Cytoplasmic Division Mechanisms Cytoplasmic division is not a part of mitosis Differs in plant and...
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Transcript of Cytoplasmic Division Mechanisms Cytoplasmic division is not a part of mitosis Differs in plant and...
Cytoplasmic Division MechanismsCytoplasmic division is not a part of
mitosisDiffers in plant and animal cells
How Do Animal Cells Divide?Cytoplasmic division in animals:
____________Cytokinesis occurs by means of a
____________ ____________, a thin indentation in the plasma membrane halfway between the poles at the equator
The flexible plasma membrane of animal cells can be squeezed in the middle to separate the two daughter cells
How Do Animal Cells Divide?Parallel arrays of microfilaments slide past
one another at the cleavage furrowThis ring of actin microfilaments is called
the ____________ _________This pulls the plasma membrane inward, until
the cytoplasm is partitionedEach daughter cell ends up with:
_____________: Animal Cells
Figure 8.8, pg 132
Figure 8.8a, pg 132
Figure 8.8a, pg 132
Figure 8.8a, pg 132
Figure 8.8a, pg 132
Each daughter cell ends up with:•a nucleus•cytoplasm (with organelles)•a plasma membrane
How Do Plant Cells Divide?The cytoplasm of plant cells cannot just be
pinched in two because of the rigid cell wallA band of microtubules and microfilaments
forms around the nucleus before mitosis starts and marks where the cell plate will form
Vesicles containing remnants of the microtubular spindle form a disk-like structure called a ______ __________between the two new cells
The cell plate becomes a cross-wall that partitions the cytoplasm
How Do Plant Cells Divide?
Figure 8.8b, pg 132
Figure 8.8b, pg 132
Figure 8.8b, pg 132
Figure 8.8b, pg 132
Figure 8.8b, pg 132
Results of Cell Division: a Human Embryo
Precise mechanisms assure that cells will be produced in the right numbers at the
right times and places
Failure to do this can result in genetic disorders and cancer
The Cell CycleThe cell cycle has built-in checkpoints where
proteins can advance, delay, or block forward progress of the cycle
The proteins are the products of checkpoint genes
For example: ______________ regulates ph0sphorylation;
can signal the end of DNA replication________ __________ activate genes that
simulate cells to grow and divide; signal the start of mitosis
When Control is LostWhen checkpoint mechanisms fail, a cell
loses control over its replication cycle
In some cases, mitosis repeats over and over
In others, the cells do not die as they are supposed to
Other times, damaged DNA is replicated
When Control is LostMutant checkpoint genes can cause
_________ by disrupting normal controls as the protein cannot function properly
A tumor is an abnormal mass formed by continually dividing descendents of the cell containing the mutation
Figure 8.11, pg 134
Checkpoint Failure and TumorsProto-oncogenes code for proteins that
stimulate mitosisTumor suppressors inhibit mitosis
_________________ are abnormal masses of cells that have lost control over their growth and cell divisions
___________ ___________ pose no threat to the body
_____________All cancers are abnormally growing
and dividing cells of a ___________ neoplasm
They physically and metabolically disrupt the surrounding tissues
All cancer cells display three characteristics
Characteristics of Cancer1. They grow and divide abnormally
Lack the controls that keep cells from getting overcrowded; cell populations reach extremely high densities
2. Both the cytoskeleton and the plasma membrane of cancer cells become altered
Membrane is leaky and can be missing proteins Cytoskeleton shrinks and/or becomes
disorganized3. Cells have a weakened capacity for adhesion
They can break away to move to other sites in the body
Characteristics of CancerCancerous cells that break off a tumor can
move to other parts of the body and establish a growing colony
Metastasis: the process of abnormal cell migration and tissue invasionAllows cancer to spread through the body
Neoplasms: Benign and Malignant
Figure 8.12, pg 135
Benign Tumor Malignant Tumor
Figure 8.12, pg 135
3 Cancer cells creep ortumble along inside bloodvessels, then leave thebloodstream the same waythey got in. They start newtumors in new tissues.
1 Cancer cellsbreak away fromtheir home tissue.
2 The metastasizingcells become attachedto the wall of a bloodvessel or lymph vessel.They release digestiveenzymes onto it. Thenthey cross the wall atthe breach.
Figure 8.12, pg 135
Chapter 8 HomeworkSelf Quiz 1-10
Explain numbers 1 and 9Critical Thinking #1 and #3