Cells

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cells
microscopic structure containing nuclear and cytoplasmic material enclosed by a semipermeable membrane and, in plants, a cell wall; the basic structural unit of all organisms.
cell theory
a basic tenet of modern biology, first stated by Matthias Schleiden and Theodor Schwann in 1838-39, that cells are the basic units of structure and function in living organisms.
plasma membrane
mebrane composed of phospholipids, cholesterol, and proteins, that encloses the cel contents
cytoplasm
the cell substance between the cell membrane and the nucleus, containing the cytosol, organelles, cytoskeleton, and various particles.
organelle
a specialized part of a cell having some specific function; a cell organ.
nucleus
a specialized, usually spherical mass of protoplasm encased in a double membrane, and found in most living eukaryotic cells, directing their growth, metabolism, and reproduction, and functioning in the transmission of genic characters.
intracellular fluid
fluid within the cell
extracellular fluid
internal fluid located outside of cells
fluid moisac model
depiction of the structure of the membranes of a cell as phospholipid bilayers in which proteins are dispersed
lipid bilayer
a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends facing outward.
phospholipid
any of a group of fatty compounds, as lecithin, composed of phosphoric esters, and occurring in living cells.
hydrophilic
having a strong affinity for water.
hydrophobic
refers to molecules, or parts of molecules, that interact only with nonpolar molecules
glycolipid
lipid with one or more covalently attached sugars
cholesterol
steroid found in animal fats as well as in most body tissues
cytoskeleton
elaborate series of rods running through cytosol, supporting cellular structures and providing the machinery to generate various cell movements
integral proteins
type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins are IMPs, but not all IMPs are transmembrane proteins.
transmembrane proteins
ype of membrane protein spanning the entirety of the biological membrane to which it is permanently attached. That is, transmembrane proteins span from one side of a membrane through to the other side of the membrane.
protein channels
assist in transporting material across the cell membrane.
protein carriers
facilitate diffusion of molecules across the cell membrane. The protein is imbedded in the cell membrane and covers the entire membrane. This is important because the carrier must transport the molecule in and out of the cell.
peripheral proteins
proteins that adhere only temporarily to the biological membrane with which they are associated. These molecules attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer.
lipid rafts
Sphingolipid and cholesterol-rich domains may exist as phase-separated "rafts" in the membrane. We discuss the relationship between detergent-resistant membranes, rafts, caveolae, and low-density plasma membrane fragments. We also discuss possible functions of lipid rafts in membranes.
glycocalyx
layer of externally facing glyco-proteins on a cell's plasma membrane
tight junctions
area wher eplasma membranes of adjacent cells are tightly bound together
desmosomes
cell junction composed of thickened plasma membranes joined by filaments
gap juctions
a passageway between two adjacent cells formed by transmembrane roteins called connexons
interstitial fluid
is a solution that bathes and surrounds the cells of multicellular animals. It is the main component of the extracellular fluid, which also includes plasma and transcellular fluid. The interstitial fluid is found in the interstitial spaces, also known as the tissue spaces.
differentially permeable
a membrane that prevents the passage of some substances but allows the passage of others based on differences in the size, charge, or lipid-solubility of the substances.
passive process
membrane transport process that do not require cellular energy
active process
membrane transport process that does require cellular energy
diffusion
spreading of particles in a gas or siolution with a movement toward uniform distribution of particles.
concentration gradient
difference in the concentration of a particular substance between two different areas
simple diffusion
unassisted transport across a plasma membrane of a lipid soluble or very smal particle
facilitated diffusion
passive transport process used by certain large or charged molecules that are unabke to pass throught he plasma membrane unaided
osmosis
the tendency of a fluid, usually water, to pass through a semipermeable membrane into a solution where the solvent concentration is higher, thus equalizing the concentrations of materials on either side of the membrane; the diffusion of fluids through membranes or porous partitions.
aquaporins
any of a family of proteins found in plasma membranes and forming a functional component of water channels.
tonicity
measure of the ability to of a solution to cause a change in cell shape or tone by promoting osmotic flows of water
isotonic solution
solution with a concentration of nonpenetrating solutes equal to that found in the reference cell
hypertonic solution
solution that has a higher concentration of nonpenetrating solutes than the reference cell
hypotonic solution
solution that is more dilute than the reference cell
active transport
membrane transport process for which ATP is required
secondary active transport
the movement of all types of molecules across a cell membrane against its concentration gradient (from low to high concentration). In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids. If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is termed primary active transport. Secondary active transport involves the use of an electrochemical gradient. Active transport uses cellular energy, unlike passive transport, which does not use cellular energy. Active transport is a good example of a process for which cells require energy. Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.
vesicular transport
transport of large particles and macromolecules into ot out of the cell or betwen compartments in membrane bound sacs
endoytosis
means by which fairly large extracellular molecules or particles enter cells
exocytosis
mechanism by which substances are moved from the cell interior to the extracellular space as a secretory vesicle fuses with the plasma membrane
phagocytosis
engulfing of foreign solids by cells
amoeboid motion
the flowing movement of the cytoplasm of a phagocyte
secretory vesicle
vesicles that migrate to the plasma membrane of a cell and discharge their contents from the cell by exocytosis
resting membrane potential
voltage that exists across the plasma membrane during the resting state of an excitable cell
polarized
state of a plasma membrane of an unstimulated neuron or muscle cell in which the inside of the cell is reltively negative in comparison to the outside
ligands
signaling chemicals that bind specifically to mebrane receptors
cytosol
viscous semitransperant fluid sunstance of cytoplasm by swhich other elements are suspended
inclusions
the act of enclosing or the condition of being enclosed.
Anything that is enclosed; a cell inclusion.
mitochondria
cytoplasmic organelles responsible for ATP geeration for cellular activities
ribosomes
cytoplsmic organelles at which proteins ar synthesized
rough endoplasmic reticulum
a network of tubular membranes within the cytoplasm of the cell, studded with ribosomes, involved in the transport of materials.
smooth endoplasmic reticulum
a network of tubular membranes within the cytoplasm of the cell, with a smooth surface, involved in the transport of materials.
golgi apparatus
membraneous system close to the cell nucleus that packages protein secretions for export
peroxisomes
...
lysosomes
organelles that originate from the golgi apparatus and contain strong digestive enzymes
endomembrane system
...
cytoskeleton
elaborate series of rods running through cytosol, supporting cellular structures and providing the machinery to generate various cell movements
microfilaments
thin strands of contractile protein actin
microtubules
one of the three types of rods in cytoskeleton of a cell; hollow tubes made of spherical protein that determine the shape of the cell
centrosome
region near the nuleus which contains paired organelles called centrioles
centrioles
minute body found near the nucleus of the cell
cilia
tiny hairlike projections on the cell surfaces thathelp them move
flagella
long whiplike tales containing microtubules
microvilli
tiny projections on the free surfaces of some epithelial cells
multinucleate
has more than one nucleus
anucleate
has no nucleus
muclear envelope
double membrane barrier of a cell nucleus
nuclear pores
An octagonal opening where the inner and outer membranes of the nuclear envelope are continuous
nucleolus
dense spherical body in a cell nucleus involved with ribosomal RNA synthesis and ribosomal subunit assembly
chromatin
structures in the nucleus that carry the hereditary factors
DNA
nucleic acid found in all living cells
histone protein
a simple protein, soluble in water and insoluble in dilute ammonia, found combined as salts with acidic substances, e.g., the protein combined with nucleic acid or the globin of hemoglobin.
chromosome
barlike bodies of tightly coiled chromatin
cell cycle
series of changes a cell goes through from the time it s produced til the time it reproduces itself
mitosis
the usual method of cell division, characterized typically by the resolving of the chromatin of the nucleus into a threadlike form, which condenses into chromosomes, each of which separates longitudinally into two parts, one part of each chromosome being retained in each of two new cells resulting from the original cell.
gene
the basic physical unit of heredity; a linear sequence of nucleotides along a segment of DNA that provides the coded instructions for synthesis of RNA, which, when translated into protein, leads to the expression of hereditary character.
mRNA
messenger RNA.
tRNA
transfer RNA.
rRNA
ribosomal RNA.
body fluids
any of various types of fluid found in the body of a human or animal, as blood or urine.
cellular secretions
the discharge from a cell of particles that are too large to diffuse through the wall; the opposite of endocytosis. The aggregation of migrating leukocytes in the epidermis as part of the inflammatory response
extracellular matrix
nonliving material in connective consisting of ground substance and fibers that separates iving cells
apoptosis
process of controlled cellular suicide