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RNA, Types, and RNA vs DNA
Continue ReadingDifferences between DNA and RNA (RNA vs DNA)
○ Carbon #2 on the pentose is not “deoxygenated” (it has a hydroxyl group attached).
○ RNA is single stranded.
○ RNA contains uracil instead of thymine.
○ RNA can move through the nuclear pores and isn’t confined to the nucleus.
Types of RNA
RNA exists in 3 forms:
1) mRNA
○ Delivers the DNA code for amino acids to the cytosol where the proteins are manufactured.
○ Has a short half-life in the cytosol, so soon after its transcription is over, the mRNA is degraded.
○ Many proteins can be transcribed in a single mRNA.
2) rRNA
○ Combines with proteins to form ribosomes, the cellular complexes that direct the synthesis of proteins.
○ rRNA is synthesized in the nucleolus.
3) tRNA
○ Collects amino acids in the cytosol, and transfers them to the ribosomes for incorporation into a protein.
mRNA → massive
rRNA → rampant
tRNA → tiny
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RNA Transcription, Diagram, Definition, Process, Steps
Continue ReadingRNA Transcription
○ All RNA is manufactured from a DNA template in a process called RNA transcription.
○ Transcription requires a promoter; Replication requires a primer.
○ The beginning of transcription is called initiation.
○ In initiation, a group of proteins called initiation factors finds a promoter on the DNA strand, and assembles a transcription initiation complex, which includes RNA polymerase
○ Prokaryotes have 1 type of RNA polymerase; Eukaryotes have 3 types of RNA polymerase (one for each type of RNA).
○ A promoter is a sequence of DNA nucleotides that designates a beginning point for transcription, and promoter recognition is the rate limiting step in transcription.
○ The promoter in prokaryotes is located at the beginning of the gene (said to be upstream).
○ The transcription start point is part of the promoter.
○ The first base-pair located at the transcription start point is designated +1; base-pairs located before the start point, such as those in the promoter, are designated by negative numbers.
○ The most commonly found nucleotide sequence of a promoter recognized by the RNA polymerase of a given species is called the consensus sequence.
○ Variation from the consensus sequence causes RNA polymerase to bond less tightly and less often to a given promoter, which leads to those genes being transcribed less frequently.
○ After binding to the promoter, RNA polymerase unzips the DNA double helix creating a transcription bubble.
○ Next the complex switches to elongation mode.
○ In elongation, RNA polymerase transcribes only one strand of the DNA nucleotide sequence into a complementary RNA nucleotide sequence.
○ Only one strand in the molecule of double stranded DNA is transcribed.
○ This strand is called the template strand or (-) antisense strand.
○ The other strand, called the coding strand or (+) sense strand protects its partner from degradation.
○ The coding strand/sense strand resembles the universal code sequence of RNA.
Diagram Representing Regulation of Transcription in Eukaryotes
○ Just like DNA polymerase, RNA polymerase reads in the 3’ → 5’ direction and builds in the 5’ → 3’ direction, but it DOESN’T have proofreading ability.
○ The end of transcription is called termination, and requires a special termination sequence (high G-C content) and special proteins to dissociate RNA polymerase from DNA.
○ Genes are activated or deactivated at the level of transcription.
○ For all cells, most regulation of gene expression occurs at the level of transcription via proteins called activators and repressors.
○ Activators and repressors bind to DNA close to the promoter, and either activate or repress the activity of RNA polymerase.
○ Activators and repressors are often allosterically regulated by small molecules such as cAMP.
○ The primary function of gene regulation in prokaryotes is to respond to the environmental changes.
○ In contrast, lack of change or homeostasis of the intracellular and extracellular compartments is the hallmark of multicellular organisms.
○ The primary function of gene regulation in multicellular organisms is to control the intra- and extracellular environments of the body.
○ Prokaryotic mRNA typically contains several genes in a single transcript (polycistronic), whereas eukaryotic mRNA includes only one gene per transcript (monocistronic).
○ The genetic unit usually consisting of the operator, promoter, and genes that contribute to a single prokaryotic mRNA is called the operon.
○ Genes of an operon are transcribed on one mRNA.
○ Genes outside the operon may code for activators and repressors
○ An operator is a segment of DNA that a regulatory protein binds to.
○ It is classically defined in the lac operon as a segment between the promoter and the genes of the operon.
○ A repressor or activator can bind to an operato.
○ A good example of an operon is the lac operon.
○ The lac operon codes for enzymes that allow E. Coli to import and metabolize lactose when glucose is not present in sufficient quantities.
○ Low glucose levels lead to high cAMP levels.
○ cAMP binds to and activates catabolite activator protein (CAP).
○ The activated CAP protein binds to a CAP site located adjacent and upstream from the promoter to the lac operon.
○ The promoter is now activated allowing the formation of an initiation complex and subsequent transcription and translation of the 3 proteins.
Diagram Representing Regulation of Transcription in Prokaryotes
○ A second regulatory site on the lac operon, called the operator, is located adjacent and downstream to the promoter.
○ The operator provides a binding site for a lac repressor protein.
○ The lac repressor protein is inactivated by the presence of lactose in the cell.
○ The lac repressor protein will bind to the operator unless lactose binds to the lac repressor protein and inactivates it.
○ The binding of the lac repressor to the operator in the absence of lactose prevents the transcription of the lac genes.
○ Lactose, then, can induce the transcription of the lac operon only when glucose is not present.
○ Gene regulation in eukaryotes is more complicated involving the interaction of many genes.
○ Thus more room is required than is available near the promoter.
○ Enhancers are regulatory proteins commonly used by eukaryotes.
○ Their function is similar to activators and repressors, but they act at a much greater distance from the promoter.
RNA Transcription Citations
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DNA Replication, Replication Fork, DNA Polymerase, Replication...
Continue ReadingDNA Replication
• DNA replication is semiconservative.
• This means that when a new double strand is created, it contains one strand from the original DNA, and one newly synthesized strand.
• It is similar for both Prokaryotes and Eukaryotes.
• The process of DNA replication is governed by a group of proteins called a replisome.
DNA Replication Diagram
• It is made up of a number of subcomponents that each provide a specific function during the process of replication.
• Replication doesn’t begin at the end of chromosomes, but toward the middle at a site called the origin of replication.
• A single eukaryotic chromosome contains multiple origins on each chromosome, while replication in prokaryotes usually takes place for a single origin on the circular chromosome.
• From the origin, two replisomes proceed in opposite directions along the chromosome making replication a bidirectional process.
• The point where a replisome is attached to the chromosome is called the replication fork.
DNA Replication Fork
• Each chromosome of eukaryotic DNA is replicated in many discrete segments called replication units or replicons.
• A replicon is a DNA molecule or RNA molecule, or a region of DNA or RNA, that replicates from a single origin of replication.
• For most prokaryotic chromosomes, the replicon is the entire chromosome.
• For eukaryotic chromosomes, there are multiple replicons per chromosome.
• The definition of replicons is somewhat confused with mitochondria, as they use unidirectional replication with two separate origins.
"Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end of a polynucleotide chain"
• DNA helicase uses the energy of ATP hydrolysis to actively unwind the two strands.
• DNA polymerase, the enzyme that builds the new DNA, cannot initiate a strand from two nucleotides, but can only add nucleotides to an existing strand.
• Therefore it requires an RNA primer to get started.
• It reads the parental strand in the 3’ → 5’ direction.
• Since it can only add new subunits to the 3’ end of the chain, it must create the new complementary strand in the 5’ → 3’ direction
• Besides being a polymerase, one of the subunits in DNA polymerase has 3’ → 5’ exonuclease (it removes nucleotides from the strand) capabilities.
• Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end of a polynucleotide chain
• There are 3 types of polymerase molecules This enzyme automatically proofreads each new strand, and makes repairs when it discovers any mismatched nucleotides.
• Primase, an RNA polymerase, creates an RNA primer approximately 10 ribonucleotides long to initiate the strand.
• Each nucleotide added to the new strand requires the removal of a pyrophosphate group (two phosphates binded together) from a DNTP (deoxynucleotide triphosphate).
• Some of this energy derived from the hydrolysis of the pyrophosphate is used to drive replication.
• SSB tetramer proteins (also called helix destabilizer proteins) prevent the two strands from reattaching after the helix is opened.
• The interrupted strand is called the lagging strand; the continuous new strand is called the leading strand.
• The lagging strand is made from a series of disconnected strands called Okazaki fragments.
• Okazaki fragments are about 100-200 nucleotides long in eukaryotes and about 1000-2000 nucleotides long in prokaryotes.
"SSB tetramer proteins (also called helix destabilizer proteins) prevent the two strands from reattaching after the helix is opened"
• DNA Ligase moves along the lagging strand and ties the Okazaki fragments together to complete the polymer.
• Since the formation of one strand is continuous and the other fragmented, the process of replication is said to be semidiscontinuous.
• The ends of eukaryotic chromosomal DNA possess telomeres.
• Telomeres are repeated 6 nucleotide units from 100-1000 units long that protect the chromosomes from being eroded through repeated rounds of replication.
• Telomerase catalyze the lengthening of telomeres at the 3’ ends of DNA strands.
• Eukaryotic chromosomes contain linear DNA molecules; Prokaryotic chromosomes are usually circular.
• So telomeres aren’t required by Prokaryotes that have circular DNA.
DNA Replication Citations
- Exploiting DNA Replication Stress for Cancer Treatment. Cancer Res . 2019 Apr 15;79(8):1730-1739.
- DNA replication origins-where do we begin? Genes Dev . 2016 Aug 1;30(15):1683-97.
- Mechanisms of DNA replication termination. Nat Rev Mol Cell Biol . 2017 Aug;18(8):507-516.
- Origins of DNA replication. PLoS Genet . 2019 Sep 12;15(9):e1008320.
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Chromosomes, Genes, DNA: Definition, Structure, and Functions
Continue ReadingChromosomes, Genes, DNA
○ A gene is a series of DNA nucleotides that generally codes for the production of a single polypeptide or mRNA, tRNA, rRNA.
○ The entire DNA sequence of an organism is called the genome.
○ Eukaryotes have more than one copy of some genes, while prokaryotes have only one copy of each gene.
○ Genes are often referred to as unique sequence DNA; while regions of non-coding DNA found only in eukaryotes are called repetitive sequence DNA.
○Generally speaking: One gene; one polypeptide. One exception is posttranscriptional processing of RNA.
Chromatin Structure
○ Negatively charged DNA loops twice around.
○Histone octamer (2 each of the positively charged H2A, H2B, H3, and H4) to form nucleosome bead.
"Histone octamer (2 each of the positively charged H2A, H2B, H3, and H4) to form nucleosome bead"
○Eukaryotic genes that are actively being transcribed by a cell are associated with regions of DNA called euchromatin, while genes not being actively transcribed are associated with tightly packed regions of DNA called heterochromatin.
○ Repetitive DNA is found mainly in heterochromatin.
○The Central Dogma of gene expression is that DNA is transcribed to RNA, which is translated to amino acids forming a protein.
DNA
○ Four nitrogenous bases exist in DNA:
○ Purines: Two ringed structure
1) Adenine (less C=O)
2) Guanine (more C=O)
○ Pyrimidines: Single ring structure
3) Cytosine (less C=O)
4) Thymine (more C=O)
○ Deamination of cytosine forms uracil
○ In nucleic acids, nucleotides are joined together by phosphodiester bonds between the third carbon of one dexoyribose and the phosphate backbone of a single strand of DNA with a 5 → 3 directionality.
○ A phosphodiester bond is a group of strong covalent bonds between the phosphorus atom in a phosphate group and two other molecules over two ester bonds.
"In DNA, two strands are joined by the hydrogen bonds"
○ Nucleotides are written 5’ → 3’
○In DNA, two strands are joined by the hydrogen bonds to make the structure called the double helix.
○ This model was proposed by Watson and Crick.
○ The members of each base pair can fit together within the double helix only if the two strands of the helix are antiparallel.
○ By convention the top DNA strand goes 5’ → 3’ and the bottom 3’ → 5’
○ Going in the 5’ → 3’ Direction is referred to as going downstream
○ Going in the 3’ → 5’ Direction is referred to as going upstream The two strands are complementary strands.
○ The double helix contains two distinct grooves called the major groove and minor groove, which moves around once every 10 base-pairs.
Chromosomes, Genes, DNA Citations
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Electron Transport Chain (ETC): Definition, Steps, and...
Continue ReadingElectron Transport Chain (ETC)
Electron Transport Chain (ETC) is an aerobic, occurs across the inner cell membrane for prokaryotes, inner mitochondrial membrane for eukaryotes.
Structure of Electron Transport Chain (ETC)
• Oxidative phosphorylation oxidizes NADH to NAD+, which creates a proton gradiant, via the pumping out of H+, that propels protons through ATP synthase.
• So the intermembrane space has a lower pH/higher [H+ concentration] than the matrix.
• The inter-cristal space or the mitochondrial matrix has a low H+ concentration and a high pH.
• NADH oxidation back to NAD and FADH2 oxidation back to FAD occur along with ATP production, allowing the earlier stages to continue.
• As electrons move within the ETC each intermediate carrier is reduced by the preceding molecule and oxidized by the following
• Oxygen is the last electron acceptor in the ETC
• 1 NADH produces 3 ATP molecules
• 1 FADH produces 2 ATP molecules
Electron Transport Chain (ETC) Summary
• 36 net ATP produced in eukaryotes, 38 net ATP produced in prokaryotes (because the electrons from the NADH produced from pyruvate decarboxylation do not have to be transported across the mitochondrial membrane in prokaryotes; doing this causes a net loss of two ATP in eukaryotes)
• Products and Reactants for Respiration:
Glucose + O2 → CO2 + H2O
Electron Transport Chain (ETC) Citations
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Krebs Cycle or TCA Cycle: Definition, Steps,...
Continue ReadingKrebs Cycle or TCA Cycle
Krebs Cycle or TCA Cycle is an aerobic process, occurs in the cytoplasm for prokaryotes, mitochondrial matrix for eukaryotes.
The process of ATP production in the Krebs cycle is called Substrate-level phosphorylation
Krebs Cycle or TCA Cycle
Total:
⊛ 4 CO2 produced
⊛ 2 GTP/ATP produced
⊛ 6 NADH produced (making 18 ATP in ETC)
⊛ 2 FADH2 produced (making 4 ATP in ETC)
"Each turn in the Krebs Cycle produces (1 glucose provides two turns)"
⊛ 2 CO2 produced
⊛ 1 GTP/ATP produced
⊛ 3 NADH produced (making 9 ATP in ETC)
⊛ 1 FADH2 produced (making 2 ATP in ETC)
Krebs Cycle or TCA Cycle Regulation
⊛ The cycle is regulated at the three steps that are highly exergonic: those catalyzed by citrate synthase, isocitrate dehydrogenase, and a- ketoglutarate dehydrogenase.
⊛ NADH and ATP are both negative regulators; ADP and Ca2+are positive regulators (activators).
⊛ Triglycerides can also be catabolized for ATP. Fatty acids are converted to acyl CoA along the outer membrane of the mitochondrion and endoplasmic reticulum at the expense of 1 ATP. Then 2 carbons are cleaved to make acetyl CoA in the matrix. This reaction also produces FADH2 and NADH for every two carbons taken from the original fatty acid. Acetyl CoA then enters into the Krebs cycle as usual. This is called beta oxidation.
⊛ The fatty acids are linked to Coenzyme A and carried into the mitochondrial matrix by the g-amino acid L-carnitine. They are then are oxidized TWO carbons at a time in the KREB cycle, yielding an NADH, FADH2, and acetyl CoA.
⊛ Amino acids are deaminated in the liver. The deaminated product is either chemically converted to pyruvic acid or acetyl CoA, or it may enter the Kreb cycle at various stages depending upon which amino acid was deaminated.
Krebs Cycle or TCA Cycle Citations
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Examples of Physical Properties: Definition, Meaning
Continue ReadingExamples of Physical Properties
Changes can be categorized into physical and chemical. The matter is made up of tiny particles and has both the properties which are;
A chemical property is defined as the characteristic of a substance that can be observed in a chemical reaction.
For example heat of combustion, toxicity, acidity, reactivity etc.
A Physical Property is defined as the characteristic of a substance that can be observed without changing the chemical nature of the substance such as its size, state of matter, colour, mass, density etc. Some other physical properties include solubility, melting and boiling points etc.
Classification for Physical Properties
There are two classes of physical properties which are;
1. Extensive Property
2. Intensive Property
1. Extensive Property
Extensive properties are those properties that depend on the size of the sample.
Shape, volume and mass are extensive properties. The properties like length, mass weight and volume that not only depend on the size but also depend on the quantity of the matter.
For instance, if we have two boxes made up of the same material one has the capacity of 6 litres and the other has the capacity of 12 litres then the box with 12-litre capacity will have more amount of matter as compared to that of the 6-litre box.
2. Intensive Property
Intensive properties are those properties that do not depend on the size or amount of matter in the sample.
Temperature, pressure and density are some of the examples of intensive properties other examples include colour, melting and boiling points as they will not change with the change in size as well as quantity of matter.
The density of 1 litre of water or 1000 litre of water will remain the same as it is an intensive property.
Physical Change
Physical change takes place without any changes in the molecular composition of the substance. The same molecule is present in the substance throughout the changes.
Physical changes are related to the physical properties of a substance which are solid liquid and gas.
During physical change the composition and the chemical nature of matter are not changed chemical property is not affected by the physical change of a substance.
The physical change includes a change in colour, solubility, change in the state of matter etc.
Examples of physical change include melting an ice cube, dissolving sugar and water. Boiling water is also an example of physical change because the water vapour has the same molecular formula as that of liquid water.
Use of Physical Properties
Physical property is used to determine the appearance, texture, colour etc. of a substance thus, these physical properties are important as they help us to differentiate between different compounds, unlike chemical properties which help us to differentiate between various compounds only when a new substance is formed from a given substance by chemical reactions.
Examples of Physical Properties
A few examples of the physical property of matter comprise of;
• Malleability occurs when metal is moulded into thin sheets, for instance, silver is shiny metal and it can be moulded into thin sheets.
• Hardness which is another physical property helps to determine how the element can be used. For Example; Carbon in diamonds is very hard whereas carbon in graphite is very soft.
• Melting and boiling point is the physical property that is unique identifiers, especially of compounds
• Melting Point: When the solid matter is heated it ultimately melts or changes into its liquid state. The ice is a solid form of water that melts at 0 oC or 32 oF and changes to its liquid state that is water or H2O.
• Boiling Point: When the liquid matter is heated further it ultimately boils or vaporizes into its gaseous state. Liquid water boils and changes into gaseous molecules or water vapour at a temperature of 100 oC.
• Density implies the weight of the substance
Density is defined as mass divide by volume.
Density = Mass/Volume
• Colour is another physical reflective property of the given material. For example; Rusting of iron.
• Volume is referred to as a three-dimensional space that is occupied by a matter.
• Mass is one of the most significant fundamental property of an object and is defined as the measure of the amount of matter that is present in a body or substance.
• Weight is defined as the measure of the force of gravity acting on an object.
Examples of Physical Properties Citations
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Metric System Chart: Definition, Formula, and Calculation
Continue ReadingMetric System Chart
The metric system chart was introduced in the year 1790 in France and was the historical invention of the international system of units or SI units which is also known as metrification.
The various units of measurement lead to the introduction of the metric system.
Metric System
The metric system of measurement is the standard way of measuring distance, height, and many other day to day events.
Each object is measured according to its length, volume weight height, and time.
The three main basic units of the metric system are;
Metre: a unit used to calculate the length of an object.
Kilograms: a unit that is used to measure the mass of an object
Second: a unit of time.
Origin of the Metric System
Metrication is defined as a process that implements the international system of units called SI units. The Metric system is followed by nearly all countries except United States, Myanmar, and Liberia.
The United States further introduced its system of units or system of metric units which are now called the United States customary units.
Difference Between USCS and SI Units
The United States metric units are also called “imperial units.” The key difference between the SI units and the American metric units is the terms and the form of units used.
For instance, In the SI unit, the length is measured using the meter whereas In USCS foot is used for measurement.
Metric Conversion
Metric conversion has referred to the conversion of the given units to the chosen units for any given quantity that is to be measured. This metric system of measurement is a set of standard units that are defined to measure the length, weight, and capacity of the given object.
Metric Conversion Chart
Metric conversion charts help us in the conversion of given units to desired units. The metric conversion helps in easier and quick calculations.
Some metric chart tables are given below;
Length Conversion Chart
This unit length is used for measuring the size of an object or the distance that an object travels from one end to another end.
There are different units of length which are meters, kilometers, feet, etc. The basic tool which is used to measure length is called a ruler.
For Example; The height of this whiteboard is about 3 meters.
The smallest unit of measuring length is a millimeter and the largest unit of measuring length is kilometers.
Length conversion chart
1 inch = 2.54 cm
1 foot = 12 inch
1 yard= 3 feet or 36 inches
1 mile = 1760 yards
1 kilometer = 1000 metre
Weight Conversion Chart
Weight is the unit that is used to measure the mass of a substance. The standard unit that is used for the measurement of mass is the kilogram, gram ton, etc.
The basic tool which is used to measure the weight of an object is the weighing scale.
For instance; the weight of this alcohol bottle is 250 grams.
Weight conversion chart
1 kilogram =1000 gram
1 pound = 16 Oz
1 Oz = 16 drums
1 ton = 2,000 LB
Volume Conversion Chart
Volume is the unit that is used to measure the space occupied by an object or matter. The standard unit used for the measurement of capacity is litre. Other units used for measurement of unit volume are milliliter etc.
For example; 500 liters of juice.
Volume conversion chart
1 litre = 1000 ml
1 cup=250 ml
1 gallon = 4 watts
1 pint = 2 cups
Time Conversion Chart
The standard unit for the measurement of time is in seconds. Other metric units of time are minutes, hours, etc.
1 minute = 60 seconds
1 hour= 60 minutes
1 day = 24 hours
1 week = 7 days
Area Conversion Chart
The area is occupied by a two-dimensional figure the area is usually measured in square units.
1 acre= 43560 square feet
Metric System Chart Citations
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Volume: Definition, Formula, Chart, and Calculation
Continue ReadingVolume Definition
Volume is referred to as a three-dimensional space that is occupied by a matter for any other closed figure.
SI unit of volume is cubic meter (cm3) but many other units exist which include cubic centimeter, pint, quart, gallon, tablespoon, etc.
Examples of volume are; These beer bottle bottles hold 250 ml of alcohol.
Ishita drank 100 ml of water.
You can purchase a gallon of milk.
Volume of Liquid
The volume of a liquid can be measured with the help of a measuring container such as a measuring cup, graduated cylinders.
The volume of liquids is addictive but this is not always true because the volume of miscible liquids such as that of alcohol and water may be less than the sum of the separate volumes.
Another point to be noted is that dissolvable solids in two liquids don’t always result in their adjective volumes.
Volume of Gas
Volume of a gas is defined as the volume of its container as the gas expands to fill the space available to them in the given container.
The volume of a gas is sometimes determined by the displacement of its liquid.
Volume of Solid
The volume of a solid can be calculated by using its dimensions.
For example; the volume of a rectangular solid is the product of its length, width, and height that is V=lwh.
Volume vs Mass
The volume and mass are considered the same but these are two different properties of matter.
Volume is defined as the amount of space occupied by a substance on the other hand mass is the amount of matter contained in a substance.
Density is defined as mass per unit volume but it is possible to have volume without the mass the example for the same would be an enclosed vacuum.
Volume vs Capacity
Capacity and the volume of a container are not the same as capacity is defined as the capability of an object to contain a substance that is either solid, liquid, or gas, whereas volume is referred to the three-dimensional space that is occupied by the matter.
Volume is measured in cubic units such as in cubic centimeters and cubic meters etc.
Capacity is measured in metric units such as in liters, gallons, etc.
Charles Law
Charles law states that the volume of a certain amount of gas is directly proportional to that of temperature in kelvin when the pressure remains constant.
This can be written as;
V = kT
k = proportionality constant
V = volume of given gas
T = temperature of a given gas
Boyles Law
Boyle’s law states that the volume of a certain amount of gas is inversely proportional to its pressure when the temperature is kept constant.
The equation can be represented in the form of;
P = k/V
k = a proportionality constant
P = Pressure of given gas
V= volume of a given gas
Avogadro's Law
Avogadro’s law states that the volume is directly proportional to the number of moles of a given gas when the pressure and the temperature both remain constant.
The following equation can be written in the form of
V = kn
k = proportionality constant
n = Number. of moles of a given gas
V= volume of a given gas
Ideal Gas Law
The above four laws discussed are combined to produce an ideal gas law which is a relationship between pressure, volume, temperature, and the number of moles present in given gas.
The equation is given as
PV = nrt
P = pressure of the gas
V= volume of gas
N = number of moles of gas
T = temperature in kelvin
r = Constant and is also known as the ideal gas constant for the universal gas constant.
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International System of Units (SI Units): Chart,...
Continue ReadingInternational System of Units (SI Units)
International system of units (SI Units) is the most widely accepted system of measurement and this system is built on 7 primary units which are:
Length
Time
Weight
Amount of substance
Electric current
Temperature
Luminous intensity
This international system of units was earlier referred as meter-kilogram-second (MKS) system.
The principle behind international system of units is that it used to provide the same values across the world for measurements such as length, height, weight etc.
SI plays a vital role in international conferences and is also used in scientific and technological research.
History of SI Units
The international system of units was introduced in 1960 which was adopted by 11th general conference on weights and measure or CGPM.
This system was invented to modify the definition of units and to be used as technology for measuring objects that we use in our daily lives.
The United States further introduced its own system of units or system of metric units which is now called as United States customary units or USCS
Difference Between USCS and SI Units
The United States metric units are also called as “imperial units.” The key difference between the SI units and the American metric units is the terms and the form of units used.
For instance, In SI unit, the length is measured using the metre whereas In USCS foot is used for measurement.
The international system of units consisted of following three categories mentioned below; Base units Supplementary units Derived units
The seven base units are given below:
Length
This unit length is used for measuring the size of an object or the distance that an object travels from one end to the other end. There are different units of length which are metre, kilometers, feet etc. The most common tool which is used to measure length is called a ruler.
For Example; The height of this blackboard is about 3 metres. Smallest unit of measuring length is millimeter and the largest unit is kilometers.
1 kilometer = 1000 metre
Time
The standard unit for measurement of time is seconds. Other metric units of time are minutes, hours etc.
1 minute = 60 seconds
1 hour= 60 minutes
1 day = 24 hours
1 week = 7 days
Weight
Weight is the unit that is used to measure the mass of an object. The standard unit that is used for the measurement of mass is kilogram, gram ton etc.
The most common tool which is used to measure the weight of an object is the weighing scale. For instance; the weight of this bottle is 250 grams.
1 kilogram =1000 gram
Amount of Substance: Mole
The amount of matter of a system that comprises as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. Elementary entities are subatomic units that comprise matter and energy.
The symbol of unit mole is mol.
Luminous Intensity
The luminous intensity, in given route, of a source produces monochromatic radiation of frequency 540×1012 hertz and has a radiant intensity in that path of 1/683 watt per steradian.
The unit of luminosity is candela which is denoted by cd.
Current
Electric current is well-defined as the rate of flow of negative charges of a conductor. Since the charge is calculated in coulombs and time is in seconds, the unit of electric current is coulomb/Sec (C/s) or amperes. The SI unit of current Ampere is denoted by unit symbol A.
Thermodynamic Temperature
The kelvin (abbreviation K), is the SI unit of temperature. One Kelvin is 1/273.16 (3.6609 x 10 -3) of the thermodynamic temperature of the triple point of a pure water that is H 2O.
Supplementary Units
Plane Angle
The name of the unit which is used to calculate the plane angle is radian. Symbol of radian is rad.
Radian describes the plane angle that is subtended by an arc of a circle.
Solid Angle
The name of the unit which is use to describe the solid angle is steradian Symbol of steradian is sr.
A steradian describes the solid angle at the centre of sphere that is subtended on a section of surface.
Derived Units
Few examples of derived units are given below;
Area: Unit name of area is square metre.
Frequency: Unit name is hertz (Hz)
Volume: Unit name is cubic metre
Speed: Unit name is metre per second
Magnetic: Field strength Unit name is ampere pe metre
International System of Units (SI Units) Citations
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