CHAPTER 3 – Cell Biology Vocabulary

A set of 30 key vocabulary flashcards covering membrane structure, transport mechanisms, and major cytoskeletal components from Chapter 3 Cell Biology.

Marker Molecule

Glycoprotein or glycolipid on the cell surface that allows cellular recognition, e.g., in immune responses or sperm–oocyte binding.

Transport Protein

Integral membrane protein that moves ions or molecules across the membrane; includes channels, carriers, and ATP pumps.

Channel Protein

Integral protein forming a tiny passageway through the membrane for specific ions or small molecules; can be leak or gated.

Carrier Protein

Integral protein that binds substances, changes shape, and shuttles them across the membrane; shows specificity and saturation.

ATP-Powered Pump

Transport protein that uses energy from ATP hydrolysis to move ions or molecules against their concentration gradient.

Uniport

Carrier-mediated transport that moves one specific type of ion or molecule across a membrane in one direction.

Symport

Coupled transport in which two different substances move together across the membrane in the same direction.

Antiport

Coupled transport in which two different substances move in opposite directions across the membrane.

Ligand-Gated Ion Channel

Membrane channel that opens or closes when a chemical signal (ligand) binds to its receptor site.

Voltage-Gated Ion Channel

Membrane channel that opens or closes in response to changes in membrane potential.

Diffusion

Passive movement of solute molecules from an area of higher concentration to an area of lower concentration.

Osmosis

Diffusion of water across a selectively permeable membrane from a less concentrated to a more concentrated solution.

Facilitated Diffusion

Passive, carrier- or channel-mediated transport of substances down their concentration gradient without ATP use.

Active Transport

Carrier-mediated movement of substances against their concentration gradient using energy derived from ATP.

Secondary Active Transport

Transport that uses the energy of an ion gradient (created by primary active transport) to move another substance.

Endocytosis

Vesicular process by which materials are taken into a cell by enclosing them in a section of plasma membrane that pinches off.

Phagocytosis

‘Cell eating’; form of endocytosis in which cells ingest solid particles, forming large phagocytic vesicles.

Pinocytosis

‘Cell drinking’; form of endocytosis that takes in droplets of extracellular fluid and dissolved molecules via small vesicles.

Receptor-Mediated Endocytosis

Highly specific endocytosis in which extracellular substances bind to receptors, triggering vesicle formation for uptake.

Exocytosis

Vesicular process that releases materials from a cell when vesicles fuse with the plasma membrane.

Cytoskeleton

Network of protein fibers (microtubules, actin filaments, intermediate filaments) that supports cell shape and enables movement.

Microtubule

Hollow tube of tubulin protein that helps form centrioles, spindle fibers, cilia, flagella, and provides intracellular transport tracks.

Actin Filament

Thin protein filament that supports the plasma membrane, forms microvilli cores, and is essential for cell movement and muscle contraction.

Simple Diffusion

Passive movement of substances directly through the lipid bilayer, typically for small, lipid-soluble molecules, without the aid of membrane proteins.

Glycocalyx

The fuzzy, sugary coat formed by glycoproteins and glycolipids on the cell surface, crucial for cell recognition, adhesion, and protection.

Intermediate Filament

Protein fiber in the cytoskeleton (e.g., keratin, vimentin) that provides mechanical strength and maintains cell shape, more stable than actin filaments or microtubules.

Membrane Potential1

Electrical charge difference across the plasma membrane, with the outside positive relative to the inside due to ion distribution.

Fluid-Mosaic Model

Concept describing the plasma membrane as a flexible phospholipid bilayer with proteins and cholesterol ‘floating’ within it.

Phospholipid Bilayer

Double layer of phospholipid molecules forming the core of cellular membranes, with hydrophilic heads outward and hydrophobic tails inward.

Cholesterol (in membranes)

Lipid interspersed among phospholipids that limits their movement and stabilizes membrane fluidity.

Integral Membrane Protein

Protein that penetrates deeply into, and often spans, the lipid bilayer; many function as channels, carriers, or receptors.

Peripheral Membrane Protein

Protein attached to the inner or outer surface of the membrane; often functions as enzymes or structural anchors.

Marker Molecule

Glycoprotein or glycolipid on the cell surface that allows cellular recognition, e.g., in immune responses or sperm–oocyte binding.

Transport Protein

Integral membrane protein that moves ions or molecules across the membrane; includes channels, carriers, and ATP pumps.

Channel Protein

Integral protein forming a tiny passageway through the membrane for specific ions or small molecules; can be leak or gated.

Carrier Protein

Integral protein that binds substances, changes shape, and shuttles them across the membrane; shows specificity and saturation.

ATP-Powered Pump

Transport protein that uses energy from ATP hydrolysis to move ions or molecules against their concentration gradient.

Uniport

Carrier-mediated transport that moves one specific type of ion or molecule across a membrane in one direction.

Symport

Coupled transport in which two different substances move together across the membrane in the same direction.

Antiport

Coupled transport in which two different substances move in opposite directions across the membrane.

Ligand-Gated Ion Channel

Membrane channel that opens or closes when a chemical signal (ligand) binds to its receptor site.

Voltage-Gated Ion Channel

Membrane channel that opens or closes in response to changes in membrane potential.

Diffusion

Passive movement of solute molecules from an area of higher concentration to an area of lower concentration.

Osmosis

Diffusion of water across a selectively permeable membrane from a less concentrated to a more concentrated solution.

Facilitated Diffusion

Passive, carrier- or channel-mediated transport of substances down their concentration gradient without ATP use.

Active Transport

Carrier-mediated movement of substances against their concentration gradient using energy derived from ATP.

Secondary Active Transport

Transport that uses the energy of an ion gradient (created by primary active transport) to move another substance.

Endocytosis

Vesicular process by which materials are taken into a cell by enclosing them in a section of plasma membrane that pinches off.

Phagocytosis

‘Cell eating’; form of endocytosis in which cells ingest solid particles, forming large phagocytic vesicles.

Pinocytosis

‘Cell drinking’; form of endocytosis that takes in droplets of extracellular fluid and dissolved molecules via small vesicles.

Receptor-Mediated Endocytosis

Highly specific endocytosis in which extracellular substances bind to receptors, triggering vesicle formation for uptake.

Exocytosis

Vesicular process that releases materials from a cell when vesicles fuse with the plasma membrane.

Cytoskeleton

Network of protein fibers (microtubules, actin filaments, intermediate filaments) that supports cell shape and enables movement.

Microtubule

Hollow tube of tubulin protein that helps form centrioles, spindle fibers, cilia, flagella, and provides intracellular transport tracks.

Actin Filament

Thin protein filament that supports the plasma membrane, forms microvilli cores, and is essential for cell movement and muscle contraction.

Simple Diffusion

Passive movement of substances directly through the lipid bilayer, typically for small, lipid-soluble molecules, without the aid of membrane proteins.

Glycocalyx

The fuzzy, sugary coat formed by glycoproteins and glycolipids on the cell surface, crucial for cell recognition, adhesion, and protection.

Intermediate Filament

Protein fiber in the cytoskeleton (e.g., keratin, vimentin) that provides mechanical strength and maintains cell shape, more stable than actin filaments or microtubules.

Specificity (in transport)

The property of carrier proteins to bind and transport only certain types of molecules or ions, or groups of closely related molecules.

Saturation (in transport)

The point at which the rate of carrier-mediated transport reaches its maximum because all available carrier proteins are occupied with binding and transporting substances.

Receptor

A protein that binds to specific signaling molecules (ligands), initiating a cellular response.

Concentration Gradient

The difference in concentration of a substance between two areas, which drives diffusion.

Filtration

Movement of fluid and solutes through a membrane from an area of higher hydrostatic pressure to an area of lower hydrostatic pressure.

Selectively Permeable Membrane

A membrane that allows certain substances to pass through freely while restricting the passage of others, crucial for cell regulation.

Leak Channel

A type of channel protein that is always open, allowing specific ions to continuously diffuse across the plasma membrane down their concentration gradients.

Isotonic Solution

A solution with the same solute concentration as the cell, causing no net movement of water across the cell membrane.

Hypotonic Solution

A solution with a lower solute concentration than the cell, leading to water moving into the cell, potentially causing it to swell and burst (lysis).

Hypertonic Solution

A solution with a higher solute concentration than the cell, causing water to move out of the cell, leading to cell shrinkage (crenation).

The property of the plasma membrane that