Cell Transport Section How can a cell separate itself from its environment and still allow material to enter and leave?

Passive Transport The movement of materials across the cell membrane without using energy is called passive transport. Types of passive transport include diffusion, facilitated diffusion, and osmosis.

1. Diffusion - the tendency of molecules to move from a higher concentration to a lower concentration until equilibrium is reached. Molecule 1 Molecule 2

Equilibrium- a condition in which the concentration of a substance is equal throughout space. Diffusion happens until the concentration of the molecules is even on both sides. NOTE: that doesn’t mean they stop moving!

Diffusion video In the cell: cell membrane keeps the cell’s internal conditions relatively constant by regulating the movement of molecules from one side of the membrane to the other side

2. Facilitated Diffusion Membrane proteins are used to transport molecules across the membrane –Larger molecules –Charged molecules Sodium (Na + ) Potassium (K + ) Chloride (Cl - ) Calcium (Ca +2 ) Nerve cells to send electrical signals in body, Muscle cells make your heat beat with the help of ions through your cells

Glucose (a larger molecule) enters and exits the cell through protein carriers This makes it easy for glucose to cross over the membrane

3. Osmosis (an example of facilitated diffusion) Diffusion of water through a selectively permeable membrane Water molecules have a tough time passing through the cell membrane, why? An aquaporin is a water channel protein

Osmosis Does this process require energy?

1. the barrier is permeable to water but not to sugar. 2. There is more “free water” on the left side because there is less glucose 4. Water will tend to move across the barrier until equilibrium is reached. 3. There is a net movement of water into the compartment containing the concentrated sugar solution. 5. the concentrations of water and sugar will be the same on both sides.

Osmosis Video The net movement in and out of the cell produces a force called osmotic pressure. Osmotic pressure can cause cells to shrink or swell

Hypertonic Solution with a higher concentration of solute and a lower concentration of water. Hyper = above

Hypotonic Solution with a lower solute concentration and a higher water concentration. Hypo = below

Isotonic Solutions of equal solute concentration. Isos = equal

With a partner discuss… What is the ideal environment for a plant cell? What is the ideal environment for an animal cell?

Effect on living animals Osmoregulation – control of water balance. –Animals must use this when exposed to hypertonic and hypotonic environments for survival. –Example – fresh water fish live in hypotonic environment use kidneys and gills to prevent excess water buildup in body.

Effect on living plant cells Most plants thrive in a hypotonic environment when cell wall is turgid and vacuole is full. Plants become wilted in isotonic environment. Plasmolysis – plant in hypertonic environment causes cell water loss, cell shrivels and the cell membrane pulls away from the cell wall and can kill the cell.

Moving on to Active transport!

The movement of material against its concentration gradient. This requires energy Substances move from an area of lower concentration to an area of higher concentration. Types of active transport include –Molecular transport –Bulk transport

Molecular Transport Active transport enables a cell to maintain internal concentrations of small molecules that differ from concentrations in its environment. Use protein pumps as opposed to protein _________.

Example of Active Molecular Transport Sodium Potassium Pump = Sodium = Potassium

Example of molecular transport The sodium potassium pump is an example of active transport because it –1. pumps molecules against their concentration gradient –2. uses energy to do this. Pumps 3 sodium ions (Na + ) out of the cell Pumps 2 potassium ions (K + ) into the cel Sodium Potassium Pump

Prevents Na + from accumulating in the cell –Na + continuously diffuses in the cell through protein channels –Increased concentration of Na + inside would cause water to move in. Why the pump is important

Bulk Transport Substances are toooooo large to even pass through a protein Endocytosis: cell ingests external molecules –Pinocytosis- “cell drinking” Cell takes in particles and extracellular fluid –Phagocytosis- “cell eating” Cell will engulf substance Digested by a lysosome

Exocytosis – process in which cells release molecules out of the cell from inside the cell The vesicle fuses with the cell membrane Cells in the pancreas make hormone insulin and secrete it into the blood stream by exocytosis. Endocytosis and exocytosis video Amoeba Feeds!

Section 7.4 Homeostasis and Cells

To maintain homeostasis, unicellular organisms grow, respond to the environment, transform energy, and reproduce. Unicellular organisms include both prokaryotes and eukaryotes.

Prokaryotes: bacteria remarkably adaptable and live almost everywhere—in the soil, on leaves, in the ocean, in the air, and even within the human body. Tuberculosis Actinomycetes

Single Celled Eukaryotes: algae, which contain chloroplasts and are found in oceans, lakes, and streams around the world, are single celled. Yeasts are also widespread. They play an important role in Breaking down complex nutrients, which makes them available for other organisms.

Multicellular Life Cells in multicellular organisms do not live on their own, they work together. Cells are specialized for different tasks and communicate with each other to maintain homeostasis. Specialized Pine Pollen Cells

Remember the levels of organization?

Cell Communication Cells communicate through chemical signaling. (receptor proteins!) Signals can speed up or slow down the activities of the cells and can cause a cell to change what it is doing.

Receptor protein Signal molecule Second messenger

Cell Junctions Cells attach to each other and hold together in tight formations. Protein in the cell membrane recognizes the cell.