Cell structures

What you need to be able to do…

• Explain why cells divide• Identify cell structures • Explain the role or ‘job’ that

each structure has.

There are three main functions of cell division:

growth, repair, and reproduction.

Growth

• living things (organisms) are made up of one or more cells. • organisms begin as a single cell. • Multicellular organisms, like us,

use division to get larger.

Repair

• Old cells constantly die and must be replaced. • For example every minute of the day

we lose about 30,000 to 40,000 dead skin cells, which are replaced by new skin cells.

Reproduction

• Single celled organisms (sometimes called ‘unicellular’) reproduce through cell division.

• Bacteria is an example of a unicellular organism.

• Some multicellular organisms, such as a mushroom, also reproduce by cell division.

The Nucleus

• directs all cell activities, including cell division

• surrounded by the nuclear membrane which allows some materials to pass into and out of the nucleus.

• The nucleus contains the nucleolus and chromosomes

chromosomes

• Chromosomes are made of DNA (deoxyribonucleic acid) and protein

• DNA is a very long molecule that looks like a twisted ladder.

• DNA provides the directions for all the cell structures and activities, including repairing worn and damaged cells and replacing dead cells.

Nucleolus

• The nucleolus is inside the nucleus• It is the site for the production and

assembly of ribosomes. • The ribosomes then move out of the

nucleus

Ribosomes

• Ribosomes are tiny organelles that make proteins • Ribosomes are either free in the

cytoplasm or attached to endoplasmic reticulum.

Endoplasmic Reticulum

• The ER is a series of tubes and flattened sacs that transport materials throughout the cell.

• If ribosomes are attached it is called rough ER. Rough ER transports proteins throughout the cell.

• If no ribosomes are attached it is called smooth ER. Smooth ER manufactures and transports fats in the cell.

Cytoplasm

• Contains all the organelles in the cell. • Most of the cell’s activities occur in

the cytoplasm, and nutrients are absorbed, transported, and processed here.

Microtubules

• Contained in the cytoplasm• Provide transport of the organelles

and structurally reinforce the cell.

Centrioles

• Organelles made of special microtubules. • found in almost all animal cells, and

they are active during cell division.

Plenary…

1. Why do cells divide?

2. What is inside the nucleus?

3. What does the nucleolus do?

4. What are chromosomes made of?

5. What do Ribosomes make?

6. What is the difference between the Rough ER and the Smooth ER

Work zone assignment (Due Monday October 25th )

• Using the information provided, make a poster or a 3-D model of a ‘make-believe’ cell containing all the structures we learned about.

• You may make the cell look like whatever you want (a house, for example).

• Label each structure and explain what it does (in your own words!)