Bio 1722 Exam 3 Flashcards

Virus

An infectious particle consisting of little more than one or more molecules of nucleic acid enclosed in a protein coat. Some also contain a membraneous (lipid) coat

Capsid

The protein shell that encloses the viral genome

Made up of subunits called capsomeres

What kind of genetic material does the viral genome contain

Either double/single stranded DNA or double/single stranded RNA

What is a Viral envelope

An envelope around viruses that help them infect hosts. Created by taking parts of the host cell’s membrane and using it to form their own membrane

Bacteriophages (Also called phages)

Complex viruses that infect bacteria

What kind of genetic material does COVID-19 contain

Single stranded RNA

Host Range

The number of host species that a virus can infect

T-Even bacteriophages

Use their tail apparatus to inject DNA into the bacterial host

Enveloped viruses

Enter host cells by fusing their viral envelope with the host’s plasma membrane

How do viruses replicate

By inserting their genetic material into the host cell’s genetic material and then replicating when the gene that the virus has inserted their genetic material into has been activated

Lytic Cycle

A phage replicative cycle that culminates in the death of the host cell

Produces new phages and lyses the host cell wall, releasing the viruses and destroying the cell

Virulent Phage

A phage that reproduces only through the lytic cycle

Lysogenic Cycle

Phage genetic material is inserted into the host cell’s genetic material. Host cell often replicates multiple times to create many daughter cells from just one cell. Eventually, the phage’s genetic material is activated due to some kind of signal and the lytic cycle is activated which gives rise to many phages

Temperate Phages

Phages that use both the lytic and lysogenic cycles

Prophage

The viral DNA that is inserted into a host cell’s DNA

Bacterial defenses against phages

Natural selection favors mutant bacteria with surface proteins that are not recognized by a particular phage. Basically, natural selection favors bacteria that mutate to contain surface receptors that can’t bond with the receptors on viruses

Phage DNA is often identified as foreign and cut up by bacterial restriction enzymes
The bacterium’s own DNA is methylated in a way that prevents attack by its own restriction enzymes

Purpose of CRISPR-Cas (Clustered Regularly Interspaced Short Palindromic repeats and nuclease enzymes called Cas) system

To defend against phages. Works by transcribing the CRISPR region of DNA along with the phage DNA. Once it has been transcribed into RNA, it binds to a Cas protein that cuts out the phage DNA, leaving only the CRISPR DNA. The phage DNA is degraded and can no longer be used to replicate.

Basically cuts the phage RNA out of the RNA strand so that it can no longer be used to replicate phages

Characteristics that allow prokaryotes to thrive in diverse environments

• Small size + rapid reproduction

• High genetic diversity through mutation

• Bacteria sharing plasmids with other bacteria to increase potential diversity

• Rapid evolution of diverse adaptations

Prokaryotes

Single-celled organisms in the domains Bacteria and Archaea

Chemical + Physical processes on early Earth necessary for the synthesis of simple cells

1. Abiotic synthesis of small organic molecules

2. Joining of small molecuyles into macromolecules

3. Packaging of molecules into protocells, droplets with membrane that maintain consistent internal chemistry

4. Creation of self-replicating molecules

What did Oparin and Haldane do

They hypothesized that the early environment was a reducing environment

What did Miller and Urey do

They showed experimentally that abiotic synthesis of organic molecules was possible in a reducing atmosphere. Created a self-contained experiment simulating the conditions of the earth billions of years ago to see if they could create life from that.

Protocells

Fluid-filled vesicles enclosed with a membrane-like structure

Montmorillonite clay

Increases the rate of vesicle formation by concentrating molecules on its surface This is because lipids and other organic molecules can spontaneously form vesicles with a lipid bilayer in water so the higher the concentration of molecules on its surface, the higher the rate of vesicle formation

Ribozymes

RNA molecules that can catalyze reactions; some are also self-replicating

First genetic material

Likely RNA

Stromatolites

Layered rocks that formed from the activities of prokaryotes, formed by cyanobacteria and other photosynthetic bacteria

Size of prokaryotic cells

0.5-5 µm(micrometers)

Cell wall

Used to protect and maintain cell shape

Bacterial cell walls

Contain peptidoglycan, a network of modified sugars and polypeptides

Archaeal cell walls

Contain polysacchardies and proteins but lack peptidoglycan

Gram-positive bacteria

Simpler cell walls composed of a thick layer of peptidoglycan

Stains a darker color

Gram-negative bacteria

They have less peptidoglycan and an outer membrane with lipopolysaccharide

Stains a lighter color

Why are some bacteria more resistant to antibiotics than others

Many antibiotics target peptidoglycan in a bacterial cell wall to destroy the bacteria however, the outer-membrane protects the peptidoglycan layer in gram-negative bacteria, increasing their antibiotic resistance by preventing the antibiotics from reaching the peptidoglycan

Capsule

A sticky, protective outer layer in prokaryotes that allow them to adhere to the substrate or each other

Endospores

Resistant cells developed by bacteria when water or nutrients are lacking so that the bacteria can survive

Dormant cells that can remain viable for centuries or survive extreme conditions

Fimbriae

Hairlike appendages used by prokaryotes to stick to the substrate or to other cells

Pili

Longer, less numerous appendages that are used to pull prokaryotes together during DNA transfer between cells

Endosymbiosis

When an ancestral cell engulfed an aerobic bacterium forming an early eukaryote

Basically where one life form engulfs another one and over time, the two cells merge and share the same functions

4 main supergroups that evolved using endosymbiosis from heterotrphic and photosynthetic eukaryotes

• Excavata

• SAR

• Archaea

• Unikonta

Examples of Endosymbiosis

Mitochondria being the descendant of some kind of ATP producing bacterium

Chloroplasts being the descendant of some kind of photosynthetic bacterium

Protist

Unicellular eukaryotes

Algae

Photosynthetic protists

Endosymbiont

Cell that lives within a host cell

Serial endosymbiosis hypothesis

The process that describes the repeated acquisition of endosymbionts, one after another, leading to the evolution of complex eukaryotic cells

ex. That mitochondria and plastids evolved sequentially with mitochondria evolving first and plastids evolving second

Secondary Endosymbiosis

When eukaryotic algal cells were ingested by heterotrophic eukaryotes

Steps in the Origin of Multicellularity

Involved many small steps 

Transition to multicellularity involved having new ways of using proteins encoded by genes

Few novel genes actually had to evolve 

Excavata

1 of the main supergroups of Eukaryotes

3 Clades - Parabasalids, Diplomonads and Euglenozoans

Includes parasites like Giardia intestinalis

SAR

1 of the main supergroups of Eukaryotes

Includes three diverse clades - Stramenopila Alveolata and Rhizaria

Includes important photosynthetic organisms like diatoms 

Diatom are algae and contain a silica case

Ex. Plasmodium, which cause malaria

Archaeaplastida

Includes photosynthetic species of red algae, green algae and plants

Algae include unicellular, colonial and multicellular specias known as seaweeds

Ex. Volvox - A simple multicellular green algae that forms a ball of sterile cells surrounding groups of reproduction cells

Unikonta

Includes amoebas, animals, fungi and non-amoeba protists closely related to animals or fungi

Amoebas in this group have lobe or tube shaped pseudopodia

Ex. Amoeba proteus

Protists

Most are unicellular while others are colonial or multicellular

Most are aquatic but can be found anywhere were

Nutritionally diverse and consume food through photoautotrophy, heterotrophy and mixotrophy

Form the base of the food web

Producers

Use energy from light or inorganic chemicals to convert CO2 to organic compounds

Consumers

Depend on producers for food by eating hem or eating animals that eat them

Mycorrhizae

Symbiotic relationship between fungi and plants

Fungi help plants by increasing nutrient absorption, specifically the delivery of things like phosphate ions and other minerals, while the plant provides the fungi with organic nutrients like carbohydrates

Aided the transition of plants and fungi from water to land

How due fungi eat things

By secreting hydrolytic enzymes into their surroundings allowing them to break down molecules so that they can eat them

Hyphae

Branched filaments that make up the mycelium in mushrooms

Arbuscular mycorrhizal fungi (Endomycorrhizae)

Type of fungi that extend hyphae into root cell walls but don’t penetrate the membrane

Ectomycorrhizal fungi

Grow around the root surface and into the extracellular spaces of the root cortex

Plasmogamy

The union of cytoplasm from two different haploid mycelia (In fungi)

Karyogamy

Fusion of haploid nuclei to form diploid cells (In fungi)

Vascular tissue

COmposed of cells joined into tubes that transport water and nutrients throughout the plant

Bryophytes

Only living group of plants that lack vascular tissue

Also lack true roots or leaves

Contain a leafy bottom called a gametophyteand have a less dense protruding part

Gametophyte is dominant

Reproduce by releasing sperm that must swim through a film of water to fertilize an egg

The clades of Bryophytes

• Liverworts

• Mosses

• Hornworts

Rhizoid

Root like structures in plants that anchor them to the substrate

Lycophytes

Type of a seedless vascular plant that reproduces through water

ex. Club mosses and their relatives

Sporophyte is dominant

Monilophytes

Type of seedless vascular plant that reproduces through water

ex. Fern and their relatives

Xylem

Type of vascular tissue that transports water and minerals

COnsists of dead cells

Phloem

Transports organic products like sugars or amino acids

Tracheids

Tube shaped cells that make up some of the xylem that conduct water and minerals

Lignin

Recalcitrant compound that strengthens xylem and doesn’t get broken down easily

Addition of this to vascular tissue provided the structural support for plants so that they can grow taller and have better access to sunlight or dispersal of spores

Roots

Absorb water and nutrients from the soil and anchor vascular plants to the group

Leaves

Promary photosynthetic organ of vascular plants

Microphylls

Small leaves with a single strand of vascular tissue and are only found in lycophytes

Ex. Krauss’s spikemoss

Megaphylls

Large leaves with a highly branched vascular ststem and are found in most other vascular plants

Ex. Tunbridge filmy fern

Seed

An embryo and its food supply contained within a protective coat

Wind or other long distance seed dispersal methods allowed seed to travel long distances and expand into new habitats on land

Gymosperms

Plants that have naked seeds that aren’t enclosed within chambers

ex. Sago palm or Douglass Fir

Angiosperms

Plants that have seeds that develop inside chambers called ovaries

Also produce reproductive structures called flowers or fruits

Pollination

Transfer of a pollen grain into the part of a seed plant containing the ovules

Pollen is generally transported by the wind or by attaching to the body of animals

Sepals

Part of the plant that encloses the unopened flower bud

Petal

Attracts pollinators with bright colors

Stamen

Contains an anther that produces pollen atop a fillament

Carpel

Produces ovules

Contains 3 parts - stigma (sticky top that catches pollen), styles (stalk) and an ovary at the base (contains ovules)

Retrovirus

A RNA virus that reproduces by transcribing its RNA into DNA inside a host cell using the enzyme reverse transcriptase. The DNA is then integrated into the host genome as a provius and becomes a permanent part of the host’s DNA

ex. HIV

Viroid

Circular RNA molecules that infect plants.

Lack a protein coat

Replicate within host plant cells and cause disease by disrupting gene expression

Prions

Infectious proteins that cause neurodegenerative diseases in animals. It is a misfolded form of a normal protein that can cause other normal proteins to misfold the same way

Vaccine

Works by injecting a harmless form or component of a pathogen like an inactivated or attenuated virus that triggers a response in the immune system which creates the appropriate memory cells and antibodies without actually causing the disease

They don’t cure an existing infection but provide immunity or a reduce in disease severity

Prokaryotes

Single Celled organisms without a nucleus

2 Domains: Archaea and Bacteria

Archaea

A type of prokaryote that thrives in extreme environments

Bacteria

A type of prokaryote that generally lives in normal temperatures

Nucleiod

A non membrane-bound region where DNA is concentrated in prokaryotes

Flagella

A structure of movement shaped like a thin rod

Taxis

A response to a stimuli seen in prokaryotes

Chemotaxis

Movement in response to chemicals

Binary Fission

Form of reproduction in prokaryotes where one cell divides into two identical daughter cells

Genetic Recombination - Transformation

Uptake of free DNA from the environment. A bacterium can absorb short fragments of DNA and incorporate them into its genome, altering its genotype

Genetic Recombination - Transduction

Transfer of DNA from one bacterium to another via bacteriophages (viruses)

Genetic Recombination - Conjugation

Direct transfer of DNA between two bacterial cells that are temporarily joined. Usually involves a donor cell with an F-plasmid forming a sex pilus to connect to a recipient cell. HOw antibiotic resistant genes spread

Phototrophs

Capture energy from sunlight

ex. Cyanobacteria performing photosynthesis

Chemotrophs

Obtain energy from chemical compounds