C.+Cells+and+Interactions+with+Environment

__Application __ Meagan- I think cells are a fascinating part of the human body. Without cells, we would not have tissues, organs, systems, or organisms. But most importantly, we would not have any DNA, I think it is amazing how the cells of our bodies can decide what it wants to keep and what it wants to get rid of. It is amazing the different ways in which our cells transport these materials:bulk transport to include endocytosis, phagocytosis, receptor-mediated endocytosis, and exocytosis. The plasma membrane also helps in separating the intracellular from the extracellular fluid with a slective mechanical barrier. This can be done by diffusion, membrane transport, passive transport, simple diffusion, and osmosis to name a few. As an OTA, it will be important for me to understand how these processes work in the human body. If there is an error in the function of these processes, it will affect the individual. Because of this, the individual may have a deficit.

Christine- Phagocytosis is an important process in our body. White blood cells use this process to fight off viruses and bacteria in our body. They do this by forming pseudopods (which literally means false feet) and surrounds the bacteria or virus to form a vacuole engulfing them. When this process is not working as effectively as it should it is our job as nurses to recognize this and find the necessary resources to help the patient out. This includes assessing the patient, taking vitals, and making sure the patients get the proper treatment.

﻿Kalli- Without transport systems like passive and active transport, our bodies would fail to do the wonderful things they do. During active transport, perhaps a pump is not working right in a certain area of the body, thus nerve cells in that area would not be going beyond the threshold to reach the action potentional and there would be no message or action. Obviously, as an OTA, I would not be able to help cure this irregularity, but I would be able to help the patient use what strength and muscle movement they do have (and adaptive devices) to help them go on with their life as they normally would.

__Content __ This unit discusses bulk transport to include endocytosis, phagocytosis, receptor-mediated endocytosis, and exocytosis. Passive transport is the movement of molecules across the cell that does not require energy expenditure. Passive transport includes simple diffusion, osmosis, and facilitated diffusion. Active transport is movement of molecules across the cell that does require energy expenditure. Active transport includes the Ca 2+ pump, Na+/K+ pump, and cotransport.

Passive transport is the movement of molecules along the gradient that requires **__NO ENERGY!!__** Examples of passive transport include simple diffusion, osmosis, and facilitated diffusion.

** Simple diffusion ** is the net diffusion of substance across the plasma membrane without the use of a carrier protein. This happens by either diffusion across the lipid bilayer or diffusion through channel proteins.



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** Osmosis **﻿ is the net movement of water across a selectively permeable membrane. It is driven by a difference in solute concentrations.Water will difuse from the more dilute solution into the more concentrated solution. Few solutes with large amounts of water (dilute) move to more solute with low amounts of water (concentrated).Water is easily moved through cell membranes by osmosis.



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** Facilitated diffusion **﻿ require cell membrane proteins, carrier proteins, to carry the molecules across the cell membrane from an area of higher concentration to an area of lower concentration.

High concentration on one side of membrane promotes binding while low concentration on one side of membrane promotes release. Adding carriers (exocytosis) or removing carriers (endocytosis) increase or decrease membrane permeability and rate of diffusion.

Picture- [] All information came from Human Physiology notes chapter 3, part 2: Passive transport: diffusion, osmosis, and facilitated diffusion.

Active transport ﻿requires carrier proteins that can move substances against their concentration gradient. Cells must expend energy in the form of ATP in order to move against the gradient. This __**DOES**__ require engergy!

Ca 2+ Pump ﻿ have high affinity for Ca 2+ and can efficiently regulate it down to very low concentration levels. The three pumps involved in the Ca 2+ pump share the basic features of the catalytic mechanism but differ in a number of properties related to tissue distribution, regulation, and role in the cellular homeostasis of Ca 2+. Ca 2+ is kept at low concentrations in the cytosol.



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Na+/K+ pump ﻿ is found in the membranes of many types of cells. In particular, it plays a very important role in nerve cell membranes. Notice that 3 positive ions (Na+) are pumped out of the cell (towards ECF) for every 2 positive ions (K+) pumped into the cell (towards ICF). This means that there is more positive charges leaving the cell than entering it. As a result, positive charge builds up outside the cell compared to inside the cell. The difference in charge between the outside and inside of the cell allows nerve cells to generate electrical impulses which lead to nerve impulses.



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Video on Active and Passive Transport []

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Compare Active and Passive Transport
- Active and passive transport can be compared by looking at their important functions of transporting particles using a gradient. - Both transports require the membrane to be permeable to the substance and a driving force to move the substance from one side of the membrane to the other.

Contrast Active and Passive Transport
- While both transports use a gradient, passive transport goes with the gradient, while active transport goes against the gradient. - Active transport requires energy expenditure (ATP), while passive transport does not require any expenditure of ATP.

Examples of Passive Transport
Diffusion Osmosis Facilitated Diffusion

Examples of Active Transport
Calcium Pump Sodium-Potassium Pump

Characteristics of Passive Transport
During passive transport, the diffusion rate increases when: the difference in concentration increases, the permeability for the diffusing substance increases, the solution temperature increases, the membrane surface area over which diffusion takes place increases

Characteristics of Active Tranport
act as a pump when carrier proteins can move substances against the concentration gradient

Why do cells need to bring molecules in and out of the cell membrane?
Cells bring molecules in because the molecules contain much needed resources such as nutrients, oxygen, and water. Cells release molecules containing toxic wastes,CO 2 ,and cell signals (hormones). Cells must regulate the type and amount of material entering and leaving the cell to maintain complexity and homeostasis inside the cell.