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Bellwork

This text explores key concepts in cellular transport, including diffusion, osmosis, and the roles of carrier proteins in facilitated transport. It outlines how molecules like glucose and amino acids pass through the plasma membrane without energy, while larger molecules utilize vesicle formation in processes like endocytosis and exocytosis. The sodium-potassium pump, a crucial active transport mechanism, is also discussed, detailing how it maintains the necessary ion balance in animal cells. Understanding these processes is essential for grasping cellular function and homeostasis.

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Bellwork

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  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

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