Homeostasis, Transport & The Cell Membrane

1. Homeostasis, Transport & The Cell Membrane Chapter 4-2 (pg 73 – 75) Chapter 5

2. Unit 5:Lecture 1 • Topic: • The Cell Membrane • Covers: • Chapter 5, pages 95 - 96 • Chapter 4, pages 73 - 75

3. The Cell Membrane • The chemistry of living organisms involves the study of solutions. • A large portion of our body is water, and the chemical reactions of life occur in aqueous(watery) solutions. • Nutrients move through the watery matrix of your blood to deliver the nutrients to cells. • Cell membranes help organisms by controlling what substances may enter or leave the cells. • Known as Selectively Permeable or Semipermeable • Some substances can cross the cell membrane without any input of energy, whereas other materials need ATP to help cross through the membrane.

4. The Cell Membrane • It’s Selectively Permeable… HOW DOES IT DO THAT? • Because of the membrane’s structure • Cell membrane is a PHOSPHOLIPID BILAYER • BILAYER- 2 LAYERS • PHOSPHOLIPID- 2 PARTS • 1. Phosphate head • 2. Lipid tail

5. 1. Phosphate head - Outer part of the bilayer • HYDROPHILIC- "Water loving” • 2. Lipid Tail - Middle part of the bilayer • HYDROPHOBIC- "Water hating"

6. The phospholipids are not attached to one another, enabling the membrane to have “fluid” like properties • Because of the lipid bilayer’s chemical properties, not all types of molecules can cross through the membrane • Some substances can cross through on their own • Small, uncharged particles can squeeze between phospholipids and can cross though the lipid layer • Some substances need assistance to cross through the membrane • Large molecules cannot fit between phospholipids • Charged particles (ions) cannot cross through the lipid layer

8. Other Parts of the Cell Membrane • 1. CHOLESTEROL(type of lipid) • Function: Helps to make the membrane "fluid", not rigid • Location: Part of the the bilayer • 2. PERIPHERAL PROTEINS • Function: Helps to keep the shape of the cell • Location: Inner layer of cell membrane, connected to fibers of the cytoskeleton

9. Other Parts of the Cell Membrane • 3. INTEGRAL PROTEINS • Function: Channel for molecules to come into the cell • Location: Embedded in the membrane (goes through membrane, from one side to the other) • Some integral proteins have carbohydrates attached • Known as Glycoprotein

10. Other Parts of the Cell Membrane •  4. GLYCOPROTEINS • Location: Integral protein with a carbohydrate attached • Carbohydrate (glycogen) sticks out of the cell, on outside of cell membrane • Functions: • Used in cell recognition • Different cell types have different shaped glycoproteins attached • Used as a cell receptor • Glycoprotein accepts proteins/substances meant for that specific cell type

11. End Lecture 1

12. Unit 5:Lecture 2 • Topics: • Transport across membranes • Passive Transport (Diffusion, Osmosis) • Covers: • Chapter 5, pages 95 – 99

13. Transport AcrossCell Membrane • Many materials cross through the cell membrane (enter cell or leave cell) • The types of transport are grouped into two categories: • Passive Transport • Active Transport • The type of transport used to move the material depends on the concentration gradient as well as the type of molecule being transported

14. CONCENTRATION GRADIENT – when the solutions on either side of the membrane do not have the same concentration of solutes (one more concentrated than the other) • When the concentration is equal throughout the space/solution, the solution is said to be in EQUILIBRIUM • Due to kinetic energy, molecules are in constant motion,  even when the solution is in a state of equilibrium • In the cell, molecules will diffuse in & out of the cell even when the cell is in equilibrium with its surroundings

15. Types of Transport:Passive • Passive Transportoccurs naturally due to kinetic energy, so it does not require any additional energy from the cell. • In passive transport, the molecules are said to be moving "down the concentration gradient" 
because the molecules are moving to an area with a lower concentration.

17.  Types of Passive Transport: • Diffusion • Osmosis • Facilitated Diffusion • Ion Channel • DIFFUSION: Movement of molecules from an area of high concentration to an area of lower concentration • EXAMPLES:Food coloring in water, Solute added to a solvent

18. Types of Passive Transport: • Diffusion • Osmosis • Facilitated Diffusion • Ion Channel OSMOSIS • Type of Passive Transport driven by kinetic energy • OSMOSISis the diffusion of water! • Water molecules are moving from an area of high concentration (of water) to an area of low concentration (of water) • If water is diffusing into or out of a cell, the water  molecules will be crossing through the cell  membrane • Cell is trying to reach EQULIBRIUM with its surrounding environment

19. HYPOTONIC SOLUTION • External solution has higher concentration of water than inside the cell • Water moves into the cell • Cell can burst! HYPERTONIC SOLUTION • External solution has a lower concentration of water than inside the cell • Water moves out of the cell • Cell shrivels up! ISOTONIC SOLUTION • Concentration of water inside and outside the cell is and inside the cell are equal • Cell is in equilibrium with its surrounding environment!

20. How cells deal with osmosis... HYPOTONIC SOLUTION • In plants - vacuole fills with water creating turgor pressure • Helps to support plant cell • In unicellular freshwater organisms - water constantly entering cell, these organisms must continuously pump the water out of the cell • Contractile Vacuole - Organelle that removes water • In Red Blood Cells – water fills up the RBC & the cell can burst! • Known as CYTOLYSIS HYPERTONIC SOLUTION • In plants - when water leaves cell, turgor pressure reduced and plants become wilted, Known as PLASMOLYSIS • In Red Blood Cells - cells can't compensate for extreme changes in concentration, so cells would shrivel • Known as CRENATION

22. End Lecture 2

23. Unit 5Lecture 3 • Topics: • Transport across membranes • Passive Transport (Facilitated Diffusion, Ion Channel) • Active Transport • Covers: • Chapter 5, pages 99 – 104

24.  Types of Passive Transport: • Diffusion • Osmosis • Facilitated Diffusion • Ion Channel FACILITATED DIFFUSION • Type of passive transport that is driven by kinetic energy • Moving molecules from high to low concentration (“Down the gradient”) • Transports molecules that can not diffuse on their own • EX. - too big, not soluble in lipids, glucose, polysaccharides • These molecules are assisted across the membrane by a type of integral protein known as a CARRIER PROTEIN • Many types of carrier proteins because each carrier protein can only assist ONE type of molecule •  * REMEMBER - Form Fits Function! *

25.  Types of Passive Transport: • Diffusion • Osmosis • Facilitated Diffusion • Ion Channel ION CHANNEL * REMEMBER - An ION is an atom or molecule with a charge • Type of passive transport that is driven by kinetic energy • Moving molecules from high to low concentration (“Down the gradient”) • Ions are not soluble in lipids, so ions cannot cross through the lipid bilayer (cell membrane) on their own • Ions cross through the cell membrane by traveling through a type of integral protein known as an ION CHANNEL • Many types of ion channels because each ion channel can only assist ONE kind of ion across the membrane •  Sodium (Na+)  - Potassium (K+) •  Calcium (Ca++)  - Chlorine (Cl-)

26. ACTIVE TRANSPORT • Unlike passive transport, ACTIVE TRANSPORT requires the cell to use energy to move the molecules across the membrane • Energy supplied by the cell's mitochondria in the form of ATP • Active transport moves molecules from an area of lower concentration to an area of higher concentration • Molecules moving "up the gradient” or “against the gradient”, solution moving away from equilibrium

27.  Types of Active Transport: • Membrane Pumps (Sodium-Potassium) • Endocytosis • Exocytosis SODIUM - POTASSIUM PUMP • Type of Active Transport, requires ATP to occur • Membrane Pumps require a special type of carrier proteins (a type of integral protein) • Membrane Pumps transport molecules from an area of low concentration to an area of high concentration • In the Sodium-Potassium Pump, sodium ions (Na+) are pumped out of the cell and potassium ions (K+) are pumped into the cell • 3 sodium leave cell for every 2 potassium that enter • Cell needs to have a high concentration of Na+ outside the cell and a high concentration of K+ inside the cell

28.  Types of Active Transport: • Membrane Pumps • Endocytosis • Exocytosis ENDOCYTOSIS • Type of Active Transport, requires ATP to occur • Requires additional energy because the cell is making major structural changes • Endocytosis is how: • Cells ingest large particles • Unicellular organisms ingest their food • Our body begins to get rid of bacteria and viruses • 2 Types of Endocytosis: • PINOCYTOSIS- transport of fluids • PHAGOCYTOSIS- movement of large particles or whole cells

29. Endocytosis:The Process • 1. Cell membrane folds in and begins to form a pouch • 2. Cell membrane encloses the external materials in a pouch • 3. Pouch pinches off to form a VESICLE • Vesicle - membrane bound organelle used to transport molecules. Often combines with lysosomes to break down ingested materials

30. Types of Active Transport: • Membrane Pumps • Endocytosis • Exocytosis EXOCYTOSIS • Type of Active Transport, requires ATP to occur • Requires additional energy because the cell is making major structural changes • Exocytosis is how: • Cells release proteins after protein leaves the Golgi • Cells release waste products

31. Exocytosis:The Process • 1. Vesicle moves to the cell membrane • 2. Vesicle fuses with the cell membrane • 3. Contents gets released to the outside of the cell

32. End Lecture 3