Chapter 7 THE CELL Honors:http://www.phschool.com/webcodes10/index.cfm?fuseaction=home.gotoWebCode&wcprefix=cbk&wcsuffix=9999

FYI--Cell Facts Cells are 90% water. Of the remaining molecules present, the dry weight is approximately: 50% protein 15% carbohydrate 15% nucleic acid 10% lipid 10% miscellaneous

All living things are made up of small individual units called: Cells Some organisms consist of one cell (unicellular), while others have many cells (multicellular). Ex. Unicellular: Bacteria, Paramecia; Multicellular: Plant, Animal Cells cannot be seen with the naked eye, therefore they were not discovered until the microscope was developed.

Discovery of Cells Robert Hooke examined thin slices of cork and other plant tissues with a compound microscope, he found box-like structures he called cells. Anton Van Leeuwenhoek observed and described human blood cells and sperm cells and one-celled organisms. Robert Brown in 1831 discovered the cell nucleus, but not its function

Lorenz Oken actually was the first to come up with the ideas in the cell theory, but Matthias Schleiden and Theodor Schwann are credited with the concept of the cell theory when they said that all plants and animals are made of cells.

Cell Theory The cell is the basic unit of structure and function in all living things. Cells can only arise from other cells. There are 2 basic types of cells: Prokaryotic: Lack any internal membrane structures. Without a nucleus. Eukaryotic: Have many membrane-bound structures. True nucleus

A prokaryotic cell is approximately 1 to 10 micrometers and a eukaryotic cell is approximately 10 to 100 micrometers. Smaller cell size has to do with the necessity of getting materials transported into and out of the cell at speeds that will meet the cell’s needs. It is also important to get wastes out of the cell rapidly.

This material exchange rate is limited by the cell’s surface area to volume ratio. When cell’s are small, the surface to volume ratio is large, meaning all parts of the cell surface are close to the external environment.

Cell Structure & Function http://web.mit.edu/esgbio/www/cb/org/organelles.html The structures inside cells are called organelles. “tiny organs” Cell Walls- The cells of most bacteria and all plants are enclosed by a rigid Cell wall. It lies outside the cell membrane and functions to protect the cell. In plant cells it is a composed of a carbohydrate called cellulose.

Plasma (Cell) Membrane A double layered membrane that surrounds the cell. It is composed of phospholipids embedded with proteins. This membrane regulates the movement of certain materials into and out of the cell. It is sometimes called semi-permeable or selectively permeable.

Cytoplasm This is a jelly-like material inside the plasma membrane. All the organelles are held in this fluid and biochemical processes also occur here. Nucleus This organelle is the “brain” of the cell. It contains the chromosomes and DNA, which carry the hereditary information. The nucleus also controls all the biochemical activities.

Nuclear Membrane or Envelope The bilayered membrane that is responsible for protecting the nucleus and only allowing certain substances in and out. Nucleolus This is a small organelle within the nucleus that is involved with the synthesis of ribosomes and rRNA

Endoplasmic Reticulum A series of channels in the cytoplasm that function in synthesizing, and transporting substances made in the cell. There are two types of ER. RER (rough endoplasmic reticulum) which has ribosomes attached and SER (smooth endoplasmic reticulum) where there are no ribosomes.

Ribosomes Mitochondria These organelles are the site of protein synthesis. They may be free floating or attached to the ER. Mitochondria This is a oval shaped organelle with a highly folded internal area called the cristae. The site of aerobic cellular respiration. Most of the body’s cellular energy (ATP) is made here. “Powerhouse of the cell”

Golgi Complex Lysosomes These organelles are flat, membranous sacs arranged like channels that synthesizes, packages, and modifies cell materials. Lysosomes These are small, sac-like structures that contain digestive enzymes. They take part in the digestion of food materials and also break down worn out cell organelles.

Vacuoles Spaces in the cytoplasm that are enclosed by a membrane. They may contain water or other materials. (Contractile vacuole): helps maintain water balance. (Food vacuoles): food is digested. Centriole A cylindrical structure in the cytoplasm that appears to function during the division of animal cells.

Plastids Pigment containing structures. There are three types: Chloroplast: Contains chlorophyll which serves as a site for photosynthesis in plant cells. Leucoplast: Colorless plastids. Stores material such as starch, oils, and proteins. Chromoplast: Contains all the other color pigments

Cytoskeleton Maintains the shape of the cell using a network of protein filaments.

Exceptions to the Cell Theory The first cell could not have arisen from a pre-existing cell. Viruses are not composed of cells but do contain genetic material and can reproduce in the presence of a living cell. Although a mitochondira and chloroplast are considered organelles, they contain genetic material and can reproduce in the presence of

Cell Organelle Mini-Movie http://glencoe.mcgraw-hill.com/sites/dl/free/0078757150/164155/00035804.html http://glencoe.mcgraw-hill.com/sites/dl/free/0078757150/164155/00035805.html