Cell Structure and Function Study Guide

Comprehensive vocabulary flashcards covering cell organelles, compartmentalization, membrane structure, mechanisms of cellular transport, and tonicity/water potential concepts.

Cell Membrane (Plasma Membrane)

A semi-permeable outer barrier found in all cells that controls the movement of materials into and out of the cell.

Cell Wall

A strong outer layer located outside the cell membrane in plant cells, fungi, some protists, and bacteria; it provides structural support, protection against mechanical and pathogen damage, and withstands internal turgor pressure to prevent bursting.

Cytoplasm (Cytosol)

The inner gel fluid present in all cells that serves as the location for many cellular processes.

Cytoskeleton

A network of protein fibers that anchor and move organelles throughout the cell and assist in cell division.

Chloroplast

A specialized double-membrane organelle containing inner folds and fluids in photosynthetic cells that captures and stores solar energy as glucose.

Golgi Apparatus

A stack of flattened membranes that functions as the processing, tagging, and transport center for proteins leaving the cell.

Lysosomes

Membrane-bound sacs containing digestive enzymes that break down worn-out cell parts and facilitate apoptosis.

Apoptosis

Programmed cell death carried out through the release of digestive enzymes stored within lysosomes.

Mitochondria

Specialized double-membrane organelles with internal folds and fluids found in all eukaryotic cells that convert glucose into usable cellular energy ($ATP$).

Nucleus

An organelle enclosed by a nuclear envelope that stores the cell's genetic material ($DNA$).

Ribosomes

Cellular structures responsible for protein synthesis; located on the rough endoplasmic reticulum (producing proteins for export outside the cell) and freely in the cytoplasm (producing proteins for use inside the cell).

Rough Endoplasmic Reticulum (RER)

A membrane-bound organelle studded with ribosomes on its surface that folds and processes newly made proteins before packaging them into vesicles for delivery to the Golgi apparatus.

Smooth Endoplasmic Reticulum (SER)

A membrane-bound organelle lacking ribosomes that synthesizes lipids and breaks down toxins.

Vacuoles

Organelles that store water and nutrients; in plant cells, a large central vacuole is responsible for generating internal turgor pressure.

Vesicles

Small, membrane-bound transport spheres used in the endomembrane pathway, endocytosis, and exocytosis.

Endomembrane Pathway

The coordinated organelle process of protein secretion: proteins synthesized by RER ribosomes are folded in the RER, transported via vesicle to the Golgi apparatus for processing and tagging, and carried by another vesicle that fuses with the plasma membrane to release proteins through exocytosis.

Cell Compartmentalization

The formation of distinct internal areas within membrane-bound organelles that isolate chemical reactions and optimize metabolic efficiency.

Endosymbiotic Theory

The theory proposing that mitochondria and chloroplasts originated as independent prokaryotic organisms that were engulfed by ancestral eukaryotic cells, supported by their circular bacterial-like $DNA$, bacterial-like ribosomes, double membranes, and self-replication capabilities.

Surface Area-to-Volume Ratio (SA:V)

The physical proportion of external surface area relative to internal volume; a higher value enhances diffusion rate and the efficiency of exchanging nutrients and wastes with the environment.

Phospholipid

The fundamental building block of cell membranes, composed of a hydrophilic phosphate head and two hydrophobic fatty acid tails.

Hydrophilic Head

The water-attracting phosphate group of a membrane phospholipid that lines the outer and inner borders of the lipid bilayer and forms hydrogen bonds with water.

Hydrophobic Tails

The water-repelling fatty acid chains that orient toward the interior of the lipid bilayer and do not form hydrogen bonds with water.

Peripheral Proteins

Membrane proteins located on the exterior surfaces (intracellular or extracellular) of the lipid bilayer.

Integral Proteins

Proteins that span across the entire membrane bilayer, commonly serving as transport channels or carriers.

Cholesterol

A hydrophobic lipid molecule embedded within the plasma membrane that maintains membrane structural stability across temperature variations.

Glycoproteins and Glycolipids

Carbohydrate chains bound to membrane proteins or lipids that function in cellular recognition, identification, and communication.

Fluid Mosaic Model

The model describing the plasma membrane as a dynamic, non-stationary mosaic where phospholipids, proteins, cholesterol, and carbohydrates move fluidly relative to one another.

Passive Transport

The net movement of substances down a concentration gradient from an area of high concentration to an area of low concentration without expending energy.

Simple Diffusion

Passive transport wherein nonpolar molecules ($CO_2$, $O_2$, $N_2$) or small polar molecules ($H_2O$, at slow rates) pass directly across the phospholipid bilayer.

Osmosis

The passive diffusion of water molecules through a semi-permeable membrane facilitated by specialized channel proteins called aquaporins.

Aquaporins

Membrane protein channels that selectively accelerate the diffusion of water across the cell membrane.

Facilitated Diffusion

The passive passage of large polar molecules (such as glucose) or charged ions ($Na^+$, $K^+$, $Cl^-$) across the membrane using specific protein channels.

Active Transport

The transport of substances against their concentration gradient from an area of low concentration to an area of high concentration, powered by energy released from $ATP$ hydrolysis ($ATP \rightarrow ADP + P$).

Vesicular Transport

The bulk transport of materials across the plasma membrane utilizing membrane-bound vesicles, categorized into exocytosis and endocytosis.

Exocytosis

A form of active vesicular transport in which internal vesicles fuse with the plasma membrane to secrete large macromolecules, such as hormones, out of the cell.

Endocytosis

A cellular process where the plasma membrane folds inward around extracellular materials that cannot cross the bilayer to engulf and bring them inside the cell.

Tonicity

The relative concentration of solutes dissolved in solution outside a cell compared to inside the cell, governing the direction and extent of net water movement across the membrane.

Hypertonic Solution

An external environment containing a higher concentration of solutes than the cell interior, causing net water loss and resulting in a shriveled or plasmolyzed cell.

Hypotonic Solution

An external environment containing a lower concentration of solutes than the cell interior, causing net water entry that leads to cell swelling and provides internal turgor pressure in plant cells.

Isotonic Solution

A solution whose solute concentration is equal to that inside the cell, resulting in no net movement of water.

Water Potential

A physical measure representing the likelihood of water to move from an area of higher potential (maximum value of $0$) to an area of lower (more negative) potential, determined by solute potential and pressure potential.

Solute Potential

The component of water potential that reflects the effect of dissolved solutes on water movement; it is always zero or negative, and adding solutes lowers this potential.

Pressure Potential

The component of water potential resulting from a physical push or pressure exerted on water; it is always zero or positive, and increasing physical pressure increases the overall water potential.