Cell Biology and Transport Mechanisms Flashcards

Vocabulary practice flashcards covering cell anatomy, organelle functions, and membrane transport processes based on Chapter 2 lecture notes.

Plasma Membrane

A selectively permeable fluid barrier stabilized by cholesterol that controls the entry and passage of substances between intracellular and extracellular environments.

Fluid Mosaic Model

The structural description of the plasma membrane in which specialized membrane proteins float through a fluid phospholipid bilayer, creating constantly changing patterns.

Phospholipid Bilayer

A two-layered membrane structure composed of water-soluble heads facing the outer surfaces and water-insoluble tails forming the interior, permeable to lipid-soluble substances.

Simple Diffusion

An unassisted passive movement of substances such as $O_2$, $CO_2$, and lipid-soluble molecules from a region of higher concentration to a region of lower concentration down a concentration gradient.

Facilitated Diffusion

Passive movement of large or insoluble molecules (such as glucose and amino acids) down their concentration gradient across a membrane via transmembrane protein carriers or water-filled protein channels.

Osmosis

A passive process involving the movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration.

Osmotic Pressure

The ability of osmosis to generate enough pressure to move a volume of water, which increases as the concentration of nonpermeable solutes increases.

Isotonic Solution

A solution that possesses the same osmotic pressure as the internal cellular fluid.

Hypotonic Solution

A solution that possesses a lower osmotic pressure than the internal cellular fluid.

Hypertonic Solution

A solution that possesses a higher osmotic pressure than the internal cellular fluid.

Primary Active Transport

An active process in which the cell expends energy (ATP) directly through transport proteins to move substances across the membrane against their concentration gradient.

Na+/K+ ATPase Pump

A primary active transport mechanism that expends ATP to move $3\text{ Na}^+$ ions out of the cell for every $2\text{ K}^+$ ions brought into the cell.

Endocytosis

An active vesicular transport process that brings substances into a cell within vesicles formed by infolding of the plasma membrane.

Phagocytosis

A form of endocytosis known as 'cell eating,' in which pseudopods engulf solid particles or bacteria to form a phagosome.

Pinocytosis

A form of endocytosis known as 'cell drinking' (bulk-phase endocytosis), involving the infolding of the plasma membrane to engulf extracellular fluid into a vesicle.

Exocytosis

An active transport process where substances are moved out of a cell in secretory vesicles that fuse with the plasma membrane to release contents into extracellular fluid.

Transcytosis

An active process involving the movement of a substance through a cell as a result of endocytosis on one side and exocytosis on the opposite side.

Receptor-Mediated Endocytosis

A selective form of endocytosis where ligand-receptor complexes trigger the infolding of a clathrin-coated pit to form a vesicle containing ligands.

Cytoplasm

The cellular contents located between the plasma membrane and the nucleus, consisting of cytosol, cytoplasmic organelles, and inclusions.

Cytosol

The fluid portion of the cytoplasm, largely made of water containing dissolved proteins, salts, sugars, and other solutes.

Mitochondria

Double-membrane organelles containing shelf-like cristae, matrix, and their own DNA and RNA that produce most of the cell's ATP through aerobic cellular metabolism.

Ribosomes

Small granules composed of protein and rRNA consisting of a large subunit and a small subunit that function as the site of protein synthesis.

Rough Endoplasmic Reticulum

A membranous network studded with ribosomes that serves as a 'membrane factory,' manufacturing all secreted proteins, integral membrane proteins, and membrane phospholipids.

Smooth Endoplasmic Reticulum

A network of membranous tubules lacking ribosomes that functions in lipid/cholesterol metabolism and drug detoxification in the liver, steroid hormone synthesis in testes, and calcium storage/release in muscle.

Golgi Apparatus

A stack of flattened membranous sacs that receives transport vesicles from the ER at its cis face to modify, concentrate, and package proteins into secretory vesicles at its trans face.

Cytoskeleton

An elaborate scaffolding of microfilaments, intermediate filaments, and microtubules running through the cytosol that supports cellular structure and movements.

Nucleus

The gene-containing control center of the cell that houses the genetic library, chromatin, and nucleolus, dictating protein synthesis.

Nuclear Envelope

A selectively permeable double membrane barrier penetrated by nuclear pores that encloses the nucleoplasm and essential solutes.