Need some help with Cell Biology exam questions

[anguissette]

I need some help with answering these exam study questions today prior to the actual test. We're supposed to answer them before taking it as a sort of study guide. Answered all of them already, I just want to check if my answers are correct :) any number of answers is welcome.

1. Red blood cells precursor cells have genes that direct the biosynthesis of the red, oxygen-carrying pigment, hemoglobin. Do all your body’s other cells also contain the genes for hemoglobin? If your answer is yes, explain why the other cells do not have hemoglobin in them. If your answer is no, explain how the genes for hemoglobin that were present in the fertilized egg that developed into you, were lost from one or more types of your cells (i.e., from liver cells, or brain cells, or intestinal cells, or from all your body cells except red cells?).

2. Pure bilayer membranes are effectively impermeable to ions and large polar molecules, such as glucose, that cells require. How do such ions and molecules get into cells? What are the various classes of proteins that affect passive membrane permeability?

3. How would stopping the light-independent reactions of photosynthesis affect the light-dependent reactions?

4. Solutions of glucose having a concentration of 0.3M can be infused directly and safely into the bloodstream of hospital patients. Is the same true for 0.3M solutions of sodium chloride (NaCl)? Explain.

5. In the absence of specific carrier proteins, which of the following can diffuse readily across the plasma membrane of a cell? ATP, glucose, amino acids, fatty acids, water, gases, proteins, ions, polysaccharides, glycerol, hemoglobin, alcohol.

6. . In mitosis how are chromosomes arranged during metaphase, and what takes place immediately after metaphase? Don’t just name the phase; instead, describe specifically what happens. Are the resulting “daughter” cells diploid (containing a pair of each type of chromosome), or haploid (only one copy of each chromosome)?

7. Mitosis, according to the text, produces daughter cells that are genetically identical to the parent cell. What this statement mean? If all the cells in your body were produced by mitosis, does this mean that all your body cells are genetically identical to the fertilized egg that ultimately became you?

3.

[pinatubo]

1. Of course it is present in all the cells of your body. They are not just expressed because of limited transcription factors. Many cascades of reaction which includes a series of phosphorylation are needed before that particular gene for hemoglobin will be expressed. A set of genes may also regulate the expression of that hemoglobin gene.

2. They can enter in a passive manner by channel proteins. These are integral proteins which may either be ion-gated, voltage-gated or ligand-gated.

3. Light-independent reaction product is the fixated or reduced carbon dioxide which will eventually turn into glucose (which is only a side reaction right). Hindi kaya baliktad ang tanong. Dapat how will it affect the light-independent. Well, if the light-independent reation is stopped, NADPH and ATP won't be used for redusing CO2 and will be stocked in the stroma. And that may cause a negative feedback to stop the electron transport chain in the thylakoid membrane. just a guess hehe

4. Read on the Na-Glucose symport in the intestine. That may answer your question. This is done by your intestine to control absorption of glucose.

5. fatty acids, glycerol, H2O--not sure hehe

6. In mitosis (not meiosis), all the cells in every phase are in diploid stage (2 sets of chromosome). These diploid chromosomes are duplicated in the S phase prior to mitosis. When a chromosome duplicates, it will now look like "X". This consists of 2 chromatids (exact copies of each other) and connected at the centromere. It is in anaphase, that this duplicates separate. The daughter cells still have diploid number of choromosomes. They just contain half of the original nucleic material that the parent cell contained. These daughter cells will again duplicate its chromosome in S phase (of the interphase). And that's it. The cell cylce continues.It's better if you look for figures showing this cycle.


7. That statement is true. When an egg cell is fertilized, stem cells which are progenitor cells for tissue-specific cells will be formed. All of these cells contain the same set chromosomes present in the egg cell so they are all genetically-identical to the fertilized egg. When they turned into specialized cells, the genes that cater only to their specific function in your body will be transcrpted. And again this, is because transcription is controlled, by specific signals that only a particular tissue cell will receive. These signals will regulate transcription (thru transcription factors), activate kinases, etc.

....eto lang yung mga naalala ko.

god bless

[anguissette]

Thank you :)

I got 76 on the exam..sigh.. oh well. I wanted a lot higher, studied like crazy for so long..least we can drop one exam out of three to get the highest two...

[anguissette]

I found out though that osmolarity in certain areas like the intestine is different than from the bloodstream...but to partially answer the question, 0.9% NaCl is used to dilute the blood ~.~ if it's dilute it means you want an isotonic solution, so below that (0.3%) would be hypotonic and harmful to RBCs.