Chapter 5: Membrane Structure and Function Flashcards

Vocabulary flashcards generated from the Chapter 5 lecture transcript covering membrane composition, transport mechanisms, signaling pathways, and cell surface structures.

Plasma membrane

A selectively permeable boundary surrounding every cell that controls what enters and leaves, allows cellular communication, and interacts with the environment.

Selectively permeable

A property of the cell membrane meaning that some substances can cross more easily than others.

Phospholipid

The main structural component of the plasma membrane, featuring a polar, hydrophilic head and nonpolar, hydrophobic fatty acid tails.

Hydrophilic head

The polar part of a phospholipid that interacts well with water.

Hydrophobic tails

The nonpolar fatty acid portion of a phospholipid that avoids water and faces inward within the bilayer.

Fluid mosaic model

A model describing the cell membrane as a flexible layer where phospholipids can move laterally (fluid) and is embedded with various proteins and molecules (mosaic).

Cholesterol

A membrane component that plays an important structural role in regulating membrane fluidity.

Glycoprotein

A carbohydrate attached to a protein on the outside of the cell membrane, functioning in cell recognition.

Glycolipid

A carbohydrate attached directly to a lipid on the outside of the cell membrane, functioning in cell recognition.

Channel proteins

Selective membrane proteins that create open pathways through the membrane for specific ions or molecules to pass without touching the hydrophobic interior.

Carrier proteins

Membrane proteins that bind to a specific substance and undergo a shape change to move the substance across the membrane.

Cell recognition proteins

Membrane proteins, such as MHC proteins, that serve as surface markers allowing the immune system to recognize cells as belonging to the body or foreign.

Receptor proteins

Proteins on the cell surface with specific shapes that bind signaling molecules (such as growth hormone) to initiate cellular responses.

Enzymatic proteins

Membrane proteins that function directly as enzymes to catalyze and speed up specific chemical reactions.

Junction proteins

Membrane proteins that connect cells together tightly or allow signals and materials to pass between neighboring cells.

Signal transduction pathway

A sequence of molecular events inside a cell consisting of reception, transduction, and response, initiated by a signaling molecule binding to a receptor.

Aquaporin

A specialized membrane protein that facilitates the rapid movement of water across the cell membrane.

Diffusion

The net movement of molecules down their concentration gradient from an area of high concentration to low concentration without requiring energy or transport proteins.

Facilitated transport

The passive movement of molecules down their concentration gradient across a membrane using a channel or carrier protein without consuming ATP.

Active transport

The movement of substances across a membrane against their concentration gradient (from low to high concentration), requiring cellular energy in the form of ATP.

Osmosis

The diffusion of water across a permeable membrane toward the side with a higher solute concentration.

Osmotic pressure

The pressure created by the movement of water across a membrane during osmosis.

Isotonic solution

A solution in which the solute concentration is balanced across the cell membrane, resulting in equal movement of water in both directions and no net movement.

Hypotonic solution

A solution with a lower solute concentration outside the cell than inside, causing water to enter the cell, leading to swelling or lysis in animal cells and turgor pressure in plant cells.

Hypertonic solution

A solution with a higher solute concentration outside the cell than inside, causing water to leave the cell, leading to crenation in animal cells and plasmolysis in plant cells.

Crenation

The shrinking or shriveling of an animal cell when placed in a hypertonic solution.

Plasmolysis

The shrinking of plant cytoplasm away from the rigid cell wall due to water loss in a hypertonic solution.

Turgor pressure

The internal pressure created when water fills the vacuole of a plant cell placed in a hypotonic solution, keeping the cell firm.

Sodium-potassium pump

A active transport protein that uses ATP to pump three sodium ions out of the cell and two potassium ions into the cell against their concentration gradients.

Bulk transport

The process of moving large materials or large quantities of substances into or out of the cell using vesicles.

Exocytosis

A form of bulk transport where an internal vesicle fuses with the plasma membrane to release its contents outside the cell.

Endocytosis

A form of bulk transport where the plasma membrane folds inward and pinches off to create a vesicle that brings materials into the cell.

Phagocytosis

A type of endocytosis commonly referred to as 'cell eating,' in which the cell takes in large solid particles.

Pinocytosis

A type of endocytosis commonly referred to as 'cell drinking,' in which the cell takes in fluid and small particles.

Receptor-mediated endocytosis

A highly specific form of endocytosis where target molecules bind to specific receptors on the cell surface, triggering the membrane to form a coated pit to bring them in.

Extracellular matrix (ECM)

A meshwork of proteins and carbohydrates surrounding animal cells that provides structural support, adhesion, and signaling capability.

Collagen

A protein in the extracellular matrix that provides structural strength.

Elastin

A protein in the extracellular matrix that provides flexibility to tissues.

Fibronectin

An extracellular matrix protein involved in cell adhesion that helps connect the matrix to integrin proteins in the plasma membrane.

Integrins

Membrane proteins that connect the extracellular environment to the inside of the cell and participate in cellular signaling.

Desmosomes

Intercellular junction proteins that hold neighboring animal cells tightly together.

Tight junctions

Intercellular connections that form impermeable seals between adjacent cells.

Gap junctions

Protein channels between neighboring animal cells that allow communication and the direct transfer of materials and signals.

Cell wall

A rigid outer structure surrounding plant cells composed mainly of cellulose that provides structural support.

Plasmodesmata

Narrow channels penetrating plant cell walls that connect the cytoplasm of adjacent plant cells, allowing transport and communication.