Cell Structure & Function Study Guide

Comprehensive vocabulary flashcards covering cell organelles, compartmentalization, endosymbiotic theory, surface area-to-volume relationships, cell membrane components, transport mechanisms, tonicity, and water potential principles.

Cell Membrane (Plasma Membrane)

The semi-permeable outer barrier of 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 and shape, protects against mechanical and pathogen damage, and withstands internal turgor pressure to prevent bursting.

Cytoplasm (Cytosol)

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

Cytoskeleton

Protein fibers that move and anchor organelles within the cell and assist in cell division.

Chloroplast

A specialized organelle found in photosynthetic cells featuring a double membrane with inner folds and fluids; it stores the sun's energy as glucose.

Golgi Apparatus

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

Lysosomes

Membrane-bound organelles containing digestive enzymes that break down broken cell parts and are utilized for apoptosis (programmed cell death).

Mitochondria

Specialized double-membrane organelles with areas of inner folds and fluids found in all eukaryotic cells; they break glucose into useable cellular energy ($\text{ATP}$).

Nucleus

An organelle surrounded by a nuclear envelope that stores and protects DNA for the cell.

Ribosomes

Structures that synthesize proteins; those located on the rough endoplasmic reticulum make proteins for export outside the cell, while those in the cytoplasm make proteins for use inside the cell.

Rough Endoplasmic Reticulum (RER)

A membrane-bound organelle studded with ribosomes on its surface that folds and processes proteins to deliver them to the Golgi apparatus.

Smooth Endoplasmic Reticulum (SER)

A membrane-bound organelle without ribosomes that breaks down toxins and synthesizes lipids.

Vacuoles

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

Vesicles

Membrane-bound transport structures utilized in the endomembrane pathway, endocytosis, and exocytosis.

Endomembrane Pathway

The sequential multi-organelle pathway through which a protein is generated on the RER ribosome, folded and packaged into a vesicle, modified and tagged in the Golgi apparatus, and ultimately secreted at the cell membrane via exocytosis.

Cell Compartmentalization

The organization of internal areas by membrane-bound organelles to isolate biochemical reactions and optimize metabolic efficiency.

Endosymbiotic Theory

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

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

A mathematical relationship where a higher ratio indicates greater efficiency at diffusing substances and exchanging materials with the surrounding environment.

Phospholipids

The primary structural lipid of cell membranes, possessing a hydrophilic phosphate head that forms hydrogen bonds with water on outer borders and hydrophobic fatty acid tails pointing inward.

Peripheral Proteins

Proteins attached to the outer intracellular or extracellular surfaces of the cell membrane.

Integral Proteins

Proteins that span across the entire lipid bilayer and are utilized for cellular transport.

Cholesterol

A hydrophobic lipid embedded within the plasma membrane that provides structural stability, particularly during temperature changes.

Glycoproteins and Glycolipids

Carbohydrate-bearing membrane molecules utilized by the cell for cellular identification and communication.

Fluid Mosaic Model

A structural model describing the cell membrane as a non-stationary arrangement of molecules that move around fluidly.

Passive Transport

The movement of substances across a cell membrane from high concentration to low concentration without requiring cellular energy.

Simple Diffusion

A passive process where nonpolar molecules ($\text{CO}_2$, $\text{O}_2$, $\text{N}_2$) and small polar molecules ($\text{H}_2\text{O}$) pass directly through the phospholipid bilayer.

Aquaporins

Specialized membrane protein channels that allow for the rapid passive diffusion of water through the cell membrane during osmosis.

Facilitated Diffusion

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

Active Transport

The movement of molecules against their concentration gradient from low concentration to high concentration, which requires energy provided by $\text{ATP}$ hydrolysis.

ATP Hydrolysis

The chemical reaction in which a phosphate bond in $\text{ATP}$ is split into $\text{ADP} + \text{P}$, releasing energy needed for active transport.

Exocytosis

A vesicular transport process where internal vesicles fuse with the cell membrane to secrete large macromolecules (such as hormones) out of the cell.

Endocytosis

A vesicular transport mechanism where the cell membrane folds inward around extracellular materials that cannot freely cross the membrane.

Hypertonic Solution

A solution with a higher solute concentration than the inside of the cell, causing net water loss from the cell and leading to cell shriveling.

Hypotonic Solution

A solution with a lower solute concentration than the inside of the cell, causing water to enter the cell and leading to cell swelling or plant cell turgor pressure.

Isotonic Solution

A solution having an equal solute concentration compared to the inside of the cell, resulting in no net movement of water.

Water Potential

The likelihood of water to move from an area of few solutes (high water potential; maximum of $0$) to an area of many solutes (low, negative water potential), defined by solute potential and pressure potential.

Solute Potential

A component of water potential that measures the effect of dissolved substances on water; it is always $0$ or negative, and adding solutes lowers it further.

Pressure Potential

A component of water potential that measures the physical push on water; it is always $0$ or positive, and adding physical pressure increases the water potential.