Core Biology Review

Overview

This lecture provides a comprehensive, high-yield review of core biology concepts, spanning cellular biology, reproduction, physiology, organ systems, genetics, and evolution, emphasizing key definitions and structures for exam preparation.

The Cell and Cell Theory

• All living things are composed of cells, the basic functional unit of life, arising only from pre-existing cells.
• Eukaryotes have a true, membrane-bound nucleus and organelles; prokaryotes lack these and have circular, naked DNA.
• The cell membrane is a phospholipid bilayer with hydrophilic heads and hydrophobic tails.
• DNA is found in chromosomes within the nucleus; mitochondria in the cytoplasm produce ATP.
• Organelles: Mitochondria (energy), lysosome (digestion), endosome (transport), rough ER (protein synthesis), smooth ER (fat synthesis, detox), Golgi (sorting/delivery), peroxisome (fat breakdown).

Cytoskeleton and Tissue Types

• Cytoskeleton: microfilaments (actin), microtubules (tubulin, cilia/flagella), intermediate filaments (tissue-specific).
• Four tissue types: epithelial (lining, glands), connective (support, structure), muscle, and nerve tissues.

Cell Division and Cycle

• Cell cycle phases: G0 (rest), G1 (growth), S (DNA replication), G2 (growth), M (mitosis/meiosis).
• Mitosis yields two identical 2N cells; meiosis yields four genetically unique N cells.
• Cell cycle checkpoints (G1/S, G2/M, metaphase) prevent propagation of DNA errors.

Reproduction, Embryology, and Stem Cells

• Male gametes: sperm (spermatogenesis); female: ovum (oogenesis, arrested in prophase I and metaphase II).
• Fertilization occurs when sperm meets the secondary oocyte (metaphase II); forms a zygote (46 chromosomes).
• Embryonic development: cleavage, blastulation, implantation, gastrulation (ectoderm, mesoderm, endoderm).
• Stem cells: totipotent (any cell), pluripotent (many cells), multipotent (few cells), unipotent (one type).

Nervous System

• CNS (brain, spinal cord) vs. PNS (nerves); neurons are the structural unit, reflex arc is the functional unit.
• Action potential: sodium influx (depolarization), potassium efflux (repolarization), unidirectional signal.
• Myelination: CNS by oligodendrocytes, PNS by Schwann cells; increases conduction speed.

Endocrine System

• Hypothalamus controls anterior pituitary, which regulates thyroid (TSH), adrenal cortex (ACTH), gonads (FSH/LH).
• Posterior pituitary releases ADH (water reabsorption) and oxytocin (milk ejection).
• Insulin (anabolic, lowers glucose), glucagon (catabolic, raises glucose).

Respiratory System

• Conducting vs. respiratory zones; gas exchange occurs in respiratory zone.
• Ventilation follows Boyle's Law (volume ↑, pressure ↓).
• Surfactant (from type II pneumocytes) reduces lung surface tension; oxygen-hemoglobin curve shifts reflect tissue oxygen delivery.

Cardiovascular System

• Heart cycle: systole (ventricular contraction), diastole (relaxation).
• Cardiac output = heart rate x stroke volume.
• Arteries, veins, and capillaries differ in structure and function.
• Blood composed of plasma (albumin for oncotic pressure) and cells (RBCs, WBCs, platelets).

Immune and Lymphatic Systems

• Innate immunity (non-specific) vs. adaptive immunity (B, T lymphocytes).
• Antigen presentation leads to antibody production and memory cell formation.
• Lymph nodes: cortex (B cells), paracortex (T cells), medulla (plasma cells, macrophages).

Digestive System

• Digestion breaks down macronutrients for absorption; absorption routes differ for water- and fat-soluble nutrients.
• GI tract layers: mucosa, submucosa, muscularis, serosa.
• Key digestive hormones: gastrin (stomach), secretin (bicarbonate), CCK (enzyme release, gallbladder contraction).

Renal System & Skin

• Nephron: filtration (Bowman's capsule), reabsorption/secretion (tubules), excretion (urine).
• Skin: epidermis (ectoderm), dermis (mesoderm), stratum basale (stem cell layer), thermoregulation.

Musculoskeletal System

• Muscle types: skeletal (voluntary), cardiac, smooth (involuntary).
• Muscle contraction: actin & myosin slide; ATP required.
• Bone: type I collagen; cartilage: type II collagen; osteoblasts build, osteoclasts resorb.

Genetics and Evolution

• Mendelian inheritance: dominance, segregation (anaphase I), independent assortment (prophase I).
• Mutations: missense (sickle cell), nonsense (stop codon).
• Hardy-Weinberg: allele (p, q) and genotype (p², 2pq, q²) frequencies.
• Evolution: natural selection is a mechanism, not synonymous; reproductive isolation can be pre- or post-zygotic.

Key Terms & Definitions

• Eukaryote — Cell with a true nucleus and membrane-bound organelles.
• Mitosis — Cell division yielding two identical diploid (2N) cells.
• Meiosis — Cell division yielding four non-identical haploid (N) gametes.
• Action Potential — Rapid change in membrane potential enabling nerve impulse transmission.
• Surfactant — Lung secretion reducing surface tension to prevent alveolar collapse.
• Oncotic Pressure — Osmotic pressure exerted by plasma proteins (e.g., albumin).
• Zygote — Fertilized egg cell (46 chromosomes).

Action Items / Next Steps

• Pause and review provided diagrams or slides on organelles, cell cycle, embryology, and cardiovascular cycles.
• Complete practice problems on genetics, Punnett squares, and Hardy-Weinberg calculations.
• Memorize tissue types, hormone functions, and phases of the menstrual and cardiac cycles.