exam 2

Phospholipid Bilayer

  • What it does: The phospholipid bilayer forms the structural foundation of the cell membrane. It controls the movement of substances in and out of the cell while maintaining a semi-permeable barrier. The hydrophilic heads face outward towards the aqueous environment, while the hydrophobic tails point inward to avoid water.

  • Why it’s important: The bilayer’s selective permeability allows the cell to maintain homeostasis, regulate internal conditions, and interact with its environment.

Basic Organelles and Their Functions

  • Nucleus: Contains genetic material (DNA) and controls cellular activities such as growth and reproduction.

  • Mitochondria: Powerhouses of the cell, responsible for energy production (ATP) through cellular respiration.

  • Endoplasmic Reticulum (ER):

    • Rough ER: Studded with ribosomes, involved in protein synthesis.

    • Smooth ER: Synthesizes lipids, detoxifies toxins, and metabolizes carbohydrates.

  • Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for delivery to targeted destinations.

  • Lysosomes: Contain enzymes to break down waste, cellular debris, and foreign materials.

  • Ribosomes: Synthesize proteins.

  • Cytoskeleton: Provides structural support and aids in cell movement.

Definitions of Transport Mechanisms

  • Simple Diffusion: Movement of molecules from high to low concentration without energy expenditure.

  • Facilitated Diffusion: Movement of molecules across the membrane via specific transport proteins without energy expenditure.

  • Passive Transport: General term for any movement of substances across the membrane without energy input (e.g., simple diffusion, facilitated diffusion).

  • Active Transport: Movement of substances against their concentration gradient, requiring energy (ATP).

  • Osmosis: The diffusion of water across a selectively permeable membrane, from a region of low solute concentration to a region of high solute concentration.

  • Endocytosis: The process by which cells engulf substances from the external environment, bringing them into the cell.

  • Exocytosis: The process by which cells expel substances from within the cell to the external environment.

Osmotic Pressure

  • Osmotic pressure is the force that drives water to move across a membrane towards the side with higher solute concentration (to balance the solute levels).

Solution Types

  • Hypertonic Solution: Higher solute concentration outside the cell than inside, causing the cell to shrink (water moves out).

  • Hypotonic Solution: Lower solute concentration outside the cell, causing the cell to swell and possibly burst (water moves in).

  • Isotonic Solution: Equal solute concentration inside and outside the cell, no net movement of water.

Types of Epithelium

  • Simple Squamous Epithelium: Thin, flat cells; found in areas of diffusion or filtration (e.g., lungs, capillaries, kidneys).

  • Simple Columnar Epithelium: Tall, rectangular cells; found in areas of absorption and secretion (e.g., lining of the digestive tract).

  • Stratified Squamous Epithelium: Multiple layers of flat cells; found in areas exposed to abrasion (e.g., skin, esophagus).

  • Transitional Epithelium: Cells that can stretch and change shape; found in the bladder and urinary tract.

Endocrine vs. Exocrine Glands

  • Endocrine Glands: Secrete hormones directly into the bloodstream (e.g., thyroid, adrenal glands).

  • Exocrine Glands: Secrete substances through ducts to the outside of the body or into body cavities (e.g., sweat glands, salivary glands).

Cells of Connective Tissue

  1. Fibroblasts: Produce collagen and extracellular matrix.

  2. Adipocytes: Store fat.

  3. Macrophages: Engulf and digest foreign substances.

  4. Mast Cells: Release histamine and heparin in response to injury or infection.

  5. Chondrocytes: Produce and maintain cartilage.

  6. Osteocytes: Maintain bone tissue.

Protein Fibers in Connective Tissue

  1. Collagen Fibers: Provide strength and resist stretching.

  2. Elastic Fibers: Allow tissues to stretch and return to their original shape.

  3. Reticular Fibers: Form a supporting network within tissues.

Layers of the Epidermis

  1. Stratum Basale: Deepest layer, where new skin cells are generated.

  2. Stratum Spinosum: Provides strength and flexibility to the skin.

  3. Stratum Granulosum: Cells begin to die and form a barrier.

  4. Stratum Lucidum: Found only in thick skin (e.g., palms, soles), provides an additional layer of protection.

  5. Stratum Corneum: Outermost layer of dead skin cells, providing a waterproof barrier.

Cell Diagram (Lab 3)

  • Be able to identify the structures and organelles in a general cell diagram (e.g., nucleus, mitochondria, ER, Golgi, etc.).

Identify Tissue Types on Slides

  • Pseudostratified Epithelium: Appears to be layered but all cells touch the basement membrane (e.g., respiratory tract).

  • Skeletal Muscle: Multinucleated, striated fibers; voluntary control.

  • Adipose Tissue: Fat cells that store energy and provide insulation.

  • Bone Tissue: Hard, calcified matrix with osteocytes in lacunae.

  • Cartilage: Firm but flexible matrix with chondrocytes; includes hyaline, fibrocartilage, and elastic cartilage.