Chp 3 Cell structure

lysosomes

contain more than 60 different enzymes. A primary lysosome is one that contains only diges- tive enzymes (about 40 different types) within an environment that is more acidic than the surrounding cytoplasm. A primary lysosome may fuse with a food vacuole (or with another cellu- lar organelle) to form a secondary lysosome in which worn-out organelles and the products of phagocytosis can be digested. Thus, a secondary lysosome contains partially digested rem- nants of other organelles and ingested organic material.

Nucleus

largest of the organelles, contains one or more nucleoli—centers for the production of ribosomes (not all cells have)

Apoptosis

programmed cell death. Lysosomes release digestive enzymes into the cell

residual body

A lysosome that contains undigested wastes Residual bodies may eliminate their waste by exocytosis, or the wastes may accumulate within the cell as the cell ages.

Cytoskeleton

Actin and myosin (microfilaments). Spindle apparatus (microtubules).

Peroxisomes

Contain enzymes that detoxify harmful molecules and break down hydrogen peroxide to water and oxygen. Oxidation of toxic molecules by peroxisomes is an important function of liver and kidney cells.

Endoplasmic Reticulum (ER)

Granular (rough) ER: Bears ribosomes on surface, in cells active in protein synthesis. Proteins enter cisternae are modified for secretion. Agranular (smooth) ER: Provides site for enzyme reactions in steroid hormone production and inactivation. Storage of Ca2+ in striated muscle cells.

Microvilli

In areas of the body that are specialized for rapid diffusion, the surface area of the cell membranes may be increased by numerous folds called microvilli. The rapid passage of the products of digestion across the epithelial membranes in the intestine, for example, is aided by these structural adaptations. Similar microvilli are found in the epithelium of the kidney tubule, which must reabsorb various molecules that are filtered out of the blood

Cytoplasm

Jelly-like matrix within the cell. Includes organelles and cytosol. Highly organized structure with microtubules and microfilaments that function as cytoskeleton.

Cell Nucleus

Most cells have single nucleus. Enclosed by inner and outer membrane (nuclear envelope). Outer membrane is continuous with ER. Nuclear pore complexes fuse inner and outer membranes together. Selective active transport of proteins and RNA. Regulation of gene expression. Transport of mRNA out of nucleus to ribosomes. Nucleoli: DNA contains the genes that code for the production of mRNA.

Cell Death

Pathologically: Cells deprived of blood supply swell, the membrane ruptures, and the cell bursts (necrosis). Apoptosis: Cells shrink, membranes become bubbled, nuclei condense. Capsases ("executioner enzymes"): Mitochondria membranes become permeable to proteins and other products. Programmed cell death: Physiological process responsible for remodeling of tissues during embryonic development and tissue turnover in the adult.

Phagocytosis

Phagocytic cells use pseudopods to surround and engulf particles. Pseudopods join, fuse, and surround ingested particle (food vacuole). Lysosomes digest food vacuole. Protects from invading organisms. Removes debris.

Endocytosis:

Pinocytosis: Nonspecific process. Plasma membrane invaginates, fuses, vesicle containing ECF pinches off, and vesicle enters cell.

Exocytosis:

Process by which cellular products are secreted into extracellular environment. Proteins and other molecules to be secreted are packaged in vesicles by Golgi complex. Vesicles fuse with plasma membrane and release contents into extracellular environment. (i.e Acetylcholine--Ach)

Autophagy

Process that destroys worn-out organelles, so that they can be continuously replaced.

ribosome

Protein factories of the cell Messenger RNA takes genetic information to the ribosome so a protein can be assembled. Very small Found free in the cytoplasm or associated with the rough ER Broken into 2 subunits composed of proteins and ribosomal RNA while not in use

Flagella

Simple whip-like structure that propels sperm through its environment

Mitochondria

Sites of energy production Have an inner membrane and an outer membrane (smooth) separated by an intermembranous space Inner membrane is folded into cristae All cells in the body, with the exception of mature red blood cells, have from a hundred to a few thousand organelles called mitochondria. mitochondria contain their own DNA.

Golgi Complex

Stacks of hollow, flattened sacks with cisternae. One side of sack faces site for entry of vesicles from ER that contain cellular products. Other site faces towards plasma membrane and releases vesicles of chemically modified products. Modifies proteins, separates according to destination, and packages into vesicles.

Cytoplasm

aqueous content inside the cell but outside the nucleus

Plasma (Cell) membrane

allows selective communication between the intracellular and extracellular compartments Composed primarily of a double layer of phospholipids and proteins—Carbohydrates are primarily associated with the outer surface of the cell membrane. Hydrophobic middle restricts passage of water and water soluble molecules and ions. Contains cholesterol

Cilia

Tiny hair-like structures that project from the surface of the cell. Stroke in unison. in Respiratory tract, uterine tube.