Ch 3.1 Flashcards
What are the basic characteristics of living things?
Cellularity, growth by a simulation, metabolism, reproduction, and responsiveness.
Define natural selection, and explain how it leads to changes in species.
Natural selection is not the survival of the fittest. Individuals in populations are genetically varied, and depending on the environment, a particular individual will be able to produce more offspring at a higher rate than others, making their traits predominate in future generations.
Explain cell theory
- The cell is the basic unit of life.
- All living things are composed of one or more cells.
- All cells come from other cells (biogenesis).
Define prokaryotic cells
Two organisms in the domain; Archea and bacteria. Prokaryotic cells have no membrane bound nucleus and tend to be smaller than eukaryotic cells.
Typical structure of prokaryotic cells
Structure; capsule, cytoplasm, cell membrane, pili, flagella, ribosomes, plasmids, nucleoid region, and glycocalyx.
What doesn’t prokaryotic cells have?
Membrane bound nucleus, Mitochondria, Endoplasmic reticulum, and Golgi bodies.
Glycocalyx
(Sugar cup)
Function; protect the cell/allow for attachment
Composed of; polysaccharides/proteins, or both. (External structure).
Capsule
(Type of glycocalyx)
Firmly attached to cell surface, in some pathogens, and protects from immune cells.
Slime layer
(Type of glycocalyx)
Loosely attached, doesn’t really protect from immune cells, but holds more water, so it attaches to cell walls and protects against dehydration.
Motility
Ability to move through the environment.
(External structure)
Flagellum
Propels cell in environment. Consist of three parts; Basal body, hook, and filament. (External structure).
Filament
Part of flagellum, it is a long, hollow shaft made of many flagellin (protein). If it needs to get longer, they just send more flagellin to build the cell. Can rotate 360°.
Basal body
Part of flagellum. Microtubular structure that provide the template for the nine-fold symmetry upon which the cilium is assembled.
Hook
Part of flagellum. Spins and creates bend, and operates like propeller.
Filament
Part of flagellum. Made up of microtubules, actin filaments, and intermediate filaments. These structures give the cell its shape and help organize the cell’s parts. In addition, they provide a basis for movement and cell division.
Polar
(Flagellar arrangement)
Flagella at one or both ends of the cell.
Monotrichous
Only one flagellum at one end of the cell.
Lophotrichous
Tuft/multiple flagellum together at one end of the cell.
Amphitrichous
One or more flagellum at both ends of the cell.
Peritrichous
flagellum cover the cell perimeter.
“Run and tumble”
Run; movement in a straight line, occurs when flagellum rotates counterclockwise. Tufts of flagella will bundle and rotate together.
Tumble; abrupt, random changes in direction when flagellum rotates clockwise. Tufts of flagella will become unbundled.
Taxis
Movement in response to stimulus (external environment)
Require cell surface receptors (integral in peripheral membrane proteins)
Chemotaxis
Chemical
Phototaxis
Light
Magnetotaxis
Magnetic field
Geotaxis
Gravity
Positive taxis and negative taxis
Positive taxis; movement towards stimulus, increases the number of runs (ccw)
Negative taxis; movement away from stimulus, increases the number of tumbles (random direction changes)
Fimbriae and pili
Non-metal structures used for attachment.
Pili
Longer than fimbrae, shorter than flagella, hollow tube used for attachment to surfaces or to other cells. Most common is the sex pilus.
Fimbrae
Short, numerous bristle, like surface projections that are made of protein. Stick cells to one another or to a surface (biofilms) or to a host cell (pathogens).
Importance of cell walls in bacteria
Provide structure, shape, protect from osmotic forces, aid in attachment, and aid in a eluding antimicrobial drugs.
Animal cells do not have cell walls?
True
Bacteria and Archaea have different cell wall chemistry?
True
What are bacterial walls composed of?
Composed of the sugar molecule peptidoglycan. Long strings of two alternating sugars; N-Acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
Peptidoglycan
For amino acid linking (proteins) and NAG and NAM together (sugars).
Stain used to identify whether a bacteria is gram-positive bacteria/negative bacteria
Crystal violet
If the organism can hold the purple stain, is it gram-positive or gram-negative?
Gram positive - thick cell membrane
gram-positive
Has a thick cell membrane wall (peptidoglycan), and has teichoic and lipoteichoic acids.
Teichoic acids
Help ions pass through wall.
Lipoteichoic acids
Link cell wall to cell membrane.
acid fast bacteria
Bacteria has an additional layer of mycolic acid which is very waxy and hydrophobic coding, which can prevent staining with Crystal light, making them appear pink (gram negative).
How to tell that a acid fast bacteria is gram-positive?
Use carbol fusion and then wash with decolorizer (acid). If stained bright pink color, this means that it is acid fast and therefore gram positive.
Gram-negative
Thin membrane wall (peptidoglycan) and has extra membrane -outer layer.
What are the components of the gram-negative outer membrane?
Phospholipids, channel proteins, lipopolysaccharide (lipid A + polysaccharide)
Endotoxin
Aka lipid A, released when Graham negative bacteria are killed, which can cause fever, vasodilation, shock, and blood clotting.
Why would antibiotics possibly not work on Gram-negative bacteria?
Antibiotics may not have an effects because they may not be able to penetrate outer cell membrane walls.
Spherical cell shape
Coccus (cocci)
Diplococci- 2
Streptococci- chain
Cocci specific; tetrads (4), sarcinae (8/cube), staphylo (a bunch)
Oblong, rod
Bacillus (bacilli)
Diplobacilli
Streptobacilli
Bacilli specific; v-shaped (cells fail to divided and break) and palisade (side by side/stacked)
Curved
Vibrio
Spiral
Spirillum (stiff)
Spirochete (flexible)
Pleomorphic
Varies in shape and size; doesn’t fit into other categories.
Do all prokaryotic cells have glycocalyces, flagella and fimbriae and pilli?
No, these are just structures that are unique to prokaryotes, not found in eukaryotes.
