Cellular Biology: Prokaryotic and Eukaryotic Cell Structures

Vocabulary flashcards covering cellular structures, organelle functions, and fundamental differences between prokaryotic and eukaryotic cells based on the lecture text.

Prokaryote

A single-celled microscopic organism (such as bacteria) that lacks a true nucleus or membrane-bound organelles, with its genetic material located directly in the cytoplasm; derived from Greek pro (before) and -karyon (kernel).

Eukaryote

An organism whose cells contain a distinct nucleus containing DNA protected by a membrane, as well as other specialized membrane-bound organelles; derived from Greek eu- (true) and -karyon (kernel).

Endomembrane System

An interconnected system of membranes found in eukaryotic cells—including the endoplasmic reticulum and Golgi apparatus—that aids in modifying and transporting cellular materials.

Cell Membrane

A thin, flexible phospholipid bilayer with embedded proteins that surrounds every living cell, creating a barrier that regulates the movement of substances in and out of the cell to maintain a stable internal environment.

Cell Wall

A rigid layer surrounding the cell membrane in plants (cellulose), fungi (chitin), bacteria (peptidoglycan), and some protists that provides structural support and protection; absent in animal cells.

Chromatin

The form of genetic material inside the eukaryotic nucleus consisting of DNA combined with proteins.

Nucleolus

A specialized structure inside the eukaryotic nucleus that plays a key role in ribosome production.

Nucleoplasm

The gel-like fluid substance that fills the inside of the nucleus.

Nuclear Envelope

A double membrane system surrounding the eukaryotic nucleus that is connected to the endoplasmic reticulum.

Nuclear Pores

Structures in the nuclear envelope that function as regulated gateways controlling the transport of molecules between the nucleus and cytoplasm.

Endoplasmic Reticulum (ER)

A eukaryotic organelle composed of a network of interconnected tube-shaped membranous structures called ER cisternae.

Smooth Endoplasmic Reticulum (SER)

A region of the ER involved in metabolic processes, detoxification of harmful substances, production of lipids and steroids (such as cholesterol), and storage of molecules.

Rough Endoplasmic Reticulum (RER)

A region of the ER studded with ribosomes on its surface that modifies and folds proteins made by those ribosomes before vesicle transport.

Ribosomes

Cellular organelles found in both eukaryotic and prokaryotic cells, often referred to as the protein factories of the cell, that assemble amino acids into polypeptides.

Golgi Complex

An organelle consisting of an unconnected network of membranous sacs called cisternae that receives, sequentially modifies, sorts, and packages molecules into vesicles for transport.

Vesicles

Membranous sacs that transport materials within cells and participate in cellular processes such as endocytosis and secretion.

Lysosomes

Membranous sacs containing acidic hydrolytic enzymes that break down complex molecules into simpler ones and degrade damaged organelles through autophagy.

Central Vacuole

A large membrane-bound organelle in plant cells containing cell sap that stores water and inorganic substances, performs enzymatic hydrolysis, and aids in plant cell swelling and growth.

Contractile Vacuole

A specialized organelle found in aquatic single-celled organisms like Paramecium that pumps excess water out of the cell.

Mitochondria

Organelles in eukaryotic cells that carry out cellular respiration, converting oxygen and sugar into usable energy in the form of $ATP$ (adenosine triphosphate).

Chloroplast

An organelle found in plants and some algae that contains the green pigment chlorophyll and performs photosynthesis by converting carbon dioxide and water into carbohydrates using sunlight.

Stroma

The fluid inside a chloroplast surrounding thylakoids that contains autonomous DNA, ribosomes, enzymes, and starch granules.

Thylakoids

Interconnected membrane-bound structures inside chloroplasts that are stacked into flattened sacs called grana.

Granum

A stack of interconnected thylakoids within a chloroplast.

Peroxisomes

Organelles containing metabolic enzymes involved in breaking down fatty acids, forming hydrogen peroxide ($H_2O_2$), and detoxifying molecules in organs like the liver and kidneys.

Catalase

An enzyme inside peroxisomes that converts harmful excess hydrogen peroxide ($H_2O_2$) into water ($H_2O$) and oxygen ($O_2$).

Cytoskeleton

A dynamic network of protein filaments in cells that provides structural support, shapes the cell, facilitates intracellular transport, and aids in cell movement.

Microfilaments

Cytoskeletal elements composed of the protein actin.

Intermediate Filaments

Cytoskeletal structures made of fibrous proteins coiled into cables.

Microtubules

Cytoskeletal structures composed of the protein tubulin.

Centriole

An organelle consisting of nine circular microtubule triplets that plays a role in forming cilia, flagella, and spindle fibers; absent in prokaryotes, fungi, and plant cells.

Centrosome

A region near the nucleus where cytoskeletal microtubules arise, containing a pair of perpendicular centrioles in animal cells that produce spindle fibers during cell division.

Pili

Hair-like structures made of pilin protein on the surface of some bacteria; short pili attach to surfaces, while long pili participate in conjugation.

Plasmid

A small, circular DNA molecule in prokaryotes that replicates independently of chromosomal DNA and often carries beneficial survival genes, such as antibiotic resistance.

Nucleoid

The region in a prokaryotic cell's cytoplasm where its single, circular DNA molecule is located without being enclosed by a membrane.