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A1.1.2 Flashcards

Water and Nucleic Acids

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1
Q

Structure of Water

What is a Solvent?

A
  • A solvent is the substance that solutes are able to dissolve into.
  • The larger volume substance that is chemically able to dissolve other substances (solutes) in order to create a solution.
  • Water is a sigficiant solvent — its properties make it able to dissolve many different solutes.
  • Water is the solvent that makes up cytoplasm of cells, fluids between organelles, blood streams, habitats such as oceans, lakes and rivers.
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2
Q

Structure of Water

What is meant by the term Polarity?

A
  • Electrons are not equally shared in a molecule, are instead pulled more closely towards one element than the other –> creating a slight/ partial charhe in the elements.
  • The molecule bends with the positive element at one end (POLE) and the negative at the other pole.
  • This creates a molecule with two poles with opposite charges and that molecule is now POLAR.
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3
Q

Structure of Water

What is Cohesion?

A
  • When two polar molecules form weak bonds between them (HYDROGEN BONDS), this IS called cohesion.
  • Because the oxegyn of a water molecule has a slight negative — and the hydrogen has a slight positive, they are atrracted to one another –> and a weak hydrogen bon forms between the two water molecules.
  • The bonds between different water molecules are an example of COHESION.
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4
Q

Structure of Water

What is Adhesion?

A
  • The same concept of positive and negative charges being attracted can cause two different polar molecules to form hydrogen bonds as well.
  • When water forms H-bonds —> is attracted to other polar molecules/ surfaces —-> ADHESION.
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5
Q

Structure of Water

What is Capillary Action?

A
  • Refers to the ability of fluid/water to move against gravity up a narrow thin tube without any force.
  • This is the result of BOTH cohesion and adhesion.
  • Adhestion is the bonding of the water to the sides of the thin tube
  • Cohesion is the bonds between the water molecules that aids in each molecule pulling other water molecules up.
  • More significant in how water moves up plants.
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6
Q

Structure of Water

The Essential role of Water for Life

A
  • Cells and living organisms did not evolve until temperatures were low enough for liquid water bodies to form.
  • From the oceans, the first cells arose as a result of water acting as a solvent for those buildings blocks.
  • The cytoplasm of cells are water-based solutions and it is water-based blood in animals that transport materials between cells.
  • These aqueous solutions are esstional for life and all living processes.
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7
Q

Structure of Water

Polar vs Non-Polar Covalent Bonds

A
  • If two elements equally share electrons (due to neither atom having a higher electron density) then the result is a non-polar covalent bond.
  • This results in a molecule with balanced charges and no poles with different charges.
  • If instead the electrons are unequally shared —> a slightly positive with one atom at one end and slightly negative charge with the atom at the other end, this is called a polar covalent bond.
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8
Q

Structure of Water

Hydrogen Bonds in Water

A
  • Two water molecules are in close proximity to one another, the slight negative charge on the oxegyn of one molecule is attracted to the slight positive of the hydrogen of the other molecule.
  • This forms a weaker, temporary bond between them called a Hydrogen bond.
  • This bond is weaker than covalent and ionic bonds, and readily breaks by heat or distance.
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9
Q

Structure of Water

Surface Tension in Water

A
  • Cohesion of water molecules creates what is known as surface tension.
  • At the surface of a body of water —- hydrgoen bonds between the molecules next to and below it, but no bonds pulling up (the attraction to water is much less pulling it closer to the other water molecules instead.)
  • The sideways and below bonds are actually stronger –> more force is needed to break them than other cohesive bonds in water.
  • The stronger cohesive bonds at the surface are called surface tension.
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10
Q

Structure of Water

Reptiles using Surface Tension

A
  • The force of surface tension means that it is actually possible for light objects to float on the surface of the water without breaking those hydrogen bonds – giving an almost solid like quality is there is a strong surface tension and the object is light and movies quickly.
  • several insects use this property to walk along the surface of water – they would need light legs.
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11
Q

Structure of Water

Cohesion in Xylem

A
  • Plants must transport water obtained in soil up to leaves without any force —> the tubes water travels in are called xylem – they work like straws.
  • The water evaporates out of leaves creates a pull/ tension.
  • Due to the cohesion between water molecules, as molecules leave the leaf, other molecules are pulled up.
  • Cohesion allows that water to continously move upwards.
  • Adhesion attractive forces between the colar celluose of cell walls also helps to continually pull water up.
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12
Q

Properties of Water

What is an aqueous solution?

A
  • Any solution that has water as its solvent is called an aqueous solution.
  • The cytoplasm of cells, intercelluar fluids, and the blood stream are all aqueous solutions.
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13
Q

Properties of Water

What does the word Hydrophilic mean?

A
  • A substance that readily dissolves in water is called hydrophilic.
  • Other polar substances that do not dissolve in water but have an attraction to water —- also considered hydropihilic.
  • Essentially means ‘wate loving’ – any substance that have has charges that react with water in any way are hydrophilic.
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14
Q

Properties of Water

What does the word hydrophobic mean?

A
  • A substance that is not attracted to water –> hydrophibic.
  • They may not repelt water, but many do, they may just simply not be attracted to it.
  • They do not dissolve in water — so are instead attracted to other non-polar substances.
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15
Q

Properties of Water

What is Buoyancy?

A
  • A term for a specific force, which is the upwards force exerted on an object when it is placed on a medium (usually water).
  • The pressure of the water below is greater than the pressure of the air above.
  • If the density of the object is grater than the buoyancy force, then the object will float.
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16
Q

Properties of Water

What is Viscosity?

A
  • The ‘stickiness’ of a fluid, that determines how easily it can flow.
  • Comes from the friction, when one part of fluid moves relative to another.
  • Pure water has high viscocity than other pure fluids –> due to its hydrogen bonds. (but traditionally has a low viscocity, as it is easy to flow, unlike syrup.)
  • Addition of solutes increase viscocity (make it harder to flow) so that sea water has a higher viscocity.
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17
Q

Properties of Water

What is meant by ‘Thermal Conductivity?’

A
  • The rate at which heat passes through a material.
  • Water has a relatively high conductivity.
  • This has implications for aquatic organisms who lose heat – but helpful for being used to transfer heat.
  • For instance, blood can move heat towards the surface of our bodies to remove heat from the body.
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18
Q

Properties of Water

What is meant by ‘Specific Heat Capacity?

A
  • How much heat can be absorbed without actually changing temperature.
  • Water has a high heat capacity —> it takes a lot of absorbed heat before it will raise a degree Celcius.
  • water is slow-to-warm, meaning that it is very important for squatic life because it means water does not rapidly change temps.
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19
Q

Properties of Water

Examples of Hydrophillic molecules in Living Organisms

A
  • Salt (an ionic compound that dissolves in water.)
  • Glucose (a polar covalent compound that dissolves in water)
  • Cellulose (a large polar compound that water forms adhesive bonds with.)
  • Fats (can be body fats but also the lipids that make up our cell membranes.)
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20
Q

Origins of Water on Earth

What does Extraplanetary mean?

A
  • A factor outside of Earth and its orbit, or occuring in outer space outside of a planet.
  • Asteroids as the extraplanetary explanation for water on Earth.
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21
Q

Origins of Water on Earth

What is an asteroid?

A
  • Small (relative to the sun) rocky objects that orbit the sun.
  • Much smaller than planets –> believed to be remnants left over from the formation of the solar system.
  • Often rotate erratically and tumble through space.
  • Larger ones can have their own companion moons.
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22
Q

Origins of Water on Earth

What is meant by Extraterrestrial Life?

A
  • The possibilty of life outside of Earth which could include on other planets.
  • To research this —> generally begins with evalutating where other abiotic factors exist that facilitate liquid water.
23
Q

Origins of Water on Earth

Contribution of Asteroids

A
  • Asteroids contain water withing the rock, and when they collide, they break apart releasing water.
  • Evidence suggests that there could have been heavier bombardment of large asteroids in the first few hundred million years after Earth’s formation, causing a delivery of lots of water from the asteroids and icy comets.
24
Q

Origins of Water on Earth

Retention of Water on Earth

A

The two factors that ensure that water be able to stay on earth:
1) - The distance from the Sun esures that the temperature on Earth is never high enough for water to boil —> liquid water is easier to retain due to the cohesive H bonds.
2) Earth has a relatively strong gravitational pull, due to its size, which holds the ocean to its surface –> keeps water vapour from going into space.

25
Q

Origins of Water on Earth

The ‘Golidlock’ Zone

A
  • A metaphor for what is also known as the ‘habitable zone’, which is the distance form a star that water can remain in liquid form which is needed for life.
  • Too close to a star –> will vaporize.
  • Too far from a star —> will freeze.
  • Earth is just right distance, hence goldilocks zone, from sun.
26
Q

Structure of DNA and RNA

What is a nucleotide?

A
  • One single nucleotide is the building block of nucleic acids including DNA and RNA. These are repeated units that form the nucleic acids.
  • Each nucleotdie is made up of 3 parts:
  • 1) A pentose (5carbon) sugar
  • 2) A phosphate group
  • A nitrogen base (A,T,C,G,U)
27
Q

Structure of DNA and RNA

What are polymers?

A
  • A larger molecule made up of many repeated units. (the word means ‘many parts’)
  • The builidng blocks are called monomers, and they are chemically joined together to form a polymer.
  • DNA and RNA are both polymers and the monomer that they are made up are nucleotides.
28
Q

Structure of DNA and RNA

What is a hydroxyl group?

A
  • A common chemical group (sometimes called a funtional group) is an oxegyn and one hydrogen connected to a larger molecule.
  • This OH- is clalled a hydroxyl group, which are particularly common in sugars/ carbohydrates.
  • Is significant in nucleis acids because the difference between the Ribose sugar in RNA and Deoxyri-bose sugar in DNA, is a hydroxyl group in ribose, but lone hydrogen in Deoxyribose.
29
Q

Structure of DNA and RNA

What are condensation reactions?

A
  • The chemical reaction that joins two monomers together.
  • Also called polymerization or Dehydration Synthesis.
  • To make monomers reactive, an -OH is removed from one monomer and an -H from another. This facilitates a bond to form between the monomers. The hydroxyl and hydrogen join to make water as a waste product.
30
Q

Structure of DNA and RNA

Covalent Bonds vs Hydrogen Bonds

A
  • Covalent bonds are fairly strong and difficult to break meaning —> the covalent bonds that connect nucleotides in the DNA backbone are strong and the single chains are very stable.
  • The hydrogen bonds between the bases in the double helix however, are considerably weaker. Meaning that they can be easily broken –> important for DNA replication during mitosis and transcription to make proteins .
31
Q

Structure of DNA and RNA

The DNA Backbone

A
  • The backbone of DNA refers to the sugar and phsphates along each of the two sides.
  • Covalent bonds form between the sugar of one nucleotide and the phosphate of the next one.
  • These bonds – > formed by condenstation reactions –> the resulting strong covalent bonds are called phosphodiester bonds.
32
Q

Structure of DNA and RNA

Nitrogenous bases in DNA vs RNA

A
  • There are four bases in DNA:
    1. Adenine, 2. Thymine, 3. Guanine, 4. Cytosine.
  • Also four bases in RNA and three of them are the same: Adenine, Guanine and Cytosine. But instead of Thymine, there is Uracil.
33
Q

Structure of DNA and RNA

Function of Nucleic Acids - MESSENGER RNA.

A
  • Messenger RNA is a small single stranded nucleic acid.
  • Used to create a copy of one single section (A GENE) of DNA.
  • That copy then leaves the nucleus and is used to make protiens at the ribosomes.
  • The process that makes mRNA is called transcription.
34
Q

Structure of DNA and RNA

Function of Nucleic Acids - TRANSFER RNA.

A
  • Transfer RNA are used in the process of making proteins.
  • The copied instructions on mRNA travel to the ribosomes.
  • tRNA are small looped RNA strands that bring oer amino acids to build a protein.
35
Q

Structure of DNA and RNA

Function of Nucleic Acids - RIBOSOMAL RNA.

A
  • Strands of RNA also make up the ribosomes themselves,
  • Ribosomes are made up of RNA strands and proteins.
  • The ribosome is the site of protein synthesis.
  • It is made up of two subunits – that clamp down when mRNA attatches to it.
36
Q

Structure of DNA and RNA

Function of Nucleic Acids - ADENOSINE TRIPHOSPHATE RNA.

A
  • The celluar energy molecule ATP is actually a single nucleotide nucleic acid.
  • It is an adenine nucleotide with two additional phosphate molecules.
  • The bond between the second and third phosphate is a high energy bond which means that when broken, energy is released that allows cells to perform vital functions.
37
Q

Structure of DNA and RNA

Complementary Base Pairing Rules

A
  • Complementary base pairing means that Adenine can only pair with Thymine and Guamine can only pair with Cytosine.
  • This is essential – due to the size and shape of the bases. Is also vital because it means that one strand of DNA acts as a template for the code for the other strands.
  • Used in DNA replication and transcirption to create new strangs using the base pairing rules and one existing strand.
38
Q

Structure of DNA and RNA

DNA as the code for proteins

A
  • The purpose of DNA is to provide the specific instructions for the making of proteins.
  • Proteins are strands of amino acids.
  • The DNA that codes for one single protein is called a gene.
  • The DNA gives the order of amino acids for that protein.
  • Every three bases are called a triplet codon.
  • Because a gene can be any length and the different base sequences are limitless, DNA can make an infinite number of protiens.
39
Q

Structure of DNA and RNA

DNA as a Universal code

A
  • In ALL living organisms, the same base sequences code for the same amino acids.
  • EG: TTT always codes for phenylalanine and bactiera, or mice, or zebras, or humans.
  • Important as evidence of evolution –> has important implications for genetic technology.
40
Q

DNA Directionality and Chromosome Structure

What is ‘Directionality?’

A
  • Refers to the specific alignment of nucleotides - in particular whether the phosphate is facing up or down.
  • The two strands of DNA run in opposite directions, one strand runs ‘right side up’, where the phosphate is facing up (known as 5’—->3’), the second strand runs upside down whereby the phosphate faces down (3’—>5’).
  • Their opposite direction is referred to as parallel.
41
Q

DNA Directionality and Chromosome Structure

What is Histones?

A
  • Are protiens that strands of DNA wrap around.
  • Due to the volume of DNA it needs to be organised in some way inside the nucelous.
  • Either histonse cluster together – DNA wraps TWICE around them.
  • The DNA forms chromosome shape when tightly packed.
  • Levek of closely packed DNA –> varies during the cell cycle and protein synthesis.
42
Q

DNA Directionality and Chromosome Structure

What are Nucleosomes?

A
  • The term for the cluster of 8 histone proteins with DNA wrapped around it.
  • The DNA is wrapped twice and then an additional H1 histone is used to hold it into place .
  • Each histone has 146 base pairs wrapped around it.
  • There is a linker DNA between each histone.
43
Q

DNA Directionality and Chromosome Structure

The 5’ and 3’ ends of a nucleotide.

A
  • Directionality relates to the oritentation of the sugar.
  • Each Carbon of the SUGAR is numbered.
  • The top most carbon is called 5’ and the phosphate is attatched to it.
  • The base of the sugar is the 3’ end.
  • A phosphate UP nucleotide has 5’ at the top and 3’ at the bottom.
44
Q

DNA Directionality and Chromosome Structure

DNA Processes: Replication

A
  • DNA replication is the process —> where one double stranded molecule is split into two —> each side is then copied to produced two double helices. (happens before cell division aka mitosis)
  • Directionality complicates DNA replication —> each seperated strand MUST have the anti-parallel strand created.
  • New strands are always copied/ produced in the 5’ –> 3’ direction, which makes building the ‘upside down’ strand harder.
45
Q

DNA Directionality and Chromosome Structure

DNA processes: Transcription

A
  • The process when DNA is copied in the nucelus to make mRNA for protien synthesis.
  • Nucleotides are always added to a 3’ end.
  • As transcription only creates one single strand and bases must be attached at the 3’ end, transcription always builds a 5’–>3’ strand.
  • When DNA splits, therefore it is always 3’–>5’ strand that acts as the template for transcription.
46
Q

DNA Directionality and Chromosome Structure

DNA Processes: Translation

A
  • The process of ‘reading’ the mRNA code to add the correct amino acids and build a protein at the ribosome.
  • When translation occurs at the ribosome, the process moves from the start of the mRNA at the 5’ end along the strand through to the 3’ end.
  • Translation, thus, also runs in the 5’–>3’ direction.
47
Q

DNA Directionality and Chromosome Structure

Purines vs Pyrimidines

A

The four nitrogenous bases differ according to the chemical make up and size.

  • PURINES: Adenine and Guanine are both larger, double ringed nucleotides.
  • PYRIMIDINES: Thymine, Cytosine, Uracil are small, single ringed nucleotides.

REMEBER: CUTS are not pure. (Cytosine, Uracil and Thymine.)

48
Q

DNA Directionality and Chromosome Structure

Purines-Pyrimidines Base Pairing Importance.

A
  • For a DNA double helix to maintain a constant shape, it is essential that every base pair combination is one larger pyrimidine base and one smaller purine base.
49
Q

History of DNA Discovery

What is bateriophage?

A
  • A VIRUS that invades and infects BACTERIA.
  • Composed of a protein COAT and a strand of DNA and spikes that help anchor onto the bacteria they are invading.
  • They do not make humans sick, but act on bacteria in similar ways to how other visuses invade our cells.
50
Q

History of DNA Discovery

What are radioisotopes?

A
  • A radioactive form of an element.
  • Release particles during their decay that allow them to be detected.
51
Q

History of DNA Discovery

What is paper chromotography?

A
  • A mixture of substances in embedded on chrmoatography paper and placed in a solvent.
  • As the solvent moves through the fibres of the paper, it carries the substances at different speeds based on their size and charge.
52
Q

History of DNA Discovery

How do bacteriophages impact bacteria?

A
  • They insert their DNA into the bacteria and then the bacteria begins using the viral DNA to make viral parts which will assemble and burst the host bacterial cell.
  • The actual viral capsid never enters the bacteria, ONLY ITS DNA.
  • As DNA is inserted and NOT the protien —> DNA is the code.
53
Q

History of DNA Discovery

Hershey and Chase’s ‘supernatant’ and ‘pellet’

A

Hershey and Chase assembled viruses and bacterial cells into a solution and allowed time for the visurs to invade the bacteria –> then centrifuged the solution by weight.
- Heavier part of the bottom formed the pellet and was made up of BACTERIAL CELLS.
- The lighter part of the top formed the supernatant and contained the LEFTOVER VIRAL SHELLS after they had invaded the bacteria.

54
Q

History of DNA Discovery

Chargaff’s falsification of the ‘tetranucleotide hypothesis’

A
  • Previous hypothesis called the tetranucleotide hypothesis formulated in 1910 — regarding struture of DNA – was it would contain repeating sequences of the four bases.
  • Meaning that there would always be the same number of each base.
  • Chargraff’s results falsified this –> it showed that while there are equal AMOUNTF OF A AND T, there is DIFFERENT AMOUNTS OF C AND G, therefore, they cannot be simply a repeating sequence.

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