Chapter 5 Lesson What are cells?

Vocabulary Preview Cell: basic unit of structure and function of ALL living things Tissue: a group of cells that work together to perform certain functions Organ: a group of tissues that work together to perform a certain function Organ System: a group of organs that work together to do a job for the body

Cells as Building Blocks Cell: is the basic unit of structure and function in living things Most cells are microscopic…..what does microscopic mean? A scientist named Robert Hookes observed a thin layer of cork through a microscope. When he looked at the cork through a microscope, it looked like tiny rooms so he called them cells.

Cells as Building Blocks Hooke’s description of cells made scientists want to know more about them. Using microscopes, they learned that all living things are made of cells. They found cells share some characteristics. Also different kinds of cells do different things.

Cells as Building Blocks Every living thing, or organism is made up of cells. Some simple organisms are just a single cell. Most plants and animals contain many cells. Plants and Animals have different types of cells, each with its own job.

Cells are Building Blocks The different cells work together to carry out life functions that keep an organism alive and healthy. Ex: Your body has cells that: break down food, carry oxygen, and carry away waste To perform these functions, each cell contains structures called organelles. Each organelle has a certain job that helps keep the cell alive.

The outer cells of this plant’s leaf help keep the plant from losing too much water. The leaf’s inner cells make food for the plant. A salamander’s skin cells don’t look like a plant’s cells, but they also help keep the organism from drying out. The single cell that makes up this amoeba [uh•MEE•buh] carries out all the functions that the organism needs to stay alive.

Cell Structures and Functions All plant and animal cells have certain organelles in common. Ex: every cell has a thin covering called the cell membrane The cell membrane protects the cell, holds it together, and controls what goes in or out of the cell.

Plant and Animal Cells Plant and Animal cells both have a nucleus. This organelle directs all of a cell’s activities. Inside the nucleus are threadlike chromosomes that have information about the cell’s activities. When a cell reproduces itself by dividing, the nucleus first makes a copy of each chromosome. The new cell gets the copies.

Plant and Animal Cells Between the cell membrane and the nucleus is the cytoplasm. Cytoplasm: a jelly-like material that contains chemicals that keep a cell healthy. Several organisms float in the cytoplasm. Mitochondria are the “powerhouses” of plant and animal cells. Mitochondria release energy from nutrients. Vacuoles store nutrients, water, or waste materials in plant cells. Vesicles has similar functions in animal cells.

Plant and Animal Cells Plant cells have some structures that are not found in animal cells. A thick cell wall helps support a plant cell. The cell wall lies outside the cell membrane. In the cytoplasm of many plant cells, there are chloroplasts. Chloroplasts make food for plant cells.

Cells, Tissues, Organs, Systems Multi-cellular of many celled organisms like you are made up of trillions of cells. Each cell is able to carry out its own life functions. The cells in multi-cellular organisms work together. Cells that work together to perform a specific function form a tissue.

Single-Celled Organisms Single-Celled Organisms function differently. They don’t have organs or tissues. The one cell that a single-celled organism has must eat, move, and do all other functions necessary for survival.