1.5 origin of cells

Question 1

where do cells come from?

Answer 1

• cells are made from pre-existing cells
• not spontaneous generation

Question 2

how did Louis Pasteur falsify the theory of spontaneous generation?

Answer 2

• use of swan-necked flasks
• boiled broth only develops microbes when direct contact

Question 3

where did cells come from in the first place?

Answer 3

• cells must have arisen from non-living material rather than other cells
  1- mimic of earth’s early conditions - Carbon compounds such as sugars and amino acids that were needed for life were produced
  2 - deep sea vents There is hot, gushing water filled with inorganic
  chemicals with necessary energy to assemble into carbon compounds into polymers
  3 - Genes are made of DNA and enzymes are needed to replicate DNA so it can be passed on to offspring. - RNA is thought to have been the initial genetic material for life on Earth as it can store hereditary information, it is self-replicating and act as a catalyst for chemical reactions.

Question 4

what is the endosymbiotic theory?

Answer 4

• Organelles evolved from independent prokaryotes that were engulfed by larger cells by endocytosis.
• These smaller cells were not digested and instead survived, and formed a mutualistic relationship.
• The smaller cells continued to carry out their functions: cell respiration and photosynthesis

Question 5

what is the evidence for the endosymbiotic theory?

Answer 5

• Mitochondria and chloroplasts have many similar characteristics as prokaryotes.
• These include: they grow and divide like cells; they have loops of naked DNA; and they contain 70S ribosomes.
• Mitochondria and chloroplasts have the double membranes expected when taken into a vesicle by endocytosis.
• Thylakoids in chloroplasts are similar to prokaryotes containing chlorophyll.