3. Enzymes and Metabolism

Learning Objectives

• Define enzymes and explain how they lower activation energy without being consumed in the reaction
• Describe the lock-and-key and induced-fit models of enzyme-substrate binding
• Interpret the Michaelis-Menten equation and explain what Km and Vmax reveal about an enzyme
• Differentiate competitive, noncompetitive, and uncompetitive inhibition using their effects on Km and Vmax
• Explain how feedback inhibition and allosteric regulation control metabolic flux
• Outline the key steps, committed enzymes, and clinical correlations of glycolysis, the citric acid cycle, and the pentose phosphate pathway
• Apply enzyme kinetics and inhibition concepts to diagnostic tests and drug mechanisms

Quick Answer

Enzymes are protein (or occasionally RNA) catalysts that speed up biochemical reactions by lowering activation energy, without being consumed themselves. Metabolism is the network of enzyme-catalyzed reactions — organized into pathways like glycolysis and the citric acid cycle — that breaks down molecules for energy (catabolism) or builds them up for growth and storage (anabolism). Enzyme behavior is described mathematically by Michaelis-Menten kinetics (Km and Vmax), and enzyme activity is controlled through inhibition, allosteric regulation, and feedback loops so that metabolic pathways run only when the cell needs them. This matters clinically because most drugs act by inhibiting or activating an enzyme, and most inborn errors of metabolism are caused by a single missing or defective enzyme.

Why Enzymes Matter: The Big Picture

Every reaction inside your cells — breaking down glucose, copying DNA, synthesizing a hormone — is thermodynamically possible but far too slow to sustain life without help. Enzymes solve this by binding a substrate, stabilizing the transition state, and lowering the activation energy needed for the reaction to proceed. They do not change whether a reaction is favorable (that is set by thermodynamics, ΔG), only how fast it reaches equilibrium.

Think of an enzyme as a highly specific tool rather than a generic accelerant. A wrench fits one size of bolt; hexokinase fits glucose (and a few similar sugars) and nothing else. This specificity is what makes it possible for a cell to run thousands of simultaneous reactions in the same cytoplasm without them interfering with each other.

Key characteristics of enzymes

• Specificity — each enzyme acts on a particular substrate or class of closely related substrates, determined by the shape and chemistry of its active site
• Efficiency — enzymes can accelerate reactions by factors of 10^6 to 10^12 compared to the uncatalyzed reaction
• Not consumed — the enzyme is released unchanged after catalysis and can be reused thousands of times per second
• Regulated — activity can be turned up or down by substrate availability, inhibitors, covalent modification, and allosteric effectors
• Optimum conditions — each enzyme has a temperature and pH range where its three-dimensional structure is most active; outside that range it denatures or loses efficiency

How Enzymes Bind Substrates

In 1894, Emil Fischer proposed the lock-and-key model: the active site is a rigid shape that only a matching substrate ("key") can fit into. This explains specificity well, but it cannot explain why some enzymes tolerate a range of substrates or why binding sometimes triggers conformational changes.

Daniel Koshland later refined this into the induced-fit model: the active site is flexible, and binding the substrate causes the enzyme to change shape slightly, tightening the fit and properly aligning catalytic residues. This is the model supported by modern structural biology — think of it less like a rigid lock and more like a glove that molds itself around a hand as it slides on.

Why it matters: Induced fit explains why some enzymes bind multiple related substrates with different efficiencies (the fit "induces" differently for each), and it explains allosteric regulation — effector binding at one site changes the shape of the active site elsewhere in the same molecule.

Common misunderstanding: Students often think the active site is a static pocket that never changes. In reality, most catalytically important enzymes undergo measurable conformational shifts during substrate binding — this movement is often what brings catalytic residues into the correct geometry for the reaction.

The Six Enzyme Classes

The International Union of Biochemistry classifies every enzyme into one of six mechanistic classes based on the type of reaction catalyzed:

1. Oxidoreductases — catalyze oxidation-reduction reactions (e.g., lactate dehydrogenase, alcohol dehydrogenase)
2. Transferases — transfer a functional group from one molecule to another (e.g., aminotransferases/transaminases, kinases)
3. Hydrolases — cleave bonds using water (e.g., lipases, proteases, phosphatases)
4. Lyases — break bonds without hydrolysis or oxidation, often forming a double bond or ring (e.g., aldolase, decarboxylases)
5. Isomerases — rearrange atoms within a single molecule (e.g., triose phosphate isomerase, phosphoglucomutase)
6. Ligases — join two molecules together using ATP energy (e.g., DNA ligase, pyruvate carboxylase)

Real-world example: Recognizing enzyme class names on labs and exams gives you an instant clue to function — "kinase" (a transferase) always means a phosphate group is being added, usually from ATP; "dehydrogenase" (an oxidoreductase) always means a hydride or electron is being transferred, usually to NAD+ or FAD.

Enzyme Kinetics: Michaelis-Menten

Once an enzyme binds its substrate, how fast does the reaction actually go? This is described by the Michaelis-Menten equation:

v = Vmax [S] / (Km + [S])

Where:

• v = initial reaction velocity at a given substrate concentration
• [S] = substrate concentration
• Vmax = the maximum velocity, reached when the enzyme is fully saturated with substrate
• Km = the Michaelis constant — the substrate concentration at which velocity is half of Vmax

Why it matters: Km is inversely related to an enzyme's affinity for its substrate. A low Km means the enzyme reaches half-maximal velocity at a low substrate concentration — it binds substrate tightly and is efficient even when substrate is scarce. A high Km means the enzyme needs a lot of substrate before it works efficiently — weaker binding affinity.

Real-world example: Hexokinase (found in most tissues) has a low Km for glucose, so it keeps phosphorylating glucose even when blood glucose is low, protecting glucose supply to the brain and muscle. Glucokinase (found in the liver and pancreatic beta cells) has a high Km, so it only becomes active when blood glucose is high after a meal — this makes it a glucose "sensor" that helps the liver store excess glucose and helps beta cells detect when to release insulin.

Catalytic efficiency (Vmax/Km, or more precisely kcat/Km) tells you how good an enzyme is overall at converting a low concentration of substrate to product — this is the number enzymologists use to compare different enzymes acting on the same substrate.

Common misunderstanding: Students often assume a high Km means a "better" or "stronger" enzyme. It is the opposite — Km is a measure of how much substrate is needed, so a lower Km reflects higher substrate affinity.

Enzyme Inhibition

Inhibitors are molecules that decrease enzyme activity, and how they do so has direct consequences on the kinetic parameters Km and Vmax. This is one of the most heavily tested concepts in biochemistry because it is the mechanism behind a huge fraction of pharmacology.

• Competitive inhibition — the inhibitor resembles the substrate and competes for the active site. Because it can be outcompeted by adding more substrate, Vmax is unchanged but the apparent Km increases (more substrate is needed to reach half-maximal velocity). Example: statins competitively inhibit HMG-CoA reductase by mimicking its substrate.
• Noncompetitive inhibition — the inhibitor binds a separate allosteric site (on either the free enzyme or the enzyme-substrate complex) and changes the enzyme's conformation, reducing catalytic efficiency regardless of substrate concentration. Km stays the same but Vmax decreases, and adding more substrate cannot overcome it.
• Uncompetitive inhibition — the inhibitor binds only the enzyme-substrate complex, not the free enzyme. Both Km and Vmax decrease, which is the kinetic signature that distinguishes it from the other two.
• Irreversible inhibition — the inhibitor forms a covalent bond with the enzyme (often at or near the active site), permanently inactivating it. Recovery requires synthesis of new enzyme. Example: aspirin irreversibly acetylates cyclooxygenase (COX); organophosphate pesticides and nerve agents irreversibly inhibit acetylcholinesterase.

Why it matters clinically: Whether a drug is competitive or noncompetitive changes how you manage overdose or toxicity. A competitive inhibitor's effect can sometimes be reversed by increasing substrate or displacing the inhibitor, while an irreversible inhibitor requires waiting for new enzyme synthesis (this is why aspirin's antiplatelet effect lasts the ~10-day lifespan of the platelet, since platelets cannot make new COX).

Regulation of Enzyme Activity

Cells cannot afford to run every pathway at full speed all the time — that would waste energy and create chaos. Regulation matches enzyme activity to the cell's actual needs, usually acting at the pathway's rate-limiting (committed) step.

1. Feedback inhibition — the end product of a pathway inhibits an earlier enzyme in the same pathway, so the pathway automatically slows down once enough product has accumulated. Example: isoleucine inhibits threonine deaminase, the first committed enzyme of its own synthesis pathway.
2. Allosteric regulation — effectors bind at a site distinct from the active site and change enzyme conformation, either activating or inhibiting the enzyme. Example: ATP allosterically inhibits phosphofructokinase-1 (PFK-1) in glycolysis, signaling that energy is already sufficient.
3. Covalent modification — reversible addition of a chemical group (most commonly phosphorylation) rapidly switches enzymes on or off in response to hormonal signals. Example: glycogen phosphorylase is activated by phosphorylation in response to glucagon and epinephrine.
4. Enzyme induction/repression — changing the amount of enzyme protein made, a slower but longer-lasting form of control at the level of gene transcription.
5. Compartmentalization — confining enzymes and substrates to specific organelles (e.g., beta-oxidation in mitochondria, fatty acid synthesis in cytoplasm) prevents opposing pathways from running simultaneously and wasting energy in a futile cycle.

Real-world example: After a meal, insulin promotes dephosphorylation of glycogen synthase (activating glycogen storage) while glycogen phosphorylase is dephosphorylated into its less active form — the same covalent modification (phosphorylation) has opposite functional effects on the two enzymes, which is a favorite exam trap.

Metabolic Pathways

A metabolic pathway is a sequence of enzyme-catalyzed reactions in which the product of one step becomes the substrate of the next. Pathways can be:

• Catabolic — break complex molecules into simpler ones, releasing energy (usually captured as ATP or reducing equivalents like NADH)
• Anabolic — build complex molecules from simpler ones, consuming energy
• Linear or branched — a branch point allows a pathway's intermediate to be routed toward different fates depending on the cell's needs

Catabolism and anabolism are linked by energy coupling: ATP generated during catabolic reactions (like glycolysis and oxidative phosphorylation) powers the energetically unfavorable steps of anabolic reactions (like gluconeogenesis and fatty acid synthesis).

Glycolysis: glucose to pyruvate

Glycolysis converts one glucose molecule into two pyruvate molecules in the cytoplasm, net-yielding 2 ATP and 2 NADH per glucose (without oxygen required).

• Overview: Glucose → Glucose-6-phosphate → Fructose-6-phosphate → Fructose-1,6-bisphosphate → (split into two 3-carbon units) → Glyceraldehyde-3-phosphate → ... → Pyruvate
• Key regulated enzyme: Phosphofructokinase-1 (PFK-1) catalyzes the committed, rate-limiting step (fructose-6-phosphate → fructose-1,6-bisphosphate). It is allosterically inhibited by ATP and citrate (signaling energy sufficiency) and activated by AMP and fructose-2,6-bisphosphate (signaling energy need).
• Clinical correlation: Pyruvate kinase deficiency is the second most common cause of hereditary hemolytic anemia (after G6PD deficiency) because red blood cells depend entirely on glycolysis for ATP.

Citric acid cycle (Krebs cycle): oxidizing acetyl-CoA

The citric acid cycle takes place in the mitochondrial matrix and completely oxidizes the acetyl group of acetyl-CoA to CO2, generating high-energy electron carriers.

• Overview: Acetyl-CoA + Oxaloacetate → Citrate → Isocitrate → α-Ketoglutarate → Succinyl-CoA → Succinate → Fumarate → Malate → Oxaloacetate (regenerated to run again)
• Per turn: yields 3 NADH, 1 FADH2, 1 GTP (or ATP), and 2 CO2 — these electron carriers feed the electron transport chain to generate the bulk of ATP produced from a glucose molecule
• Key regulated enzymes: Isocitrate dehydrogenase and α-ketoglutarate dehydrogenase are both inhibited by high ATP/NADH and activated by ADP/Ca2+, matching cycle activity to the cell's energy state
• Clinical correlation: Arsenic poisoning inhibits α-ketoglutarate dehydrogenase (a lipoic-acid-dependent enzyme), halting the cycle and causing severe energy failure.

Pentose phosphate pathway: NADPH and ribose-5-phosphate

Running parallel to glycolysis in the cytoplasm, this pathway branches off glucose-6-phosphate to serve two purposes that glycolysis cannot: generating NADPH for reductive biosynthesis and antioxidant defense, and generating ribose-5-phosphate for nucleotide synthesis.

• Key enzyme: Glucose-6-phosphate dehydrogenase (G6PD) catalyzes the first, rate-limiting, irreversible step and is the source of essentially all cytoplasmic NADPH in red blood cells
• Clinical correlation: G6PD deficiency is the most common enzymopathy in the world. Without enough NADPH, red blood cells cannot regenerate reduced glutathione to neutralize oxidative stress, causing hemolysis after oxidant exposure (fava beans, sulfa drugs, antimalarials, infection).

Clinical Applications of Enzymology

• Diagnosis: Measuring serum enzyme activity is a core diagnostic tool — elevated troponin and CK-MB indicate myocardial injury, elevated ALT/AST indicate hepatocyte injury, and elevated amylase/lipase indicate pancreatitis. Genetic enzyme assays diagnose inborn errors such as Pompe disease (acid alpha-glucosidase deficiency) and phenylketonuria (phenylalanine hydroxylase deficiency).
• Treatment: Enzyme replacement therapy is used for lysosomal storage disorders (e.g., imiglucerase for Gaucher disease, alglucosidase alfa for Pompe disease).
• Drug development: A large share of modern drugs act as enzyme inhibitors — ACE inhibitors block angiotensin-converting enzyme, statins block HMG-CoA reductase, and protease inhibitors block HIV protease. Understanding an enzyme's kinetics and active site geometry is central to rational drug design.

Key Terms

Term	Definition	Related Concept
Active site	The region of an enzyme where substrate binds and catalysis occurs	Induced fit, specificity
Substrate	The molecule an enzyme acts upon	Product, active site
Km (Michaelis constant)	Substrate concentration at half-maximal reaction velocity; inversely related to substrate affinity	Vmax, enzyme kinetics
Vmax	The maximum reaction velocity when the enzyme is saturated with substrate	Km, catalytic efficiency
Catalytic efficiency (kcat/Km)	A measure of how effectively an enzyme converts substrate to product, especially at low substrate concentration	Km, Vmax
Competitive inhibition	Inhibitor binds the active site, increasing apparent Km without changing Vmax	Km, active site
Noncompetitive inhibition	Inhibitor binds an allosteric site, decreasing Vmax without changing Km	Allosteric site, Vmax
Allosteric regulation	Binding of an effector at a site other than the active site that changes enzyme activity	Feedback inhibition, conformational change
Feedback inhibition	End product of a pathway inhibits an earlier (often the first committed) enzyme in that pathway	Allosteric regulation, rate-limiting step
Rate-limiting step	The slowest, most tightly regulated step in a pathway, usually catalyzed by an allosteric enzyme	PFK-1, HMG-CoA reductase
Cofactor/coenzyme	Non-protein helper molecule (metal ion or organic molecule, often vitamin-derived) required for enzyme activity	NAD+, FAD, Mg2+
Isoenzyme	Structurally different enzyme forms that catalyze the same reaction but differ in kinetics or tissue distribution	Hexokinase vs. glucokinase, LDH isoforms

Common Mistakes

Misconception: Competitive and noncompetitive inhibitors are distinguished by how "strong" the inhibition is. Why it's wrong: Strength has nothing to do with the classification — the classification is based on where the inhibitor binds and how it affects Km/Vmax. Correct understanding: Competitive inhibitors bind the active site and increase Km (overcome by more substrate, Vmax unchanged). Noncompetitive inhibitors bind an allosteric site and decrease Vmax (not overcome by more substrate, Km unchanged). Always check a Lineweaver-Burk plot: competitive inhibition changes the x-intercept, noncompetitive inhibition changes the y-intercept.

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Misconception: A high Km means an enzyme works "harder" or "better." Why it's wrong: Km reflects the substrate concentration needed to reach half-maximal velocity, which is a measure of how weakly the enzyme binds substrate, not how well it performs. Correct understanding: A low Km indicates high substrate affinity (the enzyme is efficient even at low substrate levels); a high Km indicates low affinity (a lot of substrate is required before the enzyme functions efficiently). Glucokinase's high Km, for example, is a functional feature that lets it act as a glucose sensor, not a weakness.

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Misconception: All metabolic pathways run continuously at the same rate. Why it's wrong: If every enzyme in a pathway worked at full capacity all the time, opposing pathways (like glycolysis and gluconeogenesis) would run simultaneously and waste ATP in a futile cycle. Correct understanding: Pathways are controlled at one or two committed, rate-limiting enzymes through allosteric regulation, covalent modification, and feedback inhibition, so flux through the pathway matches the cell's actual energy state and substrate availability.

Comparison and Connections

Feature	Competitive Inhibition	Noncompetitive Inhibition	Uncompetitive Inhibition
Binding site	Active site (mimics substrate)	Allosteric site (separate from active site)	Only the enzyme-substrate complex
Effect on Km	Increases (apparent)	Unchanged	Decreases
Effect on Vmax	Unchanged	Decreases	Decreases
Overcome by more substrate?	Yes	No	No
Lineweaver-Burk change	Different x-intercept, same y-intercept	Same x-intercept, different y-intercept	Parallel lines (both intercepts shift)
Example	Statins on HMG-CoA reductase	Many heavy metal poisonings	Lithium on inositol monophosphatase

Practice Questions

Recall

1. What are the six classes of enzymes recognized by the International Union of Biochemistry? Answer guidance: Oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases — classified by the type of chemical reaction each catalyzes.

2. Define Km and Vmax in the Michaelis-Menten equation. Answer guidance: Km is the substrate concentration at which reaction velocity is half of Vmax; it is inversely related to substrate affinity. Vmax is the maximum reaction velocity reached when the enzyme is fully saturated with substrate.

Understanding

3. Explain why a competitive inhibitor increases the apparent Km but does not change Vmax. Answer guidance: A competitive inhibitor competes with substrate for the same active site. Given enough substrate, the substrate can outcompete the inhibitor, so the same Vmax is still reachable — it just takes more substrate to get there, which raises the apparent Km.

4. Why does phosphofructokinase-1 (PFK-1) act as the primary control point of glycolysis rather than an earlier or later enzyme? Answer guidance: PFK-1 catalyzes the first committed, irreversible step unique to glycolysis (glucose-6-phosphate and fructose-6-phosphate are shared with other pathways). It is allosterically inhibited by ATP and citrate and activated by AMP and fructose-2,6-bisphosphate, allowing it to sense the cell's energy status directly.

Application

5. A new drug is found to increase the apparent Km of an enzyme without altering Vmax, and its effect disappears when substrate concentration is raised. What type of inhibitor is it, and how could this affect an overdose scenario? Answer guidance: This is a competitive inhibitor. In an overdose, increasing the natural substrate concentration (or giving a competing substrate analog) could displace the inhibitor and restore enzyme activity — this is the pharmacologic basis for treatments like fomepizole outcompeting alcohol dehydrogenase substrates in toxic alcohol ingestion.

6. A patient develops hemolytic anemia after taking a sulfa antibiotic. Lab workup shows normal hemoglobin electrophoresis but low enzyme activity in red blood cells. What enzyme deficiency is most likely, and why do red blood cells specifically suffer? Answer guidance: Glucose-6-phosphate dehydrogenase (G6PD) deficiency. G6PD is the rate-limiting enzyme of the pentose phosphate pathway, the sole source of NADPH in mature red blood cells (which lack mitochondria). Without NADPH, red cells cannot regenerate reduced glutathione, leaving them vulnerable to oxidative damage from the sulfa drug.

Analysis

7. Compare and contrast how feedback inhibition and covalent modification (like phosphorylation) achieve the same broad goal of regulating enzyme activity, but on different timescales. Answer guidance: Feedback inhibition is immediate and directly tied to metabolite concentration — it requires no external signal and reacts to the pathway's own product buildup. Covalent modification (e.g., phosphorylation by hormone-activated kinases) is triggered by external signals (glucagon, insulin, epinephrine) and can affect many enzymes simultaneously across a pathway or even across pathways, coordinating a whole-body response rather than a purely local one.

8. A researcher measures an enzyme's activity in the presence of an inhibitor and finds that both Km and Vmax decrease proportionally, with the ratio Vmax/Km remaining unchanged for the double-reciprocal plot's slope pattern. What kind of inhibition is this, and what does it suggest about the inhibitor's binding site? Answer guidance: This describes uncompetitive inhibition, which produces parallel lines on a Lineweaver-Burk plot (same slope, shifted intercepts). It suggests the inhibitor binds only to the enzyme-substrate complex (not the free enzyme), which is why both Km and Vmax decrease together rather than only one changing.

FAQ

1. What's the real difference between a cofactor and a coenzyme? A cofactor is any non-protein component required for enzyme activity, which includes both inorganic ions (like Mg2+, Zn2+, Fe2+) and organic molecules. A coenzyme is specifically an organic cofactor, and most coenzymes are derived from vitamins — NAD+ and NADP+ come from niacin (B3), FAD comes from riboflavin (B2), and coenzyme A comes from pantothenic acid (B5). This is why chronic vitamin deficiencies can look like inherited enzyme defects — the enzyme protein is fine, but its required coenzyme is missing.

2. Why do exam questions always ask about Lineweaver-Burk plots instead of the regular Michaelis-Menten curve? The Michaelis-Menten curve is a hyperbola, which makes it hard to read Km and Vmax precisely by eye — Vmax is an asymptote you never quite reach. The Lineweaver-Burk (double-reciprocal) plot of 1/v against 1/[S] turns the hyperbola into a straight line, whose slope, x-intercept, and y-intercept can be read off exactly. This is also the easiest way to visually distinguish competitive, noncompetitive, and uncompetitive inhibition, which is exactly why it appears so often on exams.

3. If enzymes aren't consumed, why do cells need to keep making them? Cells continuously make and degrade proteins, including enzymes, as part of normal turnover — old or damaged enzyme molecules are broken down and replaced. This turnover is also how a cell can adjust the total amount of an enzyme over hours to days (enzyme induction/repression), which is a slower complement to the fast, immediate regulation from allosteric effectors and covalent modification.

4. How is the "committed step" of a pathway different from just the first step? The committed step is the first reaction that is essentially irreversible and unique to that specific pathway — once the cell passes that point, it is committed to finishing the pathway (or degrading the intermediate, at a cost). Earlier steps might be shared with other pathways and freely reversible, so they aren't good regulatory targets. This is why PFK-1, not hexokinase, is the main control point of glycolysis — hexokinase's product (glucose-6-phosphate) can still be diverted to glycogen synthesis or the pentose phosphate pathway.

5. Do I really need to memorize every intermediate in glycolysis and the citric acid cycle? For exam and clinical purposes, focus on the substrates and products of each pathway, the rate-limiting/regulated enzymes (and what regulates them), the net energy yield, and the disease associated with a defect in a key enzyme. Reciting all 10 glycolytic intermediates by name rarely appears directly on exams — being asked to identify which step is blocked when a specific enzyme is deficient, and predicting the resulting build-up or deficiency, is far more common.

Quick Revision

• Enzymes lower activation energy and speed up reactions without being consumed or changing reaction equilibrium
• Lock-and-key explains basic specificity; induced fit (the modern model) explains conformational change on binding
• Km = substrate concentration at half-maximal velocity; low Km = high substrate affinity
• Vmax = maximum velocity at enzyme saturation; changes with enzyme concentration and noncompetitive/uncompetitive inhibition
• Competitive inhibition: binds active site, increases apparent Km, Vmax unchanged, overcome by more substrate
• Noncompetitive inhibition: binds allosteric site, decreases Vmax, Km unchanged, not overcome by substrate
• Uncompetitive inhibition: binds only the enzyme-substrate complex, decreases both Km and Vmax
• Feedback inhibition and allosteric regulation control flux at a pathway's committed, rate-limiting step
• Glycolysis (cytoplasm, PFK-1 is rate-limiting) yields 2 ATP + 2 NADH per glucose without oxygen
• Citric acid cycle (mitochondrial matrix) fully oxidizes acetyl-CoA, yielding 3 NADH + 1 FADH2 + 1 GTP per turn
• Pentose phosphate pathway (via G6PD) generates NADPH for antioxidant defense and ribose-5-phosphate for nucleotide synthesis
• Serum enzyme measurement (troponin, ALT/AST, amylase/lipase) is a core diagnostic tool for tissue injury

Related Topics

Prerequisites: Introduction to Biochemistry (biomolecules, catabolism vs. anabolism), protein structure (primary through quaternary structure, since enzymes are mostly proteins), general chemistry (thermodynamics, activation energy, reaction equilibria)

Related Topics: Carbohydrate Metabolism (glycolysis and gluconeogenesis in depth), Bioenergetics and Oxidative Phosphorylation (how NADH and FADH2 become ATP), Vitamins and Coenzymes (the biochemical role of cofactors)

Next Topics: Carbohydrate Metabolism, Lipid Metabolism, Amino Acid and Protein Metabolism, Clinical Enzymology and Laboratory Diagnostics

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This page is for educational purposes. Always verify with current clinical guidelines.