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Flashcards in Origins of Life Deck (37)
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1
Q

Earliest actual cells

A

prokaryotic heterotrophic anaerobes

2
Q

prokaryotic heterotrophic anaerobes

A

obtained energy by consuming organic material contained in the organic soup; performed fermentation bc there was no free O2

3
Q

What happened to the first cells once the supply of organic food depleted?

A

natural selection occured; Autotrophic cells were selected for (formed by mutation) since they no longer depended on organic food

4
Q

How did the first autotrophic cells function?

A

Used energy from the sun and inorganic materials (H 2 S) as hydrogen/electron source to produce organic materials, releasing
sulfur

5
Q

What evolved after the autotrophs?

A

Cyanobacteria

6
Q

Cyanobacteria

A

first to use water as a source for hydrogen and electrons

7
Q

What process did cyanobacteria perform?

A

photosynthesis

8
Q

what did cyanobacteria release as a waste product?

A

O2

9
Q

What evolved after O2 became a thing? Why?

A

Aerobes evolved- used oxygen to extract more energy from food–>more efficient than anaerobes

10
Q

What happened when aerobes evolved?

A

Carbon started cycling throughout the biosphere, from the physical environment (CO 2 ) to autotrophs to heterotrophic aerobes and back out

11
Q

What would happen when sunlight would break the double bonds of oxygen?

A

O3 was formed

12
Q

O3

A

ozone. protected surface of earth and allowed organisms to move to land

13
Q

What happened once ozone formed?

A

Eukaryotes formed from prokaryotes

14
Q

Endosymbiotic theory

A

eukaryotic cells formed a symbiotic relationship between prokaryotic cells, in which the prokaryotic cells were ingested by other prokaryotic cells
eventually they became permanent part of their hosts (chloroplasts + mitochondria)

15
Q

Chloroplasts

A

evolved from photosynthetic bacteria living inside heterotrophic cells

16
Q

Mitochondria

A

evolved from aerobic bacteria living inside anaerobic cells

17
Q

evidence of endosymbiotic theory

A

Mitochondria and chloroplasts possess their own DNA in circular form; have their own ribosomes that resemble prokaryotic ribosomes; can reproduce independently; thylakoid membranes resemble photosynthetic membrane of cyanobacteria

18
Q

Chemical Evolution

A

scientists believed that life developed from nonliving matter

19
Q

Step by step chemical evolution

A

spontaneously formed small organic molecules –> Large organic macromolecules (proteins, nucleic acids) –>Complicated structures that could replicate–>cell-like structures–>first structures

20
Q

Early earth atmosphere

A

atmosphere def had CO2, water vapor, carbon monoxide, hydrogen, and nitrogen. might’ve had ammonia (NH 3 ), hydrogen sulfide (H 2 S), and methane (CH 4 ), but that would’ve been quickly broken down by UV rays. all these condensed into seas as the earth cooled

21
Q

requirements early earth

A

Little or no free oxygen; High energy (thunderstorms, volcanoes, strong UV rays) Chemical building blocks (water, gases) and time (4.6 billion years old; life appeared 3.8 billion years ago)

22
Q

why couldn’t early earth have free O2?

A

O2 is very reactive – would’ve interfered with formation of organic molecules

23
Q

Formation of organic molecules hypotheses

A

Prebiotic soup hypothesis or Iron-sulfur world hypothesis-

24
Q

Iron-sulfur world hypothesis-

A

organic precursors formed at hydrothermal vents

25
Q

Prebiotic soup hypothesis-

A

organic molecules formed near Earth’s surface

26
Q

A.I. Oparin

A

Prebiotic soup hypothesis. over time, the organic molecules accumulated in shallow seas to form a “sea of organic soup”. There, monomers would join to form polymers

27
Q

Stanley Miller-

A

designed a closed apparatus that simulated conditions existing in early Earth and exposed it to electrical charges (simulated lightning). Found that after a week, organic molecules were formed

28
Q

suggestion first cells

A

Polymers that have formed may have spontaneously created proteins

29
Q

proof of polymers–>proteins

A

protenoids

30
Q

protenoids

A

abiotically produced polypeptides

31
Q

Protobionts

A

groups of abiotic organic polymers. formed after the polymers spontaneously created proteins. Can resemble living cells–grow, maintain homeostasis, carry out reactions.

32
Q

Microspheres

A

are a type of protobiont formed by adding water to abiotically formed polypeptides. Their cell membranes contain an electrochemical gradient and are
selectively permeable

33
Q

RNA world

A

model that suggests self replicating RNA formed first, that functions as an enzyme and substrate for
its own replication

34
Q

Ribozymes

A

RNA molecules that can catalyze their own reactions w/o using enzymes

35
Q

How did RNA function without DNA?

A

RNA molecules can weakly bind to amino acids causing protein synthesis (on its own)

36
Q

How could DNA have come about?

A

Perhaps double stranded copies of itself, forming DNA, which is more stable than
RNA. Once DNA was formed, it had the selective advantage and became the
information storage molecule

37
Q

hydrothermal vents

A

deep cracks in the ocean’s floor which consist of hot water, carbon monoxide, and minerals