1.5 Syllabus
U1. Cells can only be formed by division of pre-existing cells.
Relate this to cell theory
-Mitosis results in identical diploid daughter cells
- Cells are highly complexed structure and no mechanism has found for producing cells from simples subunits.
-All known examples of growth be it of a tissue, growth, population all result of cell division
-Viruses produced from simpler subunits but does not contain cells and can only produced inside the host cells that they have infected.
- All living things are composed of cells
- Cell is the smallest unit of life
- Cells only arise from pre-existing cells
-Mitosis results in identical diploid daughter cells
- Cells are highly complexed structure and no mechanism has found for producing cells from simples subunits.
-All known examples of growth be it of a tissue, growth, population all result of cell division
-Viruses produced from simpler subunits but does not contain cells and can only produced inside the host cells that they have infected.
U2. The first cells must have arisen from non-living materials.
1. Production of carbon compound ex) sugars and amino acids
2. Assembly of Carbon Compounds into polymer
3. Formation of membranes
- Passed steam through mixture of methane, hydrogen, ammonia. (These mixtures thought to be representative of the atmosphere of early Earth)
- Electrical charges used to stimulate lightning.
- Found amino acids and other carbon compounded needed for life were produced.
2. Assembly of Carbon Compounds into polymer
- Possible site for origin of 1st carbon compound is around deep-sea vents. Vents are cracks in the Earth’s surface.
3. Formation of membranes
- If phospholipids were among the first carbon compound, they would have naturally assembled bilayers readily form vesicles resembling plasma membrane of small cell
- Living organisms currently have genes made of DNA and use enzymes as catalysts.
- To replicate DNA and able to pass genes on to offspring, enzymes are needed
- However, genes are needed to make enzymes
- BUT RNA store information as same way compare to DNA but can self-replicate.
U3. The origin of eukaryotic cells can be explained by the endosymbiotic theory
-Endosymbiotic theory explains existence of several organelles of eukaryotes.
-Theory states that organelles such as (mitochondria and Chloroplast) originated as symbiosis between separate single-celled organisms.
1. Mitochondria: Aerobic respiration takes place and produce ATP
→ Mitochondria r free-living prokaryotic organisms that developed through aerobic cell respiration
2. Chloroplast: Site of photosynthesis
→Features that both evolved from independent prokaryotes: (Like prokaryotes)
→Double membrane -70s ribosome – Naked and circular DNA – Susceptible to antibiotics
→Reproduction via fission-like process – Can only be produced by pre-existing cells.
Endosymbiont: Cell which lives inside another cell with mutual benefit
-How is nucleus formed?
→ Prokaryotes grow in size and develops folds in its membrane to maintain efficient SA:VOL
→ Infoldings pinched off forming internal membrane
→ Nucleoid region enclosed in internal membrane and hence form nucleus
Related Question:
Q. Origin of eukaryotic cells according to endosymbiotic theory
Ans: Mitochondria and chloroplasts are similar to prokaryotes. Host cell takes in another cell by endocytosis but did not digest the cell and kept the ingested cell alive. Chloroplasts and mitochondria were once free-living organisms. DNA loop in chloroplast/mitochondrion. Binary fission of chloroplast. Double membrane in around chloroplast/mitochondrion. 70s ribosomes in chloroplast/mitochondrion.
-Theory states that organelles such as (mitochondria and Chloroplast) originated as symbiosis between separate single-celled organisms.
1. Mitochondria: Aerobic respiration takes place and produce ATP
→ Mitochondria r free-living prokaryotic organisms that developed through aerobic cell respiration
2. Chloroplast: Site of photosynthesis
→Features that both evolved from independent prokaryotes: (Like prokaryotes)
→Double membrane -70s ribosome – Naked and circular DNA – Susceptible to antibiotics
→Reproduction via fission-like process – Can only be produced by pre-existing cells.
Endosymbiont: Cell which lives inside another cell with mutual benefit
- Larger cell takes in smaller cell (Mitochondria) by endocytosis so smaller cell is inside the vesicle in cytoplasm of larger cell = Larger cell that only respire by anaerobic respiration took small cells that can respire by aerobic by endocytosis since aerobic respiration is more efficient.
- Instead small cell being digested, it keeps alive and performs useful function.
- Mutual benefit= Smaller cell supplied with food by larger cell
-How is nucleus formed?
→ Prokaryotes grow in size and develops folds in its membrane to maintain efficient SA:VOL
→ Infoldings pinched off forming internal membrane
→ Nucleoid region enclosed in internal membrane and hence form nucleus
Related Question:
Q. Origin of eukaryotic cells according to endosymbiotic theory
Ans: Mitochondria and chloroplasts are similar to prokaryotes. Host cell takes in another cell by endocytosis but did not digest the cell and kept the ingested cell alive. Chloroplasts and mitochondria were once free-living organisms. DNA loop in chloroplast/mitochondrion. Binary fission of chloroplast. Double membrane in around chloroplast/mitochondrion. 70s ribosomes in chloroplast/mitochondrion.
A1. All evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on earth.
Louis Pasteur designed an experiment to test whether nutrient broth could spontaneously generate microbe life.
-Microbe growth only occurred in experiment 1
Conclusion: Emergent bacterial growth only occurred in experiment 1 and did not spontaneously occurred
Related Question:
Q. Pasteur's Experiment
Ans: Spontaneous generation is life appearing from pre-existing life. Both used in flasks and is boiled in some flasks and is boiled in some flasks to kill microbes. Microbes did not appear in flasks of boiled broth. After necks of flasks were snapped, boiled broth became cloudy = Growth of microbes. Because microbes form the air contaminated the boiled broth. Curved necked allowed indirect exposure to air but prevented entry of microbes.
- Make nutrient broth by boiling water containing sugar and yeast
- Set 2 experiments and add nutrient broth to both of the flasks and bent the neck of flask into bent shape
- Each flask was then heated to boil the broth so that all existing microbes were killed
- After broth had been sterilized, Pasteur broke of swan neck from flasks only from experiment 1 exposing nutrient broth within them to air from above since outside air carries microorganisms into broth
- Flask in experiment 2 left alone
-Microbe growth only occurred in experiment 1
Conclusion: Emergent bacterial growth only occurred in experiment 1 and did not spontaneously occurred
Related Question:
Q. Pasteur's Experiment
Ans: Spontaneous generation is life appearing from pre-existing life. Both used in flasks and is boiled in some flasks and is boiled in some flasks to kill microbes. Microbes did not appear in flasks of boiled broth. After necks of flasks were snapped, boiled broth became cloudy = Growth of microbes. Because microbes form the air contaminated the boiled broth. Curved necked allowed indirect exposure to air but prevented entry of microbes.