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Summary

This comprehensive review covers fundamental biological concepts including stem cells, tissue repair, cellular processes, basic chemistry, genetics, and tissue types. The material emphasizes cellular biology, molecular processes, and physiological systems essential for understanding life sciences.

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Stem Cells and Cellular Differentiation

Types of Stem Cells by Potential

• Totipotent stem cells: Can give rise to every cell type in the body

• Only exists at very early developmental stages (2-4 cell stage)

• How identical twins form - cells split at this stage

• Each cell can develop into entire individual

• Pluripotent stem cells: Can give rise to many different cell types

• Multipotent stem cells: More limited potential, give rise to specific cell lineages

Stem Cell Locations

• Bone marrow: Give rise to different blood cell types (white blood cells, red blood cells)

• Gums: Contain stem cells for tissue repair

• Heart: Small number of stem cells present

• Skin: Stem cells for tissue regeneration

• Male gametes: Males have stem cells that produce sperm for decades

• Female gametes: Females born with all gametes arrested at prophase I

Cellular Differentiation

• Definition: Development from stem cells into specialized cell types

• Metaplasia: Change from one type of mature tissue to another

• Example: Vaginal tissue changes from simple cuboidal to stratified squamous after puberty

• Smoker's lungs: Ciliated epithelium changes to stratified squamous (loses cilia function)

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Tissue Repair and Regeneration

Types of Tissue Growth

• Hyperplasia: Growth through cell multiplication (active cell division)

• Hypertrophy: Growth through increase in cell size

• Seen in muscle growth from exercise

• Adipose tissue expansion

• Neoplasia: Development of tumors (abnormal, non-functional tissue)

Tissue Repair Mechanisms

• Regeneration: Ability to replace or repair damaged cells

• Liver cells: Constantly exposed to toxins, need repair ability

• Skin cells: Mechanical damage requires regenerative capacity

• GI tract: Constant mechanical stress and shedding

• Fibrosis: Replacement of damaged cells with scar tissue

• Occurs when highly specialized cells cannot reproduce

• Scar tissue fills gaps but doesn't perform original function

• Example: Lung damage from smoke inhalation

Wound Healing Process

1. Initial response: Blood vessels release blood, damage signals sent

2. Clotting: Clotting factors create protein scaffolds for cell attachment

3. Scab formation: Temporary seal prevents pathogen entry

4. Granulation tissue: Macrophages remove clots, fibroblasts deposit collagen

5. Remodeling phase: Begins weeks after injury, may last years

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Cell Death and Damage

Apoptosis (Programmed Cell Death)

• Definition: Controlled cell suicide, not tissue necrosis

• Triggers:

• Cells reach replication limit (25-50 divisions)

• Chromosome damage from telomere shortening

• Abnormal cell development

• Functions:

• Removes webbing between digits during development

• Prevents cancer by eliminating abnormal cells

• Immune system recognition and cleanup

Necrosis

• Definition: Tissue damage and death from blood supply loss

• Gangrene: Tissue necrosis with insufficient blood supply

• Dry gangrene: Diabetes complication, poor circulation

• Gas gangrene: Infection with Clostridium bacteria

Atrophy

• Definition: Shrinkage of tissues and loss of cell size

• Example: Muscle atrophy from lack of use

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Basic Chemistry and Atomic Structure

Atomic Components

• Atomic number: Number of protons (defines the element)

• Atomic mass: Number of protons + neutrons

• Isotopes: Same element with different numbers of neutrons

• Often radioactive and unstable

• Used in carbon dating

Electron Configuration

• Valence electrons: Outermost electrons that participate in bonding

• Noble gas rule: Atoms want complete outer electron shells

• Ion formation:

• Metals lose electrons to achieve stability

• Nonmetals gain electrons to achieve stability

Chemical Bonding

• Ionic bonds: Transfer of electrons (metal + nonmetal)

• Example: Sodium chloride (Na⁺ + Cl⁻)

• Covalent bonds: Sharing of electrons

• Nonpolar covalent: Equal sharing (C-H bonds in fats)

• Polar covalent: Unequal sharing (water molecules)

• Hydrogen bonds: Attraction between polar molecules

• Critical for water's properties and life processes

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Cellular Transport and Membrane Function

Tonicity

• Hypertonic: High solute concentration, water moves out of cell (cell shrinks)

• Hypotonic: Low solute concentration, water moves into cell

• Isotonic: Equal concentrations, no net water movement

• IV fluids are 0.9% saline (isotonic)

Transport Types

• Simple diffusion: No energy required

• Active transport: Requires ATP, moves against concentration gradient

• Carrier-mediated transport:

• Uniport: One substance, one direction

• Symport: Two substances, same direction

• Antiport: Two substances, opposite directions

Sodium-Glucose Cotransport

• Example of symport mechanism

• Sodium naturally wants to enter cell

• Glucose coupled to sodium movement

• Allows glucose uptake against concentration gradient

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DNA, RNA, and Protein Synthesis

DNA Structure and Replication

• Base pairing: A-T, G-C

• Semi-conservative replication: One old strand, one new strand per DNA molecule

• If 20% G, then 20% C and 60% A-T combined

Transcription and Translation

• Transcription: Making mRNA from DNA (in nucleus)

• Translation: Making protein from mRNA (at ribosomes)

• mRNA splicing: Introns removed, exons kept for protein coding

Protein Structure and Function

• Primary structure: Amino acid sequence

• Secondary, tertiary, quaternary: Progressive folding levels

• Denaturation: Loss of 3D structure from heat, pH changes

• Enzyme-substrate specificity: Active site shape determines function

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Tissue Types and Organization

Four Major Tissue Types

1. Epithelial tissue: Lines and covers body surfaces

2. Connective tissue: Support and protection

3. Muscle tissue: Movement and contraction

4. Nervous tissue: Communication and control

Muscle Tissue Types

• Skeletal muscle:

• Voluntary control

• Striated, multinucleated

• Attaches to bones for movement

• Cardiac muscle:

• Involuntary, found only in heart

• Striated, single nucleated

• Intercalated discs for communication

• Smooth muscle:

• Involuntary control

• Non-striated, single nucleated

• Found in blood vessels, digestive tract

Nervous Tissue

• Neurons: Conduct electrical signals

• Cell body, dendrites (receive signals), axon (transmit signals)

• Glial cells: 90% of nervous system cells

• Protect, nourish, and support neurons

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Cellular Junctions

Types of Junctions

• Tight junctions: Seal spaces between cells

• Prevent leakage (important in blood-brain barrier)

• Desmosomes: Provide mechanical strength

• Found in skin epidermis, resist shearing forces

• Gap junctions: Allow communication between cells

• Found in cardiac muscle, smooth muscle, eye tissue

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Glands and Secretion

Gland Types

• Exocrine glands: Secrete through ducts to external surfaces

• Examples: Salivary glands, sweat glands

• Products: Enzymes, mucus, digestive juices

• Endocrine glands: Secrete hormones directly into blood

• Examples: Pituitary, thyroid

• Hormones travel to distant target organs

Secretion Types

• Secretion: Useful products for the body

• Excretion: Waste products to be eliminated

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Membranes and Body Coverings

Membrane Types

• Cutaneous membrane: Skin (largest membrane)

• Epidermis: Stratified, avascular, protective

• Dermis: Vascular, contains nerves and sensory endings

• Mucous membranes: Line passages open to external environment

• Serous membranes: Line internal body cavities

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Key Concepts for Exam

Cell Cycle Phases

• G1: Cell growth and protein expression

• S phase: DNA replication

• G2: Preparation for division

• G0: Cells out of cell cycle

• Mitosis phases: Prophase, metaphase, anaphase, telophase

Important Processes

• Hydrolysis: Adding water to break bonds

• Dehydration synthesis: Removing water to form bonds

• Phosphorylation: Adding phosphate groups (turns processes on)

• Feedback mechanisms:

• Negative feedback: Maintains homeostasis

• Positive feedback: Amplifies response (labor contractions)

pH and Acids/Bases

• pH scale: Logarithmic scale of H⁺ concentration

• pH of 3 is 100 times more acidic than pH of 5