Cell Cycle Notes - Anna High Science Den - Home



Cell Cycle Notes Name: ______________________

Cells divide. This makes cells small.

Why do cells divide? Why must cells be small?

PURPOSES OF CELL DIVISION

1. ____________- increase in size of the organism (by dividing cells, not by increasing the size of the cells)

2. ___________– needed because of worn out or injured cells (your skin cells are replaced every 28 days; your stomach every 7)

3. ____________________(2 types)

•____________– one parent. Offspring identical to parent - mitosis

•__________– combination of genetic material from two parents - meiosis

Why must cells be small? “Bigger is Not Better”

CELLS ARE SMALL

Surface area to volume ratio must remain _______ for the cell. Cells need to stay small so that they can effectively transport materials:

•To take in sufficient nutrients and oxygen to maintain life

•To remove waste

•To move molecules across the cell efficiently

This is the reason why cells do not grow bigger even if the organism they are part of does

High Surface Area to Volume Ratio?????

Surface area = 6 sides x height x width

= 6 x 1 x 1 = 6

Volume = L x W x H = 1

Ratio SA:V = 6:1 -----> = 6

Surface area = 6 x height x width

= 6 x 4 x 4 = 96

Volume = L x W x H = 64

Ratio SA:V = 96:64 = 3.2 --------> = 1.5

6 is higher than 1.5!

Reproduction:

___________________________ – passes on chromosomes through __________ to make a clone (like binary fission in bacteria…more later…)

__________________________ – chromosomes are separated in _________ (more later…) and then combine to make a new organism (like egg & sperm fusing to make a newly formed zygote…more later…)

Vocabulary:

•_________________ – structure found in the nucleus of ________________ cells

that contains the genetic material; made of _______________

•________________– Strands of ________ found in the nucleus; makes up

chromosomes when folded and thickened around _____________

Nuclesome – “DNA packing”

- Strand of DNA called chromatin is tightly coiled and folded around a protein

called _______________

- DNA and histone form a bead-like structure called a _________________ which are then packed with one another to form a thick __________________ which is then visible only under a light microscope

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Prokaryotic Cell Division:

Prokaryotes reproduce by __________________________ - the dividing in half after the DNA is replicated

The Cell Cycle:

The cell cycle is a continuous process that occurs in ___________________ (body cells ex. skin). It is an ordered set of events of cell growth and division resulting in two daughter cells, which then start the process again.

2. main parts:

l. ____________________________ - the “getting ready stage”

• ________________ (makes up 90% of the cell’s life) – here the DNA appears as thread-like chromatin

– G1

– S

– G2

II. _________________

• ___________ – division of the nucleus

• ___________________– division of the cytoplasm;

follows mitosis

STAGES OF CELL CYCLE

I. ________________________________ (Must occur before mitosis)

____________________ - getting ready stage (happens before mitosis, can often see the

nucleolus, DNA threadlike chromatin)

•_______of the time, the cell is in this phase

•_______

•Performs the job that is unique to that type of cell

(a)___________________________ – G1

–Decides whether or not the cell will divide

–Makes its structural proteins and enzymes to perform its functions

•A pancreas cell will produce and secrete insulin

•Salivary gland will produce and secrete enzymes in the mouth to aid in digestion

(b)______________________ (DNA Replication)

–Each of the chromosomes is copied

(c)_____________________________– G2

–DNA replication is checked by DNA repair enzymes

–Cell prepares for mitosis

–Proteins organize themselves to form a series of fibers called the ______________

•Involved in chromosome movement during mitosis

•Spindle fibers composed of microtubules

II. Cell Division - MITOSIS

-Continuous process

-4 main parts

–prophase, metaphase, anaphase, telophase

–P-MAT (pray more at the …..church)

______________________

–Condensing (thickening/fattening) of 2

________________ to form chromosome hinged by

a ______________

•Coil up

•Become visible

–Centrioles begin to _________ to opposite sides

of the cell

–Nuclear envelope begins to _______________

______________________

–Spindle fibers align the chromosomes along the

____________of the cell nucleus.

•This line is referred to as the metaphase

plate.

–This organization helps to ensure that in the next

phase, when the chromosomes are separated,

each new nucleus will receive one copy of each

chromosome

___________________

- centromere that joins the sister chromatids __________. This allows the sister chromatids to ______________ and move apart from one another as individual chromosomes

–Each chromosome is attached to a spindle which moves it toward one pole

–Results in ______________________ and __________________

–Chromosomes arrive at opposite ends of cell and lose their distinct shape

–New nuclear envelope membranes begins to reform around each cluster of chromosomes of the daughter nuclei.

-Nucleolus becomes ____________ again

–The chromosomes disperse (uncoil) and are no longer visible under the light microscope.

–The spindle fibers break apart

–Cytokinesis may also begin during this stage.

–This phase just reverses many of the processes of prophase

CYTOKINESIS

•Process in which the cytoplasm divides and two separate cells form.

•In animal cells, it begins with the formation of a ________________________

•Microfilaments contract during cleavage and assist the division of the cell into two daughter cells

–“ It is like a string being pulled around a cube of Jell-O”

•In plant cells, cleavage does not occur

•New cell wall is formed in the center of the cell by ____________ from the _____________________

•As the vesicles join, they form a double membrane called the _________________

–Forms in middle and moves outward

–Separates the daughter cells

MITOSIS—Summary

PROPHASE- P for Phat (fat), chromosomes condense/fatten and become visible

METAPHASE- M for middle as the chromosomes lined up in the middle of cell

ANAPHASE- A for Apart or Away because the chromatids pull apart and move away from center

TELOPHASE- T for Two new nuclear envelopes forming around the clusters of chromosomes

•

Not all cells reproduce…

• Some leave the cell cycle here and do not undergo cell division

– Red Blood Cells – which “kick out” their nucleus to make room for the hemoglobin and therefore can’t divide

– Brain and spinal cord cells – rarely if ever divide

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Cell Cycle Regulators

Scientific Evidence: In the early 1980’s a group of scientists

Discovered that cells in mitosis contained a group of

___________________ that when injected into a non-dividing cell,

would stimulate the cell to begin dividing

These scientists also discovered that the amounts of these

proteins in the cell would increase and decrease with the cell

cycle. These proteins were called _______________ as they

seemed to ______________ the ___________ and _________________ of eukaryotic cells through the entire cell cycle.

Protein regulators will give either the “green light” to start cell division, the “yellow light” to delay or the “red light” to stop cell division.

There are Two Types of Cell Cycle Regulators:

1. _________________________ (the “checkpoints”)

These are cyclin proteins that respond to events occurring

__________ the cell

They will only let the cell cycle proceed if certain processes

have been completed inside the cell

• Regulatory protein will not let the cell enter mitosis

until all DNA has been ___________________

• Regulatory proteins will prevent the cell from entering

anaphase until all the chromosomes are _______________ to the spindle fiber (mitotic spindle)

• Other regulatory proteins trigger the __________ from mitosis and the beginning of the G1 phase of interphase

2. __________________________

These are proteins (_______________________) that respond to events outside the cell

They will direct the cell to __________ up or ________ down the cell cycle

• Proteins found on the _______________ of neighboring cells will cause cells to slow down their growth or stop the cell cycle to _______________ excessive growth

• Are important in wound healing, bone healing and growth of newly formed embryo

Cancer Terms

1. _________________________ - a cluster of cells that stays at the original site; normally not serious and can be successfully removed surgically

2. _________________________ - invasive tumors that impair the function of the tissue or organ it is within.

3. _________________________ - cancer cells that break away from the tumor and travel to form tumors in other locations, usually serious

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Websites

•Cell Mitosis Lab Practice

•Mitosis pictures & Video



•Cell Cycle Interactive Game



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The size of the nucleus with the DNA is not increasing but the cell size is increasing. DNA has a difficult time meeting the needs of the larger cell.

• _____________ - one of the two strands of a chromosome that become visible

during mitosis or meiosis

• _____________ - the region of the chromosome that holds the two sister

chromatids together

• _____________ – division of the nucleus. It is an asexual process since cells produced by mitosis are genetically identical to the parent cell

• ___________________ - division of the cytoplasm

6 Stages of Mitosis

P

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Ot Other cells can’t stop dividing……

U Uncontrolled cell growth is known as ____________. Cancer is a ____________ of the __________________.

Regulating Cell Cycle

• __________________________________: GI, G2 and M phases

• G1 seems to be the most important checkpoint. Cells will either continue through it and complete the cycle or be changed into a _________ phase which is a non-dividing phase

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C Cancer

• _________________________: are genes that cause cells to divide, leading to cancer.

• _________________________: genes that stop mitosis

• Usually people that end up with cancer have both an oncogene and a problem in the repressors.

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