How Can Organisms Maintain Life? Prokaryote (Plant and Animal Cells) Eukaryote (bacteria) Multicellular

Looking Inside Cells (basic unit) Cells contain Tiny structures called organelles, which carry out specific functions to keep the cell alive

Cell Wall Surrounds the cells of plants and some other organisms Rigid layer of nonliving material (cellulose) Protects and supports

Cell Membrane Controls what substances come into or out of the cell Thin selectively permeable coating Surrounds cell (just inside cell wall or on the outside of cells without a wall)

Nucleus Cell’s control center Directs all of the cells activities Nuclear membrane surrounds and protects Pores in membrane allow materials to pass through Chromatin contain genetic material, the instructions that direct the functions of cell Nucleolus produces ribososmes

Mitochondria Produces most of the energy needed by the cell (ATP) through chemical reactions The“Powerhouse” of the cell Contains its own DNA (mother’s) Surrounded by two membranes- inner has long folds to increase surface area

Microscope View of the Mitochondria

Endoplasmic Reticulum Carry proteins and other materials from one part of the cell to another Maze of passageways

Two Types of ER -Not covered with ribosomes -Involved in the synthesis of steroids, regulation of calcium levels, and breakdown of toxins Covered by ribosomes Make proteins to be exported or inserted into the cell membrane

Microscopic Views of Endoplasmic Reticulum

Ribosomes Function as factories to produce proteins Attached to surface of endoplasmic reticulum or floating in the cytoplasm

Golgi Bodies Cell’s mailroom Receive protein and other newly made materials, package them and distribute them to other parts of the cell Look like a collection of sacks and tubes

Microscopic View of the Golgi Apparatus

Chloroplasts Only found in the cells of plants and some other organisms Capture energy from the sun and use it to produce food for the cell (photosynthesis) Gives plants their green color

Vacuoles Storage area of the cell Most plant cells have one large vacuole Store water, food, and other needed materials Store waste until disposed of

Lysosome More common in animal cells than plant Cell’s cleanup crew Contain chemicals that beak down large food molecules or old worn-out cell parts

Lysosome Destroying a Mitochondrial Membrane

Cytoskeleton -Maintains shape and size -Long protein strands -Helps in the movement of organelles in the cell

Microfilaments Smallest strands that make up the cytoskeleton Microtubules - largest strands of the cytoskeleton, during cell division extend across the cell (spindle fibers) and assist in the movement of chromosome

Cilia and Flagella -Hairlike and extend form the surface of the cell -Assist in movement -Cilia: short and many present in number -Propel organisms through fluid

Bacterial Cells Usually smaller than plant or animal cells Called Prokaryotic cells Have cell walls and cell membranes and ribosome Genetic material not enclosed in a nucleus Does not contain the other organelles

Specialized Cells Multicellular organisms contain specialized cells These may be different in size and structure because of the different functions Examples include nerve cells, blood cells, skin cells, etc.

How do cells specialize or differentiate? All of the cells in a multicellular organism have the same DNA. The cells differentiate by only reading part of the genetic code. The part of the code needed to do a specific job. For example bone cells use only the part of the DNA code that is for making bone. Even though the entire set of directions is present only the part for bone is used.

Levels of organization in multicellular organisms Specialized cells working together to perform a job for the organism are called tissue. Different tissues that work together to perform a job are called organs Different organs that work together to perform a job are called organ systems The organ systems working together form the organism.