Cell Biology: Plasma Membrane Functions

Plasma Membrane

• Composed primarily of lipids and proteins with minor carbohydrate presence.
• Functions as a barrier, separating intracellular and extracellular environments.
• Capable of membrane fusion, allowing for interaction and transport between cells.

Membrane Proteins

• Integral membrane proteins penetrate deeply and often traverse the bilayer, playing roles in channel formation.
• Peripheral membrane proteins associate with the membrane surface, contributing to various functions depending on their shape.

Membrane Potential

• An electrical charge difference is established across the plasma membrane due to regulated ion movement.
• Positive ions dominate outside, while negative ions dominate inside, creating a polarized environment crucial for cell function.

Marker Molecules

• Glycoproteins and glycolipids enable cell recognition, allowing cells to identify themselves and differentiate from foreign cells.

Intercellular Communication

• Ligand-gated ion channels open in response to specific molecules binding to proteins or glycoproteins.
• Voltage-gated channels respond to changes in membrane charge, contributing to communication and signal transduction.

Body Cavities

• Dorsal cavity: Includes the cranial cavity (brain) and vertebral canal (spinal cord).
• Ventral cavity contains major organs, subdivided into thoracic (lungs, heart) and abdominopelvic (digestive organs) cavities.

Cell Structure

• General components include the plasma membrane (cell boundary), nucleus (controls activities), and cytoplasm (contains organelles).
• Cells are defined as the basic unit of life and engage in metabolism, synthesis of molecules, communication, and reproduction.

Membrane Lipids

• Phospholipids form a bilayer with hydrophilic heads facing water and hydrophobic tails inward.
• Cholesterol interspersed among phospholipids maintains membrane fluidity.

Fluid-Mosaic Model

• Describes membrane as a flexible structure where proteins and lipids can move laterally, enabling dynamic interactions.
• Phospholipids can reseal if damaged, promoting membrane integrity.

Accessory Skin Structures

• Nails and hair serve protective functions; nails are made of hard keratin.
• Arrector pili muscles cause hair to stand upright and create “goosebumps.”

Integumentary System Functions

• Protection from abrasion, microorganisms, and UV radiation.
• Glandular secretions possess antibacterial properties, and melanin offers UV protection.

Vitamin D Production

• Begins in the skin and is crucial for calcium absorption.
• UV radiation converts 7-dehydrocholesterol into cholecalciferol, which is further modified to produce calcitriol, the active form of vitamin D.

Aging Effects on Skin

• Thinning epidermis and decreased collagen lead to easier skin damage and increased wrinkles.
• Reduced melanocyte function contributes to age spots and decreased UV protection.
• diminished blood supply affects temperature regulation and moisture retention.

Burns Classification

• Partial-thickness (first and second-degree) and full-thickness (third and fourth-degree) indicate depth and severity of damage.

Healing and Skin Grafts

• Skin can heal through natural regeneration or artificial skin options from cadavers or pigs used for grafting.