lecture ch 19/20 Flashcards
Astrobiology is ____
Astrobiology: Study of life’s origin and distribution in the universe
Around 4.6 billion years ago, Earth and
other planets formed
t or f
True
Evidence of early water
Evidence of early water
When Earth’s crust cooled, water condensed on its surface
Zircon crystals 4.4 billion years old provide the earliest evidence
Evidence of early atmosphere
Evidence of early atmosphere
Volcano eruptions led to an atmosphere of water vapor, carbon dioxide,
nitrogen, and hydrogen (toxic and unbearable for us!)
Iron in the oldest rocks is not oxidized (rust); so the early atmosphere was oxygen free
Any oxygen would have oxidized organic molecules as soon as they formed
Formation of organic monomers:
a. Hypothesis 1:
b. Hypothesis 2:
c. Hypothesis 3
1=== LIGHTNING FUELED ATOMSOPHEREIC- REACTIONS tested by Miller and Urey in 1953
Filled a reaction chamber with methane, ammonia, hydrogen gas; zapped with sparks from an electrode
Within a week, a variety of organic molecules formed, including amino acids
2=== DELIVERY FROM SPACE
Many meteorites that fell on the early Earth
carried organic monomers that had formed in
space
3=== REACTIONS AT HYDROTHERMAL VENTS
Underwater geysers where mineral-rich water (mainly Hydrogen
Sulfide) is heated by geothermal energy
A combo of heat and carbon dioxide, and potassium cyanide may have
formed amino acids
Eukaryotes have mitochondria. What does the endosymbiont hypothesis say about the origins of mitochondria?
a-A eukaryote capable of cellular respiration was engulfed by an early prokaryote and became an endosymbiont.
b- A prokaryote capable of cellular respiration was engulfed by an early eukaryote and became an endosymbiont.
c- An organelle capable of cellular respiration evolved within the cell from organelles capable of photosynthesis.
d- A prokaryote capable of photosynthesis was engulfed by an early eukaryote and became an endosymbiont.
b- A prokaryote capable of cellular respiration was engulfed by an early eukaryote and became an endosymbiont.
The endosymbiont hypothesis states….
The endosymbiont hypothesis states that early eukaryotic cells engulfed prokaryotes capable of __cellular respiration__ .
which explains why all modern eukaryotes have mitochondria, and later some eukaryotes engulfed prokaryotes capable of ___photosynthesis___ ,
which explains why a limited number of eukaryotes have chloroplasts.
binary fission steps
---ADNP--- ATTACHES DUPLICATES NEW MEMBRANE AND CELL WALL PARTIONING OF CELL=2 IDENTICAL DESCENDENTS
1–The chromosome attaches to the inside of the plasma membrane.
2–The cell duplicates its chromosome and starts to extend its cell membrane and cell wall.
3–When the cell has almost doubled in size, new membrane and cell wall are deposited across the midsection.
4–The partitioning of the cell results in two identical descendant cells.
Which of the following is an organism that obtains energy from light and uses organic compounds as a carbon source?
Photoheterotroph
When microscopist ______ discovered bacteria, scientists realized that microbes can cause disease and called them PATHOGENS
van Leeuwenhoek named them PATHOGENS
_______ are non-cellular infectious particles that
consist of nucleic acid surrounded by a coat of
capsid proteins and, in some cases, an envelope
derived from membrane of its host
Viruses are….non-cellular infectious particles that
consist of nucleic acid surrounded by a coat of
capsid proteins and, in some cases, an envelope
derived from membrane of its host
-Viruses discovered in late 1800s
specialized viruses that infect bacteria
Bacteriophages
Bacteria and archaea have separate domain classifications
but they….
SHARE MANY structural and functional SIMILARITIES
total 6
Bacteria and Archaea SIMILARITIES:
1. No nuclear envelope; chromosome in nucleoid
- single chromosome (a circular DNA molecule); many species also contain plasmids
(plasmid=a small circle of DNA separate from the chromosome) - Cell wall (in most species)
- Ribosomes distributed in the cytoplasm
- Asexual reproduction by binary fission
- Capacity for gene exchange among cells by way of conjugation, transduction, and transformation-horizontal gene transfers
accessory ring of DNA
used to create gmo
plasmid
about bacteria and archae…
Cannot be seen without a light microscope
Three cell shapes are common: bacillus, coccus, and spirillum
Most have a semirigid, porous cell wall around their membrane
Bacteria may also have a slime layer or capsule around their cell wall
Single circular chromosome of double-stranded DNA in a cytoplasmic region called
the nucleoid
Single circular chromosome of double-stranded DNA in a cytoplasmic region called
the nucleoid
hairlike filaments on surface of a cell are called ____ and used for …..
hairlike filaments on surface of a cell are called ___pili____ and used for …..
Sticking to surfaces
As grappling hooks to help a cell glide along
In gene exchange with other bacteria
Many Bacteria and Archaea have a _______
—- Rotates like a propeller; does not contain microtubules, does not bend side to side
flagellum
Horizontal gene transfers… (sexual reproduction)
Transformation:
Transduction:
Conjugation:
Transformation: absorbing from the environment
(A cell takes up DNA from its environment and integrates it into its genome)
Transduction: Bacteriophages move genes between cells
(bacteriophage= virus that can infect bacterial cells)
Conjugation: Movement of genes in a plasmid,
-happens with sex pillus -straw like structure
(plasmid- accessory ring of DNA)
Viral Replication
——Most viral replication processes involve the same steps when there is a
CHANCE encounter with a host cell
WHAT ARE THE STEPS
A PENIS RECENTLY SAW A RING GIRL
ATTACHMENT
-The virus recognizes and becomes attached to a host cell
PENETRATION
-dna or rna , alone or whole virus, enters cytoplasm
REPLICATION AND SYTHESIS
-Viral genes direct the host cell into replicating viral nucleic acids, synthesizing viral enzymes and capsid proteins
ASSEMBLY
-Synthesized components are put together into new infections particles
RELEASE
-New virus particles are released from the infected cell
VIRAL REPLICATION-
Two pathways for bacteriophage replication…..
LYTIC PATHWAY
Viral genes expressed immediately after quickly accomplishing steps 1-4
(previous slide) then causes the cell to rupture (lysis), spilling contents and
virus via step 5.
LYSOGENIC PATHWAY
Viral genes undergo steps attachment and penetration, but then remain
dormant inside the host cell.
Viral genes become integrated into host DNA and replicates
Resume destructive activity later (steps 3-5 in previous slide)
______ is a retrovirus, which is a virus bearing an RNA genome that is
used as template to produce double-stranded DNA.
HIV
To infect, HIV attaches to white blood cells
Viral enzymes and RNA are released into the cell and reverse transcription
makes the DNA copy of the viral genome
DNA enters the nucleus and inserts the viral DNA into the host’s DNA. The
viral DNA is replicated and transcribed along with the host genome.
Viral RNA and proteins are synthesized, and HIV particles assemble at the
plasma membrane, budding out of the host cell and incorporating its
plasma membrane as the envelope
HIV HPV stands for
(Human Immunodeficiency Virus),
human papilloma virus
_________historically defined as cells without a nucleus
IT Consists of both Bacteria (modern bacteria) and Archaea (ancient bacteria, more recently discovered; many live in extreme habitats)
PROKARYOTES
_____ build their own food using CO2 as a carbon source
_____obtain energy from light
_____ obtain energy from chemicals
Autotrophs build their own food using CO2 as a carbon source
Photoautotrophs obtain energy from light
Chemoautotrophs obtain energy from chemicals
______________ obtain carbon by taking up organic molecules from their environment, Not capable of making their own carbon (food)
_______________ harvest energy from light and carbon from organic compounds
________________:
- —-Not capable of making their own carbon (food)
- —-Obtain energy and carbon by breaking down organic compounds
- —-All pathogenic bacteria are of this type
- —-Beneficial bacteria in the digestive tract
- —–Some are decomposers
HETEROTROPHS obtain carbon by taking up organic molecules from their environment
Not capable of making their own carbon (food)
PHOTOHETEROTROPHS- harvest energy from light and carbon from organic compounds
CHEMOHETEROTROPHS
Not capable of making their own carbon (food)
Obtain energy and carbon by breaking down organic compounds
All pathogenic bacteria are of this type
Beneficial bacteria in the digestive tract
Some are decomposers
Many bacteria and most archaea are anaerobic T OR F
TRUE
______incorporating nitrogen from the air (N2)—-»>ammonia (NH3)
Photosynthetic eukaryotes need and use ammonium
Without this, all life on Earth would not be possible
Nitrogen fixation:
