Introduction to Human Cells – Nursing Fundamentals

Two Main Types of Cells

• Prokaryotic Cells
  • Simpler, no membrane-bound nucleus.
  • Example: most bacteria.
  • Significance: understanding antibiotics—many drugs exploit structural differences (e.g.
    cell wall) between prokaryotes and human (eukaryotic) cells.
• Eukaryotic Cells
  • Complex, contain a true nucleus and organelles.
  • Human, plant, fungal, and protozoan cells.
  • Clinical link: virtually everything in nursing—the tissues, organs, pathogens like fungi and parasites—involves eukaryotic cell biology.

Main Parts of a Human (Eukaryotic) Cell

• Cell (Plasma) Membrane
  • Phospholipid bilayer; selectively permeable.
  • Controls what enters and leaves; maintains homeostasis.
  • Nursing relevance: IV fluids, electrolyte balance, and osmotic/tonic effects all act through membrane transport mechanisms.
• Cytoplasm
  • Viscous, jelly-like matrix that suspends organelles.
  • Site of many metabolic pathways (e.g. glycolysis).
  • Practical note: abnormal cytoplasmic inclusions (e.g. Heinz bodies) can indicate disease.
• Nucleus
  • "Control center" housing DNA.
  • Regulates gene expression, cell cycle, apoptosis.
  • Mutations here may lead to cancers or genetic disorders.
• Mitochondria
  • "Powerhouse"; generates ATP via cellular respiration.
  • Contains its own circular DNA—maternal inheritance.
  • Dysfunction → metabolic diseases, lactic acidosis.
• Ribosomes
  • Protein factories; free or bound to ER.
  • Translate mRNA → polypeptides.
  • Antibiotic target in prokaryotes (e.g. 30S, 50S subunits) without harming human (80S) ribosomes.
• Endoplasmic Reticulum (ER)
  • Rough ER: studded with ribosomes; synthesizes membrane & secretory proteins.
  • Smooth ER: lipid metabolism, detoxification (important in liver cells).
  • Remember as cell’s "hallway" moving material within.
• Golgi Apparatus
  • Sorts, modifies, and packages proteins/lipids into vesicles.
  • Think "shipping & receiving"; forms lysosomes and secretory vesicles.
• Lysosomes
  • Contain digestive enzymes; break down waste, pathogens, old organelles.
  • Malfunction → storage diseases (e.g. Tay-Sachs).
  • Nickname: "clean-up crew".
• Centrioles / Centrosome
  • Organize spindle fibers during mitosis/meiosis.
  • Ensures equal chromosome segregation.
  • Chemotherapy targets rapid spindle formation, hence hair-loss side effect (follicular cells rapidly divide).

How Cells Make Energy: Cellular Respiration

• Occurs primarily in mitochondria.
• Overall balanced equation:
  \text{Glucose} + \text{O}2 \; \Rightarrow \; \text{CO}2 + \text{H}_2\text{O} + \text{ATP (energy)}
• Physiologic context: after eating carbohydrates, glucose enters cells (facilitated by insulin), undergoes glycolysis in cytoplasm → pyruvate enters mitochondria → Krebs cycle & oxidative phosphorylation.
• Approx. 36-38 ATP generated per glucose under ideal aerobic conditions.
• Clinical tie-in: hypoxia shifts metabolism to anaerobic glycolysis → lactic acidosis; nurses monitor oxygen saturation to prevent this.

DNA & Protein Production

• DNA Localization: confined within nuclear envelope.
• Central Dogma: DNA (transcription) → mRNA (translation) → Protein.
• Process:
  1. DNA’s genetic code is transcribed into mRNA.
  2. mRNA exits nucleus via nuclear pores.
  3. Ribosomes read mRNA codons, assemble amino acids into polypeptides.
• Importance: proteins form enzymes, hormones, structural fibers; their correct synthesis is vital for growth, repair, immunity.
• Pharmacologic link: some antivirals block transcription/translation in viruses.

Cell Division: Mitosis

• Purpose: growth, tissue repair, asexual reproduction of somatic cells.
• Produces two genetically identical daughter cells (diploid → diploid).
• Key phases remembered by mnemonic I-P-M-A-T:
  • Interphase: DNA replication; cell prepares.
  • Prophase: chromatin condenses; spindle forms.
  • Metaphase: chromosomes align at metaphase plate.
  • Anaphase: sister chromatids pulled apart.
  • Telophase: nuclear membranes re-form; cytokinesis follows.
• Clinical correlation:
  • Cancer = loss of cell-cycle control → uncontrolled mitosis.
  • Chemotherapy & radiation aim to halt rapidly dividing cells; side effects hit other fast-growing tissues (GI mucosa, hair follicles, bone marrow).

Why Cells Matter in Nursing Practice

Additional points:

• Fluid/electrolyte management influences membrane potential and cellular hydration.
• Ethical angle: gene-editing therapies (e.g. CRISPR) target faulty DNA—raising questions about consent, equity, long-term effects.
• Pharmacology: many drugs act at cellular level—e.g. proton-pump inhibitors block gastric parietal cell pumps.

Quick Recap / High-Yield Facts

• Cells are fundamental units of life; human cells are eukaryotic.
• Nucleus houses DNA, dictating cell functions.
• Mitochondria convert nutrients to \text{ATP}—the usable energy currency.
• Ribosomes, ER, and Golgi collaborate to create and ship proteins.
• Mitosis (I-P-M-A-T) allows growth and repair; dysregulation leads to cancer.
• Proper oxygenation, nutrition, and hydration are critical for cellular health—core aspects of nursing assessments and interventions.

Need more practice? Consider:

• Flashcards for organelle functions.
• Labeling diagrams.
• Mini-quizzes on mitosis phases or cellular respiration pathway.