Ultimate Biology Review

Introduction

• Biology review in less than 90 minutes
• Topics covered: cell, reproduction, embryogenesis, nervous system, endocrine system, respiratory system, cardiovascular system, immune system, digestive system, homeostasis, musculoskeletal system, genetics, evolution

The Cell

Cell Theory

• Types: Prokaryotes vs. Eukaryotes
  • Prokaryotes: no true nucleus, circular DNA (e.g., bacteria)
  • Eukaryotes: true nucleus, linear DNA (e.g., mammals/humans)
• Four tenets
  1. All living things composed of cells
  2. Cells are the basic unit of life
  3. Cells arise from pre-existing cells
  4. Cells carry genetic information in DNA

Cell Structure

• Nucleus: control room, contains DNA organized in chromosomes
• Cytoplasm: organelles + cytosol (fluid)
• Plasma membrane: lipid bilayer (phospholipid), hydrophilic heads, hydrophobic tails
• Protoplasm: nucleus + cytoplasm

Organelles

• Mitochondria: Powerhouse, ATP production, contains mitochondrial DNA
• Lysosome: Destroyer, contains hydrolytic enzymes
• Endoplasmic Reticulum (ER): rough (protein synthesis), smooth (fat synthesis, detoxification)
• Golgi Apparatus: Sorter, modifies and directs cellular products
• Peroxisome: Destroys fat, involved in beta-oxidation
• Cytoskeleton: Structural support, involved in cell movement and division
• Types of Cytoskeleton: microfilaments (actin), microtubules (tubulin), intermediate filaments

Cell Cycle

• G0: Resting phase
• G1: Growth phase 1
• S: DNA synthesis
• G2: Growth phase 2
• M: Mitosis or Meiosis (division)
• Checkpoints: G1-S, G2-M, Metaphase
• Cancer & Chemotherapy: Uncontrolled cell division, Chemo stops cell division

Reproduction

• Male: spermatogenesis (sperm production), followed by spermiogenesis
• Female: oogenesis (ovum production)
• Fertilization: Secondary oocyte + sperm, completes meiosis II
• Menstrual Cycle Phases: Proliferation (estrogen), Secretory (progesterone), Menstruation (everything drops)
• Fertilization Steps: capacitation, acrosomal reaction, polyspermy block, completion of meiosis II, zygote formation

Nervous System

Central Nervous System (CNS)

• Brain, Spinal Cord
• Gray matter vs. white matter
• Functional/Structural Units: Neuron (functional), Reflex arc (functional)

Peripheral Nervous System (PNS)

• Cranial nerves, Spinal nerves
• Somatic (voluntary) vs. Autonomic (involuntary)
  • Sympathetic: Fight or flight
  • Parasympathetic: Rest and digest
• Myelin: produced by Oligodendrocytes (CNS) and Schwann cells (PNS)
• Action Potential: Resting (potassium out), Depolarization (sodium in), Repolarization (potassium out again)

Endocrine System

• Hypothalamus, Pituitary (Anterior & Posterior)
• Hormones: TSH, ACTH, FSH, LH, Prolactin, Growth Hormone
• Adrenal gland: Cortex (aldosterone, cortisol, adrenal androgens), Medulla (catecholamines)
• Pancreas: Exocrine (digestive enzymes), Endocrine (insulin, glucagon)
• Feedback loops and hormone actions

Respiratory System

Anatomy

• Conducting Zone vs. Respiratory Zone
• Pleura: visceral and parietal layers

Function

• Inhalation/Exhalation: Negative pressure pulls air in, positive pressure expels air
• Gas exchange: Alveoli
• Pulmonary Function Tests & Lung Volumes
• Acidosis/Alkalosis: Metabolic vs. Respiratory

Cardiovascular System

Anatomy

• Heart chambers, valves, and major vessels
• Circulatory pathways: systematic, pulmonary, fetal
• Blood pressure, cardiac cycle, systole/diastole
• Blood cells: RBCs (no nucleus/mitochondria), WBCs, platelets
• Plasma: water, proteins (albumin, globulin)

Function

• Capillary dynamics: hydrostatic vs. oncotic pressure
• Respiratory and Metabolic Links: Oxygen transport, CO2 excretion

Immune System

• Innate vs. Adaptive Immunity
  • Innate: non-specific, quick acting
  • Adaptive: specific, includes memory
• Cells involved: B lymphocytes (humoral), T lymphocytes (cellular), macrophages, dendritic cells
• Antibodies: IgM, IgA, IgE, IgG
• Lymphatic System: lymph nodes, spleen, thymus

Digestive System

Anatomy

• Organs: mouth, pharynx, esophagus, stomach, intestines
• Accessory Glands: liver, pancreas, gallbladder

Function

• Digestion: Mechanical (mastication), Chemical (enzymes, acids)

Absorption

• Water-soluble through blood, fat-soluble through lymph

Homeostasis

Kidney

• Nephron: filtration, reabsorption, secretion, excretion
• Hormones: ADH (water reabsorption), Aldosterone (sodium reabsorption)

Skin

• Layers: Epidermis (ectoderm), Dermis (mesoderm)
• Functions: protection, thermoregulation

Musculoskeletal System

• Muscle Types: Skeletal, smooth, cardiac
• Muscle contraction: ATP needed, calcium role
• Types of bone: Compact, spongy
• Bone cells: Osteoblasts (build bone), Osteoclasts (breakdown bone)
• Joints: types and functions

Genetics

Basic Concepts

• Penetrance, expressivity, dominance vs. recessive traits
• Mendel's Laws: Segregation, Independent Assortment

Mutations

• Types: Missense, nonsense, frameshift

Evolution

• Natural Selection vs. Evolution
• Modes of Selection: Stabilizing, directional, disruptive
• Reproductive Isolation: Pre-zygotic, post-zygotic
• Evolution Patterns: Divergent, parallel, convergent

Conclusion

• Medicosis notes downloadable
• Check Biology playlist for detailed explanations