Comprehensive Physiology and Cell Biology Review for Students

Physiology

The study of the normal functions of living organisms and their component parts, including the physical and chemical processes that sustain life.

Anatomy

Structure and location.

Pathology

Abnormalities of structure and/or function (disease).

Levels of Biological Organization

Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ systems → Organism.

Integumentary System

Protection.

Musculoskeletal System

Support, movement.

Respiratory System

Gas exchange.

Digestive System

Nutrients/water, waste.

Urinary System

Water/ion balance, waste.

Reproductive System

Gametes, hormones.

Circulatory System

Transport.

Nervous System

Fast coordination.

Endocrine System

Slow/hormonal coordination.

Immune System

Defense.

Homeostasis

The systems integrate to maintain balance.

Function in Physiology

Purpose of a process.

Mechanism in Physiology

Biophysical/biochemical steps that produce the function.

Miller-Urey Experiment (1953)

Simulated early Earth atmosphere + sparks produced amino acids and organic molecules, suggesting life's building blocks could form spontaneously.

Essential Elements for Life

Carbon, Hydrogen, Oxygen, Nitrogen (also P, S).

Catalytically Important Metals

Magnesium, Zinc, Iron, Copper, Manganese, Cobalt.

Ions Important for the Body

ECF: Na⁺, Cl⁻, HCO₃⁻; ICF: K⁺, Mg²⁺, phosphates, proteins; Others: Ca²⁺, H⁺, SO₄²⁻; trace metals.

Definition of Biomolecules

Biologically relevant molecules involved in structure, energy, storage, or signaling.

Four Classes of Biomolecules

Carbohydrates, Lipids, Proteins, Nucleotides.

Carbohydrates

Energy, storage; monosaccharides.

Lipids

Membranes, energy, signaling; fatty acids, sterols.

Proteins

Structure, enzymes; amino acids.

Nucleotides

Energy, information; nucleotides (base+sugar+phosphate).

Common Functional Groups

Hydroxyl, Carbonyl, Carboxyl, Amino, Phosphate, Sulfhydryl, Methyl, Ester, Ether, Amide, Acetyl.

Key Elements & Atomic Structure

Protons (+), neutrons (0), electrons (-). Valence electrons determine bonding.

Ion

Charged atom/molecule.

Cation

Positive.

Anion

Negative.

Isotope

Same element, different neutron number.

Biological Roles of Electrons

1. Covalent bonds. 2. Carry energy (NADH, FADH₂). 3. Electrical gradients/membrane potentials. 4. Signaling/free radicals.

Types of Bonds & Interactions

Covalent: polar (O-H) or nonpolar (C-H); Ionic: electrostatic; Hydrogen bonds: weak attraction; Van der Waals: transient dipoles.

Solute

dissolved substance.

Solvent

medium (often water).

Solution

mixture.

Solubility

max amount dissolvable.

Acids

donate H⁺, bases accept H⁺.

pH

measures acidity.

Acid

proton donor.

Base

proton acceptor.

Arterial blood pH

~7.4.

Cytosol pH

~7.2.

Stomach pH

1-3.

Urine pH

4.5-8.

Functions of proteins

Enzymes, transporters, receptors, signals, binding proteins, structural, defense/motility.

Activation

cofactors, cleavage, allosteric activators.

Inhibition

competitive, noncompetitive, covalent, allosteric.

Ligand

binds protein.

Substrate

ligand enzyme acts on.

Binding site

protein region that binds.

Specificity

selectivity.

Affinity

strength.

Competition

multiple ligands.

Saturation

all sites filled.

Ka

association constant.

Kd

dissociation constant (lower Kd = higher affinity).

Law of mass action

Reaction shifts based on concentration of reactants/products.

Cell types

Prokaryotes: no nucleus/organelles; Eukaryotes: nucleus, organelles; Plant: cell wall, chloroplasts; Animal: centrioles, no wall.

Body compartments

Cranial, thoracic, abdominopelvic cavities; Fluids: ICF, ECF.

Lumen

Interior of hollow organ/tube.

Biological membranes

Phospholipid bilayer with proteins, cholesterol. Functions: barrier, signaling, transport.

Cell organelles

Nucleus, ribosomes, ER, Golgi, mitochondria, lysosomes, peroxisomes, cytoskeleton.

Cytoskeleton

Actin, intermediate filaments, microtubules. Motor proteins: myosin, kinesin, dynein.

Tissues

Epithelial, connective, muscle, nervous.

Characteristics of tissues

Epithelial: protection, absorption, secretion; Connective: support, binding; Muscle: contraction; Nervous: excitability.

Extracellular matrix

Proteins + ground substance; support, signaling, adhesion.

Cell junctions

Tight junctions, adherens, desmosomes, gap junctions, hemidesmosomes.

Properties of living organisms

Cellular, metabolism, homeostasis, growth, responsiveness, reproduction, heredity, movement.

Bioenergetics

energy flow.

Metabolism

all biochemical reactions.

Critical components

Storage (ATP, glycogen), transfer (NADH), release (catabolism).

Types of work

Chemical, transport, mechanical.

Energy forms

Kinetic = motion; Potential = stored.

First law of thermodynamics

Energy conserved. Humans are open systems but law still applies.

Second law of thermodynamics

Entropy increases; energy conversions release heat.

Types of chemical reactions

Synthesis, decomposition, exchange, redox, isomerization.

Exergonic

release energy (ΔG < 0).

Endergonic

require input (ΔG > 0).

Activation energy

barrier.

High-energy electrons & heat

Electrons in NADH/FADH₂ carry energy to ETC; some lost as heat.

Enzyme classes

Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases.

Chemical reaction rate

Rate = change in concentration over time.

Enzyme role

Catalysts; lower activation energy.

Substrate & factors affecting rate

Substrate = reactant. Factors: enzyme conc., substrate conc., temp, pH, cofactors, inhibitors.

Regulation of enzymes

1. Control concentration. 2. Modulate activity. 3. Use different enzymes. 4. Compartmentalize. 5. Maintain ATP/ADP ratio.

ATP

Immediate energy molecule with high-energy bonds; made in glycolysis and oxidative phosphorylation.

Pathways

● Glycolysis: cytosol, glucose → pyruvate, ATP, NADH. ● Pyruvate → Acetyl-CoA (mito matrix). ● Krebs: CO₂, NADH, FADH₂, GTP. ● ETC: ATP synthesis, O₂ final acceptor.

Types of transport

Diffusion, facilitated diffusion, osmosis, primary/secondary active transport, vesicular.

Fluid compartments

ICF (2/3), ECF (1/3). Maintained by kidneys, lungs, CV, endocrine.

Homeostasis vs equilibrium vs disequilibrium

Homeostasis = stable ranges. Equilibrium = equal across compartments. Disequilibrium = maintained differences (ion gradients).

Active vs passive transport

Passive = no energy (diffusion). Active = needs energy (ATP, gradients).

Which requires energy

Active transport. Major source: ATP.

Examples of transport

Diffusion: O₂, CO₂. Channels: Na⁺, K⁺. Facilitated: GLUT. Primary active: Na⁺/K⁺ pump. Secondary: SGLT, Na⁺/Ca²⁺ exchanger. Vesicular: endocytosis, exocytosis.

Diffusion & Fick's law

Rate ∝ surface area, gradient, permeability; inverse to distance and size.

Simple diffusion model

Random motion; efficient over short distances.

Osmosis

Water moves toward higher solute concentration.

Tonicity

Hypotonic = water enters cells. Isotonic = no net change. Hypertonic = water exits cells.