| Term | Definition |
|---|---|
| chloroplasts | Specialized organelles found in plants and photosynthetic algae that contain a double membrane and serve as the location for photosynthesis. |
| compartmentalization | The division of the eukaryotic cell into distinct membrane-bound regions that separate different metabolic processes and enzymatic reactions. |
| endosymbiosis | The process by which free-living prokaryotic cells were engulfed by larger cells and became membrane-bound organelles. |
| eukaryotic cell | Cells that contain a membrane-bound nucleus and internal membrane-bound organelles, found in animals, plants, fungi, and protists. |
| internal membrane | Membranes within eukaryotic cells that divide the cell into compartments with specialized functions. |
| membrane-bound organelle | Specialized structures within eukaryotic cells enclosed by a membrane that perform specific cellular functions. |
| mitochondria | Membrane-bound organelles in eukaryotic cells that are the primary site of aerobic cellular respiration and ATP synthesis. |
| prokaryotic cell | Cells that lack a membrane-bound nucleus and internal membrane-bound organelles, typically bacteria and archaea. |
| Term | Definition |
|---|---|
| adenosine triphosphate | The primary energy currency of cells that powers cellular functions. |
| aerobic cellular respiration | The metabolic pathway that uses oxygen as the terminal electron acceptor to generate ATP from biological macromolecules. |
| chemical modification | Changes made to proteins in the Golgi that affect their function or cellular location. |
| chloroplasts | Specialized organelles found in plants and photosynthetic algae that contain a double membrane and serve as the location for photosynthesis. |
| double membrane | Two layers of membrane found in mitochondria and chloroplasts that create separate compartments for different cellular processes. |
| endomembrane system | A group of membrane-bound organelles and subcellular components that work together to modify, package, and transport polysaccharides, lipids, and proteins within cells. |
| endoplasmic reticulum (ER) | A membrane-bound organelle that provides mechanical support, maintains cell shape, and plays a role in intracellular transport. |
| glycosylation | A chemical modification of proteins that takes place within the Golgi and determines protein function or targeting. |
| Golgi complex | A membrane-bound organelle consisting of flattened membrane sacs that folds and chemically modifies newly synthesized proteins and packages them for trafficking. |
| hydrolytic enzyme | Enzymes found in lysosomes that break down and digest cellular materials. |
| intracellular transport | The movement of materials within a cell, facilitated by organelles like the endoplasmic reticulum. |
| lipid | Hydrophobic or amphipathic biological molecules composed primarily of carbon, hydrogen, and oxygen that store energy and form cell membranes. |
| lipid synthesis | The production of lipids, a function carried out by smooth endoplasmic reticulum. |
| lysosomes | Membrane-enclosed sacs that contain hydrolytic enzymes for digesting material and play a role in programmed cell death. |
| mitochondria | Membrane-bound organelles in eukaryotic cells that are the primary site of aerobic cellular respiration and ATP synthesis. |
| nuclear envelope | A membrane-bound component of the endomembrane system that surrounds the nucleus. |
| organelle | Membrane-bound or non-membrane-bound structures within eukaryotic cells that perform specific cellular functions. |
| photosynthesis | The series of reactions that use carbon dioxide, water, and light energy to produce carbohydrates and oxygen, allowing organisms to capture and store energy from the sun. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| polysaccharides | Complex carbohydrates formed by linking many monosaccharide monomers together through covalent bonds. |
| programmed cell death | Programmed cell death, a controlled process in which a cell actively participates in its own destruction. |
| protein | Macromolecules composed of amino acids linked together, containing carbon, hydrogen, oxygen, nitrogen, and often sulfur, that perform diverse functions in cells. |
| protein synthesis | The process by which ribosomes build proteins according to mRNA sequences. |
| ribosomes | Non-membrane subcellular structures composed of ribosomal RNA and protein that synthesize proteins according to messenger RNA sequences. |
| rough endoplasmic reticulum | Endoplasmic reticulum with attached ribosomes on its cytoplasmic surface; site of synthesis for proteins destined for secretion or membrane insertion. |
| smooth endoplasmic reticulum | Endoplasmic reticulum that functions in the detoxification of cells and lipid synthesis. |
| subcellular component | Structures within a cell that perform specific functions, including both membrane-bound organelles and non-membrane structures. |
| transport vesicle | Membrane-bound structures that are part of the endomembrane system and transport materials between organelles. |
| turgor pressure | The pressure maintained in plant cells by a large vacuole through nutrient and water storage. |
| vacuole | Membrane-bound sacs that store cellular materials and play various roles in plant and animal cells. |
| Term | Definition |
|---|---|
| heat exchange | The transfer of thermal energy between an organism's body and the surrounding environment; rate decreases as organism size increases. |
| membrane folds | Infoldings of the cell membrane that increase surface area to facilitate more efficient material exchange in complex cells. |
| metabolic rate | The rate at which an organism uses energy; typically higher per unit body mass in smaller organisms than in larger organisms. |
| nutrient exchange | The process by which cells obtain necessary nutrients from the environment. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| surface area-to-volume ratio | The relationship between the total surface area and the total volume of a cell or organism; affects the efficiency of material exchange with the environment. |
| thermal energy exchange | The transfer of heat energy between an organism and its environment. |
| waste products | Byproducts of cellular metabolism that must be eliminated from cells or organisms. |
| Term | Definition |
|---|---|
| cholesterol | A steroid molecule found in the plasma membranes of vertebrate animals that regulates membrane fluidity and stability. |
| cytosol | The aqueous interior of the cell where hydrophilic protein regions may be exposed. |
| embedded protein | Proteins that are integrated into or span across the phospholipid bilayer of the cell membrane. |
| fatty acid | Organic compounds consisting of a carboxyl group attached to a long hydrocarbon chain; can be saturated or unsaturated. |
| fluid mosaic model | A model describing the plasma membrane as a flexible structure composed of a phospholipid bilayer with embedded and peripheral proteins that can move laterally within the membrane. |
| glycolipid | A lipid with carbohydrate chains attached, found in the plasma membrane and involved in cell recognition. |
| glycoprotein | A protein with carbohydrate chains attached, found in the plasma membrane and involved in cell recognition and signaling. |
| hydrophilic | Water-loving; referring to polar molecules or regions that interact favorably with water. |
| hydrophobic | Water-repelling; referring to nonpolar molecules or regions that do not interact favorably with water. |
| nonpolar | Referring to molecules or groups with even distribution of electrical charge, making them hydrophobic. |
| phosphate | A chemical group that is part of the nucleotide structure and forms covalent bonds between nucleotides in a nucleic acid strand. |
| phospholipid | Amphipathic molecules with hydrophilic phosphate heads and hydrophobic fatty acid tails that form the basic structure of the cell membrane. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| polar | Referring to molecules or groups with uneven distribution of electrical charge, making them hydrophilic. |
| protein | Macromolecules composed of amino acids linked together, containing carbon, hydrogen, oxygen, nitrogen, and often sulfur, that perform diverse functions in cells. |
| steroid | Lipids with a four-ring carbon structure that function as hormones supporting growth, development, energy metabolism, and homeostasis. |
| Term | Definition |
|---|---|
| cell wall | A rigid structural layer outside the cell membrane that provides support, maintains cell shape, and acts as a permeability barrier in bacteria, archaea, fungi, and plants. |
| hydrocarbon tail | The nonpolar, hydrophobic portions of phospholipids that form the interior of the membrane and prevent ion and polar molecule movement. |
| hydrophilic substance | Water-loving polar molecules and ions that cannot easily cross the hydrophobic membrane interior and require transport proteins or channels. |
| hydrophobic interior | The nonpolar region in the middle of the phospholipid bilayer that repels water and polar molecules. |
| ion | Charged particles that cannot freely cross the hydrophobic membrane interior and require transport proteins or channels for movement. |
| nonpolar molecule | Molecules that lack a net electric charge and can pass freely across the hydrophobic interior of the membrane. |
| osmotic lysis | The rupture of a cell membrane due to water entering the cell in a hypotonic environment; prevented by the cell wall in plant cells, bacteria, archaea, and fungi. |
| permeability barrier | A selective barrier that controls which substances can pass between the internal and external cellular environments. |
| phospholipid | Amphipathic molecules with hydrophilic phosphate heads and hydrophobic fatty acid tails that form the basic structure of the cell membrane. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| polar molecule | Molecules with uneven distribution of electrical charge that generally cannot cross the hydrophobic membrane interior without assistance. |
| selective permeability | The property of a membrane that allows certain substances to pass through while restricting the passage of others. |
| structural boundary | The physical barrier provided by the cell wall that defines and maintains the shape and integrity of the cell. |
| transport protein | Embedded membrane proteins that facilitate the movement of hydrophilic substances across the membrane. |
| Term | Definition |
|---|---|
| active transport | The movement of ions and molecules across a membrane against their concentration gradient, requiring metabolic energy from ATP. |
| concentration gradient | A difference in the concentration of a substance across a membrane, with higher concentration on one side and lower concentration on the other. |
| endocytosis | A process in which a cell takes in large molecules and particulate matter by folding the plasma membrane inward to form vesicles that engulf external material. |
| exocytosis | A process in which internal vesicles fuse with the plasma membrane to release large molecules and other materials from the cell. |
| metabolic energy | Energy derived from cellular metabolism, typically in the form of ATP, used to power cellular processes. |
| passive transport | The net movement of molecules from regions of high concentration to regions of low concentration without the direct input of metabolic energy. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| selective permeability | The property of a membrane that allows certain substances to pass through while restricting the passage of others. |
| solute | A substance dissolved in a solvent to form a solution; the component present in smaller amount in a solution. |
| vesicle | Small membrane-bound sacs that transport and store materials within or between cells. |
| water balance | The regulation of water movement into and out of cells to maintain proper cellular function and organism homeostasis. |
| Term | Definition |
|---|---|
| aquaporins | Channel proteins that facilitate the rapid transport of water molecules across cell membranes. |
| channel protein | Membrane proteins that form pores or channels allowing specific ions or molecules to pass through the plasma membrane. |
| charged ion | Atoms or molecules that have gained or lost electrons and carry an electrical charge, such as sodium (Na⁺) and potassium (K⁺). |
| concentration gradient | A difference in the concentration of a substance across a membrane, with higher concentration on one side and lower concentration on the other. |
| facilitated diffusion | The passive transport of substances across a membrane through protein channels or carriers, requiring no energy input but moving down the concentration gradient. |
| membrane polarization | The development of an electrical charge difference across a membrane caused by the movement of ions. |
| plasma membrane | The selectively permeable membrane that surrounds the cell, composed of phospholipids, proteins, and other molecules that regulate what enters and exits the cell. |
| polar molecule | Molecules with uneven distribution of electrical charge that generally cannot cross the hydrophobic membrane interior without assistance. |
| transport protein | Embedded membrane proteins that facilitate the movement of hydrophilic substances across the membrane. |
| Term | Definition |
|---|---|
| central vacuole | A large organelle in plant cells that stores water and solutes, playing a role in maintaining turgor pressure and osmoregulation. |
| concentration gradient | A difference in the concentration of a substance across a membrane, with higher concentration on one side and lower concentration on the other. |
| contractile vacuole | An organelle in protists that collects and expels excess water to maintain osmotic balance. |
| homeostasis | The maintenance of stable internal environmental conditions in an organism despite external and internal changes. |
| hypertonic | A solution with a higher solute concentration relative to another solution, causing water to move out of the cell. |
| hypotonic | A solution with a lower solute concentration relative to another solution, causing water to move into the cell. |
| isotonic | A solution with the same solute concentration as another solution, resulting in no net movement of water across the membrane. |
| osmolarity | The concentration of solutes in a solution, which determines the direction of water movement across membranes. |
| osmoregulation | The process by which organisms maintain water balance and control their internal solute composition and water potential. |
| osmoregulatory mechanism | Physiological processes that organisms use to maintain water balance and regulate internal solute composition. |
| osmosis | The movement of water across a semipermeable membrane from regions of high water potential to regions of low water potential. |
| pressure potential | The component of water potential representing the physical pressure exerted on water in a cell, often due to cell wall rigidity. |
| solute concentration | The amount of dissolved solutes per unit volume of solution, which affects water movement across membranes. |
| solute potential | The component of water potential that represents the effect of dissolved solutes in lowering the potential energy of water. |
| water balance | The regulation of water movement into and out of cells to maintain proper cellular function and organism homeostasis. |
| water potential | The potential energy of water in a system, determined by pressure potential and solute potential, that drives water movement. |
| Term | Definition |
|---|---|
| active transport | The movement of ions and molecules across a membrane against their concentration gradient, requiring metabolic energy from ATP. |
| ATPase | An enzyme that catalyzes the breakdown of ATP to release energy for active transport and other cellular processes. |
| electrochemical gradient | The combined effect of the concentration gradient and electrical potential difference across a membrane that influences ion movement. |
| membrane potential | The electrical potential difference across a cell membrane, maintained by the Na⁺/K⁺ pump and other ion pumps. |
| membrane protein | Proteins embedded in or attached to the cell membrane that facilitate the transport of molecules and ions across the membrane. |
| Na⁺/K⁺ pump | An active transport protein that uses ATP to move sodium ions out of the cell and potassium ions into the cell, maintaining the membrane potential. |
| Term | Definition |
|---|---|
| compartmentalization | The division of the eukaryotic cell into distinct membrane-bound regions that separate different metabolic processes and enzymatic reactions. |
| enzymatic reaction | Chemical reactions catalyzed by enzymes that occur within specific cellular compartments to facilitate metabolic processes. |
| eukaryotic cell | Cells that contain a membrane-bound nucleus and internal membrane-bound organelles, found in animals, plants, fungi, and protists. |
| internal membrane | Membranes within eukaryotic cells that divide the cell into compartments with specialized functions. |
| intracellular metabolic process | Chemical reactions and pathways that occur within the cell to build up or break down molecules for energy and biosynthesis. |
| membrane-bound organelle | Specialized structures within eukaryotic cells enclosed by a membrane that perform specific cellular functions. |
| membrane-bound structure | Organelles and compartments in eukaryotic cells that are enclosed by a lipid bilayer membrane, separating their contents from the cytoplasm. |
| organelle | Membrane-bound or non-membrane-bound structures within eukaryotic cells that perform specific cellular functions. |
| surface area | The total area of a membrane available for chemical reactions and cellular processes to occur. |