Lecture 14: Cell Diversity And Viruses Flashcards
The genome is a dynamic…
Information system which impacts how cells respond and what actions they take
Cells contain a large number of…
Components
Cells are organized with respect to…
Time and space
Eukaryotic cells are structurally more _____ than prokaryotic cells
Complex
Protista are…
Enormously diverse
Protista basic features (6)
- Mostly unicellular
- Mostly aquatic
- Often contain flagella or cilia - ability to be motile
- Sexual and asexual reproduction
- Diverse nutrition lifestyles
- Link between prokaryotes and eukaryotes
Protista nutrition lifestyles include… (5)
Photosynthetic
Holotrophic - ingest other organisms and digest that (e.g. amoeba)
Saprotrophic - ingest dead material
Parasitic
Symbiotic - Protista and microalgae work together to form lycans
Examples of Protista… (4)
- Protozoans
- Unicellular red and green algae
- Diatoms
- Slime molds
Protista are found where on the phylogenetic tree?
Between the fungi and the prokaryotes
Slime molds were previously identified to be a part of the ______ kingdom, but are now grouped into the kingdom _____ - it is not a _______
Fungal
Protista
Mold
Slime mold basic features
- Eukaryotic
- Single celled
- Use spores as form of sexual reproduction
- Size: less than 1 dm to several square metres
- Multinucleate (1 cell has 1000s of nuclei)
- Have capacity to move around and respond to their environment
What is the sole purpose of viruses?
To make more of themselves
The virosphere is…
All of the viruses present on planet earth
There are probably millions of distinct viruses because…
Each microbe is associated with at least one virus
How many viruses have we characterized so far?
About 5000
Viruses are not ______
cells
Viruses reproduce only…
Within living cells
Outside of a cell, a virus is a…
Virion - when a virus exists as an inanimate particle outside of a cell
Basic properties of viruses
- Highly complex and organized
- Activity controlled by a genetic program - however coding capacity can be low
- Can reproduce - make copies of themselves
- Can evolve - very rapidly - variants
Structure of viruses
- All have a nucleic acid
- Protein coat (capsid - composed of capsid proteins) that surrounds nucleic acid
- Enclosed in a protein-containing membrane (enveloped - many) or not (naked or in enveloped)
- Nucleic acid either RNA or DNA; encodes viral proteins - thus either RNA or DNA viruses
HIV features
- Retrovirus
- RNA - can be converted to DNA
- Insert copy of its genome into the hosts DNA
- Permanent - AIDS
Hep-B features
- Hepadnavirus
- DNA virus
- Affects human liver and causes infection
Ebola virus features
- Filovirus
- Encode their genome in the form of single-stranded negative-sense RNA
- Kills cells quickly
Bacteriophage is a virus that
Infect prokaryotes - within bacteria and archaea
Adenovirus features
- Large group
- Respiratory illness
Tobacco Mosaic virus is…
One of the smallest viruses we know of, about 300 nm in size
Bacteriophages bind to bacteria through…
Tail fibers
Inside capsid head of bacteriophage, it contains…
Nucleic acid, which is mostly DNA
Sheath of a bacteriophage…
Injects DNA into bacteria
DNA of bacteriophage…
insert into bacteria genome and starts to replicate itself to be released from bacteria
CRISPR-Cas is…
A way to battle continuous attacks from bacteriophages, CRISPR-Cas is an evolved-like immune system.
Types of host ranges that viruses can have are… (2)
- Narrow host range - cold
- Wide host range - rabies
Once inside a cell, the virus…
Hijacks cellular machinery to synthesize nucleic acids (DNA/RNA) and proteins, which are assembled to make new viruses (viruses replicate within the host)
What are the two main types of viral life cycles?
- Lytic
- Non-lytic (lysogenic)
Non-lytic (lysogenic) viral life cycle is…
- Viral nucleic acid is replicated in the host; viral proteins produced
- Virus reproduces without destroying the host cell
Lytic viral life cycle is…
- Production of virus particles ruptures (and kills) host cell (e.g. bacteriophages; Ebola virus)
Combination of both ____ and ____ life cycles are found in nature
Lysogenic and Lytic - e.g. cold sores
Lysogenic life cycle:
- Once enveloped virus proteins recognizes proteins on the surface of host, goes through endocytosis, and virus is internalized
- Virus ejects capsid, and separates nucleic acid from capsid
- Separated nucleic acid creates envelope that goes to plasma membrane and also created capsid proteins that form around a new nucleic acid
- exocytosis takes place and new virus is created
Rabies has an…
Enveloped single-stranded RNA genome
How do RNA vaccines work?
Trick the body’s cells into producing fragment of virus
Glycoproteins are…
A gene that is on the outside of the cell
COVID-19 Spike protein
Binds to cells, and have evolved through many spike variants
What is a provirus?
Virus that can integrate into host genome
HPV virus is a…
DNA virus
What is a strategy to make RNA vaccines more effective?
Replicate, makes lots of copies of the RNA template for producing antigens
What is the main factor that determines what cell type a virus can infect?
Surface expression of a specific protein
