Biology
36%of exam
Human Anatomy
20%of exam
Human Physiology
20%of exam
Health
15%of exam
Chemistry
9%of exam
Quick Facts
- Exam
- NLN NEX Science subject test
- Presented items
- 60: 55 scored, 5 unscored
- Time and format
- 60 minutes; four-option multiple-choice items
- Content level
- Mainly high school; some introductory college
- Scoring
- No guessing penalty; blanks are incorrect
- Admission cutoff
- School sets requirements; no national cutoff
- 2024 science median benchmarks
- RN 69.1%; PN 56.4%; benchmarks
- Retake interval
- 30 days unless school agrees otherwise
- Score storage
- NLN retains records for three years
- Norms: RN and LPN/VN
- Two groups; effective November 2025
Taxonomic Hierarchy
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Broad to narrowGenus capitalised; species lowercaseBinomial uses genus and specific epithet
Mitosis Versus Meiosis
Mitosis
- One division after DNA replication
- Usually two daughter nuclei
- Chromosome number generally maintained
Meiosis
- Two divisions after DNA replication
- Homologous chromosomes separate, then sister chromatids
- Haploid products; oogenesis has unequal products
Oogenesis does not yield four eggs
Osmosis and Transport Decisions
- Lower external nonpenetrating-solute concentration→Predict water entry and swelling(Animal cells may lyse)
- Higher external nonpenetrating-solute concentration→Predict water loss and shrinkage(Concentration alone needs permeability context)
- Small nonpolar molecule crosses membrane→Simple diffusion down its gradient(No direct ATP use)
- Glucose follows gradient through a carrier→Facilitated diffusion(Carrier-mediated does not automatically mean active)
- Na+/K+ pump uses ATP→Primary active transport(3 Na+ outward; 2 K+ inward)
Cells, Organelles and Transport
- Prokaryotic cell
- No membrane-bound nucleus; DNA in nucleoid
- Eukaryotic cell
- Membrane-bound nucleus and organelles
- Rough ER
- Ribosomes; processing many exported proteins
- Smooth ER
- Lipid synthesis; calcium storage; detoxification
- Golgi apparatus
- Modifies, sorts and packages cargo
- Photosynthetic plant cells
- Chloroplasts; roots generally lack them
- Na+/K+ pump
- 3 outward, 2 inward per ATP
- Tonicity
- Depends on effectively nonpenetrating solutes
- Isotonic animal cell
- No net volume change; water exchanges
- Diffusion equilibrium
- Molecules move; net flux is zero
Mitosis PMAT
Prophase condenses; metaphase aligns; anaphase separates; telophase reforms nuclei
Prometaphase: nuclear envelope breaks downMetaphase: chromosomes at equatorAnaphase: sister chromatids separateCytokinesis can overlap mitotic stages
NEX Versus Legacy PAX
Current NEX
- Science has five scored content areas
- No separate physics content domain
- Two program-specific 2024 norm groups
Legacy PAX
- Older science blueprint included physics
- Different reporting conventions and norms
- Old preparation material needs blueprint checking
Use current NEX counts and norms
Division, DNA and Genetics
- Mitosis
- Two nuclei; chromosome number usually maintained
- Meiosis
- Two divisions; chromosome number halved
- Human oogenesis
- One functional ovum; polar bodies
- DNA base pairing
- A–T and G–C
- RNA building units
- Ribonucleotides; uracil usually replaces thymine
- Transcription
- DNA template directs RNA synthesis
- Translation
- Ribosome reads mRNA; assembles amino acids
- Aa × Aa genotypes
- 1 AA : 2 Aa : 1 aa
- Aa × Aa: complete-dominance phenotype
- 3 dominant : 1 recessive
- Each independent birth
- Previous outcomes do not force ratios
Metabolism, Ecology and Classification
- Glycolysis
- Cytosol; net 2 ATP per glucose
- Aerobic electron transport
- Oxygen accepts electrons at pathway end
- Light-dependent reactions
- Thylakoids; ATP, NADPH and oxygen
- Calvin cycle
- Stroma; carbon fixation into carbohydrate precursors
- Broadest and narrowest taxonomic ranks
- Domain and species, respectively
- Natural selection
- Inherited variation affects reproductive success
- Homologous structures
- Shared ancestry; functions can differ
- Analogous structures
- Similar function; evolved independently
- Trophic transfer
- Variable efficiency; 10% is approximate
- Experiment control
- Comparable conditions isolate the tested factor
- Correlation
- Association alone does not establish causation
Heart Flow Versus Oxygen Content
Arteries
- Carry blood away from heart
- Pulmonary arteries carry oxygen-poor blood
- Walls adapted to their pressure conditions
Veins
- Return blood toward the heart
- Pulmonary veins carry oxygen-rich blood
- Many limb veins contain valves
Blood-flow direction defines the vessel class
Heart, Airways and Nervous Structures
- Sagittal plane
- Left and right portions
- Frontal plane
- Anterior and posterior portions
- Transverse plane
- Superior and inferior portions
- Right ventricular outlet
- Pulmonary valve → pulmonary trunk
- Left ventricular outlet
- Aortic valve → aorta
- Tricuspid valve
- Between right atrium and right ventricle
- Mitral valve
- Between left atrium and left ventricle
- Conducting airways
- Trachea → bronchi → bronchioles
- Alveoli
- Thin surfaces for pulmonary gas exchange
- Central nervous system
- Brain and spinal cord
- Myelin-producing cells
- CNS oligodendrocytes; PNS Schwann cells
Skeleton, Digestion and Urinary Anatomy
- Typical adult skeleton
- 206 bones; individual variation exists
- Skeletal ligament
- Usually joins bone to bone
- Tendon
- Attaches muscle to bone
- Cardiac muscle
- Striated, branching cells; intercalated discs
- Smooth muscle
- Nonstriated; many hollow-organ walls
- Small intestine
- Duodenum → jejunum → ileum
- Liver and gallbladder
- Bile production versus storage and release
- Pancreas
- Digestive secretions; endocrine islet hormones
- Nephron filtrate
- Bowman’s capsule, tubule, then collecting system
- Urine outflow
- Ureter → bladder → urethra
- Thyroid location
- Anterior neck, around upper trachea
Skin, Reproduction and Senses
- Skin proper
- Epidermis and dermis; hypodermis below
- Sweat glands
- Exocrine secretion onto skin surface
- Usual human fertilisation site
- Ampulla of uterine tube
- Usual embryo implantation site
- Uterine endometrium
- Ovary and testis
- Oocytes and sperm; sex hormones
- Retinal rods
- High sensitivity in dim light
- Retinal cones
- Colour vision and finer detail
- Cochlea
- Hearing; hair cells transduce vibration
- Vestibular apparatus
- Senses head movement and position
- Lymphatic system
- Fluid return and immune functions
Cardiac Output Calculation
Rate times volume per beat gives volume per minute
Rate × stroke volume = output4,900 mL/min = 4.9 L/minExample values, not diagnostic thresholds
Sympathetic Versus Parasympathetic
Sympathetic
- Often raises heart rate
- Often dilates pupils
- Most postganglionic fibres release norepinephrine
Parasympathetic
- Often slows heart rate
- Often supports digestive activity
- Postganglionic fibres release acetylcholine
Effects vary by organ and receptor
Homeostasis Decisions
- Blood glucose rises after a meal→Insulin supports uptake and storage(Beta cells secrete insulin)
- Blood glucose falls between meals→Glucagon supports hepatic glucose output(Alpha cells secrete glucagon)
- Plasma osmolarity rises with dehydration→ADH increases renal water reabsorption(Normal regulatory response, not treatment advice)
- Blood calcium falls→PTH helps restore calcium(Multiple tissues contribute)
- Thoracic volume rises during quiet inspiration→Alveolar pressure briefly falls(Air enters from higher atmospheric pressure)
- Na+ channels open during neuronal depolarisation→Na+ usually moves inward(Electrochemical gradient supplies the driving force)
Feedback, Conduction and Hormones
- Negative feedback
- Response opposes the initial deviation
- Positive feedback
- Response amplifies change until termination
- Cardiac output
- Heart rate × stroke volume
- Cardiac conduction
- SA, AV, His, then Purkinje fibres
- Quiet inspiration
- Thoracic volume rises; alveolar pressure falls
- Central respiratory chemoreception
- CO2 alters cerebrospinal-fluid pH
- Neuronal depolarisation
- Typically voltage-gated Na+ influx
- Neuronal repolarisation
- Typically increased K+ efflux
- ADH synthesis and release
- Hypothalamus makes; posterior pituitary releases
- Insulin and glucagon
- Beta lowers glucose; alpha supports elevation
- PTH
- Raises blood calcium through coordinated effects
Humoral Versus Cell-Mediated Immunity
B-cell roles
- Mature in bone marrow
- Activated plasma cells secrete antibodies
- Antibodies can neutralise extracellular targets
T-cell roles
- Mature in the thymus
- Helper T cells coordinate responses
- Cytotoxic T cells kill infected cells
Both cooperate; division is not absolute
Kidneys, Digestion, Muscle and Immunity
- ADH effect
- Increases collecting-system water permeability
- Aldosterone effect
- Promotes sodium retention and potassium secretion
- Glucose reabsorption
- Limited by tubular transport capacity
- Bile
- Emulsifies lipids; not a digestive enzyme
- Lipase
- Hydrolyses fats into absorbable components
- Skeletal-muscle calcium
- Binds troponin; permits cross-bridge access
- ATP binding to myosin
- Detaches myosin from actin
- ATP hydrolysis
- Helps reset the myosin head
- Innate defences
- Barriers, phagocytes and inflammatory responses
- Plasma cells
- Secrete antibodies after B-cell activation
- T-cell maturation
- Thymus; helpers coordinate, cytotoxic cells kill
- Adaptive memory
- Faster responses after suitable prior exposure
Fat-Soluble ADEK
A, D, E and K are fat-soluble vitamins
A: supports visionD: supports calcium absorptionE: antioxidant functionsK: supports clotting-factor activation
Bacteria Versus Viruses
Bacteria
- Prokaryotic cells
- Most have peptidoglycan walls; exceptions exist
- Some infections need clinician-selected antibiotics
Viruses
- Acellular genetic material within protective structures
- Depend on host cells for reproduction
- Antibiotics do not treat viruses
Symptoms alone cannot establish pathogen identity
Prevention and Immunity Decisions
- Vaccination before the target disease→Primary prevention(Aims to reduce disease onset)
- Screening for early disease→Secondary prevention(Positive findings may require confirmation)
- Rehabilitation after established disease→Tertiary prevention(Reduces disability or other consequences)
- Maternal IgG crosses the placenta→Natural passive immunity(Preformed antibodies; temporary protection)
- Vaccination stimulates the recipient’s response→Artificial active immunity(Memory may develop)
- Same antigen produces faster later response→Adaptive immune memory(Protection is not an absolute guarantee)
Prevention, Immunity and Nutrition
- Primary prevention
- Prevents onset; vaccination is one example
- Secondary prevention
- Early detection; screening is one example
- Tertiary prevention
- Limits established disease’s impact; rehabilitation
- Active immunity
- Recipient responds; memory can develop
- Passive immunity
- Preformed antibodies; no recipient memory generated
- Community immunity
- Depends on reduced transmission; not universal
- Carbohydrate and protein
- Approximately 4 kcal/g each
- Fat
- Approximately 9 kcal/g
- Fat-soluble vitamins
- A, D, E and K
- Vitamin B12
- Water-soluble but stored for years
- Fruit juice sugars
- Free sugars, even without added sugar
Health, Access and Everyday Safety
- Health dimensions
- Physical, mental, social, emotional and spiritual
- Health inequity
- Avoidable, unfair difference in health opportunities
- Substance use disorder
- Health condition; moral blame is inadequate
- Home food safety
- Clean, separate, cook and chill
- Cross-contamination
- Raw food transfers hazards to ready-to-eat
- Poultry internal temperature
- FDA: 165 °F, approximately 74 °C
- Food appearance
- Normal appearance does not establish safety
- Screening result
- May need confirmation; not automatic diagnosis
- Emergency with an unsafe scene
- Avoid danger; alert emergency services
- First-aid actions
- Follow training and emergency-dispatch instructions
Oxidation and Reduction
OIL RIG: Oxidation Is Loss; Reduction Is Gain
The transferred particles are electronsOxidation and reduction occur togetherOxidation number rises during oxidation
Chemistry Condition Checks
- Oppositely charged ions attract→Ionic bonding(NaCl is a familiar example)
- Bonded atoms share electrons unequally→Polar covalent bonding(Water contains polar covalent bonds)
- Dilution without solute loss or reaction→Use M₁V₁ = M₂V₂(Same concentration basis and volume units)
- Gas amount and temperature stay fixed→Use P₁V₁ = P₂V₂(Absolute pressure; ideal-gas approximation)
- pH decreases by two units→Hydrogen-ion activity increases 100-fold(Not a 2-fold change)
- A catalyst is added at equilibrium→Equilibrium composition stays the same(Forward and reverse pathways accelerate)
Atoms, Bonds, Gases and Solutions
- Atomic number Z
- Number of protons
- Mass number A
- Protons plus neutrons in one isotope
- Neutron number
- A − Z
- Isotopes
- Same element; different neutron numbers
- Ions
- Net charge; electron count differs
- Polar covalent bond
- Electrons shared unequally
- Ionic bond
- Attraction between oppositely charged ions
- Hydrogen bonding
- Suitable partial charges; intra- or intermolecular
- Boyle: fixed amount and temperature
- P₁V₁ = P₂V₂; use absolute pressure
- Charles: fixed amount and pressure
- V₁/T₁ = V₂/T₂; kelvin temperatures
- Molarity
- Moles of solute per solution litre
- Dilution without reaction or loss
- M₁V₁ = M₂V₂; solute amount conserved
- Emulsion
- Droplets dispersed in another immiscible liquid
pH, Reactions and Catalysts
- pH definition
- Negative logarithm of hydrogen-ion activity
- One pH unit
- Tenfold hydrogen-ion activity difference
- pH 4 versus pH 6
- 100-fold hydrogen-ion activity difference
- Neutral water at 25 °C
- Approximately pH 7; temperature matters
- Buffer
- Resists small additions of acid/base
- Oxidation
- Loss of electrons
- Reduction
- Gain of electrons
- Exothermic change
- Releases heat to surroundings
- Endothermic change
- Absorbs heat from surroundings
- Catalyst
- Lowers activation barrier; equilibrium unchanged
- Acid–hydroxide neutralisation
- Often produces salt and water
- Physical versus chemical change
- State change versus changed chemical composition
Common Traps
Percent Correct Versus Percentile
Percent correct: fraction of 55 scored ≠ Percentile: position within specified norm group
Qualifying Versus Admission
Meeting a school’s threshold ≠ Guaranteed admission to that program
Content Outline Versus Current Cognitive Blueprint
2024 manual: detailed content topics ≠ January 2026: current Table 4 cognition
Overlapping Skills Versus Extra Domain
Application/interpretation: overlapping logic and reasoning ≠ Separate extra reasoning-weighted domain
Human Oogenesis Versus Equal Functional Products
Completed oogenesis: one ovum, polar bodies ≠ Four equivalent functional ova
Chromosome Sets Versus Developmental Equivalence
Haploid: one chromosome set ≠ Equivalent cytoplasm or developmental fate
Bile Versus Lipase
Bile: physical emulsification of fat droplets ≠ Lipase: chemical hydrolysis of fats
Bile Production Versus Storage
Liver: produces bile ≠ Gallbladder: stores and concentrates bile
Independent Versus Dependent Variable
Manipulated exposure: independent variable ≠ Measured response: dependent variable
Variable Role Versus Axis Convention
Independent variable: study role ≠ Horizontal axis: plotting convention
Bacterial Versus Viral Infection
Susceptible bacterial infection: antibiotics may help ≠ Viral infection: antibiotics do not treat
Bacterial Cause Versus Automatic Antibiotic Need
Bacterial infection: indication still needs assessment ≠ Any bacterial infection: automatic antibiotic need
Actual Prescription Versus Universal Course
Actual prescription: individualized instructions ≠ One universal antibiotic course for everyone
Acidemia Versus Acidosis
Acidemia: arterial pH below 7.35 ≠ Acidosis: acidifying physiological process
Observed Result Versus Established Cause
Abnormal pH: observed result ≠ Established underlying cause: further clinical evidence
Boyle Versus Charles Conditions
Boyle: fixed amount and temperature ≠ Charles: fixed amount and pressure
Absolute Versus Celsius Temperature
Kelvin: absolute temperature ≠ Celsius: temperature with arbitrary zero
Absolute Versus Gauge Pressure
Absolute pressure: referenced to vacuum ≠ Gauge pressure: referenced to ambient pressure
Last Minute
- 1.60 presented; 55 scored; 60 minutes
- 2.Biology: 20 of 55 scored items
- 3.Anatomy and physiology: 11 items each
- 4.Chemistry: 5 items; Health: 8
- 5.Knowledge 25; application 18; interpretation 12
- 6.Blanks score incorrect; no guessing penalty
- 7.School determines cutoff and score recency
- 8.Current norms use two program groups
- 9.Hypotonic animal cells gain water
- 10.Arteries go away; veins return blood
- 11.Bile emulsifies; enzymes perform chemical digestion
- 12.Cardiac output = rate × stroke volume
- 13.pH difference 2 means 100-fold activity
- 14.Trophic transfer efficiency varies by system
- 15.Screening findings may require diagnostic confirmation
- 16.Association alone does not establish causation
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