Question

4. Describe a reason why there is a constraint on cell size. 1 pt In that context, explain how eukaryotic cells are able to be 10Xlarger than prokaryotic cells. 1 pt 5. Consider a eukaryotic cell making two different proteins: one protein functions within the mitochondria and the other is secreted outside of the cell. The genes encoding the two proteins are transcribed and the two types of mRNA are released into the cytoplasm for translation How will the production of the two proteins be similar? 1 pt In what way will the protein production be different for the two proteins? 2 pts 6. Circle any statement that reflects how prokaryotic and cukaryotic cells differ. 1 pt a. Eukaryotic cell membranes are made up of phospholipid bilayers whereas prokaryotic cell membranes are made up of phospholipid monolayers b. Some eukaryotic cells are large enough to be seen without a microscope whereas all prokaryotic cells are microscopic. c. Eukaryotic chromosomes are linear whereas prokaryotic chromosomes are circular d. Eukaryotic chromosomes are made up of double-stranded DNA whereas prokaryotic chromosomes are made up of single-stranded DNA e. Eukaryotic cells contain multiple types of plasmids whereas prokaryotic cells only contain one ype of plasmid

Answer 1

4. One reason to decribe why cell size matters is that the basic processes of cell physiology, such as flux across membranes, are by their nature dependent on cell size. As a result, changes in cell volume or surface area will have profound effects on metabolic flux, biosynthetic capacity, and nutrient exchange.

The basic machinery of cell division in eukaryotes relies on microtubules, both to form the mitotic spindle and position it properly relative to the cortex. Because of the dynamic properties of microtubules, they are able to probe a limited range of lengths, and if cells get too big or too small, the mitotic apparatus may have difficulty working. Very small cells could not form a proper spindle, and very large cells could not coordinate their divisions during cleavage. So there is the apparent upper and lower limits on cell size with respect to cell division machinery. Specifically, bacteria adopt certain sizes and shapes so they can import nutrients most efficiently, meet requirements imposed by cell division, attach themselves to external surfaces, take advantage of passive dispersal mechanisms, move purposefully to pursue nutrients or avoid inhibitors, or avoid predation by other organisms.  Therefore, most bacteria produce cells in the 0.2 to 10 μm size range.

Differences in cellular structure of prokaryotes and eukaryotes include the presence of mitochondria and chloroplasts, the cell wall, and the structure of chromosomal DNA. This means that the eukaryotic cell must be larger to hold all of it's organelles. Therefore, due to evolution, the size of eukaryotic cells are able to be 10x larger than prokaryotic cells.

5. Most mitochondrial proteins are translated on free cytosolic ribosomes and imported into the organelle by specific targeting signals. In addition, mitochondria are unique among the cytoplasmic organelles as they contain their own DNA, which encodes tRNAs, rRNAs, and some mitochondrial proteins. The assembly of mitochondria thus involves proteins encoded by their own genomes and translated within the organelle, as well as proteins encoded by the nuclear genome and imported from the cytosol. But, in the cytoplasm, Ribosomes are the large complexes of protein and ribonucleic acid (RNA), are the cellular organelles responsible for protein synthesis. They receive their “orders” for protein synthesis from the nucleus where the DNA is transcribed into messenger RNA (mRNA). This mRNA travels to the ribosomes, which translate the code provided by the sequence of the nitrogenous bases in the mRNA into a specific order of amino acids in a protein. Therefore, the production of both kind of protiens are similar as they are guided/encoded by the neuclear genome. The production of both kind of protiens are different too as the mitochondria contain their own DNA, which encodes tRNAs, rRNAs, and some mitochondrial proteins. As we know that the assembly of mitochondria thus involves proteins encoded by their own genomes and translated within the organelle, as well as proteins encoded by the nuclear genome and imported from the cytosol.

6. c.

A prokaryotic chromosome is circular and resides in a cell region called the nucleoid. Prokaryotic chromosome contains a covalently closed circular DNA (cccDNA). Each eukaryotic chromosome contains a linear DNA with two ends. Chromosome occupies freely in the center of the cell and not covered by the nucleus.