A2.1 origins of cells

Question 1

conditions of early earth

Answer 1

-75-79 degrees
-no atmosphere
-surface was single global ocean
-lacked free oxygen
-no ozone layer
-high carbon dioxide, methane resulting in UV penetrations
-frequent lightning activity

Question 2

formation of carbon compounds

Answer 2

due to early earths atmospheric components, high temperatures, lightning and the gradual cooling, resulted in formation of many carbon compounds, e.g- amino acids, hydrocarbons, nucleic acids

Question 3

functions of life

Answer 3

cells are the smallest unit of self-sustaining life because they carry out all processes of life:
-metabolism
-growth
-reproduction
-response
-homeostasis
-nutrition
-excretion

viruses are non-living as they cant do the processes of life outside a host cell

Question 4

cell theory

Answer 4

-all organisms are composed of one of more cell
-cells are the smallest unit capable of life
-all cells come from pre-existing cells

Question 5

stages of first cell

Answer 5

1) formation of organic molecules (seen in Muller-Urey experiment)
2)formation of polymers
3)formation of cell membranes (phospholipid bilayers)
4)ability to self replicate (RNA)

Question 6

Muller- Urey experiment

Answer 6

evidence for the origin of organic carbon compounds
-aim= to stimulate conditions thought to be present on earth to determine the spontaneous formations of organic molecules
contained- water being heated, recreating water vapor, a stimulated atmosphere with the present gases and spark stimulating lightning, cooling, and collection the sample for analysis. Like a water cycle.
results: -identified several simple organic molecules in the collecting device known to exists in organisms e.g; long chains of hydrocarbons, amino acids
-fluid collected suggested life originated from primordial soup, water based sea of simple molecules

Question 7

reducing atmosphere

Answer 7

high amounts of hydrogen present , favorable in development of carbon compounds

Question 8

importance of formation of vesicle

Answer 8

• membrane formation said to be essential to origin of first cell
• membrane provides barrier between inside and environment

Question 9

formation of fatty acid bilayer

Answer 9

one of the first carbon compounds present on earth were simple group named fatty acids
- when present in water, displays a polarity since it has both hydrophilic and hydrophobic properties
-when large numbers of fatty acids are placed in water, they organize themselves into small double layer bubbles, vesicles

Question 10

compartmentalization

Answer 10

= the development of a boundary around a vesicle
-allows specialization of functions in different regions inside the outer protective fatty acid bilayer

Question 11

evidence for RNA as first genetic material

Answer 11

• RNA can assemble spontaneously from nucleotides
  -RNA can form copies of itself, acting as genetic material
  -RNA demonstrates ability to act as an enzyme, has some catalytic activity
• a type of RNA called ribozymes, in ribosomes are still used to catalyze peptide bond formation in protein synthesis and are highly active today
  -more simple than DNA

Question 12

evidence for last common universal common ancestor

Answer 12

• a universal genetic code shared by all cells
  -over 300 genes, or sections of genes common to all cells
  -common molecular processes in all cells, e.g= protein synthesis
  -similar transport mechanisms in and out of cells

-hypothesized that other forms of life have been demonstrated over the past 3.5 billion years, however not present today due to competitions with LUCA and descendants

Question 13

ways of dating fossils

Answer 13

1)radiometric techniques based on half life. (measuring amount of an isotope in a fossil and comparing it to amount taken up when organism was alive) = ABSOLUTE DATING
2)using particles of eroded and weathered rock or soil that may form layer and index fossils= RELATIVE DATING

Question 14

what is LUCA

Answer 14

LUCA existed 3.5 billion years ago
-is not thought to be the first life on earth, but the latest that is ancestral to all current existing life
-Luca is the stem for simple cells (like archaea, bacteria) and complex cells, (animals and plants)

Question 15

evidence for theory of origin of life found in hydrothermal vents

Answer 15

hydrothermal vents= structures formed when cracks of crust heated by magma, hot water rises with lots of minerals
evidence:
-worlds oldest fossilized traces of precipitates have originated from vents
-commonality of genetic sequences in organisms near vents (a single ancestor)
-mineral rich environment with both acidic and basic fluids, necessary for chemical reactions
- presence of hydrogen and carbon dioxide, resulting in reducing environment, needed for carbon compound formation