BIO 1 - Cell Membrane and the Transport Mechanism.pdf

GENERAL BIOLOGY 1: Sir Ernest G. Fortu, LPT  LEARNING OBJECTIVES 1. Learners will be able to 2. Learners will be able describe the structural to relate the structural components of the cell components of the cell membrane membrane to its funct...

GENERAL BIOLOGY 1: Sir Ernest G. Fortu, LPT  LEARNING OBJECTIVES 1. Learners will be able to 2. Learners will be able describe the structural to relate the structural components of the cell components of the cell membrane membrane to its function (STEM_BIO11/12-Ig-h-11) (STEM_BIO11/12-Ig-h-12)  LEARNING OBJECTIVES 3. Learners will be able 4. Learners will be able to explain how cell to differentiate membrane regulates the endocytosis and transport of materials into exocytosis. and out of the cell STEM_BIO11/12-Ig-h-14 STEM_BIO11/12-Ig-h-13  CELL MEMBRANE Cell membrane provides separation between intracellular and extracellular environment. The ability of the cell to perform specific chemical exchanges with its environment is key to life, and it is the semipermeable membrane that causes this potential. PHOSPHOLIPID BILAYER  WHAT ARE PHOSPHOLIPIDS? Phospholipids are the main component in cell membranes. They line up in a bilayer arrangement, acting as a barrier to water soluble molecules.  PHOSPHOLIPID STRUCTURE The head of the The phospholipid tails are phospholipid is made two fatty acids. of one molecule of glycerol and a phosphate group.  PHOSPHOLIPID STRUCTURE The head is polar The fatty acid tails are non-polar because of the and hydrophobic (water hating). They phosphate group. are insoluble in water. This makes the head hydrophilic (water loving). It is soluble in water. Phospholipids are amphipathic as they have both hydrophilic and hydrophobic parts. CELL MEMBRANE Cholesterol (E) manages the fluidity of the membrane and stops the COMPONENTS phospholipids sitting too closely together. This stabilizes them and reduces the chance of the membrane Cholesterol freezing in cold temperatures. CELL MEMBRANE Inserted inside the phospholipid bilayer are proteins that help together diffusion COMPONENTS and cell recognition. Proteins called transport proteins (G) go all the way through the bilayer.  Integral proteins, collectively called CELL MEMBRANE membrane proteins (F), are found totally on one aspect of the membrane. COMPONENTS Large molecules like glucose use these channel proteins to help move across cell membranes passively. CELL MEMBRANE Channel proteins transport ions and polar molecules along the COMPONENTS concentration gradient. The pores allow substances to pass through without binding to the protein. Channel protein CELL MEMBRANE Proteins create a passageway for ions and polar molecules to move through COMPONENTS the cell membrane. Carrier proteins can transport substances along or against Carrier Protein the concentration gradient by changing conformation and binding to substances. CELL MEMBRANE The carbohydrate chain (D) on the glycoprotein (C) allows it to act as a COMPONENTS receptor molecule. They can bind with certain substances and some act as cell markers for cell-to-cell recognition. Carbohydrate chain Glycoprotein CELL MEMBRANE Glycolipids stabilize the cell membrane by making hydrogen bonds COMPONENTS with nearby water molecules. They support with cell recognition and triggering immune responses. Glycolipid  TRANSPORT MECHANISMS IN CELLS  TRANSPORT MECHANISM The cell membrane is a lipid bilayer where a large variety of proteins are embedded. These proteins serve different functions. They regulate the movement of solutes into and out of the cell. The transport of solutes across the membrane happens with four completely different processes: passive diffusion (down a gradient), carrier-mediated transport (also down a gradient), primary active transport (against a gradient), and secondary-active transport (also against a gradient). The cell membrane contains channels that are unit membrane-spanning proteins through that solutes will diffuse down a gradient.  PASSIVE TRANSPORT Passive transport is the movement of substances through membranes without using energy. This type of transport depends on the permeability of the cell membrane. Passive transport can be of three types: diffusion, osmosis, and facilitated diffusion.  DIFFUSION Diffusion is the net passive movement of particles (atoms, ions, or molecules) from an area of higher concentration to lower concentration.  OSMOSIS Osmosis is a special example of diffusion. It’s the diffusion of water through a partly semipermeable membrane from a more dilute solution to a more concentrated solution.  FACILITATED DIFFUSION Facilitated diffusion is the movement of specific molecules down a concentration gradient, passing through the membrane via a particular carrier protein.  ACTIVE TRANSPORT Active transport is the movement of molecules against a concentration gradient (lower concentration to higher concentration). It involves the use of carrier proteins that bind specific molecules. This type of molecular transport needs energy or Adenosine Triphosphate (ATP).  ACTIVE TRANSPORT Major examples of active transport include re-absorption of glucose, amino acids, and salts by the proximal convoluted tubule within the nephron in the kidney. ENDOCYTOSIS AND EXOCYTOSIS  The transport of materials into and out of the cell involves the formation of membrane-bound sacs that pinches away from the cell membrane. Endocytosis and exocytosis are two processes involved in the transport of matter through the lipid bilayer. Both endocytosis and exocytosis take place through the emergence of vesicles. In endocytosis, the cell takes in materials or substances from its surroundings. The cell membrane forms a pocket or small bag around a material outside the cell. The pocket then completes up and presses away from the membrane to form a vesicle. The vesicles formed by endocytosis may join in with lysosomes or with the different organelles. The three types of endocytosis are phagocytosis, pinocytosis, and receptor -mediated endocytosis. Exocytosis refers to the reverse process of endocytosis during which waste and alternative cell byproducts are excreted out of the cell by the formation of vesicles within the Golgi complex. Throughout exocytosis, vesicles within the cell fuse with the cell membrane and unleash their contents. Cells use exocytosis to export proteins that are packaged by Golgi complex. Nerve cells and cells of varied glands, as an example, unleash proteins by exocytosis. Cells should allow certain molecules, like nutrients inside. However, some molecules must be released such as signaling proteins and waste products, to the outside environment. THANK OU Y !