The Life of a Cell

Cells have a lifecycle

Cells live and function.

Cells need to reproduce– To replace old cells– To replace injured cells– In order for living things to increase in size– In order for living things to develop

Cells die

Some cells live longer than others

– Red blood cells live approximately 10 days– Stomach and cheek cells live less than a day– Most nerve and brain cells live your entire life

Therefore, cells must be able to reproduce

The Life of a Cell

G1, S, G2 are known as Interphase

M stands for Mitosis

Interphase

3 phases in Interphase

• G1 phase– Cell grows larger– Performing cell functions (doing its job)

• S phase– DNA Replication

• G2 phase– Performing cell functions (doing its job)

The importance of replication

Replication

MITOSIS

Each new cell needs the same information as the original cell or it won’t function properly

So what do chromosomes look like after replication?

Single chromosomes

BEFORE AFTER

Chromosome and its copy

Closer Look

• The two replicas are connected at a center called the centromere

(centro………center)• Each replica is

referred to as a sister chromatid

Steps of Mitosis

Steps of Mitosis• Prophase

• Metaphase

• Anaphase

• Telophase

Prophase

• Chromatin (a mass of DNA and histones) wraps into chromosomes

(you now begin to see chromosomes- they will look like thick fingers)

You can’t see chromosomes here

Just 2 nucleoli

Now you can see dark fingers

These are chromosomes

Prophase

• Nuclear membrane starts to disappear

• Centrioles start to move to opposite sides of cell

centrioles

MetaphaseWhen you think Meta think Middle!

• Chromosomes line up in center of cell

• Spindle fibers connect to each chromosome

• Spindle fibers come from the centrioles (think of them like strings)

Spindle fibers

Anaphase

• Spindle fibers shorten and pull the chromosomes

• Chromosome break in half and move to opposite sides of cells

• Notice: no more sister chromatids, each one is now a chromosome

Telophase

• Nuclear membrane returns

• Cytokinesis occurs (cytoplasm and organelles are divided)

Interphase and Mitosis in Plant Cells

NAME THE PHASES

How will we remember this?

Let’s do the hand

So here is the complete cell cycle

Grab your microscope and let’s see if you can find the phases

• At the lab, go to this powerpoint.

• You may work in groups of 2, but make sure each person sees!!!!

• The rest of the power point will walk you through how to find the correct cells

• You must draw each phase as you see it and obtain a signature from me for points.

• Oh joy, what fun we’ll have

Root Tip Under the Microscope

3 Labeled Areas

Elongation zone:

What phase do you think these cells are in? Why?

Interphase, they are growing larger and functioning Root Cap: These cells

are old and will be damaged and dead. They are the ones that are pushed through the dirt as the root grows.

(similar to dead skin)

Where to look for this lab

Find the root on scanning power first.

Find the root cap.

Move to the zone of mitosis.

Go to low power, make sure you are still in the middle of the zone of mitosis

FOCUS!!

Move to high power

InterphaseLook for the nucleus and nucleolus!!

Prophase

You should be looking for the dark fingers (chromosomes)

MetaphaseMeta…Middle

Chromosomes should be in a line down the middle of the cell

AnaphaseCentromeres have broken and fibers are pulling the chromosomes to opposite sides of the cell

Telophase/CytokenesisStarting to look like there is a nucleus again. Look for a

new cell wall forming between the two new cells.

There’s that new cell wall

Mitosis in Animal Cells

• Follow this link to see an animation and a real animal cell undergoing mitosis

• Can you tell when the real cell hits the various stages or do they seem to blend into each other?

• Mitosis: An Interactive Animation

Still Frames of Mitosis in Animal Cells

• Look at the phases in animal cells and note any differences on your paper

• Animal cell Mitosis phases

Have a nice day!