Eukaryotic Cells Eukaryotic cells are more complex than prokaryotic cells. They are identified by the presence of certain membrane-bound organelles. Prokaryotic cells have organelles too, but much fewer and they are all free-floating in the cytoplasm Organelles are specialized structures within a cell that perform a specific function Organelle literally means little organ Most of the organelles we will talk about are only found in eukaryotic cells
The Leadership The Nucleus Eukaryotic cells contain a nucleus, which is the storage organelle for chromosomes Chromosomes are long strands of DNA The nucleus contains four sections Chromatin: the DNA Nucleolus: where ribosomes are constructed Nuclear envelope: the membrane of the nucleus Nuclear pores: holes on the envelope that allow ribosomes to pass in and out of the nucleus
The Leadership Ribosomes **Ribosomes are found in prokaryotic cells as well** Ribosomes receive coded messages from the nucleus telling the ribosome how to construct specific proteins Each cell contains millions of ribosomes, some free floating in the cytoplasm, some attached to other organelles
The Endoplasmic Reticulum The Workers The ER are long series of narrow tubes throughout the entire cell Rough ER Rough ER looks rough because it has ribosomes attached to it The rough ER contains necessary materials for building proteins It also helps add other molecules to proteins and helps shape proteins
The Workers The Smooth ER The smooth ER is the same structure as the rough ER but with no ribosomes attached Smooth ER builds lipids and steroids The specific steroids a cell builds are based on where the cell is The smooth ER of a liver cell will produce insulin; smooth ER of the testes will produce testosterone, etc
The Workers The Golgi Apparatus The Golgi Apparatus is a series of curved folded sacs. The Golgi determines the final destination of proteins and lipids in cells and delivers them using packages of phospholipids called vesicles Lysosomes Lysosomes are small vesicles that contain powerful hydrolyzing enzymes Lysosomes engulf and destroy dead cell structures or invading organisms Lysosomes return the broken down materials back to the cell to use as supplies
Peroxisomes The Workers Peroxisomes are small vesicles that, unlike lysosomes, are capable of breaking down lipids One common byproduct of peroxisomes is hydrogen peroxide, which is toxic to most cells. Cells contain additional enzymes to protect the cell from it s own H 2 O 2 Vacuoles Vacuoles are larger vesicles used for storing substances, usually water. Animal cells contain numerous smaller vacuoles Plant cells contain one enormous vacuole
The Power Plants Mitochondria The mitochondria convert sugars into usable energy sources called ATP Chloroplasts Chloroplasts of cells harness energy from sunlight and use this energy to build ATP and sugars Plant and animal cells both contain mitochondria, but only plant cells contain chloroplasts Chloroplasts and mitochondria also contain their own DNA, suggesting at one point in history they were a separate organism This is called endosymbiotic theory
Cytoskeleton The Infrastructure Within the cytoplasm are multiple series of small filaments, nearly invisible to even microscopes All these filaments put together are called the cytoskeleton Both prokaryotic and eukaryotic cells contain cytoskeleton Microfilaments: a highway for transporting materials within the cell Microtubules: internal structural support, anchoring organelles to the cytoplasm Centrioles: used in cell division
The Infrastructure Cilia and Flagella Cilia: millions of hair-like projections that move the cell similar to a rowboat Flagellum: a long extension of microfilaments that whips back and forth, like a propeller Cilia and flagella are found outside the cell attached to the plasma membrane Both are used to move cells and are particularly found in unicellular organisms
Cell Comparison Trait Prokaryotic Cells Eukaryotic Animal Cells Eukaryotic Plant Cells Cell Wall Yes (peptidoglycan) No Yes (cellulose) Plasma Membrane Yes Yes Yes Ribosomes Yes Yes Yes Lysosomes No Yes Maybe Mitochondria No Yes Yes Chloroplast No No Yes Centrioles (Ch 9-10) No Yes No Vacuole No Yes (multiple small) Yes (one large) All other organelles No Yes Yes