Absolutely! Here’s an expanded and refined version of the Cell Physiology topic with detailed explanations and examples, ideal for nursing, medical, or biology students.
🧬 CELL PHYSIOLOGY – DETAILED OVERVIEW
Cell physiology is the study of the vital functions and processes carried out by cells to support life. Each cell operates as a self-regulating unit, capable of performing complex biological tasks essential for survival, growth, communication, and reproduction.
📌 KEY FUNCTIONS OF CELL PHYSIOLOGY
Transport of Substances Across Cell Membrane
Cellular Respiration & Energy Production
Protein Synthesis
Cell Communication & Signal Transduction
Cell Growth, Division, and Death
Homeostasis and Internal Regulation
🧱 STRUCTURE OF THE CELL MEMBRANE (Plasma Membrane)
The cell membrane is semi-permeable and acts as a selective barrier.
🔹 Major Components:
Phospholipid bilayer: Provides fluidity and barrier to polar substances.
Membrane proteins:
Integral proteins: Embedded across the membrane; transporters, channels.
Peripheral proteins: Attached to membrane surface; enzymes, signaling.
Cholesterol: Stabilizes membrane, especially in varying temperatures.
Carbohydrates (Glycoproteins/Glycolipids): Cell recognition and immune response.
🔄 TRANSPORT ACROSS THE CELL MEMBRANE
1. ✅ Passive Transport (No Energy Required)
Movement occurs along a concentration gradient (high to low concentration).
a) Simple Diffusion
Direct passage of small, non-polar molecules through the lipid bilayer.
Movement of water through aquaporins (water channels).
From low solute to high solute concentration.
Importance: Maintains fluid balance across membranes (e.g., in kidneys).
2. ⚡ Active Transport (Energy Required)
Movement against the concentration gradient, using ATP.
a) Primary Active Transport
Directly uses energy from ATP to move molecules.
Example: Sodium-potassium pump (Na⁺/K⁺-ATPase)
3 Na⁺ ions out, 2 K⁺ ions in
Maintains electrochemical gradient, essential for nerve impulse conduction and muscle contraction.
b) Secondary Active Transport (Co-Transport)
Uses the energy from another molecule’s concentration gradient.
Symport: Both molecules move in the same direction (e.g., Na⁺ & glucose in intestinal cells)
Antiport: Molecules move in opposite directions (e.g., Na⁺/Ca²⁺ exchange)
3. 📦 Bulk (Vesicular) Transport
Used for macromolecules (proteins, polysaccharides) or large particles.
a) Endocytosis (Substance moves into the cell)
Phagocytosis (“cell eating”) – Engulfment of large particles by pseudopodia (e.g., WBC engulfing bacteria).
Pinocytosis (“cell drinking”) – Uptake of fluids or dissolved substances.
Receptor-mediated endocytosis – Specific molecules bind to receptors before being engulfed.
b) Exocytosis (Substance moves out of the cell)
Vesicles containing substances fuse with the plasma membrane to release contents outside.
Example: Secretion of hormones, enzymes, neurotransmitters.
⚙️ OTHER ESSENTIAL CELLULAR FUNCTIONS
🔋 1. Cellular Respiration (Energy Production)
Occurs primarily in the mitochondria, converting glucose into ATP (adenosine triphosphate).
Type
Oxygen
ATP Yield
Byproducts
Aerobic
Yes
36–38 ATP
CO₂, H₂O
Anaerobic
No
2 ATP
Lactic acid (in humans)
Importance: Provides energy for all metabolic and physiological activities.
🧬 2. Protein Synthesis
The process by which cells produce proteins needed for structure, enzymes, hormones, etc.
Step
Location
Description
Transcription
Nucleus
DNA → mRNA (messenger RNA)
Translation
Ribosome
mRNA → Protein (with help of tRNA)
Endoplasmic Reticulum & Golgi Apparatus process, fold, and package proteins for function or secretion.
📞 3. Cell Signaling & Communication
Cells communicate via:
Chemical messengers (hormones, neurotransmitters)
Receptors (proteins that bind specific signals)
Second messengers (e.g., cAMP)
This helps in coordination, response to stimuli, and regulation of cell activity.
📈 4. Cell Cycle – Growth & Division
Regulated phases ensuring proper duplication and division:
Phase
Description
G1 Phase
Cell grows and synthesizes proteins
S Phase
DNA replication
G2 Phase
Preparation for division
M Phase
Mitosis (division)
Mitosis: For somatic cell division (growth and repair)
Meiosis: For gamete formation (reproduction)
🧬 5. Apoptosis (Programmed Cell Death)
A natural process to remove damaged or unnecessary cells. Prevents cancer and autoimmune reactions.
🧠 CLINICAL APPLICATIONS / RELEVANCE
Condition
Related Cell Physiology Disruption
Cystic Fibrosis
Faulty Cl⁻ transport protein → thick mucus
Diabetes Mellitus
Impaired glucose transport and insulin signaling
Hyponatremia
Disturbed osmosis → brain swelling
Cancer
Uncontrolled cell division (mitosis failure)
Ischemia/Hypoxia
No oxygen → reduced ATP → active transport fails
Neurotoxins
Disrupt ion channels → paralysis/seizures
📚 Summary Table: Key Cell Functions
Function
Organelle Involved
Notes
Transport
Cell membrane, transport proteins
Passive & active types
Energy Production
Mitochondria
ATP generation via respiration
Protein Synthesis
Nucleus, Ribosome, ER, Golgi
DNA → mRNA → Protein
Communication
Receptors, signaling molecules
Hormonal & neural communication
Growth & Division
Nucleus, Centrosome
Cell cycle, mitosis
Waste Disposal
Lysosomes
Digest unwanted materials
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🔄 TRANSPORTATION ACROSS CELL MEMBRANE IN DETAILS
The cell membrane (plasma membrane) is selectively permeable, meaning it allows some substances to pass while restricting others. This regulation maintains the internal environment of the cell (homeostasis).
1. Passive Transport
Does not require energy (ATP)
Substances move from high to low concentration (down the gradient)
a) Simple Diffusion
Movement of small, non-polar molecules (O₂, CO₂)
Directly through the phospholipid bilayer
b) Facilitated Diffusion
Movement via transport proteins (channel or carrier)
For larger or polar molecules like glucose, ions (Na⁺, K⁺)
c) Osmosis
Diffusion of water across a semi-permeable membrane
Moves from low solute concentration to high solute concentration
2. Active Transport
Requires energy (ATP)
Moves substances against the concentration gradient (low to high)
a) Primary Active Transport
Direct use of ATP
Example: Sodium-Potassium Pump (Na⁺/K⁺ ATPase)
Pumps 3 Na⁺ out, 2 K⁺ into the cell
Maintains electrochemical gradient
b) Secondary Active Transport (Co-transport)
Indirect use of ATP
Uses energy from the gradient of one molecule to transport another
Symport: Both substances move in the same direction
Antiport: Substances move in opposite directions
3. Bulk Transport (Vesicular Transport)
For large molecules like proteins, polysaccharides