Cells and the Plasma Membrane - Vocabulary

Vocabulary flashcards covering key terms related to the plasma membrane, cell components, and cellular transport from the lecture notes.

Cell theory

The cell is the smallest unit of life; all organisms are made of one or more cells; cells arise from other cells (mitosis for most body cells; meiosis for sperm/egg).

Complementarity of structure and function

Cell activities are dictated by their shape and by the types and numbers of subcellular structures they contain.

Intracellular fluid (ICF)

Fluid inside cells; about two-thirds of the body's water.

Extracellular fluid (ECF)

Fluid outside cells; about one-third of body water; includes plasma and interstitial fluid.

Interstitial fluid (IF)

Fluid in tissue spaces; constitutes about 80% of the extracellular fluid.

Plasma (intravascular fluid)

Liquid component of blood circulating within blood vessels; makes up about 20% of extracellular fluid.

Plasma membrane

The cell's outer boundary; acts as a selectively permeable barrier.

Cytoplasm

Intracellular fluid containing organelles where cell parts function.

Nucleus

Organelle that controls cellular activities and houses genetic material.

Nucleolus

Site inside the nucleus where ribosomal RNA synthesis occurs.

Endoplasmic reticulum

Network of membranous tubules; rough ER synthesizes proteins, smooth ER synthesizes lipids.

Golgi complex

Organelle that packages, modifies, and ships proteins and lipids for secretion or delivery.

Mitochondria

Powerhouse of the cell; generates ATP through cellular respiration.

Phospholipid bilayer

Membrane structure formed by phospholipids and cholesterol; hydrophilic heads face outward, hydrophobic tails inward.

Phospholipid

Lipid with a polar head (hydrophilic) and nonpolar tail (hydrophobic) that forms the membrane's basic structure.

Cholesterol (in membranes)

Steroid that stiffens the membrane and decreases water solubility; helps maintain membrane fluidity.

Integral (intrinsic) proteins

Proteins embedded within the lipid bilayer; functions include transport and signaling.

Peripheral (extrinsic) proteins

Proteins attached to the outer or inner membrane surface; support membrane function.

Carbohydrates (on the membrane)

Identity molecules on the outer membrane that aid in cell recognition and interaction.

Glycocalyx

Glycoconjugate coating formed by membrane carbohydrates that covers the cell surface.

Membrane transport

Movement of substances across the plasma membrane.

Lipid solubility

Higher lipid solubility increases a molecule's ability to diffuse through the membrane.

Concentration gradient

Difference in concentration of a substance from one area to another; drives diffusion.

Simple diffusion

Unassisted diffusion of small or nonpolar molecules across the membrane down their concentration gradient; no energy required.

Facilitated diffusion

Diffusion that requires transport proteins (carriers or channels) but no direct energy input.

Carrier-mediated diffusion

Facilitated diffusion that uses a carrier protein to move solutes across the membrane.

Channel-mediated diffusion

Facilitated diffusion where ions pass through membrane channels based on size/charge.

Osmosis

Diffusion of water across a selectively permeable membrane.

Osmolarity

Total solute concentration of a solution.

Isotonic

Solution has the same solute concentration as the cell, so cell shape remains stable.

Hypertonic

Solution with higher solute concentration than the cell; cells lose water and shrink.

Hypotonic

Solution with lower solute concentration than the cell; cells swell as water enters.

Primary active transport

Energy-requiring pumping of substances against a gradient using ATP (e.g., Na+/K+-ATPase).

Na+/K+-ATPase

A primary active transport pump that moves Na+ out and K+ into the cell, maintaining gradients.

Secondary active transport

Transport driven by energy stored in ion gradients created by primary active transport.

Vesicular transport

Movement of substances in membrane-bound vesicles; includes endocytosis and exocytosis.

Endocytosis

Process of taking material into the cell via vesicle formation.

Exocytosis

Process of releasing material from the cell via vesicle fusion with the plasma membrane.

Phagocytosis

Cellular eating; ingestion of solid particles into phagocytic vesicles.

Pinocytosis

Cellular drinking; ingestion of extracellular fluids via vesicles.

Receptor-mediated endocytosis

Selective uptake of molecules via specific cell-surface receptors and vesicles.

Membrane potential

Voltage difference across the plasma membrane due to ion distributions.

Ion gradient

Differing concentrations of ions inside versus outside the cell.

Ion pumps

Pumps that actively move ions against their gradient (e.g., Na+/K+-ATPase).

Tight junctions

Impermeable junctions that seal cells together to prevent passage of substances (e.g., gut epithelium).

Desmosomes

Anchoring junctions that resist tearing and provide mechanical strength (skin, heart).

Gap junctions

Communicating junctions that allow ions and small molecules to pass between cells (e.g., heart).