2.6 Cell divison, cell diversity and cell diffentiation Flashcards
What is the definition of tissue?
A group of similar cells carrying out a specific function.
What is the definition of an organ?
A collection of tissues that work together to carry out a specific function.
What are the different tissue types in a animals?
- epithlial (skin, gut/airways lining)
- connective (bone, ligament cartilage)
- muscle (smooth, cardiac, skeletal)
- nervous (neurons)
What are the different tissue types in plants?
- epidermal (protective covering over leaves, stems and roots)
- vascular (xylem and phloem)
- meristematic (stem cells, found at root and shoot tips)
What are the different phases in the cell cycle?
1) G1 (growth one)
2) S
3) G2 (growth two)
4) M (mitosis/not interphase)
What happens in G1?
- cells grow and increase in size
- transcription of genes to make RNA
- organelles duplicate
- biosynthesis is enzymes needed to make DNA
- p53 (tumour suppressor) gene helps control this phase
What happens at the G1 checkpoint?
Control mechanisms ensure that the cell is ready to enter s-phase.
This is the point of no return, if it does not pass this check point it will enter G-0
Once passed, mitosis will occur.
What is the G-0 phase?
A phase triggers during G1 checkpoint, if it does not pass.
In this phase, it can either undergo apoptosis, differentiation or senescence.
Some cells which have a long cell life may stay in this stage for a very long time.
What happens in the S-phase?
This is when DNA replicates; this phase is rapid as it when he DNA base pairs are exposed, they are more susceptible to mutagenic agents, hence reduces the chances of mutations.
Housekeeping genes are replicated first, and then the inactive genes are replicated last.
What happens in G2?
The cell continues to grow, mitochondria and chloroplast also begin to be produced.
What is the name of the protein which regulates checkpoints in the cell cycle?
Cyclin
What are cyclin dependant kinases?
Enzymes which require a cyclin to work, and are used to active the next stage of the cell cycle.
So without cyclin, they will not be able to pass into the next stage so they act as a means to stop the cell cycle and prevent any cancerous cells from dividing.
How does P53 suppress tumours?
P53 is an enzyme which finds and binds to damaged DNA, inhibiting the cell cycle.
It then produces a CDK (cyclin dependant kinase)inhibiter which inhibits the CDK from activiting its substrate and passing the checkpoint.
How do enzymes lower the activation energy required?
IN synthesis reactions, enzymes reduce the repulsion between the molecules, reduciong the required energy.
In break down reactions, enzymes add strain on the bonds, allowing them to be broke easier.
What is meant by saturtion in terms of enzymes?
It means that all active sites of all the enzymes are in use, so the rate of reaction cannot increase past this point, unless more enzymes are added.
