Human Anatomy Laboratory Manual (Hartline)-Chapter 3: Collaborative Study Activities-Cell Structure

smooth endoplasmic reticulum (SER)

SER functions include synthesis of carbohydrates, lipids, andsteroid hormones; detoxification of medications and poisons; and storing calcium ions. In muscle cells, a specialized SER, called the sarcoplasmic reticulum, is responsible forstoring calcium ions that are needed to trigger the muscle cells' coordinated contractions.

Golgi body

Sorting, tagging, packaging, and distributing lipids and proteins takes place in theGolgi apparatus. The Golgi can be thought of as the "post office" ofa cell.

centrosome

The centrosome is a microtubule-organizing center found near the nuclei of animal cells. Centrosomes play a major role in cell division by organizing the microtubules that move and separate chromosomes into separate cells.

chromatin

Chromatin describes the material that makes up the chromosomes both when condensed (packed into tight structures for cell division) and decondensed (loose; chromatin is loose most of the time).

plasma membrane (cell membrane)

The plasma membrane is a phospholipidbilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment.The plasma membrane controls the passage of organic molecules, ions, water, and oxygen into and out of the cell. Wastes (such as carbon dioxide and ammonia) also leave the cell by passing through the plasma membrane.

microvillus (pl. microvilli)

The plasma membranes of cells that specialize in absorption fold into finger like projections that we call microvilli. Such cells typically line the small intestine, the organ that absorbs nutrients from digested food.

cilium (pl. cilia)

Cilia are protein fibers anchored inside of a cell with the majority of thesehair-like fibers on the exterior of a cell. In humans, cilia move substances along the cell's outer surface. For example, the cilia lining the Fallopiantubes move the ovum (egg) toward the uterus. Another example is the cilia on the cells lining the respiratory tract that moves mucus, and debris that gets trapped in the mucus, away from the lungs.

cytoskeleton

A network of protein fibers creating support, structure, shape, and movement for cells. The cytoskeleton can be thought of as the "skeleton" of the cell. There are three types of fibers within the cytoskeleton: microfilaments, intermediate filaments, and microtubules.

nuclear pore

Passageways that let materials in and out of the nucleus.

rough endoplasmic reticulum (RER)

Ribosomes attached to the RER transfer their newly synthesized proteins into the RER's interior where they undergo structural modifications, such as folding or acquiring side chains. These modified proteins incorporate into cellular membranes. The proteins synthesized with the RER can also be secreted from thecell (such as protein hormones and enzymes). The RER also makes phospholipids for cellular membranes.

vacuole / vesicle / storage vesicles

Vesicles and vacuoles are membrane-bound sacs that function in storage and transport. Other than the fact that vacuoles are somewhat larger than vesicles, there is a very subtle distinction between them: The membranes of vesicles can fuse with either the plasma membrane or other membrane systems within the cell and vacuoles cannot. Storage vesicles can store materials until they are needed, such as mucin to make mucus in goblet cells and lipid droplets in adipose cells (fat cells).

peroxisome

Peroxisomes are small, round organelles enclosed by single membranes. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many poisons that may enter the body. (Many of these oxidation reactions release hydrogen peroxide, H2O2, which would be damaging to cells; however,when these reactions are confined to peroxisomes, enzymes safely break down the H2O2 intooxygen and water.) For example, alcohol is detoxified by peroxisomes in liver cells.

nucleus (pl. nuclei)

Houses the cell’s DNA and directs the synthesis of proteins (gene expression) and the synthesis of ribosomes. Composed of the chromatin, nucleolus or nucleoli, a nuclear envelope, and nuclear pores.Nucleoplasm is essentially the cytoplasm of the nucleus.

flagellum (pl. flagella)

Flagella are long, hair-like structures that extend from the plasma membrane and enable an entire cell to move. The only human cell type that has a flagellum is a sperm cell.

nuclear envelope

Two membranes that surround the nucleus and separate it from the rest of the cell.

lysosome

Lysosomes are the cell’s “garbage disposal.” Enzymes within the lysosomes aid in breaking down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.

nucleolus (pl. nucleoli)

A darkly staining area within the nucleus called the nucleolus aggregates the ribosomal RNA with associated proteins toassemble the ribosomal subunits that are then transported out through the pores in the nuclear envelope to the cytoplasm.

cytoplasm

Even though the cytoplasm consists of 70 to 80 percent water, it has a semi- solid consistency, which comes from the proteins within it. Glucose and other simple sugars, polysaccharides, aminoacids, nucleic acids, fatty acids, and derivatives of glycerol are also foundin the cytoplasm. Ions of sodium, potassium, calcium, and many other elements also dissolve in the cytoplasm. Many metabolic reactions, including protein synthesis, take place in the cytoplasm.