Cell Structure Chapter 3 By Mr. Kling

Cell- The smallest unit capable of carrying out all the functions of life.

Examples of Cells Amoeba Proteus Plant Stem Red Blood Cell Nerve Cell Bacteria

Discovery of the Cell The English scientist Robert Hooke used one of the first microscopes to observe a thin slice of cork in He saw a lot of little boxes, which reminded him of the small rooms where monks lived. He called then cells. In 1675, the Dutch scientist 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 German botanist, Matthias Schleiden concluded that all plants were entirely composed of cells. In 1839, the German zoologist Theodor Schwann concluded that animals were entirely composed of cells. In 1855, the German physician Rudolph Virchow 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 basic units of 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 most common 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 specialize in 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

Eukaryotic Contain organelles surrounded by membranes Most living organisms PlantAnimal

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 more rapidly 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.