Cell Biology Lecture Notes PDF

Cell Biology Amira Afify Assistant Professor at faculty of science, Cairo university [email protected] [email protected] Code of conduct Objectives By the end of this lecture, each student will learn:- 1.Permeability of the plasma mem...

Cell Biology Amira Afify Assistant Professor at faculty of science, Cairo university [email protected] [email protected] Code of conduct Objectives By the end of this lecture, each student will learn:- 1.Permeability of the plasma membrane:- 1.1. Diffusion 1.2. Osmosis 1.3. Tonicity 2- Transport by carrier protein 2.1. Facilitated transport 2.2. Active transport 3- Membrane-assisted transport 3.1. Exocytosis 3.2. Endocytosis 3.2.1. Phagocytosis 3.2.2. pinocytosis 3.2.3. Receptor- mediated endocytosis 1. Permeability of the plasma membrane The plasma membrane is selectively permeable. Certain substances can freely pass through the membrane and others must be transported across either by carrier proteins or by vacuole formation. The factors that determine if a molecule is able to move through the cell membrane are 1. Size 2.Concentration gradient 3. Polarity 1.1. Diffusion Diffusion is the movement of molecules from a higher to lower concentration- that is, down their concentration gradient- until equilibrium is achieved and they are distributed equally. A few types of small molecules can simply diffuse through the plasma membrane like Gases. Experiment of dye crystal dissolve in the water: Solution- Solute- Solvent. 1.2. Osmosis Osmosis is the diffusion of water into and out of cells. Experiment Osmotic pressure is the pressure that develops in a system due to osmosis. In other wards, the greater osmotic pressure the water will diffuse in that direction. 1.3. Tonicity Tonicity is the degree to which a solution’s concentration of solute versus water causes water to move into or out of cells. In an isotonic solution, a cell neither gain or loses water. In a hypotonic solution, a cell gains water. In a hypertonic solution, a cell loses water and the cytoplasm shrinks.  Activity (Participation) Working time: 10 min One of each group will summarize the last session. 2- Transport by carrier protein Carrier proteins are specific; each can combine with only a certain type of molecule or ion, which is then transported through the membrane. 2.1. Facilitated transport The passage of such molecules as glucose and amino acids across the plasma membrane even though they are not lipid-soluble without require to energy because the molecules are moving down their concentration gradient. 2.2. Active transport The passage of such molecules or ions across the plasma membrane require to energy because the molecules are moving against their concentration gradient. Proteins involved in active transport often are called pumps because they need energy Sodium-potassium pump:- One type of pump that is active in all animal cells but is especially associated with nerve and muscle cells.  Activity (Participation) Working time: 10 min One of each group will summarize the last session. 3- Membrane-assisted transport The transport of macromolecules such as polypeptides, polysaccharides, or polynucleotides. 3.1. Exocytosis  3.2. Endocytosis 3.2.1. Phagocytosis The process when the material taken in by endocytosis is large such as food particle or another cell Ex: macrophages engulf bacteria 3.2.2. pinocytosis Occurs when vesicles form around a liquid or very small particles. Ex: blood cells, cells that line the kidney tubules or intestinal wall use pinocytosis for ingesting substances. 3.2.3. Receptor- mediated endocytosis Allowscells to take up specific kinds of molecules and then release them within the cell.  Activity (Participation) Working time: 10 min One of each group will summarize the last session.  Activity (Brain storming) Working time:-10 min. Suggest questions