2.2 All Cells Arise From Other Cells Flashcards
Which type of cell has the ability to divide?
Eukaryotic
When in the cell cycle does DNA replication occur?
Interphase
What is mitosis?
Eukaryotic cell divides to produce two daughter cells with an exact copy of the DNA of the parent cell
In what way are daughter cells similar?
They have identical copies of DNA produced by the parent cell
What is the order of the cell cycle?
Interphase Prophase Metaphase Anaphase Telophase (Cytokinesis)
What is cytokinesis?
Division of the cytoplasm
Produces two new cells
What can uncontrolled cell division lead to?
Formation of tumours and cancers
What’s the main objective of most cancer treatments?
Prevent DNA from replicating
by inhibiting the metaphase stage of mitosis by interfering with spindle formation
By what process do prokaryotic cells divide?
Binary fission
What does binary fission involve?
Replication of the circular DNA and of plasmids
Cell membrane begins to grow between the DNA molecules and punches inwards, dividing the cytoplasm
What is produced by cytokinesis in prokaryotic cells?
Two daughter cells with a single copy of the circular DNA
A variable number of plasmids
Why don’t viruses undergo cell division?
They are non-living
How do viruses replicate?
Attach to the host cell with the attachment proteins on their surface
Inject nucleic acid into the host cell
The genetic information of the injected viral nucleic acid provides the instructions for the host cell to start procuring the viral components, nucleic acid, enzymes and structural proteins
These are then assembled into new viruses
What is interphase?
Cell is actively synthesising
Chromatids not visible
What is prophase?
First stage of mitosis
Chromatids visible as they get shorter and more dense and so darker
The nucleolus disappears
The nuclear envelope breaks down
Chromosomes left free in the cytoplasm are drawn towards the equator of the cell by spindle fibres attached to the centromere
What is metaphase?
Second stage of mitosis
Chromosome are seen to be made up of two chromatids (joined by centromere)
Spindle fibres pull chromosome (attached to centromere) to arrange across the equator of the cell
What is anaphase?
Third stage of mitosis
Where chromosomes move apart and so the number of chromosomes is doubled
Spindle fibres pull them towards the poles
The energy for this is provided by mitochondria which gather around the poles
What is telophase?
The last stage of mitosis
Nuclear membrane reforms as two cells are formed
The chromosomes are no longer visible, leaving only widely spread chromatin
What is a benign tumour?
Enclose in a capsule
Grown in centre
Do not invade surrounding tissue
What is a malignant tumour?
Grow at the edges
Invade surrounding tissues and organs
(metastasis can occur)
What is metastasis?
Where cells may break off and set up secondary tumours elsewhere
What is a tumour?
Mass of cells formed by uncontrolled cell division
What is a chromosome?
A thread like structure of nucleic acids
can be / or X
Put nucleus, genes, DNA, cell and chromosomes in order of size? (big to small)
Cell, nucleus, chromosomes, genes, DNA
What must happen before a cell can divide?
Organelles must replicate (mainly mitochondria and ribosomes)
DNA must replicate
Cell must grown
Why is mitosis an important process?
Grow new cells
Repair damaged tissue
Asexual reproduction
What are the three stages of interphase?
G1- first growth phase
S- synthesis phase
G2- second growth phase
Describe the structure of a chromosome?
2 sister chromatids with the same DNA joined at the centromere
(chromosome can mean one strand)
What does time taken for mitosis depend on?
Cell type
Environmental conditions
What is mitotic index?
The proportion of cells in a tissue sample that are undergoing mitosis
What two things could a high mitotic index in a stable animal tissue indicate?
Tissue repair
Cancerous growth
What is the range for mitotic index?
0-1
0%-100%
How do you calculate mitotic index?
Number of cells with visible chromosomes / total number of cells observed
What are the stages of developing cancer?
Early tumour
Enlarging tumour, develops blood and lymphatic vessels
Tumour cells squeeze into the blood and lymphatic vessels
Tumour cells circulate
Tumour cells Asher to blood vessel walls and squeeze through to form distant metastasis
Metastasis in lymph node
What do you call something that causes cancer?
Carcinogens
List some carcinogens?
Smoking Radiation Genetics Chemicals Food Age Random
How can genetics effect chances of getting cancer?
Tumour suppressive genes act to stop mitosis from happening
Porto-oncogenes make mitosis happen
What is the Heyflick limit?
The amount of times a cell can replicate before dying
Cancer cells don’t have one
What are the three main treatment methods for cancer?
Chemotherapy
Radiotherapy
Surgery
How does chemotherapy treat cancer?
Chemical substances are used to kill cancer cells
How does radiotherapy treat cancer?
Radiation kills cancer cells
How does surgery treat cancer?
The cancer cells are physically removed
What are the key advantages of chemotherapy?
Shrinks and slows tumour growths
Reduces chance of cancer returning
Can make surgery viable
Frequent medical checks are reassuring
What are the key disadvantages of chemotherapy?
Frequent treatment is tiring
Doesn’t effect everyone in the same way so may no work as well for some
Many side effects (infection, weakness, bleeding, blood clots, anaemia etc)
What are the key advantages of radiotherapy?
Many cancer cells killed
Shrinks the tumour
No anaesthetic required (safer)
Stimulates an immune response
What are the key disadvantages of radiotherapy?
Damages surrounding tissue
Can’t kill tumour cells that aren’t seen on scans
Can’t kill all cells
Poor healing
What are the key advantages of surgery?
Removes cancer cells which extends life
Symptoms like pain and digestive issues may fade
If cancer returns, chemo can then be used to control symptoms
What are the key disadvantages of surgery?
Hospital recovery time required
Up to a year to fully recover
Side effects such as diabetes and digestive issues
Risks involve bleeding, infections, leaks and anaesthetic complications
Describe the process of prokaryotic cell replication.
Cell is respiring and creating proteins
DNA replicates and remains attached to the cell membrane
Cell lengthens and DNA moves apart to the separate ends
The centre of the bacteria contracts which starts to spectate the cell
A cell membrane and cell wall forms across the cytoplasm to separate the cells
Cell separated into 2 daughter bacteria cells with identical DNA
Describe prokaryotic cell reproduction (simply).
Respiring cell creating protein DNA replicates Cell lengthens, DNA separates Centre contracts Cell membrane and wall separates the cell 2 daughter bacteria cells
What are the three main structures in a virus?
Protein coat
Capsid
Genetic material
Why can’t viruses undergo cell division?
They’re non-living
What must be done to facilitate the replication of a virus
The injection of the viruses nucleic acid into the cell
Describe the process of viral replication.
The virus attaches to the target cell
The cell engulfs the virus (endocytosis)
Viral contents are released, viral RNA enters the nucleus where it’s replicated by the viral RNA polymerase
Viral mRNA is used to make viral proteins
New viral proteins are made and released into the extra cellular fluid and the cell continues to make new viruses
By what process does a cell engulf a virus?
Endocytosis
What is cancer?
A group of diseases caused by a growth disorder in cells
Result of damage to the genes that regulate mitosis and the cell cycle
Leads to uncontrolled growth and division of cells
What is the order of the cell cycle?
Interphase
Nuclear division
Division of the cytoplasm
When does a tumour become cancerous?
When it changes from benign to malignant
