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Biological Science
BISC 160
Dr.Beckie Symula

Chapter 5 5.2 What features characterize prokaryotic cells?  Prokaryotic cells share certain features o Plasma membrane separates it from external environment o Nucleoid contains DNA o Cytoplasm: the rest of the cell  Cytosol: mainly water, contains dissolved ions, small molecules, and soluble macromolecules such as proteins  Ribosomes: made of RNA and proteins, 25 nm, protein synthesis  Specialized features are found in some prokaryotes o Cell walls  In bacteria but not archaea  Contain peptidoglycan  Slimy layer called a capsule encloses the cell wall and keep cells from drying out  Capsule is not essential to prokaryotic life, and most prokaryotes produce no capsule o Internal membranes  cyanobacteria and some other bacteria carry out photosynthesis  Internal membrane systems contain molecules needed for photosynthesis  Other prokaryotes have internal membrane folds that function in cell division or in various energy- releasing reactions o Flagella and Pili  Some prokaryotes swim by flagella  Made of the protein flagellin Cause the movement (propeller motion) of a cell  Pili is made of protein that are hairlike and shorter, used for adherence  Fimbriae are similar to pili ut shorter and help cells adhere to surfaces such as animal cells for food and protection o Cytoskeleton  Rod-shaped bacteria have a helical network of filamentous structures that extend down the length of the cell just inside the plasma membrane  Made of proteins and are similar to actin in eukaryotic cells 2 [Type text] 5.3 What features characterize eukaryotic cells?  Compartmentalization is the key to eukaryotic cell function o Nucleus contains DNA; first steps in gene replication take place here o Mitochondria converts energy stored in bonds of carbohydrates and fatty acids into ATP o Endoplasmic reticulum and Golgi apparatus synthesize some proteins by ribosomes and package them and send them to locations in the cells o Lysosomes and vacuoles are cellular digestive systems by hydrolyzing large molecules o Chloroplasts perform photosynthesis  Some structures are not considered organelles because they lack membranes: o Ribosomes o Cytoskeleton (made up of protein-based filaments) o Extracellular matrix  Ribosomes are factories for protein synthesis o Composed of two different-sized subunits o Eukaryotic ribosomes are generally larger, but structure of prokaryotic ribosomes is better understood o rRNA and 50 different protein molecules which are noncovalently bound to the rRNA o in prokaryotic cells, ribosomes float freely in the cytoplasm o in eukaryotic cells they are in the cytoplasm attached to ER or inside mitochondria and chloroplasts  The nucleus contains most of the genetic information o Nucleus is the largest organelle o Location of DNA and site of DNA replication o Gene transcription is turned on or off o The Nucleolus is where ribosomes being to be assembled from RNA and proteins o Two membranes surround the nucleus called the nuclear envelope  Separates the genetic material from the cytoplasm.  Functionally it separates DNA transcription from translation which occurs in cytoplasm o Nuclear localization signal
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