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Chapter Summary:
In this chapter, an amazing amount of information about cells, cell structure and cell function was learned. This chapter went over everything from the basic structure of a cell to DNA synthesis and replication. Although small, the cells is actually a very complex structure that contains many different functional units within itself.The cell contains an outer plasma membrane that all things going into and out of the cell are transported across. This section illustrated how diffusion works both simple and facilitated. Along with diffusion, there is the topic of osmosis which is water transport across a cell membrane. Some particles are too large to pass through the cell membrane on their own and need a "carrier" to help them across. This type of transport is called carrier-mediated transport and facilitated diffusion fits into this category along with active transport and bulk transport. Some cells have ionic charges that are attached to them. In the section regarding the membrane potential of cells, I learned that the inside of a cell is negatively charged whereas the outside of a cell has a positive charge. There is a difference in charges depending on the ionic concentration on each side of the cell. This difference is called the membrane potential of a cell. In order for cells to do their jobs correctly, they must be able to talk to one another. Cells talk to each other in many different ways. They can signal each other by paracrine signaling, synaptic signaling or endocrine signaling.

Transport across the cell membrane:
There are many different way in which molecules can move across a cell membrane. Some molecules need carriers to help transport them across a cell membrane. This type of transport is called carrier-mediated transport. Facilitated diffusion and active transport are both carrier-mediated transport methods. Facilitated diffusion occurs when molecules enter the outside of a cell membrane into a carrier protein, that carrier protein detects the molecule is appropriate for that cell and opens up on the inside of the cell to allow the molecule to enter. Active transport requires energy in the form of ATP and is the net movement of molecules across a cell membrane. In active transport, molecules move from lower to higher concentrations. This is why energy is required; because the molecules are moving against their concentration gradient. The other type of transport across a cell membrane is called non-carrier-mediated transport. Simple diffusion across a cell membrane, simple diffusion through a protein channel in a cell membrane and osmosis of water across a cell membrane are all examples of non-carrier-mediated transport. IN simple diffusion of molecules across the cell membrane, molecules move freely inside and outside of the cell because the cell membrane is permeable to those molecules. Molecules that cannot diffuse directly across the cell membrane can use protein channels (which are like little tunnels) to enter a cell. Aquaporin channels in cells allow water to pass through and crease osmosis.Below is a picture showing some different types of transport across cell membranes.
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Tonicity:
Intravenous solutions that are given to a patient are given to accomplish different things. Some patients just need a maintenance of their current fluid volume, some need a decrease in their fluid volume that they currently have, some patients need to increase their current fluid volume. This can all be done through the use of IV fluids and using the correct fluid that will react with blood cells in a manner that will create the desired outcome.
Isotonic solutions are those that have the same water and solute concentration on both sides of the cell membrane. The blood cell will not change in size when it is in an isotonic solution. When a cell is dehydrated and the body needs to take in extra fluid, a hypotonic solution is given. If a blood cell is immersed into a hypotonic solution, it will transfer water from outside the cell to inside the cell gaining in cellular volume. A hypotonic solution will have a higher concentration of water than the cell does so water is moved down the concentration gradient from high to low; from outside to inside the cell. If a red blood cell absorbs too much water, the cell can burst. Cells that are already swollen, such as in a case of edema, need a type of solution that will help them rid themselves of some of that excess fluid. Hypertonic solutions are used in this case. In a hypertonic solution, the water concentration is greater inside the cell than it is outside the cell. Water will then move down its concentration gradient (from high to low) and move out of the cell into the extracellular fluid. Too much water movement wither out of or into a blood cell can cause problems for the patient being treated. Hypertonic and hypotonic solutions are used to create a desired effect and then once that effect is reached, a patient can be switched over to an isotonic solution to keep their cells at the current volume they are at.
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Diffusion:
Diffusion is the transport of molecules across cell membranes.Molecules will move through the lipid layer of the cell membrane until equal concentrations are reached on both sides of the cell membrane. Molecules will move from the side of the cell that has a higher concentration to the side of the cell that has a lower concentration. The total amount of movement from one side of the cell to the other is called net diffusion. In cases where the solution concentration is the same on both sides of the cell, there will be no movement and therefore no net diffusion. When water is transferred across a cell membrane in this manner it is called osmosis. Diffusion will only occur if the cell membrane is permeable to the molecule traveling through it. Not all cell membranes are permeable to all molecules. Cells are said to be selectively permeable because only select molecules can move across them. The molecules that cannot permeate the cell membrane will need some type of assistance to pass into the cell. Ions pass into a cell through tunnel-like structures in the cell wall called protein channels. These protein channels are gated and are only open to the molecules they are programmed to open for. It is a type of cellular security system. You must have a pass to get through the protein channel gate.
Diffusion rate can be influenced by many things. First, the level of concentration on either side of the cell membrane greatly influences diffusion rate. The greater the concentration difference, the faster diffusion will occur. Second, the permeability of the membrane that the molecules are trying to cross has an influence on diffusion. If a cell membrane is not permeable to a certain molecule, that molecule will not pass through that membrane. The temperature of a solution also plays a large part in diffusion rate. The warmer a solution is, the faster diffusion will take place. Lastly, the surface area of the membrane that the molecules are trying to pass through greatly influences diffusion rates. The greater the surface area that the molecules have to move across, the more that will be able to move at a given time. The molecules are then not fighting for a space to move through the cell membrane.
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Application to Nursing:
I don't know many ways in which this unit would have a direct application to the field of nursing, other than tonicity of solutions, but I do know of another one in which I know it would help me. That is, communication and understanding with the doctors I will be interacting with. In medical school, doctors gain a much higher understanding of how the cells function within the human body than nurses do. Doctors must diagnosis and treat conditions based on their understanding of basic cell function. As a nurse, having more of an understanding of how cells are built and structured will give me more of an ability to understand where doctors are basing their treatment from. Also, many doctors like to explain things to nurses and teach some of what they know. with this understanding, what they are trying to teach will make more sense because the basic knowledge is there. Being able to use my knowledge to gain more knowledge will also help me to be able to explain to my patients what is going on inside their bodies. Patients need to trust in their nurse that they know what their talking about when they explain things to them and knowing that I have the knowledge will allow me to be a better educator to my patients as well.
Case Study/Essential Questions:
"Cells are considered the basic structure and function of the human body. What is meant by that statement? Compare and contrast passive and active transport. Include characteristics and examples of each type of transport cells used to maintain homeostasis. Why do cells need to bring molecules in and out of the cell membrane? How do cells communicate?" Cells are what is left when every other part and system of our body is broken down into smaller and smaller units until all we are left with is cells. The body is broken down into systems, systems are broken down into organs, organs are broken down into tissues, and tissues are broken down into cells. Cells are the activity hub that is responsible for our digestion, reproduction, metabolic action and every aspect of how we function.
In passive transport, molecules can move themselves across a cell membrane and will follow their concentration gradients. Molecules will move from where they have a higher concentration to where there is a lower concentration. passive transport does not require any energy for it to occur. In active transport, molecules move against their concentration gradient; from lower to higher concentrations and energy in the form of ATP is required. The regulation of blood glucose to maintain homeostasis is an example of passive transport. Glucose molecules will move down their concentration gradient from higher to lower concentrations. Glucose needs a carrier protein to help it enter into the cell because it is a large molecule. These carrier proteins open up to let the glucose in, then close around the glucose molecule. When the carrier protein detects that this is the correct molecule, it opens up on the inside of the cell to let the glucose into the cell. Although it sounds complicated, this type of transport is considered passive transport because it does not require energy to make this happen. Transport pumps are used to move molecules from lower concentrations to higher concentrations against their concentration gradient. The movement of calcium ions from inside to outside of a cell is an example of active transport. Calcium concentrations are lower inside the cell than outside the cell. The pumps that move the calcium against their concentration gradient require energy in the form of ATP to make that happen. The requirement of ATP is what makes this type of transport active transport.

Cells bring molecules in and out of the cell membrane for many different reasons. It can be for absorption of nutrients, release of hormones, release of ions to regulate blood plasma, etc. The most basic reason that cells bring molecules into and out of them is to maintain homeostasis of the body. The cells are the units responsible for all the functions of our bodies that keep us alive every day. It is this entering and exiting of molecules that adjusts our heart rate as needed, take up or release glucose to maintain proper blood sugar levels, stimulate uterine contractions when we give birth, just to name a few. This intake and release of molecules keeps up alive and functioning and that is why cells need to do it.
Cells communicate through messengers. When one cell sends a chemical a message to another cell, there is a complex set of information contained in that chemical reaction that takes place.Cells that are close together can communicate with each other through their gap junctions that hold them together. One cell releases a molecule that is then absorbed by the cell next to it. Most of the time though a cell will release chemical messages into the extracellular environment that are intended for another cell to receive. Cells that are releasing a message within an organ that is intended for a different cell within that same organ are communicating through paracrine signaling. Nerves and nerve parts communicate with each other and with target cells through synaptic signaling. In synaptic signaling, axons of nerves release neurotransmitters that are intended for specific target cells. The target cells then pick up these neurotransmitters and interpret their message. The endocrine system works through endocrine signaling. In endocrine signaling, the glands of the endocrine system release hormones that care carried by the blood to their respective target cells. In order for a cell to react to any given protein, it must have the needed target receptors and be a perfect fit for the hormone. If a cell does not have the needed receptor protein, the hormone will not act on that cell.