1.5 origin of cells

Question 1

spontaneous generation

Answer 1

the prevailing theory before Pasteur’s experiment. Living organisms can arise spontaneously from nonliving matter.

Question 2

biogenesis

Answer 2

Describes the principle that living things only arise from other living things by reproduction

Question 3

describe Pasteur’s experiment

Answer 3

1. Broth boiled in order to sterilize it (killing pre-existing micro organisms)
2. He allowed the broths to cool and sit for several days. In the Experimental group, as the broth cools, condensation seals the entrance of the tubing, resulting no organisms being able to enter into the flask.
3. If the neck is broken, bacteria would of been able to re-enter into the flask. Pasteur only found living organisms in the Control group with the broken neck. Broth became cloudy indicating bacterial growth
4. Demonstrated that cells are not generated spontaneously. Cells enter the broth from the surrounding air. Spontaneous generation theory was rejected, only living cells can produce new cells.

Question 4

abiogenesis

Answer 4

The theory that living cells arose from non-living matter.

Question 5

describe the Urey-Miller experiment

Answer 5

1. recreated the supposed conditions of prebiotic Earth (methane, ammonia, hydrogen, carbon dioxide, nitrogen, boiled water)
2. The mixture experienced an electrical discharge to replicate lightning (energy source)
3. It was left to cool for a week
4. Analyzed and found to have traces of simple organic molecules (urea and amino acids)
5. Formaldehyde and hydrogen cyanide (simple compounds) were found, then later they combined and produced the organic molecules

Question 6

weaknesses of the Urey-Miller experiment

Answer 6

The question of where DNA and RNA was originated is NOT explained by their theory.
Not certain of chemical composition of the early atmosphere

Question 7

endosymbiotic theory

Answer 7

Eukaryotic cells evolved when multiple cells combined into one (symbiotic relationship). points out that the mitochondria and the chloroplast are organelles which were once free living cells. They were both prokaryotes which were engulfed by phagocytosis.
The cells did not die but survived in the inner cell and evolved to perform functions in the cell.(they function as a single organism)

Question 8

explain the endosymbiotic theory

Answer 8

large cells preyed on smaller cells by letting their outer cell membrane fold inwards to form double membrane and vacuole like structures in which there prokaryotic prey can be engulfed.
The prokaryotic cell inside the larger cell could still perform aerobic respiration
The eukaryotic cell would give organic compounds to the prokaryotic cell which could then use to produce energy in the form of ATP.
The prokaryotic and eukaryotic cell lost the ability to live without each other

Question 9

Evidence of the Endosymbiotic Theory:
Mitochondria and Chloroplast (5)

Answer 9

Membranes: both have double membrane organelles.

Antibiotics: can affected/ harm the mitochondria and chloroplast.

Division: the organelles reproduce independently by splitting in two (like binary fission).

DNA: is a loop which resembles the DNA of certain prokaryotes.

Ribosomes: the organelles have their own 70s ribosomes