MCAT Biology Review

Molecular Biology: Enzymes and Metabolism

• Enzyme structure and function
  • Function of enzymes in catalyzing biological reactions
  • Reduction of activation energy
  • Substrates and enzyme specificity
• Control of enzyme activity
  • Feedback inhibition
  • Competitive inhibition
  • Non-competitive inhibition
• Basic metabolism
  • Glycolysis, anaerobic and aerobic, substrates and products
  • Krebs cycle, substrates and products, general features of the pathway
  • Electron transport chain and oxidative phosphorylation, substrates and products, general features of the pathway
  • Metabolism of fats and proteins

Molecular Biology: DNA and Protein Synthesis

DNA structure and function

• DNA structure and function
  • Watson-Crick model of DNA; double helix
  • DNA composition: purine and pyrimidine bases, sugars, phosphate
  • Base pairing specificity: A with T, G with C
  • Function in transmission of genetic information
• DNA replication
  • Mechanism of replication: separation of strands, specific coupling of free nucleic acids
  • Semi-conservative nature of replication
• Repair of DNA
  • Repair during replication
  • Repair of mutations
• Recombinant DNA
  • Restriction enzymes
  • Hybridization
  • Gene cloning
  • PCR

Protein synthesis

• Genetic code
  • Central Dogma: DNA -> RNA -> protein
  • Codon-anticodon relationship
  • Missense, nonsense codons
  • Initiation, termination codons (function, codon sequences)
• Transcription
  • mRNA composition and structure (RNA nucleotides, 5' cap, poly-A tail)
  • tRNA and rRNA composition and structure (e.g., RNA nucleotides)
  • Mechanism of transcription (RNA polymerase, promoters, primer not required)
• Translation
  • Roles of mRNA, tRNA, rRNA
  • Role and structure of ribosomes

Molecular Biology: Eukaryotes

• Eukaryotic chromosome organization
  • Chromosomal proteins
  • Telomeres, centromeres
• Control of gene expression in eukaryotes
  • Transcription regulation
  • DNA binding proteins, transcription factors
  • Cancer as a failure of normal cellular controls, oncogenes
  • Post-transcriptional control

Genetics

• Mendelian concepts
  • Phenotype and genotype
  • Gene
  • Locus
  • Allele: single and multiple
  • Homo- and heterozygosity
  • Wild type
  • Recessiveness
  • Complete dominance
  • Co-dominance
  • Incomplete dominance, leakage, penetrance, expressivity
  • Gene pool
• Meiosis and genetic variability
  • Significance of meiosis
  • Important differences between meiosis and mitosis
  • Segregation of genes
    • Independent assortment
    • linkage
    • recombination
    • single crossovers
    • double crossovers
  • Sex-linked characteristics
    • very few genes on Y chromosome
    • sex determination
    • cytoplasmic inheritance
  • Mutation
    • general concept of mutation-error in DNA sequence
    • types of mutations: random, translation error, transcription error, base substitution, inversion, addition, deletion, translocation, mispairing
    • advantageous vs. deleterious mutation
    • inborn errors of metabolism
    • relationship of mutagens to carcinogens
• Analytic methods
  • Hardy-Weinberg Principle
  • Test cross: back cross, concepts of parental, F1 and F2 generations

Microbiology

• Fungi
  • General characteristics
  • General aspects of life cycle
• Virus structure
  • General structural characteristics (nucleic acid and protein, enveloped and nonenveloped)
  • Lack organelles, nucleus
  • Structural aspects of typical bacteriophage
  • Genomic content RNA or DNA
  • Size relative to bacteria and eukaryotic cells
• Viral life cycle
  • Self-replicating biological units that must reproduce within specific host cell
  • Generalized phage and animal virus life cycles:
    • attachment to host, penetration of cell membrane or cell wall, and entry of viral genetic material
    • use of host synthetic mechanism to replicate viral components
    • self-assembly and release of new viral particles
  • Retrovirus life cycle: integration into host DNA
  • Transduction: transfer of genetic material by viruses
• Prokaryotic cell: structure, bacteria
  • Lack of nuclear membrane, mitotic apparatus
  • Lack of typical eukaryotic organelles
  • Major classifications of bacteria by shape: bacilli (rod-shaped); spirilli (spiral shaped); cocci (spherical); eubacteria; archaea
  • Presence of cell wall in bacteria
  • Flagellar propulsion, mechanism
• Prokaryotic cell: growth and physiology
  • Reproduction by fission
  • High degree of genetic adaptability, acquisition of antibiotic resistance
  • Exponential growth
  • Existence of anaerobic and aerobic variants
  • Parasitic and symbiotic
• Prokaryotic cell: genetics
  • Existence of plasmids, extragenomic DNA, transfer by conjugation
  • Transformation: incorporation into bacterial genome of DNA fragments from external medium
  • Regulation of gene expression, coupling of transcription and translation

Generalized Eukaryotic Cell

• Nucleus and Other Defining Characteristics
  • Defining characteristics (membrane bound nucleus, presence of organelles, mitotic division)
  • Nucleus (compartmentalization, storage of genetic information)
  • Nucleolus (location and function)
  • Nuclear envelope, nuclear pores
• Membrane-bound Organelles
  • Mitochondria
    • site of ATP production
    • self-replication; have own DNA and ribosomes
    • inner and outer membrane
  • Lysosomes (vesicle containing hydrolytic enzymes)
  • Endoplasmic reticulum
    • rough (RER) and smooth (SER)
    • RER (site of ribosomes)
    • role in membrane biosynthesis: SER (lipids), RER (transmembrane proteins)
    • RER (role in biosynthesis of transmembrane and secreted proteins that cotranslationally targeted to RER by signal sequence)
  • Golgi apparatus (general structure; role in packaging, secretion, and modification of glycoprotein carbohydrates)
• Plasma Membrane
  • General function in cell containment
  • Protein and lipid components, fluid mosaic model
  • Osmosis
  • Passive and active transport
  • Membrane channels
  • Sodium-potassium pump
  • Membrane receptors, cell signaling pathways, second messengers
  • Membrane potential
  • Exocytosis and endocytosis
  • Cell-cell communication (General concepts of cellular adhesion)
    • gap junctions
    • tight junctions
    • desmosomes
• Cytoskeleton
  • General function in cell support and movement
  • Microfilaments (composition; role in cleavage and contractility)
  • Microtubules (composition; role in support and transport)
  • Intermediate filaments (role in support)
  • Composition and function of eukaryotic cilia and flagella
  • Centrioles, microtubule organizing centers
• Cell Cycle and Mitosis
  • Interphase and mitosis (prophase, metaphase, anaphase, telophase)
  • Mitotic structures and processes
    • centrioles, asters, spindles
    • chromatids, centromeres, kinetochores
    • nuclear membrane breakdown and reorganization
    • mechanisms of chromosome movement
  • Phases of cell cycle: G0, G1, S, G2, M
  • Growth arrest
• Apoptosis (Programmed Cell Death)

Specialized Eukaryotic Cells and Tissues

• Nerve Cell/Neural
  • Cell body (site of nucleus and organelles)
  • Axon (structure, function)
  • Dendrites (structure, function)
  • Myelin sheath, Schwann cells, oligodendrocytes, insulation of axon
  • Nodes of Ranvier (role in propagation of nerve impulse along axon)
  • Synapse (site of impulse propagation between cells)
  • Synaptic activity
    • transmitter molecules
    • synaptic knobs
    • fatigue
    • propagation between cells without resistance loss
  • Resting potential (electrochemical gradient)
  • Action potential
    • threshold, all-or-none
    • sodium-potassium pump
  • Excitatory and inhibitory nerve fibers (summation, frequency of firing)
• Muscle Cell/Contractile
  • Structural characteristics of striated, smooth, and cardiac muscle (old aamc topic)
  • Abundant mitochondria in red muscle cells (ATP source)
  • Organization of contractile elements (actin and myosin filaments, cross bridges, sliding filament model)
  • Calcium regulation of contraction, sarcoplasmic reticulum
  • Sarcomeres ("I" and "A" bands, "M" and "Z" lines, "H" zone - General structure only)
  • Presence of troponin and tropomyosin
• Other specialized cell types
  • Epithelial cells (cell types, simple epithelium, stratified epithelium)
  • Endothelial cells
  • Connective tissue cells (major cell types, fiber types, loose vs. dense, cartilage, extracellular matrix)

Nervous and Endocrine Systems

• Endocrine system: Hormones
  • Function of endocrine system (specific chemical control at cell, tissue, and organ level)
  • Definition of endocrine gland, hormone
  • Major endocrine glands (names, locations, products)
  • Major types of hormones
• Endocrine system: Mechanisms of hormone action
  • Cellular mechanisms of hormone action
  • Transport of hormones (bloodstream)
  • Specificity of hormones (target tissue)
  • Integration with nervous system (feedback control)
• Nervous System: Structure and Function
  • Major functions
    • high-level control and integration of body systems
    • response to external influences
    • sensory input
    • integrative and cognitive abilities
  • Organization of vertebrate nervous system
  • Sensor and effector neurons
  • Sympathetic and parasympathetic nervous systems (functions, antagonistic control)
  • Reflexes
    • feedback loop, reflex arc, effects on flexor and extensor muscles
    • role of spinal cord, brain
    • efferent control
• Nervous System: Sensory Reception and Processing
  • Skin, proprioceptive, and somatic sensors
  • Olfaction, taste
  • Hearing
    • ear structure
    • mechanism of hearing
  • Vision
    • light receptors
    • eye structure
    • visual image processing

Circulatory, Lymphatic, and Immune Systems

• Circulatory System
  • Functions (circulation of oxygen, nutrients, hormones, ions, and fluids; removal of metabolic waste)
  • Role in thermoregulation
  • Four-chambered heart (structure, function)
  • Systolic and diastolic pressure
  • Pulmonary and systemic circulation
  • Arterial and venous systems (arteries, arterioles, venules, veins)
    • structural and functional differences
    • pressure and flow characteristics
  • Capillary beds
    • mechanisms of gas and solute exchange
    • mechanism of heat exchange
    • source of peripheral resistance (no longer tested)
  • Composition of blood
    • plasma, chemicals, blood cells
    • erythrocyte production and destruction (spleen, bone marrow)
    • regulation of plasma volume
    • coagulation, clotting mechanisms, role of liver in production of clotting factors
  • Oxygen and carbon dioxide transport by blood
    • hemoglobin, hematocrit
    • oxygen content
    • oxygen affinity
  • Details of oxygen transport: biochemical characteristics of hemoglobin
    • modification of oxygen affinity
• Lymphatic System
  • Major functions
    • equalization of fluid distribution
    • transport of proteins and large glycerides
    • production of lymphocytes involved in immune reactions
    • return of materials to the blood
    • Composition of lymph (similarity to blood plasma; substances transported)
    • Source of lymph (diffusion from capillaries by differential pressure)
    • Lymph nodes (activation of lymphocytes)
• Immune system: Innate and Adaptive Systems
  • Cells and their basic functions
    • macrophages, neutrophils, mast cells, natural killer cells, dendritic cells
    • T-lymphocytes
    • B-lymphocytes, plasma cells
  • Tissues
    • bone marrow
    • spleen
    • thymus
    • lymph nodes
  • Basic aspects of innate immunity and inflammatory response
  • Concept of antigen and antibody
  • Structure of antibody molecule
  • Mechanism of stimulation by antigen; antigen presentation

Respiratory System

• General structure and function
  • gas exchange, thermoregulation
  • protection against disease, particulate matter
• Breathing mechanisms
  • diaphragm, rib cage, differential pressure
  • resiliency and surface tension effects

Skin System

• Functions in homeostasis and osmoregulation
• Functions in thermoregulation
  • hair, erectile musculature
  • fat layer for insulation
  • sweat glands, location in dermis
  • vasoconstriction and vasodilation in surface capillaries
• Physical protection
  • nails, calluses, hair
  • protection against abrasion, disease organisms
• Structure
  • layer differentiation, cell types, tissue types (epithelial, connective)
  • relative impermeability to water

Digestive and Excretory Systems

Digestive System

• Ingestion
  • saliva as lubrication and source of enzymes
  • epiglottal action
  • pharynx (function in swallowing)
  • esophagus (transport function)
• Stomach
  • storage and churning of food
  • low pH, gastric juice, protection by mucus against self-destruction
  • production of digestive enzymes, site of digestion
  • structure (gross)
• Liver
  • production of bile
  • role in nutrient metabolism, vitamin storage
  • role in blood glucose regulation, detoxification
  • structure (gross)
• Bile
  • storage in gall bladder
  • function
• Pancreas
  • production of enzymes, bicarbonate
  • transport of enzymes to small intestine
  • structure (gross)
• Small intestine
  • absorption of food molecules and water
  • function and structure of villi
  • production of enzymes, site of digestion
  • neutralization of stomach acid
  • structure (anatomic subdivisions)
• Large intestine
  • anatomic subdivisions (old topic)
  • absorption of water
  • bacterial flora
  • structure (gross)
• Rectum (storage and elimination of waste, feces)
• Muscular control
  • sphincter muscle
  • peristalsis

Excretory System

• Roles in homeostasis
  • blood pressure
  • osmoregulation
  • acid-base balance
  • removal of soluble nitrogenous waste
• Kidney structure
  • cortex
  • medulla
• Nephron structure
  • glomerulus
  • Bowman's capsule
  • proximal tubule
  • loop of Henle
  • distal tubule
  • collecting duct
• Formation of urine
  • glomerular filtration
  • secretion and reabsorption of solutes
  • concentration of urine
  • countercurrent multiplier mechanism (basic function)
• Storage and elimination (ureter, bladder, urethra)

Muscle and Skeletal Systems

• Muscle System
  • Functions
    • support, mobility
    • peripheral circulatory assistance
    • thermoregulation (shivering reflex)
  • Structural characteristics of skeletal, smooth, and cardiac muscle; striated vs nonstriated
  • Nervous control
    • motor neurons
    • neuromuscular junctions, motor end plates
    • voluntary and involuntary muscles
    • sympathetic and parasympathetic innervation
• Skeletal System
  • Functions
    • structural rigidity and support
    • calcium storage
    • physical protection
  • Skeletal structure
    • specialization of bone types, structures
    • joint structures
    • endoskeleton versus exoskeleton
  • Cartilage (structure and function)
  • Ligaments, tendons
  • Bone structure
    • calcium-protein matrix
    • bone growth (osteoblasts, osteoclasts)

Reproductive System and Development

• Reproductive System
  • Male and female reproductive structures and their functions
    • gonads
    • genitalia
    • differences between male and female structures
  • Gametogenesis by meiosis
  • Ovum and sperm
    • differences in formation
    • differences in morphology
    • relative contribution to next generation
  • Reproductive sequence (fertilization, implantation, development, birth)
• Embryogenesis
  • Stages of early development (order and general features of each)
    • fertilization
    • cleavage
    • blastula formation
    • gastrulation
      • first cell movements
      • formation of primary germlayers (endoderm, mesoderm, ectoderm)
    • neurulation
  • Major structures arising out of primary germ layers
• Developmental Mechanisms
  • Cell specialization
    • determination
    • differentiation
    • tissue types
  • Cell communication in development
  • Gene regulation in development
  • Programmed cell death

Evolution

• Evolution
  • Natural selection
    • fitness concept
    • selection by differential reproduction
    • concepts of natural and group selection
    • evolutionary success as increase in percent representation in the gene pool of the next generation
  • Speciation
    • definition of species
    • polymorphism
    • adaptation and specialization
    • concepts of ecological niche, competition
    • concept of population growth through competition
    • inbreeding
    • outbreeding
    • bottlenecks, genetic drift
    • divergent, parallel, and convergent evolution
    • Symbiotic relationships
      • Parasitism
      • Commensalism
      • Mutualism
  • Relationship between ontogeny and phylogeny (Ontogeny recapitulates phylogeny)
  • Evolutionary time as measured by gradual random changes in genome
  • Origin of life
• Comparative anatomy
  • Chordate features
    • notochord
    • pharangeal pouches, branchial arches
    • dorsal nerve cord
  • Vertebrate phylogeny: vertebrate classes and relations to each other

Source: Official MCAT biology topics were obtained directly from the AAMC.