Cells

What is a cell? Structural and functional unit of all organisms. Some can work independently (on their own) to carry out all of life’s processes. Some cells have organelles, some don’t. Organelles are small, specialized cellular subunits separated from the rest of the cell by membranes. Organelles help a cell to move molecules, create and store energy, and store information.

Important People and Cells Robert Hooke (1665) – coined the word “cell” to describe what he saw when looking at slices of cork under a microscope. Antony Van Leeuwenhoek (1600s) – invented the microscope. Schwann (animal cells), Schleiden (plant cells), and Virchow – Between the 3 of them they came up with the Cell Theory.

The Cell Theory All living things are made of cells. Cells are the basic unit of all living things. All cells come from other living cells of the same kind.

Basic Cell Structure (Three Basic Parts) Cell Membrane. A thin, flexible boundary surrounding the cell. Cytoplasm. The watery, jelly-like part of the cell that contains salts, minerals, and the cell organelles. Genetic Material. The area of the cell where the DNA (deoxyribonucleic acid) is stored. It regulates all cell activities.

Diagram of a typical animal (eukaryotic) cell, showing subcellular components. Organelles: (2) nucleus (11) cytoplasmanimaleukaryotic Organellesnucleuscytoplasm

Microscopes Compound Light Microscope Invented in the 1590s. Allows limited view of a cell. Scanning Electron Microscope Invented in 1920s. Allows us to see individual organelles. Transmission electron microscope allows scientists to see cells in greater detail; it uses a beam of electrons to take 3-D pictures of cells.

Prokaryotic vs. Eukaryotic Cells Prokaryotic Does not have a true nucleus. Genetic material is not enclosed in a membrane. They have no membrane- bound organelles. Bacteria are prokaryotic cells. Eukaryotic Has nucleus surrounded by membrane. DNA is located in nucleus. Has several membrane- bound organelles. Tend to be larger than prokaryotes. Plants and animal cells are both eukaryotic.

Parts of a Eukaryotic Cell Plastid – structures used in photosynthesis and product storage. Only in plants. Cell Wall – Rigid membrane around plant cell; provides shape and support. In plants only. Vacuoles – spherical storage sac for food and water; larger in plants. Golgi Apparatus – flattened membrane sacs for synthesis, packaging, and distribution.

Parts of Eukaryotic Cells (cont’d) Mitochondria – Rod-shaped double membranous structures where cellular respiration (energy release) takes place. Endoplasmic Reticulum – Folded membranes having areas with and without ribosomes used for transport of RNA and proteins. Nucleus – control center of the cell; location of hereditary material (DNA); surrounded by nuclear envelope/membrane.

Parts of Eukaryotic Cells (cont’d) Ribosomes – structures that manufacture proteins; found on endoplasmic reticulum and floating in cytoplasm. Lysosomes – sperical sac containing enzymes for digestive functions; recycling center of cell. Cell membrane – Membrane surrounding the cell that allows some molecules to pass through; also called bilipid layer.

Parts of Eukaryotic Cells (cont’d) Cytoplasm – Jelly-like substance in the cell around the nucleus and organelles; site of many metabolic cycles and protein synthesis. Microfilaments/Microtubules – fibers and tubes of protein that move internal cell parts. Nucleolus – inside nucleus; site of ribosome production. Nuclear envelope/membrane – double membrane that surrounds nucleus.

Parts of Eukaryotic Cells (cont’d) Centrioles – short tubes necessary for cell reproduction in some cells. In animal cells only. Cilia – Short, hair-like extensions on the surface of some cells; used for movement and food gathering. Animal cells only. Flagella – Long, whip-like extension on the surface of some cells; used for movement. Animal cells only.