Unit 1.5b Flashcards
Why can living organisms reproduce?
Because our cells can divide
How long does it take prokaryotes, like bacteria, to divide?
It can be as short as 20 minutes
How long does it take eukaryotes to divide?
On average, it takes around 24 hours
Why does it take so long for eukaryotes to divide in comparison to prokaryotes?
Because they go through the cell cycle, which is more complex
Why is the cell cycle complex in comparison to other ways cells divide?
It’s more complex due to organelles and the cell having lots of chromosomes containing DNA and proteins
What is the complex containing DNA and proteins in chromosomes called?
Chromatin
Why is cell division important in multicellular organisms?
It allows cells to grow and replace dead cells, which therefore repairs damaged tissues
What is the cell cycle?
It’s to process in which a cell goes through to duplicate its content
What is the product of the cell cycle?
Two genetically identical daughter cells
Do all cells need to be replicated at the same rate?
No, some cells will be replicated more often than others due to the need for being replaced and some will never replicate
Why do some cells never divide?
Some cells never divide as they are so specialised
What causes cells in the liver to divide?
They must be stimulated
How is the cell cycle regulated?
Cell cycle is regulated by control system which responds to intra an extra cellular signals
What would happen if the rate of the cell cycle is altered?
There would be serious consequences
What is a proto-oncogene?
It’s a normal gene often involved in the control of cell growth and division
What is formed when a proto-oncogene mutates?
A tumour-promoting oncogene is formed
What do tumour promoting oncogenes cause?
They cause the cell to divide in an uncontrolled and unregulated manner
What is the result of an uncontrolled increase in the cell cycle?
Tumour formation, as without regulation, the cells are not recognised and attacked by the immune system which leads to cancer
What is the result of an uncontrolled reduction in the cell cycle?
Degenerative diseases as neurons re-enter the cell cycle, but cannot complete it which means the cell will die
What are the two main phases the cell cycle is broken into?
The interphase and the mitotic (M) phase
What happens during the interphase?
Cell growth and DNA replication
What occurs during the mitotic phase?
Segregation of replicated chromosomes, and the division of the cytoplasm, which leads to the formation of daughter cells
What is three sub phases, make up the interphase?
- G1
- S Phase
- G2
What occurs during the G1 phase?
This is the first period of growth where proteins and organelles are synthesised. As the cell is active, it carries out metabolic processes.
What occurs during the S phase?
Cell growth continues
The nuclear DNA replicates
Chromosomes are copied in preparation for mitosis leading to chromosomes becoming sister chromatids
What occurs during the G2 phase?
This is the second growth period where proteins and organelles are again synthesised
By the end of interphase, what has happened to the parent cell?
The size of the parent cell will have doubled
Is interphase part of mitosis?
No, interphase is part of the cell cycle
What is the mitotic phase split into?
It’s split into mitosis and cytokinesis
What happens during mitosis? (tiny summary)
The nucleus and its contents divide equally
What happens during cytokinesis? (Tiny summary)
Separation of cytoplasm into daughter cells
In order, what are the four stages of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
How are the four stages of mitosis recognised?
They are recognised by their appearance, and the location of the cells chromosomes in its nucleus
What occurs during prophase?
- DNA condenses into chromosomes with two sister chromatids
- The nuclear membrane breaks down and spindle microtubules extend from the MTOC by polymerisation
- The spindle fibres attach to the chromosomes at the kinetochores in the centrosome
What is the kinetochores?
It’s the joining site in the centromere
What occurs during metaphase?
Chromosomes align at the metaphase plate
What is the metaphase plate?
It’s the arrangement of chromosomes at the cell equator
What occurs during anaphase?
Spindle microtubules shorten by depolymerisation separating the sister chromatids and pulling them to opposite poles
What occurs during telophase?
-Chromosomes decondense and nuclear membranes form around them
-This is also when is cytokinesis occurs
What occurs during cytokinesis in animal cells?
A protein ring around the centre of the cell contracts pinching it into two genetically identical daughter cells each with one nucleus
What equation allows us to work out the percentage of cells in a sample undergoing mitosis?
(Cells in mitosis (PMAT) / total number of cells) x 100
