Chapter 4

 All living organisms are made up of cells  Cells are the basic units of structure and function in living organisms.  All cells come from cells that existed before them by cellular reproduction.  Schwann, Schleiden and Virchow are credited with coming up with the basics of the cell theory 

 Every cell has the following main characteristics: ◦ Plasma membrane covering ◦ Cytoplasm ◦ Their genes are made of DNA ◦ Ribosomes are tiny organelles that assemble proteins

 Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen.  This microscope is the only type that can examine living organisms, it is cheap and easy to use.  Disadvantage: limited magnification, cannot show too many details of cells.  See handout for the parts of the microscope – you must know it.  – images of the human body under a microscope

 Two important characteristics that determine the quality of a light microscope: ◦ Magnification – an increase in the apparent size of an object. We calculate magnification by the following: Magnification of eyepiece x magnification of objective = total magnifying power Resolution – the measure of clarity of an image. As the magnification increases, the resolution of the image decreases.

 Some microscopes use beams of electrons for magnification instead of light – electron microscopes  Scanning electron microscope (SEM) – used to study the detailed architecture of the surface of the object. Forms a 3D image, but does not show the inside of the object.  Transmission electron microscope (TEM) – used to provide a detailed 2D image of the inside structure of the object that is viewed.

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  Cells are microscopic, they are visible only with light microscopes. Most of their size ranges from µm.  The cells are small, because they have to be able to carry materials from one side of the cell to the next in a short period of time.  Cells must have a large enough surface area to be able to take in nutrients and oxygen and release waste quickly.

 Prokaryotic cells – small cells (about 1-10 µm) that do not have a nucleus and organelles that are covered with membranes  Prokaryotic cells are found in Bacteria and Archaea (two main domains of life).

 Nucleoid region – part of the prokaryotic cell where the DNA is found  Cell membrane – innermost covering of the cell  Cell wall – made up of a special mix of polysaccharides and proteins (antibiotics break it down)  Capsule – outside of the cell wall, protective covering (not all bacteria have it)  Flagella (sing. Flagellum) – moves bacteria  Pili – used to stick them to surfaces and for conjugation (exchange of genetic materials between bacteria)

 Cytoplasm – dissolves substances and holds organelles  Ribosomes – organelles that make proteins in the cytoplasm   – bacteria song

 Protists, Fungi, Plants, and Animals  Have nucleus and organelles that are surrounded by phospholipid membranes (membrane-bound organelles)  Much larger and more complex than prokaryotic cells. ( µm)  Reproduce sexually and asexually 

 Nucleus ◦ Control center of cell; contains most of the cell’s DNA  Nucleolus ◦ Location where ribosomes are synthesized, made up of DNA, RNA and proteins  Nuclear envelope ◦ Protects the DNA in the nucleus, nuclear pores allow the exchange of materials. ◦ Amazing cells:

 Ribosomes ◦ Protein synthesis – mushroom-shaped organelle that is made up of RNA and proteins  Rough ER ◦ Comprised of a network of tubes and flattened sacs. ◦ Continuous with plasma membrane and nuclear membrane and made up of the same material ◦ Site of protein synthesis (consists of ribosomes) and protein folding (this is where many proteins get their secondary and tertiary structures).

 Smooth ER ◦ Site of lipid and carbohydrate metabolism ◦ No ribosomes ◦ Membrane structure, so it is also made up of phospholipids and proteins ◦ Detoxification  Golgi Apparatus ◦ Connected with ER; flattened disc-shaped sacs, stacked one on top of the other ◦ Modification, storage, and packaging of proteins. ◦ “Tags” proteins so they go to the correct destination ◦ “The mailroom of the cell”

Amazing cells:

 Lysosomes (in animal cells and some protists) ◦ Digestion of nutrients, bacteria, and damaged organelles; destruction of certain cells during embryonic development ◦ Contain hydrolytic enzymes  Peroxisomes ◦ Diverse metabolic processes break down H ions into hydrogen peroxide ◦ Detoxification  Vacuoles ◦ Digestion (like lysosomes); storage of chemicals, cell enlargement; water balance, really large in older plant cells

 Chloroplasts ◦ Conversion of light energy to chemical energy of sugars (site of photosynthesis) ◦ Double membrane structure You must be able to draw and label the parts of chloroplasts  Mitochondria ◦ Conversion of chemical energy of food to chemical energy – cellular respiration ◦ Bound by double membrane You must be able to draw and label the parts of mitochondria

 Cytoskeleton (including cilia, flagella, and centrioles in animal cells) ◦ Maintenance of cell shape; anchorage for organelles; movement of organelles within cells; cell movement; mechanical transmission of signals from exterior of cell to interior. Cilia and flagella move the cell or move substances on the cell. ◦ Centrioles: important for cell division  Cell walls (in plants, fungi, and protists) ◦ Maintenance of cell shape and skeletal support; surface protection; binding of cells in tissues ◦ Made up of cellulose in plants, chitin in fungi and different types of materials in prokaryotes.

0O5Yhttp:// 0O5Y – cell animation