Chapter 8.5 Flashcards
examples of cells that constantly divide
- the cells at the tip of plant’s roots
2. stems cells in bone marrow continue to produce new blood clls
egs of cells that stop dividing
1, skin cells around a wound stop dividing once the healing is complete
2. brain cells rarely divide once they mature
What two groups of proteins guide a cell’s progress through the cell cycle
Cyclin : fluctuate in predictable ways during each stage:
2. proteins that bind to each cyclin: translate these fluctuations into action by activating the transcription factors that stimulate entry into the next stage of the cell cycle
The interactions of the signaling proteins ( cyclin and the proteins that bind to it)serve as what
checpoints : they ensure that cello does not enter one stage until the previous stage is complete
What are the mechanics of the checkpoints of the cell cycle
A cell that fails to pass a checkpoint correctly will not undergo the change in cyclin concentrations that allow it to progress to the next stage
G1 checkpoint
screens for dna damage
S phase checkpoints
ensures that dan replication occurs properly
G2 checkpoint
Is the last point before the cells begins mitosis
metaphase checkpoint
ensures that all chromosomes are aligned and that the the spindle fibres attach correctly to the chromosomes
Why are checkpoint timing essential
too little cell division - an injury would go unprepared
Too much Cell division: an abnormal growth forms
TUMOR
an abnormal mass of tissue
2 types of TUMORS
- BENIGN TUMORS
2. MALIGNANT TUMORS
BENIGN TUMORS
usually slow growing and harmless, unless they get large enough to disrupt nearby tissues or organs
What prevents a tumor from spreading
a tough capsule of connecting tissue surrounding the tumor
egs of benign tumors
warts and moles
MALIGNANT TUMORS
- invades adjacent tissue
why do malignant tumors spread
because it lacks a surrounding capsule, making it likely to metastasize
METASTASIZE
cells can break away from the original mass and travel in the bloodstream or lymphatic system to colonize other areas of the body
CANCER
a class of diseases characterized by malignant cells
The mechanics of cancer
Cancer begins when a single cell accumulates genetic mutations that cause it to break through its death and division controls. As the cell continues to divide a tumor develops. All tumors grow slowly at at first because only a few cells are divine, but not all cells continue to grow at the same rate.
How do cancer cells differ from normal cells
- uncontrolled cell division (no connective tissue capsule)
- they look different: rounder, cell membrane is more fluid, loses some specialized features from parent cells, may have multiple nuclei
- they are immortal: they ignore the clock that limits normal cells to about 50 cell divisions: they have high telemorase
- GROWTH FACTORS: cancer cells divide even in their absence
- They lack CONTACT INHIBITION
- They lack ANCHORAGE DEPENDENCE
( explains why metastasis occurs) - does not undergo apoptosis when badly damaged
- They send signals to develop new blood vessels enabling a tumor to have its own blood supply
Where does cellular clock reside
in TELOMERES
what are TELOMERES
The encoding dan at the tips of eukaryotic chromosomes
What do TELOMERES do
They consists of hundreds to thousands of repeats of a specific DNA sequence, at each cell division, the elopers loose nucleotides from their ends, so that the chromosomes become shorter. After about 50 divisions all that loss signals division to cease in a normal cell.
TELOMERASE
cells that produce the enzyme telomerase can continually add dan to chromosome tips. their chromosomes stay long which enables them to divide beyond the approx 50 division limit
GROWTH FACTORS
proteins that stimulate cell division
e.g. of growth factor
epidermal growth factor stimulate cells to divide to produce new skin
CONTACT INHIBITION
normal cells stop dividing when they touch on another in a one -cell thick layer in a culture
ANCHORAGE DEPENDENCE
normal cells only divide when attached to a solid surface
What macromolecule control the cell cycle and apoptosis
proteins. genes encode proteins
What 2 classes of cancer- related genes play a role in the development of cancer.
- oncogenes
2. tumor supressor gene
ONCOGENES ( onko, mass or lump)
Mutated variants of genes that normally stimulate cell division
The normal versions of oncogenes are called
PROTO-ONCOGENES
PROTO-ONCOGENES
encode many types of proteins
If the protein is abnormally active or expressed at too high a concentration, the cell cycle will be accelerated, and cancer may develop
why are oncogenes especially dangerous
because only one of the two versions in a cell (from dad and mom) needs to be damaged for cancer to develop. The oncogenes are
The oncogene’s protein
Is abnormal and is an accelerator that overrides the normal protein encoded by the proto-oncogene
TUMOR SUPPRESSOR GENES
encode proteins that normally block cancer development: they promote apoptosis or prevent cell division. they block cancer from developing.
. Unlike oncogenes both of the versions of this gene must be damaged for cancer to develop: as long as one tumor suppressor gene is functioning , the cell continues to produce protective proteins
The more oncogenes or mutated tumor suppressor genes in a person’s cell
the higher the probability of cancer
How is the spread of cancer usually described
In stages
Why are chemotherapy and radiation considered blunt tools to treat cancer
because they target all rapidly dividing cells whether cancerous or not
egs of normally rapidly diving cells
bone marrow, digestive tract and hair follicles
What prevents normal cells from dividing when they are not supposed to?
Interactions between signaling proteins produces checkpoints in the cell cycle to ensure that cells do not divide at improper times.
What happens at cell cycle checkpoints
At cell cycle checkpoints, the cell cycle is controlled, ensuring that each stage of the cycle is completed before the next stage begins. A cell will only proceed into mitosis if the G1, S, and G2 checkpoints have been successfully passed. If they have not, the cell may stop or suspend the cell cycle, or may enter apoptosis and die.
. What is the difference between a benign and a malignant tumor?
Benign tumors do not spread to other areas of the body and do not invade nearby tissues. A malignant tumor does invade nearby tissues and may metastasize to colonize other areas of the body.
How do cancer cells differ from normal cells
Cancer cells are different from normal cells in that they have lost the normal controls on the cell cycle. Cancer cells therefore divide in an unregulated fashion. Cancer cells look different from normal cells and lose some of the special features of the parent cell. Cancer cells may have their own growth factors that signal when they should divide. Cancer cells lack contact inhibition; in addition, they are essentially immortal and lack apoptosis. Cancer cells can stimulate the growth of new blood vessels that supply them with nourishment and remove wastes.
What is the relationship between mutations and cancer
Mutations cause changes to the signaling proteins that act as checkpoints on division or that signal apoptosis. These changes result in cells that continually divide and do not undergo cell death.
How does a person acquire the mutations associated with cancer?
Mutations can be inherited or caused by exposure to mutagens such as UV radiation or tobacco chemicals. Some sexually transmitted viruses also cause cancer. Lifestyle choices such as eating right and exercising might help prevent mutations associated with cancer.
Distinguish among the treatments for cancer
Surgical tumor removal is a direct and local treatment that removes just the cancerous mass and often nearby lymph nodes. Chemotherapy and radiation treatments are both “blunt” tools that target any rapidly dividing cell types, though radiation treatment is much more localized.
