33 terms

Chapter 10: Biology

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Cells cannot grow indefinitely. List and describe the main reasons for this.
DNA overload: cannot direct all cell activities because the cell is too large
Ratio of SA to Volume decreases as the cell gets larger; this leads to a buildup of wastes inside the cell, and a lack of nutrients (oxygen and glucose) inside the cell

If this continues, the cell will die...the cell will divide instead
Compare and contrast sexual and asexual reproduction
asexual:all offspring are genetically the same; faster; bacteria, body
-can be bad because one disease can wipe out entire species
Sexual:offspring are genetically different from each other and the parent
-used in all sexually reproducing organisms (like plants, animals, etc.)
increases chances for survival;
· good genes are passed on (helps with evolution)
-slower/ need 2
Both: Results in new cells/organisms
- involve the passing down of DNA from parent cell (organism) to offspring
When do chromosomes become visible in the cell?
-prior to cell division
-Prophase is the first time visible (only visible in mitosis)
How is a eukaryotic chromosome different from a prokaryotic one?
Prokaryotic chromosomes are circular; not contained in the nucleus (just in the cytoplasm)
What is the eukaryotic cell cycle? Describe what it is, and then describe the important events that occur in each stage below.
Interphase: longest stage of the cell cycle
Includes three parts (G1, S, G2)
G1: cell grows
S (synthesis): DNA is replicated (copied)
G2: cell prepares for mitosis (makes structures and organelles needed for mitosis)
Prophase: first stage of mitosis (longest stage of mitosis)
Chromatin condenses (chromosomes become visible)
Nuclear envelope breaks down
Spindle forms and & centrioles separate
c. Metaphase: chromosomes line up along the equator of the cell (middle); the centromeres become attached to the spindle

d. Anaphase: sister chromatids (centromere splits) separate and start to move towards poles

e. Telophase: last stage of mitosis
i. Nuclear envelopes reform
ii. Spindle breaks down
iii. Chromosomes uncoil (cannot see the chromosomes by end of telophase)
iv. Cell membrane starts to pinch in

f. Cytokinesis: when the cell membrane and cytoplasm actually divides into two separate cells
Cytokinesis is the final stage of the cell cycle. How is it different in plants versus animals? Why?
In plant cells, a cell plate must first form (scaffolding) to allow the cell wall a place to form
In animal cells, the cell membrane simply pinches in
The cell cycle must be controlled, or cells divide uncontrollably. What are the main regulators for the cell cycle? Describe each one and how they work.
Cells stop dividing when they run into other cells
Cyclins (external and internal)
-internal (act on certain parts of cycle- stop metaphase if the chromosomes are not lined up)- ONE CELL only
-external (multiple cells at once)- human growth hormone (know example)
c. Apoptosis
d. Some cells do not divide at all
What types of cells do not divide at all?
Nerve, brain and red blood cells
What is cancer? Review your notes and the notes over the video animations.
Cancer is a disease of MITOSIS (cell process).BRCA 1&2 and p53 are two types of DNA mutations that can result in cancer.
How do the mutations (in B) result in cancer? Be specific to the cancer type.
BRCA 1 & 2 are tumor suppressors- when they function normally (without a mutation), they will control tumor growth by preventing uncontrolled cell cycles/ mitotic divisions
(an increased risk from 12% to 60% for breast cancer, and an increased risk of 1.4% to 39% for ovarian cancer)
p53 is a proto-oncogene; when it is mutated, it becomes an oncogene; it normally functions to control the cell cycle; if defective, the cell cycle is uncontrolled, which means the cells divide uncontrollably (can cause all cancer types) (plays a role in 50% of all cancers)
What is the difference between a benign growth and a malignant tumor?
a benign growth stays contained within the tissue it originated in
a malignant growth will invade nearby tissues and organs
Explain the process that allows a malignant tumor to spread throughout the body.
After the initial mutation in the genes that control cell growth, the mutations will increase with each new cell division; the cells will then grow with in the tissue and then start to invade the nearby cells and tissues
As the tumor grows, it will recruit nearby blood vessels through the process of angiogenesis
Once new blood vessels have formed, the cancer can now spread throughout the blood stream and deliver cancer cells to new locations
If a cancer cell goes to another site, and starts to grow there (a secondary location), this is known as metastasis
Cancer cells are very different from normal cells: Explain how they are different.
Mutations in the genes that control cell growth
DO NOT respond to the normal controls on cell growth
Changes in the surface of the cell (it becomes sticky); causes the cancer cells to stick together in clumps
Changes in the size of the cytoplasm (usually an increase in the size, or an unusual size)
Changes in the number of nuclei (may have 2-3 nuclei per cell)
Chemo drugs act on different parts of the cell cycle. What parts? Give specific examples of these types of drugs.
DNA synthesis (S-phase of interphase): this prevents the cell from making more DNA, so when it divides, it cannot function; ex. Methotrexate
Spindle formation (mitosis): this prevents the spindle from forming, which prevents the chromosomes from moving and splitting correctly, so all the cells afterwards are defective/ cannot function; ex. Taxol (BC drug) and Vinicristine (childhood leukemia drug)
What are the three MAIN treatments for cancer? Explain how each one works (and the potential side effects).
surgery, radiation and chemo therapy
What is cell differentiation? When does it occur in humans?
When cells become specialized to perform different tasks (contraction, protection)
Usually occurs 5-7 days after egg is fertilized
The gastrula created 3 layers- ectoderm, mesoderm, and endoderm- each layer becomes a certain part of the organisms (each one has many different cell types within it)
How are stem cells different from typical body cells?
unspecialized cells (only have a few active genes)
can become any cell type in the body (with chemical signals)
have the ability to reproduce quickly and indefinitely (some stem cell lines have been around for 20 years)
Stem cells can be used for:
medication testing
treatment of neurological (Alzheimer's and Parkinsons) diseases as well as cardiac disease (replace heart cells that have been damaged or create new valves)
treatment of burn and paralysis victims
create new organs (bladder, intestine, etc.)
What are iPS cells? Why would they be useful?
iPS cells start out as normal cells (that have already differentiated); they are genetically changed (by putting 4 genes in them); they then become stem cells (pluripotent); they then can be given chemical signals to turn into many different cell types
What is a stem cell niche?
a niche is the location that the stem cell can be found in; they will remain there until given the correct chemical signal that tells them to divide and differentiate
ex. hair, bone marrow (red blood cells), intestines
Why is there controversy over the use of stem cells?
some stem cells (the most useful ones) come from the developing embryo (taken from the blastocyst when the embryo is 5-7 days old)
cyclin
group of proteins that regulate the cell cycle
cancer
disorder where cells cannot control their growth
centriole
structure in animal cell that helps organize cell division
spindle
a fan-like structure of microtubules that help to separate the chromosomes
chromatid
one of 2 "sister" identical parts of a duplicated chromosome
centromere
area of attachment between two sister chromatids
cell division
creation of new daughter cells (from 1 cell)
mitosis
division of the nucleus
apoptosis
programmed cell death
stem cells
unspecialized cells
Describe the basic procedure for this lab. What did we do? Why?
Looked at slides (on cards) of cells in various stages of the cell cycle
The cells in mitosis were counted based on the stage of the mitosis; this was to determine if the length of time a cell spends in a stage is related to the amount of cells that will be found in that stage (hypothesis)
What did the results from this lab show us about the cell cycle?
The longer the stage of mitosis, the more likely that the stage will be present in the cells that were counted (ex. prophase is the longest since it has the most things that need to be completed so there were more cells in that stage)