Transcript: cell structure Holding it all together The plasma membrane The plasma membrane encloses the cell, making it distinct from other cells and from the outside environment. The plasma membrane is vital to the process of homeostasis, or the maintenance of a stable, steady internal environment. The plasma membrane enables this stability because it is selectively permeable. This simply means that the membrane controls what can enter or exit the cell. Useful nutrients are selectively allowed entrance while waste materials are selectively allowed to leave. Phospholipid membranes are fluid structures, similar in consistency to cooking oil. As you can see in the pictures, the plasma membrane is largely made up of molecules called phospholipids. Each phospholipid has a phosphate head and lipid tails. The head portion is hydrophilic, meaning that it interacts well with water. The tails are hydrophobic, avoiding contact with water. As a result, the phospholipids organize themselves into a phospholipid bilayer, with heads pointing outward and tails hidden away from the watery cytosol or extracellular (outside-the-cell) environment. Cholesterol molecules embedded in the bilayer help to maintain this fluidity. Also embedded within the bilayer are membrane proteins that act as gatekeepers, enforcing the selective permeability of the membrane. This description of the plasma membrane, with membrane proteins moving freely along the membrane, is called the fluid mosaic model The membrane that encloses and define all cells as seperate from the enviroment is called the plasma membrane or cell membrane The job of the plasma membrane is to seperate the chemical reactions occuring inside the cell from the chemicals outside The fluid inside the cell, called the cytoplasm, contains all the organelles and is very different from (cyto = cell) and (plasm = shape) cytoplasm literally means cell shape - fitting as the plasma membrane is what defines the cell shape plasma membrane are made of several different components, much like a mosaic work of work because membranes are a mosaic, and because they are flexible and fluid, scientists call them a 'fluid mosaic model'. TIP: Remember the plasma membrane as an international border controlling what enters or leaves the a particular country is a good way of remembering the plasma membrane in each cell the hydrophilic heads point towards watery environments (outside and inside the cell) sandwitching the hydrophobic bilayers Because cells reside in watery solutions (extra cellular matrix) and because they contain a watery solution inside of them (cytoplasm), the plasma membrane forms a sphere around each cell - so the water attracting heads are in contact with fluid and water repelling ttails are protected on the inside Other Components In addition to phospholipids, proteins play a major component of plasma membranes The proteins are embedded in the phospholipid layer, but they can drift laterally - like ships sailing in an oily ocean Cholesterol and carbohydrates are minor components of plasma membrane but they play fairly significant roles Cholesterol makes your membrane stable and prevents it from solidifying when your body temperature is low Carbohydrate chains attach to the outer-surface of the plasma membrane on each cell When they attach to the to phospholipids they form glycolipids - when they attach to the proteins they form glycoproteins Your DNA determines which specific carbohydrates attach to your cells, affecting characteristics such as your blood type Nuclear membrane The nucleus is limited by its nuclear membrane, which is a phospholipid bilayer interrupted at intervals known as nuclear pores The gaps provide direct communication between the nucleus and the cytoplasm It is difficult to overstate the importance of membranes to living cells; without them life could not exist. The plasma membrane, also known as the cell surface membrane or plasmalemma, defines the boundary of the cell. It regulates the movement of materials into and out of the cell and facilitates electrical signaling between cells. Straight Through the Membrane: Diffusion Through the Bilayer Molecules of oxygen are uncharged. Although they dissolve readily enough in water, they are also able to dissolve in the hydrophobic interior of lipid bilayers. Oxygen molecules can therefore pass from the extracellular fluid into the interior of the plasma membrane, and from there pass on into the cytoplasm, in a simple diffusion process Three other small molecules with important roles in biology—carbon dioxide, nitric oxide, and water itself—also pass across the plasma membrane by simple diffusion, as do the uncharged hormones of the steroid family. In contrast, charged ions cannot dissolve in hydrophobic regions and therefore cannot cross membranes by simple diffusion. http://www.biologymad.com/cells/cellmembrane.htm Passively moving along Importance TRANSPORT Actively helping molecules across Osmosis: Osmosis is simply the
Transcript: Cell Membrane Acts as a gatekeeper, provides structural support to the cytoplasm, recognizes foreign materials, and communicates with other cells. Turn to page 175 in your text book. Please label your image of the cell membrane, proteins, and enzymes. Transport Proteins Forms a doughnut-shaped channel. Allows for passage of sugars, ions, etc. Channels are particular. Different types of cells have different types of channels. Receptor Proteins Transmit information to inside cell. Protrudes out from cell: has particular shape: substances such as hormones bind to it and send messages inside cell. Cell Surface Markers Long, exterior arms: often with carboydrates attached. Identifies the type of cell. Immune defenses rely on markers to tell one cell from another. Enzymes - proteins in the membrane that help with biochemical reactions inside the cell. Cells must move substances that vary in size, electrical charge, and composition into and out of cell. Why must cells transport substances in and out of cell? A constant internal state that is maintained in a changing environment by continually making adjustments to the internal and external environment. Cell Surface Proteins Facilitated Diffusion http://go.hrw.com/resources/go_sc/interactOnline/hx/hxcen1_io.swf What is it? Transport proteins help substances that cannot pass through lipid bilayer diffuse into cell. 2 types of Transport Proteins 1. Channel Proteins: Ions, sugars, and amino acids use Channel Proteins. Each channel is specific to substance with correct size and charge. Example: Only sodium ions can pass through sodium ion channel. 2. Carrier Proteins: binds to a specific substance on one side of membrane. The binding causes protein to change shape. As protein's shape changes , the substance passes through the membrane and is released on other side. Cell Membrane Some substances diffuse through lipid bilayer. Others diffuse through transport (channel) proteins. Simple Diffusion Small, nonpolar molecules such as oxygen pass directly through bilayer. Concetration of oxygen higher outside than inside. So oxygen molecules move down concentration gradient into cell. Cell Transport Homeostasis Passive Transport Cell does not use energy to move substances in/out of cell. In solution, molecules move randomly to fill up space. Equilibrium is reached when space is evenly filled. Concentration gradient forms when one area has a higher concentration until equilibrium is reached. This movement is known as diffusion. Movement Through the Cell Regulates what enters and leaves cell: helps maintain homeostasis. Is selectivily permeable. Provides support and protection Composed of a "phospholipid bilayer" (lipids with phosphate group attached). Has polar head and nonpolar tail. Heads are hydrophillic/tails hydrophobic. Water soluble molecules are stopped by water insoluble tailes (sugars, proteins, ions) Facilitated Diffusion
Transcript: The Cell Membrane By:Bree, Drake and Nathan The cell membrane is the coating of the cell. Thank you for watching!!! There are two different types of membranes one animal one plant. The cell membrane protects the the inner part of the cell. plant membrane animal membrane Drake
Transcript: The Cell Membrane is made up of several things... A phospholipid bilayer. cholestrol glycolipids that grow off of the phospholipids glycoproteins that grow off of proteins intrinsic and extrinsic proteins a tranporter protein allows big molecules to pass through the cell mebrane. The cell membrane has many functions The most important function the cell membrane has is protecting the cell from the outside world. It creates a barrier between the inside and outside and chooses what it allows to come in. Essentially it is like a city wall... The cell membrane has so many functions it was impossible to fit it all in one slide other functions of the cell membrane include... Allows essential nutrients into the cell Gets rid of waste materials that are inside of the cell the cell membrane is selectively permeable which means it can choose what it lets in and out of it. If you were to compare the cell membrane to a factory machine it would be most like the walls of the building that protects the other machines. http://en.wikipedia.org/wiki/Cell_membrane http://www.wisconline.com/objects/ViewObject.aspx?ID=ap1101 http://www.biologymad.com/cells/cellmembrane.htm http://www.biology-online.org/dictionary/Cell_membrane http://biology.about.com/od/cellanatomy/ss/cell-membrane.htm Function Continued References What is the cell membrane like? The Cell Membrane Structure Function By: Tyler Mlakar and Levi Thornbrugh
Transcript: Importance All living cells, prokaryotic & Eukaryotic have a plasma membrane allows nutrients & other essential elements to enter the cell & waste materials to leave the cell Holds cells together & keeps other substances out Structure Double layer lipids Function Plasma membrane proteins function in several different ways Serves as as external cell barrier, acts in transport of substances into or out of cell Other Information plays a dynamic role in many cellular & activites Defines extent of a cell, dividing two major fluid department; intracellular & extracellular Purpose Without the cell membrane the cell would have no protection or structure. Any sort of bacteria could get through to the bare cell and causes damage to the cell and diseases for the human body. By: Maddison Fuller & Hannah Anderson Plasma Membrane (Cell Membrane)
Transcript: What other two macromolecules is the Cell Membrane made of? Proteins that form channels and pumps & Carbohydrate chains as ID cards Provides protection and support for the cell Water, oxygen, & carbon Dioxide are able to pass through the cell wall Found in plants, algae, fungi, and most prokaryotes Cells are divided into two categories: Prokaryotes & Eukaryotes Prokaryotes They are smaller and simpler and do not have a nucleus Example - bacteria Eukaryotes contain a nucleus & membrane bound organelles Examples plants, animals, fungi & other microorganisms bi = two two layers of lipids! The cell membrane is made up of a lipid bilayer Cell Bounderies Cell Membrane Cell Walls Cell Types Control what enters and leaves the cell & provides protection and support.
Transcript: What is Selectively Permeable? Stucture! (cc) image by rocketboom on Flickr Three Cell membranes can be found on both animal and plant cells. It forms a boundry between the inside and the outside of the cell. Cell membranes are selectively permeable. Two <iframe width="640" height="360" src="http://www.youtube.com/embed/Qqsf_UJcfBc?feature=player_detailpage" frameborder="0" allowfullscreen></iframe> Selectively Permeable means that the cell membrane controls what enters and exits the cell. Its made up of proteins and phospholipids. Proteins are used as sensors for recognizing the bad material. (cc) image by quoimedia on Flickr Cell Membrane Corey Canavan & Mary Clarke Four
Transcript: Parts of Membrane Faciliated Diffusion Lipids The Cell Membrane is sometimes called the plasma membrane because many cells in the body are indirect contact with the fluid portion of the blood- the plasma active Diffusion: the movement of small uncharged molecules down a concentration gradient The Cell Membrane regulates what enters and leaves the cell and also provides protection and support Role of Membrane Cell Membrane Transport Types of Transport And Proteins within the membrane are key to the functioning of the overall membrane. These proteins mainly transport chemicals and information across the membrane. Every membrane has a varying degree of protein content. Proteins can be in the form of peripheral and intergal. The lipid bilayer is a thin membrane made up of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around the cells. Diffusion and Faciliated Proteins passive
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