“Cells are the basic building blocks of all living things” (Genetics Home Reference, 2015), cells are the smallest unit that is capable of performing life functions. They are responsible for the conversion of nutrients from food into energy, the structure of the body and perform specialised functions for each different organelle. There are two main types of cells, Prokaryotic and Eukaryotic. The Prokaryotic (see appendix one) is a single-celled organism without a membrane-bound structure, meaning it lacks a nucleus, mitochondria and any other membrane-bound organelles (Unknown, 2015).
The Eukaryotic is any cell or organism that has a cell membrane-bound structure. Meaning it contains the major organelles inside a cell (Arrington, 2014). Inside the cell there are the main organelles. There is the Nucleus which is a noticeable organelle containing most of the cell’s DNA, which is surrounded by a Nuclear Membrane. The Mitochondria is an oval structure bounded by a double membrane, this organelle converts chemical energy into Adenosine Tri-Phosphate (ATP). A Lysosome is a sac bounded by a single membrane and the Golgi apparatus or bodies stores chemicals and gets rid of waste. There are some minor organelles in the cell which consist of the Endoplasmic Reticulum (rough and smooth), Ribosomes and cytoplasm to just name a few. View images two of appendices for a diagram of the Eukaryotic Cell.
The Cell Membrane (Plasma Membrane)
All cells have a plasma membrane that forms the outer protection of a cell which separates the interior of the cell from the exterior. The Original model of the structure of a membrane was created by Davson and Danielli, where there unit membrane was covered by a liquid bilayer coated with protein. An example of this protein is the Aquaporins; these are the water transporting channels of the membrane using the passive process (Tajkhorshid, 2006). This model has been modified due to many years of research and the accepted model of the structure is the “Fluid-Mosaic Model” to view this diagram of the model head to image three of the appendices.
The Fluid Mosaic Model has a bilayer of amphipathic Phospholipids which are arranged with the hydrophobic tails facing in and the hydrophilic head facing out. The cell membrane is also made up of cholesterol which joins phospholipids together; Glycoproteins which are proteins with carbohydrates attached and Glycolipids are lipids with carbohydrates attached, which allows things to transport across the membrane by attaching to the glycolipids (Biology, 2015).
Phospholipid
The phospholipid molecule is a compound of two hydrophobic tails and one hydrophilic head (image four of appendices). The hydrophilic head contains groups of phosphate attached to glycerol molecules and the hydrophobic tails contain either a saturated or unsaturated fatty acid (Biology, 2015). The hydrophobic tails, water rebelling molecules, are non-polar meaning they have no charge whereas the hydrophilic heads, water loving molecules, are polar meaning they have a negative charge. Due to the water fearing tails and the water loving heads, the phospholipid bilayer satisfies both ends without interfering. However, water molecules are transported through Aquaporins so it does not interfere with the Hydrophobic tails in the phospholipids; these membrane proteins where discovered by Peter Agre in 1992 (Aquaporin A/S, 2007).
Types of Transport
The cell membrane is a selectively permeable to ions and molecules and will control the movement of substances in and out of the cell. There are two types of transport across the membrane, active and passive.
Active transport is when the cell membrane uses energy to transport ions and molecules through the cell membrane. Throughout the cell membrane there are proteins, Integral membrane protein, Peripheral membrane protein and protein channels, which work to transport ions and molecules through the membrane. One part of the protein is positioned outside the cell and the other half is inside, allowing molecules and ions to move across the membrane bilayer (Rader, 2014). In the image five of the appendices it shows how the ions and molecules are transported through the membrane.
Passive transport does not require energy to transport of biochemical and other atomic or molecular substances across the cell membrane as it is transferring the molecules with the concentration gradient (high to low) resulting in no energy being needed (ENOTES, 2008). Carbon Dioxide and Oxygen are small molecules with no charge and can freely move across the cell membrane through one of the four types of passive transportation, diffusion, facilitated diffusion, filtration and osmosis (Passive Transport, 2015).
Osmosis is used for the specific transportation of water molecules across the semi-permeable membrane. This involves the movement of water into a region of higher solute concentration to a lower solute concentration to equalise the solute concentrations on either side (Osmosis, 2015). See appendix six.
This equalisation of the amount of fluid on either side of the semi-permeable membrane creates the state which is known as “Isotonic”. This occurs when both sides of the cell have the same concentration of the solute. However if the solution has low levels of the solute it is considered to be “Hypotonic” and if the solution has high levels of the solute it is identified as “Hypertonic”. In image 7, it displays that the different levels of solute will affect the cell itself by dehydrating it (hypertonic), over hydrating it (hypotonic) or keeping it the same.
The aim of this extended experimental investigation is to determine which fluid or drink is better at hydrating an athlete after exercise. This task analyses the three drinks Gatorade, Red Bull and Bottled Water; these three drinks all have different concentrations.
The experiment will consist of potatoes in each of these drinks to see which drink keeps the potato in the isotonic state. As the potato has a semi-permeable membrane will allow the diffusion of water molecules to go in and out of the potato, depending on the concentration gradient between the potato and the solutions. If the solutions have a higher concentration of carbohydrates or glucose, then the potato the water will pass through the membrane and into the potato and it will gain weight.
However, if the solution has a lower concentration then the potato the water will go out of the potato through the membrane and into the solution as osmosis is the movement of water molecules from a high concentration gradient to a lower concentration. But, there is a chance that the solution has the same concentration gradient as the potato meaning that the water will freely move back and forth from each substance without the change of concentration.
Gatorade is an isotonic drink which contains similar concentrations of carbohydrates and glucose just like it is in the human body (Diabetes, 2015). This solution contains electrolytes to replace the ones lost during exercise. An electrolyte is a substance that contains freely moving ions which acts like an “electrically moving current” (Nordqvist, 2014). Every life form cannot live without electrolytes and in the human body sodium “(Na+), potassium (K+), calcium (Ca2+), bicarbonate (HCO3-, magnesium (Mg2+), chloride (C1-), hydrogen phosphate (HPO42-), and hydrogen carbonate (HCO3-)” (Nordqvist, 2014). Out of these seven chemicals Sodium and Potassium are in the Gatorade drink, meaning that this drink will replace those lost electrolytes and keep the cells in the isotonic state.
The energy drink Red Bull is also used in this experiment however this solution is hypertonic. This means that the solution contains higher levels of sugar and salt (Diabetes, 2015). Causing the solution within the cell to move across the semi-permeable membrane allowing each side to be equal, however this then dehydrates the cell. The hypotonic drink of this experiment is water (H2O) where the solution has a lower gradient of salt to the human body, allowing the solutes of the blood to slide through the membrane to equalise the solutions (Maccarthy, 2015).