ch 11 : cell division

ch11 quiz study sheet (copy of google doc)

biology honors ‘24-‘25

cell division

there are 2 main reasons a cell should divide instead of growing;

• the larger a cell is, the less efficient it is in moving waste and food across the cell

  • the rate of material exchange (waste out, food in) depends on the surface area of the cell. (aka the total area of the cell membrane)

  • the rate at which food and oxygen are consumed and wastes are produced depends on the volume of the cell.

  • as a cell gets larger, both of these rates increase, as does its SA, but vol and SA don’t grow at the same rate.

• as a cell grows it places increasing demands on its DNA

  • the largest cells use unusual shapes/structures to maintain the ratio.

difference between asexual and sexual reproduction - 

• asexual reproduction involves a single parent and produces offspring that are genetically identical to the parent. 

• sexual reproduction requires two parents and results in offspring with genetic material from both, leading to genetic diversity. 

asexual

sexual

chromosomes are structures within cells that contain dna, the genetic material. each chromosome consists of a single, continuous dna molecule. 

after dna replication, each chromosome comprises two identical copies called sister chromatids, connected at a region known as the centromere. 

these sister chromatids are considered a duplicated chromosome.

 prior to replication, a chromosome is referred to as a single chromosome. 

homologous chromosomes are pairs of similar but non-identical chromosomes, one inherited from each parent. 

during cell division, chromosomes undergo condensation, a process where chromatin fibers become tightly coiled, forming the compact structures visible under a microscope. this supercoiling is essential for the efficient segregation of chromosomes into daughter cells.

prokaryotic cells divide through a process called binary fission, where the single, circular chromosome replicates, and the cell splits into two identical daughter cells. eukaryotic cells, on the other hand, undergo mitosis, a more complex process involving multiple stages to ensure accurate distribution of duplicated chromosomes into two new nuclei.

binary fission vs. mitosis

binary fission is a simpler process where the cell duplicates its single circular chromosome and then splits into two identical daughter cells. mitosis, on the other hand, is a multi-step process that ensures accurate chromosome segregation into two genetically identical daughter cells.

cell cycle overview

the cell cycle consists of two main phases: interphase (when the cell grows and prepares for division) and mitotic phase (m phase) (when the cell actually divides).

interphase (prepares the cell for division)

1. g1 phase (gap 1):

• the cell grows in size.

• organelles duplicate.

• the cell performs its normal functions.

2. s phase (synthesis phase):

• dna replication occurs, producing sister chromatids.

3. g2 phase (gap 2):

• final preparations for division.

• checks for dna replication errors.

mitosis (m phase) – the actual division process

1. prophase:

• chromatin condenses into visible chromosomes.

• spindle fibers begin to form.

• nuclear membrane starts breaking down.

2. metaphase:

• chromosomes line up at the metaphase plate (center of the cell).

• spindle fibers attach to the centromeres.

3. anaphase:

• sister chromatids are pulled apart by spindle fibers towards opposite poles.

4. telophase:

• nuclear membranes reform around the separated chromosomes.

• chromosomes start decondensing into chromatin.

cytokinesis (division of the cytoplasm)

• in animal cells, a cleavage furrow forms, and the cell pinches into two.

• in plant cells, a cell plate forms due to the rigid cell wall, eventually becoming the new cell wall.

cell division: plant cells vs. animal cells

the complete cell division process

1. the cell grows and prepares during interphase.

2. mitosis ensures that chromosomes are equally divided.

3. cytokinesis splits the cell into two identical daughter cells.

4. each daughter cell enters the g1 phase and begins the cycle again.

the cell cycle is regulated by checkpoints that ensure proper division. the three primary checkpoints are:

1. g1/s checkpoint: assesses cell size, nutrients, growth factors, and dna integrity. if conditions are unfavorable or dna is damaged, the cell may enter a resting state (g0) or undergo repair mechanisms.

2. g2/m checkpoint: ensures that dna replication in the s phase has been completed successfully and checks for dna damage. if errors or damage are detected, the cell cycle is halted to allow for repair.

3. spindle (metaphase) checkpoint: occurs during mitosis; it verifies that all chromosomes are properly attached to the spindle apparatus before proceeding with chromosome separation.

these checkpoints are crucial for maintaining genomic stability and preventing uncontrolled cell division.

regulatory proteins, such as cyclins and cyclin-dependent kinases (cdks), play vital roles in cell cycle progression. cyclins regulate cdks, which in turn phosphorylate target proteins to advance the cell cycle. growth factors are external signals that promote cell division and survival. apoptosis, or programmed cell death, is a mechanism that eliminates damaged or unnecessary cells.

tumors result from unregulated cell growth. benign tumors are non-cancerous growths that remain localized, while malignant tumors are cancerous, can invade surrounding tissues, and have the potential to metastasize to distant body parts.

cell division; cell cycle; mitosis; regulation

why does cell division occur (multiple reasons)? what is the difference between sexual and asexual reproduction? What are the advantages and disadvantages of each?

chromosome terminology - double/duplicated chromosome vs. single chromosome, chromatids, centromere, homologous chromosomes, supercoiling/condensed

binary fission vs. mitosis. cell cycle/interphase/mitosis stages and events.

plants vs. animals.

regulation/control of cell cycle - checkpoints (what are the 3 different checkpoints - what do they check for and why are they important?); regulatory proteins, growth factors, cyclins, apoptosis, tumors, cancer (benign, malignant)