LSM1401 Notes Summary (2a) © Lim Fang Jeng
Cell Biology II
Study of Eukaryotic and Prokaryotic growth
Growth & Reproduction
Growth
– Individual organism and population of organisms
– In cellular level, it often refers to cell division and related to reproduction Reproduction
- Process of producing new generations, continuing life Mechanisms of growth and reproduction
Organisms Mechanisms
Prokaryotes
- Binary fission (majority)
- Buddi g or… –Gram –ve bacteria - Frag e tatio or… - photosynthetic - Spores (Conidia) –Gram +ve bacteria Eukaryotes - Mitosis
- Meiosis
Prokaryotic cell cycle is different from Eukaryotic cell cycle
Prokaryotic Cell Cycle
- Cell Growth & Binary fission - Only have single circular DNA - Binary fission
o Symmetrical process – one parent two daughter cells o 3 steps
Replication of DNA – slower than overall cell division
Synthesis
Separation
Eukaryotic Cell Cycle
Interphase (G1,S,G2)
- Longest part of the cycle
- Cell roughly double in mass due to replicated DNA and cytoplasmic component
- Chromosome will have two sister chromatids - Chromosome consists of DNA which is
wrapped up around histones.
- Most of the cells will remain in G1 while they are undergoing biomolecules synthesis.
- Cells which will be divided will enter S to undergo DNA replication
- Consists of molecular brake in G1, cells will detect the
atured ells that o ’t e di idi g a d they ill stop at i terphase.
LSM1401 Notes Summary (2a) © Lim Fang Jeng Mitosis
- Bipolar spindle apparatus (at transition from Prophase Metaphase) o Microtubules found, overlaps at the equator
o Move chromosomes during mitosis - Four stages
o Prophase
Condensing of duplicates chromosome (early)
New microtubules formed and nuclear envelop breaks up (late) o Metaphase
Spindle fibres formed and attached to sister chromatids of each chromosome [Transition]
Chromosomes line up at equator
Maximally condensed chromosome o Anaphase
Sister chromatids of each chromosome pulled apart o Telophase
New nuclear membrane formed
Chromosome decondense
Two nuclear membranes formed and separated (cytokinesis)
- Two daughter nuclei of same chromosome number produced from one parent nucleus - Cytoplasmic division
o Cytokinesis – occurs in late anaphase or end of telophase o Cell plate formation (plants) and Cell cleavage (animals) o Ring of microfilaments will cleave the cells into two
Lost Control (Molecular Brake)
- Checkpoint proteins
o Growth factors - Some cells keep dividing for growth and renewal o Other proteins - Some cells will stop appropriately
- If the cells which the molecular brake fails to stop – cancers - Cancer cells often can be transferred from one part to another part
Population Growth
- Doubling time – period needed for cells to double
- Low doubling time= High growth rate (Doubling time/hour)
Batch culture
- Growth in bioreactors - Phases
o Lag phase
Preparing for growth
Adapting to change
Adjusting metabolism o Log phase
Microtubule (cytoskeleton) of bipolar spindle (during Metaphase)
centriole
LSM1401 Notes Summary (2a) © Lim Fang Jeng
Exponential growth
� = 2�, N= number of cells divided; n= number of generations o Stationary Phase
Average population size = constant (dying rate=production rate)
Stability depends on
Depletion of essential nutrients
Accumulation of toxic materials o Death phase
Cells dying
Vital cellular functions cease
Continuous Culture
Normally we do not desire cells to arrive death phase Nutrients need to be continuously supplied
- Keep concentration of essential nutrient low to control the growth rate - Number of cells in population will not change
- Can be kept running for long period of time - In nature, we are all in continuous culture
Requirements for Growth
Temperature
Optimal growth temperature
- Temperature which a microbe grows best
- Enzyme-catalysed reactions will work best ( Not being affected) 3 groups of special organisms
- Thermophiles - Grow best at high temperature - Mesophiles - Grow in moderate temperature - Psychrophiles - Grow best in low temperature
pH
- Most cells grow best in neutral range
- Acidophiles – Grow best in acidic condition -Gastrointestinal organisms - Alkaliphiles – Thrive in alkaline environments
- They can control intracellular pH by pumping H+ out of cells
Osmotic Pressure
- Most of the time, bacteria will live in hypotonic environments o So they need cell wall to withstand turgor pressure - Plasmolysis
o Shrinking of cell due to water loss
- Halophiles – Can withstand high salt concentration
LSM1401 Notes Summary (2a) © Lim Fang Jeng
Light
- Important for phototrophs
Chemical growth factors
- Water, Carbon, Oxygen, Nitrogen, Phosphorus, Sulphur, Trace elements, Special growth vectors - Carbon
o Autotrophs – Obtain carbon from carbon dioxide o Heterotrophs - Obtain carbon from organic molecules - Oxygen
o Major chemical components - Special Growth Factors
o Amino acids and vitamins - Trace elements
o Metal ions – serve as cofactor of enzymes
