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University of Ottawa

MIDTERM 1 NOTES TOPIC 1 21 Basic Features of Cell Structure and Function Cell Theory oAll organisms are composed of one or more cells oThe cell is the basic structural unit of all living organisms oCells arise only from the division of preexisting cells unicellular organisms bacteria and archaea some protists such as amoebas and some fungi such as yeast 21 a Cells are Small and are Visualized Using a Microscope all forms of life grouped into bacteria archaea eukarya smallest bacteria have a diameter of 05 micrometers in diameter most multicellular are 530 micrometers microscopy technique for producing visible images of objects or other things that are too small for the human eye cells are small because of the SA to V ration volume of a cell determines the amount of chemical activity that can take place within it increase exchanging ability by flattening developing surface folds or extensions that increase their surface area 21b Cells Have a DNA containing Central region that is surrounded by cytoplasmall cells bounded by plasma membrane bilayer made of lipids with embedded protein molecules lipid bilayer is hydrophobic barrier to passage of watersoluble substances but selected watersoluble substances can penetrate cell membranes through transport protein channels contains DNA molecules that form genes and code for proteins which maintain DNA structure and enzymes that duplicate DNA into RNA cytoplasm parts of cell between plasma membrane and the central region which contain organelles organelles small organized structures important for cell function cytosol aqueous solution containing ions and various organic moleculessynthesis and assembly of most molecules for growth and reproduction 22 Prokaryotic Cells very smallsingle group of organisms lacking a nucleus nucleoid has no boundary membrane separating it from cytoplasm genetic material located herethree shapes spherical rodlike spiral Ex Ecoli DNA is a single circular molecule that unfolds when released from the cell DNA molecule is the prokaryotic chromosome Information copied into mRNA and ribosomes use mRNA to assemble amino acids into proteins Plasma membrane is surrounded by a rigid external layer called cell wall Cell wall protects cell Plasma membrane transports materials in and out of cell metabolize food molecules into ATP Flagella pili 23 a Eukaryotic Cells have nucleus Eukaryotes that are defined by having cells where DNA is contained within a membranebound cytoplasm called nucleus Proteins form channels Some proteins in membrane act as receptors Plasma membrane protein markers 23 b Eukaryotic Nucleus contains more DNA than Prokaryotic Nucleoid Nucleus separated from cytoplasm by nuclear envelopeNetwork of protein filaments called lamins lines and reinforces the inner surface of the nuclear envelope in animal cells Nuclear pore complex exchanges components between nucleus and cytoplasm and prevents transport of material not meant to cross the nuclear membrane Nucleoplasm liquid or semiliquid substance within nucleus Chromatin combo of DNA and proteins Chromosome one complete DNA molecule with its associated proteins Nucleoli form around genes coding for rRNA molecules of ribosomes 23 c Eukaryotic Ribosomes Are Either Free in the Cytosol or Attached to MembranesRibosomes are freely suspended in cytosol others are membrane attached Ribosomes are attached to nuclear envelope but most are to endoplasmic reticulum23 d Endomembrane System Divides Cytoplasm into Functional and Structural Components endomembrane system collection of interrelated internal membranous sacs that divide the cell into functional and structural compartments synthesis and modification or proteins and their transport into membranes and organelles or to the outside of the cell synthesis of lipids and detoxification of some toxins vesicles which are small membranebound compartments that transfer substances between parts of the system
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