Chapter 3: Cells and Tissues Flashcards
What form is DNA in when a cell is not dividing?
Chromatin
What form is DNA in when a cell is dividing?
Chromosomes
What is the name of proteins that chromatin is wound around?
histones
What are the three types of cell junctions?
Tight junctions, desmosomes, gap junctions
What are tight junctions?
impermeable junctions that encircle the cells and bind them together into leakproof sheets
What is the function of tight junctions?
to prevent substances from passing through the extracellular space between cells
What is the function of desmosomes?
They prevent cells subjected to mechanical stress (such as heart muscle cells and skin cells) from being pulled apart.
What is the structure of desmosomes junctions?
thickenings of adjacent plasma membranes (plaques) that are connected by fine protein filaments (made of cadherins). Thicker protein filaments extend from the plaques inside the cells to the plaques on the cells’ opposite sides
What is the function of gap junctions?
to allow communication
What is the structure of gap junctions?
hollow cylinders composed of proteins (called connexons) that span the entire width of the neighboring membranes (which are therefore called transmembrane proteins)
What type of molecules cannot move across gap junctions?
macromolecules
What are the three alternate types for the cell membrane junctions?
impermeable junctions, anchoring junction, communicating/transmembrane junctions
What are the three major components of cytoplasm?
cytosol, inclusions, organelles
What is the cytosol?
It’s a semi-transparent fluid that suspends the other elements (organelles, particles)
What is dissolved in the cytosol?
nutrients and other solutes
What are inclusions?
Inclusions are non-living chemical substances that may or may not be present, depending on the specific cell type. Most are stored nutrients or cell products floating in the cytosol.
What are examples of inclusions? (4)
lipid droplets, glycogen granules, pigments, mucus
What are organelles?
specialized cellular compartments that are the metabolic machinery of the cell
What are the protrusions within the second plasma membrane of mitochondria called?
cristae
What is the difference between ribosomes in the cytoplasm and the ribosomes stuck to the RER?
The ribosomes stuck to the RER produces proteins that functions outside of the cell
What is the structure of peroxisomes?
Membranous sacs of oxidase and catalase enzymes.
What is the function of peroxisomes?
The enzymes detoxify a number of toxic substances such as free radicals. The most important enzyme, catalase, breaks down
hydrogen peroxide
In what conditions do lysosomes (sacs that contain very powerful enzymes) burst?
when the cell is injured or deprived of oxygen and when excessive amounts of vitamin A are present
What is the structure of microtubules?
Cylindrical structures made of tubulin proteins.
What is the function of microtubules?
Support the cell and give it shape. Involved in intracellular and cellular movements. Form centrioles and cilia and flagella, if present