Chapter 3: The Cellular Level of Organization Flashcards
plasma membrane (plasmalemma)
Protects cellular contents; makes contact with other cells; contains channels, transporters, receptors, enzymes, cell-identity markers, and linker proteins; mediates entry and exit of substances.
cytoplasm
Site of all intracellular activities except those occurring in the nucleus.
cytosol
Fluid in which many of cell’s metabolic reactions occur.
nucleus
Nuclear pores control the movement of substances between the nucleus and cytoplasm, nucleoli produce ribosomes, and chromosomes consist of genes that control cellular structure and direct cellular functions.
chromosome
One of the small, threadlike structures in the nucleus of a cell, normally 46 in a human diploid cell, that bears the genetic material; composed of DNA and proteins (histones) that form a delicate chromatin thread during interphase; becomes packaged into compact rodlike structures that are visible under the light microscope during cell division.
genes
Biological unit of heredity; a segment of DNA located in a definite position on a particular chromosome; a sequence of DNA that codes for a particular mRNA, rRNA, or tRNA.
lipid bilayer
two back-to-back layers
made up of three types of lipid molecules—phospholipids, cholesterol, and glycolipids. About 75% of the membrane lipids are phospholipids, Present in smaller amounts are cholesterol (about 20%), and various glycolipids (about 5%).
phospholipids
lipids that contain phosphorus
cholesterol
a steroid with an attached —OH (hydroxyl) group
glycolipids
lipids with attached carbohydrate groups
amphipathic molecules
having both polar and non polar parts
integral proteins
extend into or through the lipid bilayer and are firmly embedded in it. Most integral proteins are transmembrane proteins, which means that they span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid
peripheral proteins
are not as firmly embedded in the membrane. They are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane
glycoproteins
proteins with carbohydrate groups attached to the ends that protrude into the extracellular fluid.
glycocalyx
an extensive sugary coat
ion channels
pores or holes that specific ions, such as potassium ions (K+), can flow through to get into or out of the cell. Most ion channels are selective: they allow only a single type of ion to pass through
carriers
selectively moving a polar substance or ion from one side of the membrane to the other.
receptors
A specialized cell or a distal portion of a neuron that responds to a specific sensory modality, such as touch, pressure, cold, light, or sound, and converts it to an electrical signal (generator or receptor potential). A specific molecule or cluster of molecules that recognizes and binds a particular ligand
ligand
A chemical substance that binds to a specific receptor
enzymes
A chemical substance that accelerates chemical reactions; an organic catalyst, usually a protein
linkers
anchor proteins in the plasma membranes of neighboring cells to one another or to protein filaments inside and outside the cell.
cell-identity markers
They may enable a cell to (1) recognize other cells of the same kind during tissue formation or (2) recognize and respond to potentially dangerous foreign cells
selective permeability
The property of a membrane by which it permits the passage of certain substances but restricts the passage of others
concentration gradient
a difference in the concentration of a chemical from one place to another, such as from the inside to the outside of the plasma membrane.
electrical gradient
A difference in electrical charges between two regions
electrochemical gradient
The combined influence of the concentration gradient and the electrical gradient on movement of a particular ion
hydrophobic
water hating
hydrophillic
water loving
mitochondria
Site of aerobic cellular respiration reactions that produce most of a cell’s ATP. Plays an important early role in apoptosis
mitosis
Nuclear division; distribution of two sets of chromosomes into separate nuclei.
G1 phase
Metabolically active cell duplicates most of its organelles and cytosolic components; replication of chromosomes begins.
S phase
Replication of DNA and centrosomes.
G2 Phase
Cell growth, enzyme and protein synthesis continue; replication of centrosomes complete
channel-mediated facilitated diffusion
a solute moves down its concentration gradient across the lipid bilayer through a membrane channel
carrier-mediated facilitated diffusion
a carrier (also called a transporter) moves a solute down its concentration gradient across the plasma membrane
metaphase
Centromeres of chromatid pairs line up at metaphase plate
aquaporins (AQPs)
integral membrane proteins that function as water channels. AQPs play a critical role in controlling the water content of cells.
hydrostatic pressure
Pressure exerted in this way by a liquid that forces water molecules to move back into the left arm.
tonicity
a measure of the solution’s ability to change the volume of cells by altering their water content
isotonic solution
A solution having the same concentration of impermeable solutes as cytosol
hypotonic solution
Solution that causes cells to swell and perhaps rupture due to gain of water by osmosis
hemolysis
The escape of hemoglobin from the interior of a red blood cell into the surrounding medium; results from disruption of the cell membrane by toxins or drugs, freezing or thawing, or hypotonic solutions
hypertonic
Solution that causes cells to shrink due to loss of water by osmosis.
crenation
shrinkage of cells