BIOLOGY 1030

SUMMER 1999

UNIT II. THE STRUCTURE OF LIVING THINGS

 

organization	nucleus vs nucleoid vs nucleolus
homeostasis	70S vs 80S ribosomes
reproduction	endomembrane system
metabolism and metabolic diversity	cytoskeleton - microtubules vs microfilaments
cell theory of life	mitochondria and plastids and endosymbiosis
cellular vs noncellular	membranes and boundaries
prokaryote vs eukaryote	viruses and viroids

1. The unity and diversity of life
1. basic characteristics
1. organization and hierarchy
2. metabolism - use of chemistry and energy
3. adaptability and responsiveness (homeostasis)
4. reproduction -- evolution
2. organisms - the diversity of life
1. metabolic diversity
2. photoautotrophs vs. chemoheterotrophs
3. specialized metabolic pathways
4. structural diversity
1. plants, animals, and fungi
2. protists = protozoans and algae
3. eubacteria and archaebacteria
4. viruses and viroids?
5. clay??
3. structural similarity
1. suppose you were handed a living alien organism--basic questions still hold
1. How is it put together?
2. How does it function?
2. present understanding of Earthly organisms indicates a few basic themes,constantly repeated
1. large organisms are organized into organs and organ systems; organs are composed of tissues; tissues are composed of cells
2. small organisms lack tissues and organs, but are composed of cells
3. smaller objects without cellular structure exist, but do not metabolize or reproduce
4. implication is that cells represent some sort of basic unit of life (note: only discovered late 17th and early 18th century by van Leeuwenhoek and Hooke)
3. results summarized by Schleiden, Schwann, and Virchow in the cell theory of life
1. all organisms are composed of cells
2. cells are the basic unit of life (have all of the characteristics of life)
3. cells come from pre-existing cells
4. implicaton is that understanding cells fundamental to understanding life
5. why this similarity? what is so special about a cellular structure?
1. compartmentalization and specialization
2. survival of organism not dependent on survival of individual cells
3. favorable surface to volume ratios
2. Cellular and subcellular structures
1. common tools of the cell biologist
1. microscopy
1. magnification vs resolution
2. light microscope
1. magnify up to 1500x (need oil at high power)
2. resolution .2 micrometers
3. electron microscope (scanning vs transmission; freeze fracture)
1. magnification - 100,000x
2. resolution - .1 nm
4. atomic force and X-ray microscopes
2. cell fractionation
1. centrifugation
2. gel electrophoresis
3. radiotracer experiments
2. basic cell structure
1. major parts
1. membrane or boundary
1. phospholipids and proteins
1. phospholipids are similar to soaps, form a bilayered fluid structure (nothing really holding the molecules together--hydrophobic bonding)
2. proteins perform the actual work of the membrane
2. genetic material
1. in all cellular life-forms we know, consists of DNA; messages are translated through the action of RNA
3. cytoplasm
1. fluid in the cell
2. together with the cell membrane contains the proteins and complex structures necessary for metabolism
4. a closer look at cell membranes
1. functions of the cell membrane
1. boundary
2. controls passage of material - most noticeable in resting potential
3. hold cells together
4. binding spots for cytoskeleton
5. help cells recognize each other
6. function in growth and division
2. implications for structure
1. want something rather loosely put together (not rigidlike plastic)
2. what actually holds it together
1. types of bonding between molecules
1. covalent bonding vs ionic bonding vs hydrogen bonding
2. hydrophobic/hydrophilic interactions
3. probably want more than one kind of molecule in membrane because of the variety of interactions and functions that it must perform
4. actual chemical structure
1. phospholipid bilayer
1. amphipathic - hydrophobic/hydrophilic
2. fluid in plane (flip-flops rare) because loose bonding
3. fluidity depends on nature of the phospholipids
4. allows free passage of nonpolar molecules (diffusion), but blocks polar and ionic compounds
5. allows membranes to unite
2. embedded and associated proteins allow for all of the other functions
1. controllable passage
1. facilitated diffusion (permease) and active transport both require proteins
2. cell-to-cell signalling
3. attachment of the cytoskeleton
4. cell junctions
1. tight junctions - glue
2. desmosomes - rivet
3. gap junctions - closable channels
4. plasmodesmata - complete cytoplasmic junctions
2. two major types of cells found in three major domains of cellular life (see chart on page 89)
1. Archea - prokaryote cell type
2. Eubacteria - prokaryote cell type
3. Eukaryote - eukaryote cell type
3. structure of eukaryotic cells
1. nucleus
1. nuclear envelope: double membrane, pores, protein layer
2. chromosomes (chromatin) containing  DNA & protein
3. nucleolus - ribosome production
2. cytoplasmic structures
1. ribosomes - make proteins
1. RNA and protein
2. come in 2 parts
3. may be attached or free
4. 80S
2. endomembrane system
1. endoplasmic reticulum - system of tubes and sacs
1. smooth ER - lipid & carb. metabolism
2. rough ER - protein synthesis (secretion) & membrane production
2. transport vesicles (to Golgi apparatus)
3. Golgi apparatus - final preparation of stuff from rough ER
4. transport vesicles
1. from Golgi to cell
2. from Golgi to cell membrane
3. specialized vesicles
1. lysosomes - digest macromolecules (intracellular digestion after phagocytosis - Tay-Sachs syndrome results from the failure of lysosome digestion)
2. vacuoles
1. food
2. contractile
3. central vacuole of plants
3. microbodies - enzymes for special functions; grow in place
4. mitochondria
1. double membrane, DNA, ribosomes
2. conversion of pyruvate energy to ATP energy
5. plastids
1. double membrane, DNA, ribosomes
2. thylakoids
3. chlorophyll - energy capture
4. enzymes for glucose and starch production; carotenoid pigments
6. cytoskeleton
1. function in structure & movement
2. three components
1. microtubules - hollow rods
1. basic shape of cell, hold parts in place, move by pushing and pulling (spindle)
2. also functions as railroad - motor molecules
3. also basis of flagella & cilia to move cells from place to place
1. have 9+2 skeleton with side-arms of dynein between pairs for movement
2. microfilaments - actin (& myosin) rods
1. support & movement (cytoplasmic streaming; muscles)
3. intermediate filaments - structure
3. cell surface
1. cell membrane
2. cell walls
1. in plants - cellulose in polysaccharide matrix
2. in fungi - chitin
3. in animals - absent, but many have a fuzzy glycocalyx
4. structure of prokaryote cells
1. genetic material a single circular molecule of DNA in a nucleoid
2. cytoplasmic structures
1. 70S ribosomes
2. endomembrane structure (possible, usually missing)
3. cell surface
1. cell membrane similar to eukaryotes (different versions of phospholipids)
2. wall with peptidoglycan  (Gram positive vs Gram negative)
5. viruses - non-cellular structure
1. envelop (sometimes)
2. protein capsid
3. genetic material - either DNA or RNA
6. cell structure and the treatment of infectious diseases
1. resident flora
2. Koch's postulates and the determination of infectious agents
3. mechanisms of antibiotic activity
 

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