The Cell

The history of the Cell Theory  Before microscopes were invented, people believed that diseases were caused by curses and supernatural spirits  As scientists began using microscopes, they quickly realized they were entering a new world- one of microorganisms  Microscopes enables scientists to view and study cells, the basic units of living organisms

Development of Light Microscopes  The first person to record looking at water under a microscope was Anton van Leeuwenhoek  The microscope van Leeuwenhoek used is considered a simple light microscope because it contained one lens and used natural light to view objects  Compound light microscopes use a series of lenses to magnify objects in steps  These microscopes can magnify objects to 1500 times

The Cell Theory  Robert Hooke was an English scientist who lived at the same time was van Leeuwenhoek  Hooke used a compound light microscope to study cork, the dead cells of oak bark  Cells are the basic building blocks of all living cells

The Cell Theory is Made Up of Three Main Ideas  All organisms are composed of one or more cells  The cell is the basic unit of structure and function of organisms  All cells come from preexisting cells

Three Scientists Contributed to the Cell Theory  Schleiden: Plants are made of one or more cells  Virchow: New cells are produced from the division of old cells  Schwann: Animals are made of cells

Development of Electron Microscopes  The electron microscope was invented in the 1940’s  This microscope uses a beam of electrons to magnify structures up to 500,000 times their actual size  There are two basic types of electron microscopes  The scanning electron microscope scans the surface of cells to learn three dimensional shape  The transmission electron microscope allows scientists to study the structure contained within a cell

Two Basic Cell Types  Prokaryotic Cells  Cells that do not contain internal membrane-bound structures and do not have a nucleus  Organisms with these cells are called unicellular, for example bacteria  They still carry out all of life's activities such as respiration, cell reproduction, growth, etc.  Eukaryotic  Cells containing membrane-bound structures and a nucleus  Organisms with these cells can be unicellular or multicellular; plan or animal  Organisms that are multi-cellular have specialization in their cells

Eukaryotic Cell Structures: Organelles  The membrane-bound structures within eukaryotic cells  Each “little organ” has a specific function that contributes to cell survival  Separation of organelles into distinct compartments benefits the eukaryotic cells

Biologists divide the cells into two major parts  The nucleus is the central membrane-organelle that manages cellular functions  Everything between the cell membrane and the nucleus is called the cytoplasm (cell goo), where the rest of the organelles are

Nucleus  Nuclear Envelope- Double layered membrane surrounding the nucleus, contains small pores  Nuclear Pores- Holes in the envelope that allows for transport of materials in an out of the nucleus  Chromatin- Grainy material visible in the nucleus, made of DNA tightly coiled around proteins  Chromosomes- Threadlike structures within the nucleus containing the genetic information that is passed from one generation of cells to the next  Nucleolus- Dense material in nucleus; makes ribosomes which make proteins

Ribosomes  Ribosomes are made in the nucleolus out of RNA and proteins  They travel in and out of the nucleolus through the nuclear pores  Ribosomes are small particles within the cell on which proteins are assembled  The can be free (found in the cytoplasm), or attached to the rough endoplasmic reticulum

Endoplasmic Reticulum  The endoplasmic reticulum (ER) is responsible to assembly, transport, and storage of molecules within a cell  There are two types of ER  Rough ER- Contains ribosomes and makes proteins  Smooth ER- Lacks ribosomes; has enzymes that make membrane lipids and detoxifies drugs  Liver cells contain many smooth ER for detoxification

Golgi Apparatus  Stacks of membranes in the cell that modifies, sorts, and packages proteins from the ER (UPS of cells)  The golgi apparatus is like a customization shop where finishing touch's are added to proteins

Lysosomes  Organelles that contain digestive enzymes  Digest excess or worn out organelles, food particles, and engulfed viruses or bacteria  Are the clean up crew of the cell  Tay-Sachs disease is causes by excess lipid accumulation on the brain. The cause has been traced to lysosomes that failed to function properly

Vacuoles  A membrane-bound space used for temporary storage materials (water, salts, proteins, and carbohydrates)  Plant cells have much larger vacuoles to be able to stand up rights vs. animal cells  Paramecium have contractile vacuole that pumps excess water of of the cell, which is homeostasis

Mitochondria  Membrane-bound organelles in plant and animal cells that transform energy for the cell  A mitochondria has a highly folded inner membrane  The fold increase the surface area of the mitochondria of cells  Cellular respiration takes place in the mitochondria of cells  Cellular respiration in the process that converts chemical energy stored in food into ATP energy fro the cell to use  Muscles cells (needed for movement) contain a large number of mitochondria for energy production

Chloroplasts  Found in cells of plants and some protists  Organelles that capture light energy and produce glucose to store for a later time  Photosynthesis takes place in chloroplasts  Contain green pigment called chlorophyll  Chlorophyll traps lights energy and gives leaves and stems their green color  Chloroplasts act like a solar power plant

Cytoskeleton  Cells have a support structure called the cytoskeleton within the cytoplasm  It is a network of proteins that help maintain cellular shape and movement  Is composed of microtubules ad microfilaments  Microtubules are thin, hollow cylinders made of protein that maintain cell shape  Microfilaments are thin solid protein fibers that help cells more (amoeba)

Centrioles  Made of microtubules  One of two tiny protein structures located in the cytoplasm of animal cells near the nuclear envelope  Help to organize cell division (helps split cells in two)  Only found in animal cells

Movement: Cilia and Flagella  Some cells surfaces have cilia and flagella, which are structures that aid in locomotion or feeding  Cilia are short, numerous hair like projections that move in a wave like motion  Flagella are long projectiles that move in a whip like motion  Cilia and flagella are the major means of locomotion in unicellular organisms

The Plasma/ Cell Membrane  All living cells must maintain a balance regardless of internal and external conditions. Survival depends on the cell’s ability to maintain the proper conditions within itself  The plasma membranes job is to:  Allow a steady supply of glucose, amino acids, and lipids to come into the cell no matter what the external conditions are  Remove excess amount of these nutrients when levels get so high that they are harmful  Allow waste and other products to leave the cell  Selective permeability is a process used to maintain homeostasis in which the plasma/cell membrane allows some molecules into the cell while keeping others out

Structure of the Plasma Membrane  The plasma membrane is composed of two layers of phospholipids back-to-back called a bilayer  Phospholipids are lipids with a phosphate attached to them  The phospholipids are lipids with a phosphate attached to them  The phospholipids in a plasma membrane have a glycerol backbone, two fatty acid chains, and a phosphate group  The phosphates hydrophilic, and the lipid hydrophobic

Make Up of the Phospholipid Bilayer  The phosphate group is critical for the formation and function of the plasma membrane  The fluid mosaic model describes the plasma membrane as a flexible boundary of a cell  The phospholipids move within the membrane

Other Components of the Plasma Membrane  Proteins are embedded in the phospholipid bilayer  Some proteins form channels for mumps to move material across the membrane  Carbohydrates attached to proteins. They act as signals or identification cards, allowing cell recognition  Cholesterol plays the important role of preventing the patty acid chains of the phospholipids from sticking together

Cell Walls  The cell was is a fairly rigid structure located outside the plasma membrane that provides additional support and protection  Found in plant cells, (protists) algae, and some prokaryotes, but not in animal cells  Plant cells walls are made of cellulose (carb)