BY 30 – Fall 2001
5.1.
Overview to the Cell
a. The ________________________ is the basic structural and functional unit of a living organism. This idea is one part of a concept known as the _________________________________.
b. Cells can be distinguished into two basic classes called _________________ and ________________________. Of these, the ______________________ lack a true nucleus whereas eukaryotes possess a nucleus and _______________________________.
c. The process by which cells become specialized both structurally and functionally is called __________________________________. As a result cells can be organized into different ________________________________.
d. Most cells have three basic parts: the _______________________________; ____________________________; and a ____________________________.
5.2.
The Plasma Membrane
a. The structure of the plasma membrane is best described by the ____________________________ model. According to this model, the membrane consists of a lipid _________________________ into which various ______________________ are dispersed.
b. The main component of the bilayer are ___________________________ molecules, each which contains two __________________________ and a ________________________________ group.
c. Phospholipid molecules are examples of ____________________________ molecules meaning that they have both polar and nonpolar regions. In this case, the nonpolar region is represented by the _______________________ portion of the molecule while the ____________________________ portion represents the polar region.
d. Because of the hydrophobic interior, _______________________________ substances have difficulty crossing the lipid bilayer which is thus considered to be _______________________________ to them.
e. Besides phospholipids, other lipid components of plasma membranes include combinations of lipids and carbohydrate called ________________________, and _______________________. It is the ____________________________ that keeps the membrane fluid.
f. Membrane proteins come in two distinct classes called __________________ and ______________________________ proteins. Of these two, it is the ___________________________ that are completely inserted into the bilayer. They also often have sugars attached making them _____________________.
g. Integral membrane proteins function as ______________________________; ______________________________; _______________________________; or ________________________________.
h. Transport proteins that act as either _________________ channels or carriers that allow the passage of ______________________ substances across the membrane. Because not all such substances can cross at all times, the membrane is said to be __________________________________ for them.
i. Peripheral membrane proteins function as _____________________________ or as attachment sites for the ____________________________________.
j. The __________________________________ consists of all the carbohydrate groups on the outside of the plasma membrane. Because this structure varies between cell types, it forms one basis of cellular _______________________.
k. Integral membrane proteins that function as receptors have a _______________________ site for a particular _______________________. Examples of ligands include ____________________________________ and ___________________________, each of which has a specific receptor.
l. Receptor activation following ligand binding usually involves the activation of a __________________ protein which in turn can lead to the opening of a _____________________________ or activation of an enzyme that produces __________________________ messengers such as cAMP or IP3. Second messengers in turn activate ________________________ which phosphorylate proteins leading to a change in cell function.
5.3.
Cytoplasmic Organelles
a. The region between the nucleus and the plasma membrane is called the __________________________.
b. The cytoplasm has three different components: the _____________________, and one or more _____________________ and ________________________. Of these, the fluid component is called the ____________________________.
c. __________________________ (which literally mean “little organs”) are for the most part surrounded by a _______________________________ thereby forming a specialized internal environment.
d. __________________________ are often called the “power plants” of the cell because they represent the site where most __________________________ is produced in a process that requires _________________________. In general the number of mitochondria per cell varies with the _____________________ requirements of that cell.
e. Mitochondria possess ________________ sets of membranes; the inner one is thrown into folds called __________________________.
f. ___________________________ are small dark staining structures consisting of proteins and rRNA. They represent the site where ___________________ synthesis takes place.
g. Ribosomes can be either free or attached to the ________________________. Proteins made on free ribosomes typically remain and function within the _____________________________, whereas proteins made on the RER are destined for use either in the ___________________________ or outside of the cell.
h. The type of endoplasmic reticulum (ER) that lacks ribosomes is called ________________________ whereas the type that possesses ribosomes is called __________________________. In both types, the internal space is referred to as a __________________________. Of the two types, it is the ________________________ that is involved in the synthesis of lipids and the detoxification of certain drugs.
i. The _________________________ has 2 surfaces called the cis-face and the trans-face. Of these two, vesicles from the RER enter the Golgi at the _______________ face. Following modification, concentration, and packaging of protein, vesicles leave at the ______________________ face where they become either ______________________________ vesicles or ____________________. Alternatively, vesicles containing lipid and protein destined for the plasma membrane travel to, and _______________________ with it.
j. Lysosomes are the sites of intracellular ______________________________ involving enzymes known as ____________________________ because their pH optima lie in the acidic range. On the other hand, ___________________, which resemble lysosomes, do not originate from the Golgi and detoxify a number of harmful substances using ______________________ enzymes.
k. The cytoskeleton consists of ______________________________________, _____________________________, and ____________________________. Of these, it is the _______________________________ which are hollow and consist of the protein _____________________________.
l. Microfilaments are composed of the protein __________________________, and form the core of cellular projections called ________________________.
m. The _________________________ represents the microtubule-organizing center, and also contains the paired ______________________________, which help to organize the mitotic spindle and provide the origin for _________________________ and _______________________________.
n. While a cell may have numerous cilia, they typically have only one _____________________________. Both structures consist of microtubules organized into __________________ peripheral doublets and _____________ central single microtubules. While _________________________ function to move substances along the cell surface, ______________________________ function to move the entire cell.
5.4.
The Nucleus
a. When a cell has more than one nucleus, it is referred to as ______________________________. On the other hand cells that have no nuclei are unable to ______________________ or make _________________ - an example being ___________________ cells.
b. The function of the nucleus is to store and transmit _____________________ in the form of _____________________, and to pass this information onto the cytoplasm in the form of _______________________________.
c. The nucleus has three basic components called the ____________________, ___________________________ and ______________________________.
d. The nuclear envelope is a _______________________ membrane; the outer portion is continuous with the ____________________________. At various points, these two membranes fuse to create ___________________________.
e. _____________________ are dark staining spherical bodies which are the site of ribosome subunit assembly. These subunits then leave the nucleus through ______________________ to gain access to the cytoplasm.
f. Chromatin consists of __________________________ and associated proteins. During cell division, it condenses to form ______________________.