Cell Growth and Division

When we grow up, what’s really happening to our cells?

Cell Growth and Division

Do we grow by getting more cells?

Or do the cells we already have get bigger?

Cell Growth

• Cells can only grow to a certain size before they have to divide.

• An adult and a baby have the same size of cells. Adults just have more cells.

• Your body makes about 24,000,000,000 new cells each day.

Life is made of cells video

Why can’t cells just get bigger?

There are two reasons that cells have to divide as they grow.

1- DNA overload2- Exchanging materials

DNA Overload• The bigger cells

get, the harder it is for DNA to be used by the entire cell.

• Like a small town library as the town grows bigger.

Exchanging materials• The cell membrane

has to transfer items in and out of the cell.

• As the cell grows, the volume increases faster than the surface area does.

• Like the roads leading into or out of a town.

The cell cycle

• The cell cycle (life cycle of a cell) has 4 main parts:– G1 phase– S phase– G2 phase– M phase

The cell cycle

• Anytime the cell is not dividing, it is in Interphase– During interphase the

cell grows, copies its DNA, and gets ready to divide.

• M phase is when the cell divides

Cell Division• During cell division

the cell actually divides into two identical cells.

Mitosis• Mitosis has 4 parts:1- Prophase2- Metaphase3- Anaphase4- Telophase

1- Prophase

• During Prophase:– Chromosomes

condense and become visible.

1- Prophase– Centrioles

move to the poles of the cell.

1- Prophase

– The nuclear envelope breaks down.

2- Metaphase

• During Metaphase, the chromosomes line up across the center of the cell.

3- Anaphase

• During anaphase, the chromosomes split apart and move to opposite sides of the cell.

• Anaphase continues until the chromosomes stop moving.

4- Telophase

• Chromosomes begin to disperse into a tangle of chromatin.

• The nuclear envelope reforms around the two sets of chromatin.

Mitosis

• Mitosis is now complete!

• Remember:Mitosis:1- Prophase2- Metaphase3- Anaphase4- Telophase

Quiz time!!!

Which part of mitosis does each of the following pictures represent?