Histology Chapters 2 & 3 Flashcards
What is the plasma membrane composed of?
phospholipids, cholesterol, proteins, and chains of oligosaccharides
What is the function of the plasma membrane? (3)
Site where materials are exchanged between the cell and its environment; regulates the ion concentration of the cytoplasm; also recognition, regulatory, and interaction functions.
what is the thickness of the plasma membrane?
7.5 to 10 nm thick (EM)
what is the structure of the plasma membrane?
Trilaminar (EM); fluid mosaic model
Where does osmium tetroxide deposit on the plasma membrane?
On the outer hydrophilic heads away from the hydrophobic tails.
What are the three kind of proteins in the plasma membrane?
Integral, transmembrane, and peripheral
What are structures that are always on the outside of the cell attached to the plasma membrane?
Glycoproteins
What are the three kinds of Endocytosis?
Phagocytosis, pinocytosis, and receptor-mediated endocytosis
Define phagocytosis.
“Cell-eating”; phagosome; then fuses with lysosome
Define pinocytosis.
Also called fluid-phase endocytosis is “cell-drinking”; pinocytotic vesicle; then fuses with lysosomes.
Define receptor-mediated endocytosis.
Binding of the ligand to a receptor causes coated pits made of clathrin to form; pinches off to form a coated vesicle; fuses with endosomal compartment to form endosomes.
Define exocytosis.
Release of material across plasma membrane into the extra cellular space; involves vesicle fusing with plasma membrane and releasing its contents.
What is the function of a lysosome?
Sites of intracellular digestion and turnover of cellular components.
What is the size of a lysosome?
0.05 - 0.5 micrometers
What is the structure of a lysosome?
Membrane bound vesicles that contain about 40 different hydrolytic enzymes.
what is the relative size of an lysosome versus a RBC?
about 1/16th of the size
What is the function of a ribosome?
Protein synthesis
What is the size of a ribosome?
20nm x 30nm
What is the structure of a ribosome?
Composed of two different sized subunits; the subunits are composed of rRNA and proteins; can be found free within the cytoplasm or attached to membrane of the endoplasmic reticulum.
What is the structure of the endoplasmic reticulum?
Network of intercommunicating channels and sacs of membranes which enclose a space called a cisterna.
What defines rough endoplasmic reticulum (RER), and what does the RER do?
There are ribosomes on the cytosolic side of the membrane; produces proteins for secretion.
What defines the smooth endoplasmic reticulum (SER); and what does the SER to?
Regions of ER without ribosomes; cisternae are much more tubular; important in the production of phospholipids; abundant in cells that synthesize steroid hormones.
What are two types of human organ cells that have an abundance of smooth ER?
neurons and liver cells
What is the function of the golgi apparatus?
Completes post-translational modifications, packages, and sorts proteins synthesized in the RER.
What is the Structure of the golgi apparatus?
Composed of smooth membranous saccules; has a cis (entry) face and a trans (exit) face.
What is the function of the mitochondria?
Membrane-enclosed organelles with enzyme arrays specialized for aerobic respiration and production of adenosine triphosphate (ATP).
What is the size of a mitochondria?
0.5-1.0 micrometer in diameter and 5-10 micrometers in length
What is the structure of mitochondria?
Two membranes (inner and outer) and two compartments (matrix and intermembrane space); inner membrane folded to form cristae which project into matrix.
Give an example of cells that would have a lot of mitochondria due to their high energy needs.
Muscle, kidney, liver
What is the function of secretory vesicles (granules)?
Formed at the golgi apparatus; store product until it is released via exocytosis
What is the structure of the secretory vesicle?
Secretory product surrounded by membrane.
What is the function of a proteasome?
To degrade denatured and nonfunctional polypeptides.
What is the structure of a proteasome?
Cytoplasmic protein (no membrane); cylindrical structure made of four stacked rings.
What is the function of peroxisomes?
Oxidizes various potentially toxic molecules as well as prescription drugs. These are very important in pharmaceutical activities.
What is the size of a peroxisome?
0.5 micrometer in diameter
What is the structure of a peroxisome?
Spherical membrane-limited organelle
In what human tissue cells are peroxisomes found in great numbers?
Liver cells
What are microtubules and where are they found?
They are fine tubular structures found in cytoplasmic matrix, centrioles, basal bodies, cilia, and flagella.
What is the function of microtubules?
Formation and maintenance of cell shape; cellular transport of organelles and vesicles; create repeated beating motion.
What is the size of a microtubule? Outer diameter and wall thickness.
Outer diameter of 24nm and dense wall 5nm thick
Is a microtubule hollow?
Yes the lumen is hollow.
What is the length of a microtubule?
Variable, can be many micrometers in length.
What is the structure of a microtubule?
Composed of alpha and beta tubulin molecules; organize to form 13 parallel protofilaments.
Microtubules are very important in what to the cell?
Cell shape
What is an axoneme?
This is the core structure in cilia and flagella microtubule assembly.
What is the structure of microtubules?
Assembly of microtubules in a 9+2 pattern.
How are the 9 axoneme units assembled in a microtubule?
Microtubule doublets that are connected in the pattern; beta, alpha, dynein, beta, alpha, dynein…
What causes the conformational change in the axoneme?
ATP-dependent interaction cause conformational change - get repeated beating movement.
What are microfilaments also called?
Actin filaments
What is the function of microfilaments?
Allow for contractile activity within cells, including cell shape changes for endocytosis, exocytosis, and cell locomotion, moving cytoplasmic components, and cleavage during mitosis.
What is the size of microfilaments?
5-9 nm
What is the structure of microfilaments?
Composed of globular subunits organized into a double-stranded helix.
What to intermediate filaments do?
They are very stable so the provide mechanical strength and stability.
What is the size of intermediate filaments?
10-12nm in diameter
What is the structure of intermediate filaments?
Protein subunits different in different cell types; rod-like subunits that organize into a cable like structure.
What do intermediate filaments tie into that connect cells?
Desmosomes
What are three examples of inclusions?
Lipid droplets, glycogen granules, pigment deposits
Are inclusions considered organelles?
No
What are inclusions in the cell?
Cytoplasmic structures or deposits composed mainly of accumulated metabolites or other substances.
What are the three main components of the nucleus?
Nuclear envelope, chromatin, nucleolus.
What is the nuclear envelope?
2 parallel unit membranes separated by a narrow space; at sites where inner and outer membranes of the nuclear envelope fuse, nuclear pore complexes form; where regulation of the transport between the nucleus and cytoplasm takes place.
What are the two types of chromatin?
Heterochromatin and euchromatin
What is chromatin?
The chromosomal material in a largely uncoiled state.
Define heterochromatin.
Course granules in EM and basophilic clumps in light microscopy.
Define euchromatin.
Less coiled; fine granules in EM and lightly basophilic areas in light microscopy.
A very active cell would have much of what kind of chromatin?
Euchromatin, as this is the uncoiled active parts of DNA.
What is the nucleolus?
Spherical, highly basophilic structure present in nuclei of cells active in protein synthesis; lots of rRNA in this location.
What can be seen microscopically during prophase?
A nucleus with dispersed chromosomes, mitotic spindle is developing.
What can be seen microscopically during metaphase?
Chromosomes aligned on an equatorial plate, and visible mitotic spindle.
What can be seen microscopically during anaphase?
Sister chromatids being pulled apart and visible mitotic spindle.
What can be seen during telophase?
Cytokinesis occurring, reforming of the nuclear envelope, and a cleavage furrow.
Give a brief summary of mitosis.
Interphase > Prophase (chromosomes condense) > Metaphase (chromosomes line up single file) > Anaphase/Telophase (genetically identical daughter cells produced)
What does mitosis produce?
Two identical daughter cells.
What happens in late interphase before meiosis?
Synapsis and crossing over begin.
What happens in prophase one of meiosis?
Crossing over continues. Paired chromosomes condense.
What happens in Metaphase 1 of Meiosis?
Homologous chromosomes line up double file.
What happens in anaphase 1/telophase 1 of meiosis?
Homologs separate into haploid daughter cells; sister chromatids remain joined.
What happens in Metaphase 2 of meiosis?
Chromosomes line up single file in haploid cells.
What happens in anaphase 2/telophase 2 of meiosis?
Sister chromatids separate into nonidentical haploid cells.
What is the product of Meiosis 2?
Meiosis produces haploid cells with new genetic combinations.
What is apoptosis?
The process of cell suicide or programmed cell death; leads to the production of small membrane-enclosed apoptotic bodies which undergo phagocytosis by neighboring cells.
What happens to the cell during necrosis?
Cell rupture
Are necrosis and apoptosis the same thing?
No
