FINAL EXAM REVIEW BIO PT. IV

Virus

acellular, non‑living infectious particles

Obligate intracellular parasites

must infect a host to replicate

Genome types of VIRUSES

DNA or RNA, single‑ or double‑stranded, linear or circular

Capsid

protein shell protecting viral genome

Envelope

lipid membrane acquired from host; contains viral glycoproteins.

Helical viruses shape

rod‑shaped (e.g., tobacco mosaic virus).

Icosahedral viruses shape

20‑sided capsid (e.g., adenovirus)

Complex viruses

bacteriophages with head + tail

What do viral spikes do?

host recognition & attachment.

Lytic Cycle in order:

• Attachment

• Penetration

• Biosynthesis

• Maturation

• Lysis — host cell bursts

In the Lysogenic Cycle, Prophage formation:

viral DNA integrates into host genome

In Lysogenic Cycle: Dormancy

virus replicates with host cell

In Lysogenic Cycle: Induction

stress triggers switch to lytic cycle.

Animal Virus Replication process

• Attachment via glycoproteins

• Entry by fusion or endocytosis

• Uncoating — capsid removed.

• Genome replication — depends on genome type.

• Assembly & release — budding (enveloped) or lysis (non‑enveloped).

RNA Viruses: RNA‑dependent RNA polymerase happens when

host cells do not have this enzyme

Positive‑sense RNA

acts like mRNA

Negative‑sense RNA

must be converted to +RNA first

Retroviruses

use reverse transcriptase to make DNA from RNA

Reverse transcriptase

error‑prone → high mutation rate

Integration into host genome

forms provirus

Latency

long asymptomatic period

CD4 T‑cell infection leads to

immune system collapse

What is Zoonotic transmission?

animal → human

Antigenic DRIFT

small mutations → seasonal flu

Antigenic SHIFT

major reassortment → pandemics

In Plant Viruses: Transmission via wounds or vectors come from where?

insects, mechanical damage

Prions

infectious misfolded proteins

• Cause neurodegenerative diseases — mad cow, CJD.

• No nucleic acids — replicate by inducing misfolding.

Viroids

small circular RNA molecules.

• Infect plants — disrupt growth.

Cytopathic effects

cell death, lysis, syncytia

Adaptive immunity

• antibodies, cytotoxic T cells.

LUCA

Last Universal Common Ancestor; root of all life

Meaning of Prokaryotes as first life

existed billions of years before plants/animals

What was Early Earth conditions?

hot, volcanic, high radiation → thermophiles likely first

Microbial mats

layered prokaryotic communities

Stromatolites

fossilized microbial mats; 1.5 BYA evidence

What organism lived in Anoxic atmosphere?

only anaerobes

What is the Phototroph evolution?

early phototrophs that created cyanobacteria

What is the Oxygenation event?

cyanobacteria increased atmospheric O₂

Extremophile

prokaryotes adapted to extreme conditions

TYPE OF EXTREMOPHILE: Acidophiles

pH ≤ 3

TYPE OF EXTREMOPHILE: Alkaliphiles

pH ≥ 9

TYPE OF EXTREMOPHILE: Thermophiles

60–80°C

TYPE OF EXTREMOPHILE: Hyperthermophiles

80–122°C

TYPE OF EXTREMOPHILE: Psychrophiles

−15 to 10°C

TYPE OF EXTREMOPHILE: Halophiles

high salt

TYPE OF EXTREMOPHILE: Osmophiles

high sugar

PROKARYOTIC: Cocci description

sphere like

PROKARYOTIC:Bacilli description

rod shaped

Structure of Prokaryote

• Cell wall

• Plasma membrane

• Ribosomes

• Circular DNA genome

Flagellum

rotary motor

Pilus

gene transfer, attachment, movement.

Archae has what kind of lipids?

branched lipids

Bacteria has what kind of lipids?

unbranched lipids

Archaea has what linkage?

ETHER

Bacteria has what linkage?

ESTER

What does archae LACK in a cell wall?

no peptidoglycan

What does bacteria HAVE in a cell wall?

peptidoglycan

Transformation in PROK.

uptake of naked DNA.

Transduction in PROK.

bacteriophage‑mediated DNA transfer

Conjugation in PROK.

pilus‑mediated DNA transfer

Macronutrients in PROK.

C, H, O, N, P, S

Micronutrients in PROK.

Fe, B, Cr, Mn

Phototrophs get energy from

sunlight

Chemotrophs get energy from

chemicals

Chemoorganotrophs get energy from

organic compounds

Chemolithotrophs get energy from

inorganic compounds

Aerobic respiration accepts whose electron?

O2 (OXYGEN)

Anaerobic respiration accepts whose electron?

inorganic molecules

What is the Carbon cycle?

decomposition, carbon fixation

What is the Nitrogen cycle?

nitrogen fixation, nitrification, denitrification.

Typhoid fever

Salmonella enterica serovar Typhi

Tuberculosis

Mycobacterium tuberculosis

Lyme disease

Borrelia spp., tick‑borne

Foodborne pathogens

E. coli O104:H4, Shiga toxin

Antibiotic Resistance

• Superbugs — resistant strains due to antibiotic overuse.

• MRSA — methicillin‑resistant Staphylococcus aureus.

Nitrogen fixation

converts N₂ → ammonia

Skin microbiome

protection from pathogens

Gut microbiome

digestion, immunity.

Fermentation

cheese, yogurt, bread, wine, beer

Bioremediation

using microbes to remove pollutants

Protist

eukaryotes that are not animals, plants, or fungi

What is the protist cell structure?

nucleus, organelles, cytoskeleton.

Primary endosymbiosis

heterotrophic eukaryote engulfed cyanobacterium → chloroplasts

Secondary endosymbiosis

eukaryote engulfed a photosynthetic eukaryote → complex plastids.

Which shapes of protists are most common?

Unicellular protists

Multinucleate single cells

slime molds, Caulerpa

Multiple nuclei examples

amoebae, seaweeds

Dinokaryon

unique nucleus in dinoflagellates.

Silica shells

diatoms, radiolarians.

Pellicle

flexible protein strips for protection + movement

Photoautotrophs example

green, red, brown, golden algae

Absorptive feeders is a type of Heterotroph that

parasitic forms (Plasmodium, Giardia).

Phagocytosis is a type of Heterotroph

engulfing food particles

Mixotrophy

• combine photosynthesis + heterotrophy (e.g., Euglena).

Cilia

Paramecium

Pseudopodia

Amoeba

Flagella

Euglena, choanoflagellates

Binary fission

common asexual reproduction

Segsual cycles

fusion of haploid nuclei + meiosis

Red algae

primary chloroplasts, agar source, multicellular