Cell Membranes and Exchange of Materials across the membrane!

Diffusion

Molecules move from an area of higher concentration to an area of lower concentration until the concentration is the same throughout. In (a), a crystal of potassium permanganate (KMnO4) was dropped into a glass of water. The molecules diffuse through the water (b) until they are evenly distributed throughout (c).

A Semipermeable Membrane• Molecules that move in and out of a cell

freely:– WATER, OXYGEN, AND CARBON

DIOXIDE, AMINO ACIDS

– Why?• They are small molecules

• Large molecules like PROTEINS AND CARBOHYDRATES CANNOT move across the membrane freely

• The Cell Membrane is SEMIPERMEABLE (SELECTIVELY PERMEABLE)– ONLY ALLOWS CERTAIN MOLECULES

TO PASS THROUGH

Osmosis• The diffusion of water

• Passive Transport

• Water diffuses from an area of high water concentration to an area of low water concentration

Cells respond to their environment!

What process occurred that caused these red blood cells to change shape?

3.3 Diffusion and Osmosis How Cells Exchange Materials

Initially the cells are in a solution with the same concentration of dissolved material as is found inside the cells. This is called an isosmotic solution. The animal cell can survive only fairly small variations from this concentration.

Elodea

Red Onion

Parameciause a contractile vacuole to rid of excess water

Exocytosis

             

Endocytosis

A type of active transport

Examples of endocytosis

Phagocytosis – brings in “food”

Pinocytosis – cell brings in Water

CFTR Protein and Cystic Fibrosis

Exchange in Multicellular OrganismsGas Exchange on LAND and water

Gas Exchange in Water

Water has oxygen in it, but not in high concentrations like in air

Organisms in water have adaptations to removing limited oxygen in water

Type of adapations?

Large surface area!

Gas Exchange in Water

Gas Exchange on Land

Gas Exchange in Humans

Oxygen is obtained from inhaled air. The air passes down the trachea (windpipe) and enters the bronchi at the entrance to the lungs. Each bronchus divides into smaller tubes called bronchioles. At the end of the each bronchiole branch are sets of air sacs. These air sacs are called alveoli.

Website link

This scanning electron micrographs shows the organization of the pulmonary acinus. This micrograph is of a cast of two terminal bronchioles, the short respiratory, or transitional, bronchioles and all of the alveolar air spaces supplied by those bronchioles.

An average adult has about 600 million alveoli,giving a total surface area of about 100m². The walls of the alveoli are composed of a single layer of flattened epithelial cells, as are the walls of the capillaries, so gases need to diffuse through just two thin cells. Water diffuses from the alveoli cells into the alveoli so that they are constantly moist. Oxygen dissolves in this water before diffusing through the cells into the blood, where it is taken up by haemoglobin in the red blood cells.

Waste removal in organisms

• What are the 3 types of nitrogen waste?– Ammonia– Urea– Uric Acid

– What kind of organisms excrete each? Where would these organisms each live?

Waste Removal in Humans – The Excretory System

The kidney is made of nephrons

Each kidney is bean-shaped and about the size of an adult's fist.

The kidneys are located below the ribs and toward the back.

They contain nearly 40 miles of tubes, most of them tiny, that process some 100 gallons of blood each day.

The kidneys filter and clean the blood, and they produce urine from excess water and dissolved solids.

What Causes Kidney Stones? Kidney stones are hardened crystal clumps that can develop in the urinary system. They usually form because there is a breakdown in the balance of liquids and dissolved solids in the urine. The kidneys must keep the right amount of water in the body while they remove materials that the body cannot use. If this balance is disturbed, the urine can become overloaded with substances (usually small crystals) that won't dissolve in water. Crystals begin to stick together and slowly add layer upon layer to form a stone. A kidney stone may grow for months or even years before it causes a problem.

Kidney stones don't all look the same. The color depends on what chemicals are in it. Most are yellow or brown, but they can be tan, gold, or black. Stones can be round, jagged, or even have branches. They vary in size from specks to pebbles to stones as big as golf balls.

                                                                        

Who Gets Kidney Stones? Anyone can get kidney stones, but some people are more likely to develop stones than others. Typically, a person with a kidney stone is a man 20 to 60 years old. Although four out of five kidney stone sufferers are men, women also get kidney stones. Often, there is a family history of kidney stones. Chronic dehydration (lack of body water) can lead to kidney stones. Very hot weather, heavy sweating, or too little fluid intake contribute to the formation of kidney stones. People who work outdoors in hot weather and who do not drink enough fluids may increase their risk of getting stones.

Website on kidney stones

Feedback Regulation

(pump ions out using ATP energy; inside becomes negatively charged)