• What are some of the tools scientists use to observe very small things?

• Microscopes

Scientists

• Robert Hooke studied nature by using a light microscope.– Light microscopes

use optical lenses to magnify objects by bending light rays.

• Anton van Leeuwenhoek was the 1st scientist to observe living cells.

What is a cell?

A cell is the smallest unit of life.The cell theory states:

● All living things are made up of cells● Cells are the basic units of structure and function in living things● New cells are produced from existing cells

What is a theory?

Remember, a theory is not just a hunch, it is an idea supported by a considerable amount of experimental evidence.

Examples of Cells-Why are they different?

The different shapes of cells reflect their different functions.

• The long extensions that reach out in various directions from the nerve cell allows the cell to send and receive nerve impulses(messages)

• The flat, plate-like shape of skin cells suits their function of covering and protecting the surface of the body.

What limits cell size?

• Small cells can exchange substances(oxygen, nutrients, and carbon dioxide) more readily than larger cells because small objects have a higher surface area to volume ratio.

• So, the cells divide!

There are 2 kinds of cells:

• Eukaryotes – Have a nucleus

• Examples of eukaryotes are plants, animals, fungus, and protists

• More complicated

• Prokaryotes – Do NOT have a nucleus

• Examples of prokaryotes are bacteria

• Smaller than eukaryotes

• Less complicated

Cells have specialized structures to carry out functions. These are called organelles.

Cell Organelles:• Nucleus – command center

of the cell. The nucleus houses and protects the cell’s genetic material in the form of DNA. ONLY FOUND IN EUKARYOTES

Chromosomes are structures in the nucleus made of DNA and protein.

• Cytoplasm – the “gel” material inside the cell membrane but not in the nucleus. The organelles live inside the cytoplasm.

Cell Organelles

• Nuclear membrane- a double membrane that surrounds the nucleus and is made up of 2 phospholipid bilayers.

• Nucleolus- within the nucleus, where the assembly (making) of ribosomes begin.

Cell Organelles• Cell membrane

(Plasma membrane) – only allows certain molecules to enter or leave the cell. It also provides protection and support for the cell.

Centriole-located near the nucleus and helps organize cell division. Found in animal cells.

Cell Organelles• Mitochondria – converts

food into energy (ATP) that the cell can use. They are the power centers of the cell.– ATP powers most of the

cells chemical reactions– Highly active cells, such

as muscle cells, can have hundreds of mitochondria.

• Cytoskeleton – supports the cell and helps to maintain the shape. – The same way tent poles

support the shape of a tent.

Cell Organelles:

• Endoplasmic Recticulum (ER) – makes lipids, proteins and other materials that are exported (taken out) of the cell. – Functions primarily as an intracellular highway, a path along

which molecules move from one part of the cell to another.• Rough ER – part of the ER that makes proteins and

phospholipids.• Once these proteins are made, they are later exported from

the cell or inserted into one of the cell’s own membranes.• For example, ribosomes on the Rough ER make digestive

enzymes. -Called “rough” because ribosomes are attached to the

surface and makes it look bumpy.

More Endoplasmic Reticulum• Smooth ER – lacks ribosomes and thus has a

smooth appearance. • Smooth ER builds lipids, such as cholesterol. • In the ovaries and testes, smooth ER produces

the steroid hormones estrogen and testosterone.• In the skeletal and heart muscle cells, smooth ER

releases calcium, which stimulate contraction.• Smooth ER is abundant in the liver and kidney

cells, where it helps detoxify drugs and poisons. Long term abuse of alcohol and other drugs causes these cells to produce more smooth ER.

Cell Organelles:

• Ribosomes – small particles of RNA and protein that direct protein synthesis in the cytoplasm. They build proteins by following instructions that come from the nucleus.

Cell Organelles:• Golgi Apparatus–

modifies, sorts and packages the proteins that come from the Rough ER and either stores them or ships them out of the cell.

• Lysosome – removes waste from the cell. (Destroys cells that are no longer functioning properly.)

• Microtubules-holds organelles in place, maintains a cell’s shape, and act as tracks that guide organelles and molecules as they move within the cell.

• Microfilaments- contribute to cell movement, including the crawling of white blood cells and the contraction of muscle cells.

Movement

• Cilia and flagella-hairlike structures that extend from the surface of the cell, that helps a cell MOVE.

• Cilia-Short, hair-like structures

• Flagella-Long, whip-like structures

Cell Organelles:

• Chloroplasts – ONLY FOUND IN PLANT CELLS

- captures energy from sunlight and converts it into chemical energy in plant cells.

• Cell Wall – NOT FOUND IN ANIMAL CELLS

- provides support and protection for the plant cell.

-Contains a carbohydrate called cellulose.

Cell Organelles

• Vacuoles –saclike structures used to store materials such as water, salts, proteins, and carbohydrates.

Balloon Demo

• How does the odor pass through the balloon?– Molecules of the

substance pass through the small pores or dissolve in the rubber.

– This is called permeability.