Memly's MCAT Biology and Biochemistry: 350 Key Terms

350 terms, with the biochemistry weighted heaviest.

350 cardsLast updated 2026-08-21

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Knowing a definition is rarely what a passage asks for. It asks what the definition predicts: what happens to apparent Km when the inhibitor binds the enzyme-substrate complex, why a curve shifts right when tissue turns acidic, why a protein stops migrating at one point in a pH gradient, what a band at the wrong size means. Every one of those is a definition plus one more step, and that second step is where the marks are. So every card here gives the definition and then the step that makes it usable, on 313 of the 350. The weighting follows where that reasoning is hardest rather than where content is easiest to list: 44 cards on amino acids and protein structure, 35 on enzymes and kinetics, 95 across bioenergetics and metabolism, 40 on the laboratory methods that generate the data in a passage, 50 on organ system physiology, and the rest across nucleic acids, genetics, carbohydrates and lipids. Cell structure and the step-by-step pathways of respiration and photosynthesis sit in the Cell Biology Essentials deck, so the two fit together rather than repeating each other. Cards are tagged by area and by sub-area, so you can run just enzyme kinetics, just the separation techniques, or just nitrogen metabolism on its own. Import it and the deck joins your spaced-repetition schedule. What you should end up with is the thing a passage actually tests: given a graph, a gel, or a curve, being able to say what it means and what would change it.

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What's inside

Showing 100 representative cards from the full 350-card deck.

Front	Back
Amino acid classification by side chain	Definition: The twenty standard amino acids sorted by what their side chain does in water, into nonpolar, polar uncharged, acidic, and basic groups. Why it matters: Nearly every question about folding, charge, or a mutation's effect is answered by which group the residue belongs to.
Polar uncharged amino acids	Definition: Serine, threonine, cysteine, tyrosine, asparagine, and glutamine, whose side chains hydrogen bond without carrying a net charge at neutral pH. Why it matters: Serine, threonine, and tyrosine carry the hydroxyls that kinases phosphorylate, which is why regulation clusters on this group.
Basic amino acids	Definition: Lysine, arginine, and histidine, whose side chains can accept a proton and carry positive charge. Why it matters: Lysine and arginine are protonated at physiological pH and bind the phosphate backbone of nucleic acids, which is why histones are rich in both.
Aromatic amino acids	Definition: Phenylalanine, tyrosine, and tryptophan, each carrying a ring in the side chain. Why it matters: They absorb ultraviolet light near 280 nanometres, which is how protein concentration is estimated spectrophotometrically, with tryptophan contributing most.
Cysteine and disulfide bonds	Definition: A sulfhydryl-bearing residue, two of which can be oxidized to form a covalent disulfide bridge. Why it matters: It is the only covalent cross-link in tertiary and quaternary structure, and it forms in oxidizing environments, which is why disulfides are common in secreted proteins and rare in the cytosol.
Isoelectric point	Definition: The pH at which a molecule carries no net charge. Why it matters: A protein does not migrate in an electric field at this pH, which is the whole basis of isoelectric focusing, and it is least soluble there because charge repulsion between molecules disappears.
Titration curve of an amino acid	Definition: A plot of pH against added base showing a plateau at each pKa and a steep rise between them. Why it matters: Buffering capacity is greatest at each pKa, where the species is half deprotonated, and the isoelectric point sits on the steep segment between two plateaus.
Essential amino acids	Definition: The amino acids an adult human cannot synthesize and must obtain from the diet. Why it matters: The distinction is about biosynthetic capacity rather than importance, and some are conditionally essential when synthesis cannot keep pace with demand.
Peptide bond geometry	Definition: The amide linkage between residues, which has partial double bond character from resonance and is therefore planar. Why it matters: No rotation is possible about the peptide bond itself, so backbone conformation is described entirely by the two angles on either side of it. Often confused with: Free rotation. The bond is rigid and almost always in the trans arrangement.
Alpha helix	Definition: A right-handed coil held by hydrogen bonds between the backbone carbonyl of one residue and the amide hydrogen four residues along. Why it matters: The hydrogen bonds are backbone to backbone, so any sequence can in principle form one, and side chains project outward. Often confused with: Side chain bonding. Secondary structure is a backbone phenomenon.
Beta turn	Definition: A short backbone reversal, typically of four residues, that lets a chain fold back on itself. Why it matters: Glycine and proline dominate turns, the first for flexibility and the second for its built-in kink.
Chaperonin	Definition: A barrel-shaped complex that encloses a partly folded polypeptide and gives it an isolated chamber in which to fold. Why it matters: Isolation prevents aggregation with neighbouring unfolded chains, which is the main risk in a crowded cytosol.
Protein glycosylation	Definition: Attachment of carbohydrate to a protein, N-linked through asparagine or O-linked through serine or threonine. Where: Begins in the endoplasmic reticulum for N-linked chains and is elaborated in the Golgi. Why it matters: The sugar governs folding quality control, stability, and cell surface recognition.
Hemoglobin quaternary structure	Definition: A tetramer of two alpha and two beta subunits, each holding a haem group with a central iron. Why it matters: Having four subunits is what makes cooperative binding possible, since one subunit can report its state to the others.
2,3-bisphosphoglycerate	Definition: A glycolytic side product that binds in the central cavity of deoxyhemoglobin and stabilizes the low-affinity state. Why it matters: Its concentration rises at altitude and in chronic hypoxia, which shifts the curve right and improves unloading without changing hemoglobin itself.
Oxidoreductases	Definition: Enzymes catalyzing electron transfer, usually paired with a nicotinamide or flavin coenzyme. Recognized by: Names containing dehydrogenase, oxidase, reductase, or peroxidase.
Lyases	Definition: Enzymes breaking a bond without water and without oxidation, often leaving a double bond, or adding a group across one. Recognized by: Synthases, decarboxylases, and aldolases. Often confused with: Ligases, which join molecules and require energy input.
Transition state stabilization	Definition: The central catalytic strategy, in which the active site binds the transition state more tightly than the substrate. Why it matters: Lowering the energy of the highest point on the path is what reduces activation energy, so a molecule resembling the transition state is a very tight inhibitor.
Serine protease catalytic triad	Definition: Serine, histidine, and aspartate arranged so that histidine deprotonates serine and aspartate orients histidine. Why it matters: The three residues are distant in sequence and adjacent in the folded protein, which is a standard illustration that function follows tertiary structure.
Michaelis-Menten equation	Definition: The relationship giving initial reaction velocity as a function of substrate concentration, rising hyperbolically to a maximum. Assumes: A steady state in which the enzyme-substrate complex is formed and consumed at equal rates, and initial velocity measured before product accumulates.
Lineweaver-Burk plot	Definition: A double reciprocal plot of one over velocity against one over substrate concentration, giving a straight line. Reads out: The vertical intercept is the reciprocal of Vmax, the horizontal intercept is the negative reciprocal of Km, and the slope is Km over Vmax. Why it matters: Inhibition types are told apart by which intercept moves, which is much harder to see on the hyperbolic plot.
Uncompetitive inhibition	Definition: An inhibitor that binds only the enzyme-substrate complex, lowering both Km and Vmax. Why it matters: Removing the complex pulls the binding equilibrium forward, which is why apparent affinity appears to improve while output falls. On a double reciprocal plot: Parallel lines, because both terms fall by the same factor.
Sigmoidal kinetics of an allosteric enzyme	Definition: A velocity curve that is S-shaped rather than hyperbolic, so Michaelis-Menten analysis does not describe it. Why it matters: The shape comes from cooperativity between subunits, which makes the enzyme act as a switch across a narrow substrate range.
Isozymes	Definition: Distinct proteins catalyzing the same reaction with different kinetic properties, often expressed in different tissues. Example: Hexokinase and glucokinase, which act on glucose with very different Km values.
Coenzyme A	Definition: A pantothenate-derived carrier that binds acyl groups through a high-energy thioester bond. Why it matters: The thioester is what makes an acyl group transferable, so coenzyme A appears wherever two-carbon and larger acyl units move between pathways.
Aldose and ketose	Definition: Sugars classified by whether the carbonyl sits at the end of the chain as an aldehyde or within it as a ketone. Why it matters: Only the aldehyde form is directly oxidizable, which is why ketoses must isomerize before they register in a reducing sugar test.
Mutarotation	Definition: The spontaneous interconversion of alpha and beta anomers in solution, passing through the open chain form. Why it matters: A pure anomer dissolved in water relaxes to an equilibrium mixture, which is why optical rotation drifts to a fixed value.
Reducing sugar	Definition: A sugar with a free anomeric carbon, able to open to the aldehyde and be oxidized. Why it matters: Sucrose is not reducing because both anomeric carbons are locked in its glycosidic bond, while lactose and maltose are.
D and L designation in sugars	Definition: Assignment made from the chiral carbon furthest from the carbonyl, with the hydroxyl on the right in a Fischer projection defining D. Why it matters: Essentially all biological sugars are D, which is the mirror image of the convention for amino acids, where the L form predominates.
Fatty acid nomenclature	Definition: A fatty acid is described by chain length and by the number and position of double bonds. Why it matters: Position is counted from the carboxyl carbon in systematic naming and from the methyl end in omega naming, so the same molecule carries two different numbers.
Why fat stores more energy than carbohydrate	Definition: Fatty acid carbons are more reduced than sugar carbons and triacylglycerols are stored without water. Why it matters: The energy difference is roughly twofold per gram before hydration is counted, and considerably more once it is, which is why long-term storage is lipid rather than glycogen.
Steroid backbone	Definition: Four fused rings, three of six carbons and one of five. Why it matters: Members differ only in attached functional groups and oxidation state, which is why testosterone and estradiol are close relatives despite opposite effects.
Micelle, bilayer and liposome	Definition: A micelle is a single-tailed aggregate with a hydrophobic core, a bilayer is a two-leaflet sheet, and a liposome is a closed bilayer vesicle with an aqueous interior. Why it matters: Which one forms depends on the shape of the molecule, so single-tailed detergents make micelles and two-tailed phospholipids make bilayers.
Nucleoside and nucleotide	Definition: A nucleoside is a base joined to a sugar. A nucleotide adds one or more phosphates. Why it matters: Polymerases add nucleoside triphosphates and release pyrophosphate, so the triphosphate supplies both the residue and the energy for the bond.
DNA melting temperature	Definition: The temperature at which half of a DNA population has separated into single strands. Raised by: Higher GC content, greater length, and higher salt concentration that screens backbone repulsion.
DNA supercoiling	Definition: Over- or under-winding of the double helix relative to its relaxed state. Why it matters: Unwinding at a replication fork drives positive supercoils ahead of it, which would stall the fork if they were not relieved.
Proofreading by DNA polymerase	Definition: A 3' to 5' exonuclease activity that excises a mismatched nucleotide immediately after it is added. Why it matters: It acts during synthesis, which distinguishes it from repair systems that act afterward, and it accounts for most of replication's accuracy.
Eukaryotic RNA polymerases	Definition: Polymerase I makes most ribosomal RNA, polymerase II makes messenger RNA and several small RNAs, and polymerase III makes transfer RNA and one ribosomal RNA. Why it matters: Only the polymerase II transcripts are capped and polyadenylated, so processing follows from which enzyme made the transcript.
Polycistronic messenger RNA	Definition: A single transcript encoding several proteins, each with its own start and stop signals. Why it matters: It is a prokaryotic arrangement that follows from operon organization, and eukaryotic transcripts are monocistronic instead.
Ribosomal A, P and E sites	Definition: The A site accepts the incoming charged transfer RNA, the P site holds the growing chain, and the E site releases the deacylated transfer RNA. Why it matters: The order A to P to E is the direction of movement during translocation, so naming the site names the stage.
Nonsense-mediated decay	Definition: A surveillance pathway degrading transcripts carrying a premature stop codon. Why it matters: It prevents accumulation of truncated proteins, so a nonsense mutation often removes the message rather than producing a short protein.
High-energy phosphate compounds	Definition: Molecules whose phosphate transfer releases a large amount of free energy, including ATP, creatine phosphate, phosphoenolpyruvate, and 1,3-bisphosphoglycerate. Why it matters: The energy is in the difference between reactant and product stability, from charge repulsion and resonance in the released phosphate, not in the bond itself.
Redox potential and electron flow	Definition: A measure of a species' tendency to accept electrons, with electrons flowing spontaneously toward the more positive potential. Why it matters: The respiratory chain is ordered by increasing potential, ending at oxygen, so the sequence of carriers is set by thermodynamics rather than by convention.
Investment and payoff phases of glycolysis	Definition: The first phase consumes ATP to phosphorylate and split the six-carbon sugar, and the second recovers more ATP from the two three-carbon products. Why it matters: Phosphorylation traps the sugar in the cell and destabilizes it for cleavage, so spending ATP early is what makes the later yield possible.
Glyceraldehyde 3-phosphate dehydrogenase step	Definition: The oxidation that reduces NAD+ and captures the energy as a high-energy acyl phosphate. Why it matters: It is where glycolysis produces its reducing equivalents, which is why the pathway stalls without a way to regenerate NAD+.
Fructose entry into glycolysis	Definition: Fructose enters below the main regulatory step, being split into three-carbon units after phosphorylation in the liver. Why it matters: Bypassing phosphofructokinase-1 means fructose metabolism is not slowed by high energy charge the way glucose is.
Pyruvate dehydrogenase complex	Definition: A multi-enzyme assembly using thiamine pyrophosphate, lipoic acid, coenzyme A, FAD, and NAD+ to convert pyruvate to acetyl CoA. Why it matters: The reaction is irreversible, which is why fatty acids cannot be converted back into glucose in humans.
Anaplerotic reactions	Definition: Reactions replenishing citric acid cycle intermediates that have been withdrawn for biosynthesis. Example: Pyruvate carboxylase converting pyruvate to oxaloacetate, activated by acetyl CoA. Why it matters: The cycle is catalytic, so removing an intermediate slows every subsequent turn until it is replaced.
Respiratory chain complexes	Definition: Four membrane complexes, with complexes I, III, and IV pumping protons and complex II feeding electrons in without pumping. Why it matters: Because complex II does not pump, electrons entering there yield less ATP than those entering at complex I.
Uncoupling proteins	Definition: Inner membrane proteins allowing protons to return to the matrix without passing through ATP synthase. Why it matters: The gradient's energy is released as heat instead of ATP, which is the basis of non-shivering thermogenesis in brown adipose tissue.
Gluconeogenesis	Definition: Synthesis of glucose from pyruvate, lactate, glycerol, and glucogenic amino acids, mainly in the liver. Why it matters: It is not simply reversed glycolysis, because three glycolytic steps are irreversible and must be bypassed.
Glycogenesis	Definition: Glycogen synthesis, in which glucose is activated as UDP-glucose and added by glycogen synthase, with a branching enzyme forming alpha-1,6 links. Why it matters: Activation as a uridine nucleotide is what makes addition thermodynamically favourable.
Lipolysis	Definition: Hydrolysis of stored triacylglycerol into fatty acids and glycerol by hormone-sensitive lipase and associated enzymes. Regulated by: Activated by phosphorylation downstream of glucagon and adrenaline, and suppressed by insulin.
Oxidation of odd-chain fatty acids	Definition: The final cycle yields propionyl CoA, which is converted through methylmalonyl CoA to succinyl CoA. Why it matters: Succinyl CoA is a citric acid cycle intermediate, so the three-carbon remnant of an odd-chain fatty acid is glucogenic while the rest is not.
Acetyl-CoA carboxylase	Definition: The committed and rate-limiting step of fatty acid synthesis, forming malonyl CoA using biotin and ATP. Regulated by: Activated by citrate and insulin signalling, inhibited by phosphorylation and by the long-chain acyl CoA products.
HMG-CoA reductase step	Definition: The rate-limiting and committed step of cholesterol synthesis, reducing HMG-CoA to mevalonate using NADPH. Why it matters: The same HMG-CoA intermediate appears in ketogenesis, but that pathway is mitochondrial while cholesterol synthesis is cytosolic.
Transamination	Definition: Transfer of an amino group from an amino acid to a keto acid, producing a new amino acid and a new keto acid. Why it matters: It is freely reversible and conserves nitrogen, so it redistributes amino groups rather than removing them.
Urea cycle	Definition: The hepatic pathway converting ammonia into urea for excretion, spanning mitochondrion and cytosol. Why it matters: The two nitrogen atoms of urea come from different sources, one from free ammonia and one from aspartate.
Glucogenic and ketogenic amino acids	Definition: Glucogenic skeletons enter as pyruvate or a citric acid cycle intermediate, ketogenic ones as acetyl CoA or acetoacetyl CoA. Why it matters: Only leucine and lysine are purely ketogenic, and because acetyl CoA cannot become glucose, only the glucogenic group supports gluconeogenesis.
Purine synthesis	Definition: Stepwise construction of the base directly onto a ribose phosphate scaffold, so the nucleotide is built rather than assembled from a free base. Why it matters: It is expensive in ATP and in one-carbon units from folate, which is why the salvage pathway carries most of the load in resting cells.
Absorptive state	Definition: The hours after a meal, when insulin is high and the body stores incoming fuel as glycogen, triacylglycerol, and protein. Why it matters: Glucose is the dominant fuel for every tissue during this window, so fatty acid oxidation is suppressed rather than merely unnecessary.
Metabolic actions of insulin	Definition: Promotes glucose uptake in muscle and adipose tissue, glycogen and fatty acid synthesis, and protein synthesis, while suppressing lipolysis and gluconeogenesis. Why it matters: It is the only hormone that lowers blood glucose, which is why its actions are described as anabolic across every fuel class at once.
Liver as the metabolic hub	Definition: The organ receiving portal blood first and holding the enzymes for gluconeogenesis, ketogenesis, urea synthesis, and lipoprotein assembly. Why it matters: It buffers the composition of blood leaving it, so other tissues see a far steadier supply than the gut delivers.
Chemical classes of hormones	Definition: Peptide and protein hormones, steroid hormones, and amino acid derivatives. Why it matters: Solubility follows the class, and solubility decides whether the hormone needs a surface receptor and whether it travels bound to a carrier protein.
Tropic hormones	Definition: Hormones whose target is another endocrine gland rather than a non-endocrine tissue. Why it matters: They create the layered feedback structure, so removing the target gland raises the tropic hormone as feedback is lost.
Column chromatography	Definition: Separation of a mixture passed through a packed column, with components emerging at different times according to how strongly they interact with the packing. Why it matters: Every chromatographic method is this one idea with a different basis of interaction, so identifying the basis predicts the elution order.
Affinity chromatography	Definition: Separation using a ligand bound to the column that binds only the target protein. Why it matters: It can purify a protein in one step because selectivity comes from biological recognition rather than from a bulk property.
SDS-PAGE	Definition: Gel electrophoresis in which a detergent denatures proteins and coats them with negative charge proportional to length. Why it matters: Uniform charge-to-mass ratio removes charge and shape as variables, so migration reports size alone.
Two-dimensional gel electrophoresis	Definition: Isoelectric focusing in one direction followed by SDS-PAGE at right angles to it. Why it matters: Combining two independent properties resolves far more proteins than either alone, which is why it was the original proteomics workhorse.
Edman degradation	Definition: Sequential removal and identification of one residue at a time from the amino terminus. Why it matters: It reads only a limited stretch before yields decay, and it fails on a blocked amino terminus, which is why long sequences are obtained another way.
Spectrophotometry and the Beer-Lambert relationship	Definition: Absorbance is proportional to concentration, path length, and the molar absorptivity of the substance. Why it matters: It makes concentration measurable without consuming the sample, and it underlies almost every continuous enzyme assay.
Immunoprecipitation	Definition: Capture of a target protein from a mixture using an antibody attached to a solid support. Why it matters: Partners bound to the target come down with it, which is how protein interactions are demonstrated in a cell extract.
Southern blot	Definition: Transfer of size-separated DNA to a membrane, detected with a labelled nucleic acid probe. Why it matters: It detects a specific sequence within a complex genome, and the pattern of bands reports restriction site differences between individuals.
Sanger dideoxy sequencing	Definition: Sequencing by chain termination, using dideoxynucleotides that lack the 3' hydroxyl needed to extend further. Why it matters: Termination is random and the fragments are separated by size, so the ladder read from smallest upward gives the sequence.
Cloning vector	Definition: A DNA molecule able to replicate independently and carry an inserted fragment, usually a plasmid or a viral vector. Requires: An origin of replication, a selectable marker, and a site for inserting the fragment.
Site-directed mutagenesis	Definition: Deliberate alteration of a chosen codon to test what a particular residue contributes. Why it matters: It converts a structural hypothesis into a testable prediction, which is how catalytic residues are confirmed.
Penetrance	Definition: The proportion of individuals carrying a genotype who show any of the associated phenotype. Why it matters: Incomplete penetrance lets a trait appear to skip a generation without the allele having been lost, which breaks simple pedigree reasoning. Often confused with: Expressivity, which is about degree rather than presence.
Mosaicism	Definition: The presence of two or more genetically different cell populations in one individual, arising from a mutation after fertilization. Why it matters: Whether the change is transmitted depends on whether the germ line is involved, so somatic and germline mosaicism differ in consequence.
Autosomal recessive inheritance pattern	Definition: A trait appearing in siblings without appearing in the parents, affecting both sexes about equally. Why it matters: Two unaffected carriers are the usual parents, which is why the pattern looks like the trait skipped a generation.
Compound heterozygote	Definition: An individual carrying two different mutant alleles at the same locus rather than two copies of the same one. Why it matters: The phenotype can be intermediate or unusual, so a recessive condition need not mean two identical alleles.
Loss-of-function mutation	Definition: A change reducing or abolishing the activity of a gene product. Why it matters: It is usually recessive, because one working copy commonly makes enough product.
Haploinsufficiency	Definition: A situation in which one working copy of a gene does not produce enough product for the normal phenotype. Why it matters: It explains how a loss-of-function change can nonetheless behave as dominant.
Linkage disequilibrium	Definition: Non-random association of alleles at nearby loci, so particular combinations occur more often than chance would give. Why it matters: It decays with distance and with generations, so its extent estimates how recently a variant arose.
Consanguinity and homozygosity	Definition: Mating between relatives raises the chance that offspring inherit two copies of an allele from a shared ancestor. Why it matters: It changes genotype frequencies toward homozygosity without changing allele frequencies, which is why it violates a Hardy-Weinberg assumption.
Resting membrane potential	Definition: The steady negative interior voltage of an unstimulated neuron, set mainly by potassium permeability and maintained by the sodium-potassium pump. Why it matters: The membrane is far more permeable to potassium than to sodium at rest, so resting potential sits near the potassium equilibrium value.
Removal of neurotransmitter from the synapse	Definition: Termination by enzymatic degradation, reuptake into the presynaptic terminal, or diffusion away. Why it matters: Without removal the receptor stays occupied, so the mechanism of clearance sets how briefly a synapse can signal.
Sympathetic and parasympathetic compared	Definition: Sympathetic fibres leave the thoracic and lumbar cord with short preganglionic and long postganglionic neurons. Parasympathetic fibres leave the brainstem and sacral cord with the opposite arrangement. Why it matters: The short sympathetic preganglionic fibres synapse in a chain near the cord, which lets one signal spread widely, while parasympathetic ganglia sit on the target organ and act locally.
Excitation-contraction coupling	Definition: The sequence from membrane depolarization through calcium release from the sarcoplasmic reticulum to exposure of binding sites on the thin filament. Why it matters: Calcium is the link between an electrical event and a mechanical one, which is why contraction stops when it is pumped back.
Cardiac conduction system	Definition: Impulse arising in the sinoatrial node, delayed at the atrioventricular node, then spreading through the bundle branches and Purkinje fibres. Why it matters: The delay lets the atria empty before the ventricles contract, so timing rather than speed is the point of that step.
Determinants of cardiac output	Definition: The product of heart rate and stroke volume, with stroke volume set by preload, afterload, and contractility. Why it matters: Separating the three explains why the same output can be reached in very different ways.
Blood composition	Definition: Plasma with erythrocytes, leukocytes, and platelets, all arising from haematopoietic stem cells in marrow. Why it matters: Mature erythrocytes have no nucleus and no mitochondria, which is why they cannot repair themselves or use the oxygen they carry.
Alveolar gas exchange	Definition: Diffusion of oxygen and carbon dioxide across the thin alveolar and capillary walls, driven by partial pressure differences. Why it matters: Rate depends on surface area, membrane thickness, and the pressure gradient, so thickening the barrier impairs exchange without changing the gradient.
Nephron segments	Definition: Glomerulus and Bowman capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, and collecting duct. Why it matters: Each segment has a distinct permeability and transporter set, so knowing the segment predicts what is being moved.
Countercurrent multiplier	Definition: The loop of Henle arrangement in which a water-permeable descending limb and a salt-transporting, water-impermeable ascending limb build a medullary gradient. Why it matters: The gradient is what makes concentrated urine possible, so loop length predicts an animal's ability to conserve water.
Renal handling of acid and base	Definition: Reclamation of filtered bicarbonate and excretion of hydrogen ions buffered by phosphate and ammonia. Why it matters: It acts over hours to days, complementing the respiratory response that acts in minutes.
Pancreatic secretion	Definition: Enzymes released as inactive zymogens together with a bicarbonate-rich fluid. Why it matters: Bicarbonate raises duodenal pH into the range where pancreatic enzymes work, so the two components are useless apart.
Clonal selection	Definition: Expansion of the few lymphocytes whose receptors happen to fit an antigen, from a repertoire generated before exposure. Why it matters: The repertoire is built by random recombination in advance, so the antigen selects rather than instructs.
Hormonal control of the menstrual cycle	Definition: Follicle-stimulating and luteinizing hormones driving follicular development and ovulation, with estrogen and progesterone feeding back. Why it matters: Estrogen feedback switches from negative to positive before ovulation, which is what produces the luteinizing hormone surge.
Gastrulation and germ layers	Definition: Rearrangement producing ectoderm, mesoderm, and endoderm. Why it matters: Every tissue traces to one of the three, so knowing the layer predicts what a structure becomes.
Fetal circulatory shunts	Definition: Three diversions carrying blood past the liver and lungs before birth, closing after the first breaths. Why it matters: The lungs are fluid-filled and non-functional before birth, so bypassing them is the efficient arrangement until they inflate.

Frequently asked

Why is the deck weighted toward biochemistry?

Because that is where a definition and its consequence come apart most sharply. Amino acid chemistry, kinetics, and metabolic regulation carry 204 of the 350 cards, and they are the areas where a passage can hand you a plot and expect you to read a mechanism off it rather than recall a fact.

What is on each card?

A term on the front. On the back, a definition on all 350, and on 313 the line that makes it usable, most often the consequence that a question would actually turn on. Where two ideas are routinely swapped, the card names the other one and says what separates them. Each line is labeled, so the back reads as a short structured answer.

Does it cover the experimental and laboratory questions?

Yes, as its own block of 40 cards: chromatography by size, charge and affinity, the gel methods including SDS-PAGE and isoelectric focusing, blots and quantitative PCR, sequencing from Sanger to next-generation, and the structural methods from crystallography to cryo-electron microscopy. Each card says what the method separates by, which is what a passage figure usually depends on.

How does it fit with the Cell Biology Essentials deck?

They are built to sit side by side and share no cards. That deck covers organelles, membranes, transport, the cell cycle, and the pathways of respiration and photosynthesis step by step. This one starts where those leave off, going deeper on protein chemistry, enzyme kinetics, metabolic regulation and integration, laboratory methods, and human organ system physiology.

How is it organized for studying one area at a time?

Every card carries an area tag and a finer sub-area tag, across amino acids and proteins, enzymes, carbohydrates and lipids, nucleic acids, bioenergetics, carbohydrate metabolism, lipid and nitrogen metabolism, metabolic integration, genetics, laboratory methods, and organ systems. Filter by a tag to drill one area, or by the finer tag for a single block such as separation techniques or glycolysis detail.

Can I import the whole deck on the free plan?

Yes. Importing a saved deck runs no new AI generation and spends no AI credits, so the free plan imports every card. You can study, edit and delete them afterwards.

Will importing it twice create duplicates?

No. Cards you already have are skipped and only cards added in a revision come through. Including re-imports after deleting it, one official deck can be imported three times per account.

Can I edit the cards after importing?

Yes. Once imported they are your cards: edit either side, delete the ones you already know cold, retag them, or move them into another deck.