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Anatomy Exam 1: Cells and Mitosis flashcards | Quizlet
Created by saramarina
Three major components of a human cell.
Plasma membrane
Cytoplasm
Organelles
Plasma membrane two major roles?
Regulator of what goes in and what comes
out.
Plays a key role in communication among
cells and between cells and their external
environment.
What are the major chemical
components?
Lipids and proteins (phospholipids,
cholesterol molecules, and glycolipids)
Phospholipids
About 75% of the membrane lipids are
phospholipids, lipids that contain
phosphorus.
Cholesterol molecules
20% of the plasma membrane lipids are
cholesterol molecules, which are
interspersed among other lipid in both
layers of the membrane.
Glycolipids
are lipids attached to carbohydrates,
account for the other 5%
What are the two membrane proteins?
Integral and peripheral proteins
Integral proteins
extend into or through the lipid bilayer and
are firmly embedded in it.
Peripheral proteins
are not as firmly embedded in the
membrane as the integral proteins, and are
attached to membrane lipids or integral
proteins at the inner or outer surface of the
membrane.
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Functions of membrane proteins
a. form ion channels b. carriers or
transporters c. receptors d. some are
enzymes that catalyze specific chemical
reactions e. they can serve as linkers f. cell
g. identity markers.
What does it mean that the plasma
membrane has selective permeability?
permeable means that a structure, such as
a membrane, permits the passage of
substances through it, while impermeable
means that a structure does not permit the
passage of substances through it. Although
plasma membranes are not completely
permeable to any substance, they do
permit some substances to pass more
readily than others. This property of
membranes is called selective
permeability.
Passive processes (transport)
In passive processes, substances move
across a plasma membrane, due to their
own kinetic energy, down a concentration
gradient.
There are several types of passive
processes...what are they called?
Diffusion, osmosis, facilitated diffusion,
and filtration.
Diffusion
is a passive process in which there is a net
(greater) movement of a substance from a
region of higher concentration to a region
of lower concentration—that is, the
substance moves from an area where
there is more of it to an area where there
is less of it. The substance moves because
of its kinetic energy. A good example of
diffusion in the body is the movement of
oxygen from the blood into the body cells
and the movement of carbon dioxide from
the cells back into the blood. This
movement ensures that cells receive
adequate amounts of oxygen and eliminate
carbon dioxide as part of their normal
metabolism.
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Osmosis
is the net movement of water molecules
through a selectively permeable membrane
from an area of higher water concentration
(lower concentration of solutes, dissolved
substances) to an area of lower water
concentration (higher solute
concentration). It is also a passive
process. The water molecules pass
through pores (holes) in integral proteins in
the membrane and between neighboring
phospholipid molecules due to their kinetic
energy, and the net movement continues
until equilibrium is reached. Water moves
between various compartments of the
body by osmosis.
facilitated diffusion
is a passive process that is accomplished
with the assistance of transmembrane
proteins functioning as carriers. In this
process, some large molecules and
molecules that are insoluble in lipids can
still pass through the plasma membrane.
Among these are various sugars,
especially glucose. In facilitated diffusion,
glucose binds to a specific carrier protein
on one side of the plasma membrane, the
carrier undergoes a change in shape, and,
as a result, glucose is released on the
opposite side of the membrane.
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Active transport
The process by which substances, usually
ions, are transported across plasma
membranes with the expenditure of energy
by the cell, typically from an area of lower
concentration to an area of higher
concentration, is called active transport. In
active transport the substance being
moved makes contact with a specific site
on a transporter protein. Then the ATP
splits, and the energy from the breakdown
of ATP causes a change in the shape of
the transporter protein that expels the
substance on the opposite side of the
membrane. Active transport is considered
an active process because energy is
required for transporter proteins to move
substances across the membrane against a
concentration gradient.
Vesicular transport
A vesicle (VES-i-kul; vescula=little blister
or bladder), as noted earlier, is a small,
spherical, membranous sac formed by
budding off from an existing membrane.
Vesicles transport substances from one
structure to another within cells, take in
substances from extracellular fluid, or
release substances into extracellular fluid.
Endocytosis
In endocytosis (endo-=within), materials
move into a cell in a vesicle formed from
the plasma membrane. In exocytosis (exo=out), materials move out of a cell by the
fusion of vesicles, formed inside a cell,
with the plasma membrane. Both
endocytosis and exocytosis require cellular
energy supplied by the breakdown of
ATP. Thus transport in vesicles is an
active process.
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Receptor-mediated endocytosis
a highly selective type of endocytosis, cells
take up specific ligands. (Recall that
ligands are molecules that bind to specific
receptors.) A vesicle forms after a
receptor protein in the plasma membrane
recognizes and binds to a particular
particle in the extracellular fluid. For
instance, cells take up cholesterol
contained in low-density lipoproteins
(LDLs), transferrin (an iron-transporting
protein in the blood), some vitamins,
antibodies, and certain hormones by
receptor-mediated endocytosis.
Receptor-mediated endocytosis of LDLs
(and other ligands) occurs as follows
Phagocytosis
(from Ancient Greek phago, meaning
"eating", kytos, meaning "cell", and -osis,
meaning "process") is the cellular process
of engulfing solid particles by the cell
membrane to form an internal phagosome
by phagocytes and protists.
pinocytosis
a form of endocytosis in which tiny
droplets of extracellular fluid are taken up.
No receptor proteins are involved; all
solutes dissolved in the extracellular fluid
are brought into the cell. During bulkphase endocytosis, the plasma membrane
folds inward and forms a vesicle
containing a droplet of extracellular fluid.
The vesicle detaches or "pinches off" from
the plasma membrane and enters the
cytosol. Within the cell, the vesicle fuses
with a lysosome, where enzymes degrade
the engulfed solutes. The resulting smaller
molecules, such as amino acids and fatty
acids, leave the lysosome to be used
elsewhere in the cell. Bulk-phase
endocytosis occurs in most cells,
especially absorptive cells in the intestines
and kidneys.
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Exocytosis
In contrast with endocytosis, which brings
materials into a cell, exocytosis releases
materials from a cell. Just remember that
endo means "in," and exo means "out." All
cells carry out exocytosis, but it is
especially important in two types of cells:
(1) secretory cells that liberate digestive
enzymes, hormones, mucus, or other
secretions; and (2) nerve cells that release
substances called neurotransmitters. In
some cases, wastes are also released by
exocytosis. During exocytosis, membraneenclosed vesicles called secretory vesicles
form inside the cell, fuse with the plasma
membrane, and release their contents into
the extracellular fluid.
Transcytosis
Transport in vesicles may also be used to
successively move a substance into,
across, and out of a cell. In this active
process, called transcytosis, vesicles
undergo endocytosis on one side of a cell,
move across the cell, and then undergo
exocytosis on the opposite side. As the
vesicles fuse with the plasma membrane,
the vesicular contents are released into the
extracellular fluid. Transcytosis occurs
most often across the endothelial cells that
line blood vessels and is a means for
materials to move between blood plasma
and interstitial fluid. For instance, when a
woman is pregnant, some of her
antibodies cross the placenta into the fetal
circulation via transcytosis.
Cytoplasm
consists of all the cellular contents within
the plasma membrane except for the
nucleus, and has two components: (1)
cytosol and (2) organelles, tiny structures
that perform different functions in the cell.
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Function of cytoplasm
The cytosol is the site of many chemical
reactions required for a cell's existence.
For example, enzymes in cytosol catalyze
numerous chemical reactions. As a result
of these reactions, energy is released and
captured to drive cellular activities. In
addition, these reactions provide the
building blocks for maintaining cell
structure, function, and growth.
Structure of the cytoplasm
The cytosol (intracellular fluid) is the fluid
portion of the cytoplasm that surrounds
organelles (see Figure 2-1) and constitutes
about 55% of total cell volume. Although
it varies in composition and consistency
from one part of a cell to another, cytosol
is 75-90% water plus various dissolved
and suspended components. Among these
are different types of ions, glucose, amino
acids, fatty acids, proteins, lipids, ATP,
and waste products. Also present in some
cells are various organic molecules that
aggregate into masses for storage. These
aggregations may appear and disappear at
different times in the life of a cell.
Examples include lipid droplets that
contain triglycerides, and clusters of
glycogen molecules called glycogen
granules (see Figure 2-1).
What are organelles?
intracellular structures that have
characteristics shapes and perform
specialized functions.
Cytoskeleton
a network of three types of protein
filaments that provide shape to the cell and
play roles in cell movement as well as in
movement of organelles within cells.
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microfilaments
These are the thinnest elements of the
cytoskeleton. They are concentrated at the
periphery (near the plasma membrane) of
a cell. They are composed of the protein
actin and have two general functions:
movement and mechanical support. With
respect to movement, microfilaments are
involved in muscle contraction, cell
division, and cell locomotion. Cell
locomotion occurs during the migration of
embryonic cells during development, the
invasion of tissues by white blood cells to
fight infection, or the migration of skin cells
during wound healing.
microtubules
The largest of the cytoskeletal
components, microtubules are long,
unbranched hollow tubes composed
mainly of a protein called tubulin. The
centrosome serves as the initiation site for
the assembly of microtubules. The
microtubules grow outward from the
centrosome toward the periphery of the
cell. Microtubules help determine cell
shape and function in the intracellular
transport of organelles, such as secretory
vesicles, and the migration of
chromosomes during cell division. They
also participate in the movement of
specialized cell projections such as cilia
and flagella.
intermediate filaments
are thicker than microfilaments but thinner
than microtubules. Several different
proteins can compose intermediate
filaments, which are exceptionally strong.
They are found in parts of cells subject to
mechanical stress and help anchor
organelles such as the nucleus and attach
cells to one another.
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Function of the centrosome
Function
The pericentriolar material of the
centrosome contains tubulins that build
microtubules in nondividing cells and form
the mitotic spindle during cell division.
Structure of the centrosome?
located near the nucleus, consists of two
components: a pair of centrioles and
pericentriolar material. The two centrioles
are cylindrical structures, each composed
of nine clusters of three microtubules
(triplets) arranged in a circular pattern.
The long axis of one centriole is at a right
angle to the long axis of the other.
Surrounding the centrioles is pericentriolar
material, which contains hundreds of ringshaped complexes composed of the
protein tubulin. These tubulin complexes
are the organizing centers for growth of
the mitotic spindle, which plays a critical
role in cell division, and for microtubule
formation in nondividing cells. During cell
division, centrosomes replicate so that
succeeding generations of cells have the
capacity for cell division.
What is a cilia?
Cilia (singular is cilium) are numerous,
short, hairlike projections that extend from
the surface of the cell. Each cilium contains
a core of 20 microtubules surrounded by
plasma membrane. These 20 microtubules
are arranged with one pair in the center
surrounded by nine clusters of two fused
microtubules (doublets). Each cilium is
anchored to a basal body just below the
surface of the plasma membrane. A basal
body is similar in structure to a centriole
and functions in initiating the assembly of
cilia and flagella.
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Function of cilia?
Functions
1. Cilia move fluids along a cell's surface.
The coordinated movement of many cilia
on the surface of a cell causes the steady
movement of fluid along the cell's surface.
Many cells of the respiratory tract, for
example, have hundreds of cilia that help
sweep foreign particles trapped in mucus
away from the lungs. The extremely thick
mucus secretions that are produced in
people who suffer from cystic fibrosis
interfere with ciliary action and the normal
functions of the respiratory tract. The
movement of cilia is also paralyzed by
nicotine in cigarette smoke. For this
reason, smokers cough often to remove
foreign particles from their airways.
Because cells that line the uterine
(fallopian) tubes also have cilia that sweep
oocytes (egg cells) toward the uterus,
females who smoke have an increased risk
of ectopic (outside the uterus) pregnancy.
What's the structure and function of
flagella?
Flagella (singular is flagellum) are similar in
structure to cilia but are typically much
longer. Flagella usually move an entire cell.
The only example of a flagellum in the
human body is a sperm cell's tail, which
propels the sperm toward the oocyte in
the uterine tube.
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Ribosome structure and function?
are sites of protein synthesis. These tiny
organelles are packages of ribosomal
RNA (rRNA) and many ribosomal
proteins. Ribosomes are so named
because of their high content of ribonucleic
acid. Structurally, a ribosome consists of
two subunits, one about half the size of the
other. The two subunits are made
separately in the nucleolus, a spherical
body inside the nucleus. Once produced,
they exit the nucleus and join together in
the cytosol where they become functional.
Functions
1. Ribosomes associated with
endoplasmic reticulum synthesize proteins
destined for insertion in the plasma
membrane or secretion from the cell. 2.
Free ribosomes syntendoplasmichesize
proteins used in the cytosol.
Rough Endoplasmic Reticulum
is a network of membranes in the form of
flattened sacs or tubules. The ER extends
from the nuclear envelope (membrane
around the nucleus), to which it is
connected, throughout the cytoplasm. The
ER is so extensive that it constitutes more
than half of the membranous surfaces
within the cytoplasm of most cells.
Rough Endoplasmic Reticulum function?
has two parts to it. The Rough ER has
many Ribosomes lining its inside and
creates proteins for the cell which are
either used or sent to the Golgi Apparatus
for transportation. Proteins that are
created in the Rough ER have a higher
chance of being secreted.
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Smooth ER
Anatomy Exam 1: Cells and Mitosis flashcards | Quizlet
extends from the rough ER to form a
network of membrane tubules. Unlike
rough ER, smooth ER does not have
ribosomes on the outer surfaces of its
membrane. However, smooth ER contains
unique enzymes that make it functionally
more diverse than rough ER. Because it
lacks ribosomes, smooth ER does not
synthesize proteins, but it does synthesize
fatty acids and steroids, such as estrogens
and testosterone. In liver cells, enzymes of
the smooth ER help release glucose into
the bloodstream and inactivate or detoxify
lipid-soluble drugs or potentially harmful
substances, such as alcohol, pesticides,
and carcinogens (cancer-causing agents).
In liver, kidney, and intestinal cells a
smooth ER enzyme removes the
phosphate group from glucose-6phosphate, which allows the "free" glucose
to enter the bloodstream. In muscle cells,
the calcium ions (Ca2+) that trigger
contraction are released from the
sarcoplasmic reticulum, a form of smooth
ER. The smooth ER's job is to remove
toxins from the system, which is why a
high concentration of Smooth ER is found
in the liver.
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The Goli Complex
Most of the proteins synthesized by
ribosomes attached to rough ER are
ultimately transported to other regions of
the cell. The first step in the transport
pathway is through an organelle called the
Golgi complex. It consists of 3 to 20
cisternae, small, flattened membranous
sacs with bulging edges that resemble a
stack of pita bread. The cisternae are
often curved, giving the Golgi complex a
cuplike shape. Most cells have several
Golgi complexes, and Golgi complexes
are more extensive in protein-secreting
cells, a clue to the organelle's role in the
cell.
Function of Golgi Body?
Functions
1. Modifies, sorts, packages, and
transports proteins received from the
rough ER.
2. Forms secretory vesicles that discharge
processed proteins via exocytosis into
extracellular fluid; forms membrane
vesicles that ferry new molecules to the
plasma membrane; forms transport
vesicles that carry molecules to other
organelles, such as lysosomes.
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Lysosomes
Anatomy Exam 1: Cells and Mitosis flashcards | Quizlet
are membrane-enclosed vesicles that form
from the Golgi complex. Inside can be as
many as 60 kinds of powerful digestive
enzymes that are capable of breaking
down a wide variety of molecules.
Lysosomes fuse with vesicles formed
during endocytosis and the lysosomal
enzymes break down the contents of the
vesicles. Proteins in the lysosomal
membrane allow the final products of
digestion, such as sugars, fatty acids, and
amino acids, to be transported into the
cytosol. In a similar way, lysosomes in
phagocytes can break down and destroy
microbes, such as bacteria and viruses.
Lysosomes
Lysosomes contain several kinds of
powerful digestive enzymes.
Functions
1. Digest substances that enter a cell via
endocytosis and transport final products of
digestion into cytosol.
2. Carry out autophagy, the digestion of
worn-out organelles.
3. Carry out autolysis, the digestion of
entire cell.
4.
Carry out extracellular digestion.
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Peroxisomes
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Another group of organelles similar in
structure to lysosomes, but smaller, are
called peroxisomes. Peroxisomes, also
called microbodies, contain several
enzymes called oxidases that can oxidize
(remove hydrogen atoms) from various
organic substances. For example, amino
acids and fatty acids are oxidized in
peroxisomes as part of normal
metabolism. In addition, enzymes in
peroxisomes oxidize toxic substances,
such as alcohol. Thus, peroxisomes are
very abundant in the liver, where
detoxification of alcohol and other
damaging substances takes place. A
byproduct of the oxidation reactions is
hydrogen peroxide (H2O2), a potentially
toxic compound. However, peroxisomes
also contain an enzyme called catalase,
which decomposes H2O2. Because the
generation and degradation of H2O2
occur within the same organelle,
peroxisomes protect other parts of the cell
from the toxic effects of H2O2. Like
mitochondria, peroxisomes self replicate.
One way that new peroxisomes may form
is by budding off from preexisting ones by
enlarging and dividing.
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Proteasomes
Although lysosomes degrade proteins
delivered to them in vesicles, cytosolic
proteins also require disposal at certain
times in the life of a cell. Continuous
destruction of unneeded, damaged, or
faulty proteins is the function of tiny barrelshaped structures called proteasomes. For
example, proteins that are part of
metabolic pathways are degraded after
they have accomplished their function.
Such protein destruction halts the pathway
once the appropriate response has been
achieved. A typical body cell contains
many thousands of proteasomes, in both
the cytosol and the nucleus. They are far
too small to discern under the light
microscope and do not show up well in
electron micrographs. Proteasomes were
so named because they contain numerous
proteases, enzymes that cut proteins into
small peptides. Once the enzymes of a
proteasome have chopped up a protein
into smaller chunks, other enzymes then
break down the peptides into amino acids,
which can be recycled into new proteins.
Mitochondria
Within mitochondria, chemical reactions of
aerobic cellular respiration generate ATP.
Function: Generate ATP through reactions
of aerobic cellular respiration.
More on mitochondria
mitochondria self-replicate, a process that
occurs during times of increased cellular
energy demand or before cell division.
Mitochondria even have their own DNA,
in the form of multiple copies of a circular
DNA molecule that contains 37 genes.
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nuclear envelope
A double membrane called the nuclear
envelope separates the nucleus from the
cytoplasm. Both layers of the nuclear
envelope are lipid bilayers similar to the
plasma membrane. Serves as the physical
barrier, separating the contents of the
nucleus (DNA in particular) from the
cytoso. Many nuclear pores are inserted in
the nuclear envelope, which facilitate and
regulate the exchange of materials
(proteins such as transcription factors, and
RNA) between the nucleus and the
cytoplasm.
Nucleolus
Inside the nucleus are one or more
spherical bodies called nucleoli (singular is
nucleolus) that function in producing
ribosomes. Each nucleolus is simply a
cluster of protein, DNA, and RNA, that is
not enclosed by a membrane. Nucleoli are
the sites of rRNA synthesis and the
assembly of rRNA and proteins into
ribosomal subunits. Nucleoli are quite
prominent in cells that synthesize large
amounts of protein, such as muscle and
liver cells. Nucleoli disperse and disappear
during cell division and reorganize once
new cells are formed.
Chromatin
Within the nucleus are most of the cell's
hereditary units, called genes, which
control cellular structure and direct cellular
activities. Genes are arranged along
chromosomes. Human somatic (body)
cells have 46 chromosomes, 23 inherited
from each parent. Each chromosome is a
long molecule of DNA that is coiled
together with several proteins. This
complex of DNA, proteins, and some
RNA is called chromatin. The total genetic
information carried in a cell or an organism
is its genome.
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Function of chromatin
The functions of chromatin are to package
DNA into a smaller volume to fit in the
cell, to strengthen the DNA to allow
mitosis and meiosis, and to control gene
expression and DNA replication. Changes
in chromatin structure are affected by
chemical modifications of histone proteins,
such as methylation and acetylation, and
by other DNA-binding proteins.
Nucleoplasm
Similar to the cytoplasm of a cell, the
nucleus contains nucleoplasm or nuclear
sap. The nucleoplasm is one of the types
of protoplasm, and it is enveloped by the
nuclear membrane or nuclear envelope.
The nucleoplasm is a highly viscous liquid
that surrounds the chromosomes and
nucleoli.
Somatic Cell Division
The cell cycle is an orderly sequence of
events by which a somatic cell duplicates
its contents and divides in two. Human
cells, such as those in the brain, stomach,
and kidneys, contain 23 pairs of
chromosomes, for a total of 46. One
member of each pair is inherited from each
parent. The two chromosomes that make
up each pair are called homologous
chromosomes or homologs; they contain
similar genes arranged in the same (or
almost the same) order. When examined
under a light microscope, homologous
chromosomes generally look very similar.
The exception to this rule is one pair of
chromosomes called the sex
chromosomes, designated X and Y.
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