Cell Prof Gehane 2024 PDF

‫سورة البقرة آية ‪32‬‬  Lecture Objectives By the end of this lecture you should be able to:- 1)Describe cell membrane structure and function of its components. 2)Describe cellular transport. 3)Differentiate between passive and active transport 4) Describe functions of cytoplasm...

‫سورة البقرة آية ‪32‬‬  Lecture Objectives By the end of this lecture you should be able to:- 1)Describe cell membrane structure and function of its components. 2)Describe cellular transport. 3)Differentiate between passive and active transport 4) Describe functions of cytoplasmic organelles.  Cells—the fundamental unit of life Molecules of life Cell as fundamental unit Cell membranes and organelles Cell metabolism Cells organized into tissues. Eukaryotic cell Eukaryotic cell  The Cell Membrane Glycoprotein Extracellular fluid Glycolipid Phospholipids Cholesterol Transmembrane Peripheral proteins protein Cytoplasm Filaments of cytoskeleton A cell membrane or plasma membrane separates cell from outside world—creates ability to regulate internal environment (homeostasis) Structure of Cell Membrane  I- Membrane Lipids 1. Phospholipids (75%) 2. Cholesterol (20%) 3. Glycolipids (5%) (Lipids bound Carbohydrates)  Phospholipids Phosphate Fatty acid tails hydrophobic Phosphate group head hydrophilic Fatty acid Arranged as a bilayer Aaaah, one of those structure–function examples  Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads  More than lipids… In 1972, S.J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer It’s like a fluid… It’s like a mosaic… It’s the Fluid Mosaic Model!  II- Membrane Proteins Proteins determine membrane’s specific functions Membrane proteins: Peripheral proteins loosely bound to surface of membrane cell surface identity marker (antigens) Integral proteins penetrate lipid bilayer cross whole membrane transmembrane protein transport proteins. channels, permeases (pumps) Types of protein channels: Open channels: - They are open all the times. - e.g. Na+ & K+ leak channels which are important in resting membrane potential. Gated channels: - These channels have gates which regulate the movement of ions through them. - They are classified according to the cause that open & close their gates. Voltage- gated channels → e.g. Na+ & K+ voltage-gated Channels → they open or close by alteration in membrane potential. → they are important in action potential. Ligand-gated channels → e.g. acetylcholine. → they open or close by binding with a ligand. II- Membrane Proteins  III- Membrane carbohydrates Short sugar chains (oligosaccharide) on the outer membrane Attached to membrane lipids or proteins (Glycocalyx): 1- Glycolipids 2- Glycoproteins  What does selectively permeable mean? The membrane allows some things in while keeping other substances out  The transport mechanism across the cell membrane There are three mechanisms of transport across the cell membrane: I- Passive transport: Simple diffusion. Facilitated diffusion. A-Simple diffusion: It is movement of the molecules across the cell membrane according to their concentration gradient. It doesn't need additional source of energy or carrier protein. Pathways:- Diffusion through the lipid bilayer. - Diffusion through the protein channels. 1- Simple diffusion through the lipid bilayer: Lipid soluble substances → O2, alcohol & nitrogen. Water: it can penetrate the cell membrane although it is insoluble in membrane lipid, because: → water molecules are small & their kinetic energy are high. So, water molecules can penetrate like bullets. 2- Simple diffusion through protein channels: Passage of ions extremely slow through the cell membrane. Because: - ions move in hydrated form which has large size. - Repulsion occurs between ions & the charges of the lipid bilayer. So, the transport of ions through the cell membrane must occur through protein channels.  What are diffusion and osmosis? 1. Diffusion is the random movement of molecules from a higher concentration to a lower concentration 2. Osmosis is the diffusion of water molecules  Osmotic Solutions Isotonic – equal solute on each side of the membrane Hypotonic – less solute outside cell, water rushes into cell and cell bursts Hypertonic – more solute outside cell, water rushes out of cell and cell shrivels B- Facilitated diffusion: - It is movement of molecules across the cell membrane according to their concentration gradient. - This process is passive & not need energy, but it needs carrier protein to facilitate the transfer of molecules which cannot cross the cell membrane. e.g. glucose & amino acids Facilated diffusion  What are facilitated diffusion and active transport? 3. Facilitated transport is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier 4. Active transport is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier II-Active transport: - It is the movement of molecules across the cell membrane against the concentration gradient. - It needs source of energy. Types: A- Primary active transport: Energy comes from hydrolysis of ATP. e.g. Na+ & K+ ions. B- Secondary active transport: Use energy stored in the concentration gradient. e.g. Na+ - glucose transport.  Types of carrier proteins 1-Uniports → they transport one substance only across the cell membrane. 2- Symports → transport two substances in the same direction 3- Antiports→ they exchange one substance for another. e.g. Na+ - K+ ATPase or Na+ - K+ pump is a typical antiport carrier. It transports 3 Na+ out of the cell for 2 K+ into the cell. Vesicular transport: Large particles can enter or leave the cell by this type of transport. Types: A- Endocytosis: - It is a process by which large particles can enter the cell. - It needs energy supplied by ATP. B- Exocytosis: - It is a process by which secretory products of the cell such as hormones can leave the cell. - It needs energy supplied by ATP. What are endocytosis and exocytosis? The nucleus: - It is a spherical or oval structure, usually located near the center of the cell. - It is made up in large part of chromosomes that carries the individual′s characteristics. - Each chromosome is made of DNA. Function: It controls the cell activities & reproduction. Organelles: The most important organelles are: 1- Endoplasmic reticulum. 2- Golgi apparatus. 3- Mitochondria 4- Lysosomes. 5- Peroxisomes. Functions of Golgi Complex: 1-Modifies proteins and lipids. 2-Make and secrete mucus. 3-Packages products into vesicles. The concentration gradient determines what? A. How fast a molecule crosses the membrane B. How fast the cell will fill up C. How fast the cell can move D. How fast the flagellum will be able to grab onto an object. What are the three types of passive transport? A. Simple diffusion facilitated diffusion and pumps B. Exocytosis, endocytosis, pumps C. Exocytosis, endocytosis, osmosis D. Simple diffusion, facilitated diffusion, and osmosis The concentration gradient determines what? A. How fast a molecule crosses the membrane B. How fast the cell will fill up C. How fast the cell can move D. How fast the flagellum will be able to grab onto an object. What are the three types of passive transport? A. Simple diffusion facilitated diffusion and pumps B. Exocytosis, endocytosis, pumps C. Exocytosis, endocytosis, osmosis D. Simple diffusion, facilitated diffusion, and osmosis