Microscope and CellsChapter 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

http://www.youtube.com/watch?v=AeygTtDx2W8

I. 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

Antone von Leeuwenhoek assembled the first microscope that was useful for scientific research.

Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen.

See handout for the parts of the microscope – you must know it. http://www.youtube.com/watch?v=3emmlXcV-MU&feature=related

II. The Compound Light 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.

III. Electron Microscopes

http://www.mos.org/sln/sem/mascara.gif

http://www.cellsalive.com/howbig.htm

Cells are microscopic, they are visible only with light microscopes. Most of their size ranges from 1-100 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.

III. The Size of Cells

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).

IV. Prokaryotic Cells

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

http://www.ted.com/talks/lang/eng/bonnie_bassler_on_how_bacteria_communicate.html

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.

Reproduce sexually and asexually http://www.youtube.com/watch?v=Y3u_GDIj7RI&feature=related

V. Eukaryotic Cells

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 pore◦ Allows RNA to move in and out of nucleus◦ http://www.youtube.com/watch?v=CQNvOI-zV_E&feature=related

◦ Amazing cells: http://learn.genetics.utah.edu/content/begin/cells/insideacell/

VI. Eukaryotic OrganellesGeneral Function: Manufacturing

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

◦ 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 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”

Eukaryotic OrganellesGeneral Function: Manufacturing

Lysosomes (in animal cells and some protists)◦ Digestion of nutrients, bacteria, and damaged

organelles; destruction of certain cells during embryonic development

Peroxisomes◦ Diverse metabolic processes with breakdown of

H2O2 by-product Vacuoles

◦ Digestion (like lysosomes); storage of chemicals, cell enlargement; water balance, really large in older plant cells

Eukaryotic OrganellesGeneral Function: Breakdown

Chloroplasts◦ Conversion of light energy to chemical energy of

sugars (site of photosynthesis)◦ Double membrane structureYou must be able to draw and label the parts of

chloroplasts Mitochondria

◦ Conversion of chemical energy of food to chemical energy of ATP

◦ “Power House” of cell◦ Bound by double membraneYou must be able to draw and label the parts of

mitochondria

Eukaryotic Organelles: Energy Processing

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.

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.

Eukaryotic OrganellesGeneral Function: Support, Movement, and Communication