chapter 3 vocab

Prokaryotic

Cell type that lacks a membrane-bound nucleus and membrane-bound organelles; bacteria and archaea are prokaryotic organisms.

Eukaryote

Cell type that contains a membrane-bound nucleus and membrane-bound organelles; includes animals, plants, fungi, and protists.

Unicellular

An organism consisting of a single cell.

Multicellular

An organism consisting of many cells that work together.

Hydrophilic

Water-attracting; describes substances or portions of molecules that interact readily with water. The phosphate heads of phospholipids are hydrophilic.

Hydrophobic

Water-repelling; describes substances or portions of molecules that do not interact readily with water. The fatty-acid tails of phospholipids are hydrophobic.

Phospholipid bilayer

A double layer of phospholipids that forms the basic structure of the cytoplasmic membrane, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Selectively permeable

A property of the cytoplasmic membrane that allows some substances to cross more easily than others, controlling what enters and leaves the cell.

Aquaporin

A membrane channel protein that facilitates the movement of water across the cytoplasmic membrane.

Diffusion

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

Active transport

The movement of substances across a membrane against their concentration gradient using cellular energy.

Efflux pumps

Transport proteins that actively pump substances out of a cell; they can contribute to antimicrobial resistance by removing antimicrobial drugs.

Passive transport

The movement of substances across a membrane without the expenditure of cellular energy, generally from higher to lower concentration.

Protein secretion

The process by which a cell transports proteins from inside the cell to the outside of the cell.

Gram negative

Bacteria with a cell wall characterized by a thin layer of peptidoglycan surrounded by an outer membrane; these cells stain pink following Gram staining.

Gram positive

Bacteria with a cell wall characterized by a thick layer of peptidoglycan; these cells stain purple following Gram staining.

Peptidoglycan

A macromolecule that provides strength to the bacterial cell wall; it is found only in bacteria.

Biofilm

A community of microorganisms attached to a surface and surrounded by a self-produced extracellular matrix.

Flagella

Long cellular structures used for cell movement.

Chemotaxis

The movement of a cell toward or away from a certain chemical in the environment.

Pili

Cell-surface structures that allow cells to adhere to certain materials; some types are involved in DNA transfer between cells.

Nucleoid

The region of a prokaryotic cell where the chromosome is located; unlike a nucleus, it is not surrounded by a membrane.

Ribosome

The cellular structure involved in protein synthesis.

Endospore

An extraordinarily resistant dormant cell produced by some types of bacteria that allows survival under unfavorable environmental conditions.

Vesicle

A small membrane-bound compartment used to transport or store substances within eukaryotic cells.

Endocytosis

The process by which a eukaryotic cell takes material into the cell by surrounding it with the cytoplasmic membrane and forming a vesicle.

Exocytosis

The process by which intracellular vesicles fuse with the cytoplasmic membrane and release their contents outside the cell.

Pinocytosis

A type of endocytosis in which a cell takes in extracellular fluid and dissolved substances; sometimes called cell drinking.

Phagocytosis

A type of endocytosis in which a cell engulfs large particles or microorganisms; sometimes called cell eating.

Actin

A protein that forms microfilaments of the cytoskeleton and is involved in maintaining cell shape and cellular movement.

Chloroplast

A membrane-bound organelle found in plants and algae that carries out photosynthesis.

Endoplasmic reticulum

A membrane network in eukaryotic cells involved in the synthesis and transport of proteins and lipids; rough ER contains ribosomes while smooth ER does not.

Golgi apparatus

A eukaryotic organelle that modifies, sorts, and packages proteins and other molecules for transport to their destinations.

Magnification

The apparent increase in the size of an object produced by a microscope.

Resolution

The ability of a microscope to distinguish two nearby objects as separate and distinct.

Mitochondria

Eukaryotic organelles where aerobic cellular respiration occurs and most cellular ATP is produced.

Contrast

The difference in appearance between an object and its background that makes the object easier to see.

Dark-field microscope

A light microscope that produces a bright image of the specimen against a dark background; useful for viewing thin, living, unstained microorganisms.

Phase-contrast microscope

A microscope that increases contrast by converting differences in how light passes through a specimen into differences in brightness; useful for viewing living, unstained cells.

DIC microscope

Differential interference contrast microscope; uses differences in light passing through a specimen to produce a highly detailed image with a three-dimensional appearance.

Fluorescence microscope

A microscope that uses fluorescent substances that absorb light at one wavelength and emit light at a longer wavelength, causing labeled structures to glow against a dark background.

Electron microscope

A microscope that uses a beam of electrons rather than visible light to produce images with much greater resolution than a light microscope.

Simple stain

A staining technique that uses a single dye to color cells, allowing their size, shape, and arrangement to be observed.

Differential stain

A staining technique that uses multiple dyes to distinguish different types of cells or cellular structures based on their staining properties.

Acidic dye

A negatively charged dye whose chromophore is repelled by the negatively charged bacterial cell surface, usually staining the background rather than the cell.

Basic dye

A positively charged dye whose chromophore is attracted to the negatively charged bacterial cell surface, causing the cells themselves to become stained.

Capsule stain

A staining technique used to visualize the capsule surrounding some microorganisms, typically by staining the cell and/or background while leaving the capsule as a clear halo.

Endospore stain

A differential staining technique used to detect and visualize bacterial endospores.