Cell Structure and Function

Comprehensive vocabulary flashcards covering cell theory, cell types, organelle structure and function, cell membrane composition, cytoskeleton elements, and membrane transport mechanisms.

Cell

The smallest living unit of structure and function of all organisms.

Robert Hooke

Mid-1600s scientist who observed a sliver of cork, saw a "row of empty boxes," and coined the term cell.

Theodor Schwann & Matthias Schleiden

Scientists who proposed in 1839 that "all living things are made of cells."

Rudolf Virchow

Scientist who stated 50 years after Schwann and Schleiden that "all cells come from cells."

Cell Theory

Principles stating that all living things are made of cells, the cell is the smallest living unit of structure and function, and all cells arise from preexisting cells.

Surface Area-to-Volume Ratio

The ratio of total surface area to total volume in a cell; smaller cells have a larger ratio (e.g., $6:1$ for eight $1\,\text{cm}$ cubes compared to $3:1$ for one $2\,\text{cm}$ cube).

Protoplasm

Cell contents contained within a thick fluid.

Organelles

Structures within a cell specialized for carrying out specific cell functions.

Prokaryotic Cells

The first cell type on Earth (Bacteria and Archaea) characterized by lacking a membrane-bound nucleus and membrane-bound organelles.

Nucleoid

The region of DNA concentration inside a prokaryotic cell.

Eukaryotic Cells

Cells containing a membrane-bound nucleus and organelles, including fungi, protists, plant, and animal cells.

Endosymbiotic Theory

Theory explaining the evolution of modern eukaryotic cells from ancient cells and symbiotic bacteria.

Plasma Membrane

A double layer of phospholipids and embedded proteins that contains cell contents and regulates what passes in and out of the cell.

Phospholipid

A membrane lipid consisting of a hydrophilic (polar) head made of phosphoric acid and glycerol, and a hydrophobic tail composed of fatty acid chains.

Fluid Mosaic Model

Model describing the fluid nature of a cell membrane composed of a lipid bilayer with embedded proteins.

Glycoproteins

Membrane proteins attached to carbohydrate chains that function to identify the cell type.

Cell Wall

Outer layer surrounding the plasma membrane that provides protection and support, composed of cellulose in plants, chitin in fungi, and protein-polysaccharide in bacteria.

Cytoplasm

Viscous fluid within the cell containing cytosol, interconnected filaments and fibers, storage substances, and organelles (excluding the nucleus).

Cytosol

The fluid portion of the cytoplasm.

Cytoskeleton

Network of protein filaments, fibers, and tubules that provides mechanical support, anchors organelles, and helps move substances within the cell.

Microfilaments

Cytoskeletal fibers measuring $8\,\text{nm}$ in diameter (such as actin) that aid in structural support and cell movement.

Microtubules

Tubular protein structures measuring $25\,\text{nm}$ in diameter made of protein subunits, forming part of the cytoskeleton, cilia, flagella, and centrioles.

Intermediate Filaments

Cytoskeletal fibers measuring $10\,\text{nm}$ in diameter composed of threadlike units that provide mechanical support.

Cilia

Short cellular extensions containing a $9 + 2$ arrangement of microtubule pairs used to move fluids over cell surfaces.

Flagella

Whip-like cellular extensions with a $9 + 2$ arrangement of microtubule pairs that provide cell motility, such as in sperm cells.

Centrioles

Pairs of microtubular structures present in animal cells that play a role in cell division.

Nucleus

Spherical control center of the eukaryotic cell bounded by a double membrane that contains chromosomes and the nucleolus.

Nuclear Envelope

A double membrane containing nuclear pores (aqueous channels) that separates the nucleus from the cytoplasm.

Chromatin

The uncoiled form of DNA packaged with proteins found in the nucleus when the cell is not dividing.

Nucleolus

Structure within the nucleus that directs RNA synthesis and forms/assembles ribosomes.

Endoplasmic Reticulum (ER)

Network of internal membranes that forms compartments and vesicles, modifies and transports proteins, and synthesizes carbohydrates and lipids.

Rough Endoplasmic Reticulum

Membrane network studded with ribosomes on its surface involved in manufacturing and modifying proteins.

Smooth Endoplasmic Reticulum

Membrane network lacking ribosomes that contains enzymes involved in building carbohydrates and lipids.

Golgi Apparatus

Stacks of flattened membrane vesicles that function as the packaging and shipping station of the cell and participate in plant cell wall synthesis.

Lysosomes

Membranous sacs containing digestive enzymes found in animal cells that aid in cell renewal, break down old cell parts, and digest invaders.

Vacuoles

Membrane-bound storage sacs for water, food, and wastes; mature plant cells typically possess a single large vacuole.

Mitochondria

Double-membrane organelles containing their own DNA that break down fuel molecules (glucose, fatty acids) during cellular respiration to release energy as $\text{ATP}$.

Chloroplasts

Solar energy-capturing organelles derived from photosynthetic bacteria, found in plants and algae, that contain chlorophyll and carry out photosynthesis to produce glucose.

Thylakoid

Chlorophyll-containing membrane sac inside a chloroplast.

Granum

A stack of thylakoid membrane sacs inside a chloroplast.

Stroma

The fluid space surrounding the grana within a chloroplast.

Passive Transport

Movement of molecules across a cell membrane down a concentration, pressure, or charge gradient without requiring energy input.

Diffusion

The passive movement of molecules from an area of higher concentration to an area of lower concentration to equalize concentration.

Osmosis

A special form of diffusion involving the movement of water across a membrane from a lower solute concentration to a higher solute concentration.

Hypotonic Solution

A solution with a lower solute concentration outside the cell than inside, causing net water movement into the cell, making it swollen or lysed.

Hypertonic Solution

A solution with a higher solute concentration outside the cell than inside, causing net water movement out of the cell, leaving it crenated.

Isotonic Solution

A solution in which solute concentration outside the cell equals solute concentration inside the cell, resulting in no net water movement.

Facilitated Diffusion

Passive transport of molecules across a membrane through specific carrier or channel proteins (such as aquaporins) without using cellular energy.

Active Transport

The movement of molecules across a membrane against a concentration gradient, requiring cellular energy in the form of $\text{ATP}$.

Sodium-Potassium Pump

An active transport mechanism that uses $\text{ATP}$ to pump sodium ions ($\text{Na}^+$) out of the cell and potassium ions ($\text{K}^+$) into the cell.

Endocytosis

The process by which a cell takes in large material, particles, or organisms by surrounding them with the plasma membrane and pinching off to form a vesicle.

Phagocytosis

A form of endocytosis commonly referred to as 'cell eating,' in which a cell engulfs solid particles or organisms into a vesicle.

Pinocytosis

A form of endocytosis commonly referred to as 'cell drinking,' in which a cell takes in fluid and dissolved large molecules into a vesicle.

Exocytosis

The process by which a cell discharges or expels material by fusing a secretory vesicle with the plasma membrane.