chapter 3- cells and methods to observe them

capsule

a distinct, thick gelatinous material that surrounds some microorganisms

chemotaxis

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

cytoplasmic membrane

a phospholipid bilayer embedded with proteins that surrounds the cytoplasm and defines the boundary of the cell

endospore

an extraordinarily resistant dormant cell produced by some types of bacteria

flagellum

a type of structure used for cell movement

gram-negative

bacteria that have a cell wall characterized by a thin layer of peptidoglycan surrounded by an outer membrane; when Gram stained, these cells are pink

gram-positive

bacteria that have a cell wall characteried by a thick layer of peptidoglycan; when Gram stained, these cells are purple

lipopolysaccharide / LPS

molecule that makes up the outer layer of the outer membrane of Gram-negative bacteria

peptidoglycan

a macromolecule that provides strnegth to the cell wall; it is found only in bacteria

periplasm

the gel-like material that fills the region between the cytoplasmic membrane and the outer membrane of Gram-negative bacteria

pili

cell surface structure that allow cells to adhere to certain material; some types are involved in a mechanism of DNA transfer

plasmid

extrachromosomal DNA molecule that replicated independently of the chromosome

ribosome

structure involved in protein synthesis

transport systems

mechanisms cells use to transport nutrients and other small molecules across the cytoplasmic membrane

cell envelope

the layers surrounding the contents of the cell; they include the cytoplasmic membrane, cell wall, and capsule (if present)

cytoplasm

contents of a cell, excluding the nucleus

nucleoid

region of a prokaryotic cell containing the DNA

selectively permeable

describing material that allows only certain molecules to pass through freely

aquaporins

pore-forming membrane proteins that specifically allow water to pass through

simple diffusion

movement of solutes from a region of high concentration to one of low concentration; does not involve transport proteins

osmosis

movement of water acorss a membrane from a dilute solution to a more concentrated solution

electron transport chain (ETC)

group of membrane-embedded electron carriers that pass electrons from one to another, and in the process, create a proton motive force

proton motive force

form of energy generated as an electron transport chain moves protons across a membrane to create a chemiosmotic gradient

facilitated diffusion

transport process that moves compounds across a membrane down a concentration gradient; does not require energy

active transport

energy-consuming process by which cells move molecules across a membrane and against a concentration gradient

group translocation

type of transport process that chemically alters a molecule during its passage through the cytoplasmic membrane

secretion

releasing a substance from a cell or tissue

signal sequence

amino acid sequence that directs cellular machinery to secret a polypeptide

teichoic acids

gram-positive cell wallcomponent, composed of chains of a common subunit to which various sugars and D-alanine are usually attached

outer membrane

(in prokaryotic) the unique lipid bilayer of gram-negative cells that surrounds the peptidoglycan layer

(in eukaryotic) the membrane on the cytoplasmic side of organelles that have double membranes

porins

proteins in the outer membrane of gram-negative bacteria that form channels through which small molecules can pass

lysozyme

enzymes that degrades the peptidoglycan layer of the bacterial cell wall

slime layer

a diffuse and irregular material that surrounds some microorganisms

glycocalyx

polysaccharide layer that surrounds some cells and generally functions as a mechanism of either protection of attachment

filament, hook, basal body

the three parts of a flagellum

prokaryotic chromosome

a single, circular double-stranded DNA molecule that contains all the genetic information required by a cell

cytoskeleton

the dynamic filamentous network that provides structure and shape to cells

storage granule

an accumulation of a high-molecular-weight polymer synthesized from a nutrient that a cell has in relative excess

gas vesicles

small, rigid compartments produces by some aquatic bacteria that provide buoyancy to the cell

bacterial microcompartment (BMC)

protein-based structure in some bacteria that contains enzymes required for certain reactions

encapsulin nanocompartment

protein-based compartment in bacteria and archaea that holds certain proteins

sporulation

the process of producing a spore

germinate

exit the dormant stage; used to describe the behavior of an endospore or other resting cell

receptor

type of protein that binds to specific molecules in the environment, providing a mechanism for the cell to sense and adjust to its surroundings

ligand

a molecule that specifically binds to a given receptor

channel

pore-forming membrane protein that allows specific ions to diffuse into and out of a cell

carrier

type of protein found in cell membranes that transports certain compounds across the membrane

endocytosis

process through which cells take up particles by enclosing them in a vesicle pinched off from the cell membrane

pinocytosis

process by which eukaryotic cells take in liquid and small particles from the surrounding environment by internalizing and pinching off small pieces of their own membrane, bringing along a small volume of liquid and any material attached to the membrane

phagocytosis

the process by which a phagocyte engulfs microbial invaders and debris

exocytosis

process by which eukaryotic cells expel material; membrane-bound vesicles inside the cell fuse with the plasma membrane, releasing their contents to the external medium

actin filaments

cytoskeletal structures of eukaryotic cells that allow movement within the cell

microtubles

cytoskeleton structure of a eukaryotic cell that form mitotic spindles, cilia, and flagella; hollow cylinders composed of tubulin

intermediate filament

component of the eukaryotic cytoskeleton; functions like a rope, strengthening the cell mechanically

mitochondria

organelle in eukaryotic cells in which the majority of ATP synthesis occurs

chloroplast

organelles in photosynthetic eukaryotic cells that harvest the energy of sunlight and use it to synthesize ATP, which is then used to fuel the synthesis of organic compounds

endoplasmic reticulum (ER)

organelle of eukaryotes where macromolecules destined for the external environment of other organelles are synthesized; complex system of flattened sheet, sacs, and tubes

golgi apparatus

series of membrane-bound flattened sacs within eukaryotic cells that serve as the site where macromolecules synthesized in the endoplasmic reticulum are modified before they are transported to other destinations

lysosome

membrane-boound structure in eukaryotic cells that contains powerful degratative enzymes

peroxisome

organelle that uses hydrogen perozide and superoxide to degrade substances

contrast

the number of different visible shaded in a specimen

wet mount

method of observing living organisms in a drop of liquid using a microscope