chapter 3 learning objectives Flashcards
describe the 4 major processes of living cells
growth- increase in size
reproduction- increase in number
responsiveness- ability to react to environmental stimuli
metabolism- controlled chemical reactions of organisms
(occurs in all bacteria, archaea, eukaryotes)
describe the composition, function, and relevance to human health of glycocalyces
glycocalyces- gelatinous sticky substance surrounding the outside of the cell composed of polysaccharides, polypeptides, or both. protect the cells from drying and can play a role in the ability of pathogens to survive and cause disease. 2 types: capsule and slime layer
distinguish capsules from slime layers (bacteria)
capsule: composed of organized repeating units of organic chemicals, firmly attached to cell surface. chemicals can resemble those in the human body preventing bacteria from being recognized as foreign
slime layer: loosely attached to cell surface (water soluble). sticky layer that allows prokaryotes to attach to surfaces as biofilms
discuss the structure and function of bacterial flagella
composed of filament, hook, and basal body. rotation propels bacterium through environment. bacteria move in response to stimuli so they can move in runs (counterclockwise) toward a positive stimulus and tumbles (clockwise) away from a negative stimulus
compare and contrast the structures and functions of fimbriae, pili, and flagella
fimbriae are shorter than flagella and there may be hundreds per cell. they are sticky, bristle-like projections composed of protein with adhesive tips. used by bacteria to adhere to one another and to other substances. some carry enzymes that detoxify metal ions. conduct electrical signals among cells in a biofilm.
pili: longer than fimbriae but shorter than flagella. bacteria typically only have 1. pili mediate the transfer of DNA from one cell to another (conjugation).
compare and contrast the cell walls and cell envelopes of gram-positive and gram-negative bacteria in terms of structure and gram staining
gram positive cell walls: thick layer of peptidoglycan, contain teichoic acids and lipoteichoic acids. acid-fast bacteria have walls with up to 60% mycolic acid (a long chain fatty acid)
gram negative cell wall: thin layer of peptidoglycan, asymmetric bilayer membrane. porins form channels through inner and outer leaflet which allows some molecules to freely pass across the outer membrane. LPS lipid A can be toxic. periplasmic space between the outer membrane and the cytoplasmic membrane
describe the clinical implications of the structure of the gram-negative cell envelope
the outer leaflet of the asymmetric bilayer membrane is composed of lipopolysaccharide (LPS). Lipid A can be toxic and can be released when antimicrobial drugs kill bacteria and may trigger fever, vasodilation, inflammation, shock, and blood clotting
explain the fluid mosaic model of membrane structure
The fluid mosaic model of the cell membrane is how scientists describe what the cell membrane looks and functions like, because it is made up of a bunch of different molecules that are distributed across the membrane. If you were to zoom in on the cell membrane, you would see a pattern of different types of molecules put together, also known as a mosaic. These molecules are constantly moving in two dimensions, in a fluid fashion, similar to icebergs floating in the ocean. The movement of the mosaic of molecules makes it impossible to form a completely impenetrable barrier.
describe the functions of a cytoplasmic membrane as they relate to permeability
separates the contents of the cell from the outside environment. they are selectively permeable- nutrients are brought into the cell and wastes are removed by either passive or active processes. maintains a concentration gradient.
compare and contrast the passive and active processes by which materials cross a cytoplasmic membrane
passive: electrochemical gradient provides the source of energy; the cell doesn’t expend its energy reserve. includes diffusion, facilitated diffusion, and osmosis.
diffusion- high to low concentration. no energy output by cell. only small chemicals or lipid soluble through phospholipid bilayer.
facilitated diffusion- integral proteins act as channels or carriers to allow certain molecules to diffuse down their concentration gradients. nonspecific (allow a range of chemicals) and specific (requires permeases that are more specific and only carry certain substrates)
osmosis- diffusion of water across a selectively permeable membrane. high water to low water or low solute to high solute
active: requires cell to expend energy stored in ATP and utilizes transmembrane permease proteins including uniport, antiport, and symport.
distinguish among isotonic, hypertonic, and hypotonic solutions
isotonic- solutions on either side of selectively permeable membrane have same concentration
hypertonic- solution with higher concentration of solutes is hypertonic to the other
hypotonic- solution with lower concentration of solutes is hypotonic to the other
describe the bacterial cytoplasm and its basic contents
gelatinous material inside cell. composed of cytosol, inclusions, ribosomes, cytoskeleton in many cells, and endospores in some cells
describe the structure and function of prokaryotic and eukaryotic ribosomes
prokaryotic ribosomes (bacterial) are the site of protein synthesis in cells. bacteria have 70s ribosomes composed of 30s and 50s subunits.
eukaryotic ribosomes are larger than prokaryotic ribosomes. have 80s ribosomes composed of 60s and 40s subunits.
describe the composition, function, and importance of eukaryotic glycocalyces
present only on animal and protozoan cells that do not have cell walls. help anchor animal cells to each other, strengthen cell surface, provide some protection against dehydration and function in cell-to-cell recognition and communication
compare and contrast prokaryotic and eukaryotic cell walls and cytoplasmic membranes
prokaryotic cell walls: most cells are surrounded by structural cell wall that provides shape and protects from osmotic forces. bacterial cell walls have peptidoglycan but archaeal cell walls do not.
eukaryotic cell walls: fungi, algae, plants, and some protozoa have cell walls but no glycocalyx. composed of various polysaccharides, no peptidoglycan. protect from environment, anchors neighboring cells together, provides shape and support against osmotic pressure.
prokaryotic cytoplasmic membranes: are a fluid mosaic of phospholipids and proteins. proteins act as recognition molecules, enzymes, receptors, carriers, or channels. bacterial- composed of phospholipids and associated proteins. basic structure is phospholipid bilayer.
archaeal- An archaeal cytoplasmic membrane maintains electrical and chemical gradients in the cell. It also functions to control the import and export of substances from the cell using membrane proteins as ports and pumps, just as proteins are used in bacterial cytoplasmic membranes
eukaryotic cytoplasmic membrane: all eukaryotes have a cytoplasmic membrane. is a fluid mosaic of phospholipids and proteins. contains steroid lipids to help maintain fluidity. contains assemblages of lipids and proteins. attach chains of sugar molecules to the other surfaces of lipids and proteins in the cytoplasmic membrane
