Thursday, 7 January 2016

Experienced Cell Biology Interview Questions and Answers

31. What are the main components of the cytoskeleton?
The cytoskeleton is a network of very small tubules and filaments distributed throughout the cytoplasm of eukaryotic cells. It is made of microtubules, microfilaments and intermediate filaments.
Microtubules are formed by molecules of a protein called tubulin. Microfilaments are made of actin, the same protein that participates in the contraction of muscle cells. Intermediate filaments are made of protein too.
Cell Structure Review - Image Diversity: cytoskeleton

32. What are the functions of the cytoskeleton?
As the name indicates, the cytoskeleton is responsible for the supporting of the normal shape of the cell; it also acts as a facilitator for substance transport across the cell and for the movement of cellular organelles. For example, the sliding between actin-containing filaments and the protein myosin creates pseudopods. In cells of the phagocytic defense system, like macrophages, cytoskeleton is responsible for the plasma membrane projections that engulf the external material to be interiorized and attacked by the cell.

33. What are chloroplasts? What is the main function of chloroplasts?
Chloroplasts are organelles present in the cytoplasm of plant and algae cells. Likewise mitochondria, chloroplasts have two boundary membranes and many internal membranous sacs. Within the organelle there are own DNA, RNA and ribosomes and also the pigment chlorophyll, responsible for absorption of photic energy that is used in photosynthesis.
The main function of chloroplasts is photosynthesis: the production of highly energetic organic molecules (glucose) from carbon dioxide, water and light.
Cell Structure Review - Image Diversity: chloroplasts

34. What is the molecule responsible for the absorption of photic energy for photosynthesis? Where is that molecule located in photosynthetic cells?
The chlorophyll molecules are the responsible for the absorption of the light energy for photosynthesis. These molecules are found on the internal membranes of chloroplasts.

35. What are the colors (of the electromagnetic spectrum) absorbed by plants? What would happen to photosynthesis if the green light waves that reach a vegetable were blocked?
Chlorophyll absorbs all other colors of the electromagnetic spectrum but it practically does not absorb the green. The green color is reflected and such reflection provides the characteristic color of plants. If the green light that reaches a plant is blocked and the exposition of the plant to other colours is maintained there would be no harm for photosynthesis. Apparent paradox: the green light is not important for photosynthesis.
There is difference between the optimun color frequency for the two main types of chlorophyll, the chlorophyll A and the chlorophyll B. Chlorophyll A has an absorption peak in approximately 420 nm wavelenght (anil) and chlorophyll B has its major absorption in 450 nm wavelenght (blue).
Cell Structure Review - Image Diversity: electromagnetic spectrum

36. What is the way followed by the energy absorbed by plants to be used in photosynthesis?
The energy source of photosynthesis is the sun, the unique and central star of our planetary system. In photosynthesis the solar energy is transformed into chemical energy, the energy of the chemical bonds of the produced glucose molecules (and of the released molecular oxygen). The energy of glucose then is stored as starch (a glucose polymer) or it is used in the cellular respiration process and transfered to ATP molecules. ATP is consumed in metabolic processes that spend energy (for example, in active transport across membranes).

37. what substance the plant cell wall is made? Is that substance a polymer made of which monomer?
The plant cell wall is made of cellulose. Cellulose is a polymer whose monomer is glucose. There are other polymers of glucose, like glycogen and starch.
Cell Structure Review - Image Diversity: plant cell wall

38. What is the function of the plant cell wall?
The plant cell wall has structural and protective functions. It plays important role in the constraint of the cell size, preventing the cell to break when it absorbs much water.

39. What are plant cell vacuoles? What are their functions? How is the covering membrane of the vacuoles called?
Plant cell vacuoles are cell structures delimited by membranes within which there is an aqueous solution made of several substances like carbohydrates and proteins. In young plant cells many small vacuoles can be seen; within adult cells the most part of the internal area of the cell is occupied by a central vacuole.
The main function of the vacuoles is the osmotic balance of the intracellular space. They act as “an external space” inside the cell. Vacuoles absorb or release water in response to the cellular metabolic necessities by increasing or lowering the concentration of osmotic particles dissolved in the cytosol. Vacuoles also serve as storage place for some substances.
The membrane that delimits the vacuoles is called tonoplast, named after the osmotic function of the structure.

40. What is a membrane?
Membrane is any delicate sheet that separates one region from other blocking or permitting (selectively or completely) the passage of substances. The skin, for example, can be considered a membrane that separates the exterior from the interior of the body; cellophane, used in chemical laboratories to separate solutions, acts as membrane too.

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