CHAPTER 3 Flashcards
What are the characteristics of life?
growth reproduction responsiveness metabolism cellular structure
What are characteristics of prokaryotes?
lack nucleus
lack various internal structures bound with phospholipid membranes
are typically 1.0 um in diameter or smaller
composed of bacteria and archaea
What are characteristics of eukaryotes?
have nucleus have internal membrane-bound organelles are typically 10-100 um in diameter more complex structure composed of algae, protozoa, fungi, animals, and plants
What are glycocalyces?
gelatinous, sticky substance surrounding the outside of the cell (bacterial cells)
composed of polysaccharides, polypeptides, or both
What are the two types of glycocalyces? Describe them.
Capsule- composed of organized repeating units of organic material, firmly attached to cell structure, may prevent bacteria from being recognized by host
Slime layer- loosely attached to cell surface, water-soluble, sticky layer allows prokaryotes to attach to surfaces
Functions of the glycocalyx?
protect cells from dehydration and nutrient loss
inhibit killing by WBCs by phagocytosis
attachment- formation of biofilms
What makes biofilms a health issue?
Biofilms have been shown to develop on medical device surfaces, and dispersal of single and clustered cells implies a significant risk of microbial dissemination within the host and increased risk of infection
What is EPS and how does it protect cells?
extracellular polymeric substance
cells use them to attach to themselves and the target environment
protects cells by preventing dessication, facilitates communication between cells in the biofilm, enables adherence and provides nutrients
3 parts in biofilm formation?
Attachment- cells attach to surface
Growth- sticky matrix made by biofilm encourages adhesion
Detachment- planktonic (free-floating) cells can be released from biofilm
Characteristics of flagella
responsible for movement
long structures that extend beyond cell surface
not present on all bacteria
Function of flagella
rotation propels bacterium through environment, rotation is reversible; bacteria move in response to stimuli- runs and tumbles
Flagellar structure
Filament- long, thin, helical structure
Hook- curved sheath
Basal Body- stacks of rings that anchor filament and hook to cell wall
Flagellar arrangements
monotrichous- single flagellum at one end
Lophotrichous- small bunches emerging from same site
Amphitrichous- flagella at both ends of cell
Peritrichous- flagella dispersed over surface of cell
Endoflagella of spirochetes chararcteristics
spiral tightly around cell
corkscrew motion
form axial filament that wraps around cell between cytoplasmic membrane and outer membrane
Characteristics of Fimbriae
sticky, bristle like projections
used by bacteria to adhere to one another and to substances in environment
shorter than flagella
serve an important function in biofilms
Characteristics of Pili
special type of fimbriae
longer than fimbriae but shorter than flagella
bacteria typically have only one or two per cell
transfer DNA from one cell to another (conjugation)
Characteristics of bacteria cell walls
provide structure and shape and protect cell from osmotic forces
assist some cells in attaching to other cells or in resisting antimicrobial drugs
gives bacteria characteristic shapes
composed of peptidoglycan
gram-positive or gram-negative
Shapes of Bacteria
cocci- spherical
bacilli- rod
curved shapes- vibrious, spirilla, spirochaetes
Peptidoglycan is a polymer of what?
NAG + NAM
disaccharide
joined by glycosidic bond
side chains of amino acids form peptides and link to other disaccharides to form framework of peptidoglycan on bacteria
Gram-Positive bacterial cell wall characteristics
thick layer of peptidoglycan
contain teichoic acids and lipoteichoic acids
appear PURPLE following gram staining
up to 60% mycolic acid in acid-fast bacteria helps cells survive desiccation
Gram-Negative bacterial cell wall characteristics
think layer of peptidoglycan
PINK after gram staining
bilayer membrane outside peptidoglycan contains phospholipids, proteins, and lipopolysaccharides (LPS)
may impede tx of disease
What is Lipid A?
portion of LPS and can cause fever, vasodilation, inflammation, shock, and blood clotting
What bacterial groups lack typical cell wall structure?
mycobacterium and nocardia
gram-positive cell wall structure with waxy lipid mycolic acid (cord factor)
How is bacteria without cell walls stabilized?
by sterols, pleomorphic (existing in different shapes)
ex. mycoplasma pneumoniae
structure of bacterial cytoplasmic membranes
referred to as phospholipid bilayer, has integral and peripheral proteins
What are the functions of the cytoplasmic membrane?
energy storage
harvest light energy in photosynthetic bacteria
selectively permeable
naturally impermeable to most substances
proteins allow substances to cross membrane
maintain concentration and electrical gradient
passive (no ATP needed) and active (ATP needed) processes
What are the passive processes?
diffusion
facilitated diffusion
osmosis
What are the active processes?
active transport
group translocation
What is diffusion?
high concentration to low concentration
What is facilitated diffusion?
high to low concentration but requires protein carrier or channel. Can be specific or nonspecific
What is osmosis?
diffusion of free water across a semipermeable membrane from an area of high concentration to an area of low concentration until the solute concentration is equal on both sides
3 mechanisms of active transport?
uniport, antiport, coupled transport
What is group translocation?
substance is chemically modified during transport
only in bacteria
What is active transport?
ATP-dependent carrier proteins bring substances into cell
What is cytoplasm?
liquid portion of cytoplasm
mostly water
contains cell’s DNA in region called nucleotide
What are inclusions?
may include reserve deposits of chemicals
What are endospores?
unique structure produced by some bacteria
defensive strategy against unfavorable conditions
resistant to extreme conditions such as heat, radiation, and chemicals
What are ribosomes?
sites of protein synthesis
composed of polypeptides and ribosomal RNA
What is the cytoskeleton?
composed of 3 or 4 types of protein fibers
can play different roles in the cell- cell division, cell shape, segregate DNA molecules, move through the environment
What is the external structure of archaea composed of?
glycocalyces, flagella, fimbriae and hami
Characteristics of archaeal cell walls?
most have cell walls, but not composed of peptidoglycan. Instead, contain variety of specialized polysaccharides and proteins
Characteristics of Archaeal cytoplasm
similar to bacterial cytoplasm- 70s ribosomes, fibrous cytoskeleton, circular DNA
differs from bacterial cytoplasm- different ribosomal proteins, different metabolic enzymes to make RNA, genetic code more similar to eukaryotes
External structure of eukaryotic cells
glycocalyces- not as organized as prokaryotic capsules
help anchor animal cells to each other
strength cell surface
provide protection against dehydration
function in cell to cell recognition and communication
Cell Walls in Eukaryotic Cells
fungi, algae, plants, and some protozoa has cell walls
composed of various polysaccharides-cellulose found in plant cells walls, fungal cells walls composed of cellulose, chitin, and glucomannan, algal walls composed of variety
Cytoplasmic membrane in eukaryotic cells
present in all eukaryotic cells
are a fluid mosaic of phospholipids and proteins
contain steroid lipids to help maintain fluidity
contain regions of lipids and proteins called membrane rafts
control movement into and out of cell
Function of lipid rafts
signaling and/or transport of membrane proteins
Flagella characteristics of eukaryotes
flagella
structure- enclosed within cytoplasmic membrane, shaft composed of tubulin arranged to form microtubules, filaments anchored to cell by basal body, hook
may be single or multiple
function- undulate rhythmically
Characteristics of cilia on eukaryotes
shorter and more numerous than flagella
coordinated beating propels cells through environment
Ribsome characteristics in eukaryotes
protein synthesis, largers than prokaryotic ribosomes, composed of 60s and 40s subunits
cytoskeleton of eukaryotes
anchors organelles in cell
extensive networks of fibers and tubules
produces basic shape of cell
made up of tubulin microtubules, actin microfilaments, and intermediate filamens
centrioles and centrisomes in eukaryotes
play role in mitosis, cytokinesis, and formation of flagella and cilia
centrosome is region of cytoplasm where centrioles are found
not found in all eukaryotic cells
nucleus characteristics
often largest organelle in cell, contains most of cells DNA
semiliquid portion called nucleoplasm
RNA synthesized in nucleoli
surrounded by nuclear envelope
endoplasmic reticulum characteristics
netlike arrangement of flattened, hollow tubules continuous with nuclear envelope
functions as transport system
smooth ER and rough ER
golgi body characteristics
receives, processes, and packages large molecules for export of cell
packages molecules in secretory vesicles that fuse with cytoplasmic membrane
lysosomes, peroxisomes, vacuoles, and vesicles
store and transfer chemicals within cells
may store nutrients
lysosomes contain catabolic enzymes
peroxisomes contain enzymes that degrade poisonous wastes
mitochondria
have 2 membranes composed of phospholipid bilayer
produce most of cells ATP
interior matrix contains 70s ribosomes and a circular molecule of DNA
chloroplasts
light-harvesting structures found in photosynthetic eukaryotes
use light energy to produce ATP
Endosymbiotic theory
proposed to explain why mitochondria and chloroplasts have 70s ribosomes, circular DNA, and two membranes
eukaryotes formed from the union of small aerobic prokaryotes with larger anaerobic prokaryotes
smaller prokaryotes became internal parasites
