Bio 2 Exam 2

Structure of Virus

Nucleic acid surrounded by a protein coat(capsid)

Capsid

The protein coat that surrounds viruses

What do viruses lack that distinguishes them from living things

No cellular organelles

No metabolism

Cant grow

Cant reproduce via mitosis/meiosis

Unknown ancestry, no record,inconsistent nucleic acid, no taxonomy

Infect all living things, host specific

What kind of structure is a virus

Infectious structure, can infect bacteria, fungus, plants, and animals

Obligate parasites?

Viruses

Cannot metabolize or reproduce outside a host

Virus firsts

Discovered in 1886; TMD

Too small tosee with light, visualized in 1930s w an electron microscope

Viral size

20-250nm

Virus shapes

Come in several shapes and sizes consistent across viral familes

Virus components

Viral nucleic genome

Protective capsid

Glycoprotein on capsid

Plasma membrane

Capsomeres

Capsid proteins coded for in viral nucleic acid

Plasma membrane

Envelope made of host’s plasma membrane

Viral Classification

Morphology

Type of nucleic acids

4 Viral capsids

Helical

Icosahedral

Enveloped

Head-and-tail

helical viruses

Tubular protein capsid

Nucleic acid

Most plant viruses

Icosahedral Viruses

Spherical protein capsid

Nucleic acid

Most common viral family: Adenovirus & Poliovirus

Enveloped Virus

Envelope from host cell membrane, surrounds a icosahedral capsid

Rapidly adapt to host

Nucleic acid

Head and Tail

icosahedral head

Helical tail

Bacteriophages, infect bacteria

Nucleic acid types

DNA or RNA viruses

Characteristics of viral genomes

Small genome for making: DNA/RNA, Proteins for capsid, Replication proteins unavailable in host cell

Viral Nucleic Acid Characteristics

DNA/RNA can be ds or ss, linear or circular

Transcription

DNA used as template to make mRNA

Translation

mRNA used as template to build protein

Template mRNA

+mRNA

Uses - DNA strand as template

DNA Viruses

Nucleic acid is DNA

viral DNA directs host DNA Pol to replicate viral DNA rather than host DNA

Transcription and translation of viral DNA into viral proteins

Human DNA virus:

Chicken pox

Herpes

HPV

RNA viruses

Viral nucleic acid is RNA

viral RNA encodes for replication enzyme (RNA Pol) that replicate viral RNA into +mRNA ot be used for translation

Retroviruses

RNA encodes for enzymes that replicate the viral DNA into DNA

Retrovirus steps to make mRNA

Reverse transcription into ssDNA, then makes it’s own cDNA, yielding dsDNA, insrted into host DNA

Then transcribed into mRNA

Human RNA viruses

HIV

measles

SARS-COV2

RNA Pol is not fastidious

Makes many mistakes

RNA viruses mutate more frequently than DNA viruses

RNA viruses are able to readily adapt to hosts

Viral glycoproteins

Glycoproteins can be found on the surface of the capsid that are recognized by host cell receptors

Viruses evolved to utilize receptors

Viral host range

Viruses have a narrowed range of organisms/tissue they can infect using their glycoproteins for cell recognition

Cell receptors that viruses recognize

Cell-cell recognition

Enzymatic activity

cell-cell anchors

Viral life cycle

Attachment: Attaches to host cell at receptor

Penetration: Capsid penetrates host cell

Uncoating: Viral contents are released into host cell

Replication: Nucleic acid enters host nucleus, replicated/transcribed into +mRNA w viral Pol or host cell Pol

Assembly: +mRNA is used to create viral enzymes, capsid proteins, and viral nucleic acid

Release: Newly created viruses are released from the host cell

Lytic Lifecycle

Host cell is destroyed in lytic life cycle

Release of viruses destroys the host cell

Lysogenic life cycle

Host cell not destroyed

Viral DNA integrated as a prophage in bacterial host

Not same as viral latency

Bacteriophage life cycles in kingdoms

Lysogenic and lytic bacteriophages infect bacteria in the Kingdom Bacteria

• Archaea have similar viruses

Viral Latency

A part of lytic life cycle and some Eukaryotic viruses

After initial infection, virus settles in nerve tissue and goes long periods of time without producing new viruses

• Herpes

Happens when no longer producing more viruses

Can either integrate or become episomes

Viral Specificity

Can sometimes only infect a single species

Small pox humans

Plant viruses plants

Some times broad: rabies

Horizontal Transmission

One organism to another (all viruses

Vertical Transmission

Parent to off spring; primarily in plants

In ppl: HHV-6 and HHV-7

Plant Transmission

cannot occur unless cell wall is initially damaged; occurs as a result of mechanical damages

Animal transmission

No cell wall; more easily infected

Receptor Mediated Endocytosis

Animal cell imports virus after cell receptor-virus interacction

Transport Protein Mimicry

Viral capsid protein can become a transport protein

Viral DNA passes through

Vaccine

Show immune system what virus looks like to build immunity to certain viruses and bacteria

most viral

Prevent serious infection, not contagiousness; viral load still present

Antibiotics do NOT work

Antibiotics treat infections

Types of vaccines

Live, attenuated

Killed

Subunit

Live attenuated

Active but weakened virus

Killed

Entire virus dead

Subunit

Use portions of viral proteins or nucleic acid

mRNA vaccine

Flu virus physical characteristics

Enveloped virus

-ssRNA

Spherical capsid

Type A flu virus

infects humans, birds, pigs

illness and death

75% of seasonal flus

Divided into subtypes based on 2 proteins

Hemagglutinin and neuraminidase

18H and 11 N

Swine flu

Swine Influenza Virus hemagglutinin 1 and Neuraminidase 1

Type A

Type B

Infects humans and seals; causing illness and death

Victoria and Yamagata

Based on hemagglutinin

Type C

Infect humans dogs and pigs

mild; no death

Type D

Cows and pigs not people

Corona virus characteristics

Enveloped virus w protein spikes

+ssRNA w in enveloped capsid

5 Groups of CoV

Alpha, Beta, gamma, delta, omicron

4 Human CoV

229E (alpha)

NL63 (Alpha)

OC43 (beta)

HKU1 (Beta)

Three Novel CoV

Middle Eastern Respiratory Corona Virus 2012

Severe Acute Respiratory Beta coronoa virus, SARS 2003

SARS CoV2, Beta in 2019

Prokaryotes

Appeared 3.5 Billion years ago

1 billion after earth

Predate eukarya by billions

Everywhere; extremophiles

Pioneers

Recycle nutrients

10 Prokarya:1 our cells in body

Beneficial to life

Can be harmful

Ancient Life

No oxygen; intense solar radiation

Lived in colonial microbial mats near hydrothermal vents and volcanos

Chemoautotrophic

Spewed to surface

Photosynthesis 1.5 billi years after prokaryotes

Cyanobacteria/blue green algae from first terrestrial prokaryotes

Photosynthesis oxygenated the atmosphere

Allowed other life to colonize earth

Created the ozone layer

Protection from solar radiation

Prokaryotic structure

No membrane-bound organelles

Cell Wall

Plasma membrane

Ribosomes

Some flagella/cilia for locomotion

Pilli attach to surface of other cells

Circular dsDNA

Plasmids

Plasmids

Small circular DNA molecules

Can be acquired from other bacterial cells or from the environment

Plasmids replicate independent of bacteria’s own chromosome

Contain only a few genes not present in bacterias own chromosome

Prokaryotic shapes

Coccus

Bacilli

Spirillus

Peptidoglycan

Comprise the bacterial cell wall

Polysaccharide chain cross linked by both L- and D- Amino acids

Most amino acids are only L-form, some D

Gram positive

All gram positive in same phylum

Thick cell wwall

90% Peptidoglycan/10% teichoic acid

Gram negative

All other phyla are gram negative

10% peptidoglycan

Outside of cell wall is a capsule layer of lipopolysaccharide and lipoproteins

Second lipid bilayer

Prokaryotic cells reproduce via?

Binary fission

Binary fission

Circular chromosome replicated by DNA synthesis

Bacteria grows

Pinches inward until it seperates into two seperate cells

Clones

No mitosis

No gene recombination

Mutations provide variance

Bacteria can share genes with other bacteria

• Transformation

• Transduction

• Conjugation

Transformation

Bacteria absorb plasmid/bacterial DNA shed by another

Absorbed plasmids remain plasmids

DNA must be incorporated into recipient bacterial chromosome to be transcribed

Transduction

Bacteriophage transplant bacterial DNA from one bacteria to another

bacterial DNA from last bacteriophage host is interspersed into viral DNA and incorporated into the new bacterial host

Conjugation

DNA transferred from one bacteria to another via pilus

Can transfer plasmid or parts of bacterial genome

F+ factor gene produces sex pilus

Hfr cell has F⁺ gene

Epidemic

Disease affecting high percent of population in a specific area

Yellow fever, cholera

Pandemic

Widespread, world wide, epidemic with a high death toll

HIV/AIDS, Spanish flu, Cholera, bubonic plague, Covid

Endemic

Disease always present in a population

Chicken pox, the flu

Infections are often treated

Inappropriately

Antibiotic resistance

Antibiotics target cell walls/cytoskeleton, preventing reproduction

Some bacteria will naturally be partially resistant to antibiotics, can eventually select for fully resistant bacteria

Transformation,transduction, and conjugation allow bacteria to obtain resitance

Overuse causes resistance

Staph aureus

Common bacteria, infects animals, treated with antibiotics

Methicillin resistant staph aureus, resistant to most antibiotics

Easily treated bacteria are becoming resistant

Development of new is time consuming and expensive

Eukaryote distinct characteristics

Nucleus w nuclear membrane

Chromosomes of DNA organized around histone protein

Membrane-bound organelles

Mitochondria(and chloroplasts if photosynthetic)

Cytoskeleton of microtubules and microfilaments

Mitotic

Can be sexually reproducing, some asexual

Endosymbiont theory

Mitochondria and chloroplasts came from engulfment of a once free living bacteria

Formed chimera cell

Coevolved for millions of years, no inseparable; true mutualistic symbiotic relationship

Support for Endosymbiosis from structure

Two membranes

Have circular DNA

Have ribosomes and translate their own protein

Divide to create new mitochondria/chloroplasts

• host cell does not build new mitochondria/chloroplasts

• Divide independently

Fungi characteristics

Eukaryotes, nucleus and membrane bound organelles

More closely related to animals than plants

Chtin cell wall

No photosynthetic pigments

No chloroplasts

Heterotrophs, absorb carbon, dont fix carbon dioxide

Most have both sexual/asexual reproduction

Can be mutualistic/parasitic

People use fungus in food/beer/wine production

Fungi structure

Nucleus, DNA wrapped around histones

Body tissue is haploid

membrane bound organelles

mitochondria

No chloroplasts

Cellular pigments, not used for photosynthesis, protect against UV, many are toxic

Cell wall

Plasma membrane contains ergosterol NOT cholesterol

non motile

Fungi vs Yeast

Fungi: Multicellular

Yeast: unicellular

Fungi Morphological states

Vegetative and Reproductive

Vegetative body

Also called the thallus, produces hyphae

Hyphae

a haploid filamentous structure

Collective hyphae=mycelium

Vegetative hyphae are haploid

Septated Hyphae

When each nucleus is divided by a cell wall

Coenocytic hyphae

Hyphae undivided by cell walls

Fungal Light/O₂ req

Moist environments

Slightly acidic

Grow with or without light

Not photosynthetic

Obligate aerobes

Obligate anaerobes

Facultative Anaerobes, can facilitate anaerobic conditions

Fungal Nutrition

Heterotrophs

consume organic/inorganic compounds

Most saprophytic

• consume decaying in/organic matter

• break down lignin and cellulose

• Good recyclers

Fix nitrogen, some hunt worms/insects in nitrogen poor soil

Digest food with exoenzymes from hyphae which is then imported into mycelium

Store carbs as glycogen

Parasitic potentially

How do perfect fungi reproduce

Asexually or sexually

How do imperfect fungi reproduce

Asexually

Modes of fungal asexual reproduction

Fragmentation, fragments grow into new separate mycelium

Budding, cytoplasm bulges, nucleus divides via mitosis, bud separates from mother

Spores: haploid spores through mitosis that can develop into haploid vegetative hyphae

Steps Sexual Fungal Reproduction

Plasmogamy: two unrelated haploid hyphae fuse (seperate nuclei); reproductive body is heterokaryotic (n+n)

Karyogamy: nuclei fuse and form a diploid zygote

Meiosis: zygote splits into haploid 1n spores

Germination: Mycelium forms

Then:

Fragmentation: Mycelium fragments to produce more hyphae

Produce haploid spores via mitosis

Perfect do both

Saprophytes

Release nitrogen and phosphorous from decaying organic matter

Fungi produce exoenzymes

released to substrate or bound to cellw all

Large molecules hydrolyzed, transported into cells

Hydrolysis requires water

Mycorrhizae

When fungal hyphae interacts with vascular roots, channel water and dissolved nutrients to plant roots

• Plants provide fungus w G3P or glucose that fungus uses to create ATP

Ectomycorrhizae

Hyphae sheaths the roots

Endomycorrhizae

Hyphae grow inside of roots in arbuscule

Endophytes

Fungus lives inside the plant tissue

Doesnt damage plants

Fungus release toxins to repel herbivores

Fungus release chemical to help plant respond to stress