Chapter 5 Lecture Notes PDF

monomer ! 1) lipods-don't have a Monosaccharide 2) carbohydrates - acids amino 3) proteins - &1. Inocleic...

monomer ! 1) lipods-don't have a Monosaccharide 2) carbohydrates - acids amino 3) proteins - &1. Inocleic alid-nucleosises List the 4 biological macromolecules and the monomer that makes up each. Note that only 3 have monomers. 2. List a specific type of each biological macromolecule that you would find in a cell. 3. What cell structures/parts are shared by animal, plant, and bacterial cells?  Chapter 5 Membranes: The Interface Between Cells and Their Environment 5.6 Exocytosis and Endocytosis tasm Endocytosis and exocytosis are mechanisms of vesicular transport that move large material into or out of cells ↳ 5.6 Completing the Endomembrane System: Exocytosis and Endocytosis During exocytosis, materials inside the cell are packaged into vesicles and excreted to the extracellular space/fluid These vesicles are usually derived from the Golgi Let’s watch these videos: https://www.youtube.com/watch?v=K7yku3sa4Y8 and 5.6 Exocytosis and Endocytosis # During endocytosis, the plasma membrane invaginates (folds inward) to form a vesicle that brings substances into the cell & Three types of endocytosis: 1. Receptor-mediated endocytosis uses receptor proteins to bring in specific cargo 1. See how cholesterol in your diet is transported into cells by Drink & endocytosis 2. Pinocytosis primarily brings in fluid, allowing cells to sample - the extracellular environment 3. Phagocytosis involves bringing in very large particles (ex: a -- ca solids bacterial cell); only some cells are- phagocytes Watch this video of phagocytosis of a bacterium https://www.youtube.com/watch?v=I_xh- bkiv_c Vocab-ology! Phage = eat Pino = drink 5.6 Exocytosis and Endocytosis During endocytosis, the plasma membrane invaginates (folds inward) to form a vesicle that brings substances into the cell 5.1 Membrane Structure Section 5.1 Learning Outcomes 1. Describe the fluid-mosaic model of membrane structure 2. Identify different types of membrane proteins 5.1 Membrane Structure The 2 primary structural components of membranes are phospholipids and proteins; membranes perform many functions Carbohydrates may be attached to membrane lipids and proteins, forming glycolipids and glycoproteins 5.1 Membrane Structure Biological Membranes Are a Mosaic of Lipids, Proteins, and Carbohydrates The fluid-mosaic model describes the membrane as a mosaic of lipid, protein, and carbohydrate molecules where the lipids and proteins can move relative to each other within the membrane Video: https://www.youtube.com/watch?v=Qqsf_UJcfBc&t=1s ⑪-poer ad Terms: ↑fate Leaflet Bilayer Fluidity ioniaction ↳ /hydrophobic inside O 5.1 Membrane Structure Proteins Associate with Membranes in Three Ways Although the phospholipid bilayer is the structural core, proteins carry out many important membrane functions Proteins are categorized based on their association with the membrane: Integral membrane proteins have a portion that is integrated into the hydrophobic region of the membrane Peripheral membrane proteins are noncovalently bound to regions of other proteins or to the polar portions of phospholipids Group Work 1. Identify the types of bonds holding the phospholipids of the plasma membrane together in a bilayer. A. Phospholipid polar head with Extracellular space outside of cell lonic u/ water E. Orientation of cholesterol within B. Ends of opposing the phospholipid phospholipids bilayer hydrophobic attraction Hydrophilic attraction * first bump D. Lipid tails of adjacent phospholipids C. Phospholipid polar head with Hydrophobic inside of cell ⑪ Intracellular space attraction hydrogen bonds + lonicbonds Group Work 1. Now let's see a protein incorporated into the bilayer. This particular protein has the illustrated primary structure. How would you expect this protein to associate with the plasma membrane? Polar R-grp Non- polar R-grp A O B polar heads interact with outside C Group Work 1. Now let's see a protein incorporated into the bilayer. This particular protein has the illustrated primary structure. How would you expect this protein to associate with the plasma membrane? Polar R-grp Non- polar R-grp A B O C 5.2 Fluidity of Membranes Section 5.2 Learning Outcomes 1. Describe the fluidity of membranes 2. Predict how fluidity will be affected by changes in lipid composition 5.2 Fluidity of Membranes Membranes Are Semifluid Phospholipids have free lateral movement. Use this picture to explain why phospholipid “flip-flop” is rare. Gif this happens, that means cell is dying.  5.2 Fluidity of Membranes Membranes Are Semifluid Smooth ER will make new phospholipids in response to outside temperature and other physiologic needs. These lipids eventually end up in the cell’s internal and outer membranes. 2. New 1. New phospholipids made here. phospholipids Depending on environment, these travel here!! may: 1) Have shorter lipid tails 2) Have more/less double bonds between carbons. (more detail on next slides) Consider the plasma membrane of cells in the legs of a caribou. A) If the phospholipids remain the same how will the fluidity change & when temperatures decrease in wintertime? (less fluid or more fluid?) B) How will this change in membrane fluidity affect the transport of nutrients and waste into/out of cells? fluidia , 5.2 Fluidity of Membranes Smooth ER can make different phospholipids depending on the needs of the cell The THREE factors that effect the fluidity of a membrane 1. Length of the nonpolar tails (tails range from 14 to 24 carbons) - - Shorter tails have less hydrophobic attraction between them  more fluid membrane 2. Presence of unsaturated fatty acid tails- (double bonds) Double bond puts a kink in the lipid tails, allowing kinetic motion for each phospholipid  making the bilayer more fluid less hydrophobic attractions here I #I each lipid has Hu more kinetic motion  5.2 Fluidity of Membranes Smooth ER can make different phospholipids depending on the needs of the cell The THREE factors that effect the fluidity of a membrane 3. Presence of Cholesterol Cholesterol pushes lipid tails apart in Cholesterol pulls lipid tails together in low temperatures. warmer temperatures. Gives phospholipids more space from Maintains sufficient hydrophobic solidifying. attraction between phospholipids. Pics from Amoeba Sisters  5.2 Fluidity of Membranes Smooth ER can make different phospholipids depending on the needs of the cell Membrane fluidity is a concept that is directly affected in cases of extreme Heat Stroke Sound bite from Podcast “Not Built for This: Maximum Temperature,” released September 6, 2024 Start at 20:00 – 22:27 time stamp Cholesterol pulls lipid tails together in warmer temperatures. Maintains sufficient hydrophobic attraction between phospholipids. Pics from Amoeba Sisters 5.3 Overview of Membrane Transport Section 5.3 Learning Outcomes 1. Compare and contrast simple diffusion, facilitated diffusion, passive transport, and active transport 2. Explain the process of osmosis and how it affects cell structure 3. Predict the direction of water movement in response to a solute gradient 5.3 Overview of Membrane Transport The Phospholipid Bilayer Is a Barrier to the Simple Diffusion of Hydrophilic Solutes Examine the High, Low, and Very Low permeability groups of molecules. [ Remember that 1. molecules are generally polar or nonpolar 2. the plasma membrane has a nonpolar core of lipids Now discuss why each group can or cannot cross the plasma membrane. 5.3 Overview of Membrane Transport The Phospholipid Bilayer Is a Barrier to the Simple Diffusion of Hydrophilic Solutes Next, in your groups explain “facilitated diffusion” based on this picture. transmembrane Protein ↑ > a they ree x-- Start around 1:30 https://www.youtube.com/watch?v=jhszFBtBPoI 5.3 Overview of Membrane Transport Substances can cross the membrane in 3 general ways: simple diffusion, facilitated diffusion, or active transport Passive transport does not require an input of energy whereas active transport does require energy 5.3 Overview of Membrane Transport Cells Maintain Gradients Across Their Membranes Living cells maintain a relatively constant internal environment that is different from their external environment A transmembrane gradient (concentration gradient) is present when the concentration of a solute is higher on one side of a membrane than the other st An electrochemical gradient is a dual gradient with both electrical and chemical components Ion gradients know definition 5.3 Overview of Membrane Transport Osmosis Is the Movement of Water Across Membranes to Balance Solute Concentrations The most transported molecule across a cell membrane is water. It even has its own category of diffusion called Osmosis. Rule/Memory tool: Water moves to dilute a solute. Practice 1. For each cell, draw an arrow indicating the net movement of water by osmosis 2. Match the top cells to the bottom images of cell swelling, shrinking, neither the cell is in "Hypertonic This solution is tonic G solution 10M NaCl 0.001M NaCl 1M NaCl Treater a ↓ centratin 11 1M NaCl 1M NaCl ==1M NaCl The cell · is in a solution by personic Il in the solution. · The cell ihypotonic s Hypertonic 2 X Hypotonic - L - I so tonic 5.3 Overview of Membrane Transport Osmosis Is the Movement of Water Across Membranes to Balance Solute Concentrations How does osmosis affect cells with a rigid cell wall (bacteria, fungi, algae, plants)? If the extracellular fluid is hypotonic, a plant cell will take up a small amount of water, but the cell wall prevents osmotic lysis If the extracellular fluid is hypertonic, water will exit the cell 5.4 Transport Proteins Section 5.4 Learning Outcomes 1. Outline the functional differences between channels and transporters 2. Compare and contrast uniporters, symporters, and antiporters 3. Explain the concepts of primary and secondary active transport 4. Describe the structure and function of pumps  Substances can cross the membrane in 3 general ways: 1) Simple diffusion, 2) Facilitated diffusion, or 2) Active transport Passive diffusion Active Transport Simple diffusion Facilitated diffusion 5.4 Transport Proteins- Passageways for Solute Movement Channels provide an open, fixed Transporter or Carrier channels bind to shape passageway molecule and must change shape to allow transportation of molecule to Used only in Facilitated other side of membrane. Diffusion For Facilitated Diffusion or Active transport 5.4 Transport Proteins Channels Provide Open Passageways for Solute Movement Channels provide an open passageway that can facilitate the diffusion of hydrophilic molecules or ions Most channels are gated, meaning they transition between open and closed states based on regulatory signals Ex: some channels are regulated through interactions with other small molecules like hormones or neurotransmitters In contrast to transporters, channels do not have a specific binding site (pocket) for their solutes 5.4 Transport Proteins Transporters Bind Their Solutes and Undergo Conformational Changes Transporters (aka “carriers”) bind their solutes in a hydrophilic pocket and undergo a conformational change that switches the exposure of the pocket from one side of the membrane to the other Transporters provide the principal pathway for uptake of organic molecules, such as sugars, amino acids, and nucleotides; they are also involved in expelling various waste materials out of cells 5.4 Transport Proteins Transporters Bind Their Solutes and Undergo Conformational Changes Transporters are named according to the number of solutes they bind and the direction in which they transport those solutes: Uniporter transport in one direction- Symporter in direction 2 solutes moving same Antiporter directions. two solutes moving in opposite 5.4 Transport Proteins Active Transport Is the Movement of a Solute Against a Gradient Active transport is the movement of a solute across a membrane against its gradient (from lower to higher concentration area) Energetically unfavorable and requires the input of energy There are 2 general types: primary and secondary active transport Primary active transport directly uses energy (typically released from ATP hydrolysis) to transport a solute against its gradient 5.4 Transport Proteins Active Transport Is the Movement of a Solute Against a Gradient Secondary active transport involves the use of energy stored in a pre-existing gradient to drive the active transport of another solute Ex: the H+/sucrose symporter depicted below uses the energy of the H+ gradient to move sucrose against its gradient H+ is used by many symporters in bacteria, fungi, algae, and plant cells whereas Na+ use is prevalent in animal cells 5.4 Transport Proteins ATP-Driven Ion Pumps Generate Ion Electrochemical Gradients Cells have many different types of ion pumps in their membranes Ion pumps maintain ion gradients that drive many important cellular processes: Cells invest a tremendous amount of their energy (up to 70%) into ion pumping 5.5 Intercellular Channels Section 5.5 Learning Outcomes 1. Contrast the structure and function of gap junctions and plasmodesmata 5.5 Intercellular Channels Channels that allow direct movement of substances between adjacent cells Gap junctions can connect animal cells Plasmodesmata can connect plant cells -- attach Cytosol 5.7 Cell Junctions Section 5.7 Learning Outcomes 1. Outline the structure and function of anchoring junctions and tight junctions Tight Junctions Adherens Junctions # (connect the Actin from cell to cell) O Desmosomes (connect the intermediate G filaments from cell to cell) At ↳ Hemidesmosomes (connect cell to extracellular matrix) 5.7 Cell Junctions Tight Junctions Prevent the Leakage of Materials Across Animal Cell Layers Tight junctions form a tight seal between cells and prevent material from leaking between adjacent cells Occludin and claudin are integral membrane proteins used to form tight junctions Along intestinal lumen, tight junctions: Prevent leakage of lumen contents into the blood Help organize different protein transporters on the apical and basal surfaces Prevent microbes from entering the body 5.7 Cell Junctions Anchoring Junctions Link Animal Cells to Each Other and to the Extracellular Matrix (ECM) Animals are multicellular; to become multicellular, cells must be linked together Gap junctions and plasmodesmata allow movement of solutes and signals between cells; other junctions physically adhere cells to each other and to the ECM Anchoring junctions link cells to each other and to the ECM Cell adhesion molecules (CAMs) are integral membrane proteins that participate in forming these junctions Cadherins and integrins are 2 types of CAMs Anchoring junctions are grouped into 4 main categories: adherens junctions, desmosomes, hemidesmosomes, and focal adhesions