Cell Structure and Function Flashcards

Comprehensive vocabulary flashcards covering bacterial and eukaryotic cell structure, glycocalyces, flagella, cell wall composition, membrane transport mechanisms, and internal structures like endospores and inclusions.

Friedrich Wöhler

Scientist who disproved the belief that organic chemicals could only originate from living organisms.

Schwann & Schleiden

Scientists who formulated the theory that all living organisms are composed of cells.

Metabolism

The process by which organisms take in nutrients from their environment and utilize them to produce the energy (stored in ATP) required for growth, reproduction, and responsiveness.

Responsiveness

The ability of living organisms to modify themselves in reaction to changing external or internal conditions.

Growth

An increase in the physical size of living cells or organisms.

Reproduction

An increase in the total number of organisms or cells.

Taxa

The biological classification groups used to categorize organisms, such as Domain Archaea and Domain Bacteria.

Prokaryotes

Microorganisms that lack a nuclear membrane surrounding their genetic material and are capable of reading DNA genetic code while simultaneously synthesizing proteins (typically around $1.0\,\mu m$ in size).

Eukaryotes

Organisms composed of cells containing a nuclear envelope that surrounds their DNA to form a true nucleus, along with membrane-bound organelles (typically $10\text{--}100\,\mu m$ in size).

Glycocalyx

A sticky, gelatinous substance composed of polysaccharides, polypeptides, or both, which surrounds the outer exterior of a bacterial cell.

Capsule

A glycocalyx constructed from organized, repeating units of organic chemicals that are firmly attached to the surface of a cell.

Slime Layer

A loose, water-soluble type of glycocalyx that aids bacteria in attaching to surfaces and forming biofilms.

Biofilm

A complex community of numerous microorganisms adhering to a surface (such as dental plaque), protecting resident bacteria from antibiotics and host defenses.

Flagella

Long, threadlike structures extending past the cell surface and glycocalyx that rotate to enable cell motility.

Flagellin

Globular protein molecules arranged in a helical pattern to construct the filament portion of a bacterial flagellum.

Flagellar Basal Body

The component made of a rod and protein rings that anchors the flagellar filament to the cell wall and cytoplasmic membrane.

Serovars

Strains of a bacterial species classified based on antigenic differences in their flagellar proteins.

Peritrichous

A flagellar arrangement in which flagella cover the entire outer surface of the bacterial cell.

Spirochetes

Spiral-shaped bacteria that possess endoflagella at both ends forming an axial filament, allowing them to move in a corkscrew motion.

Endoflagella

Flagella located between the cytoplasmic membrane and outer membrane of spirochetes that form an axial filament wrapped around the cell body.

Monotrichous

Refers to a bacterial cell that possesses a single flagellum located at one end.

Amphitrichous

Refers to a bacterial cell with flagella positioned at both opposite ends of the cell.

Lophotrichous

Refers to a bacterial cell that has a tuft or cluster of flagella attached at one end.

Taxis

Cellular movement occurring directly in response to an environmental stimulus (positive towards, negative away).

Phototaxis

Cellular movement in response to a light stimulus.

Chemotaxis

Cellular movement in response to a chemical stimulus.

Fimbriae

Proteinaceous, rod-like extensions that are shorter than flagella and allow bacteria to adhere to surfaces, host tissue, or other cells.

Conjugation Pilus

A hollow protein tube longer than fimbriae but shorter than flagella, used by bacteria to transfer DNA from one cell to another during conjugation.

Cocci and Bacilli

Common bacterial shapes representing spherical cells (cocci) and rod-shaped cells (bacilli).

Peptidoglycan

A complex mesh carbohydrate lattice in bacterial cell walls constructed from alternating NAG and NAM chains linked by tetrapeptide bridges.

Gram-Positive Cell Wall

A bacterial cell wall featuring a thick outer layer of peptidoglycan containing teichoic acids and lipoteichoic acids.

Teichoic Acids

Negatively charged unique chemical compounds present in Gram-positive cell walls that assist in regulating ion passage.

Lipoteichoic Acids

Teichoic acids covalently bound to membrane lipids, anchoring peptidoglycan to the cytoplasmic membrane in Gram-positive cells.

Gram-Negative Cell Wall

A cell wall characterized by a thin layer of peptidoglycan surrounded by an outer membrane containing phospholipids, proteins, and lipopolysaccharides (LPS).

Porins

Protein channels spanning both leaflets of the Gram-negative outer membrane, allowing small molecules like glucose to cross freely.

Lipid A

The toxic lipid component of lipopolysaccharide (LPS) released when Gram-negative bacterial outer membranes break down, inducing fever, inflammation, shock, and blood clotting.

Periplasmic Space

The fluid-filled space located between the cytoplasmic membrane and outer membrane of Gram-negative bacteria.

Fluid Mosaic Model

A structural model of the cytoplasmic membrane describing membrane proteins arranged like tiles in a mosaic that can move laterally within a fluid phospholipid bilayer.

Selective Permeability

The property of a cell membrane that dictates which chemical substances can pass into or out of the cell.

Passive Transport

The movement of chemical substances across a cell membrane along an electrochemical gradient without consuming ATP.

Active Transport

The process requiring cellular ATP and carrier proteins to move substances across a membrane against their electrochemical gradient.

Diffusion

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

Osmosis

The diffusion of water across a semipermeable membrane toward a region with a higher solute (lower water) concentration.

Isotonic Solution

A solution that has an equal solute concentration compared to the interior of a cell, resulting in no net gain or loss of water.

Hypertonic Solution

A solution containing a higher concentration of solutes relative to another solution, causing cells without walls to lose water and shrink.

Hypotonic Solution

A solution containing a lower concentration of solutes relative to another solution, causing cells to absorb water and expand.

Osmotic Effects on Cells

The physical responses of cells placed in hypertonic or hypotonic solutions as water crosses the membrane to balance solute concentrations.

Uniport

A carrier protein (permease) that transports only one specific substance across a cell membrane at a time.

Antiport

A carrier protein that simultaneously transports two different substances across a cell membrane in opposite directions.

Symport

A carrier protein that transports two different substances across a cell membrane simultaneously in the same direction.

Group Translocation

An active transport process unique to certain prokaryotes in which a substance is chemically modified while being transported across the membrane.

Cytosol

The liquid portion of the cytoplasm, consisting mainly of water along with dissolved ions, carbohydrates, proteins, lipids, and waste products.

Inclusions

Deposits of reserve nutrients or compounds (such as lipids, starch, or gas vesicles) stored within the bacterial cytosol.

Endospores

Extremely durable, dormant, non-reproductive structures produced by bacteria such as Bacillus and Clostridium to withstand harsh conditions and protect genetic material.

Sporulation

An $8\text{--}10\text{ hour}$ process in which a vegetative bacterial cell forms an endospore to shield its DNA when nutrients are depleted.

Svedbergs ($S$)

Units used to express ribosome size based on the rate at which particles sediment during centrifugation.

70S Ribosomes

The size classification of prokaryotic ribosomes, which are composed of a $30S$ subunit and a $50S$ subunit.

Cytoskeleton

An internal framework of protein fibers within bacterial cells that plays roles in cell division, shape determination, and segregation of DNA molecules.