5 Written Questions

1. are hollow cylinders composed of proteins that span the entire width of the abutting membranes.
2. is so called because it is studded with ribosomes. er can be thought of as the cell's membrane factory. proteins made on its ribosomes migrate into the tubules of the rougher, where they fold into their functional threedimensional shapes and then are dispatched to other areas of the cell.
3. some cells have projuction called cilia, whiplike cellular extensions that move substances along the cell surface.
4. is the semitransparent fluid that suspends the other elements.
5. are formed when golgi apparatus, the sacs swell. then their swollen ends, filled with protein, pinch off. which travel to the plasma membrane.

5 Matching Questions

1. ribosomes
2. gap junctions
3. tight junctions
4. desmosomes
5. nuclear membrane

1. a is a double membrane between the two membranes is a fluid-filled "moat" or space. encloses a jellylike fliud called nucleoplasm.
2. b are impermeable junctions that bind cells together into leakproof sheets that prevent substances from passing throught the extracellular space between cells. these junctions keep digestive enzymes from seeping into the bloodstream.
3. c are tiny, bilobed, dark bodies made of proteins and one variety of RNA, called ribosomal RNA. ribosomes are the actual sites of protein synthesis in the cell.
4. d commonly seen in the heart and between embryonic cells, function mainly to allow communication. neighboring cells are connected by connexons.
5. e are anchoring junctions that prevent cells subjected to mechanical stress from being pulled apart. such as skin cells. these junctions are buttonlike thickenings of adjacent plasma membranes (plaques).

5 Multiple Choice Questions

1. vary structurally depending on their roles. tight junctions, desmosomes, gap junctions.
   1. inclusions
   2. gap junctions
   3. membrane junctions
   4. tight junctions
2. is a fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment.
   1. lysosomes
   2. nuclear membrane
   3. plasma membrane
   4. flagella
3. are chemical substances that may or may not be present, depending on the specific cell type. they include the lipid droplets common in fat cells, glycogen gtanules abundant in liver and muscle cells, pigments such as melanin in skin and hair cells, mucus and other secretory products, and various kinds of crystals.
   1. connexons
   2. nucleus
   3. nucleoli
   4. inclusions
4. are membranous sacs containing powerful oxidase enzymes that use molecular oxygen to detoxify a number of harmful or poisonous substances, including alcohol and formaldehyde, but most important function is to "disarm" dangerous free radicals.
   1. lysosomes
   2. chromosomes
   3. desmosomes
   4. peroxisomes
5. "network within the cytoplasm" ER is a system of fluid-filled cisterns that coil and twist through the cytoplasm. tubeles, or canals.
   1. plasma membrane
   2. cytoplasm
   3. endoplasmic reticulum
   4. microtubules

5 True/False Questions

1. mitochondria → consists of a double membrane, equal to 2 plasma membranes, placed side by side. outer membrane is smoothe and featureless, inner membrane has shelflike protrusions called cristae.

   True        False

2. flagella → the basic biological unit of living organisms, containing a nucleus and a variety of organelles enclosed by a limiting membrane.

   True        False

3. nucleoli → a dense central body in most cells containing the genetic material of the cell.

   True        False

4. free radicals → are highly reactive chemicals with unpaired electrons that can scramble the structure of proteins and nucleic acids.

   True        False

5. chromatin → when a cell is not dividing, its DNA is combined with protein and forms a loose network of bumpy threads.

   True        False