Cell Structure and Function

Cell Membrane

The structure that surrounds all animal cells and separates the cytoplasm from the external environment.

Physical Isolation

The function of the cell membrane to separate the internal cellular environment from the external environment.

Regulation of Exchange

The function of the cell membrane to control the exchange of ions, nutrients, waste, and products between the cell and its surroundings.

Communication

The function of the cell membrane to allow recognition and response to the external environment through proteins.

Structural Support

The function of the cell membrane to attach to the cytoskeleton, adjacent cells, and extracellular matrix for support.

Plasma Membrane

The main component of cell membranes, composed mostly of proteins, lipids, and carbohydrates.

Phospholipids

The molecules that make up the phospholipid bilayer of the cell membrane.

Membrane Steroid Cholesterol

A membrane component that acts as a temperature buffer and maintains fluidity in the cell membrane.

Glycocalyx

The protective layer on the external surface of the cell membrane consisting of glycoproteins and glycolipids. Serves as identity markers for cell-cell recognition.

Integral Proteins

Proteins that penetrate the hydrophobic core of the lipid bilayer.

Transmembrane Proteins

Integral proteins that protrude into both the cytoplasm and the extracellular fluid.

Membrane Proteins

Proteins in the cell membrane that have various functions, including transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, and attachment to the cytoskeleton and extracellular matrix.

Carrier Proteins

Proteins in the membrane that are ideal for transporting glucose, amino acids, or molecules that are too large. Are more specific in what they transport.

Signal Transduction

Receptors that bind to ligands, chemical messengaers, that trigger the channel to open

Enzyme

Thing that speeds up chemical reactions

Cell Junctions

Long-lasting or permanent connections between adjacent cells.

Tight Junctions

Cell junctions that connect cells into sheets and create a tight seal, preventing substances from passing between cells.

Anchoring Junctions

Cell junctions that attach the cytoskeleton of a cell to the matrix surrounding the cell or the cytoskeleton of an adjacent cell.

Communicating (Gap) Junctions

Cell junctions that link the cytoplasms of two cells together, allowing controlled passage of small molecules or ions between them.

Passive Transport

The type of membrane transport that transports molecules via diffusion and does not require energy.

Active Transport

The type of membrane transport that requires an energy source, such as ATP, to transport molecules.

Diffusion

The net movement of a substance from an area of high concentration to an area of low concentration.

Dialysis

Type of diffusion that selectively diffuses solutes that are typically lipid soluble

Selective Permeability

The property of the cell membrane that allows specific molecules to cross while prohibiting the passage of others.

Facilitated Diffusion

Diffusion that uses membrane proteins to transport large polar molecules across the cell membrane. Requires a protein carrier or channel. A form of passive transport.

Non lipid soluble = polar molecules/ions =

Hydrophilic = Lipophobic

Lipid soluble = nonpolar molecules/ions

Hydrophobic = Lipophilic

Osmosis

The diffusion of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

Aquaporins

Channel proteins that facilitate the osmosis of water across the cell membrane, typically the primary route.

Osmotic Pressure

The pressure or force exerted to prevent inward flow of water across a semipermeable membrane toward a higher concentration of solutes.

Tonicity

The way a solution affects the volume of a cell.

Hypertonic

A solution with a high solute concentration that causes a cell to lose water and shrink.

Hypotonic

A solution with a low solute concentration that causes a cell to gain water and swell.

Isotonic

A solution with an equal solute concentration that does not change the size of a cell.

Active Transport

The transport of molecules against their concentration gradient using energy from ATP.

Membrane Pump

A protein-mediated active transport that uses energy from ATP to move substances against their concentration gradient.

The Na+/K+ Pump

Most important membrane pump that transports 3Na+ out and 2 K+ in per ATP consumed

Coupled Transport/Cotransport

A form of active transport where the carrier protein uses ATP to move a substance one across the membrane and storing potential energy.

Vesicles

Small sacs filled with large molecules too bigg to transport by other means that are enclosed in phospholipid bilayer.

Endocytosis

The process of cells absorbing external material by engulfing it in a vesicle.

Phagocytosis

“Cell Eating” or process where cells ingest large particles like bacteria, dead/damaged cells, or parts of the cell

Pinocytosis

“Cell Drinking” or process where cells engulf fluid droplets from ECF

Exocytosis

The process of large molecules exiting the cell by fusing vesicles with the plasma membrane.

Transcytosis

The process of molecules being brought into the cell through endocytosis, transported to the other side of the cell, and then secreted through exocytosis.

Prokaryotic Cells

Cells that do not have a nucleus or distinct interior compartments. They have cytoplasm and may have a flagellum for locomotion. Examples include bacteria.

Eukaryotic Cells

Cells characterized by the presence of membrane-bound organelles and compartmentalization. They have a nucleus and other components such as central vacuole, vesicles, chromosomes, cytoskeleton, and cell walls.

Nucleus

The central organelle that holds the genetic material (chromatin) in the form of DNA and protein. It contains the nucleolus, nuclear envelope, nucleoplasm, and chromosomes.

Ribosomes

RNA-protein complexes where protein synthesis occurs. They are assembled in the nucleoli and attach to messenger RNA.

Endomembrane System

A system of membranes that divides the cell and channels molecules passing through the cell interior. It includes the endoplasmic reticulum and Golgi apparatus.

Endoplasmic Reticulum

A network of membrane tubules involved in protein and lipid synthesis. Rough ER has ribosomes attached to it, while smooth ER lacks ribosomes and is involved in metabolic processes.

Golgi Apparatus

The shipping and receiving center for cell products. It processes and packages proteins for transport to their final destinations.

Lysosomes

Vesicles containing digestive enzymes that break down food and foreign particles.

Vacuoles

Membrane-bound organelles involved in food storage and water regulation.

Peroxisomes

Organelles containing enzymes that catalyze the removal of electrons and associated hydrogen atoms.

Mitochondria

Organelles where cellular respiration takes place and ATP is synthesized. They have a double membrane and contain a fluid-filled matrix and cristae.

Cytoskeleton

A network of filaments that provides shape, structure, and movement within the cell. It includes intermediate filaments, actin filaments, and microtubules.

Centrioles

Short cylinders involved in cell movement, working with microtubules. Has a 9+0 pattern.

Cilia

Small, numerous structures involved in cell movement on the surface of cells.

Flagellum

A large, single structure used by cells to move itself along.

Cell Junctions

Long-lasting connections between adjacent cells. There are three types:tight junctions, desmosomes, and gap junctions.