BIOS256 Comprehensive Review

BIOS256 Comprehensive Review Notes

Passive vs. Active Processes

• Passive Processes:

  • No energy required from the cell

  • Include:

  • Simple Diffusion

  • Facilitated Diffusion

  • Osmosis

• Active Processes:

  • Energy required for the cell to move substances across the membrane

  • Include:

  • Active Transport

  • Exocytosis

  • Endocytosis

    • Subtypes:

    • Phagocytosis

    • Pinocytosis

Simple Diffusion

• Definition: Movement of molecules from an area of higher concentration to an area of lower concentration.

• Direction: Move “down” the concentration gradient.

Factors Affecting Diffusion Rate Through a Membrane

• Temperature:

  • Higher temperature increases motion of particles.

• Molecular Weight:

  • Larger molecules move more slowly.

• Steepness of Concentrated Gradient:

  • Greater concentration difference increases the rate.

• Membrane Surface Area:

  • Increased surface area leads to an increased rate.

• Membrane Permeability:

  • Higher permeability results in a higher rate.

Facilitated Diffusion

• Definition: Similar to diffusion, but molecules are ferried across the membrane by a carrier molecule allowed entry by a channel.

Osmosis

• Definition: Movement of water only.

• Mechanism: Water moves from regions of higher concentration to lower concentration, or it moves toward a higher concentration of solutes.

Tonicity

• Hypertonic:

  • More solutes outside than inside the cell; results in cell shrinkage.

• Isotonic:

  • Equal solute concentration inside and outside the cell; cell remains the same.

• Hypotonic:

  • More solutes inside than outside; cell swells and may burst.

Active Transport

• Definition: Movement of substances from an area of lower concentration to higher concentration.

• Mechanism: Moving “against” the concentration gradient.

• Energy Requirement: Requires ATP energy.

• Example: Solute pumps like Na+, K+, Ca2+.

Types of Active Transport

• Sodium-Potassium Pump (Na+-K+ ATPase)

• Endocytosis

• Exocytosis

Cell Membrane and Vesicle Interaction

• Endocytosis: Process of taking materials into the cell.

• Exocytosis: Process of expelling materials from the cell.

Membranes

• Definition: Flat sheets of pliable tissue that cover or line parts of the body.

• Types of Membranes:

  • Epithelial Membranes:

  • Mucous membranes

  • Serous membranes

  • Cutaneous membranes

  • Synovial Membranes

Four Tissue Types in the Human Body

1. Epithelial: Lines (covers) body surfaces and cavities.

2. Connective: Supports and binds body parts.

3. Muscular: Moves the body and its parts.

4. Nervous: Receives stimuli and conducts impulses.

The Epidermis

• Contains four major types of cells:

  1. Keratinocytes

  2. Melanocytes

  3. Intraepidermal macrophages (Langerhans cell)

  4. Tactile epithelial cells (Merkel cell)

Structure of the Epidermis

• Composition:

  • Thinner skin: 4 layers

  • Thicker skin: 5 layers

• Layers (from deep to superficial):

  1. Stratum basale

  2. Stratum spinosum

  3. Stratum granulosum

  4. Stratum lucidum (only in thick skin)

  5. Stratum corneum

Skin Pigments

• Melanin: Produced by melanocytes in the stratum basale.

  • Types of Melanin:

  • Pheomelanin: Reddish-brown.

  • Eumelanin: Brown-black.

• Other Pigments:

  • Hemoglobin: A red pigment in red blood cells.

  • Carotene: A yellow-orange pigment stored in the stratum corneum and adipose tissue.

Burns

• Definition: Tissue damage caused by excessive heat, electricity, radioactivity, or corrosive chemicals that denature proteins in skin cells.

• Grading Burns by Severity:

  • First-degree Burn: Affects epidermis.

  • Second-degree Burn: Affects epidermis and dermis.

  • Third-degree Burn: Affects all layers (epidermis, dermis, hypodermis).

Skin Grafts

• Third-degree Burns: Often require skin grafts.

  • Autograft: Tissue from another location on the same person’s body.

  • Split-skin graft: Involves taking epidermis and part of the