Anatomy & Physiology: Cell Structure, Membrane Transport, and Cell Communication (4.1–4.6)

A set of vocabulary-style flashcards covering key cellular structures, membrane components, transport mechanisms, signaling, and cell junctions based on the lecture notes.

Plasma membrane

Forms the outer, limiting barrier that separates the cell’s internal contents from the external environment and regulates movement of substances in and out of the cell.

Nucleus

Largest cell structure enclosed by the nuclear envelope; contains genetic material (DNA).

Cytoplasm

All cellular contents between the plasma membrane and nucleus, including cytosol, organelles, and inclusions.

Cytosol

Intracellular fluid; viscous, high water content, and contains dissolved macromolecules and ions.

Organelles

Complex, organized structures within cells; come in membrane-bound and non-membrane-bound forms.

Membrane-bound organelles

Organelles such as rough ER, smooth ER, Golgi apparatus, lysosome, peroxisome, mitochondrion, and vesicles that are enclosed by membranes.

Non-membrane-bound organelles

Organelles like ribosomes, centrosome, proteasomes, and cytoskeleton that lack surrounding membranes.

Ribosomes

RNA-protein complexes that synthesize proteins; can be free-floating or bound to membranes.

Centrosome

Non-membrane-bound organelle that organizes microtubules during cell division.

Proteasomes

Protein complexes that degrade unneeded or damaged proteins.

Cytoskeleton

Network of protein filaments that maintains cell shape and provides mechanical support.

Rough endoplasmic reticulum (RER)

Ribosome-studded ER involved in synthesis and initial modification of proteins.

Smooth endoplasmic reticulum (SER)

ER lacking ribosomes; site of lipid synthesis and detoxification processes.

Golgi apparatus

Stacks of flattened membranes that modify, sort, and package proteins for secretion or delivery to other organelles.

Lysosome

Vesicles containing digestive enzymes that break down waste materials and cellular debris.

Peroxisome

Organelle containing enzymes that break down fatty acids and detoxify harmful substances.

Vesicle

Membrane-bound sac used to transport materials within the cell or to the plasma membrane.

Nucleolus

Dense region within the nucleus where ribosomal RNA (rRNA) synthesis occurs.

Nuclear envelope

Double membrane surrounding the nucleus that contains nuclear pores for transport.

Nucleoplasm

Substance within the nucleus containing chromatin and nucleolus.

Phospholipids

Membrane lipids with polar, hydrophilic heads and nonpolar, hydrophobic tails; form the bilayer.

Phospholipid bilayer

Two parallel sheets of phospholipid molecules that form the basic framework of the plasma membrane.

Polar head

Hydrophilic region of a phospholipid that faces aqueous environments.

Glycolipids

Lipids with carbohydrate groups that contribute to glycocalyx on the cell surface.

Cholesterol

Sterol interspersed within the phospholipid bilayer that helps regulate membrane fluidity and stability.

Glycocalyx

Carbohydrate-rich coating on the cell surface involved in cell recognition and protection.

Integral proteins

Membrane proteins embedded within the lipid bilayer, often spanning the membrane.

Peripheral proteins

Proteins attached to the exterior or interior surfaces of the membrane, not embedded in the bilayer.

Transport proteins

Proteins that facilitate movement of substances across the plasma membrane.

Channel proteins

Proteins that form pores allowing specific ions to pass through the membrane.

Carrier proteins

Proteins that change shape to transport substances across the membrane, often down a gradient.

Pumps

Transport proteins that move substances against their concentration gradient using energy.

Receptors

Membrane proteins that bind ligands to trigger cellular responses.

Identity markers

Cell-surface proteins that help distinguish healthy cells from cells to be destroyed.

Enzymes

Proteins that catalyze biochemical reactions and may be membrane-associated.

Anchoring sites

Locations where the cytoskeleton attaches to the plasma membrane to stabilize the cell.

Cell-adhesion proteins

Proteins that promote cell-to-cell attachments and tissue architecture.

Ligand

Molecule that binds to a receptor to trigger a response.

Channel-linked receptors

Receptors that open ion channels in response to ligand binding, initiating electrical changes.

Enzymatic receptors

Receptors that activate protein kinases to phosphorylate target enzymes.

G protein-coupled receptors

Receptors that transmit signals via G proteins to activate intracellular pathways.

Diffusion

Net movement of a substance from an area of higher concentration to lower concentration due to kinetic energy.

Simple diffusion

Diffusion of small, nonpolar solutes through the phospholipid bilayer along a concentration gradient.

Facilitated diffusion

Diffusion of small charged or polar solutes with the help of membrane proteins.

Channel-mediated diffusion

Movement of ions through water-filled channels; channels may be leak or gated.

Carrier-mediated diffusion

Transport of small polar molecules by carrier proteins, down their gradient (uniporter).

Aquaporin

Water channel protein that facilitates osmosis across the membrane.

Osmosis

Movement of water across a semipermeable membrane, driven by solute concentration differences.

Permeable solutes

Solutes that can cross the lipid bilayer (e.g., oxygen, carbon dioxide, urea).

Nonpermeable solutes

Solutes that cannot cross the lipid bilayer (e.g., many ions, glucose, proteins).

Osmotic pressure

Pressure exerted by water movement across a semipermeable membrane due to solute differences.

Isotonic

Solution with the same solute concentration as cytosol; no net water movement.

Hypotonic

Solution with lower solute concentration than cytosol; water moves into the cell, causing swelling.

Hypertonic

Solution with higher solute concentration than cytosol; water moves out, causing cell shrinkage.

Hydrostatic pressure

Pressure exerted by a fluid on the walls of its container; related to fluid balance concepts in osmosis.

Primary active transport

Active transport that uses energy directly from ATP breakdown to change a transport protein’s shape.

Sodium–potassium pump (Na+/K+ pump)

Active transport that exports Na+ and imports K+ to maintain electrochemical gradients.

ATP

Energy currency of the cell; provides energy for primary active transport via phosphorylation.

Secondary active transport

Active transport that uses the gradient of one substance to drive the movement of another (no direct ATP).

Symport

Secondary active transport where two substances move in the same direction via a carrier.

Antiport

Secondary active transport where two substances move in opposite directions.

Vesicular transport

Bulk transport that uses vesicles to move large substances across the plasma membrane.

Exocytosis

Vesicle fuses with the plasma membrane to release its contents outside the cell.

Endocytosis

Vesicle formation that brings material into the cell from the extracellular space.

Phagocytosis

Cellular eating; engulfment of large particles by pseudopodia and lysosomal digestion.

Pinocytosis

Cellular drinking; uptake of small droplets of interstitial fluid via vesicles.

Receptor-mediated endocytosis

Endocytosis initiated when ligands bind to cell-surface receptors and are internalized via clathrin-coated pits.

Clathrin-coated pit

Specialized membrane region that facilitates receptor-mediated endocytosis by forming vesicles.

LDL receptor

Receptor that binds low-density lipoproteins and mediates cholesterol uptake into cells.

Direct cell contact

Direct interactions between cells important for immune function, fertilization recognition, and tissue repair.

Ligand-receptor signaling

Cell communication initiated by ligand binding to receptors, affecting cellular responses.

Channel-linked receptors

Ligand-activated receptors that open ion channels to alter membrane potential.

Enzymatic receptors

Receptors that activate protein kinases to phosphorylate intracellular targets.

G protein-coupled receptors

Receptors that transmit signals via G proteins to regulate intracellular processes.

Tight junctions

Junctions that seal adjacent cells to prevent passage between cells.

Desmosomes

Junctions that bind neighboring cells together, providing mechanical stability.

Hemidesmosomes

Junctions that anchor basal cells to the basement membrane.

Gap junctions

Channels formed by connexons that provide direct cytoplasmic passageways between cells.

Microvilli

Membrane extensions that increase surface area for absorption.

Cilia

Hair-like projections that move substances along the cell surface.

Flagellum

Long projection that propels the cell.