MCB 4403 EXAM 1

domains of life

archea, bacteria, eukaryota

cell envelope in prok cells

plasma membrane + cell wall

T/F: the cell wall is closer to the outside of the cell than the plasma membrane

T

where is the nucleiod within a prok cell

within the cytoplasm, no distinct membrane

components of nucleoid

DNA (usually circular) , RNA, protein

components of 70s ribosome

50s and 30s subunit

polysome

a chain of ribosomes on the same mRNA

how do euk cells make up for a worse SA to volume ratio?

increase SA by having endomembranes (ex organelles)

what allows for different conditions within different organelles in euk cells?

separation into zones/ compartments by endomembranes

T/F: bacteria perform endocytosis and exocytosis

F; although recent evidence has exhibited prokaryotic exocytosis

unique features of chlorplast and mitochondria

double membrane, 70s rRNA, divide by binary fission- like process, has its own DNA

can eukaryotes have cell walls?

yes- plants and fungi

algae and plant cell wall polymer

cellulose

fungi and insect cell wall polymer

chitin (modified 6C sugar with amide group)

archea cell wall polymer

pseudomurein

pseudomurein components

NAG + NAT, short peptide chain, B 1,3 linkages

bacteria cell wall polymer

peptidoglycan

peptidoglycan components

NAG+NAM, short peptides attached to NAM, B 1,4 bonds

gram + cell wall components

very thick peptidoglycan layer, teichoic acids crosslinked to peptidoglycan

teichoic acid results

acidic polysacc, makes surface negatively charged and hydrophobic, increases heat and osmotic stress resistance

gram - cell wall components

inner membrane→ thin peptidoglycan layer → outermembrane composed of inner phospholipid leaflet and outer LPS leaflet

LPS components

lipid A, core polysacc, O specific side chain

gram - porins purpose

selective passage into the cell

gram - lipoproteins purpose

cross link peptidoglycan to outer membrane

gram - periplasmic space and its role

space between inner and outer membrane, this is where metabolic activity occurs

T/F: the outer membrane in gram - cells serves a role in respiration

F, the periplasmic space is site of metabolic activity

what cell type flagella can run (counterclockwise) and tumble (clockwise)?

bacteria

what drives flagella rotation?

proton motive force (PMF)

major difference between flagella and pili

flagella penetrates to the plasma membrane and functions as motility, while pili anchor bacterium to surfaces

sex pilus

type of pili used for conjugation; transfers genetic info between cells

what is a glycocalyx?

general term for a polysacc layer outside the cell wall

2 major forms of glycocalyx

capsule and slime layer

capsule features

defined and thick layer outside bacterial cell walls, offers protection against certain pathogenic bacteria

slime layer features

loosely bound layer outside bacterial cell walls, aids in surface attachment and protection

biofilm

a protective matrix involved in bacterial attachment, includes a whole community of microorganisms

T/F: both slime layers and capsules aid in biofilm formation

T

what does an endospore include

the cells genome and ribosomes

why are endospores resistant

they have a thick coat surrounding it to protect from environmental extremes

how do endospores regenerate bacteria

they germinate into new cells when conditions become favorable

T/F: all protozoans and algae have cell walls. explain

F, some are instead protected by flexible strips of protein called pellicle

what differentiates flagella in eukaryotes v prok?

they beat in waves, not running+ tumbling

cilia

similar structure as flagella, just shorter

growth factors

compounds required for growth that many microbes cannot synthesize (ex. amino acids, vitamins)

where do microbes obtain growth factors

from environment (or medium)

fastidious organism

has complex or specific nutritional requirements, making it more difficult to grow

terms for how organisms obtain CARBON required for cell reactions

heterotroph (from organic molecules) or autotroph (from inorganic molecules)

heterotroph examples

humans, all fungi + protozoans, and most bacteria

autotroph examples

algae, plants, some bacteria

terms for how organisms obtain ENERGY required for cell reactions

chemotroph (from inorganic sources) or phototroph (from light)

most heterotrophs are…

chemoheterotrophs

terms for how organisms obtain their source of ELECTRONS to drive energy systems

lithotrophs (inorganic e- donor, ex H2S) and organotrophs (organic e- donor, ex glucose)

are all autotrophs phototrophs?

NO

axenic culture

“pure” culture with one species

why is agar preferred as a growth medium?

it stays solid in typical (warm) incubation conditions, most microorganisms cannot digest it

why does agar work in pour plate method

agar melts at a high temp but stays liquid until cooled considerably, so there is a window where you can have agar at a temp sustainable to keeping bacteria alive

streak plate technique

produces single colonies from unknown [ ], does not require dilution

individual cells or CFUs produce…

isolated colonies

pour plate technique

technique to isolate microbes into single colonies, uses diluted cultures, microbes are mixed with molten agar and embedded in an on top

utility of pour plate technique

isolating microbes that are sensitive to atm O₂

undefined media, examples, and benefit

variable composition, ex blood, yeast, tap water, beef broth, cheap to make

defined medium and examples

known chem composition, ex glucose, distilled water, NaCl

what are fastidious organisms often grown on? why?

undefined media, inc likelihood that it meets their requirements

differential media

differentiates organisms by eye (ex. a colored indicator to identify colonies based on color)

selective media

selectively grow a particular organism while inhibiting growth of others

explain how antibiotics can act as selective media

they can allow resistant organisms to grow (select), while inhibiting organisms that are susceptible to the antibiotic

enrichment media

use of a medium that favors growth of a desired organism present in low numbers

why might enrichment media be best for soil or stool samples?

stool and soil samples contain many microorganisms, and the organism of interest may be present in small numbers

why measure microbial growth?

to know how it grows, how to limit growth, modifying/ developing enzymes, learn role in microbial communites

direct microscopic examination

directly count cells, very time consuming but accurate, need to know dilution factor and vol. liq used

cell sorting

way to quantify microbial growth using a cell sorter (laser), time consuming but accurate, need to know # of counted cells dilution factor and vol liq used

counting viable cells

a way to measure microbial growth where each colony= 1CFU (with reasoning that colonies only grow from viable cells), need to do serial dilution, less time consuming

optical density/ turbidity

use of spectrophotometer to measure turbidity, optical density linear ONLY at low cell densities, VERY fast but less accurate

lag phase

cells synthesize new enzymes to adapt to new environment

exponential/ log phase

cells growing at max rate allowed, not limited by resources

stationary phase

nutrients are limited, cell growth= cell death

death phase

nutrients near depletion, cell growth < cell death

explain why you might see diauxic growth

a microbes preferred nutrient source is depleted (ex glucose), so it goes through a lag phase while it synthesizes enzymes for the new best nutrient, exponential growth follows

list terms for optimal growth of organisms at temperatures from coldest to hottest

psychrophile (below 15C), mesophile (20-45C), thermophile (50-60C), extremophile (>100C)

examples of ways psychrophiles alter internal chemistry to allow for cold conditions

inc membrane fluidity with more unsaturated fatty acids, inc stabilizing IMFs within proteins

in static cultures, where would you see obligate aerobes? explain

at the top where O2 exposure is highest

where would you see obligate anaerobes in culture? explain

at the bottom, because they are killed by o2

where would you see facultative anaerobes in culture? explain

most at the top and some at the bottom; these thrive in O2 but can make due with fermentation/ anaerobic respiration

where would you see aerotolerant anaerobes in culture? explain

evenly spread because o2 has no effect on growth (indifferent)

where would you see microaerophiles in culture? explani

slightly below the top, o2 level has to be “just right” for growth

high osmotic pressure describes a ___ / ____ solution

hypertonic/ concentrated

low osmotic pressure describes a ____ / _____ solution

hypotonic/ dilute

what conditions lead to plasmolysis, why?

hypertonic solution, water leaves the cell to balance

what conditions lead to cell lysis/ bursting? why?

hypotonic solution, water coming into the cell because intracellular solute is higher. inc vol causes cell to burst

how do bacteria prevent from fluctuating in osmotic pressure

rigid cell walls (peptidoglycan)

how is fungal growth different than bacterial?

fungal growth via hyphae (tip growth), vs bacteria by binary fission

T/F: weak bonds release energy when forming stronger bond

true

how many atp does NADH generate in etc?

3 atp

how many atp does FADH2 generate in etc?

2 atp (enters etc at a later point)

glycolysis purpose

generate 2 3c pyruvate molecules

glycolysis input

2 atp, glucose

how many atp does glycolysis net? how does it do this?

2 net atp (4 total), substrate level phosphorylation

products of glycolysis

2 atp, 2 pyruvate, 2 NADH

where does glycolysis occur in prok?

prok cytosol

options of NADH after glycolysis

either go to etc or used in fermentation to regenerate NAD+ so glycolysis can continue

T/F: pyruvate enters krebs cycle. explain

F; must first be converted by coenzyme a to acetyl coA