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Asexual
Offspring are genetically identical
Sexual
There is variation in offspring to parents
Importance of cell division
Importance of cell division
1. Reproduction
2. Repair and Replacement of damaged or dead cells.
3. Growth: increase in cell numbers causing growth, not increase in cell size
Cell cycle = series of events taking place in cell as grows and divides.
Cell spends most time in interphase, it grows. Replicates chromosomes, prepares for cell division.
M Phase
M Phase
Where cell actually divides into 2 copies.
Resulting cells = daughter cells, each enter own interphase, begins new round of cell cycle.
Daughter cells: Identical cells formed when a cell undergoes division by mitosis.
As eukaryotic cells grow and divide they move through 3 stages; interphase, mitosis and cytokinesis. Cell grow and prepare to divide during interphase. Division starts during mitosis and cytokinesis.
It depends how much time each phases last,
Ex: embryonic cell divides rapidly.
Some cells may take about 30 h per cycle.
Specialized cells, like adult nerve cells may never divide at all.
Cell Processes
Cell Processes
Chemical and water needed by cell to carry life processes
What are those again?
Waste products need to be eliminated by cell
These needs are met by the 2 processes diffusion and osmosis
Osmosis
Osmosis
Diffusion
Diffusion
Movement of chemicals across the cell membrane from of high concentration to area of low concentration
Ex: Axe spray in a change room
Cell Size
Cell Size
Diffusion and osmosis take time
Larger cell = longer process
Therefore smaller cell size = quicker, more efficient eliminating wastes, accumulation of necessary substances.
The 3 stages
The 3 stages
Interphase (3 stages of its own)
Mitosis (4 phase of its own)
Cytokinesis
Interphase
Interphase
The longest for most cells but not a resting stage. During interphase, cell carries life activities except division. These include growth, cellular respiration and any specialized functions of all cell type.
When cell prepares to divide, strands are duplicated so there are 2 identical strands of genetic material.
Has 3 stages of its own:
Cell busy with life activity (building proteins, taking energy and prepares for cell divisions by growing (producing new proteins and organelles) and by synthesizing copies of its DNA (the chromatin).
Chromosomes in long, thin, invisible strands.
1. G1 Phase
1. G1 Phase
First stage of interphase
Creating RNA and proteins need for cell growth and DNA duplication occurs.
Stage is then followed by S Phase
However Some cells like.... 👉👉
2. S Phase (stands for DNA synthesis)
2. S Phase (stands for DNA synthesis)
DNA Duplication occurs
3. G2 Phase
3. G2 Phase
Organizes and compress genetic materials
Cell leave starts mitosis and Completes division.
nerve cells stop divides and enters G0 phase, a resting stage without continue S Phase where DNA duplication occurs.
Centrosome Duplication
Centrosome Duplication
Centrioles duplicates around nucleus
then move to opposite sides of cell
Nucleus starts dissapear
Chromosomes starts pairing up/ organize together at where nucleus was. 👇
Microtubules, strings starts appearing from centrioles
👈
Chromosomes pairing ups in x-shapes and stay attached to each other
These are called the chromatids. One copy is the
right leg and arm
left leg and arm
Middle is called centromere, which links pair of chromatids together.
Mitosis in animal cells are very similar to mitosis in plant cells👆
Aka karyokinesis
Division of genetic material
Result in 2 genetically identical daughter cells
Has 4 phases of his own
- Use acronym PMAT
Prophase
Metaphase
Anaphase
Telophase
1. Prophase:
1. Prophase:
Chromosomes shorten, thicken
Each chromosomes made up of sister chromatids held together by cetromere
Nuclear membrane breaks down
2. Metaphase
2. Metaphase
Chromosomes line up along middle of cell (equator)
Spindle fibres are visible
3. Anaphase
3. Anaphase
Centromere splits and each chromtids, now called a "daughter chromosome" migrates toward opposite poles, pulled by spindle fibres
4. Telophase
4. Telophase
Chromosomes is thin and longer, no longer visible under light microscope
Nuclear membrane forms
Rate of mitosis
Rate of mitosis
Different parts of an organism experience difference rates of mitosis
Ex: an onion root tip is where growth occurs and therefore the cells divide frequently ever 12-36 hours.
In human skins cells (that brush off) or intestinal cells (that are btoken down by the digestive process) have high rates of mitosis, whereas red blood cells may last for months.
Cytokinesis
Cytokinesis
Cytoplasm divides, producing 2 daughter cells
In animal cells, cytoplasm pinches apart
In plant cells, a cell plate form
Checkpoints in the Cell Cycle
Checkpoints in the Cell Cycle
Specialized proteins keep the nucleus informed as to the status of the cell and its environment
The nucleus then instructs the cell:
To divide or not to divide
Cells remain in interphase if
Cells remain in interphase if
Signals from surrounding cells say no
Nutrients are in short supply
DNA has not been replicated
DNA is damaged
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