Bellwork

1. Bellwork What is diffusion & osmosis? What is the concentration gradient direction for passive transport?

2. Ch. 4- Membrane Structure & Function Ch. 4.2 (part 2)- Permeability of the Plasma Membrane

3. Facilitated Transport: the passage of molecules like glucose and amino acids across the plasma membrane • Facilitated by their corresponding transport protein • Does not require energy • Molecules are moving down their concentration gradient Target #13- I can describe facilitated transport

4. Target #14- I can describe the role of carrier proteins in cellular transport • Larger molecules are able to enter the cell through the membrane because of carrier proteins • Each protein is designed for a certain type of molecule or ion • The carrier protein is believed to undergo a change in shape to move the molecule across the membran • Proteins involved in active transport are called pumps • They use energy to move substances against the concentration gradient

5. Target #15- I can explain active transport • Active Transport • Molecules or ions move through the plasma membrane • Accumulates on either side of the cell membrane • Must move up the concentration gradient • From areas of lower concentration to higher concentration • Requires energy to complete • In the form of ATP ( the energy molecule)

6. Target #16- I can describe a sodium potassium pump • Sodium-Potassium Pump • Proteins transport Na+ and K+ ions (sodium and potassium) up the concentration gradient • In animal cells, Na+ needs to be higher outside the cell and K+ needs to be higher inside the cell • Transport proteins help maintain this balance

7. Target #17- I can identify the steps of a cycle in the sodium-Potassium Pump

8. Target #18- I can describe what how large molecules are transported • Molecules that are too large, like polypeptides, polysaccharides, and nucleotides, to enter the cell via diffusion enter or exit through vesicle formation • Called membrane assisted transport • The membrane is needed to form a vesicle • Requires an expenditure of energy • Keeps the molecule from mixing with other molecules within the cytoplasm

9. Target #19- I can explain Exocytosis • Exocytosis • A vessicle fuses with the plasma membrane • Ex: hormones, neurotransmitters, and digestive enzymes • The Golgi apparatus produces the vesicles that carry these molecules out to the membrane • Process naturally enlarges the plasma membrane • Considered a part of natural cell growth • Can be regulated based on the needs of the body

10. Endocytosis • Cells take in substances by vesicle formation • A portion of the plasma membrane enfolds to envelope an incoming substance • The membrane pinches off to form an intracellular vesicle • Occurs in one of three ways • Phagocytosis: transports large substances like viruses • Pinocytosis: transports small substances like macromolecules • Receptor-Mediated endocytosis: special form of pinocytosis Target #20- I can explain Endocytosis

11. Target #21- I can differentiate between the types of endocytosis • Phagocytosis • Common in unicellular organisms • White blood cells do this when dealing with viruses • Vesicle formed fuses with a lysosome to digest/break down viral material • Pinocytosis • Occurs when vesicles form around a liquid or very small particles • Ingestion of substances • Ex: use in red blood cells, kidneys, or intestines • Occurs continuously

12. Target #21 Cont. • Receptor-Mediated Endocytosis • A form of pinocytosis • Uses a receptor protein shaped specifically for the molecule it is carrying • Ex: vitamins, peptide hormones, or lipoprotein • Found in one location in the plasma membrane • Called a coated pit • The vesicle becomes uncoated and my fuse with a lysosome • when empty, used vesicles fuse with the plasma membrane, and the receptors return to their former location • Selective and much more efficient than ordinary pinocytosis • involved in the uptake, transfer, and exchange of substances between cells