Cell Structure/Mitosis phases Flashcards
Fluid bi-layer of lipid molecules with protein molecules dispersed in it.
The lipid bilayer is basically comprised of phospholipids with a polar “head” that is charged and hydrophilic (likes water) and an uncharged, nonpolar “tail” that is hydrophobic (hates water)
Plasma membrane
minute fingerlike extensions of the plasma membrane.
Increase the surface area of the plasma membrane.
Found on the surface of absorptive cells such as intestines and kidney tubule cells
Microvilli
a series of integral protein molecules in the plasma membranes of adjacent cells fused together.
Form an impermeable junction that encircles the cell.
Help prevent molecules from passing through the extracellular space between adjacent cells
Tight Junctions
are anchoring junctions.
Prevents adjoining cells from separating
Desmosomes
a communicating junction allowing chemical substances to pass between adjacent cells
Gap junctions
the cellular material between the plasma membrane and the nucleus. Most cellular activities occurs here.
Cytoplasm
Three major elements comprise the cytoplasm
cytosol, cytoplasmic organelles, inclusions
the fluid in which the other cytoplasmic elements are suspended
cytosol
the metabolic machinery of the cell.
cytoplasmic organelles
chemical substances that may or may not be present, depending on the cell type.
Ex. stored nutrients.
inclusions
specialized cellular compartments, each performing its own job to maintain the life of the cell
Cytoplasmic Organelles
threadlike or sausage-shaped membranous organelle.
The “powerhouse” of the cell, providing the cell with most of its ATP supply
Mitochondria
small, dark-staining granules composed of proteins and a variety of RNA called ribosomal RNA. Sites of protein synthesis
Ribosomes
an extensive system of interconnected tubes and parallel membranes enclosing fluid-filled cavities (cisternae).
It coils and twists through the cytosol.
Endoplasmic Reticulum (ER)
Two varieties of Endoplasmic Reticulum (ER)
Rough endoplasmic reticulum (Rough ER)
Smooth endoplasmic reticulum (smooth ER)
External surface contains ribosomes.
ocated in most secretory cells, antibody-producing plasma cells, and liver cells producing most blood proteins.
It’s also the cell’s “membrane factory”.
Integral proteins and phospholipids that form part of all cellular membranes are manufactured here
Rough endoplasmic reticulum
A continuation of the rough ER consisting of tubules arranged in a looping network.
Its enzymes catalyze reactions involved in the following processes:
a. Lipid metabolism, cholesterol synthesis, and synthesis of lipid components of lipidproteins.
b. Synthesis of steroid-based hormones such as sex hormones.
c. Absorption, synthesis, and transport of fats.
d. Detoxification of drugs, certain pesticides, and carcinogens.
e. Breakdown of stored glycogen to from free glucose.
Smooth endoplasmic reticulum
Consists of stacked and flattened membranous sacs associated with swarms of tiny membranous vesicles.
Principal “traffic director” for cellular proteins.
Major function is to modify, concentrate, and package the proteins and lipids made at the rough ER
Golgi apparatus
contain digestive enzymes. Abundant in phagocytes (cells that dispose of invading bacteria and cell debris).
Function as cells’ “demolition crew” by:
Digesting particles taken in by endocytosis.
Degrading worn-out or nonfunctional organelles.
Performing metabolic functions.
Breaking down non-useful tissues.
Break down bone to release calcium ions into the blood.
Lysosomes, if damaged, will self-digest itself by a process called autolysis
Lysosomes
membranous sacs containing a variety of powerful enzymes
Peroxisomes
Hollow tubes made of spherical protein subunits called tubulins.
Determines the overall shape of the cell along with the distribution of organelles.
Mitochondria, lysosomes, and secretory granules attached to microtubules.
Microtubules
the thinnest elements are strands of the protein actin.
Each cell has a unique arrangement. Attached to the cytoplasmic side of the cell’s plasma membrane which gives strength to the cell’s surface.
Involved in cell motility or changes in cell shape.
Funtions: Actin with myosin help contract muscles and forms the cleavage furrow that pinches a cell in two during cell division.
Also responsible for the crawling movement of amoeboid motion, and for the membrane changes that accompany endocytosis and exocytosis
Microfilaments
tough, insoluble protein fibers that have a diameter between those of microfilaments and microtubules.
Most stable and permanent element of the cytoskeleton.
High tensile strength and act as internal guy wires to resist pulling forces exerted on the cell
Intermediate filaments
a region near the nucleus where microtubules are anchored.
Act as a microtubule organizing center and has a granular-looking matrix which contains centrioles
Centrosome
small, barrel-shaped organelles oriented at right angles to each other.
This matrix is known for its generation of microtubules and its role of organizing the mitotic spindle in cell division.
Centrioles also form the bases of cilia and flagella.
Centrioles
whip-like motile cellular extensions.
Usually they are in large numbers located on exposed surfaces of certain cells.
Function in moving substances in one direction across cell surfaces.
Line the respiratory tract and propel mucus with dust and bacteria out of the lungs.
Propels other substances across the cell
Cilia
these are longer than cilia.
Ex. sperm, which has a tail which propels the cell. Propels the cell itself
Flagella
The control center of the cell.
Contains genes and the instructions needed to build nearly all the body’s proteins.
It also dictates the kinds and amounts of proteins to be synthesized at any one time in response to signals acting on the cell.
Nucleus
three regions of the nucleus
nuclear envelope, nucleoli, and chromatin.
A double membrane barrier which surrounds the nucleus
Nuclear Envelope
spherical bodies within the nucleus.
Associated with nucleolar organizer regions which contain DNA which issues genetic instructions for synthesizing ribosomal RNA (rRNA).
Nucleoli
a system of bumpy threads weaving their way through the nucleoplasm (jellylike fluid where nuclear elements are suspended).
Composed of relatively equal amounts DNA and globular histone proteins
Chromatin
series of changes a cell goes through from the time it’s formed until it reproduces
cell life cycle
Two major periods of the cell life cycle
interphase, cell division (mitosis)
the cell grows and carries out its usual activities
interphase
the cell continues to carry out all its normal functions/activities and rests from dividing
Interphase
Interphase Divides into three subphases
G1, S, and G2
cell is metabolically active (making proteins and growing quickly) but the timeframe for this phase varies
G1
DNA replicates itself, making sure the two new cells will be identical to the original
S
Enzymes and other proteins needed for division are made and moved to their proper sites and the phase is short; centriole replication is done.
G2
this must be done before cell division
DNA Replication
essential for body growth and tissue repair
Cell division
Involves division of the nucleus
mitosis
division of the cytoplasm
cytokinesis
series of events which parcels out replicated DNA to two daughter cells
mitosis
what are the four phases of mitosis
prophase, metaphase, anaphase, and telophase
(1st phase) Early: microtubule arrays (asters) extend from the centrosome matrix around the centrioles.
The chromatin threads coil and condense forming chromosomes (these are already replicated and are actually called chromatids and are held together by a centromere).
As the chromosomes appear, the nucleoli disappear and the cytoskeletal microtubules disassemble.
The centriole pairs separate and act as focal points for growth of a new set of microtubules called the mitotic spindle.
As the spindle lengthens, they push the centrioles farther and farther apart, propelling them toward opposite ends of the cell.
prophase
nuclear envelope fragments, and the spindle now occupies the center of the cell and interacts with the chromosomes.
Part of the growing spindle attaches to a kinetochore (a protein-DNA complex) at each centromere.
Eventually, the chromosomes comes to the middle of the cell.
late prophase
Chromosomes cluster in the middle of the cell and their centromeres are aligned at the exact center of the spindle
Metaphase
begins as the centromeres split and each chromatid becomes a chromosome in its own right.
The kinetochore fibers rapidly disassemble at their ends and gradually pull each chromosome toward the pole it’s facing.
The polar microtubules slide past each other and lengthen and move toward the two poles causing the cell to elongate.
This phase is easy to recognize because the chromosomes look “V shaped”.
This is the shortest phase of mitosis
Anaphase
starts when the chromosomes stop moving.
identical sets of chromosomes, now at opposite poles, uncoil and resume their threadlike extended-chromatin form.
A new nuclear envelope, re-forms around each chromatin mass.
Nucleoli reappear within the nuclei and the spindle breaks down and disappears
Telophase and Cytokinesis
Completes the division of the cell into two daughter cells
Cytokinesis
begins during late anaphase and continues through and beyond telophase
Cytokinesis
begins during late anaphase and occurs after mitosis ends.
The plasma membrane over the center of the cell is drawn inward to form a cleavage furrow.
The furrow deepens until the cytoplasm is pinched in two, producing two daughter cells
Cytokinesis
