Chapter Two: The Cytoplasm

Cytoplasm

The part of the cell that lies internal to the plasma membrane and external to the nucleus. Contains cytosol, organelles, and inclusions

Cytosol

The jellylike, fluid-contaning substance within which the other cytoplasmic elements are suspended. Consists of water, ions, and many enzymes

Ribosomes

Protein synthesis for cellular or extracellular function. They are constructed of proteins and ribosomal RNA. Consists of two subnits.

Translation

The process on the ribosomes where amino acids are linked together to form protein molecules. It is dictated by DNA which carry instructions to the ribosome by mRNA.

Free ribosomes

Float freely within the cytosol. They make the soluble proteins that function within the cytosol itself.

Rough ER Structure

Consists mainly of stacked membrane-enclosed cavities called cisterns. Ribosomes stud the external faces of the membranes of the rough ER.

Rough ER Function

Secrete proteins from the ribosomes, makes digestive enzymes for lysosomes, makes integral proteins and phospholipids.

Smooth ER Structure

Is continuous with the right ER and consists of tubules arranged in a branching network

Smooth ER Function

Lipid metabolism, the making/breaking down fats, calcium ion storage

Golgi Apparatus Structure

Stack of three to ten disc-shaped cisterns, each bound by a membrane. The cis (convex) face recieves spherical, membranous transport vesicles from the rough ER. New vesicles bud off a trans (concave) face to leave the apparatus.

Golgi Apparatus Function

Sorts, processes, and packages the proteins and membranes made by the rough ER.

Pathway A in the golgi apparatus

Occurs in gland cells where the protein product is contained in secretory vesicles which release their contents to the cell’s exterior

Pathway B in the golgi apparatus

The membrane of the vesicle fuses to and contributes to the plasma membrane, whose components are constantly renewed and recycled

Pathway C in the golgi apparatus

The vesicle leaving the golgi is a lysosome, a sac filled with digestive enzymes, that remains inside the cell

Lysosomes

Spherical, membrane-walled sacs containing many kids of digestive enzymes that can digest many types of large molecules. The break apart and digest unwanted substances.

Mitochondria Structure

Look bean shaped. It is enclosed by two membranes including the smooth outer membrane and the inner folded membrane that produces cristae. The cristae protrude into the matrix (jellylike substance). Contain maternal DNA.

Mitochondria Function

Produce the energy for cellular function. Systematically release the energy stored in chemical bonds of nutrients molecules and transferring the energy to produce ATP.

Peroxisomes Structure

Membrane-walled sacs that resemble small lysosomes and contain oxidases and catalase.

Peroxisomes Function

Play a major role in removing toxic substances from the body and break down long chains of fatty acids.

Oxidases

Use oxygen to neutralize aggressively reactive molecules called free radicals converting them to hydrogen peroxide. If left as free radicals, they can destroy membranes and DNA.

Catalase

Converts hydrogen peroxide into water and oxygen

Cytoskeleton Structure

An elaborate network of rods running throughout the cytosol. Contains microfilaments, intermediate filaments, and microtubules

Cytoskeleton Function

Support cellular structures and generate various cell movements

Microfilaments

The thinnest elements of the cytoskeleton, are strands of the protein actin. Actin filaments interact with myosin to generate contractile forces within the cell. Enables some cells to use pseudopods in a crawling action. Unstable and constantly re-forming.

Actin and Myosin

Contractile proteins in cells, especially abundant in muscle cells

Intermediate Filaments

Tough, insoluble protein fibers, with a diameter between those of microfilaments and microtubules. Act like wires to resist pulling forces that are placed on the cell. Link adjacent cells together by attaching to specific cell junctions called desmosomes.

Microtubules

The elements with the largest diameter, are hollow tubes made of spherical protein subunits called tublins. The radiating patter of these stiff substances determine the overall shape of the cell, and the distribution of cellular organelles

Kinsesins and Dyneins

Small motor proteins that help organelles move within the cytoplasm

Centrosome

Spherical structure in the cytoplasm near the nuclear. It contains the centrosome matrix and centrioles.

Centrosome matrix

An outer cloud of proteins. It seeds the growth and elongation of microtubules

Centrioles

Barrel-shaped structures that lie perpendicular to one another. The wall of each has 27 short microtubules which are stable. These structures act in forming cilia, flagella, and the mitotic spindle

Cytoplasmic Inclusions

Temporary structures in the cytoplasm that may or may not be present in a given cell type

Lipid Droplets

An inclusion that are spherical drops of stored fat

Glycosomes

An inclusion that store sugar in the form of glycogen. Contain enzymes that make and degrade the glycogen into its glucose subunits.