Anatomy Lecture Ch 3 Flashcards
The Cellular Level of Organization
plasma membrane
cell’s flexible outer surface, separating the cell’s internal environment from the external environment
selective barrier that regulates the flow of materials into and out of a cell
communication between cells and external environment
cytoplasm
consists of all the cellular contents between the plasma membrane and the nucleus; cytosol and organelles contained within
cytosol
the fluid portion of cytoplasm; contains water, dissolved solutes, and suspended particles
nucleus
a large organelle that houses most of a cell’s DNA
chromosome
a single molecule of DNA
genes
hereditary units that control most aspects of cellular structure and function
fluid mosaic model
the molecular arrangement of the plasma membrane resembles a continually moving sea of fluid lipids that contains a mosaic of many different proteins
lipid bilayer
two back-to-back layers made up of three types of lipid molecules: phospholipids, cholesterol, and glycolipids
phosphoplipid
about 75% of the membrane lipids
contain phosphorus
cholesterol
a steroid with an attached OH group
glycolipids
lipids with attached carbohydrate groups
amphipathic
lipids have both polar and nonpolar parts
integral proteins
extend into or through the lipid bilayer and are firmly embedded in it
transmembrane proteins
span the entire lipid bilayer and protrude into both the cytosol and extracellular fluid
peripheral proteins
not as firmly embedded in the membrane
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 formed by the carbohydrate portions of glycolipids and glycoproteins
ion channels
pores or holes formed by integral proteins that specific ions can flow through to get into or out of the cell
most ion channels only allow a single type of ion to pass through
carriers
some integral proteins act as carriers and selectively move a polar substance or ion from one side of the membrane to the other
receptors
cellular recognition sites
each type of receptor recognizes and binds a specific type of molecule
ligand
a specific molecule that binds to a receptor
enzymes
catalyze specific chemical reactions
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
enable a cell to recognize other cells of the same kind during tissue formation or recognize and respond to potentially dangerous foreign cells
blood types are a form of cell-identity markers
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 different in electrical charges between two regions
electrochemical gradient
combined influence of the concentration gradient and the electrical gradient on movement of a particular ion
passive transport processes
a substance moves down its concentration gradient
moves from higher to lower concentration
uses only the cell’s kinetic energy
active transport processes
cellular energy is used to drive the substance against its concentration or electrical gradient
moves from lower to higher concentration
requires ATP
vesicles
tiny, spherical membrane sacs used into transport
diffusion
a passive process in which the random mixing of particles in a solution occurs because of the particles’ kinetic energy
simple diffusion
a passive process in which substances move freely through the lipid bilayer of the plasma membranes of cells without the help of membrane transport proteins
facilitated diffusion
used with solutes that are too polar or highly charged
an integral membrane protein assists a specific substance across the membrane
the integral membrane proteins can either form a channel or act as a carrier
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 moves a solute down its concentration gradient across the plasma membrane
this is a passive process so no cellular energy is required
osmosis
a type of diffusion in which there is net movement of a solvent through a selectively permeable membrane
passive process
aquaporins (AQPs)
integral membrane proteins that function as water channels
play a critical role in controlling the water content of cells
osmotic pressure
proportionate to the concentration of the solute particles that cannot cross the membrane
the higher the solute concentration, the higher the solution’s osmotic pressure
tonicity
a measure of the solution’s ability to change the volume of cells by altering their water content
isotonic solution
any solution in which a cell maintains it normal shape and volume
hypotonic solution
a solution that has a lower concentration of solutes than the cytosol inside the RBCs
hemolysis
rupture of RBCs
lysis
the rupture of other type of cells due to placement in a hypotonic solution
hypertonic solution
higher concentration of solutes than does the cytosol inside RBCs
crenation
shrinkage of cells when placed in a hypertonic solution
active transport
energy is required for carrier proteins to move solutions across the membrane against a concentration gradient
primary active transport
energy derived from hydrolysis of ATP changes the shape of a carrier proteins which pumps a substance across a plasma membrane against its concentration gradient
secondary active transport
the energy stored in a Na+ or H+ concentration gradient is used to drive other substances across the membrane against their own concentration gradients
pumps
carrier proteins that mediate primary active transport
symporters
transporters that move two substances in the same direction
antiporters
transporters that move two substances in opposite directions
endocytosis
materials move into a cell in a vesicle formed from the plasma membrane
requires ATP
exocytosis
materials move out of a cell by the fusion with the plasma membrane of vesicles formed inside the cell
requires ATP
receptor-mediated endocytosis
highly selective type of endocytosis by which cells take up specific ligands
binding, vesicle formation, uncoating, fusion with endosome, recycling of receptors to plasma membrane, degradation in lysosomes
phagocytosis
a form of endocytosis in which the cell engulfs large solid particles, such as worn-out cells, whole bacteria, or viruses
phagocytes
cells that are able to carry out phagocytosis
pseudopods
projections of the plasma membrane and cytoplasm of the phagocyte
phagosome
vesicle used in phagocytosis
pinocytosis
a form of endocytosis in which tiny droplets of extracellular fluid are taken up
no receptor proteins involved
transcytosis
transport in vesicles to move substances into, across, and out of a cell
active process
undergo endocytosis, move across the cell, undergo exocytosis on the opposite side
occurs most often in endothelial cells that line blood vessels
cytoskeleton
a network of protein filaments that extends throughout the cytosol
microfilaments
the thinnest elements of the cytoskeleton
composed of the proteins actin of myosin and are most prevalent at the edge of the cell
help generate movement
provide mechanical support
microvilli
nonmotile, microscopic fingerlike projections of the plasma membrane
intermediate filaments
thicker than microfilaments but thinner than microtubules
found in parts of cells subject to mechanical stress; help stabilize the position of organelles such as the nucleus and help attach cells to one another
microtubules
the largest of the cytoskeletal components; long, unbranched hollow tubes composed mainly of the protein tubulin
help determine cell shape; function in the movement of organelles such as secretory vesicles, of chromosomes during cell division, and of specialized cell projections, such as cilia and flagella
organelles
specialized structures within the cell that have characteristic shapes; perform specific functions in cellular growth, maintenance, and reproduction
pericentriolar matrix
contains hundreds or ring-shaped complexes composed of the protein tubulin
saccules
small, flattened membranous sacs with bulging edges
convex entry face
a saccule that faces the rough ER
concave exit face
a saccule that faces the plasma membrane
intermediate saccules
sacs between the entry and exit faces
transfer vesicles
bud from the edges of the saccules and move specific enzymes back toward the entry face and move some partially modified proteins toward the exit face
secretory 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
autophagy
the process by which entire worn-out organelles are digested
autophagosome
the organelle to be digested is enclosed by a membrane derived from the ER to create a vesicle called an autophagosome
autolysis
the destruction of an entire cell
chromatin
complex of DNA, proteins, and some RNA
genome
total genetic information carried in a cell of an organism
nucleosome
“beads” on the string of chromatin that consist of double-stranded DNA wrapped twice around a core of eight proteins
histone
a core of eight proteins which help organize the coiling and folding of DNA
linker DNA
the string between the beads of chromatin that holds adjacent nucleosomes together
chromatin fiber
coiling of nucleosomes that folds into larger loops
chromatids
a pair of DNA fibers that form a chromosome
proteome
all of an organism’s proteins
gene expression
a process in which a gene’s DNA is use as a template for synthesis of a specific protein
base triplet
genetic information stores as sets of three nucleotides
codon
complementary sequence of three nucleotides
genetic code
the set of rules that relate the base triplet sequence of DNA to the corresponding codons of RNA and the amino acids they specify
transcription
occurs in the nucleus; 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 ammino acid and holds it in place on a ribosome until it is incorporated into a protein during translation
RNA polymerase
enzyme that catalyzes transcription of DNA
terminator
special nucleotide sequence that specifies the end of a gene
translation
an mRNA molecule binds to a ribosome; the mRNA nucleotide sequence specifies the amino acid sequence of a protein
polyribosome
several ribosomes attached to the same mRNA
somatic cell
any cell of the body other than sex cell
germ cell
a gamete or any precursor cell destined to become a gamete
mitosis
a type of cell division involving the distribution of two sets of chromosomes into two separate nuclei
homologous chromosomes
two chromosomes that make up each of the 23 pairs
diploid cells
contain 2 sets of chromosomes; somatic cells
interphase
when a cell is not dividing; consists of G1, G2 and S phases; chromosomes are not visible under light microscope
G1 phase
metabolically active cell duplicates most of its organelles and cytosolic components; replication of chromosomes begins
G0 phase
cells that remain in G1 for a very long time, perhaps never divide again; most nerve cells are in G0
S phase
interval between G1 and G2; replication of DNA and centrosomes
G2 phase
cell growth, enzyme and protein synthesis continue; replication of centrosomes complete
mitotic phase
results in the formation of two identical cells, consists of a nuclear division (mitosis) and a cytoplasmic division (cytokinesis) to form two identical cells
prophase
chromatin fibers condense into paired chromatids; nucleolus and nuclear envelope disappear; each centrosome moves to an opposite pole of the cell
metaphase
centromeres of chromatid pairs line up at metaphase plate
anaphase
centromeres split; identical sets of chromosomes move to opposite poles of cell
telophase
nuclear envelopes and nucleoli reappear; chromosomes resume chromatin form; mitotic spindle disappears
cytokinesis
cytoplasmic division; contractile ring forms cleavage furrow around center of cell, dividing cytoplasm into separate and equal portions
cleavage furrow
a slight indentation of the plasma membrane
necrosis
a pathological type of cell death that results from tissue injury
meiosis
reproductive cell division that occurs in the gonads (ovaries and testes) produces gametes in which the number of chromosomes is reduced by half
haploid cells
gametes; contain a single set of 23 chromosomes
meiosis I
begins once chromosomal replication is complete, consists of prophase I, metaphase I, anaphase I, and telophase I
prophase I
same as mitotic prophase with addition of two events; two sister chromatids of each pair of homologous chromosomes pair off which is call synapsis; parts of the chromatids of two homologous chromosomes may be exchanged with one another in crossing-over
genetic recombination
crossing-over results in a new combination of genes
metaphase I
tetrads line up along the metaphase plate
anaphase I
members of each homologous pair of chromosomes separate as they are pulled to opposite poles of the cells by the microtubules attached to the centromeres; paired chromatids remain together
telophase I
similar to mitotic telophase
meiosis II
prophase II, metaphase II, anaphase II, telophase II; centromeres split, sister chromatids separate and move toward opposite poles
telomeres
specific DNA sequences found at the tips of each chromosome; protect the tips of chromosomes from erosion and from sticking to one another
