Download Cell Growth

Cell Growth
Discussion Questions
1. What is cell growth? (**getting bigger, gaining mass)
2. What's the difference btwn growth and division?(**getting bigger, reproduction)
3. Are our cells the same size as an infants? (**yes)
Then, why is a baby smaller?(**they have less cells)
4. How do we grow? (**cells increase in size and number)
I. Cell Growth
A. Cell size limitations-- Cells stay small because...
1. surface area to volume ratio
a. large ratio is needed to get nutrients in and wastes out efficiently
b. more SA to small volume does this quicker; more surface to work with
organelle level
c. (**cristae) (folded membrane of mitochondria) increases SA for E production
organ level
d. (**rugae) (folds in stomach) help to increase SA to maximize secretion
Volume
Surface area
SA to Volume Ratio
1cm cube
1cm3
6cm2
6:1
2 cm cube
8cm3
24cm2
3:1
4 cm cube
64cm3
96cm2
3:2
**How many small cubes will it take to = the volume of one 2cm cube? *8
**How much greater is the total surface area of that # of cubes vs one 2cm cube?
*24cm2
eight 1cm cubes have SA of 48cm2, one 2cm cube has SA of 24cm2 ...
2. (**Diffusion)
a. movement of nutrients and wastes through cytoplasm
b. RNA traveling through cytoplasm
c. must be quick or cell will die, diffusion is slow over long distance
*FOCUS ? Why can't we be one big cell? (**nutrients and waste couldn’t diffuse quickly)
3. (**DNA) tells it to stay small (tells it when to divide)
a. one nucleus where DNA regulates RNA production & protein synthesis
b. large amoeba have more than 1 nucleus (nuclei) because it’s (**more efficient)
B. Cell Facts
1.
2.
3.
4.
5.
6.
cells are approximately (**2-200) micrometers
the largest cell is (**the yolk of an ostrich egg, 8cm in diameter)
there are approximately (**100 trillion) cells in the average adult
every second your body produces approximately (**25 million) new cells
in your lifetime, you will shed approximately (**40) pounds of skin.
(**95%) of dust is composed of skin cells.
Discussion Questions before division.
1. Why do cells divide? (**repair and reproduction)
2. What makes a cell divide? (**DNA)
3. Are they identical? (**Yes, to do the same function)
4. When we reach full size, do our cells still divide? (**yes, to repair injuries, etc.)
5. If our cells are always dividing, why don't we have more? (**some die or are damaged)
II. Cell Division in prokaryotes (bacteria) and Growth in other organisms
***Find and insert a small picture or example for each of the following
A. Binary Fission
1. (** bacteria and some protists divide by binary fission
after genetic material, DNA is replicated)
2. (** cell pinches inward, splitting cell in two)
3. (** bacteria are the only organisms to reproduce this way)
B. Budding
1. (**tiny growth off of the side of a parent that eventually grows to full size)
2. (**yeast, hydra)
C. Sporulation
1. (**use of spores to reproduce)
2. (**fungi- mold, mildew, mushrooms)
3. (**plants- ferns and mosses have sporophyte/gametophyte generations)
D. Vegetative Propagation- is growth, NOT reproduction of an organism
1. (**the growth of roots from stems or clippings submerged in water)
2. (**some plants)
E. Regeneration- is growth for repair, NOT reproduction of an organism
1. (**regrowth of an injured or severed body part)
2. (**starfish, lizard tails)
F. Mitosis- can be a means to ‘grow’ or a form of asexual reproduction
1. (**is how multicelluar organisms grow or gain body mass)
2. (**is how some unicellular protists {algae, amoeba} reproduce)
control + click the link below to see 3-D chromosomes in each stage of mitosis
http://mcb.berkeley.edu/labs/cande/mitosis.html
III. Division in eukaryotes
A. Cell Cycle consists of interphase and mitosis. (G1, S, and G2= interphase)
1. G1 is the first growth phase, cell gains cytoplasm (grows & develops) {11hours}
2. during the S phase, DNA is replicated and histones are synthesized {7 hours}
3. G2 cell prepares for division, sythesizes organelles & materials for division {3 hours}
4. Mitosis is the division of the nucleus and its contents to 2 daughter cells {1 hour}
5. Cytokinesis-(**the division of the cytoplasm that occurs at the end of mitosis)
B. Forms of DNA and eukaryotic chromosomes (xsomes)
1. the chemical structure of DNA is always the same, changes are only physical
2. (**chromatin)- thin uncoiled strands of DNA in the nucleus (spaghetti in a TIN can)
3. (**chromosome) (xsome)- one long piece of double stranded DNA coiled into a rod
a. is DNA coiled around histone proteins
b. is a visible rod shaped structure
c. each xsome consists of 2 identical parts called sister chromatid
d. the point at w/c each pair of chromatids is attached is the centromere
e. if it has ITS OWN centromere, it’s a chromosome
sister
chromatid
C. Growth and Division (interphase, mitosis, and cytokinesis) IPMAT!!!
1. INTERPHASE- between phase (between what?**cell divisions)
a. (**period of growth that consists of G1, S, and G2)
b. DNA is replicated and chromosomes are ALWAYS in the form of chromatin
c. nuclear membrane and nucleolus present
d. (**most of the cell cycle is spent here)
2. PROPHASE- primary phase
a. (**first and longest phase of mitosis)
b. (**nuclear membrane and nucleolus disappear)
c. replicated DNA, in the form of chromatin, coils to form visible xsomes
d. xsomes are doubled structures, each half is a sister chromatid
e. fibers organize to form spindle fibers (animals-centrioles move to poles)
3. METAPHASE- middle phase
a. (**xsomes line up on spindle fibers in the middle [the equator] of the cell)
b. (**each xsome is attached to spindle by its centromere)
4. ANAPHASE- apart
a. centromere splits and spindle fibers shorten separating sister chromatid
b. after separation, each chromatid is now called a chromosome
c. (**xsomes move to opposite poles, away from their copies)
5. TELOPHASE- two
a. nuclear membrane and nucleolus reappear, xsomes become chromatin
b. (**spindle starts to disappear)
c. (**2 daughter cells are formed)
6. CYTOKINESIS- division of cytoplasm that starts during telophase!!!!!!
a. plants-(**cell plate) forms across the middle of the cell and extends outward
b. animals-(**cleavage furrow) pinches inward, between the two new nuclei
NOW EACH DAUGHTER CELL HAS THE SAME NUMBER AND TYPE OF XSOMES AS THE ORIGINAL
CELL. BACK TO INTERPHASE!!!!!!
IV. Regulation of the cell cycle
A. Cell division is controlled by DNA
1. cells go or stay in G1, S, and G2 because of the presence or accumulation of "trigger proteins"
2. this control keeps organisms and their cells in homeostasis
3. regulation of the cell cycle is ESSENTIAL
B. Uncontrolled division of cells
1. cancer is (**the uncontrolled ‘growth’ or division of cells)
2. cancer cells have simply lost genetic control over cell division
3. when (**oncogenes) are triggered and expressed, they make the cell cancerous
4. (**carcinogen) - any substance or agent that causes cancer
(asbestos, smoking, pollution, chemicals, UV light, X-rays)
5. types of tumors
a. (**benign) - usually stay within the mass, generally no life threat (wart, cyst)
b. (**malignant) - cancerous, can be life threatening
i. (**lymphoma) - solid tumors that grow in tissue that makes blood cells
(these may cause leukemia)
ii. (**carcinoma) - grow in the skin and nerves
iii. (**sarcoma) - grow in bone and muscle
6. spreading of cancer cells can be slowed or stopped if it’s detected early
a. (**invasiveness) movement of cancer cells into surrounding normal tissue
b. (**metastasis) - cancer cells leave the tumor and settle in other places