Viruses
(virion)- consists of nucleic acid core surrounded by a protein coat called a capsid. smaller than bacteria. Not living- classified separately, based on common characteristics:
Capsid make up
proteins called capsomeres- determines shape of virus.
bacteriophage
virus that affects bacteria;
cell makeup of viruses
acellular and cannot independently perform metabolic activities
virus reproduction
Can reproduce but only within other cells- takes over the cell’s genetic information
Virus nucleic acid
Nucleic acid=DNA or RNA but not both. DNA–single or double stranded.
virus classification
type of nucleic acid (DNA/RNA…see recording). presence/absence of capsid
virus origin
Virus came from bits of nucleic acids that “escaped” from cellular organisms (transposons or plasmids) in plants, animals, or bacteria
plant virus can only infect plant
Lytic cycle-
type of virus reproductive cycle. lyses or destroys host cell. Viruses that only have lytic cycles are virulent
Attachment or absorption
viruses attach to receptors on host cell wall or cell membrane
Penetration-
nucleic acid moves from virus into cytoplasm of host cell
Replication and synthesis
virus degrades host cell nucleic acid and uses host cell to synthesize necessary components for its replication
Assembly
newly synthesized viral components are assembled into new viruses
Release
new viruses are released from cell. Lytic enzymes produced by phage destroys host’s plasma membrane
Steps of lytic cycle
Attachment or absorption, penetration, Replication and synthesis, Assembly, Release
Temperate viruses
do not always destroy their hosts. They have lysogenic cycle in which the virus become integrated into the hosts
Temperate viruses details
This virus replicates when the host cell replicates. Certain external conditions can cause them to revert to a lytic cycle, or they may remain repressed indefinitely.
Viruses that infect animal cells
May have DNA–DNA from virus integrates into DNA of the host cell
May have RNA–in some, used as mRNA in the host cell
retroviruses
infect animal cells; Reverse transcriptase produces DNA from the RNA, which then becomes integrated into the host DNA, which is used to make RNA again (HIV is ex)
Viruses that infect plant cells
Because plants have thick cell walls, viruses cannot penetrate plant cells unless they are damaged. Once enters- spreads through plant via plasmodemata. Most RNA viruses
Symptoms: reduced plant size, spots or streaks on leaves, flowers or fruits
Viroid-
smaller than a virus, has no protective protein coat, Consists of short strand of RNA; Cause plant disease
Prion
“proteinaceous infectious particle”- animals have a gene that codes for this prion (208 amino acids)- normally harmless. But it can convert to a different shape and cause disease
tobacco mosaic virus
infects tobacco plants
Bovine spongiform encephalopathy-
“mad cow disease”- prion. cattle became infected when ate feed containing infected brains and organs from sheep
transmissible spongiform encephalopathies (TSEs)-
prion. group of fatal degenerative brain diseases- when animals are infected, brain appears to develop holes and become sponge- like
Prokaryotes
no nucleus or organelles except for ribosomes; have single chromosome and some have plasmids; Cells walls contain peptidoglycans; Some contain flagella or capsule around the cell wall for added protection against phagocytosis; many have pilli
peptidoglycans
polysaccharides with polypeptides
pilli
hair-like appendages that help in adherence
flagella prokaryotes
consists of flagellin (single filament), not tubulin in 9 + 2 like in eukaryotes
How do prokaryotes reproduce?
Binary fission, budding
Binary fission-
one cell divides into two equal sized cells
Budding
cell develops small bud that matures and separates from the mother
Genetic variation in prokaryotes can be introduced by
Conjugation, Transduction, Transformation
Transformation-
bacteria absorbs DNA from its surroundings
Transduction-
new DNA is introduced into bacteria through a virus
Conjugation-
DNA exchange between two bacteria cells. Donor bacteria produced tube, or pilus that connects to the recipient cell Donor’s chromosomes can be sent, allowing recombination w the recipient
How are prokaryotes organized?
organized by mode of nutrition (chemo/photoautotroph/Heterotrophs–parasites/saprophytes) or by O2 presence
saprophytes
decomposers
Obligate aerobes
need O2
Obligate anaerobes
cannot be in presence of O2
Facultative anaerobe
grow in oxygen but can switch to anaerobic conditions
Archeabacteria
Cell walls lack peptidoglycans; similar ribosomes to eukaryotes; Different lipids in plasma membranes as compared to eubacteria; 3 groups
3 groups Archeabacteria
Methanogens produce methane gas
o Extreme halophiles live in high salt conc
o Thermoacidophile hot and acidic environments
Eubacteria
Mostly decomposers; Reside in human body (700 trillion) and can be beneficial;
protists
This kingdom is unique in that the organisms that are grouped here are
extremely diverse- grouping them together in the Protist kingdom is
done for sake of convenience. Ex- organisms may be algaelike, animallike, funguslike,
unicellular, or multicellular
FUNGI
Eukaryotic, heterotrophic, cell walls with chitin, filamentous inside, Mold or yeasts, Reproduction by spores,
PLANTS
Eukaryotic, Autotrophs
- Cell walls with cellulose
- Terrestrial
- Have alternation of generation
- All have protected embryos
alternation of generation
o Spend part of lives in multicellular haploid stage and part in
multicellular diploid stage
ANIMALS
Multicellular eukaryotes - Heterotrophic Diploid generation is dominant - Most are motile at some point in life Most undergo a period of embryonic development during which 2 – 3 layers of tissue form
Eumetazoa
animals cells organized into tissues
Parazoa
animals no organs/tissues
Diploblastic
eumetazoa embryo w 2 cell layers
Triploblastic
eumetazoa embryo w 3 cell layers
Ectoderm
outer layer Triploblastic outer covering of the body and nervous tissue
Mesoderm
Triploblastic middle layer- gives rise to muscles, skeleton, circulatory system
Endoderm-
Triploblastic inner layer- gives rise to digestive tube
Body symmetry
Radial symmetry- circular body pattern (body has form of
wheel), only have front and back/ top and bottom
o Bilateral symmetry- can be divided through one plane to
produce right and left halves of the body
Cephalization-
In animals with bilateral symmetry, the anterior end
has increasing tissue (ex- formation of brain) as organism increases in complexity
Gastrovascular cavity-
“gut” area where food is digested, One-two openings
Coelom
fluid filled space between body wall and digestive tissue that cushions internal organs
Acoelomate
animals lack a coelom
Pseudocoelemate
animals that have a cavity that is not completely lined by mesoderm tissue
Coelomate
animals with a true coelom lined completely by
mesoderm, producing a tube within a tube body plan
Segmentation
Many have body parts that are the same but repeat or modified to perform special functions
Protostomes/Deuterostomes
Animals with coelom are divided into two groups:
Protostomes- include mollusks, annelids, arthropods
Deuterostomes- include echinoderms and chordates
Differ in pattern of cleavage- cell divisions that take place in the early development of the zygote and differentiation of archenteron first infolding from the blastula (ball of stem cells)
