Aim: How has the electron microscope enabled scientists to see the unseen? Look how far we have come in 400 years.

Living Environment HW#10 Due Friday 10/8 Read text pages 184-189 Pg 186 word origins – answer question Pg 186 draw diagram –answer predicting question under fig. 7-18 Read – How does penicillin work? Summarize and come up with two questions for further research.

Differences between compound, and electron microscopes Compound microscope uses light and lenses to focus. The electron microscope uses electrons and magnets to focus. The image cannot be looked at directly with the naked eye.

Difference in images Electron microscopes have enabled us to learn a lot about the cell organelles. Have students compare the images

The cell membrane helps the cell maintain Homeostasis Lipid bilayer Work with your partner: what does homeostasis mean?

Structure of the cell membrane Outside of cell Carbohydrate proteins Cell membrane In addition to lipids, most cell membranes contain protein molecules that run through the lipid bilayer. Carbohydrate chains are attached. There are so many molecules attached to the cell membrane that scientists call the membrane a “mosaic” of different molecules. The cell membrane serves a special function because there are certain substances that pass through the membrane. Talk with your group and make a list of substances that can pass through a cell membrane. Amino acids, simple sugars, oxygen, carbon dioxide Inside of cell (cytoplasm) Protein channel Lipid bilayer

antibiotics that interfere with cell wall synthesis have a high specificity and are low in toxicity to host organisms A bactericidal antibiotic kills the bacteria. Penicillin is a bactericidal. A bactericidal usually either interferes with the formation of the bacterium's cell wall or its cell contents.

Tagged carbohydrate on the surface of the cell membrane Sugars light up the cells in this jaw of a 3-day-old zebrafish embryo and highlight a scientific first: labeling and tracking the movements of sugar chains called glycans in a living organism. Here, recently produced glycans (red) are on the cell surface while those made earlier in development (green) have migrated into the cells. In some areas, old and new glycans mingle (yellow). A better understanding of such traffic patterns could shed light on how organisms develop and may uncover markers for disease, such as cancer. Courtesy of chemical biologist Carolyn Bertozzi, University of California, Berkeley.

Aim: How do substances diffuse through a membrane? Things that move into a cell… Things that move out of a cell… Amino acids, monosaccharides (sugar), glycerol and fatty acids, elements, Ca, Iron, Phosperous, oxygen, carbon dioxide and some compounds that the cell makes for secretion (hormones, etc)

Diffusion – molecules of a substance move from areas of higher concentration to areas of lower concentration Water molecules Osmosis is the diffusion of water through a selectively permeable membrane. In this illustration, there is a higher concentration of water outside the cell that inside it. As a result, water molecules move across the membrane into the cell. Diffusion. This is a good example of how certain molecules, such as oxygen, simply move directly through a membrane in response to the high-to-low concentration gradient. As an example, oxygen diffuses out of the lungs and into the blood for transport to all of the cells. Sugar molecules

Facilitated diffusion Outside of cell Carbohydrate proteins Cell membrane In addition to lipids, most cell membranes contain protein molecules that run through the lipid bilayer. Carbohydrate chains are attached. Facilitated Diffusion. This is a special type of diffusion that is useful because substances are sometimes too large to move freely through a membrane, or they need to move against a concentration gradient so transport proteins embedded in the membrane assist with the passage. In most cases, the transport protein creates a chemical channel for the passage of a specific substance. Because no energy is expended, the rate of facilitated diffusion depends on the number of transport proteins embedded in the membrane. As an example, glucose is moved by a glucose-transporter protein as it passes through the red blood cell into a body cell. Inside of cell (cytoplasm) Protein channel Lipid bilayer

Active Transport requires energy A molecule is moving across the cell membrane from an area of low concentration with the help of a transport protein A In picture A and B, locate the area of low concentration. Locate the area of high concentration. Scientists think that the transported molecules are somehow squeezed through the transport proteins, as the proteins change their configuration to accommodate their riders. Sometimes substances must be pumped against a concentration gradient, such as the sodium ions (Na+) and potassium ions (K+) pump. So a transport protein and energy, usually adenosine triphosphate (ATP), the energy-rich compound, are needed to push the ions against the gradient. In the case of sodium and potassium ions, maintaining sodium outside and potassium inside the cell is crucial to the functioning of muscles and nerves B

Selectivity of transport across a membrane refers to the shape of the substance passing through, certain substances can pass through and some cannot. Role of insulin in the diffusion of sugar across a membrane.

Large molecules pass through the cell membrane by endocytosis and exocytosis http://www.phschool.com/science/biology_place/biocoach/biomembrane2/cytosis.html

What do the different shapes represent?

Plasma Membranes are Selectively Permeable Do Now Summary Plasma Membranes are Selectively Permeable What does this mean? What are the ways in which substances can pass through a cell membrane Cell membranes are selectively permeable. Some solutes cross the membrane freely, some cross with assistance, and others do not cross at all. http://www.phschool.com/science/biology_place/biocoach/biomembrane1/permeability.html