Biology

Unit 2 Notes:Cells & Organelles

(1) Cells• All living things must:

• Be made of at least one cell.

• Make new cells from pre-existing cells.

• Some living things are:• Made of just 1 single cell “Unicellular” or “Single Celled”

• Made of many specialized cells “Multicellular”

• Cells have to complete processes to keep us living and healthy using organelles.

• Organelles: Small structures found inside cells, each with a specialized structure and function.

MulticellularUnicellular

(2) Organelles to Know• Nucleus: Stores and protects genetic information.

• Ribosome: Connects amino acids to form proteins.

• Endoplasmic Reticulum: Folds proteins into correct structures and ships where needed.

• Golgi Body: Sorts, Packages and Ships cell molecules.

(“Organelles to Know” Continued)• Mitochondrion: Completes cellular respiration in all cells.

• Chloroplast: Completes photosynthesis in plant cells.

• Cell Membrane: Controls what enters and exits the cell.

• Cell Wall: Provides extra structure and support in plant cells.

(3) Why Organelles Inside Cells?• Organelles help cells complete a wide variety of functions.

• There are two types of cells:• Prokaryotic Cells = Cells without a nucleus, and few organelles.

• Eukaryotic Cells = Cells with a nucleus and many organelles.

• The Endosymbiotic Theory:• Provides an explanation for organelles inside cells.

(4) The Endosymbiotic Theory:• Organelles were once free-living single celled organisms.

• The smaller organisms could live inside larger ones.

• Smaller organisms became structures we now call “organelles”.

• Evidence for the Theory:• Organelles have a membrane just like the outside of cells.

• Mitochondria have their own genetic information.

• Mitochondria and Chloroplasts can reproduce and function without the cell.

• Organelles are similar in structure to bacteria.