Notes: Organelles

Plasma Membrane Outer surface of the cell. Only allows certain things in or out. Separates internal reactions from the external environment. Allows cell to dump waste and interact with its environment.

Plasma Membrane Made of phospholipids. They have a polar, phosphate head and 2 nonpolar, fatty acid tails. Polar end points out, toward water, nonpolar tails point in, away from water. Creates a double layer called the phospholipid bilayer

Membrane Proteins Plasma membranes often contain specific proteins – called integral proteins – that are embedded in the lipid bilayer.

The cell membrane is… The doors into and out of the factory:

Fluid Mosaic Model States that the phospholipid bilayer behaves like a fluid more than it behaves like a solid. The membrane’s lipids and proteins can move sideways within the bilayer, like a boat on the ocean. As a result, the cell membrane is constantly changing.

Nucleus The nucleus directs the cell’s activities and stores DNA. Nuclear Envelope: Double membrane surrounding the nucleus. Made of two phospholipid bilayers. Covered with tiny, protein-lined holes called nuclear pores. They provide exits/entrances for RNA

The nucleus is… The big boss (CEO) Tells everyone else what to do

Nucleolus Nucleolus: Area in the nucleus where DNA is concentrated when it is making ribosomal RNA. Ribosomes are organelles that direct protein creation in the cytoplasm

Mitochondria Mitochondria are organelles that transfer energy from organic molecules to ATP. ATP ultimately powers most of the cell’s functions. Mitochondria are known as the “power house” of the cell. The more active the cell, like muscle cells, the more mitochondria they have. Like nucleus, has an inner and outer phospholipid membrane. Inner membrane is made of many folds called cristae. Mitochondria have their own DNA and are only reproduced from preexisting mitochondria. Cells need a constant source of energy. The energy for cellular functions is produced by chemical reactions that occur in the mitochondria and chloroplasts (in plants).

The mitochondria is… The power generator for the factory Creates useable energy

Ribosomes Ribosomes are small, spherical organelles that are responsible for building protein. Do not have a membrane. Made of protein and RNA molecules. Classified as “free” or “membrane-bound”. “Free”: can move anywhere throughout the cytosol. “Membrane-bound”: attached to the rough Endoplasmic reticulum

The ribosomes are… The factory workers on the assembly line Ribosomes build proteins

Endoplasmic Reticulum The Endoplasmic Reticulum (ER) is a intracellular highway. A network of tubes and sacs that provide a pathway along which molecules move within the cell.

Endoplasmic Reticulum Two parts: Rough ER: system of interconnected, flattened sacs covered with ribosomes. Produces phospholipids and certain proteins. Produces digestive enzymes. Smooth ER: doesn’t have the ribosomes, which is why it’s smooth. Helps detoxify drugs and poisons in liver and kidney cells.

The ER is… An assembly line….(where the workers do their work) Items move along a conveyer belt to different parts of the plant ER moves items to different parts of the cell in the same way!

Golgi Apparatus The golgi apparatus is also made of flattened, membranous sacs. The part nearest the nucleus receive vesicles from the ER that have new proteins or lipids. Proteins get labels, which direct them to other parts of the cell or prepare them to leave

The golgi apparatus is… The finishing / packaging department Gets things ready to leave the cell

Lysosome A lysosome is a vesicle produced by the Golgi apparatus. They contains digestive enzymes that break down large molecules. Breaking down cells when they die. They are integral in maintaining the health of cells.

The lysosomes are… The cleaning crew / custodians They clean up the cell

Cytoskeleton The cytoskeleton is a network of thin tubes and filaments that crisscrosses the cytoplasm. It provides structure to the cell like tent poles do for a tent.

The cytoskeleton is… The beams and poles supporting the factory

Centrioles Part of the cytoskeleton Are involved in cell division. Found in the cytoplasm, near the nuclear membrane. Don’t exist in plant cells.

The centrioles are… The supervisors who divide the work to everyone else.

Cilia and Flagella Hair-like structures that extend from the surface of the cell They assist in movement. Cilia are short and present in large numbers. Flagella are long and less numerous.

The flagellum are… Conveyor belts or carts The key here is that they move

Plant Organelles Cell wall: rigid layer that lies outside the plasma membrane. Provides structure and protection. Contains cellulose Central vacuoles: large, fluid-filled reservoirs. Store water, enzymes, and waste products. Provide support for plant tissue. Can make up 90% of plant cell’s volume. The lifestyle of plants is different than that of animals. They make their own carbon molecules from carbon taken from the environment. Cell wall contains cellulose a carbohydrate that helps form a stiff box around each cell. Vacuole - When there’s lots of water, it fills the vacuole and the cells expand, allowing the plant to stand upright. When there’s little water, the vacuoles lose water and the plant wilts.

Plant Organelles Cont. Chloroplast Uses light energy to make carbohydrates from CO2 and H2O (photosynthesis). Are surrounded by two membranes. Contain chlorophyll is the molecule that absorbs the light. Plant cells may have several chloroplasts.

The chloroplasts are the… The cell wall is the… Factory gates The chloroplasts are the… Power generators The vacuole is the… Storage closet

Comparing Cells Both animal (b) and plant cells (c) have: Organelles Cell Membrane Cytoplasm Plant Cells (c) have: Cell wall Central vacuole Plastids