Characteristics of the Cell

Cells Cells- the smallest unit that can perform all the functions needed for life All organisms are made of cells. Cells all have the same basic parts and processes. The picture shows onion cells under a microscope.

Cell Theory 1665- Cells were first discovered by Robert Hooke when he was looking at cork under a microscope. “The Wacky History of Cell Theory” http://ed.ted.com/lessons/the- wacky-history-of-cell-theory

Current Cell Theory… All organisms are made of one or more cells. The cell is the basic unit of all living things. All cells come from existing cells.

Cell Structure All cells have the following parts: Cell Membrane- a layer that covers and protects the cell Creates a boundary between the inside of the cell and the surrounding environment Controls what goes in and out of the cell Cytoplasm- the fluid material inside the cell membrane

Cell Structure DNA- the genetic information that holds information needed to make new cells and new organisms Organelles- parts inside of the cell that do different jobs Ex: Ribosome, nucleus

Prokaryotic and Eukaryotic Cells Eukaryotic cells have a nucleus and prokaryotic cells do not. Nucleus- a structure enclosed by a membrane that contains most of the cell’s DNA. Prokaryotic Cells- do not have a nucleus so the DNA floats in the cytoplasm. No nucleus DNA shaped like a twisted rubber band No membrane-bound organelles A cell wall outside the cell membrane

Prokaryotic and Eukaryotic Cells have a nucleus DNA in nucleus 10 times larger than prokaryotic cells Eukaryotic cells have organelles. Most eukaryotes are multicellular, but some are unicellular

Prokaryotic and Eukaryotic Cells

Organization of Living Things Organism- any living thing Organisms can be unicellular or multicellular Benefits of being multicellular Larger size Longer life Specialization

Levels of Organization Cells Tissues Organs Organ Systems Organism

Cells are specialized Multicellular organisms have many different types of specialized cells Each specialized cell has a particular job called its function. Cells with special functions generally have a structure that suits them for that job Ex: The function of a red blood cell is to carry oxygen to other cells. A red blood cell is small and smooth. This helps it slip through small blood vessels.

Levels of Organization Tissue- a group of cells that work together to do a specific job Ex: muscle cells are organized into muscle tissue Organ- a structure made of two or more tissues that work together to do a job Ex: Heart- made of muscle, nerve, and other types of tissues. Organ system- a group of organs working together to do a job Ex: the stomach is part of the digestive system Organism- Organ systems are organized into the organism. The different organ systems work together to carry out all the life functions of the individual.