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
intravenous solutions
liquids infused into the blood of a vein that are isotonic
sodium-potassium pump
These sodium–potassium pumps maintain a low concentration of Na+ in the cytosol by pumping these ions into the extracellular fluid against the Na+ concentration gradient. At the same time, the pumps move K+ into cells against the K+ concentration gradient.
cellular respiration
Oxidation of glucose to produce ATP; consists of glycolysis, formation of acetyl coenzyme A, the Krebs cycle, and the electron transport chain
vesicle
a small, spherical sac
diploid (2n) cells
Having two sets of chromosomes.
endoderm
A primary germ layer of the developing embryo; gives rise to the digestive canal, urinary bladder, urethra, and respiratory tract.
ectoderm
The primary germ layer that gives rise to the nervous system and the epidermis of skin and its derivatives
microfilaments
Thinnest components of the cytoskeletal, composed of actin and myosin; provide mechanical support and movement (muscle contraction, cell division, and cell locomotion.
pseudopods
Temporary protrusion of the leading edge of a migrating cell; cellular projection that surrounds a particle undergoing phagocytosis.
microtubules
Cylindrical protein filament, from 18 to 30 nm in diameter, consisting of the protein tubulin; provides support, structure, and transportation
pus
The liquid product of inflammation containing leukocytes or their remains and debris of dead cells.
interphase
The period of the cell cycle between cell divisions, consisting of the G1 (gap or growth) phase, when the cell is engaged in growth, metabolism, and production of substances required for division; S (synthesis) phase, during which chromosomes are replicated; and G2 phase.
mitotic spindle
Collective term for a football‐shaped assembly of microtubules (nonkinetochore, kinetochore, and aster) that is responsible for the movement of chromosomes during cell division
meiosis
A type of cell division that occurs during production of gametes, involving two successive nuclear divisions that result in cells with the haploid (n) number of chromosomes.
haploid (n) cells
Having half the number of chromosomes characteristically found in the somatic cells of an organism; characteristic of mature gametes.
leukemia
A malignant disease of the blood-forming tissues characterized by either uncontrolled production and accumulation of immature leukocytes in which many cells fail to reach maturity (acute) or an accumulation of mature leukocytes in the blood because they do not die at the end of their normal life span (chronic)
mesoderm
The middle primary germ layer that gives rise to connective tissues, blood and blood vessels, and muscles
saccules
The inferior and smaller of the two chambers in the membranous labyrinth inside the vestibule of the internal ear containing a receptor organ for linear acceleration or deceleration that occurs in a vertical direction
nucleosome
Structural subunit of a chromosome consisting of histones and DNA
somatic cell division
Type of cell division in which a single starting cell duplicates itself to produce two identical cells; consists of mitosis and cytokinesis
sex chromosomes
The twenty‐third pair of chromosomes, designated X and Y, which determine the genetic sex of an individual; in males, the pair is XY; in females, XX
synapsis
The pairing of homologous chromosomes during prophase I of meiosis
somite
Block of mesodermal cells in a developing embryo that is distinguished into a myotome (which forms most of the skeletal muscles), dermomyotome (which forms the subcutaneous tissue, dermis, and all skeletal muscles of the trunk and limbs), and sclerotome (which forms the vertebrae and ribs)
intermediate saccules
Sacs between the entry and exit faces are called intermediate saccules
transfer vesicles
bud from the edges of the saccules move specific enzymes back toward the entry face and move some partially modified proteins toward the exit face.
secretory vesicles
These vesicles deliver the proteins to the plasma membrane, where they are discharged by exocytosis into the extracellular fluid
membrane vesicles
deliver their contents to the plasma membrane for incorporation into the membrane
mitochondrial cristae
folds
mitochondrial matrix
The central fluid-filled cavity of a mitochondrion, enclosed by the internal mitochondrial membrane
nuclear pores
Each nuclear pore consists of a circular arrangement of proteins surrounding a large central opening that is about 10 times wider than the pore of a channel protein in the plasma membrane.
nuclear envelope
separates the nucleus from the cytoplasm
histones
help organize the coiling and folding of DNA
linker DNA
holds adjacent nucleosomes together.
proteome
all of an organism’s proteins.
gene expression
a gene’s DNA is used as a template for synthesis of a specific protein.
transcription
the genetic information represented by the sequence of base triplets in DNA serves as a template for copying the information into a complementary sequence of codons
messenger RNA (mRNA)
directs the synthesis of a protein.
ribosomal RNA (rRNA)
joins with ribosomal proteins to make ribosomes
transfer RNA (tRNA)
binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation
anticodon
a triplet of nucleotides
RNA polymerase
catalyzes transcription of DNA
promoter
The segment of DNA where transcription begins, a special nucleotide sequence
terminator
specifies the end of the gene
introns
do not code for parts of proteins
exons
do code for segments of a protein.
pre-mRNA
the transcript includes information from both introns and exons
small nuclear ribonucleoproteins
enzymes that cut out the introns and splice together the exons.
alternative splicing
a process in which the pre-mRNA transcribed from a gene is spliced in different ways to produce several different mRNAs.
translation
the nucleotide sequence in an mRNA molecule specifies the amino acid sequence of a protein.
P (peptidyl) site
binds the tRNA carrying the growing polypeptide chain
A (aminoacyl) site
binds the tRNA carrying the next amino acid to be added to the growing polypeptide.
E (exit) site
binds tRNA just before it is released from the ribosome
polyribosome
Several ribosomes attached to the same mRNA
reproductive cell division
the mechanism that produces gametes
kinetochore
a protein complex outside the centromere
metaphase plate
plane of alignment of the centromeres
cleavage furrow
a slight indentation of the plasma membrane, and is completed after telophase
cyclin-dependent protein kinases
enzymes that can transfer a phosphate group from ATP to a protein to activate the protein; other enzymes can remove the phosphate group from the protein to deactivate it.
necrosis
a pathological type of cell death that results from tissue injury.
genetic recombination
the formation of new combinations of genes
telomeres
specific DNA sequences found only at the tips of each chromosome.
carcinomas
malignant tumors that arise from epithelial cells.
melanomas
cancerous growths of melanocytes, skin epithelial cells that produce the pigment melanin
sarcoma
general term for any cancer arising from muscle fibers or connective tissues
osteogenic sarcoma
the most frequent type of childhood cancer, destroys normal bone tissue.
lymphoma
a malignant disease of lymphatic tissue
aniogenesis
the growth of new networks of blood vessels.
