Cell Biology Lecture 2, Spring 2024 Lecture Notes PDF

1. What is the structure of a cell that protects and keeps things out? a. Cell membrane b. Chloroplast c. Vacuole D. Mitochondria 2. What is the organelle in a cell that powers the cell making energy? a. Cell membrane b. Chloroplast c. Vacuole D. Mitochondria 3. Prokaryotes are organisms ma...

1. What is the structure of a cell that protects and keeps things out? a. Cell membrane b. Chloroplast c. Vacuole D. Mitochondria 2. What is the organelle in a cell that powers the cell making energy? a. Cell membrane b. Chloroplast c. Vacuole D. Mitochondria 3. Prokaryotes are organisms made up of cells that lack 1. ……………. 2. ……………… Cell Membrane The plasma membrane Also known as the cell membrane or cytoplasmic membrane is a biological membrane that separates the interior of a cell from its outside environment. All cells have a cell membrane The function of the plasma membrane is: 1. Protect the cell from its surroundings. 2. Contains the cytoplasm (fluid in cell) 3. Selectively permeable to ions and organic molecules 4. Controls what enters and exits the cell to maintain an internal balance called homeostasis. 5. Plasma membranes must be very flexible in order to allow certain cells, such as red blood cells to change shape as they pass through narrow capillaries. 6. Plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to other cells to help group cells together to form tissues. 7. The membrane also maintains the cell potential 8. Allow cell recognition. Provide a binding site for enzymes. What is the other name for the Cell Membrane?  FLUID MOSAIC MODEL The fluid mosaic model of the cell membrane is how scientists describe what the cell membrane looks and functions like, because it is made up of a bunch of different molecules that are distributed across the membrane. Structure of the Cell Membrane  1- Phospholipids Contains 2 fatty acid chains that are nonpolar (water fearing-hydrophobic) Head is polar & contains a PO4 group & glycerol (water loving hydrophilic)  2- Cholesterol Cholesterol is a type of steroid which is helpful in regulating molecules entering and exiting the cell.  3- Proteins 1. Integral proteins They are embedded in the whole bilayer Integral proteins are helpful for transporting larger molecules, like glucose, across the cell membrane. Integral proteins have hydrophobic and hydrophilic areas 2. Peripheral proteins They are located on the inner or outer surface of the phospholipid bilayer Help with transport or communication. 4- 5- Cells need to: Take in things they need Get rid of the things they don’t need Communicate with one another  Solubility Materials that are soluble in lipids can pass through the cell membrane easily 1. Small molecules and larger hydrophobic molecules move through easily. e.g. O2, CO2, H2O 2. Ions, hydrophilic molecules larger than water, and large molecules such as proteins do not move through the membrane on their own.  Types of Transport Across Cell Membranes Two main types 1. Passive Transport 2. Active Transport Passive Transport The movement of materials across the cell membrane without using energy Caused by concentration gradient Works in both directions Three types: 1. Diffusion 2. Facilitated diffusion 3. Osmosis 1- Diffusion The process by which molecules spread from areas of high concentration, to areas of low concentration (Moving across the concentration gradient) No energy is required When the molecules are even throughout a space. it is called EQUILIBRIUM Diffusion across a membrane Requires NO energy Molecules move from area of HIGH to LOW concentration until equilibrium is reached Solute moves DOWN concentration gradient (HIGH to LOW) Small, uncharged particles (oxygen, carbon dioxide, most lipids) 2- Facilitated Diffusion Molecules that cannot directly diffuse across the membrane pass through  Channel proteins are embedded in the cell membrane & have a pore for materials to cross  Carrier proteins can change shape to move material from one side of the membrane to the other No ENERGY needed Used for Ions & large molecules (Cl- and glucose) 3- Osmosis Osmosis is the diffusion of water through a selectively permeable membrane down its concentration gradient From an area of high-water concentration to an area of lower water concentration Aquaporins are water channels which are protein pores used during OSMOSIS Aquaporins Predict what you think will happen to the water levels on either side of the semi permeable membrane. Osmotic Solutions Hypotonic- lower concentration of solutes Isotonic- concentrations of solute and solvent are equal Hypertonic- higher concentration of solutes Osmotic pressure Active Transport · Movement against a concentration gradient Requires Energy (ATP) One direction Types: Molecular Transport e.g.: Na+-K+ Pump Bulk Transport (Endocytosis and Exocytosis) Sodium- Potassium Pump Endocytosis The process by which cells absorb material (molecules such as proteins) from outside the cell by engulfing it with their cell membrane Two Types 1. Pinocytosis 2. Phagocytosis Pinocytosis Movement of liquids into the cell Called “Cell Drinking” Receptor-Mediated Endocytosis Some integral proteins have receptors on their surface to recognize & take in hormones, cholesterol, etc. Phagocytosis Movement of solids into the cell Exocytosis A cellular process where cells eject waste products or chemical transmitters (such as hormones) from the interior of the cell. Exocytosis is similar in function to Endocytosis but works in the opposite direction. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane.