Organelles

Structure and Function of Organelles The Structure and Function of the following organelles will be discussed: –Cell Membrane –Nucleus –Cell Wall –Cytoplasm –Cytoskeleton –Ribosomes –Endoplasmic Reticulum –Golgi Apparatus –Mitochondria –Lysosomes –Centrioles –Vacuoles –Chloroplast

Cell Membrane The protective barrier between the cell and the external environment Made of fatty molecules called phospholipids ▫Doesn’t dissolve in water and forms a protective layer around the cell. Membrane allows some substances to pass through it by diffusion

Cell Wall (Plant Cells Only) A boundary around plant cells that provides structure and support. ▫Outside of the cell membrane

Nucleus The “brain” of the cell. Manages cell function and contains the DNA in a small, dense portion called the nucleolus. Chromatin – A series of proteins and DNA that make up the nucleus.

Cytoplasm A jelly like substance that surrounds and contains the organelles.

Cytoskeleton A network of thin fibers that acts as a support system for organelles. ▫Maintains the shape of a cell.

Ribosomes Used by the cell to synthesize proteins. Very small organelles that are either free-floating or attached to another organelle.

Endoplasmic Reticulum Structure: a system of membranous tubules and sacs Function: intercellular highway (a path along which molecules move from one part of the cell to another) Two types: ▫Rough Endoplasmic Reticulum ▫Smooth Endoplasmic Reticulum

Rough Endoplasmic Reticulum Rough Endoplasmic Reticulum (rER): prominent in cells that make large amounts of proteins. ▫Covered with Ribosomes

Smooth Endoplasmic Reticulum Smooth Endoplasmic Reticulum (sER): involved in the synthesis of lipids (fats) and breakdown of toxic substances ▫Not covered with Ribosomes

Golgi Apparatus Structure: stacked flat sacs Function: Receives proteins and fats from the endoplasmic reticulum and distributes them to other parts of the cell using Vesicles. (receiving, processing, packaging, and shipping) ▫Vesicles are membrane bound sacs containing proteins and fats

Mitochondria Structure: folded membrane within an outer membrane Function: converts energy stored in food into usable energy for work ▫cellular respiration

Lysosomes (Animal Cells Only) Structure: spherical organelles that contain enzymes Function: breaks down food particles, invading objects, or worn out cell parts ▫The lysosomes clean up the cells

Centrioles Structure: composed of nine sets of triplet microtubules arranged in a ring ▫Exist in pairs Function: centrioles play a major role in cell division (mitosis) ▫More on this later!

Vacuoles Structure: a sac of fluid surrounded by a membrane ▫Very large in plants ▫Tend to be small in animal cells Function: used for temporary storage of wastes, nutrients, and water Very large in plants ▫When it fills with water the plant cells become firm.

Chloroplasts (Plant Cells Only) Structure: stacked sacs (thylakoids) that contain chlorophyll surrounded by a double membrane ▫Stroma – thick fluid that surrounds the thylakoids Function: photosynthesis

Animal Cell Cross Section

Plant Cell Cross Section

Plant Cells vs. Animal Cells Animal cells are very similar to plant cells except for the following major differences: ▫Animal cells do not contain chloroplasts ▫Animal cells are not surrounded by cell walls ▫The vacuoles in plants are much larger than those of animals

Elodea Human Cheek Cells Plant Cells vs. Animal Cells