Lesson 7 - The Cell Membrane PDF

 Quote of the day: “Be selective in your Battles, Sometimes peace is better than being right” Are you a Selective Person? Does being selective a good character?  How will you describe a Cell Membrane?  What is a Cell Membrane?  What is a Cell Membrane? Basically, a cell m...

 Quote of the day: “Be selective in your Battles, Sometimes peace is better than being right” Are you a Selective Person? Does being selective a good character?  How will you describe a Cell Membrane?  What is a Cell Membrane?  What is a Cell Membrane? Basically, a cell membrane (or plasma membrane) is an ultrathin, plastic, dynamic, electrically charged, and selectively-permeable membrane layer that separates the cytoplasm from the extracellular matrix and helps in maintaining the cell structure and function. This should not be confused with the cell wall, which is an extra layer present outside of the cell membrane mainly in plants, bacteria, and  What is a Cell Membrane? An animal cell membrane is an outermost layer whereas the plant cell membrane is the second layer after the plant cell wall. The Cell Membrane is a selectively permeable membrane, which means that the cell membrane allows only some substances and molecules to pass into or leave the cell.  What describes the Cell What describes a Cell membrane? 1. Selectively Permeable 2. Phospholipid Bilayer 3. Fluid Mosaic Model SELECTIVELY PERMEABLE - Controls what comes in and out of the cell. Does not let large, charged or polar things through without help. We should take note here that the membrane is selectively permeable and not semi-permeable. Semipermeable membranes are more simple in function because they are not “picky”, so If molecules are small enough they will pass through the membrane by osmosis, diffusion or following its concentration gradient from an area of higher concentration to an area of lower solute concentration. Selectively permeable membranes are more specific (hence the name selective) as to What is the cell membrane made of? The cell membrane is composed of varying amounts of lipids, carbohydrates, and proteins. Although lipids form the basic structure of the plasma membrane, proteins and carbohydrates play irreplaceable roles in the  The cell membrane is composed mainly of phospholipids, which consist of phosphate, glycerol and fatty acids. The phospholipids in the cell membrane are arranged in two layers, called a phospholipid bilayer. Each phospholipid molecule has a head and two tails. The head "loves" water (hydrophilic) and the tails "hate" water (hydrophobic). The water-hating tails are on the interior of the membrane, whereas the water-loving heads point outwards, toward either the cytoplasm or  The currently accepted model for the structure of the plasma membrane, called the fluid mosaic model, was first proposed in 1972. This model has evolved over time, but it still provides a good basic description of the structure and behavior of membranes in many According to the fluid mosaic cells. model, the plasma membrane consists of a mosaic of components—primarily, phospholipids, cholesterol, and proteins—that move freely and fluidly in the plane of the membrane. FLUID MOSAIC MODEL - The phospholipids move, thus allowing small non-polar molecules to slip through. What are the Components of the Cell membrane? The main component of the cell membrane are phospholipids. However, there are also others, which include four total components: 1. Phospholipids 2. Proteins 3. Carbohydrates 4. Cholesterol 1. Phospholipids Phospholipids are a type of lipid that makes up the cell membrane. Phospholipids are amphipathic, meaning they have both hydrophobic parts, which do not readily mix with water, and hydrophilic parts, which mix with water. 1. Phospholipids The amphipathic nature of the phospholipids results in a bilayer structure of the membrane. The amphipathic nature of the phospholipids also allows the membrane to be semi-permeable or selectively permeable.  2. Proteins Proteins are the second major component of plasma membranes. There are two main categories of membrane proteins: integral and peripheral. Integral membrane proteins are, as their name suggests, integrated into the membrane. They assist specific larger and charged molecules to move in and out of the cell. They can act as ‘tunnels’ or will change shape. Proteins that extend all the way across the membrane are called transmembrane proteins. Peripheral membrane proteins are found on the outside and inside surfaces of membranes, attached either to integral proteins or to phospholipids. Unlike integral membrane proteins, peripheral membrane proteins do not stick into the hydrophobic core of the membrane, and they tend to be more loosely 2. Proteins INTEGRAL PROTEINS - assists specific larger and charged molecules to move in and out of the cell. Can act as ‘tunnels’ or will change shape. 3. Carbohydrates Carbohydrates are the third major component of plasma membranes. In general, they are found on the outside surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids). These carbohydrate chains may consist of 2-60 monosaccharide units and can be either straight or branched. Along with membrane proteins, these carbohydrates form distinctive cellular markers, sort of like molecular ID badges, that allow cells to recognize each other. These markers are very important in the immune system, allowing immune cells to differentiate between body cells, which they 3. Carbohydrates  4. Cholesterol Cholesterol, another type of lipid that is embedded among the phospholipids of the membrane, helps to minimize the effects of temperature on fluidity. At low temperatures, cholesterol increases fluidity by keeping phospholipids from packing tightly together, while at high temperatures, it actually reduces fluidity. In this way, cholesterol expands the range of temperatures at which a membrane maintains CHOLESTEROL: Reduces membrane fluidity by reducing phospholipid movement. Also stops the membrane from becoming solid at room temperatures.  Quote of the day: “Like the Cell Membrane, be selective in your Battles, Sometimes peace is better than being right”