Chapter 6
golgi apparatus
organelle active in synthesis, modification, sorting, and secretion of cell products
mitochondrion
organelle where cellular respiration occurs and most ATP is generated
eukaryotic cell
a cell in which the DNA is in an organelle called the nucleus, which is bounded by a double membrane
cytosol
a semifluid jellylike substance in which all subcellular components are suspended
cell fractionation
a technique for studying cells that centrifuges test tubes and separates the major organelles from each other. order: 1. nuclei and cellular debris 2. mitochondria (and chloroplast, if from a plant) 3. microsomes - pieces of plasma membranes acells' internal membranes 4. ribosomes
ribosomes
complexes that make proteins, free in cytosol or bound to rough ER or nuclear envelope
plasmodesmata
cytoplasmic channels through cell walls that connect the cytoplasms of adjacent cells
lysosome
digestive organelle where macromolecules are hydrolyzed
nuclear envelope
double membrane enclosing the nucleus, perforated by pores, continuous with ER
chromatin
material consisting of DNA and proteins, visible in a dividing cell as individual condensed chromosomes
plasma membrane
membrane enclosing the cell
peroxisome
organelle with various specialized metabolic functions, produces hydrogen peroxide as a by-product, then converts it to water
flagellum
motility structure present in some animal cells, composed of a cluster of microtubules within an extension of the plasma membrane
endoplasmic reticulum
network of membranous sacs and tubes, active in membrane synthesis and other synthetic and metabolic processes, has rough (ribosome-studded) and smooth regions
nucleolus
nonmembranous structure involved in production of ribosomes, a nucleus has one or more nucleoli. here, a type of RNA called ribosomal RNA (rRNA) is synthesized from instructions in the DNA. also, proteins imported from the cytoplasm into large and small units of ribosomes and then leave to be made into a whole ribosome.
describe the molecular composition of nucleoli and explain their function.
nucleoli consist of DNA and the ribosomal RNA (rRNA) made according to its instructions, as well as proteins imported from the cytoplasm. together, the rRNA and proteins are assembled into large and small ribosomal subunits. (these are exported through nuclear pores to the cytoplasm, where they will participate in polypeptide synthesis.)
cell wall
outer layer that maintains cell's shape and protects cell from mechanical damage, made of cellulose, other polysaccharides, and protein
chloroplast
photosynthetic organelle, converts energy of sunlight to chemical energy stored in sugar molecules
microvilli
projections that increase the cell's surface area
central vacuole
prominent organelle in older plant cells, functions include storage, breakdown of waste products, hydrolysis of macromolecules, enlargement of this is a major mechanism of plant growth
centrosome
region where the cell's microtubules are initiated, contains a pair of centrioles
cytoskeleton
reinforces cell's shape, functions in cell movement, components are made of protein
what role do ribosomes play in carrying out genetic instructions?
ribosomes in the cytoplasm translate the genetic message, carried from the DNA in the nucleus by mRNA, into a polypeptide chain
chromosomes
structures that carry the genetic information. each one contains one long DNA molecule associated with many proteins
chromatin
the complex of DNA and proteins making up chromosomes
cytoplasm
the interior of the cell
nuclear lamina
the nuclear side of the envelope is lined by this, a netlike array of protein filaments that maintain the shape of the nucleus by mechanically supporting the nuclear envelope