the discovery of cells

• Robert Hooke: 1665; looked at cork (tree bark) under a microscope of sorts, noticed hollow compartments that looked like rooms in a monastery that were called “cells”

• cell theory was developed by scientists Schleiden, Schwan, and Virehow; states that

  • all organisms are made of cells

  • all cells are produced by other living cells

  • cells are the basic units of life

• cells are the building blocks of all living organisms

types of cells

• all cells fall into one of two categories: prokaryotic cells and eukaryotic cells

• prokaryotic cells (prokaryotes): cells that do not have a nucleus or membrane binding their organelles together

  • eg. bacteria

• eukaryotic cells (eukaryotes): cells that have a nucleus and membrane-bound organelles

  • any organism that is not a prokaryote

  • can be singular or multicellular

  • plant cells are eukaryotes with chloroplasts, central vacuoles, and cell walls

  • animal cells are eukaryotes with centrioles and lysosomes

organelles (cell parts)

• cytoskeleton: a network of protein fibers with many functions

  • microtubules: long, hollow tubes used for cell shape, movement of organelles, manipulation of chromosomes during cellular division

• nucleus: contains the cell’s genetic information

  • DNA is contained in the nucleus and has the “instructions” for making proteins, it cannot leave the nucleus

  • chromatin: spread out form of DNA which condenses into tightly-coiled chromosomes before cellular division

  • RNA is used as a messenger because DNA can’t leave the nucleus

  • nucleolus: inside the nucleus, responsible for making ribosomes

• endoplasmic reticulum: an extensive network of folded membranes which produces the membranes of the cell and other organelles

  • can be rough or smooth

  • rough-- studded with ribosomes, looks lumpy under a microscope

  • smooth--detoxifies drugs and poisons, synthesizes lipids

organelles in the cytoplasm

• ribosomes: “factories” that make protein; made by the nucleolus and have two different subunits

  • ribosomes on the rough endoplasmic reticulum make proteins destined to be exported from the cell or imbedded into the cell membrane

  • ribosomes free in the cytoplasm make protein to be used within the cell, always imbedded into the cell membrane

• golgi apparatus: layered stacks of membrane enclosed spaces that process, sort, and ship out proteins; alter proteins and send them on their way

• vesicles: small bags from the endoplasmic reticulum used to transport proteins and substances to and from the golgi bodies

• mitochondria: the powerhouse of the cell, responsible for making ATP (energy) through the process of cellular respiration

• chloroplasts: found in plant cells, use CO2 and water to make sugar in photosynthesis

• vacuole: found in plant cells, a fluid-filled sac used for storage of water, food molecules, ions, and enzymes

  • central vacuole: found in plant cells, responsible for storing water, poisons, and some pigments of fruits and flowers; when it fills with water, it increases the cell’s turgor pressure

    • should have high turgor pressure (keeps cell standing upright rather than wilting)

  • contractile vacuole: found in protists, used to pump out excess water to prevent the cell from bursting

• lysosomes: contain digestive enzymes to break down food, and defend against bacteria and viruses; can also recycle cell parts

  • “suicide sacs”—programmed cell destruction

• centrioles: found in animal cells, organize microtubules to form cilia and flagella

  • cilia: microscopic hairs on the exterior surface of a cell; beat back and forth like oars for a boat, help move the cell and move materials around the cell

  • flagella: whiplike tail for movement of the cell

cell membrane

• cell membrane: selectively permeable substance which controls the passage of materials into or out of the cell

  • selectively permeable: allows some but not all materials to pass

• cholesterol: keeps the membrane more fluid

  • carbohydrates attached serve as identification tags so cells can distinguish one cell from another

the role of cells

• “building blocks” of organisms

  • every living being is built up of at least one cell; the human body contains trillions

• give structure to the human body and its organs

  • form bones and other organs that are critical to the structure of the human body

• process nutrients from food and convert them to energy (ATP)

  • through cellular respiration, we’re able to gain nutrients and energy from the food we consume

• carry out specialized functions

  • cells in each organ have a different set of functions from others, eg. fighting infections (white blood cells)