Cell Growth and Division

Things to ponder… When living things grow, what happens to its cells? ? OR ?

Things to ponder… When living things grow, what happens to its cells? For example: When a 7lb baby grows into a 70lb child is it because its cells grow bigger or because it made more cells?

Things to ponder… When living things grow, what happens to its cells? For example: When a 7lb baby grows into a 70lb child is it because its cells grow bigger or because it made more cells? What would happen if a cell where just split into two without any preparation? Would the two new cells have everything they would need to survive? ?

Objectives Describe the stages of the cell cycle, including DNA replication and mitosis, and the importance of the cell cycle to the growth of organisms (TEKS 5A) Describe how cell division solves the problems of cell growth. Name the main events and components of the cell cycle Describe what happens during the 4 phases of mitosis

Limits to Cell Growth The larger a cell becomes, the more demands the cell places on its DNA. In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane. If cells just grew larger… DNA would get “overloaded” As a cell increases in size, it usually doesn’t make more DNA. The same amount of DNA would then be forced to control a much larger cell causing an “information crisis”

Limits to Cell Growth The larger a cell becomes, the more demands the cell places on its DNA. In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane. If cells just grew larger… Exchanging materials would also become more difficult Food, oxygen, and water enter a cell through the cell membrane and wastes exit through this same membrane The cells surface area and volume are critical to the cells ability to efficiently do this. As a cell grows, its volume increases more rapidly than its surface area limiting what can come into or out of the cell. It’s like a highway in Houston vs a highway in Huntsville.

Made more cells…Cell Division! When a 7lb baby grows into a 70lb child is it because its cells grow bigger or because it made more cells?

Cell division, however, is just one small part of the cell cycle

Objectives Describe the stages of the cell cycle, including DNA replication and mitosis, and the importance of the cell cycle to the growth of organisms (TEKS 5A) Describe how cell division solves the problems of cell growth. Name the main events and components of the cell cycle Describe what happens during the 4 phases of mitosis

The Cell Cycle During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cycle again. Interphase-The longest part of the cell cycle. It has 3 phases. G1 phase- a growth phase. Cells increase in size and synthesize new proteins and organelles. S phase- Chromosomes (DNA) are replicated G2 phase- another growth phase. Organelles are duplicated and the cell prepares for cell division Cell Division– Also called M phase. Has 2 phases. Mitosis- First stage of cell division. It’s made up of 4 stages Cytokinesis- Final stage of division when the cytoplasm divides and separates to form two daughter cells.

? Answer: NO Things to ponder… When living things grow, what happens to its cells? For example: When a 7lb baby grows into a 70lb child is it because its cells grow bigger or because it made more cells? What would happen if a cell where just split into two without any preparation? Would the two new cells have everything they would need to survive? Answer: NO ?

Cell Division: Background Info The who, what, where, when, why, and how of cell division Who’s dividing: Where does it start: When does it divide: Why does it divide: How does this happen: The cell, specifically somatic or asexual cells The nucleus During mitosis (M phase) To make more cells (to grow) I’m glad you asked…

Cell Division: How it happens Every cell must copy its genetic information before cell division can begin. In prokaryotes (aka bacteria) cells undergo a much simpler version of cell division called binary fission…but we won’t focus on this today. In eukaryotes, cell division is more complex mainly due to the complexity of cell itself (more organelles, more DNA, etc) The two main stages of cell division are mitosis and cytokinesis Do you remember at what stage of the cell cycle is genetic information copied?

Cell Division: What’s a chromosome? Every cell must copy its genetic information before cell division can begin. Chromosomes contain that genetic information. Chromosomes are simply DNA wound up into a threadlike structure found in the nucleus. Chromosomes are not visible in most cells except during cell division. During S phase, each chromosome is duplicated or copied creating an identical sister chromatid. At the end of cell division, the two new daughter cells will each have one of those sister chromatids; thereby making two cells with identical chromosomes.

Humans have 46 chromosomes, or 23 pairs. One chromosome is paternal (means it comes from the father) One chromosome is maternal (means it comes from the mother) The figure below is called a karyotype. It’s a set of human chromosomes arranged in order from 1-22 with the sex chromosomes being last.

Objectives Describe the stages of the cell cycle, including DNA replication and mitosis, and the importance of the cell cycle to the growth of organisms (TEKS 5A) Describe how cell division solves the problems of cell growth. Name the main events and components of the cell cycle Describe what happens during the 4 phases of mitosis

Cell Division: Mitosis There are 4 main stages of mitosis

PROPHASE DNA thickens and becomes visible 1st dividing phase DNA thickens and becomes visible Centrioles appear in centrosome region & move to poles Nuclear membrane & nucleolus disappear Spindle fibers form & attach to chromosomes

________ region organizes spindle CENTROSOME Spindle MICROTUBULES are part of cytoskeleton

METAPHASE Chromosomes line up in ___________ middle

ANAPHASE apart Centromeres split Centrioles pull chromatids_______ Each chromatid is now its own chromosome

TELOPHASE two See ______ nuclei Nuclear membrane & nucleolus return Chromosomes spread out at opposite ends of the cell Spindle fibers disappear Images from: Pearson Eduction Ince; Publishing as Pearson Prentice Hall http://www2.bc.cc.ca.us/cnewton/Biology%2011/Mitosis.html

Final stage of cell division is: CYTOKINESIS Cytoplasm splits into 2 cells