Hey
I have a sac coming up on osmosis and here are the key concepts we need to know:
• Draw and label fluid mosaic model of the plasma membrane
• What are the functions of all its components in the plasma membrane?
• Define and give an example of Diffusion
• Define and give an example of Osmosis
• Define and give an example of Facilitated diffusion
• Define and give an example of Active transport
• Identify the differences between all modes of transport
• Define and understand hypertonic, hypotonic and isotonic.
• What can/cannot readily pass through the cell membrane
• Define and understand the terms hydrophobic and hydrophilic.
It would be awesome if someone could answer a couple and I could compare it with my answers. I want my answers to be perfect and include all the important stuff
Thanks in advance
The role of the phospholipid membrane in general is to control the inputs and outputs in a cell. The carbohydrate chains (glycoproteins and glycolipids) are involved in intercellular communication and also recognises self and non-self (foreign substances). Cholesterol increases fluidity and prevents solidification of the membrane at low temperatures. The protein channels enable ions (charged particles) and large hydrophilic substances to diffuse through the membrane and is also involved in active transport (the energy-requiring passage of molecules against the concentration gradient). The pores between the phospholipids allow small uncharged and lipophilic substances such as alcohol and urea to diffuse through.
Diffusion is the net movement of solutes from a region of high solute concentration to a region of low solute concentration along a concentration gradient until equilibrium is reached. For example, when you add food colouring to water, the water will eventually be coloured as the colouring will diffuse to the clear regions (where the concentration of the food colouring is low) hence making the whole water solution coloured.
Osmosis is the net movement of water molecules from a region of high water potential (low solute concentration) to a region of low water potential (high solute concentration) along the osmotic gradient. For example, imagine a frog in a pond; if the pond has a lot of salt dissolved in it- it is hypertonic to the frog and water will therefore diffuse out of the frog possibly making it burst. This is because the cells in our body are semi-permeable- solutes cannot exist easily therefore water diffuses to make the two mediums reach equilibrium. Note that osmosis is a form of passive transport or in other words does not require energy.
Facilitated diffusion is the net movement of solutes along a concentration from an area of high solute concentration to an area of low solute concentration with the aid of protein channels. For example, sodium ions require protein channels as they cannot "simply" diffuse through the membrane.
Active transport is the net movement of solutes from an area of low solute concentration to an area of high solute concentration AGAINST the concentration gradient. This requires an expenditure of energy and is highly important for cells. For example, the roots of plants require active transport to absorb ions in the soil- this is because there is already a higher concentration of ions in the roots so energy is required. Energy that is used in active transport must be in the form of ATP (chemical energy) which is produced by the mitochondria in the cells.
Passive transport includes facilitated diffusion, simple diffusion and carrier mediated transport. It requires no energy as solutes are being diffused along the concentration gradient. In contrast, active transport requires energy as the solutes must be taken up against the concentration gradient.
Small uncharged particles, volatile substances and lipophilic molecules such as alcohol, urea, water, ethanol can readily pass through the membrane whereas hydrophilic polar substances such as sodium cannot- they require protein channels. Larger molecules are taken into the cell via endocytosis whereby the cell membrane simply engulfs the substances such as food and forms a vesicle in the cell.
Hydrophilic literally means water loving --> hydro - water and philic - loving
Hydrophobic means water fearing --> hydro - water and phobic - fearing
Forgot to mention, when a solution is isotonic to another solution, this means that they have the same solute concentration therefore diffusion is occurring at a constant rate between the two mediums.
Also endocytosis and exocytosis are other forms of transport as well. Exocytosis is the opposite of endocytosis whereby large particles exits the cell - the vesicles fuses with the membrane and releases its contents. This is common with lysosomes.
Hope this helped and please correct me if I'm wrong