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