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Chapter 2

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York University
BIOL 1000
Angelo Belcastro

2.1 Robert Hooke Cork and realized they had small rooms in them- cells Cell Theory 1. All organisms are made up of one or more cells 2. The cell is the most basic structural and functional unit of all living organisms 3. Cells only arise from pre-existing cells All forms of life are grouped in DOMAINS Archea, bacteria and Eukarya Evolution of Microscopes 2.1b Cells are enclosed by plasma membrane o composed of lipids and embedded proteins molecules o Lipid bilayer is hydrophobic, but though channels some h2o may enter the cell Cytoplasm Contains organelle, cytoskeleton and and cytosol: aq water soln that contains ions Prokaryotes No nucleus, rather a central area where most of the DNA is located called nucleoid Bacteria and Archea Most common shapes: spherical, rodlike, spiral Prokaryotic chromosome DNA is copied onto mRNA, where ribosomes use this info to gather aa into proteins Have cell walls, providing cell with ridgity and protection due to harsh environments o Layer of polysaccharides called the glycocalyx o When glycocalyx is loose, known as slime layer where as when its more dense it is called a capsule o Enables cells to attach on to other cells to form colonies Few contain inner membranes, hence process occur in cytoplasm or plasma membrane (some photosynthetic do not) Movement is carried out with flagella, which extends from cell surfave Bacterium flagella propelling action, rotation in socket Pili extended from cell walls, attaching cell to other cells or things 2.3a Eukaryotic Cells Divided into 4 groups : fungi, animal, plants protists All have true nucleases Cytosol :involved in energy metabolism, and molecular synthesis, provides support and motility Plasma membrane: transports substances into/out cell. Embedded proteins o Act as channels o Act as receptors: recognize and bind specific molecules to trigger responses o Act as markers to label cells that belong inside of the cell Cell wall in fungi and plants 2.3b Nucleus Nuclear Envelope: separates cytoplasm, 2 membranes Lamins lines (intermediate filament): reinforces inner surface of nuclear envelope Embedded in nuclear envelope nuclear pore complexes o Formation of many nucleoporins o Exchanges content with nuclear and cytoplasm, and prevents certain content from leaving the nucleus o Nuclear pore helps assist large molecules to pass, where as small ones go w/o any assistance o RNA molecule acts as chaperone through pore o Things imported: enzymes for DNA repl. o Proteins needed to enter cell have certain seq’n called: nuclear localization signal o Protein in cytosol binds to signal and helps move it to nuclear pore complex Nucleoli (nucleolus): one or more. Form around genes coding for rRNA molecules of ribosomes. o Within, info in rRNA genes copied into rRNA molecules, combing with proteins for form rib. Subunits o Leaves nucleus and enter cytoplasm, joining mRNA to form ribosomes ATP formation in mitochindira: cristae and matrix 2.3c Ribosomes larger in eukaryotes, 4 types of rRNA molecules Some free in cytosol, some attached to membranes, nuclear envelope, some endoplasmic reticulum 2.3d Endomembrane System Divides cells in functional and structural compartments Synthesizes and modifies proteins, and their transport into membranes , synthesis of lipids, detox of toxins Connected indirectly by vesicles Components: nuclear envelope, (R&S) Endoplasmic Reticulum, golgi complex, lysosomes, vesicles, plasma membrane Endoplasmic Reticulum Rough o Ribosomes attached to it, proteins enter lumen where they form into their final shape o Chemical modifications: addition of carb groups to make glycoproteins occur in lumen o Proteins are delivered to other regions via vesicles o Next step usually Golgi complex, which packages for delivery o Connected to nuclear envelope, proteins made here enter space between 2 membranes  move into ER o Found vastly in pancreatic cells, due to manufacture of enzymes Smooth o Synthesis of lipids o In liver cells, contain enzymes that break down toxins Golgi Complex Number and size vary, with cell type Receives proteins in the ER, where it receives it from vesicles Chemical modification: removal of aa segments, adding of some functional groups/lipids or carbs Secretes, embedded, others placed in lysosomes Golgi labels proteins as to where their final destination is Vesicles may attach to plasma membrane to aid in growth of the cell Lysosomes Contain hydrolytic enzymes for the digestion of proteins, lipids, nucleic acids, carbs Cell recycles subunits Only found in animals Lysosomes come from the budding of the golgi Enzymes are made in the ER Autophagy: digestion of organelles not functioning properly Summary Golgi complex is the deliverer and distributor of proteins From here they may be secreated out in vesicles or storage then out through exocytosis Materials entering the cell are also sorted by the golgi complex 1. Instructions for protein building leave nucleus into cytoplasm 2. Proteins assembled from aa by the ribosomes attached to the ER 3. Proteins then made by ER ribosomes enter ER cisternae and chemical modifications are made (membrane lipids) 4. Vesicles arise from ER and transported to Golgi for further modifications 5. Protein/lipid modifications are made in golgi and are prepared into vesicles 6. Vesicles transport to plasma membrane and either move out, or remain as storage 7. Lysosomes from Golgi digest damaged organelles, or fuse with endocytic vesicles for sorting in Golgi Mitochondria Site of cellular respiration Generate majority of ATP made by cell Enclosed by 2 membranes o Outer mitochondrial membrane & inner mitochondrial membrane o Atp generated in matrix and cristae Matrix contains DNA may have been alone prior to entering eukaryotic cell 2.3f Cytoskeleton Protein fibres helps maintain cell shape In plants most support is given by cell wa
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