Histo chap 2&3 Flashcards
- cells produced by the first zygotic cellular divisions
- give rise to all tissue types of the fetus
Blastomeres
- Explanted to tissue culture cells
of the inner cell mass
Embryonic Stem Cells
- cells predominantly express sets of
genes that mediate specific cytoplasmic activities, becoming efficiently organized in tissues with specialized functions and usually changing their shape accordingly
Differentiation
-It consists of phospholipids, cholesterol, and proteins, with oligosaccharide chains
-It functions as a selective barrier regulating the passage of materials into and out of the cell
PLASMA MEMBRANE
- continuum that exists between the interior of the cell and extracellular macromolecules.
Integrins
are major constituents of membranes
Proteins
- incorporated directly within the lipid bilayer
- extracted only by using detergents to disrupt the lipids
Integral proteins
- bound to one of the two membrane surfaces
- can be extracted from cell membranes with salt solution
Peripheral proteins
- polypeptide chains of many integral proteins span the membrane
Multipass proteins
- transports small, nonpolar molecules directly
through the lipid bilayer
Diffusion
multipass proteins forming transmembrane pores through which ions or small molecules pass selectively.
Channels
where water molecules cross
Aquaporins
- transmembrane proteins that bind small molecules and translocate them across the membrane via
conformational changes
Carriers
substances are brought into the cell
Endocytosis
- ingestion of particles such
as bacteria or dead cell remnants
Phagocytosis or cell eating
- involves smaller invaginations of the cell membrane which fuse and entrap
extracellular fluid and its dissolved content
Pinocytosis or cell drinking
- includes membrane proteins called receptors that bind specific molecules
(ligands).
Receptor-mediated endocytosis
- movement of large molecules from inside to outside the cell
- triggered in many cells by a transient increase in cytosolic Ca2+
Exocytosis
used for products that are
released from cells continuously
Constitutive secretion -
occurs in response to signals
coming to the cells, such as the release of digestive enzymes from pancreatic cells in response to specific stimuli.
Regulated secretion
process of membrane movement
and recycling
Membrane trafficking
couple the cells and allow exchange of
ions and small molecules
Gap Junctions
signal molecules (hormones) are
carried in the blood from their sources to target cells throughout the body
Endocrine signaling
chemical ligand diffuses in extracellular fluid but is rapidly metabolized so that its effect is only local on target cells near its source
Paracrine signaling
-a special kind of paracrine interaction,
neurotransmitters act on adjacent cells
through special contact areas called synapses
Synaptic signaling
signals bind receptors on the same cells that produced the messenger molecule
Autocrine signaling
-important in early embryonic
-bind surface receptors of the target cell when the two cells make direct physical contact
Juxtacrine signaling
ligand binding induces catalytic activity in
associated peripheral protein
Enzymatic receptors
open associated channels upon ligand binding to promote transfer of molecules or ions across the membrane
Channel-linked receptors
upon ligand binding stimulate associated Gproteins which then bind the guanine nucleotide GTP and are released to activate other cytoplasmic proteins.
G-protein-coupled receptors
assemble polypeptides from amino acids on molecules of
transfer RNA (tRNA) in a sequence specified by mRNA
Ribosomes
Prominent in cells specialized for protein secretion, such
as pancreatic acinar cells
Rough Endoplasmic Reticulum
-lacking polyribosomes
-not basophilic
-its cisternae are more tubular or saclike
Smooth Endoplasmic Reticulum
- completes posttranslational modifications of proteins produced in the RER and then packages and addresses these proteins to their proper destinations
Golgi apparatus
- sites of intracellular digestion and turnover of cellular components
Lysosomes
-excess organelles or large aggregates of
nonfunctional macromolecules in cytoplasm are degraded
Autophagy
very small abundant protein complexes that are not associated with membrane, each approximately the size of the small ribosomal subunit
-degrade denatured or otherwise nonfunctional polypeptide
- lysosomes digest organelles or membranes by autophagy, proteasomes deal primarily with free proteins
as individual molecule
Proteasomes
- membrane-enclosed organelles with arrays of enzymes specialized for aerobic respiration and production of adenosine triphosphate (ATP)
Mitochondria
-rapid cell death
Apoptosis
-spherical organelles enclosed by a single membrane and named for their enzymes producing and degrading hydrogen peroxide, H2O2
Peroxisomes
substrates by removing hydrogen atoms that are transferred to molecular oxygen (O2), producing H2O2
Oxidases
immediately break down H2O2 , which is
potentially damaging to the cell
Catalase
-fine tubular structures
Microtubules
-larger, more stable arrays
Axonemes
Composed of actin subunits and allow motility and most contractile activity in cells, using reversible assembly of the actin filaments and interactions between these filaments and associated myosin family proteins
Microfilaments (Actin Filaments)
networks of actin filaments and as free G-actin
subunits near the cell membrane
Cell cortex
Chap 3
is the command center of the
cell, that contains the code of all cell
enzymes and proteins.
Nucleus
Chap 3
It forms a selectively permeable barrier
between the nuclear and cytoplasmic
compartments
Nuclear Envelope
Chap 3
Nuclear Envelope:
It has two concentric membranes separated
by a narrow (30-50nm) called
perinuclear space.
Chap 3
Nuclear Envelope
Associated with the inner nuclear
membrane is a highly organized proteins
called the __________________ which stabilizes
the nuclear envelope
Nuclear lamina
Chap 3
display eightfold symmetry
around a lumen
Nucleoporins
Chap 3
______________consists of DNA and all
associated proteins involved in the
organization and function of DNA
Two sister chromatids are help
together by complexes of cohesion
proteins
Chromatin
Chap 3
The structural unit of DNA and histones
is _________________
nucleosome
Chap 3
– is visible as finely granular
material in the microscope and as stained
basophilic areas in the light microscope
(loosely packed)
Euchromatin
Chap 3
– (heteros other + chroma color) – appears as a coarse, electrondense material in the electron microscope and as intensely basophilic clumps in the
light microscope (densely packed)
Heterochromatin
Chap 3
is generally similar in all cell types and contains mainly repetitive, gene poor DNA sequences
including large chromosomal regions called
the centromeres and telomeres
Constitutive Heterochromatin
Chap 3
– contains other regions of DNA with genes where
transcription is variably inactivated in
different cells by epigenetic mechanisms
and can undergo reversible transitions from
compact, transcriptionally silent states.
Facultative Heterochromatin
Chap 3
is generally spherical, highly
basophilic subdomains of nuclei in cells
actively engaged in protein synthesis.
Nucleolus
Chap 3
The regular sequence of events that
produce a new cells is termed
Cell Cycle
Chap 3
The cell cycle has four distinct phases:
- Mitosis
- G1 Phase
- S Phase
- G2 Phase
Chap 3
the gap between mitosis and
the beginning of DNA Replication
G1 phase
Chap 3
The period of DNA synthesis
S phase
Chap 3
the gap between the DNA
Duplication and the next mitosis
G2 phase
Chap 3
Produces two diploid cells
Mitosis
Chap 3
- The nucleolus disappears and the
replicated chromatin condenses like a
threadlike chromosomes each consisting of
duplicate sister chromatids joined at the
centromere - The two centromeres with their nowduplicated centrioles separate and migrate
to opposite poles of the cell and organize
the microtubules for mitotic spindle - Late in prophase, lamins and inner nuclear
membrane are phosphorylated, causing the
nuclear lamina and nuclear pore complexes to disassemble and disperse in cytoplasmic
membrane vesicles
Prophase
Chap 3
The chromosomes condenses further and
large protein complexes called the
Kinetochore (kinetos, moving)
The cell is now more spherical and
microtubules move the chromosomes into
alignment at the equatorial plate
Metaphase
Chap 3
- Sister chromatids are called (chromosomes
themselves) - Separate and move toward opposite spindle
poles by combination of microtubule motor
proteins and dynamic changes in the length
of the microtubules as the spindle pole
moves farther apart.
Anaphase
Chap 3
- The two sets of chromosomes are at the
spindle poles and begin reverting to their
uncondensed state - Microtubules of the spindle depolymerize
and the nuclear envelope begins to
reassemble around each set of daughter
chromosomes - A belt like contractile ring of actin filaments
associate with myosins and develop in the
cortical cytoplasm at the cell’s equator
Telophase
Chap 3
- Constriction of this ring produces a
cleavage furrow and progresses until the
cytoplasm and its organelles are divided
into two daughter cells, each with one
nucleus.
▪ The cell turnover rate is rapid in the
epithelium lining the digestive tract and
uterus or covering the skin.
Cytokinesis
Chap 3
▪ Is a specialized process involving two
unique and closely associated cell division
that occurs only in the cells that will form
sperm and egg cells.
▪ Produces four haploid cells
Meiosis
