
1. Malonyl-ACP condenses with an acetyl to yield
acetoacetyl-ACP followed by a series of reactions to
form butyryl-ACP
2. Six more molecules of malonyl-ACP react successively
at the carboxyl end of the fatty acid chain to form
palmitoyl-ACP
3. Palmitate is released via hydrolysis
4. Other fatty acids can be synthesized from palmitate
Fatty Acid (Beta) Oxidation
Process in which long chain fatty acids are oxidized into acetyl-CoA

High energy-yielding pathway

Occurs in tissues with high energy requirement such as the heart
Mitochondria
Where does Fatty Acid (Beta) Oxidation occur?
Fatty Acids
What are the reactants in Fatty Acid (Beta) Oxidation?
Acetyl-CoA
What are the products in Fatty Acid (Beta) Oxidation?
Fatty Acid (Beta) Oxidation Pathway
1. Fatty acid is dehydrogenated by acyl-CoA
dehydrogenase
2. Hydration by enoyl-CoA hydratase
3. Dehydrogenation by β-hydroxyacyl-CoA
dehydrogenase
4. Cleavage of the resulting β-ketoacyl-CoA by thiolase
Cholesterol Synthesis/Mevalonate Pathway
Process of synthesizing cholesterol

Tightly-controlled to prevent the over-accumulation of cholesterol within the body
Cytosol, Endoplasmic Reticulum (Microsomes), Peroxisomes
Where does Cholesterol Synthesis occur?
Acetyl-CoA
What are the reactant(s) in Cholesterol Synthesis?
Cholesterol
What are the product(s) in Cholesterol Synthesis?
Cholesterol Synthesis Pathway
Acetyl-CoA => 3-hydroxy-3-methylglutaryl-CoA
(HMG-CoA) => mevalonate => isopentenyl pyrophosphate
(IPP) => squalene => cholesterol
Tricarboxylic Acid Cycle (aka Krebs Cycle or Citric Acid Cycle)
Series of reactions that are involved in cellular respiration
Mitochondrial Matrix
Where does the Tricarboxylic Acid Cycle (aka Krebs Cycle or Citric Acid Cycle) occur?
2 Acetyl-CoA, NAD+, FAD, GDP Pi
What are the reactants in the Tricarboxylic Acid Cycle (aka Krebs Cycle or Citric Acid Cycle)?
3 NADH, FADH2, GTP, H+, 2 CO2, SH-CoA
What are the products in the Tricarboxylic Acid Cycle (aka Krebs Cycle or Citric Acid Cycle)?
Tricarboxylic Acid Cycle (aka Krebs Cycle or Citric Acid Cycle) Pathway
Acetyl-CoA + oxaloacetate => citrate => isocitrate
=> ɑ-ketoglutarate => succinyl CoA => succinate => fumarate
=> malate => oxaloacetate
Electron Transport Chain
Process which creates an electrochemical proton gradient that drives the synthesis of ATP

Net ATP yield: approx. 32-34 ATP
Inner Mitochondrial Membrane
Where does the Electron Transport Chain occur?
Free O2, NADH, FADH2, H+
What are the reactants in the Electron Transport Chain?
ATP, H2O
What are the products in the Electron Transport Chain?
Electron Transport Chain Pathway
12 H + 3 O2 à 6 H2O + 34 ATP
Urea Cycle
Process of converting toxic ammonia into urea to be
excreted by the body
Mitochondria and Cytosol
Where does the Urea Cycle occur?
Ammonia (NH3), HCO3, ATP
What are the reactants in the Urea Cycle?
Urea
What are the products in the Urea Cycle?
Urea Cycle Pathway
Inside the Mitochondria:
2 ATP + HCO3 + NH3 => carbamoyl phosphate =>
citrulline

In Cytosol:
Citrulline => argininosuccinate + aspartate => arginine + fumarate => arginine + H2O => ornithine + urea
Protein Synthesis
Process by which all cells synthesize proteins
Ribosomes
Where does Protein Synthesis occur?
mRNA, tRNA, amino acids
What are the reactants in Protein Synthesis?
Proteins
What are the products in Protein Synthesis?
Protein Synthesis Pathway
1. Ribosome complex assembles
2. As mRNA passes through the ribosome, each codon
interacts with the anticodon of a specific tRNA
3. tRNA carries the appropriate amino acid into the 3'
terminus, which incorporates it into the growing chain
4. As polypeptide grows, it folds to form a protein and
continues to grow until a stop codon is encountered
5. Ribosome releases the polypeptide
Protein Catabolism
Breakdown of proteins into compounds that are used to
synthesize new proteins
Cytosol
Where does Protein Catabolism occur?
Proteins
What are the reactants in Protein Catabolism?
Amino acids, heme, nucleotides, hormones,
neurotransmitters, urea, glucose, fatty acids, ketone bodies
What are the products in Protein Catabolism?
Protein Catabolism Pathway
Protein => amino acid pool => oxidative
deamination => carbon skeleton => pyruvate => glucose
Nucleotide Synthesis
Process by which nucleotides are synthesized

Synthesis can be de novo (anew) or from degradation products
of nucleic acids
Cytosol
Where does Nucleotide Synthesis occur?

Two types: Pyrimidine Synthesis and Purine Synthesis
All but one step occurs in the cytosol
Where does Pyridimine Synthesis occur?
Cytosol only
Where does Purine Synthesis occur?
Multiple possible pathways
depending on end product
What are the reactants and products of Nucleotide Synthesis?
Nucleotide Catabolism
Breakdown of DNA and RNA into either waste products or
into compounds that may be used to make new nucleotide
components
Cytosol
Where does Nucleotide Catabolism occur?
Nucleotides
What are the reactants in Nucleotide Catabolism?
Pyrimidine (Cytosine and Uracil) Catabolism: H2O, CO2

Purine (Adenine & Guanine) Catabolism: uric acid
What are the products in Nucleotide Catabolism (Pyrimidine vs. Purine)?
Nucleotide Catabolism Pathway (Adenine and Guanine)
DNA/RNA => nucleotides => nucleosides => hypoxanthine => xanthine => uric acid
Nucleotide Catabolism Pathway (Cytosine and Uracil)
DNA/RNA => nucleotides => beta-alanine => malonyl-CoA
Nucleotide Catabolism (Thymine)
DNA/RNA => nucleotides => β-aminoisobutyric acid => methylmalonyl-CoA => acetyl-
CoA/succinyl-CoA
Hexose Monophosphate Pathway (Pentose Phosphate Pathway)
• Oxidation of glucose 6-phosphate to produce pentose
• Pentoses formed are useful for synthesis of nucleic acids
• Produces electron-rich (reducing agent) substances
needed for lipid synthesis
Cytosol
Where does the Hexose Monophosphate Pathway (Pentose Phosphate Pathway) occur?
Glucose-6-Phosphate
What are the reactants in the Hexose Monophosphate Pathway (Pentose Phosphate Pathway)?
Pentoses, ribose-5-phosphate, NADPH
What are the products in the Hexose Monophosphate Pathway (Pentose Phosphate Pathway)?
Hexose Monophosphate Pathway (Pentose Phosphate Pathway) - Oxidative Phase
Glucose-6-phosphate => 6-
phosphogluconolactone => 6-phosphogluconate
=> ribulose-5-phosphate + NADPH
Hexose Monophosphate Pathway (Pentose Phosphate Pathway) - Non-Oxidative Phase
Ribulose-5-phosphate => xylulose-5-phosphate =>
sedoheptulose-7-phosphate + glyceraldehyde-3-phosphate => fructose-6-phosphate + erythrose-4-phosphate => fructose-6-phosphate + glyceraldehyde-3-phosphate
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