Cell StructureChapter 3 By Mr. Kling
Cell- The smallest unit capable of carrying out all the functions of life.
Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell
Discovery of the Cell • The English scientist RobertHooke used one of the first microscopes to observe a thin slice of cork in 1665. He saw a lot of little boxes, which reminded him of the small rooms where monks lived. He called then cells. • In 1675, the Dutchscientist Anton van Leeuwenhoek used a microscope to look at a sample of clear pond water and saw single celled organisms.
Formation of The Cell Theory • In 1838, a Germanbotanist,MatthiasSchleidenconcluded that all plants were entirely composed of cells. • In 1839, the German zoologist TheodorSchwannconcluded that animals were entirely composed of cells. • In 1855, the German physician RudolphVirchow determined (while studying how disease affects living things) that cells only come from other cells. • These 3 scientists are credited, together, as creating the cell theory.
The Cell Theory • All living things are composed of 1 or more cells. • In organisms, cells are the basicunitsof structure and function. • Cells come only from existing cells.
History of Cells • The first cells had no separate, internal parts (organelles). They are called prokaryotes. • These were the only living things to exist for the first 2 billion years on Earth. • Prokaryotes are the mostcommon type of cells on Earth. • Prokaryotes are very small (1-15 um). • Example: bacteria
History of Cells • About 1.5 billion years ago, cells developed a nucleus and other membrane-bound cell parts (organelles). The cells are called eukaryotes. • Eukaryotes can be larger (2-2,000 um). • Early eukaryotes were single-celled (unicellular). • Eventually, many eukaryotic cells joined together and formed multicellular (many celled) organisms. • Each cell is able to specializein certain activities. • Examples: nerve cells carry messages muscle cells contract the outside of the cell membrane.
Two Types of Cells • Prokaryotic • Eukaryotic
Prokaryotic • Do not have structures surrounded by membranes • Few internal structures • One-celled organisms, Bacteria http://library.thinkquest.org/C004535/prokaryotic_cells.html
Eukaryotic • Contain organelles surrounded by membranes • Most living organisms Plant Animal http://library.thinkquest.org/C004535/eukaryotic_cells.html
Cell Size • Cells must be small. • There are approximately 100 trillion (100,000,000,000,000) cells in the human body.
Why are cells so small? • Surface-to-Volume ratio • Food, water, oxygen, and other materials must enter through the surface. Waste products must leave through the surface. • As a cell grows, its volume increases morerapidly than its surface area does. • As a cell size increases, it takes longer for information and materials to reach their destination. Small cells are more efficient.
Eukaryotic Cell Parts (Organelles) • Animal Cell Parts • Cell Membrane- The outer bilipid boundary of a cell. Also called the plasma membrane. • Cytoplasm- The jelly-like fluid in a cell. • Ribosomes- Site of protein synthesis. • Endoplasmic Reticulum- A folded membrane system used for a molecular transport in the cell. There are 2 types of ER, smooth and rough. Rough ER has lots of ribosomes. • Golgi Apparatus- Secretes waste products. • Mitochondria- Site of aerobic respiration in cells. • The energy distribution center of the cell. • Lysosomes- Site of the cellular digestion. • Microtubules- Long, slender, tube-shaped organelles that help give the cell shape and support.
Animal Cell Parts (continued) • Microfilaments- Fine, threadlike organelles that help give the cell shape and support. • Cilia- Hair-like structures on the outside of the cell that help the cell move. Example: The cilia that surround a paramecium. • Flagella- Hair-like structure that helps the cell move. Example: The tail of a sperm cell. • Nucleus- Contains most of the cell’s DNA. • Nuclear Envelope- The membrane that surrounds the nucleus. • Chromatin- The DNA and proteins in the nucleus of a nondividing cell. • Chromosome- DNA in a coiled, rod-shaped form that occurs during cell division. • Nucleolus- Site in the nucleus where ribosomes are created.
Plant Cell Parts • Plant cells have all the parts of animal cell, plus a few more. • The additions: • Cell Wall- A strong, rigid layer on the outside of the cell membrane. • Vacuoles- A fluid-filled cavity that stores waste products. In a mature plant cell, the vacuole typically takes up 90% of the volume. • Plastids- An organelle in which food or pigments are stored. There are 3 types: • Chloroplasts- Contain chlorophyll. • Chromoplasts- Contain orange carotenes, yellow xanthophylls, and various red pigments. • Leucoplasts- Store food such as starches, proteins and lipids. Especially common in potato tubers.