Plant Cell Organelles and Their Functions
January 20, 2014
Plant Cell Organelles and Their Functions
1. What is the interdependent relationship between mitochondria and other organelles?
Although cell-organelles can seem isolated from one another because of things like membrane barriers, there is a close relationship between them. Mitochondria can work as a kind of power house cell considering it uses ATP synthesis which helps in the energy currency of cells. Also other organelles help in mitochondria in maintaining its physical integrity and functionality. One example could be smooth Endoplasmic Reticulum supplies lipids (which are an essential structural element of the mitochondrial membrane) to mitochondria although the nucleus ensures delivery of specific proteins to the mitochondria which can be crucial for this specific organelle for their function and structure.
2. What are similarities and differences between the Golgi apparatus and the large central vacuole?
Vacuoles and Golgi bodies can share many similarities especially in their ability to store different biomolecules. Considering vacuoles can temporarily store a wide range of nutrients and waste material as well as other material for the purpose of transportation. Golgi bodies also store various materials such as lipids, polysaccharides, and proteins which allow these to be directed towards the final destinations. The main difference between these organelles is apparent when looking at the Golgi bodies, they may introduce many different modifications in each entity which is they store. Central vacuole does not share this characteristic.
3. What is the function of chloroplast? Include functions of stroma and grana.
Chloroplasts are what perform photosynthesis in plants. This means they help to synthesis the food in plants using solar energy. Chloroplasts contain thylakoids, these are quite often piled on top of one another. The stacks of thylakoids are known as grana that has many integral and peripheral membrane proteins and the chemicals that are required for the light reactions of photosynthesis which includes chlorophyll. Thylakoids are surrounded by the stroma which means that the inner liquid of the chloroplast which has all of the enzymes is required to secure the reaction known as “dark” in photosynthesis.
4. Explain the function of the smooth endoplasmic reticulum and rough endoplasmic reticulum. How are their functions similar to the nucleus? How are they different?
Rough endoplasmic is essential for protein synthesis while smooth endoplasmic reticulum mostly takes part in the synthesis of lipids. Although there could be key similarities between the endoplasmic reticulum and the nucleus such as participation in the synthesis of bio-molecules; the nucleus performs this in an indirect manner by sending messages to the endoplasmic reticulum and other organelles. Although the endoplasmic reticulum carries out this task itself directly.
5. Provide three unique chemical or physical properties of water. How are these properties useful to water movement in plant cells?
Characteristics of water can be considered extraordinary and can assist in its movement: (a) Water flows from its higher to lower concentration so; can enter from soil into the dry parts of plant. (b) Capillary movement may be shown by water because of which, when one molecule of water moves forward and sticks to a surface (in plant) then it pulls on other water molecules too. (c) Hydrogen bonds may be formed by water molecules that strengthen the linkage between them and thus assist in their movement.
6. Discuss similarities and differences between bulk flow and diffusion. What are driving forces behind each process?
Both diffusion and bulk flow are required for the principle of water movement, but diffusion signifies net progressing down a concentration gradient because of the indiscriminate movement of distinct molecules while, majority flow involves moving the water along with solutes jointly owing to a pressure gradient
7. Describe Fick’s law. How might this law be applied to osmosis? Explain how osmosis is a special case of diffusion.
Fick’s Law states that:
Diffusion α surface area x concentration difference
This law can also be applied in the case of osmosis since; osmosis is the procedure through which water molecules may diffuse through a semi- permeable membrane from an area that has a higher water capacity to an area that has a lower water capacity or from their higher concentration to lower concentration.
8.What role does solute concentration play in osmosis? How does water’s chemical potential influence osmosis? What role do water properties play in diffusion?
The net direction of osmosis depends on relative concentration of solutes present on two sides of membrane. Therefore; if a solution present at one side is hypotonic to solution present at another side of semi-permeable membrane then exo-osmosis would occur and vice-versa. If pure water is in contact with both sides of semi-permeable membrane then there could not be identified net flow of water across the membrane due to equal chemical potential while, if the two sides of membrane reflect variation in “chemical potentials” then Osmotic flow can occur from higher to lower chemical potential until the restoring of equilibrium in terms of chemical potential. Water supports diffusion via providing favorable circumstances for movement of solute molecules that occurs from higher to lower concentration of solute. In fact, rate of diffusion also depends on the medium through which the substance diffuses and water is called an ideal medium for the process.
9. Distinguish between osmotic pressure and potential. What organelle is related to osmotic potential?
Osmotic pressure can be described as the pressure that is applied by a solution to limit the internal flow of water through a semi-permeable membrane. Osmotic potential can be described as the opposite of water potential. This means that the extent that a solvent can have to exist in a liquid. Vacuoles can be closely related with the osmotic potential considering they can accumulate and remove Na+ and Cl–to balance the osmotic effects.
10. What role do aquaporins play in cell membrane permeability? What controls the gating of aquaporins?
Aquaporins can form tetramers in cell membrane, and may assist in the transportation of water (and other tiny solutes) across the membrane. Their gating might be carried out by an interaction between them and gating mechanism that may lead towards alteration in their 3- dimensional structure and can ultimately block the pore because of which, flow of water by it can be discontinued. For example; in plants such gating is regulated by dephosphorylation of a few particular serine residues in response to drought, and protonation of few definite histidine residues in reply to flooding.