Chapter Three Exchanging Materials with the Environment

What is this picture about? What are two details observed in this picture? What is one very important idea represented in this picture?

Exchanged Materials What is the role of the cell membrane? The cell membrane regulates the passage of materials into and out of the cell. Single celled bacteria: Wall made of carbohydrates and proteins. A membrane made primarily of phospholipids.

Exchanged Materials Materials needed for life must enter the cell and certain materials must leave the cell … what are they?

Exchanged Materials Water CO2 and O2 Sodium, Magnesium, Calcium, Hydrogen, Chloride, Potassium Sugars, Amino Acids, Lipids Ammonia

Membrane as a Barrier Based on the picture – how is a cell membrane constructed? The membrane consists of two thin layers of phospholipids. Hydrophobic/ Hydrophilic? Nonpolar tails repel charged particles but allow fat-soluble molecules to pass.

Membrane as a Barrier What might determine if material can pass through the cell membrane? Polarity, size, and electric charge. Small gases (O2 and CO2) as well as small polar molecules (water and ethanol) pass freely.

Membrane as a Barrier How do charged ions and large polar molecules (glucose and a.a.’s) pass through the membrane? Transport proteins embedded in the membrane help polar molecules such as sugars and aa’s.

Membrane as a Barrier This diagram shows selective permeability. What does it mean to be selectively permeable? The cell membrane is selectively permeable. The outside of the cell membrane is involved in communication. Glycoproteins act as antennae.

What is this picture about? What are two details observed in this picture? What is one very important idea represented in this picture?

Diffusion and Osmosis Explain how the “concentration” or “density” of the particles in the picture affects their movement. The movement of molecules from high concentration to low concentration is diffusion.

Diffusion and Osmosis The first picture in this grouping has a high concentration gradient. Define concentration gradient. A difference in concentration across a distance is a concentration gradient. What happens at equilibrium? Explain what is happening with the purple dye.

Diffusion and Osmosis How is this picture an example of concentration gradient and diffusion?

Diffusion and Osmosis How is diffusion responsible for keeping this plant looking healthy? The diffusion of water down a concentration gradient is called osmosis.

Diffusion and Osmosis PROBLEM With the cytoplasm and organelles, an animal cell is about 98% water. What would happen to … an animal cell placed in distilled water (100% water)? an animal cell placed in a high salt solution (90% water)?

Diffusion and Osmosis What might affect the rate of diffusion? Steeper concentration gradient. Surface area.

Passive and Active Transport Cells may need concentrations inside that differ from simple diffusion. How might this happen? Passive transport involves diffusion without any input of energy. Active transport uses energy to move substances against the concentration gradient.

Passive and Active Transport What if a substance is too big to diffuse through the membrane? Facilitated diffusion is a type of passive transport involving membrane proteins as channels. Very large molecules move across the cell by way of endocytosis and exocytosis.

Gas Exchange in Water What is cell respiration, and what gases are exchanged? Cell respiration releases energy for metabolism; O 2 is used and CO 2 is released.

Gas Exchange in Water How do O 2 and CO 2 move across the membrane? O 2 and CO 2 must be dissolved in water for diffusion to take place. Consistency of the membrane?

Gas Exchange in Water Water environments contain small amounts of dissolved oxygen. Concentration gradient? As a result … surface area for gas exchange?

Gas Exchange in Water Fish gills have a large surface area made of many fine filaments. Filaments are composed of capillary rich disks. Water flows past, countercurrent to the blood flow – gases are exchanged efficiently.

Gas Exchange on Land Due to a moist gas exchange surface, land based organisms risk dehydration. How have organisms on land evolved to resolve this?

Gas Exchange on Land In insects, gas exchange occurs through branching air tubes called tracheae. Air flows in and out of tracheae through openings called spiracles. The spiracles can close to retain water.

Adaption to Life on Land Your nasal cavities moisten, warm and filter the air you breathe – why is that necessary? Air passes through the nose and mouth, past the pharynx and larynx, down the trachea and bronchus to the lungs.

Adaption to Life on Land The lungs contain millions of microscopic cavities for gas exchange called alveoli. If gas exchange occurs at the alveoli – what must they be like?

Adaption to Life on Land Thin Large Surface Area (two large parking spaces) Many Capillaries O 2 in and CO 2 out

Cystic Fibrosis Cystic Fibrosis is a genetic disorder resulting in coughs, lung infections and digestion difficulties. The absence of one aa in cystic fibrosis transmembrane conductance protein (CFTR) prevents chloride regulation.

Cystic Fibrosis This affects osmotic movement results in mucus build up. What affects can mucus build up have on the lungs and digestive tract?

Adaption to Life on Land How do plants prevent water loss during gas exchange? Plants have a waxy covering called the cuticle. Gases move into and out of the leaf through openings called stomates – regulated by guard cells.

Adaption to Life on Land The presence of water regulates the guard cells. How does water move up the stem of a plant? Transpiration