91. List 2 differences between DNA and RNA. 92. Where do the following processes
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91. List 2 differences between DNA and RNA. 92. Where do the following processes occur in a cell? DNA replication Translation 93. State the functions of the following enzymes: DNA polymerase RNA polymerase Helicase 94. Where do the following processes take place in a cell? Glycolysis Transition reaction Citric Acid cycle Electron transport chain 95. How many ATP's are produced by aerobic respiration? 96. What is the role of NADH and FADH2 in aerobic respiration? 97. List 2 characteristics of cancer cells. 98. List 2 methods by which genes can be cloned. 99. What is competitive inhibition? 100. Proto-oncogenes code for proteins that suppressor genes code for proteins that cell division. cell division while tumorExplanation / Answer
91. Differences between DNA and RNA are listed below:
a) DNA is a long polymer with deoxyriboses and phosphate backbone, having four different nitrogenous bases: adenine, guanine, cytosine and thymine.
Whereas, RNA is a polymer with a ribose and phosphate backbone, having four different nitrogenous bases: adenine, guanine, cytosine, and uracil. (https://en.wikibooks.org/wiki/Structural_Biochemistry/Nucleic_Acid/Difference_between_DNA_and_RNA)
b) DNA is a double-stranded molecule while RNA is a single stranded molecule. (https://www.thoughtco.com/dna-versus-rna-608191)
c) DNA is responsible for storing and transferring genetic information while RNA directly codes for amino acids and as acts as a messenger between DNA and ribosomes to make proteins. (https://www.thoughtco.com/dna-versus-rna-608191)
d) The helix geometry of DNA is of B-Form. DNA is completely protected by the body i.e. the body destroys enzymes that cleave DNA. DNA can be damaged by exposure to Ultra-violet rays.
Whereas, The helix geometry of RNA is of A-Form. RNA strands are continually made, broken down and reused. RNA is more resistant to damage by Ultra-violet rays. (https://en.wikibooks.org/wiki/Structural_Biochemistry/Nucleic_Acid/Difference_between_DNA_and_RNA)
92. - DNA replication is the process by which DNA makes a copy of itself during cell division (https://www.yourgenome.org/facts/what-is-dna-replication) or DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule . This process occurs in all living organisms and is the basis for biological inheritance. (https://en.wikipedia.org/wiki/DNA_replication). DNA Replication takes place in the 'Nucleus of Eukaryotic cell' and in 'Cytoplasm of Prokaryotic cell' (as Prokaryotes lack nucleus).
- Transcription is a process in which the DNA is transcribed into mRNA and is important part of the protein synthesis process. Eukaryotic cells are facilitated with the nucleus, and they can have one or more nucleus, which contains the genetic materials such as DNA and RNA. These materials actively participate in the process of protein synthesis, which takes place inside the nucleus, and subsequently, mRNA is formed. Then the transcribed mRNA comes out of the nucleus pores into the cytoplasm. The translation takes place, and thus, completes the process of protein synthesis.
In case of prokaryotics, transcription takes place in th cytoplasm. (https://biologywise.com/where-does-transcription-occur)
- Translation refers to the process of creating proteins from an mRNA template. The sequence of nucleotides on the RNA is translated into the amino acid sequence of proteins and this reaction is carried out by ribosomes. (https://biologydictionary.net/translation/)
In prokaryotes; e.g. bacteria, translation occurs in the cytoplasm, where the large and small subunits of the ribosomebind to the mRNA. In eukaryotes, translation occurs in the cytosol or across the membrane of the endoplasmic reticulum in a process called co-translational translocation. In co-translational translocation, the entire ribosome/DNA complex binds to the outer membrane of the rough endoplasmic reticulum (ER) and the new protein is synthesized and released into the cytosol; the newly created polypeptide can be stored inside the ER for future vesicle transport and secretion outside the cell, or immediately secreted.(https://en.wikipedia.org/wiki/Translation_(biology).
93. Function of following enzymes:
----DNA Polymerase: An enzyme assisting in DNA replication. DNA polymerases are those that are involved in template-directed synthesis of DNA fromdeoxyribonucleotide triphosphates. They are used to assemble DNA molecules by copying a template strand of DNA according to base-pairing interactions. They usually work in pairs so that two new identical strands of DNA are produced from a single strand of the parent DNA molecule. (https://www.biology-online.org/dictionary/DNA_polymerase)
----RNA Polymerase: RNA polymerase (RNAP or RNApol) is an enzyme that is responsible for making RNA from a DNA template. In all cells RNAP is needed for constructing RNA chains from a DNA template, a process termed transcription. RNAP is a nucleotidyl transferase that polymerizes ribonucleotides at the 3' end of an RNA transcript. RNA polymerase enzymes are essential and are found in all organisms, cells, and many viruses. (https://www.biology-online.org/dictionary/RNA_polymerase)
----Helicases: An enzyme that utilizes energy from nucleoside triphosphate (e.g. ATP) hydrolysis in order to unwind the two annealed nucleic acidstrands (e.g. DNA). (https://www.biology-online.org/dictionary/Helicase). The helicaseunwinds the DNA molecule resulting in a replication fork, thus, allowing the DNA polymerases to read the strands for use as templates. DNA polymerases add free nucleotides to the 3' end of the newly forming strand. As a result, the new strand elongates in a 5'? 3' direction. (https://www.biology-online.org/dictionary/DNA_polymerase).
94. --Glycolysis: Glycolysis can be defined as the sequence of reactions for the breakdown of Glucose (6-carbon molecule) to two molecules of pyruvic acid (3-carbon molecule) under aerobic conditions; or lactate under anaerobic conditions along with the production of small amount of energy. Glycolysis takes place in the Cytoplasm of the cell. (https://laboratoryinfo.com/glycolysis-steps-diagram-energy-yield-and-significance/)
---Transition Reaction: Transition Reaction is also called Oxidative Decarboxylation. It takes place in the matrix of the mitochondria. The Transition Reaction converts the two molecules of the 3-carbon pyruvate from glycolysis into two molecules of the 2-carbon molecule acetyl Coenzyme A (acetyl-CoA) (http://cellular-respiration.tripod.com/id3.html). The transition reaction links glycolysis to the citric acid (Krebs) cycle.
---Citric Acid Cycle: The citric acid cycle (CAC) – also known as the tricarboxylic acid (TCA) cycle or the Krebs cycle– is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoAderived from carbohydrates, fats, and proteins into carbon dioxide and chemical energy in the form of adenosine triphosphate (ATP). (https://en.wikipedia.org/wiki/Citric_acid_cycle).
It takes place in mitochondria of eukaryotes and in cytosol of prokaryotes.
---Electron Transport Chain: An electron transport chain (ETC) is a series of complexes that transfer electrons from electron donors to electron acceptors via redox (both reduction and oxidation occurring simultaneously) reactions, and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. In eukaryotes, an important electron transport chain is found in the inner mitochondrial membrane where it serves as the site of oxidative phosphorylationthrough the use of ATP synthase. It is also found in the thylakoid membrane of the chloroplast in photosynthetic eukaryotes. In bacteria, the electron transport chain is located in their cell membrane. (https://en.wikipedia.org/wiki/Electron_transport_chain).
95. In Aerobic Respiration, total number of ATP produced are 38.
Aerobic respiration consists of three steps.
1. Glycolysis (2 ATP)
2. Krebs Cycle (2 ATP)
3. Electron Transport Chain (34 ATP)
Total = 38 ATP (https://www.wyzant.com/resources/lessons/science/biology/cellular-respiration)
96. NADH and FADH2 in aerobic respiration:
ATP production is an important part of cellular respiration (the process of generating energy from food) and both NADH and FADH2 that are involved in this process help in making more ATP.
Cellular respiration is essentially a 4-step process that includes glycolysis, acetyl CoA formation, Krebs cycle, and electron transport chain. In glycolysis, sugar is broken down to generate the end product, pyruvate. Pyruvate is a 3-carbon molecule, which gets converted into acetyl coenzyme-A (CoA). In the Krebs cycle, acetyl CoA is oxidized, which releases high energy electrons. These electrons and hydrogen atoms combine with NAD+ and FAD molecules to form NADH and FADH2, respectively.
NADH and FADH2 that act as electron carriers give away their electrons to the electron transport chain. The electron transport chain refers to a group of chemical reactions in which electrons from high energy molecules like NADH and FADH2 are shifted to low energy molecules (energy acceptors) such as oxygen. The electron transport chain is the primary means by which energy is derived in cellular respiration as well as in other processes like photosynthesis.The electrons that are shifted from NADH and FADH2, are essentially high-energy electrons. The energy that is released while transferring these electrons is used for making ATP. (https://biologywise.com/function-of-nadh-fadh2).
97. Characteristics of Cancer Cells are given below: Cancer is a malignant neoplasm that is the effect of uncontrolled proliferation of cells.
a) Cancer cells are self sufficient on growth factors. This means that they can continue to proliferate and divide independently, as opposed to normal cells that need external growth factors.
b)They can resist inhibitory signals that normally come from neighbouring cells.
c) Resisting apoptosis is also a crucial attribute of a cancer cell.
d) Can multiply forever. Normal cells go through senescence through e.g. shortening of telomeres with every cell division. Cancer cells however have telomerase that will sustain the telomere length of the chromosomes rendering the cell virtually immortal.
e)Invade local tissues and metastasize. This means that the cancer cells spread throughout the body by sending out pioneer cells that can form new metastases.
98: Methods for gene cloning:
There are two types of gene cloning: in vivo, which involves the use of restriction enzymes and ligases using vectors and cloning the fragments into host cells (as can be seen in the image above). The other type is in vitro which is using the polymerase chain reaction (PCR) method to create copies of fragments of DNA.
a) In vivo cloning a fragment of DNA, containing a single gene or a number of genes, is inserted into a vector that can be amplified within another host cell. A vector is a section of DNA that can incorporate another DNA fragment without losing the capacity for self-replication, and a vector containing an additional DNA fragment is known as a hybrid vector. If the fragment of DNA includes one or more genes the process is referred to as gene cloning.
There are 4 different type of vectors:Plasmid vectors, Lamda (?) phage vectors , Cosmids, Expression vectors
The host cell copies the cloned DNA using its own replication mechanisms. A variety of cell types are used as hosts, including bacteria, yeast cells and mammalian cells.
b) Polymerase Chain Reaction (PCR), is an in vitro method for making many copies of a specific section of DNA, without the need for vectors or host cells. The DNA to be copied – the template DNA – is mixed with forward and reverse primers complementary to the end of the template DNA, nucleotides, and a version of DNA polymerase known as Taq polymerase. (This enzyme is stable under high temperatures, and is obtained from the thermophilic bacterium Thermus aquaticus.) The process involves the repetition of three steps:
(https://www2.le.ac.uk/projects/vgec/schoolsandcolleges/topics/recombinanttechniques)
99. Competetive Inhibition: It is a form of enzyme inhibition where binding of an inhibitor prevents binding of the target molecule of the enzyme, also known as the substrate. This is accomplished by blocking the binding site of the substrate - the active site - by some means. In competitive inhibition, an inhibitor that resembles the normal substrate binds to the enzyme, usually at the active site, and prevents the substrate from binding. During competitive inhibition, the inhibitor and substrate compete for the active site. The active site is a region on an enzyme which a particular protein or substrate can bind to. The active site will only allow one of the two complexes to bind to the site therefore either allowing for a reaction to occur or yielding it. (https://en.wikipedia.org/wiki/Competitive_inhibition).
100. Proto-onncogenes code for proteins that stimulate or help cell division while tumor suppressor genes code for proteins that cell division.
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