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2.1 Life Science: Cell Biology, Human Anatomy & Genetics
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1 Chapter 1: Guide Scope, AFQT & Service-Specific Policy
1.1 Editorial Scope and Service-Specific AFCT Policy 1.2 AFQT Meaning and Study Priorities 1.3 Service Composites and Targeted Skill Planning 1.4 Format-Agnostic Test Preparation and Pacing
2 Chapter 2: General Science (GS)
2.1 Life Science: Cell Biology, Human Anatomy & Genetics 2.2 Physical Science: Matter, Energy, Forces & Motion 2.3 Earth & Space Science: Geology, Meteorology & Astronomy 2.4 Chemistry Fundamentals: Atomic Structure, Elements & Chemical Reactions
3 Chapter 3: Arithmetic Reasoning (AR)
3.1 Word Problems: Rates, Ratios, Proportions & Percentages 3.2 Financial & Distance Math: Interest, Profit/Loss, Speed & Time 3.3 Work & Mixture Problems: Joint Rates & Percentage Concentrations 3.4 Multi-Step Problem Solving & Algebraic Word Problems
4 Chapter 4: Word Knowledge (WK)
4.1 General Academic & Technical Vocabulary 4.2 Context Clues, Synonyms & Antonyms 4.3 Word Roots, Prefixes & Suffixes (Etymology) 4.4 Advanced Technical & Operational Terminology
5 Chapter 5: Paragraph Comprehension (PC)
5.1 Identifying Main Ideas, Central Themes & Topic Sentences 5.2 Extracting Supporting Details & Factual Information 5.3 Drawing Logical Inferences & Author's Purpose 5.4 Analyzing Text Structure & Drawing Conclusions
6 Chapter 6: Mathematics Knowledge (MK)
6.1 Pre-Algebra & Number Operations: Exponents, Radicals & Order of Operations 6.2 High School Algebra: Linear Equations, Inequalities & Polynomials 6.3 Geometry Fundamentals: Angles, Triangles, Quadrilaterals & Circles 6.4 Coordinate Geometry, Perimeter, Area & Volume Formulas
7 Chapter 7: Electronics Information (EI)
7.1 Electrical Principles: Voltage, Current, Resistance & Ohm's Law (V=IR, P=VI) 7.2 Electric Circuits: Series, Parallel & Combination Circuit Analysis 7.3 Electrical Components: Resistors, Capacitors, Inductors & Transformers 7.4 Electronic Semiconductors, Transistors, Diodes & Logic Gates
8 Chapter 8: Auto & Shop Information (AS)
8.1 Automotive Systems: Internal Combustion Engines, Fuel & Ignition Systems 8.2 Automotive Mechanical Systems: Transmission, Suspension, Brakes & Cooling 8.3 Hand & Power Tools: Identification, Uses & Fasteners 8.4 Shop Practice, Woodworking, Metalworking & Safety Rules
9 Chapter 9: Mechanical Comprehension (MC)
9.1 Simple Machines: Levers, Pulleys, Inclined Planes & Mechanical Advantage 9.2 Force, Motion, Work & Power: Newton's Laws & Energy Transformations 9.3 Fluid Dynamics & Pressure: Pascal's Principle, Hydraulics & Pneumatics 9.4 Mechanical Components: Gears, Belts, Springs & Friction
10 Chapter 10: Spatial Assembly Practice (AO Skill)
10.1 Spatial Connections and Assembly Patterns
2.1 Life Science: Cell Biology, Human Anatomy & Genetics
Key Takeaways Explain This Topic AI
Cells are the fundamental units of life, categorized into prokaryotic (no membrane-bound nucleus) and eukaryotic (containing a distinct nucleus and membrane-bound organelles).
Photosynthesis converts light energy into chemical energy stored in glucose ( 6 C O 2 + 6 H 2 O + light → C 6 H 12 O 6 + 6 O 2 6CO_2 + 6H_2O + \text{light} \rightarrow C_6H_{12}O_6 + 6O_2 6 C O 2 + 6 H 2 O + light → C 6 H 12 O 6 + 6 O 2 ), while cellular respiration breaks down glucose to generate ATP energy ( C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O + 36 – 38 ATP C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36\text{--}38\text{ ATP} C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O + 36 – 38 ATP ).
Mitosis produces two genetically identical diploid ( 2 n 2n 2 n ) daughter cells for growth and repair; meiosis produces four genetically diverse haploid ( 1 n 1n 1 n ) gametes for sexual reproduction.
The human body maintains internal homeostasis through 11 major organ systems, including the circulatory, respiratory, digestive, nervous, and endocrine systems.
Mendelian genetics relies on dominant and recessive alleles; a monohybrid cross of two heterozygous parents ( B b × B b Bb \times Bb B b × B b ) yields a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio.
Last updated: July 2026
Life Science: Cell Biology, Human Anatomy & Genetics
Life Science forms a cornerstone of the General Science skill area. Candidates are evaluated on fundamental biological principles ranging from micro-level cellular biochemistry to macro-level human anatomy, genetics, and ecological taxonomy.
1. Cell Biology & Cellular Organization
All living organisms are composed of cells , the structural and functional units of life. Life is divided broadly into two cellular architecture types:
Prokaryotes : Primitive single-celled organisms (such as bacteria and archaea) that lack a membrane-bound nucleus and membrane-bound organelles. Their genetic material floats freely in a nucleoid region.
Eukaryotes : Complex single-celled or multicellular organisms (animals, plants, fungi, protists) possessing a membrane-bound nucleus containing DNA, as well as specialized internal structures called organelles .
Essential Cellular Organelles
- Organelle Function Found In
- Nucleus Contains genetic material (DNA); directs cell activities and protein synthesis Plant & Animal cells
- Mitochondria "Powerhouse of the cell"; site of cellular respiration producing ATP energy Plant & Animal cells
- Ribosomes Synthesizes proteins by translating mRNA sequences All cells (Prokaryote & Eukaryote)
Endoplasmic Reticulum (ER) Rough ER (studded with ribosomes) synthesizes proteins; Smooth ER synthesizes lipids & detoxifies toxins Plant & Animal cells
Golgi Apparatus Modifies, sorts, and packages proteins and lipids for storage or export Plant & Animal cells
Lysosomes Contains digestive enzymes to break down waste, cellular debris, and foreign pathogens Primarily Animal cells
Vacuoles Storage sacs for water, nutrients, and waste; plant cells contain one large Central Vacuole Plant (large) & Animal (small)
Chloroplasts Site of photosynthesis; contains chlorophyll to convert sunlight into glucose Plant cells & Algae
Cell Membrane (Plasma Membrane) Semi-permeable phospholipid bilayer that regulates entry and exit of substances All cells
Cell Wall Rigid outer layer made of cellulose (plants) or chitin (fungi) providing structure and support Plant, Fungal & Bacterial cells
2. Cellular Energy & Metabolism
Cells require energy to perform work, maintain homeostasis, and grow. Two primary metabolic pathways govern energy conversion in living systems:
Photosynthesis
Photosynthesis is an anabolic, endergonic process occurring in plant chloroplasts. Autotrophs capture light energy to convert carbon dioxide and water into glucose and oxygen gas. Chemical Equation: 6 C O 2 + 6 H 2 O + Light Energy → C 6 H 12 O 6 + 6 O 2 \text{Chemical Equation: } 6CO_2 + 6H_2O + \text{Light Energy} \rightarrow C_6H_{12}O_6 + 6O_2 Chemical Equation: 6 C O 2 + 6 H 2 O + Light Energy → C 6 H 12 O 6 + 6 O 2
Light-Dependent Reactions : Occur in the thylakoid membranes; split water molecules ( H 2 O H_2O H 2 O ), release O 2 O_2 O 2 , and produce ATP and NADPH.
Calvin Cycle (Light-Independent Reactions) : Occurs in the stroma; utilizes ATP and NADPH to fix C O 2 CO_2 C O 2 into glucose ( C 6 H 12 O 6 C_6H_{12}O_6 C 6 H 12 O 6 ).
Cellular Respiration
Cellular respiration is a catabolic, exergonic process occurring in eukaryotic mitochondria. Heterotrophs and autotrophs break down glucose in the presence of oxygen to generate adenosine triphosphate (ATP) . Chemical Equation: C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O + 36 – 38 ATP \text{Chemical Equation: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + 36\text{--}38\text{ ATP} Chemical Equation: C 6 H 12 O 6 + 6 O 2 → 6 C O 2 + 6 H 2 O + 36 – 38 ATP
Glycolysis : Occurs in the cytoplasm; splits one 6-carbon glucose into two 3-carbon pyruvate molecules (Yields 2 ATP + 2 NADH 2\text{ ATP} + 2\text{ NADH} 2 ATP + 2 NADH ). Requires no oxygen (anaerobic).
Krebs Cycle (Citric Acid Cycle) : Occurs in the mitochondrial matrix; oxidizes acetyl-CoA to release C O 2 CO_2 C O 2 (Yields 2 ATP 2\text{ ATP} 2 ATP , NADH, and F A D H 2 FADH_2 F A D H 2 ).
Electron Transport Chain (ETC) : Occurs on the inner mitochondrial membrane (cristae); uses oxygen as the final electron acceptor to generate the bulk of cellular energy via oxidative phosphorylation (Yields ∼ 32 – 34 ATP \sim 32\text{--}34\text{ ATP} ∼ 32 – 34 ATP ).
Anaerobic Respiration (Fermentation) : In the absence of oxygen, cells undergo fermentation. Yeast perform alcoholic fermentation (producing ethanol and C O 2 CO_2 C O 2 ), while human muscle cells undergo lactic acid fermentation during intense effort, producing lactic acid and 2 ATP 2\text{ ATP} 2 ATP .
3. Cell Division & Reproduction: Mitosis vs. Meiosis
Organisms reproduce and repair tissues through coordinated nuclear division processes: Mitosis: [Parent 2n] ---> [Daughter 2n] + [Daughter 2n] (Identical Somatic Cells)
Meiosis: [Parent 2n] ---> [Gamete 1n] [Gamete 1n] [Gamete 1n] [Gamete 1n] (Diverse Gametes)
- Feature Mitosis Meiosis
- Purpose Growth, tissue repair, asexual reproduction Sexual reproduction (gamete formation)
- Location Somatic (body) cells Germ cells in gonads (testes & ovaries)
- Divisions 1 nuclear division 2 nuclear divisions (Meiosis I & II)
- Daughter Cells 2 identical diploid ( 2 n 2n 2 n ) cells 4 unique haploid ( 1 n 1n 1 n ) cells
- Human Chromosome Count 46 chromosomes (23 pairs) 23 single chromosomes
- Genetic Variation None (clones of parent) High (due to crossing over & independent assortment)
- Phases of Mitosis (PMAT)
Prophase : Chromatin condenses into visible chromosomes; nuclear envelope breaks down; spindle fibers form.
Metaphase : Chromosomes line up along the equator (metaphase plate) of the cell.
Anaphase : Sister chromatids are pulled apart by spindle fibers to opposite poles.
Telophase : Nuclear envelopes reform around separated chromatids; chromosomes uncoil back into chromatin.
Cytokinesis : Division of the cytoplasm, yielding two distinct daughter cells.
- 4. Genetics & Molecular Biology
- DNA and RNA Structure
Deoxyribonucleic acid ( DNA ) holds the master genetic code in a double-helix structure composed of nucleotide monomers (a sugar-phosphate backbone and nitrogenous bases).
DNA Nitrogenous Bases : Adenine ( A ), Thymine ( T ), Cytosine ( C ), Guanine ( G ). Base pairing rules: A-T and C-G .
RNA Differences : Ribonucleic acid ( RNA ) is single-stranded, contains ribose sugar instead of deoxyribose, and replaces Thymine with Uracil (U) (pairing A-U and C-G ).
Central Dogma of Molecular Biology : DNA → Transcription mRNA → Translation Protein \text{DNA} \xrightarrow{\text{Transcription}} \text{mRNA} \xrightarrow{\text{Translation}} \text{Protein} DNA Transcription mRNA Translation Protein .
Mendelian Inheritance
Gregor Mendel established fundamental inheritance laws using pea plants:
Gene : A segment of DNA encoding a specific trait.
Allele : Alternative forms of a gene (e.g., B B B for brown eyes, b b b for blue eyes).
Genotype : The genetic makeup of an organism ( B B BB BB = homozygous dominant, B b Bb B b = heterozygous, b b bb bb = homozygous recessive).
Phenotype : The observable physical characteristics resulting from the genotype.
Punnett Square Example ( B b × B b Bb \times Bb B b × B b Monohybrid Cross):
- B b
- B BB (Brown) Bb (Brown)
- b Bb (Brown) bb (Blue)
Genotypic Ratio : 1 B B : 2 B b : 1 b b 1\,BB : 2\,Bb : 1\,bb 1 BB : 2 B b : 1 bb (25% B B BB BB , 50% B b Bb B b , 25% b b bb bb ).
Phenotypic Ratio : 3 Brown eyes : 1 Blue eye (75% dominant, 25% recessive).
5. Human Anatomy & Physiology: Major Body Systems
The human body contains 11 major organ systems working interdependently to sustain life:
System Major Organs / Structures Primary Functions
Circulatory (Cardiovascular) Heart, arteries, veins, capillaries, blood Transports oxygen, nutrients, hormones, and metabolic wastes throughout the body
Respiratory Nasal cavity, trachea, bronchi, lungs, alveoli Exchanges oxygen ( O 2 O_2 O 2 ) and carbon dioxide ( C O 2 CO_2 C O 2 ) between air and blood
Digestive Mouth, esophagus, stomach, small/large intestines, liver, pancreas Mechanical and chemical breakdown of food; nutrient absorption and waste elimination
Nervous Brain, spinal cord, peripheral nerves, sensory receptors Controls voluntary/involuntary responses; processes sensory input and sends electrical signals
Endocrine Pituitary, thyroid, adrenal glands, pancreas, ovaries/testes Secretes hormones into the bloodstream to regulate metabolism, growth, and mood
Musculoskeletal Skeletal muscles, bones (206 in adult), cartilage, tendons, ligaments Provides structural support, protects internal organs, produces blood cells (bone marrow), enables movement
Immune / Lymphatic White blood cells, lymph nodes, spleen, thymus, lymphatic vessels Defends against pathogens; returns excess fluid to the bloodstream
Excretory (Urinary) Kidneys, ureters, urinary bladder, urethra Filters metabolic wastes and excess fluid from blood to form urine; regulates fluid/electrolyte balance
Integumentary Skin, hair, nails, sweat glands Outer protective barrier; regulates body temperature and synthesizes Vitamin D
Reproductive Testes, prostate (male); Ovaries, uterus, fallopian tubes (female) Produces gametes (sperm/eggs) and sex hormones to propagate the species
6. Biological Taxonomy & Classification
Taxonomy is the science of naming and classifying living organisms into hierarchical categories based on evolutionary relationships:
- Domain (Archaea, Bacteria, Eukarya)
- Kingdom (Animalia, Plantae, Fungi, Protista, Eubacteria, Archaebacteria)
- Phylum
- Class
- Order
- Family
- Genus
- Species
Mnemonic for Taxonomy Hierarchy : D ear K ing P hilip C ame O ver F or G ood S oup ( D omain, K ingdom, P hylum, C lass, O rder, F amily, G enus, Species ).
Binomial Nomenclature : Organisms are formally named by their Genus (capitalized) and species (lowercase), written in italics (e.g., Homo sapiens for humans, Canis lupus for wolves).