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MCAT Biology Syllabus
The Biology syllabus for MCAT in full: 7 chapters, 39 topics and 111 sub-topics, every one listed below, plus 51 Biology flashcards with answers.
Biology syllabus: all 7 chapters
Expand any chapter to see its topics and sub-topics.
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Cell Biology
7 topics- Cell Theory
- Basic Tenets of Cell Theory
- Historical Experiments Supporting Cell Theory
- Prokaryotic vs. Eukaryotic Cells
- Structural Differences
- Functional Differences
- Examples and Roles in the Environment
- Cell Membrane Structure and Function
- Phospholipid Bilayer
- Membrane Proteins
- Membrane Transport Mechanisms (Passive Transport, Active Transport, Facilitated Diffusion, Osmosis)
- Transport Across Cell Membranes
- Endocytosis and Exocytosis
- Ion Channels and Membrane Potential
- Cell Organelles and Their Functions
- Nucleus
- Mitochondria
- Endoplasmic Reticulum (Rough and Smooth)
- Golgi Apparatus
- Lysosomes and Peroxisomes
- Cytoskeleton (Microtubules, Microfilaments, Intermediate Filaments)
- Cell Cycle and Mitosis
- Phases of the Cell Cycle (Interphase, Mitotic Phase)
- Regulation of the Cell Cycle
- Checkpoints and Apoptosis
- Meiosis and Gametogenesis
- Stages of Meiosis
- Differences Between Meiosis and Mitosis
- Formation of Sperm and Ova
- Cell Theory
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Molecular Biology
5 topics- DNA Structure and Function
- Double Helix Model
- Complementary Base Pairing
- DNA Replication
- RNA Structure and Function
- Types of RNA (mRNA, tRNA, rRNA)
- RNA Synthesis (Transcription)
- DNA Replication
- Enzymes Involved (Helicase, DNA Polymerase, Ligase)
- Leading and Lagging Strands
- Transcription and RNA Processing
- Transcription Mechanism
- RNA Splicing, Capping, and Polyadenylation
- Translation and Protein Synthesis
- Ribosome Structure and Function
- tRNA and Codon-Anticodon Interaction
- Steps of Translation (Initiation, Elongation, Termination)
- DNA Structure and Function
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Genetics and Evolution
5 topics- Mendelian Genetics
- Laws of Segregation and Independent Assortment
- Punnett Squares and Predicting Offspring Ratios
- Non-Mendelian Inheritance
- Incomplete Dominance
- Codominance
- Multiple Alleles
- Polygenic Inheritance
- Genetic Linkage and Mapping
- Linkage and Recombination
- Genetic Maps and Distance Calculation
- Population Genetics
- Hardy-Weinberg Equilibrium
- Factors Affecting Allele Frequencies (Genetic Drift, Gene Flow, Mutation, Natural Selection)
- Evolutionary Concepts
- Natural Selection
- Speciation
- Adaptive Radiation
- Phylogenetics
- Mendelian Genetics
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Microbiology
5 topics- Bacterial Structure and Function
- Cell Wall Structure
- Reproduction
- Genetic Variation
- Viral Structure and Life Cycles
- Virus Structure
- Life Cycles
- Fungi and Parasites
- Basic Characteristics and Life Cycles
- Pathogenicity and Human Disease
- Microbial Growth and Control
- Lag Phase
- Log Phase
- Stationary Phase
- Death Phase
- Methods of Control
- Host-Microbe Interactions
- Normal Flora
- Pathogenesis and Immune Evasion
- Bacterial Structure and Function
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Immunology
5 topics- Innate Immune System
- Physical and Chemical Barriers
- Phagocytic Cells
- Inflammatory Response
- Adaptive Immune System
- Lymphocytes
- Antigen Presentation and Recognition
- Clonal Selection and Expansion
- Antibodies and Antigens
- Structure and Function of Antibodies
- Types of Antibodies
- Antigen-Antibody Interactions
- Vaccination and Immune Memory
- Principles of Vaccination
- Types of Vaccines
- Long-term Immunity
- Immune System Disorders
- Autoimmune Diseases
- Allergies
- Immunodeficiency
- Innate Immune System
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Physiology
8 topics- Nervous System
- Neuron Structure and Function
- Action Potential and Synaptic Transmission
- Central Nervous System (Brain, Spinal Cord)
- Peripheral Nervous System (Somatic, Autonomic)
- Endocrine System
- Hormone Types and Mechanisms of Action
- Major Glands and Hormones (Hypothalamus, Pituitary, Thyroid, Adrenal, Pancreas, Gonads)
- Feedback Mechanisms
- Cardiovascular System
- Heart Anatomy and Physiology
- Blood Vessels and Circulation
- Blood Composition and Function
- Respiratory System
- Anatomy of the Respiratory System
- Mechanisms of Breathing
- Gas Exchange and Transport
- Digestive System
- Anatomy of the Digestive Tract
- Digestive Enzymes and Their Functions
- Nutrient Absorption
- Renal System
- Kidney Structure and Function
- Nephron and Urine Formation
- Regulation of Water and Electrolyte Balance
- Musculoskeletal System
- Muscle Structure and Contraction Mechanisms
- Bone Structure and Function
- Joint Types and Movement
- Reproductive System
- Male and Female Reproductive Anatomy
- Hormonal Regulation of Reproduction
- Gametogenesis and Fertilization
- Nervous System
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Developmental Biology
4 topics- Embryogenesis
- Stages of Early Development (Fertilization, Cleavage, Blastulation, Gastrulation)
- Germ Layer Formation
- Organogenesis
- Stem Cells and Differentiation
- Types of Stem Cells (Totipotent, Pluripotent, Multipotent)
- Mechanisms of Differentiation
- Organ Development
- Major Organ Systems Development
- Critical Periods and Teratogens
- Developmental Disorders
- Genetic Disorders
- Congenital Malformations
- Embryogenesis
MCAT Biology flashcards — 51 questions with answers
What are the three main tenets of the classical Cell Theory?
(1) All living organisms are composed of one or more cells; (2) The cell is the basic structural and functional unit of life; (3) All cells arise from pre-existing cells (Virchow's "omnis cellula e cellula").
List the four key structural differences between prokaryotic and eukaryotic cells.
Prokaryotes lack a membrane-bound nucleus (DNA in nucleoid), lack membrane-bound organelles, have a single circular chromosome, and have 70S ribosomes. Eukaryotes have a true nucleus, membrane-bound organelles, linear chromosomes, and 80S ribosomes.
Compare the ribosome sedimentation coefficients of prokaryotes and eukaryotes.
Prokaryotes have 70S ribosomes (50S + 30S subunits). Eukaryotes have 80S cytoplasmic ribosomes (60S + 40S subunits). Note the Svedberg unit ($S$) is not additive because it reflects sedimentation rate.
According to the fluid mosaic model, what are the primary components of the cell membrane?
A phospholipid bilayer (amphipathic, with hydrophilic heads outward and hydrophobic tails inward) interspersed with cholesterol, integral (transmembrane) and peripheral proteins, and carbohydrates attached as glycoproteins and glycolipids.
What role does cholesterol play in the fluidity of the animal cell membrane?
Cholesterol acts as a fluidity buffer: at high temperatures it restrains phospholipid movement (decreasing fluidity), and at low temperatures it prevents tight packing (increasing fluidity), maintaining optimal membrane fluidity across temperatures.
Distinguish passive diffusion, facilitated diffusion, and active transport with respect to gradient and energy.
Passive (simple) diffusion moves solutes down their gradient without protein or energy. Facilitated diffusion moves solutes down their gradient via a carrier/channel protein, no energy. Active transport moves solutes against their gradient and requires energy (ATP).
Describe the ion movements and stoichiometry of the $\ce{Na+/K+}$-ATPase.
Per ATP hydrolyzed, it pumps 3 $\ce{Na+}$ out of the cell and 2 $\ce{K+}$ into the cell, both against their gradients. This is primary active transport that maintains the resting membrane potential and is electrogenic.
Define osmosis and predict water movement for hypertonic, hypotonic, and isotonic external solutions.
Osmosis is diffusion of water across a semipermeable membrane from low to high solute concentration. In a hypertonic solution the cell shrinks (water leaves); in a hypotonic solution it swells/lyses (water enters); in an isotonic solution there is no net water movement.
Differentiate primary and secondary active transport.
Primary active transport uses ATP directly to move a solute against its gradient (e.g., $\ce{Na+/K+}$-ATPase). Secondary active transport (co-transport) uses the electrochemical gradient established by primary transport to drive another solute against its gradient, via symport or antiport.
What is the function of the mitochondrion and why is it considered semi-autonomous?
The mitochondrion is the site of the citric acid cycle, oxidative phosphorylation, and ATP production. It is semi-autonomous because it has its own circular DNA, 70S ribosomes, and double membrane, consistent with the endosymbiotic theory.
Contrast the functions of rough and smooth endoplasmic reticulum.
Rough ER is studded with ribosomes and synthesizes/modifies secretory and membrane proteins. Smooth ER lacks ribosomes and functions in lipid/steroid synthesis, detoxification, and (in muscle) calcium storage.
What is the role of the Golgi apparatus, and name its cis and trans faces.
The Golgi modifies, sorts, packages, and ships proteins and lipids into vesicles. The cis face (near the ER) receives vesicles; the trans face (near the membrane) ships them to their destinations.
Compare the enzymatic roles of lysosomes and peroxisomes.
Lysosomes contain acid hydrolases that digest macromolecules and cellular debris via autophagy at low pH (~5). Peroxisomes break down very-long-chain fatty acids via $\beta$-oxidation and detoxify, producing and degrading $\ce{H2O2}$ using catalase.
Name the phases of interphase and what occurs in each.
$G_1$ (cell growth, organelle synthesis), $S$ (DNA replication, chromosomes duplicated), and $G_2$ (further growth, preparation for mitosis). $G_0$ is a non-dividing resting state.
List the four stages of mitosis in order and one key event in each.
Prophase (chromatin condenses, spindle forms, nuclear envelope breaks down), Metaphase (chromosomes align at the metaphase plate), Anaphase (sister chromatids separate to opposite poles), Telophase (nuclear envelopes reform, chromosomes decondense), followed by cytokinesis.
What occurs at the $G_2/M$ checkpoint and which molecule drives it?
The $G_2/M$ checkpoint verifies that DNA has been correctly and completely replicated and there is no DNA damage before mitosis. It is driven by MPF (maturation-promoting factor), a complex of cyclin B and cyclin-dependent kinase 1 (CDK1).
How does meiosis differ from mitosis in outcome (ploidy and number of daughter cells)?
Mitosis produces 2 genetically identical diploid ($2n$) daughter cells. Meiosis produces 4 genetically unique haploid ($n$) daughter cells through two divisions (meiosis I and II).
What are synapsis and crossing over, and when do they occur?
Synapsis is the pairing of homologous chromosomes to form tetrads (bivalents), and crossing over is the exchange of genetic material between homologs at chiasmata. Both occur in prophase I of meiosis, generating genetic recombination.
When do homologous chromosomes separate versus sister chromatids in meiosis?
Homologous chromosomes separate during anaphase I (reductional division, $2n \to n$). Sister chromatids separate during anaphase II (equational division), analogous to mitosis.
Compare spermatogenesis and oogenesis in terms of number and size of functional gametes.
Spermatogenesis produces 4 functional, equal-sized sperm per primary spermatocyte. Oogenesis produces 1 large functional ovum plus 2-3 polar bodies per primary oocyte, due to unequal cytoplasmic division.
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Describe the double-helix structure of DNA including strand orientation and helix type.
DNA is a right-handed double helix of two antiparallel strands (one $5'\to 3'$, the other $3'\to 5'$) with a sugar-phosphate backbone and nitrogenous bases pairing in the interior; standard B-DNA.
State Chargaff's rules and the base-pairing / hydrogen-bond details in DNA.
Chargaff's rules: %A = %T and %G = %C, so purines = pyrimidines. Adenine pairs with thymine via 2 hydrogen bonds; guanine pairs with cytosine via 3 hydrogen bonds.
List three structural differences between DNA and RNA.
DNA has deoxyribose sugar, uses thymine, and is typically double-stranded. RNA has ribose sugar (2'-OH), uses uracil in place of thymine, and is typically single-stranded.
Name the three main types of RNA and their functions.
mRNA carries the genetic code from DNA to the ribosome; tRNA carries amino acids and reads codons via its anticodon; rRNA forms the structural and catalytic core of the ribosome.
Why is DNA replication described as semiconservative, and who demonstrated this?
Each daughter molecule retains one parental (old) strand and one newly synthesized strand. Meselson and Stahl demonstrated this in 1958 using $\ce{^{15}N}$/$\ce{^{14}N}$ density-gradient centrifugation.
Contrast the leading and lagging strands in DNA replication.
The leading strand is synthesized continuously in the $5'\to 3'$ direction toward the replication fork. The lagging strand is synthesized discontinuously as Okazaki fragments away from the fork, later joined by DNA ligase.
State the functions of helicase, primase, DNA polymerase III, and DNA ligase.
Helicase unwinds the double helix at the fork; primase synthesizes RNA primers; DNA polymerase III adds nucleotides $5'\to 3'$; DNA ligase seals nicks between Okazaki fragments to join the sugar-phosphate backbone.
What is the role of DNA polymerase I in prokaryotic replication?
DNA polymerase I removes the RNA primers using its $5'\to 3'$ exonuclease activity and replaces them with DNA. It also has $3'\to 5'$ proofreading exonuclease activity.
Define the terms template strand, coding strand, and identify which RNA polymerase reads.
RNA polymerase reads the template (antisense) strand $3'\to 5'$ to synthesize mRNA $5'\to 3'$. The coding (sense) strand has the same sequence as the mRNA (with T instead of U).
What three modifications convert pre-mRNA to mature mRNA in eukaryotes?
(1) Addition of a 5' 7-methylguanosine cap; (2) addition of a 3' poly-A tail; (3) splicing out of introns and joining of exons by the spliceosome.
Distinguish introns from exons.
Exons are the coding (expressed) sequences retained in mature mRNA and translated. Introns are the intervening non-coding sequences that are transcribed but spliced out before translation.
Explain the key features of the genetic code (degeneracy, wobble, start/stop).
The code is read in triplet codons, is degenerate (multiple codons per amino acid), nearly universal, and non-overlapping. The wobble hypothesis allows flexible third-base pairing. AUG (Met) is the start codon; UAA, UAG, UGA are stop codons.
Name the three stages of translation and the ribosomal sites involved.
Initiation (small subunit + initiator tRNA-fMet/Met binds start codon), elongation (aminoacyl-tRNA enters A site, peptide bond forms, translocation), and termination (release factor at stop codon). Sites: A (aminoacyl), P (peptidyl), E (exit).
State Mendel's Law of Segregation.
Each organism carries two alleles for each gene, and these alleles segregate (separate) randomly during gamete formation so that each gamete receives only one allele. This reflects homolog separation in meiosis I.
State Mendel's Law of Independent Assortment.
Alleles of different genes assort independently of one another during gamete formation, provided the genes are on different chromosomes (or far apart on the same chromosome).
For a monohybrid cross $Aa \times Aa$, give the genotypic and phenotypic ratios.
Genotypic ratio is $1\,AA : 2\,Aa : 1\,aa$ ($1:2:1$). Phenotypic ratio (complete dominance) is $3$ dominant $: 1$ recessive ($3:1$).
For a dihybrid cross $AaBb \times AaBb$, state the classic phenotypic ratio.
$9:3:3:1$ — 9 both dominant, 3 dominant A/recessive b, 3 recessive a/dominant B, 1 both recessive, assuming independent assortment and complete dominance.
Differentiate complete dominance, incomplete dominance, and codominance.
Complete dominance: heterozygote shows the dominant phenotype. Incomplete dominance: heterozygote shows a blended intermediate phenotype (e.g., red $\times$ white $\to$ pink). Codominance: both alleles fully and simultaneously expressed (e.g., AB blood type).
Explain how ABO blood type illustrates multiple alleles and codominance.
Three alleles ($I^A$, $I^B$, $i$) exist. $I^A$ and $I^B$ are codominant to each other and both dominant to $i$. Genotypes: $I^A I^A/I^A i$ = type A, $I^B I^B/I^B i$ = type B, $I^A I^B$ = type AB, $ii$ = type O.
What is the inheritance pattern of X-linked recessive traits?
The gene is on the X chromosome. Males (XY) need only one recessive allele to be affected (hemizygous); females need two. Affected fathers cannot pass it to sons but pass carrier status to all daughters. Examples: hemophilia, color blindness.
Define epistasis and pleiotropy.
Epistasis: one gene's alleles mask or modify the phenotypic expression of a different gene (e.g., coat color). Pleiotropy: a single gene influences multiple, seemingly unrelated phenotypic traits (e.g., sickle-cell).
How is recombination frequency used to construct genetic maps?
Recombination frequency (percent recombinant offspring) estimates distance between two linked genes, where 1% recombination = 1 map unit (centimorgan, cM). Closer genes recombine less; frequencies above 50% indicate unlinked (independently assorting) genes.
Why does a recombination frequency of 50% indicate genes are unlinked?
A maximum of 50% recombinants is what independently assorting genes produce, indistinguishable from genes on separate chromosomes. Genes physically far apart on the same chromosome undergo enough crossovers to appear unlinked.
State the Hardy-Weinberg allele and genotype frequency equations.
For two alleles: $p + q = 1$ and $p^{2} + 2pq + q^{2} = 1$, where $p^{2}$ is homozygous dominant frequency, $2pq$ heterozygous frequency, and $q^{2}$ homozygous recessive frequency.
List the five conditions required for Hardy-Weinberg equilibrium.
(1) No mutation, (2) no natural selection, (3) no gene flow (migration), (4) random mating, and (5) a very large (effectively infinite) population size (no genetic drift).
In a population, 16% of individuals show a recessive phenotype. Find $q$, $p$, and the heterozygote frequency.
$q^{2} = 0.16 \Rightarrow q = 0.4$; $p = 1 - q = 0.6$; heterozygote frequency $2pq = 2(0.6)(0.4) = 0.48$ (48%).
Define genetic drift and the bottleneck and founder effects.
Genetic drift is random change in allele frequencies, pronounced in small populations. Bottleneck effect: a drastic population size reduction randomly alters allele frequencies. Founder effect: a small group founds a new population with non-representative allele frequencies.
Distinguish the modes of natural selection: directional, stabilizing, and disruptive.
Directional selection favors one extreme phenotype, shifting the mean. Stabilizing selection favors intermediate phenotypes, reducing variance. Disruptive (diversifying) selection favors both extremes over intermediates, potentially leading to speciation.
Differentiate allopatric and sympatric speciation.
Allopatric speciation occurs when a physical/geographic barrier isolates populations, preventing gene flow. Sympatric speciation occurs without geographic isolation, via mechanisms like polyploidy, niche differentiation, or sexual selection within the same area.
Contrast the shapes and composition of Gram-positive and Gram-negative bacterial cell walls.
Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane, staining purple. Gram-negative bacteria have a thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS, an endotoxin), staining pink/red.
Describe the three basic bacterial morphologies and the function of bacterial flagella, pili, and plasmids.
Morphologies: cocci (spherical), bacilli (rod), and spirilla/spirochetes (spiral). Flagella enable motility; pili (fimbriae) aid adhesion and conjugation (sex pilus); plasmids are small circular extrachromosomal DNA carrying genes such as antibiotic resistance.
MCAT Biology FAQ
What is in the MCAT Biology syllabus?
MCAT Biology is split into 7 chapters: Cell Biology, Molecular Biology, Genetics and Evolution, Microbiology, Immunology, Physiology and Developmental Biology. Together they contain 39 topics and 111 sub-topics.
How many chapters are in MCAT Biology?
7 chapters, containing 39 topics and 111 sub-topics. The largest chapter is Physiology, with 8 topics.
Are there flashcards for MCAT Biology?
Yes — a 51-card Biology deck, printed in full in the flashcards section of this page and available in the Examius app with spaced repetition. The free plan covers one exam of your choice, including its flashcards; Examius Pro, a one-time purchase, unlocks every other exam and deck.