Chapter 7 Notes Section 1
Cells Cells remained out of sight during most of human history until the invention of the first microscopes. It was not until the mid 1600s that scientists began to use microscopes to observe living things.
The History of the Cell 1.) In 1665 Robert Hooke used an early compound microscope to look at a thin slice of cork (plant material) It was composed of tiny empty chambers that he called cells. (Figure 7-1, pg 169) We now know that cells are not empty but contain living matter.
The History of the Cell 2.) In 1674 Anton van Leeuwenhoek used a single-lens microscope to observe pond water and other things. 3.) In 1838 Matthias Schleiden concluded that all plant are made up of cells. 4.) The following year Theodor Schwann stated that all animals were make of cells.
The History of the Cell 5.) In 1855 Rudolf Virchow concluded that new cells could be produced only from the division of existing cells. These numerous observations made it clear that cells are the basic units of life.
Cell Theory All living things are composed of cells. Cells are the basic units of structure and function in living things. New cells are produced from existing cells.
Exploring the Cell Today s researchers use microscopes and techniques more powerful than the pioneers of biology could have imagined. When using a light microscope the light limits the detail of images that can be made. Electron microscopes are capable of revealing details as much as 1000 times smaller than those visible with light microscopes.
Transmission electron microscopes (TEMs) make it possible to explore cell structures and large protein molecules. Cells and tissues must be cut first into thin slices before they can be examined. Scanning electron microscopes (SEMs) use a pencil like beam of electrons to scan over the surface of a specimen. Specimens do not have to be cut. A stunning three-dimensional image is produced
Only nonliving preserved cells and tissue can be visualized when using electron microscopes. In the 1990s researchers perfected a new class of microscopes that produce images by tracing the surfaces of samples with a fine probe. (Figure 7-3, page 172)
Types of Cells A typical cell ranges from 5 to 50 micrometers in diameter. Cells have two characteristics in common 1. surrounded by a barrier called a cell membrane. 2. at some point in their lives they contain the molecule that carries biological information (DNA). Cells fall into two broad categories, depending if they contain a nucleus: 1. Prokaryotes-Cells that do not contain nuclei 2. Eukaryotes-Cells that do contain nuclei
Cell membrane Cytoplasm Cell membrane Cytoplasm Nucleus Organelles
Prokaryotes Smaller and simpler than eukaryotic cells. Have genetic material that is not contained in a nucleus. Some contain internal membranes. Grow, reproduce, and respond to the environment. Ex. Bacteria
Eukaryotes Cells are generally larger and more complex than prokaryotic cells. Generally contain dozens of structures and internal membranes. Contain a nucleus in which their genetic material is separated from the rest of the cell. Ex. plants, animal, fungi, and protists.
Chapter 7 Notes Section 2
Eukaryotic Cells Eukaryotic cells are divided into two parts Nucleus Cytoplasm Portion outside the nucleus where organelles reside
Nucleus Contains most of the cell s DNA DNA is the code for making proteins Surrounded by a double membrane called the nuclear envelope Contains chromatin, which consists of DNA bound to protein Condenses during cell division to form chromosomes Nucleolus small dense region in nucleus where the assembly of ribosomes begins
Ribosomes Small particles of RNA and protein Are spread throughout the cell Are also attached to the rough endoplasmic reticulum Ribosomes are the site of protein synthesis
Endoplasmic Reticulum An internal membrane system Lipids, some proteins, and other materials are assembled here Rough ER has ribosomes attached to allow for protein synthesis Smooth ER has no ribosomes to allow for lipid synthesis
Golgi Apparatus Appears as a stack of membranes Acts like a postman It changes, sorts, and packages proteins and other materials Also delivers these packages to their final destination
Lysosomes Small organelles filled with enzymes Act as a cleaning crew They break down lipids, carbohydrates, and proteins so the cell can use them Also break down old organelles Also break down unneeded junk in cell such as bacteria
Vacuoles Saclike structures used for cell storage Stores water, salts, proteins, and carbohydrates
Mitochondria Powerhouse of the cell Converts chemical energy stored in food into a form that cells can use Has a double membrane One on the outside of organelle One folded up inside the organelle Contains its own DNA
Chloroplasts Powerhouse for a plant cell Converts energy from sun into chemical energy during process of photosynthesis Contains its own DNA
Cytoskeleton A network of protein filaments Helps cell retain its shape Also helps in cell movement Two of the filaments are microfilaments and microtubules Microtubules are very important in cell division As well as centrioles which help organize cell division
Chapter 7 Notes Section 3
Cell Boundries Cell Membrane- All cells are surrounded by this thin, flexible barrier. It regulates what enters and leaves the cell and provides protection and support. Contains protein molecules that are embedded in the lipid bilayer with carbohydrates attached. The Carbohydrates act like chemical identification cards.
Outside of cell Cell membrane Proteins Carbohydrate chains Inside of cell (cytoplasm) Protein channel Lipid bilayer
Cell Wall- Lie outside the cell membrane. Porous enough to allow water, oxygen, and carbon dioxide through. The main function is to provide support and protection for the cell. Plant cell walls are made mostly of cellulose
Measuring Concentration The cytoplasm contains a solution of many different substances in water. The concentration of a solution is the mass of solute in a given volume of solution (mass/volume). EX: If you had 12 g of salt in 6 L of water, what is the concentration.
Diffusion The process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Particles will move until equilibrium is reached. Does not require the cell to use energy.
Glucose molecules High Concentration Cell Membrane Low Concentration
Osmosis If a substance is able to diffuse across a membrane the membrane is said to be permeable to it. Most biological membranes are selectively permeable; some substances can pass across and others cannot. Osmosis is the diffusion of water through a selectively permeable membrane.
Osmosis When a solution has a higher solute concentration than the cell, it is said to be hypertonic. ( above strength ) When a solution has a lower solute concentration than the cell, it is said to be hypotonic. ( below strength ) When the concentration is the same inside and outside the cell, it is said to be isotonic. ( same strength )
Osmotic Pressure For organisms to survive, they must have a way to balance the intake and loss of water. Sometimes the cell takes on too much water and may burst. Large organisms are not in danger of this. Bacteria and plant cells are surrounded by a tough cell wall that tries to prevent this.
Facilitated Diffusion Sugar glucose molecules cannot pass through the membrane on their own. The cell membrane protein channels are said to facilitate (help) the diffusion of glucose across the membranes lipid bilayer.
Active Transport Materials move against a concentration difference. This process requires energy and transport protein pumps. Potassium, calcium and sodium move across this way.
Endocytosis The process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. Two types: Phagocytosis cell eating - Extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it. (Amoebas) Pinocytosis-Tiny pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell.
Exocytosis The membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell. EX: The removal of water by a contractile vacuole.
Chapter 7 Notes Section 4
Unicellular Organisms Only has one cell Can carry out all the essential functions of life Grow, reproduce, respond to the environment, etc.
Multicellular Organisms Made of many cells that do different tasks (cell specialization) Examples Muscle cells are packed with dense fibers that contract blood cells have special proteins that bind to oxygen to transport it around the body nerve cells have the ability to transmit messages throughout the body Plants also have specialized cells Examples: Guard Cells monitor the plants internal conditions
Levels of Organization Individual Cells Tissues Organs Organ Systems Organism
Tissues Groups of similar cells that perform a specific function Four main types Muscle Epithelial Nervous Connective
Organs Many groups of tissues working together to perform a specific function Example The stomach is an organ made up of smooth muscle tissue, epithelial tissue and nervous tissue
Organ Systems Many organs working together to perform a specific function Example Digestion includes the stomach, large and small intestines, esophagus, mouth, and pharynx, liver, and pancreas