Chapter 3 Flashcards
plasma membrane
cell membrane
nuclear envelope
a double membrane with nuclear pores that surround nucleus
cytoplasm
where most cell activities take place
chromatin
dispersed, thin strands of DNA and associated proteins in nucleus, which condenses to become visible mitotic chromosomes during cell division
nucleolus
consists of ribosomal RNA and proteins
ribosome
site of protein synthesis
Rough endoplasmic reticulum
synthesizes proteins and transports them to the golgi apparatus
Smooth endoplasmic reticulum
Manufactures lipids and carbohydrates; detoxifies harmful chemicals; stores calcium
golgi apparatus
Modifies, packages, and distributes proteins and lipids for secretion or internal use
lysosome
Membrane-bound vesicle pinched off Golgi apparatus; contains digestive enzymes
Peroxisome
Serves as one site of lipid and amino acid degradation; breaks down hydrogen peroxide
Proteasomes
Tubelike protein complexes in the cytoplasm; Break down proteins in the cytoplasm
Mitochondria
ATP synthesis
Centrioles
Pair of cylindrical organelles in the centrosome, consisting of triplets of parallel microtubules; Serve as centers for microtubule formation; determine cell polarity during cell division; form the basal bodies of cilia and flagella
Flagellum
Extension of the plasma membrane; propels spermatozoa
Microvilli
Extension of the plasma membrane containing microfilaments; Increase surface area of the plasma membrane for absorption and secretion; modified to form sensory receptors
membrane potential
regulation of ion movement by cells results in a charge difference across the plasma membrane
glycocalyx
collection of glycolipids, glycoproteins, and carbohydrates on the outer surface of the plasma membrane.
Phospholipids
assemble to form a lipid bilayer
lipid bilayer
double layer of phospholipid molecules
fluid-mosaic model
suggests that the plasma membrane is neither rigid nor static in structure but is highly flexible and can change its shape and composition through time.
Cholesterol
other major lipid in the plasma membrane; limits the movement of phospholipids, providing stability to the plasma membrane
integral proteins (or intrinsic proteins )
protein molecules that penetrate deeply into the lipid bilayer, in many cases extending from one surface to the other
peripheral proteins (or extrinsic proteins )
attached to either the inner or the outer surfaces of the lipid bilayer.
marker molecules
cell surface molecules that allow cells to identify other cells or other molecules.
glycoproteins
proteins with attached carbohydrates
glycolipids
lipids with attached carbohydrates
attachment proteins
allow cells to attach to other cells or to extracellular molecules
Cadherins
proteins that attach cells to other cells
integrins
proteins that attach cells to extracellular molecules.
transport proteins
integral proteins that allow ions or molecules to move from one side of the plasma membrane to the other.
Channel proteins
one or more integral proteins arranged so that they form a tiny channel through the plasma membrane
leak ion channels or non-gated ion channels
channel proteins that are always open and are responsible for the plasma membrane’s permeability to ions when the plasma membrane is at rest.
gated ion channels
channel proteins that can be open or closed.
ligands
small molecules that bind to the proteins or glycoproteins.
ligand-gated ion channels
gated ion channels that open or close in response to
chemical signals or ligands
voltage-gated ion channels
gated ion channels that open or close when there is a change in charge across the plasma membrane
Carrier proteins or transporters
integral membrane proteins that move ions or molecules from one side of the plasma membrane to the other.
Uniport
the movement of one specific ion or molecule across the membrane.
Symport
the movement of two different ions or molecules in the same direction across the plasma membrane
antiport
the movement of two different ions or molecules in opposite directions across the plasma membrane.
ATP-powered pumps
transport proteins that move specific ions and molecules from one side of the plasma membrane to the other.
Receptor proteins
proteins or glycoproteins in the plasma membrane that have an exposed receptor site on the outer cell surface
cystic fibrosis
a genetic disorder that affects chloride ion channels.
G protein complex
located on the inner surface of the plasma membrane which acts as an intermediary between a receptor and other cellular proteins.
selectively permeable
allows only certain substances to pass through it.
vesicle
small, membrane-bound sac that can transport large, non-lipid-soluble molecules, small pieces of matter and even whole cells across the plasma membrane
Diffusion
the movement of solutes from an area of higher solute concentration to an area of lower solute concentration
concentration gradient
The concentration difference between two points, divided by the distance between the two points
Viscosity
a measure of how easily a liquid flows
Osmosis
the diffusion of water (solvent) across a selectively permeable membrane
Selectively permeable
the membrane allows water but not all the solutes dissolved in the water to diffuse through it.
Aquaporins or water channel proteins
increase membrane permeability to water in some cell types, such as kidney cells.
Osmotic pressure
the force required to prevent water from moving by osmosis across a selectively permeable membrane.
isosmotic
Solutions with the same concentration of solute particles that have the same osmotic pressure even if the types of solute particles in the two solutions differ from each other.
hyperosmotic
solution that has a greater concentration of solute particles, and therefore a greater osmotic pressure than another solution
hyposmotic
when a solution is more dilute, with the lower osmotic pressure compared with the more concentrated solution.
isotonic
when a cell placed into a solution neither shrinks nor swells
tonicity
the shape of the cell remains constant, maintaining its internal tension or tone
hypertonic
when a cell is placed into a solution and water moves out of the cell by osmosis, causing the cell to shrink
hypotonic
when a cell is placed into a solution and water moves into the cell by osmosis, causing the cell to swell
crenation
in red blood cells, when water moves by osmosis from the cell into the hypertonic solution, causing the cell to shrinks
lysis
when a cell swells too much and ruptures
Mediated transport
the process by which transport proteins mediate, or assist, the movement of large, water-soluble molecules or electrically charged molecules or ions across the plasma membrane.
Specificity
each transport protein binds to and transports only a single type of molecule or ion
Competition
the result of similar molecules binding to the transport protein
Saturation
the rate of movement of molecules across the membrane
is limited by the number of available transport proteins
Facilitated diffusion
a carrier-mediated or channel-mediated process that moves substances into or out of cells from a higher to a lower concentration
Active transport
a mediated transport process that requires energy provided by ATP; can move from lower to higher concentrations
sodium-potassium pump; sodium-potassium ATP-ase
active transport system that moves Na + out of cells and K + into cells
Secondary active transport
involves the active transport of an ion, such as sodium, out of a cell, establishing a concentration gradient, with a higher concentration of the ions outside the cell.
Endocytosis
the uptake of material through the plasma membrane by the formation of a vesicle; phagocytosis and pinocytosis
receptor-mediated endocytosis
when the plasma membrane contains specific receptor molecules that recognize certain substances and allow them to be transported into the cell by phagocytosis or pinocytosis.
Hypercholesterolemia
common genetic disorder characterized by the reduction in or absence of low-density lipoprotein (LDL) receptors on cell surfaces, which interferes with the receptor-mediated endocytosis of LDL cholesterol; results in too much production of cholestrol
exocytosis
when secretions accumulate within vesicles, move to the plasma membrane, and fuse there, then contents are expelled from the cell.
Cytosol
fluid portion of the cytoplasm, which contains the cytoskeleton and cytoplasmic inclusions.
cytoskeleton
supports the cell and holds the nucleus and other organelles in place.
Microtubules
hollow tubes composed primarily of protein units called tubulin; help provide support and structure to the cytoplasm of the cell, much like an internal scaffolding; they are involved in cell division and in the transport of intracellular materials; and they form essential components of certain cell organelles, such as centrioles, spindle fibers,
cilia, and flagella.
Actin filaments or microfilaments
small fibrils that form bundles, sheets, or networks in the
cytoplasm; provide structure to the cytoplasm and mechanical support for microvilli, support the plasma membrane, and define the shape of the cell.
Intermediate filaments
protein fibers that provide mechanical strength to cells and support the extensions of nerve cells.
cytoplasmic inclusions
aggregates of chemicals either produced or taken in by the cell; contained in cytosol
lipo-chromes
pigments that increase in amount with age.
nuclear pores
At many points on the surface of the nuclear envelope, the
inner and outer membranes fuse to form porelike structures
Deoxyribonucleic acid (DNA)
mostly found within the nucleus with small amounts found within mitochondria; DNA and associated proteins are organized into chromosomes and histones
histones
important for the structural organization of DNA
chromatin
During most of the cell’s life cycle, the chromosomes are dispersed throughout the nucleus as these delicate filaments; during cell division the dispersed chromatin
becomes densely coiled, forming compact chromosomes.
ribonucleic acid (RNA)
can leave the nucleus through nuclear pores;
gene
A sequence of nucleotides in a DNA molecule that specifies the structure of a protein or RNA molecule
Ribosomes
sites of protein synthesis; consist of ribosomal RNA (rRNA)
and proteins; produced separately in the nucleolus
Free ribosomes
primarily synthesize proteins used inside the cell, whereas ribosomes attached to the endoplasmic reticulum usually produce proteins that are secreted from the cell.
cisternae
interior spaces of organelle sacs and tubules that are isolated from the rest of the cytoplasm.
smooth endoplasmic reticulum
manufactures lipids, such as phospholipids, cholesterol, and steroid hormones, as well as carbohydrates; phospholipids help form vesicles; enzymes help reduce chemical toxicity
rough endoplasmic reticulum
where proteins are produced and modified for secretion and for internal use.
Golgi Apparatus
modifies, packages, and distributes proteins and lipids manufactured by the rough and smooth endoplasmic reticula
transport vesicles
proteins produced in ribosomes and packaged into transport vesicles that move to the Golgi apparatus, fuse with the Golgi membrane, and release the protein into the Golgi apparatus cisterna.
secretory vesicles
membrane-bound; pinch off from the Golgi, move to the surface of the cell, their membranes fuse with the plasma membrane, and the contents of the vesicle are released to the exterior by exocytosis.
Lysosomes
membrane-bound vesicles that form at the Golgi; contain a variety of hydrolytic enzymes that function as intracellular digestive systems.
autophagia
when lysosomes also digest the organelles of the cell that are no longer functional
Peroxisomes
membrane-bound vesicles; smaller than lysosomes; contain enzymes that break down fatty and amino acids; hydrogen peroxide is a byproduct of the breakdown.
catalase
enzyme that breaks down hydrogen peroxide to water and oxygen.
Pompe disease
rare genetic disorder caused by the inability of lysosomal enzymes to break down glycogen.
Familial hyperlipoproteinemia
group of genetic disorders that occur when large amounts of lipids accumulate in phagocytic cells that lack the normal enzymes required to break down the lipid droplets.
Mucopolysaccharidoses, such as Hurler syndrome
genetic diseases in which lysosomal enzymes are unable to break down mucopolysaccharides (glycosaminoglycans), so these molecules accumulate in the lysosomes of connective tissue cells and nerve cells.
Proteasomes
consist of large protein complexes, including several enzymes that break down and recycle other proteins within the cell.
cristae
infoldings that project like shelves into the interior of the mitochondrion.
matrix
substance located in the space formed by the inner membrane.
mitochondrial diseases
Disorders that result from changes in mitochondrial genes that can lead to disruptions in normal ATP synthesis, reducing the amount of ATP produced by the cells.
Leber hereditary optic neuropathy
results in sudden vision loss due to optic nerve degeneration.
centrosome
specialized zone of cytoplasm close to the nucleus; center of microtubule formation in the cell.
spindle fibers
extend out in all directions from the centrosome; attaches to a chromosome and stops growing or shrinking during cell division.
Dynein arms
proteins connecting adjacent pairs of microtubules
basal body
modified centriole
Flagella
similar structure to cilia, but longer; sperm
Genes
functional units of heredity, the transmission of genetic traits from parent to offspring.
gene expression
production of proteins from the information stored in DNA; involves transcription and translation
transcription
copy of; transcription is the synthesis of mRNA, tRNA, and rRNA based on the nucleotide sequence in DNA
translation
changing of something from one form to another
transfer RNA (tRNA)
transport molecules that transfer RNA (tRNA) and carry the amino acids to the ribosomes
RNA polymerase
enzyme that synthesizes the complementary RNA molecule from DNA.
promoter
a DNA nucleotide sequence that RNA polymerase attaches to; the attachment of RNA polymerase to the promoter causes a portion of the DNA molecule to unwind, exposing the nucleotide sequence
transcription factors
other proteins that the RNA must first associate with in order to interact with the DNA.
terminator
a DNA nucleotide sequence that when RNA polymerase
encounters it, it detaches from the DNA, releasing the newly formed mRNA.
exons
Regions of the mRNA that code for proteins
introns
non-protein-coding regions
pre-mRNA
An mRNA that contains introns; functional mRNA consists only of exons
posttranscriptional processing
modifications made before a pre-mRNA leaves the nucleus, which produces the functional mRNA that is used in translation to produce a protein
poly-A tail
added to one end of the mRNA and a 7-methyl guanosine cap is added to the other end; ensure that mRNA travels from the nucleus to the cytoplasm and interacts with ribosomes during translation
alternative splicing
when various combinations of exons are incorporated into mRNA
genetic code
information contained in mRNA
codons
genetic code is carried in these sets of three nucleotide units
start codon
signals the beginning of translation
stop codons
signal the end of translation
ribosomal RNA (rRNA)
The function of tRNA is to match a specific amino acid to a specific codon of mRNA.
anticodon
consists of three nucleotides and is complementary to a particular codon of mRNA
polyribosome
resulting cluster of ribosomes attached to the mRNA after a ribosome uses the initial part of mRNA, another ribosome can attach to the mRNA and begin to make a protein
proproteins
longer when they are first made than in their final, functional state; extra piece of the molecule is cleaved off by enzymes to make the proprotein into a functional protein.
proenzymes
the proproteins of the proteins that are enzymes
posttranslational processing
various modifications to proteins
cell life cycle
the changes a cell undergoes from the time it is formed until it divides to produce two new cells; two stages: interphase and cell division (mitosis and cytokinesis)
Interphase
phase between cell divisions; 90% or more of the life cycle of a typical cell is spent in interphase.
DNA replication
process by which two new strands of DNA are made, using the two existing strands as templates.
DNA polymerase
an enzyme that adds new nucleotides to the 3′ end of the growing strands.
leading strand
forms as a continuous strand
lagging strand
forms in short segments called Okazaki fragments .
DNA ligase
splic Okazaki fragments
Mitosis
division of a cell’s chromosomes into two new nuclei, each of which has the same amount and type of DNA as the original nucleus.
mitotic chromosomes
During mitosis, the chromatin becomes very densely coiled to form these compact chromosomes
chromatids
one of the two copies of the original chromosome each mitotic chromosome consists of
centromere
where the chromatids are attached
kinetochore
protein structure that binds the centromere and provides a point of attachment for microtubules that will move the chromatids during mitosis
prophase
chromatin condenses to form mitotic chromosomes; spindle fibers extend from the centrioles to the centromeres of the chromosomes; the centrioles divide and migrate to each pole of the cell; in late prophase, the nucleolus and nuclear envelope disappear.
metaphase
chromosomes align near the center of the cell.
anaphase
the chromatids separate; at this point, two identical sets of chromosomes are moved by the spindle fibers toward the centrioles at one of the poles of the cell. At the end of anaphase, each set of chromosomes has reached an opposite pole of the cell, and the cytoplasm begins to divide.
telophase
nuclear envelopes form around each set of chromosomes to form two separate nuclei; The chromosomes begin to uncoil and resemble the genetic material characteristic of interphase.
Cytokinesis
division of the cell’s cytoplasm to produce two new cells.
cleavage furrow
an indentation of the plasma membrane that forms midway between the centrioles.
Genetics
the study of heredity—that is, the characteristics children inherit from their parents.
Mendelian genetics
study of how genetic traits are passed from parent to offspring
genomic medicine
genetic approach to the diagnosis and management of disease
gametes
sex cells
genotype
The genes an organism has for a given trait
phenotype
The expression of the genes as a trait
alleles
Alternate forms of genes
dominant allele
mask the effects of the recessive allele for that trait
homozygous
the two alleles for the trait are identical
heterozygous
the two alleles for the trait are different
polydactyly
has extra fingers or toes; dominant expression
Somatic cells
all the cells of the body except the gametes.
diploid number
normal number of chromosomes in a somatic cell; 46 chromosomes
haploid
normal number of chromosomes in a gamete; 23 chromosomes
autosomal chromosomes
all the chromosomes except the sex chromosomes; 22 pairs
sex chromosomes
determines the sex of the individual; 1 pair; X or Y chromosomes
karyotype
a display of the chromosomes of a somatic cell during metaphase of mitosis.
homologous chromosomes
Chromosome pairs; each member of the pair is a homolog; 1 from mother, 1 from father
genome
all the genes found in the haploid number of chromosomes from one parent.
locus
location, on a chromosome; each gene of the genome occupies a specific locus
multiple alleles
alleles can exist in many forms; Differences in alleles arise by mutation
allelic variant
different form of an allele, or mutated allele (gene), or a polymorphism (many forms).
phenylketonuria (PKU)
autosomal recessive trait with multiple alleles.
complete dominance
homozygous dominant and the heterozygote had the same phenotype
codominance
two alleles at the same locus are expressed so that separate, distinguishable phenotypes occur at the same time; blood types
incomplete dominance
the dominant allele does not completely mask the effects of the recessive allele in the heterozygote; beta, major, and minor thalassemia
polygenic traits
result from the interactions of many genes; height, intelligence, eye color, and skin color.
Sex-linked traits
traits affected by genes on the sex chromosomes
X-linked traits
affected by genes on the X chromosome; most sex-linked traits are X-linked
Y-linked traits
affected by genes on the Y chromosome.
meiosis
cell division that reduces chromosome number by half; gametes are produced that have one homolog from each of the homologous pairs of chromosomes.
carrier
carrier for a recessive trait is a person who is heterozygous for that trait, with one normal allele and one disorder-causing allele. The carrier does not exhibit the disorder
but can pass it on to his or her children.
genetic disorder
a failure of structure, function, or both as a result of abnormalities in a person’s genetic makeup- DNA
mutagens
Agents that cause mutations
point mutation
A mutation involving a single nucleotide change
structural mutations
Mutations that change the sequence or number of nucleotides involve changes in chromosome structure
nondisjunction
As the chromosomes separate during meiosis, the two members of a homologous pair may not segregate as they normally do. As a result, one of the daughter cells receives both chromosomes, and the other daughter cell receives none.
aneuploidy
zygote with 47 chromosomes or 45 chromosomes rather
than the normal 46
Down syndrome or trisomy 21
type of aneuploidy in which three chromosomes 21 are present.
syndrome
set of signs and symptoms occurring together as the result of a single cause, such as a single mutation or one extra chromosome
Cancer
usually results from a series of somatic mutations that cause uncontrolled cell division and changes in the normal functions of cells.
genomic map
depicts the DNA nucleotide sequences of the genes and their locations on the chromosomes
gene therapy or genetic engineering
repairs or replaces defective genes or gene products, resulting in cures or treatments for genetic disorders.
