Biology Chapter 4: Cell Structure and Function

These vocabulary flashcards cover the primary concepts of cell biology from Chapter 4, including the differences between prokaryotic and eukaryotic cells, organelle functions, the endomembrane system, and the cytoskeleton.

Cell Theory

A unifying concept in biology stating that all organisms are composed of cells, cells are the basic units of structure and function, and cells come only from preexisting cells.

Matthias Schleiden

A German botanist ($1804$ to $1881$) who contributed to the cell theory by identifying that plants are composed of cells.

Theodor Schwann

A German zoologist ($1810$ to $1882$) who contributed to the cell theory by identifying that animals are composed of cells.

Rudolph Virchow

A German physician ($1821$ to $1902$) who determined that cells are self-reproducing and come only from preexisting cells.

Surface-area-to-volume ratio

A relationship that requires cells to be small; as a cell increases in size, its volume increases faster than surface area, decreasing the efficiency of material transport.

Prokaryotic Cells

Cells that lack a membrane-bound nucleus and are structurally smaller and simpler than eukaryotic cells.

Peptidoglycan

A complex molecule that strengthens the cell wall of bacteria.

Nucleoid

A region in a prokaryotic cell that contains the single, circular DNA molecule.

Plasmids

Small accessory, extrachromosomal rings of DNA found in many prokaryotes.

Conjugation pili

Rigid, tubular structures used by prokaryotes to pass DNA from cell to cell.

Eukaryotic Cells

Cells characterized by the presence of a membrane-bound nucleus and specialized organelles.

Organelles

Small structures within a cell that perform specific functions and isolate chemical reactions.

Endosymbiotic theory

The hypothesis that mitochondria and chloroplasts originated when a large eukaryotic cell engulfed smaller independent prokaryotic cells.

Nucleoplasm

The semifluid medium inside the nucleus that contains chromatin.

Chromatin

A combination of nucleic acids and proteins that condenses to form chromosomes during cell division.

Nucleolus

A dark region within the nucleus where ribosomal RNA ($rRNA$) is produced and ribosome subunits are assembled.

Ribosomes

The site of protein synthesis in the cell, composed of two subunits and made of $rRNA$ and proteins.

Rough Endoplasmic Reticulum

A system of membrane channels continuous with the nucleus, studded with ribosomes, and responsible for protein modification and glycoprotein production.

Smooth Endoplasmic Reticulum

A system of membrane channels lacking ribosomes, involved in lipid synthesis, detoxification (especially in liver cells), and storage.

Golgi apparatus

A stack of flattened, curved saccules that modifies, sorts, and packages proteins and lipids into vesicles for shipment.

Lysosomes

Highly acidic, membrane-bound vesicles produced by the Golgi apparatus that contain hydrolytic enzymes for digesting macromolecules and recycling cell parts.

Peroxisomes

Membrane-bounded vesicles that enclose enzymes that catalyze reactions producing hydrogen peroxide ($H_2O_2$), which is then broken down into water and oxygen by catalase.

Central vacuole

A large, fluid-filled sac in plant cells (taking up to $90$% of volume) that stores water, nutrients, and waste while maintaining turgor pressure.

Chloroplasts

The site of photosynthesis in plants and algae, consisting of a double membrane, stroma, and thylakoids stacked into grana.

Stroma

The semifluid region within a chloroplast that surrounds the thylakoids and contains enzymes for carbohydrate synthesis.

Mitochondria

The powerhouse of the cell, where cellular respiration occurs to produce $ATP$ from the breakdown of carbohydrates.

Cristae

The folds of the inner mitochondrial membrane that increase the surface area for respiratory enzymes.

Cytoskeleton

An internal framework of actin filaments, intermediate filaments, and microtubules that maintains cell shape and assists in movement.

Actin filaments

Extremely thin protein fibers that form a dense web under the plasma membrane and interact with myosin for muscle contraction.

Intermediate filaments

Intermediate-sized, ropelike assemblies of fibrous polypeptides, such as keratin, that provide mechanical strength to cells.

Microtubules

Hollow cylinders made of alpha and beta tubulin dimers that interact with motor molecules like kinesin and dynein for organelle movement.

Centrioles

Short, hollow cylinders composed of a $27$-microtubule ($9 \times 3$) arrangement, located in the centrosome of animal cells.

9 + 2 pattern

The characteristic microtubule arrangement in eukaryotic cilia and flagella, consisting of a cylinder of nine pairs surrounding two central single microtubules.