List the 3 reasons why cells can’t get too large
- Diffusion
- DNA
- Surface area-to-volume ratio
Why is diffusion a factor of cell size?
If organelles are too far from the cell membrane, they would have to wait a long time to get molecules that are diffusing through
Why is DNA a factor of cell size?
The nucleus cannot provide DNA fast enough to act as the blue print for the high amounts of proteins and enzymes that a large cell would need
Why is surface area-to-volume ratio a factor of cell size?
The volume of the cell increases a lot faster than the surface area. Therefore if the cell gets too big, the cell membrane will not have enough surface area to diffuse the amount of nutrients the cell needs or get rid of the waste the cell produces
Describe interphase
period where the cell is preparing to divide through growth and maintenance
What is the G1 phase?
(“first gap”) growth
What is the S phase?
(“synthesis”) DNA duplication
What is the G2 phase?
(“second gap”) Maintenance
Describe synthesis
portion of interphase where cells duplicate their DNA
DNA is packaged into sets of what?
chromosomes
Humans have __ chromosomes ( __ from each parent)
46; 23
Body cells are considered _______ _____
Somatic cells
Are somatic cells diploid or haploid?
diploid
Reproductive cells are considered ________
Gametes
Are gametes diploid or haploid?
haploid
What are sister chromatids
identical copies of a chromosome
Describe centromere
holds sister chromatids together
How is DNA duplicated in synthesis?
each chromosome gets copied and is attached to its copy
Define mitosis
Cell division where 1 diploid parent cell makes 2 identical diploid daughter cells
Describe prophase
the chromosomes coil up and become visible while the nuclear envelope disappears. Sister chromatids are present
A _______ forms at each pole and ________ ______ made of microtubules grow out
centriole; spindle fibers
Short microtubules stick out from the centriole in a star shape known as an ____
aster
Describe prometaphase
spindle fibers attach to each of the chromatids at a sight called the kinetochore
Describe metaphase
the spindle fibers line the chromatids up at the equator of the cell called the metaphase plate
Describe anaphase
the kinetochores “reel in the spindle fibers to pull the sister chromatids apart by splitting their centromere. The split chromatids are pulled towards opposite poles of the cell
Describe telophase
Once the chromatids have reached the opposite sides the spindle fibers disappear, the chromosomes unravel, and the nuclear envelope reappears on the two new nuclei.
Describe cytokinesis
the cytoplasm forms a cleavage furrow at the equator to split the cytoplasm
Describe binary fission
the chromosome replicates (beginning at the origin of replication), and the two daughter chromosomes actively move apart
The cell cycle is controlled by chemical signals in the __________
cytoplasm
What is the cell cycle control system
a set of events that occurs in a sequence to regulate the cell cycle
The cell cycle control system has specific _________ where the cell cycle stops until a go-ahead signal is received
checkpoints
the __ checkpoint is the most important
G1
If the cell does not receive the go-ahead signal what happens?
it will go into a non-dividing state called the G0 phase
What is cyclin
a regulatory protein that builds up in the G2 phase
What are Cyclin dependent kinases (Cdks)
a regulatory protein that is always present waiting for the arrival of cyclin
What is MPF (maturation-promoting factor)
cyclin and Cdks combined to trigger a passage through G2 and Mitosis
What are growth factors
proteins released by certain cells that stimulate other cells to divide
What does the platelet-derived growth factor (PDGF) do
stimulates the division of human fibroblast cells (connective tissue). This is released when cut from blood platelets so healing can begin.
What is density-dependent inhibition
crowded cells stop dividing
What is anchorage dependence
cells must be attached to something in order to divide
Why are cancer cells formed
Cancer cells do not respond normally to the cells cycle check points or external signals
How do cancer cells’ growth factor work?
They may make their own growth factor
They may convey a growth factor’s signal without the presence of the growth factor
They may have an abnormal cell cycle control system
Define transformation
A normal cell is converted to a cancerous cell
What is a benign tumor
The lump that is formed if the cancer stays at the original site
________ tumors spread to surrounding tissues through _______ through _______ ________
Malignant; metastasis; blood vessels
Describe the organization eukaryotic genome
Eukaryotic genomes are packaged into chromosomes, it is a double helix
Compare and contrast cytokinesis in animals and plants
Animal cells undergo true cytokinesis- plants do not. In plants a cell plate forms to become the new cell wall separating the two daughter cells. Animal cells form a cleavage furrow. This occurs during telophase of mitosis and ends when the two daughter cells resolve.
Describe the S phase checkpoint
ensure DNA is fully replicated before mitosis
What do the G1 and G2 checkpoints check?
if DNA is damaged before moving to the next step
What is the checkpoint in mitosis for?
to ensure chromosomes are lined up correctly in metaphase before continuing to anaphase
