Prokaryotes Study Guide Midterm 3 - Egan BISC-120

What is a prokaryote?

a type of cell lacking a membrane-enclosed nucleus and membrane-enclose organelle; they are unicellular and small

Prokaryotes achieve:

all of an organism’s life’s functions within a single cell

What are 3 characteristics of prokaryotes?

• circular chromosome

• genes organized into operons

• translation of mRNA into proteins begins before transcription of DNA into mRNA is complete

• organelles - cytoskeleton - prokaryotic binary fission

What domains do prokaryotes make up?

bacteria & archaea

What enables prokaryotes to reach huge population sizes and thrive in diverse environments? (4 answers)

• Small size and rapid reproduction 

• mutations

• diverse adaptations

• rapid evolution

What is the usual size of a prokaryote?

0.5-5 𝜇m

What are 3 typical shapes of a prokaryote?

spherical (cocci), rod-shaped (bacilli), and spiral

What are bacterial cell walls made up of?

a modified sugar polymer called peptidoglycan

What are archaeal walls made up of?

a variety of polysaccharides and proteins

Gram-positive bacteria have:

simpler walls with a large amount of peptidoglycanG

Gram-negative bacteria have:

less peptidoglycan but have an outer membrane that contains lipopolysaccharides

What is a capsule & slime layer respectively?

a sticky layer of polysaccharide or protein surround the cell wall, called capsule if dense and well-defined, or slime layer if not

What do capsules/slime layers enable?

adherence to substrate or other individuals, prevent dehydration, and protect cell from host’s immune system

What are endospores?

Endospores are inactive bacteria that can withstand extreme conditions and remain viable for centuries

What are fimbriae?

hairlike appendages that allow prokaryotes to stick to their substrate or other individuals

What are pili?

longer than fimbriae an function to pull cells together enabling the exchange of DNA

What is taxis?

the ability to move toward or away from a stimulus

What is the most common structure used by prokaryotes for movement?

Flagella

Where is the chromosome located in a prokaryote?

the nuclei region

What are plasmids?

They are independently replicating DNA, physically separated and carry genes that benefit the survival of the organism

What are three factors that contribute to high levels of genetic diversity in prokaryotes?

rapid reproduction, mutation, and genetic recombination

How do prokaryotes reproduce quickly?

By binary fission

What happens during binary fission?

chromosomes are duplicated and origins move to the end of each cell, splitting and resulting in two daughter cells

How do differences arise after binary fission?

mutations

What are 3 ways genetic recombination occurs in prokaryotes?

transformation, transduction, and conjugation?

What happens in transformation?

prokaryotic cells incorporate foreign DNA taken up from their surroundings

What state must bacteria be in for transformation?

a state of competence (more permeable), which may occur as a time-limited response to environmental conditions

What happens in transduction?

phages carry prokaryotic genes from one host cell to another as an unintended result

What happens in conjugation?

the process in which DNA is transferred between two prokaryotic cells

In E. coli, how does conjugation occur?

a plus of the donor cell attaches to the recipient and retracts, pulling two cells together. DNA is transferred through a “mating bridge”

What piece of DNA is required to produce pili?

F factor

F plasmids (F+) function as?

DNA donors —- F factor encodes genes for sexual pili and activate DNA synthesis

What can an F+ cell convert?

An F+ cell can convert F- cell to F+ if an entire F plasmid transfers to an F-, otherwise, if it’s partial, the recipient cell will be recombinant but remain F-.

What do Hfr cells mean, and what do they function as?

High Frequency of Recombination cells, and they function as donors during reconjugation

Homologous segments of chromosomal DNA do what during conjugation?

the Hfr cells recombines with that of the F- cells and create genetic variants

What is metabolism in prokaryotes?

Metabolism is the totality of an organism’s chemical reactionsM

Metabolism is an _____.

emergent property of life arising from interactions between molecules within a cellMe

How do metabolic pathways begin and end?

They begin with a specific molecule (substrate or reactant) and end with a product

What are anabolic pathways?

consume energy to build complex molecules from simpler ones. ex: photosynthesis

What are catabolic pathways?

They release energy by breaking down complex molecules into simpler compounds. ex: cellular respiration

What can photoautotrophic bacteria perform?

Oxygenic photosynthesis or anoxygenic photosynthesis.

What is photosynthesis?

they trap light energy and convert it into chemical energy

What is chemosynthesis?

use inorganic energy sources to synthesize larger molecules

What do chemoautotrophs feed on, and what are most of them?

They feed on chemicals that are good electron donors, and most are extremophiles

What are chemoheterotrophs?

they obtain carbon from other living organisms and use cellular respiration

photoheterotrophs can’t use CO₂, so what do they do?

They must break down larger organic molecules to obtain energy

O₂ to obligate aerobes?

O₂ is required for cellular respiration

O₂ for obligate anaerobes?

They are poisoned by O₂ and live by fermentation or use substances other than O₂ for anaerobic respiration

O₂ for facultative anaerobes?

use O₂ if present for fermentation or anaerobic respiration

What is metagenomics?

A DNA sequencing approach that lets scientists identify new species of bacteria and archaea, including ones that can’t be cultured

What are proteobacteria?

a phylum of gram-negative bacteria, aka phylum pseudomonadota

What do proteobacteria consist of?

anoxygenic photoautotrophs, chemoautotrophs, and heterotrophs

Gonorrhea and stomach ulcers are a result of what proteobacteria?

Heterotrophic, as they include several pathogens

What do phylum chlamydiota parasitize?

All species parasitize animal cells and have Gram-negative walls lacking peptidoglycan

What make up phylum chlamydiota?

They are gram-negative anaerobic bacteria that replicate inside eukaryotic cells

What are spirochaetota?

they are helical, gram-negative, heterotrophs that spiral through the environment by rotating internal filaments

What are cyanobacteria?

they are gram-negative photoautotrophs; ancestors responsible for The Great Oxidation Event

What is TACK?

TACK is a supergroup composed of the remaining, closely-related clades of archaea

Why are lokiarchaeotes important?

recently discovered and closely related to the TACK archaea and may represent asgard archaea of the eukaryotes; it introduces another possible shuffling of the phylogenetic tree of life

What is symbiosis?

A long-term biological interaction between two different species that live in close physical and/or physiological contact with each other.

What is a symbiont?

the smaller of the pair in symbiosis

What is a host?

the larger of the pair in symbiosis, and can be viewed as habitats

What do symbiosis play a major role in?

the recycling of chemical elements between living and nonliving

What is commensalism?

symbiotic relationship where one organism benefits and the other is unaffected.

What is parasitism?

symbiotic relationship where the organism benefits at the expense of the host.

What is mutualism?

a symbiotic relationship where all organisms benefit

What happens in the decomposition cycle?

the cycle mineralize nutrients into compounds that can be taken up by other organisms

What is nitrogen-fixing?

it transforms atmospheric nitrogen into forms available to other organisms

What is microbiota?

community of microorganisms that live in a particular environment (ex: human skin)

How are microorganisms beneficial to humans?

they act as a physical barrier to prevent the invasion of pathogens (competitive exclusion)

What is CRISPR?

A gene-altering tool