Cell Structure and Function

The cell theory grew out of the work of many scientists and improvements in the microscope. Many scientists contributed to the cell theory. More was learned about cells as microscopes improved.

The cell theory grew out of the work of many scientists and improvements in the microscope. Many scientists contributed to the cell theory. More was learned about cells as microscopes improved. The cell theory is a unifying concept of biology.

Early studies led to the development of the cell theory. The Cell theory has three principles. All organisms are made of cells.

Early studies led to the development of the cell theory. The Cell theory has three principles. All organisms are made of cells. All existing cells are produced by other living cells.

Early studies led to the development of the cell theory. The Cell theory has three principles. All organisms are made of cells. All existing cells are produced by other living cells. The cell is the most basic unit of life.

Prokaryotes Genetic material is not in a nucleus Less complicated and smaller than eukaryotic cell Example: Bacteria **An organism made of a prokaryotic cell is called a prokaryote.

Prokaryotic Cells

Eukaryotes Genetic material is contained in a nucleus and separated from the rest of the cell More complex and larger than prokaryotic cells Example: Plants, animals, fungi, protists **An organism made of eukaryotic cell(s) is called a eukaryote.

Eukaryotic cells Diatoms (algae) Root tip Neuron Uterine cells

Eukaryotic cell structure Two major parts: Nucleus Cytoplasm-portion of the cell outside the nucleus that contains organelles (parts or “organs” of the cell)

Nucleus-The control center Structure: Surrounded by a double membrane called a nuclear envelope. It is dotted with many nuclear pores to allow materials (RNA, proteins, etc) in and out of the nucleus.

Nucleus Function: Contains almost all of the cell’s DNA for coding proteins and other molecules. DNA is found on chromosomes which contain genetic information. The Control Center of the cell!

Nucleolus Structure: Function: Small dense region in the center of the nucleus Function: where ribosomes are made.

Ribosomes Structure: Function: Small pieces of RNA and protein found throughout the cell. Two subunits. Function: Site of protein synthesis.

Rough Endoplasmic Reticulum Structure: Membranous system Rough ER- has ribosomes on surface to assemble proteins Continuous with the nuclear envelope Function: Site where lipid parts of cell membrane are made, along with proteins and other materials to export from the cell.

Smooth Endoplasmic Reticulum Structure: Membranous system NO ribosomes on surface Function: Synthesis of lipids and phospholipids for membranes Detoxifies drugs and toxins in the cell

Golgi Apparatus Structure: Function: Stack of closely packed membranes Modify, sort, and package proteins and other materials from the ER for storage in the cell or release from the cell. It puts the finishing touches on proteins.

Lysosomes Structure: Function: Small sac, filled with digestive enzymes Function: Breakdown of lipids, carbohydrates and proteins into small molecules to be used by the rest of the cell Breakdown used up organelles Gets rid of all “stuff” in the cell The “Clean-up crew”

Vacuole Structure: Function: Sac-like Plant cells have one large central vacuole Animal cells have many small vacuoles Function: Stores water, salts, proteins and carbohydrates

Mitochondria Structure: Function: Enclosed by two membranes with the inner folded membrane, called cristae. Contains it’s own DNA (Evidence for the Endosymbiotic Theory) Function: Convert chemical energy in food into materials easier for the cell to use. This is called cell respiration.

Chloroplasts Structure: Function: Surrounded by two membranes Stacks of membranes inside called thylakoids. Contains own genetic information like mitochondria Contains green pigment called chlorophyll Not found in animal cells! Function: Captures energy from the sun (solar energy) and changes it into food (chemical energy) for plants (photosynthesis).

The History of the cell continued In 1967, Lynn Margulis proposed that mitochondria and chloroplasts were descended from ancient symbiotic prokaryotes. This theory is called the Endosymbiotic Theory! Click on image to view video

Cytoskeleton- structure and support Two types: microfilaments and microtubules- made of proteins Function: Helps maintain cell shape Helps with movement of the cell (i.e. flagella and cilia)

Flagellum Structure: Function: long, whip-like structure made of microtubules Function: Allows the cell to swim through fluid

Cilia Structure: Function: small hair-like structures made of microtubules; beat rhythmically to move fluid outside the cell. Function: This propels or anchors the cell.

Centrioles Structure Function Pair of cylindrical arrangement of microtubules found perpendicularly to each other Region around centrioles called centrosome Function help Divide the DNA in ANIMAL CELL division

Cell Membrane Structure: Function: Double membrane called a lipid bilayer Flexible structure that forms a strong barrier between the cell and its surroundings Phospholipids with integral proteins and cholesterol Function: Regulates what enters and leaves the cell Provides protection and support

Cell Wall Structure: Function: Lies outside the cell membrane Made of structural carbohydrates Found in plants, algae, fungi and many bacteria NOT FOUND IN ANIMAL CELLS! Function: Provides support and protection for the cell

Levels of organization (smallest to largest) 1. Cells 2. Tissues: group of similar cells with specific function Four types: muscle, epithelial, nervous, connective tissue 3. Organs: groups of tissues working together 4. Organ systems: a group of organs that work together to perform a specific function Examples: Nervous system, digestive system