2.03 Cell Membranes and Homeostasis Essay

Diffusion is defined as the movement of molecules from an area of high concentration to an area of low concentration. The diffusion of water molecules through a semi-permeable(selectively permeable) membrane is osmosis. Semi-permeable means that some molecules can move through the membrane while others can not. Diffusion and Osmosis are passive forms of transport requiring no energy. Active Transport utilizes energy in the form of ATP. Water is a solvent that can dissolve a number of substances more than any other substance. Wherever water goes, through the ground or a body, it takes along valuable molecules. Water’s chemical composition causes it to be attracted to many different molecules and be attracted so strongly it disrupts the forces and dissolves it. Water can pass through the semipermeable membrane without any help but can change the solution, on the other side of the cell membrane, depending on how much it diffuses in and out.

All cells take in and use nutrients and other substances from the surroundings. Cells of the intestine and the kidney are specialized to carry out

1. In passive transport, what determines the direction of movement of small particles? The direction of movement of particles in passive transport is determined by the concentration gradient (diffusion) between the cytoplasm and the extracellular fluid. 2. Why do the molecules in facilitated diffusion need help moving across the plasma membrane? Likely, the molecules are too large to pass unaided through the plasma membrane with the concentration gradient; they need to pass through special transport proteins.

A cell needs to perform diffusion in order to survive. Substances, including water, ions, and molecules that are required for cellular activities, can enter and leave cells by a passive process such as diffusion. Diffusion is random movement of molecules in a net direction from a region of higher concentration to a region of lower concentration order to reach equilibrium. Diffusion does not require any energy input. Diffusion is needed for basic cell functions - for example, in humans, cells obtain oxygen via diffusion from the alveoli of the lungs into the blood and in plants water

The cell membrane is the outermost boundary of the cell, made up of proteins and lipids. This membrane holds the cell together and establishes the movement of materials that go into and out of the cell. This is a selectively permeable membrane: a barrier that allows some molecules to pass through, but prevents other molecules from penetrating (1). Passive transport is the movement of materials across a cell membrane without the use of energy from the cell. One type of passive transport is diffusion.

Introduction: Passive transport occurs when substances move from high concentration areas to a lower concentration region. Both Diffusion and Osmosis are examples of passive transport, however, osmosis is when water molecules move across a selectively permeable membrane. The plasma membrane, being a thin barrier to outside environment, is a selectively permeable membrane. Thus, it only allows certain particles to enter or exit the cell. A selectively permeable membrane is important because it protects the cell from certain materials that can potentially be toxic to the cell by not allowing the cell to diffuse uniformly; this means that not all particles can equally facilitate to the cell (encyclopedia ,n.d.). The movement of substance across a membrane is caused by two factors, their size and charge (Pearson Education, 2008). If a substance is small and nonpolar it can easily move but if it 's large and polar, it will have difficulty traveling across the membrane. For example, the selectively permeable membrane allows water, which is known as solvent, to move freely but prevents large molecules such as sugar molecules from passing through; the sugar molecules are known as solute (BBC, 2014).

In red blood cells, the sugar glucose is needed. They have protein carriers that allow glucose to move both in and out the cell without ATP, which gives the cell the material it needs, without using energy it uses for other things. 2. Plants,

Cells are always in motion, energy of motion known as kinetic energy. This kinetic energy causes the membranes in motion to bump into each other, causing the membranes to move in another direction – a direction from a higher concentration of the solution to a lower one. Membranes moving around leads to diffusion and osmosis. Diffusion is the random movement of molecules from an area of higher concentration to an area of lower concentration, until they are equally distributed (Mader & Windelspecht, 2012, p. 50). Cells have a plasma membrane that separates the internal cell from the exterior environment. The plasma membrane is selectively permeable which allows certain solvents to pass through

All cells contain membranes that are selectively permeable, allowing certain things to pass into and leave out of the cell. The process in which molecules of a substance move from an area of high concentration to areas of low concentration is called Diffusion. Whereas Osmosis is the process in which water crosses membranes from regions of high water concentration to areas with low water concentration. While molecules in diffusion move down a concentration gradient, molecules during osmosis both move down a concentration gradient as well as across it. Both diffusion, and osmosis are types of passive transport, which do not require help.

If a cell needs something from outside of the cell that could not enter via passive transport, then the cell would have to use energy. This kind of transport is called active transport. It’s when the molecules are moving from low to high concentration, which is moving against the concentration

The body can be described as a series of interconnected compartments. Cell membranes are the barriers among the different compartments. In order for drugs to gain access to the cells, they must move between the different compartments, more importantly cell membranes, after being administered. The two most important methods for dealing will cell membrane travel are diffusion through lipid and carrier-mediated transport.

Diffusion occurs when there is a concentration gradient of particles in a cell (a portion with a greater amount of particles in one area and less in another); when given time these particles will on their own, spread out evenly throughout the same area. When there is a semi-permeable cell membrane, only certain particles are permitted to enter the domain of the cell requiring osmosis to move water between the cell and its environment. (Kahn).

The cell membrane benifits the cell in many different ways and is composed of many different parts which help the membrane execute what it is supposed to practice. A model that represents these parts is called the fluid mosaic model. The model contains proteins and carbohydrates within a phospholipid bilayer that consists of hydrophobic tails and hydrophilic heads. All of the components within the bilayer play a role in the function of the cell membrane. For example the carbohydrates practice cell to cell recognition while the proteins transport molecules in the cell and back out. Proteins also have alternate functions such as intercellular joining and extracellular matrix. When molecules transport in and out of the cell through the membrane, there are two types of transport, passive and active transports. Passive transport occurs when molecules move with the concentration gradient. One example is simple diffusion, where the molecules transport through the cell membrane effortlessly moving from a high to low concentration. Then there is facilitated diffusion where the molecules such as glucose move with the concentration gradient but have to use a protein to pass through the membrane. Osmosis, however, is the diffusion of water molecules across the membrane, but the water molecules also need to pass through a protein because the inside of the lipid bilayer consists of hydrophobic tails. The purpose

2) All plants and animals are made up of cells and all cells are surrounded by a membrane. Any ion or molecule that the cell needs to either use or get rid of requires the ability to move through the cell membrane. Diffusion in plant and animal cells is the spontaneous net movement of ions and molecules from an area of high concentration to an area of low concentration, this is also referred to as moving down a concentration gradient. The movement of molecules and ions during diffusion is known as passive transport because they move as a result of their own kinetic energy. Although the kinetic energy is random in its movement due to the concentration gradient there will be net movement until dynamic equilibrium is reached. The rate of diffusion depends on the distance the molecule needs to travel, temperature, solubility, concentration gradient and the size of the molecule. Diffusion is dependent on the molecules being able to pass through the cell membrane, however, diffusion does not require a membrane in order to take place.

Diffusion only occurs when there is a concentration gradient. This means when a particular type of molecule is not spread out at an even concentration, but either exists in a higher concentration. The concentration gradient in regards to the movement of molecules (except water) always moves from high concentration to low concentration. Diffusion across cell membranes can occur in three main ways. The way in which it diffuses is depended on whether the molecules are small or large, and whether the molecules have already been concentrated. When really small molecules appear they are able to fit into a protein channel that is in the plasma membrane. This process of crossing the membrane can occur either by passive transport of active transport. When molecules are too big to fit through any channels, then they enter the cells by moving in a vesicle or by pumping, and this process is called active transport. When a molecule is crossing the membrane through passive transport, it is doing this because no extra energy needs to be used to get the molecule across the membrane. However when active transport is occurring this is because extra energy needs to be applied. Active transport can be done in two different ways, either by using pumps or using vesicles. Active transport using pumps moves small molecules against the concentration gradient. This is why there is extra energy needed. The pumps push molecules from areas of low concentration to high