Chapter 6

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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


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