Daily Questions 1.A cell that does not contain a nucleus is a ____________________. 2.The portion of the cell outside the nucleus is the _________________. 3.The layer of two membranes surrounding the nucleus is the ____________________.

Daily Question A scientist wants to measure the effect of phosphorus on a freshwater ecosystem. She creates two model ecosystems in her lab and gives one ecosystem a normal amount of phosphorus and gives the other no phosphorus. Identify the manipulated and responding variable.

Cell Theory All living things are made of cells. Cells are the basic unit of structure and function in living things. New cells are produced from existing cells.

Cellular discoveries Robert Hooke saw dead cells Anton van Leeuwenhoek used a microscope to see living cells Matthias Schleiden found that all plants were made of cells Theodor Schwann said that all animals were made of cells Rudolf Virchow said that new cells could come from old cells

Categories of Cells They either have a nucleus or don’t have a nucleus Nucleus – large membrane-enclosed structure that contains the cell’s genetic material as DNA Eukaryotes – cells that contain nuclei Prokaryotes – cells that do not have a nucleus

The cell as a factory Organelles – specialized structures or little organs Cytoplasm – portion of the cell outside the nucleus The nucleus contains nearly all the cell’s DNA and with it the coded instructions for making proteins and other important molecules.

More about the nucleus Nuclear envelope – layer of 2 membranes that surrounds the nucleus of a cell Chromatin – DNA bound to protein Chromosomes – distinct threadlike structures containing the genetic information passed from one generation of cells to the next Nucleolus – brain of the nucleus where ribosomes assembled

Ribosomes and the ER Small particles of RNA where proteins are assembled Endoplasmic reticulum – internal membrane system where lipid components of the cell membrane are assembled along with proteins and other materials Proteins go from ribosomes to ER Smooth ER has enzymes that perform special tasks

Googly Golgi Bodies Golgi apparatus – modifies, sorts, and packages proteins and other materials from the ER for storage or secretion outside the cell Like a custom shop Also makes lysosomes

Lysosomes and Vacuoles Lysosomes – small organelles filled with enzymes Digest fats, carbohydrates, and proteins Also break down old organelles The garbage disposal of cells Vacuoles – sacs that store water, salts, proteins and carbohydrates

Mighty mitochondria Mitochondria – organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use The powerhouses of the cell Inherited from your mother

Chloroplasts Organelles that capture the energy in sunlight and convert it to chemical energy through photosynthesis Animal cells do NOT have chloroplasts Contain the green pigment chlorophyll, which makes plants green

Structure: Cytoskeleton Cytoskeleton – network of protein filaments that helps cell to maintain its shape Only in eukaryotic cells Microfilaments are threadlike structures that support the cell Microtubules are hollow structures made of proteins (tubulins) Centrioles are structures made of tubulin that are found near the nucleus and help cell division (only in animal cells)