Comparing Prokaryotic and Eukaryotic Cells

Comparing Fields and Methods First, let's recap the original motivation for using methods to hide fields. Consider the following struct that represents a position on a screen as an (X, Y) coordinate pair: struct ScreenPosition { public ScreenPosition(int x, int y) { this.X = rangeCheckedX(x); this.Y = rangeCheckedY(y); } public int X; public int Y; private static int rangeCheckedX(int x) { if (x < 0 || x > 1280) { throw new ArgumentOutOfRangeException("X"); } return x; } private static int rangeCheckedY(int y) { if (y < 0 || y > 1024) { throw new ArgumentOutOfRangeException("Y"); } return y; } } The problem with this struct is that it does not follow the golden rule of encapsulation; it does not keep its data private. Public data is a bad idea because its use cannot be checked and controlled. For example, the ScreenPosition constructor range checks its parameters, but no such check can be done on the “raw” access to the public fields. Sooner or later (probably sooner), either X or Y will stray out of its range, possibly as the result of a programming error: ScreenPosition origin = new ScreenPosition(0, 0); . int xpos = origin.X; origin.Y = -100; // Oops The common way to solve this problem is to make the fields private and add an accessor method and a modifier method to respectively read and write the value of each private field. The modifier methods can then range-check the new field values because the constructor already checks the initial field values. For example, here's an accessor (GetX) and a modifier (SetX) for the X field. Notice how SetX checks its parameter value: struct ScreenPosition { . public int GetX() { return this.x; } public void SetX(int newX) { this.x = rangeCheckedX(newX); } . private static int rangeCheckedX(int x) { . } private static int rangeCheckedY(int y) { . } private int x, y; } The code now successfully enforces the range constraints, which is good. However, there is a price to pay for this valuable guarantee—ScreenPosition no longer has a natural field- like syntax; it uses awkward method-based syntax instead. The following example increases the value of X by 10. To do so, it has to read the value of X by using the GetX accessor method, and then write the value of X by using the SetX modifier method: int xpos = origin.GetX(); origin.SetX(xpos + 10); Compare this with the equivalent code if the X field were public: origin.X += 10; There is no doubt that, in this case, using fields is cleaner, shorter, and easier. Unfortunately, using fields breaks encapsulation. Properties allow you to combine the best of both examples: to retain encapsulation while allowing a field-like syntax. Comparing Prokaryotic and Eukaryotic Cells Comparing Prokaryotic and Eukaryotic Cells Bởi: OpenStaxCollege Cells fall into one of two broad categories: prokaryotic and eukaryotic The predominantly single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes (pro- = before; -karyon- = nucleus) Animal cells, plant cells, fungi, and protists are eukaryotes (eu- = true) Components of Prokaryotic Cells All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; 3) DNA, the genetic material of the cell; and 4) ribosomes, particles that synthesize proteins However, prokaryotes differ from eukaryotic cells in several ways A prokaryotic cell is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle We will shortly come to see that this is significantly different in eukaryotes Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid ([link]) This figure shows the generalized structure of a prokaryotic cell 1/4 Comparing Prokaryotic and Eukaryotic Cells Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule ([link]) The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration The capsule enables the cell to attach to surfaces in its environment Some prokaryotes have flagella, pili, or fimbriae Flagella are used for locomotion Pili are used to exchange genetic material during a type of reproduction called conjugation Fimbriae are protein appendages used by bacteria to attach to other cells Eukaryotic Cells In nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells The principle “form follows function” is found in many contexts For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched A eukaryotic cell is a cell that has a membrane-bound nucleus and other membranebound compartments or sacs, called organelles, which have specialized functions The word eukaryotic means “true kernel” or “true nucleus,” alluding to the presence of the membrane-bound nucleus in these cells The word “organelle” means “little organ,” and, as already mentioned, organelles have specialized cellular functions, just as the organs of your body have specialized functions Cell Size At 0.1–5.0 µm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10–100 µm ([link]) The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell Similarly, any wastes produced within a prokaryotic cell can quickly move out However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport Indeed, the large size of these cells would not be possible without these adaptations In general, cell size is limited because volume increases much more quickly than does cell surface area As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area through which materials must be transported declines 2/4 Comparing Prokaryotic and Eukaryotic Cells This figure shows the relative sizes of different kinds of cells and cellular components An adult human is shown for comparison Section Summary Prokaryotes are predominantly single-celled organisms of the domains Bacteria and Archaea All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles Many also have polysaccharide capsules Prokaryotic cells range in diameter from 0.1–5.0 µm Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membranebound organelles that allow for compartmentalization of functions Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells Multiple Choice Which of these all prokaryotes and eukaryotes share? nuclear envelope cell walls organelles plasma membrane D 3/4 Comparing Prokaryotic and Eukaryotic Cells A typical prokaryotic cell compared to a eukaryotic cell is smaller in size by a factor of 100 is similar in size is smaller in size by a factor of one million is larger in size by a ... Comparing Server and Client Validations Consider the EmployeeForm.aspx page of the Honest John Web site again. The user is expected to enter the details of an employee: name, employee ID, position, and role. All the text boxes should be mandatory. The employee ID should be a positive integer. In a Windows Forms application, you would use the Validating event to ensure the user typed something into the First Name and Last Name text boxes and that the employee ID value was numeric. Web forms do not have a Validating event, which means that you cannot use the same approach. Server Validation If you examine the TextBox class, you will notice that it publishes the TextChanged event. This event runs the next time the form is posted back to the server after the user changes the text typed in the text box. Like all Web Server control events, the TextChanged event runs at the Web server. This action involves transmitting data from the Web browser to the server, processing the event at the server to validate the data, and then packaging up any validation errors as part of the HTML response sent back to the client. If the validation being performed is complex, or requires processing that can only be performed at the Web server (such as ensuring that an Employee ID the user types in exists in a database) , this might be an acceptable technique. But if you are simply inspecting the data in a single text box in isolation (such as making sure that the user types a positive integer into an Employee ID text box), performing this type of validation of the Web server could impose an unacceptable overhead; why not perform this check in the browser on the client computer and save a network round-trip? Client Validation The Web Forms model provides for client-side validation through the use of validation controls. If the user is running a browser such as Microsoft Internet Explorer 4 or later, which supports dynamic HTML, these controls generate JavaScript code that runs in the browser and avoids the need to perform a network round-trip to the server. If the user is running an older browser, the validation controls generate server-side code instead. The key point is that the developer creating the Web form does not have to worry about this; all the browser detection and code generation features are built into the validation controls. The developer simply drops a validation control onto the Web form, sets its properties (by using either the Properties window or code), and specifies the validation rules to be performed and any error messages to be displayed. There are five types of validation controls supplied with ASP.NET: • RequiredFieldValidator Use this control to ensure that the user has entered data into a control. • CompareValidator Use this control to compare the data entered against a constant value, the value of a property of another control, or a value retrieved from a database. • RangeValidator Use this control to check the data entered by a user against a range of values, checking that the data falls either inside or outside a given range. • RegularExpressionValidator Use this control to check that the data input by the user matches a specified regular expression, pattern, or format (such as a telephone number, for example). NOTE You should be aware that if a user can type unrestricted text into a text box and send it to the Web server, they could type text that looks like HTML tags (<b> for example). Hackers sometimes use this technique to inject HTML into a client request in an attempt to cause damage to the Web server, or to try and break in (I am not going to go into the details here!). By default, if you try this trick with an ASP.NET Web page the request will be aborted and the user is shown the message “A potentially dangerous Request.Form Prokaryotic and Eukaryotic Cells Structure and Function In general microbes or microorganisms may be either prokaryotic (bacteria) or eukaryotic (protists, fungi, and some animals). However, there are some microbial organisms that appear to be intermediates between prokaryotes and eukaryotes (they possess a nucleus but do not have mitochondria or chloroplasts, an example is Giardia intestinalis. Prokaryotes differ from eukaryotes in several ways including but not limited to: Characteristics Prokaryotic Eukaryotic Types bacteria (monerans) protists, fungi, plants, and animals Organization unicellular usually multicellular (exception some protists) Cell size small (0.1-10um) larger (10-100um) Membrane-bound organelles absent present Reproduction asexual asexual and sexual DNA circular linear Proteins assoc. with DNA Basic Histone Plasma membrane No sterols Sterols Ribosomes 70S 80S Cytoskeleton Absent present PROKARYOTIC CELLS [...]... are dormant structures produced by some species of Bacillus and Clostridium Shapes and arrangements of bacteria There are six common shapes of bacteria: coccus, bacillus, coccobacillus, vibrio, spirochete, and spirullum and there are several arrangements of these cells: single, chains (strepto-), clusters (staphylo-), pairs (diplo-) etc Eukaryotic Cell Cell Membrane Cell membrane Structure Components... and synthetic processes The following are found within the protoplasm of the prokaryotic cell: chromatin body or the bacterial chromosome nucleoid or nuclear region of the cell that is associated with the chromatin body plasmids are tiny circular extrachromosomal strands of DNA ribosomes are small structures consisting of RNA and proteins that are involved in protein synthesis inclusions or granules... and active transport) Recognition (e.g., self vs non-self) Reception (for protein hormones) Adhesion Nucleus Structure and Function – membrane similar to cell membrane (similar function) – Nucleolus (formation of ribosomes) – Chromosomes (gene expression) – Nucleoplasm (matrix) Ribosomes • Structure – rRNA – Proteins • Function – Site of protein formation (translation) • Found in both prokaryotes and. .. primary dye) and Gram - bacteria stain pink (the color of the counterstain or second dye) The Gram stain is a differential staining technique because different species of bacteria stain differently The difference is a result of the composition of the cell wall The protoplasm or cytoplasm is the dense gelatinous solution within the cell membrane that is the primary site for the cell’s biochemical and synthetic... layer (outermost layer) differs greatly in thickness, organization and chemical composition depending on the bacterial species T Beneath the outer layer lies the cell wall The cell membrane is a thin flexible sheet that surrounds the contents of the bacterial cell Its functions include: transport, energy extraction, nutrient processing, and synthesis The Gram Stain An important tool in the identification... structurally) Endoplasmic Reticulum • Structure membranous system of tunnels and sacs – Rough – with ribosomes on surface – Smooth- no ribosomes on surface • Function – Rough – protein synthesis – Smooth- lipid synthesis Golgi Apparatus • Structure also membranous, kind of like a stack of pancakes • Function processing of lipids and proteins Lysosomes • Structure membrane bound sac containing hydrolytic... Energy transfer by ATP synthesis Chloroplast • Structure – Also cigar or spindle shaped, double membrane-bound, green • Function – Site of photosynthesis OTHER STUCTURES • • • • Cell walls, not in animal cells Prokaryotic Cells Vs. Prokaryotic Cells Vs. Eukaryotic Cells Eukaryotic Cells Now that we have learned how living Now that we have learned how living things are organized what’s next? things are organized what’s next?  We will learn more about the lowest level of We will learn more about the lowest level of organization: cells organization: cells What is the first thing that we need to know about What is the first thing that we need to know about cells? cells?  All cells fall into one of the two major classifications All cells fall into one of the two major classifications of either prokaryotic or eukaryotic. of either prokaryotic or eukaryotic. [...]... called them cells He used this name because it reminded him of little rooms that monks lived in Matthias Schleiden  First to see living plant cells and determined that plants are also made of these tiny structures called cells Theodor Schwann  Viewed animal tissue and concluded that animals are also made of these tiny structures called cells Rudolf Virchow  He was the scientist that said cells can... structures called cells Rudolf Virchow  He was the scientist that said cells can only be produced by other living cells The Cell Theory 1 2 3 All Organisms are composed of one or more cells The cell is the basic unit of structure and organization of organisms All cells come from other living cells Cells Organelles are membrane-bound cell parts   Mini “organs” that have unique structures and functions... unicellular  Cells are smaller in size  Cells are larger in size  Has larger number of organisms  Has smaller number of organisms How do the differences line up? Prokaryotes  Appeared 4 billion years ago Eukaryotes  Appeared 1 billion years ago How do the similarities line up? Lets See!!!     Both types of cells have cell membranes (outer covering of the cell) Both types of cells have ribosomes...What do prokaryotic cell look like? Now let’s take a look at the characteristics of eukaryotes  Eukaryotic cells appeared approximately one billion years ago  Eukaryotes are generally more advanced than prokaryotes  Nuclear membrane surrounds linear genetic... eukaryotes have several different parts  Prokaryote’s organelles have coverings known as membranes  Eukaryotes have a complex internal structure  Eukaryotes are larger than prokaryotes in size What do eukaryotic cells look Mitochondria like? Nucleus Cytoplasm Golgi Complex Endoplasmic Reticulum Cell Membrane How do the differences line up? Prokaryotes  Organelles lack a membrane  Ribosomes are the only... billion years ago How do the similarities line up? Lets See!!!     Both types of cells have cell membranes (outer covering of the cell) Both types of cells have ribosomes Both types of cells have DNA Both types of cells have a liquid environment known as the cytoplasm  Your turn: Make a Venn Diagram outlining the similarities and differences between prokaryotes and eukaryotes  You may use your book... may use Analysis and biological relevance of advanced glycation end-products of DNA in eukaryotic cells Viola Breyer 1, *, Matthias Frischmann 1, *, Clemens Bidmon 1 , Annelen Schemm 2 , Katrin Schiebel 2 and Monika Pischetsrieder 1 1 Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Germany 2 Institute for Biochemistry, University of Erlangen-Nuremberg, Germany Sugars and other reactive carbonyl compounds bind spontaneously to nucleophilic amino groups of amino acids and proteins in a nonenzymatic process (glyca- tion) [1]. It is well established that proteins are readily glycated in vivo. The first glycation product to be detected in vivo was hemoglobin (Hb) A 1c , the Amadori product of Hb A [2]. Hb A 1c is now an established clini- cal marker for medium-term hyperglycemia in diabetic patients. In vivo, early glycation products, such as the Amadori product, are further converted into the hetero- geneous group of advanced glycation end-products (AGEs). AGEs accumulate on serum proteins and in various tissues, particularly during aging, diabetes, and renal failure [3]. Elevated AGE levels contribute to the development of diabetic and uremic complications, such as atherosclerosis [4], nephropathy, and retinopathy [5]. In analogous reactions, glycation may also affect DNA. In vitro, nucleobases and dsDNA react with Keywords advanced glycation end-products; DNA; eukaryotic cells; Maillard reaction; N 2 -carboxyethyl-2¢-deoxyguanosine Correspondence M. Pischetsrieder, Department of Chemistry and Pharmacy, Henriette Schmidt-Burkhardt Chair of Food Chemistry, Schuhstr. 19, 91052 Erlangen, Germany Fax: +49 9131 8522587 Tel: +49 9131 8524102 E-mail: pischetsrieder@lmchemie. uni-erlangen.de Website: http://www.lebensmittelchemie. pharmazie.uni-erlangen.de *These authors contributed equally to this work (Received 23 October 2007, revised 17 December 2007, accepted 19 December 2007) doi:10.1111/j.1742-4658.2008.06255.x Advanced glycation end-products (AGEs) of DNA are formed spontane- ously by the reaction of carbonyl compounds such as sugars, methylglyoxal or dihydroxyacetone in vitro and in vivo. Little is known, however, about the biological consequences of DNA AGEs. In this study, a method was developed to determine the parameters that promote DNA glycation in cultured cells. For this purpose, the formation rate of N 2 -carboxyethyl-2¢- deoxyguanosine (CEdG), a major DNA AGE, was measured in cultured hepatic stellate cells by liquid chromatography (LC)-MS ⁄ MS. In resting cells, a 1.7-fold increase of CEdG formation rate was observed during 14 days of incubation. To obtain insights into the functional consequences of DNA glycation, CEdG was introduced into a luciferase reporter gene vector and transfected into human embryonic kidney (HEK 293 T) cells. Gene activity was determined by chemiluminescence of the luciferase. Thus, CEdG adducts led to a dose-dependent and highly significant decrease in protein activity, which is caused by loss of functionality of the luciferase in addition to reduced transcription of the gene. When the CEdG-modified vector was transformed into Escherichia coli, a loss of ampicillin resistance was observed in comparison to transformation with the unmodified plas- mid. These results indicate that CEdG accumulates in the genomic DNA of resting cells, which could lead to diminished protein activity. Abbreviations AGE, advanced glycation end-product; CEdG, N 2 -carboxyethyl-2¢-deoxyguanosine; DAD, diode array .. .Comparing Prokaryotic and Eukaryotic Cells Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a... prokaryotes and eukaryotes share? nuclear envelope cell walls organelles plasma membrane D 3/4 Comparing Prokaryotic and Eukaryotic Cells A typical prokaryotic cell compared to a eukaryotic. .. materials must be transported declines 2/4 Comparing Prokaryotic and Eukaryotic Cells This figure shows the relative sizes of different kinds of cells and cellular components An adult human is