A1 Unity and Diversity of Molecules Flashcards
Why is water the medium of life?
The first cells originated in water, water remains the medium in which most processes of life occur
What causes the polarity of covalent bonding within water molecules?
Unequal sharing of electrons, causing Oxygen to be slightly negative + Hydrogen slightly positive
What is the cause of hydrogen bonding between water molecules?
The polarity of the water molecules
What is a hydrogen bond (between water molecules)?
Weak temporary bond between H of one water molecue and the oxygen of another
What is cohesion?
Attraction between water molecules, due to hydrogen bonding
How is surface tension created within water?
Hydrogen bonds are formed between all water molecules in all directions. At the surface, the hydrogen bonds are stronger (and fewer). Therefore, the top layer is the strongest layer of bonds and is hardest to break.
What does surface tension mean for organisms?
Light objects/animals are able to move across without breaking the hydrogen bonds
What is the effect of cohesion within plants?
When one H2o evaporates out of the stomata, another one is pulled up. Therefore, the hydrogen bonds between the water allows for the continuous flow of movement up a thin tube (xylem)
What is the impact of water being adhesive to materials that are polar/charged?
Water is adhesive to sides of xylem vessel, allowing water not to fall back down the vessel. In this way, adhesion helps water ‘stick’ to plant cell walls
What does hydrophilic mean?
Substance that readily dissolves in water / polar molecules that don’t dissolve but are attracted
What does hydrophobic mean?
Not attracted to water. Does not dissolve in wter
What is buoyancy?
Upward force exerted on an object when it is placed on a medium
What is visocity?
Stickiness of a fluid, which determines its ability to flow
What is thermal conductivity?
The rate at which heat passes through a material
What is specific heat capacity?
How much heat can be absorbed without changing temperature
What are some hydrophilic molecules, important for living organisms?
Salt, glucose, cellulose
What are some hydrophobic molecules, important for living organisms?
Fats, hormones
Where do most enzyme catalyst reactions occur?
In water
Are all molecules hydrophilic?
No, function of some molecules in cells depend on them being hydrophobic and insoluble
How are polarity and water’s solvent properties related?
Water’s polarity enables it to dissolve and surround charged ions with water molecules
What are water’s buoyancy levels?
Reasonably high. If an object has a low density, it could flow
What are air’s buoyacy levels?
Almost no buoyancy force
What is the visocosity of water?
Reasonable viscosity for a liquid, due to hydrogen bondsW
What is the viscosity of air?
Almost none, objects move with little resistance
What is the thermal conductivity of water?
Relatively high (for a liquid), which is problematic for warm-blooded organisms b/c they lose heat
What is the thermal conductivity of air?
Relatively low, so organisms are better able to sustain their own temperature
What is the specific heat capacity of water?
High capacity, meaning it requires lots of heat/energy to raise the temperature. This means stable temperatures for aquatic organisms
What is the specific heat capacity of air?
Relatively low, therefore the temperature of air is highly variable
As an ectothermic / cold-blooded organism, is it better to live in water or air?
Water, due to high thermal conductivity and specific heat capacity
As an exothermic / warm-blooded organism, is it better to live in water or air?
Air, due to lower thermal conductivity and lower specific heat capacity
What are the water based adaptations of the Black-throated Loon?
Uses the buoyant forc eof water to float on the surface
Webbed feet and streamlined shape, to combat the viscosity of water that makes movement/diving difficult
Has an oil gland that allows their feathers to be coated with hydrophobic oil. This combats the high risk of heat loss due to high thermal conductivity
The high heat capacity of water means that the Loon can regulate its body temperature during extremes
What are water-based adaptations of the Ringed Seal?
Buoyant forces allow snout to stay on water
Paddle feet and streamlined shape helps to overcome the viscosity of water (helping swimming)
Thick layer of blubber reduces heat loss in a medium with high thermal conductivity
What is extraterrestrial life?
Possibility of living organisms outside Earth
What is an asteroid?
Relatively small rocky object that orbits the sun
What is the Asteroid Theory for Water on Earth?
Asteroids are hydrated rocks that move erratically in space, relatively close to Earth. They can collide with the surface of the Earth. At collision, the asteroids break apart and release liquid H2O.
There is evidence of lots of large asteroid collisions around the time period of the formation of Earth. Another piece of evidence is the D/H (heavy water) ratio for asteroids is very similar to that of Earth
What is the evidence for the Asteroid Theory for Water on Earth?
There is evidence of lots of large asteroid collisions around the time period of the formation of Earth. Another piece of evidence is the D/H (heavy water) ratio for asteroids is very similar to that of Earth
What are the reasons for the retention of water on Earth?
Earth;s temperature suits liquid form of water (with some state changes). Temp is low enough to allow for its condensation
Earth’s gravitational pull holds H2O close to the surface
How are the properties of water related to the search for extraterrestrial life?
Due to water’s essential nature, extraterrestrial life must be found in an area that supports liquid water. It must be in the “Goldilocks Zone”, in which the planet must not be too close to a Sun (water will vapourise) or too far from a Sun (will freeze)
What is the genetic material of all living organisms?
DNA
What is a nucleotide?
Building block of nucleic acids (including DNA and RNA)
What is a polymer?
Substance consisting of large molecules, made up of repeating units
What is a hydroxyl group?
A common chemical group of an oxygen covalently bonded to a hydrogen. The OH is then connected to a larger molecule
What is a condensation reaction?
A chemical reaction that joins two monomers together.
An OH is removed from one, and an H is removed from the other. This facilitates a bond between the monomers
What is messenger RNA?
Copy of one single gene of DNA. Single-stranded and used for protein synthesis with ribosomes
What is transfer RNA?
Small looped RNA strands that bring amino acids based on mRNA instructions
What is ribosomal RNA?
Ribosomes that are made of rRNA and proteins
What is the structure of a nucleotide?
Phosphate group, pentose sugar and a nitrogen base.
What is the structure of Adenosine Triphosphate?
ATP consists of a nitrogenous base (adenine), a ribose sugar and three phosphate groups.
There are high energy bonds between phosphate groups so that, when one breaks off, energy is released
What are the bonds between sugar and phosphate in DNA?
Phosphodiester bonds
What is the result of sugar-phosphate bonding?
The bonds between them make a continuous chain of covalently bonded atoms in each strand of DNA or RNA nucleotides, which form a strong “backbone” of the molecules.
What are the names of the nitrogenous bases in nucleic acids?
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Uracil (U)
What is the structure of DNA?
A double helix made up of two antiparallel strands of nucleotides with two strands linked by hydrogen bonding between complementary base pairs
What are the similarities between DNA and RNA?
Both form nucleic acids, made up of nucleotides
Form strong covalent (phophodiester) bonds between nucleotides, joined by condensation reactions.
Both have the bases of adenine, guanine and cytosine
What are the differences in RNA and DNA (list of traits)?
Number of strands present
Types of nitrogenous bases
Type of sugar
What is the structure of the deoxyribose sugar?
5-carbon pentose sugar with a hydrogen on the 2nd carbon
What is the structure of ribose sugar?
5-carbon pentose sugar with a hydroxyl group on the 2nd carbon
What is the difference between deoxyribose and ribose sugar?
Deoxyribose has one less oxygen at the 2nd carbon
What is the difference between the sugars of RNA and DNA?
DNA has deoxyribose sugar - one less oxygen at the 2nd carbon
RNA has ribose sugar
What is the difference in the nitrogenous bases of DNA and RNA?
In DNA, adenine is complementary to thymine
In RNA, adenine is complementary to uracil
What is the difference between strand structure of DNA and RNA?
DNA forms a double helix, with two antiparallel backbone strands bonded by H-bonds between complementary bases
RNA generally exists in single stranded form
What does each gene code for?
One protein
What is DNA’s purpose?
Instructions for the proteins needed by the body
In what way is DNA diverse?
Any length of DNA molecule and any base sequence is possible.
DNA has an enormous capacity for storing data
Why is there so much DNA?
Each gene of DNA code for one protein. Millions of proteins are needed, therefore there must be a lot of DNA with different lengths and base sequences. These differing lengths and base sequences determine the structure of different proteins and thus, their functions
Why is DNA universal?
All living organisms have the same four bases, and each triplet codon is equivalent to the same amino acid in every living organism.
What is complementarity based upon, in nucleic acids?
Hydrogen bonding
What is the genetic code being across all life forms evidence for?
Universal common ancestry
What is directionality?
Specific alignment of nucleotides, especially whether phosphate is running 5’ to 3’ or 3’ to 5’
What are histones?
Proteins that strands of DNA wrap around, providing support for the chromosome
What are nucleosomes?
A DNA molecules wrapped around the core of eight histone proteins help together by an additional histone protein attached to linker DNA
How many base pairs of DNA are wrapped around a histone?
146
What is meant by replication?
Process where one double-stranded molecules splits and each side is copied, resulting in two new identical replicas of DNA
What is meant by DNA transcription?
When DNA is copied in the nucleus to make mRNA for protein synthesis
What is DNA Translation?
The decoding of instructions to make proteins
How are nucleosomes connected?
Linker DNA
What are the features of a purine base?
Double ringed structure. The rings consist of a hexagon and a pentagon, thus purines are larger than pyrimidines
What are the features of a pyrimidine base?
Single-ringed structure, in the shape of a hexagon
Which nitrogenous bases are purines?
Adenine, guanine
Which nitrogenous bases are pyrimidine?
Cytosine, thymine, uracil
Why must base pairing involve one purine and one pyrimidine?
In order for the DNA double helix to maintain a consistent shape (regardless of base structure)
If both purine = too big
If both pyrimidine = too small for hydrogen bonds to form
What is a phosphodiester bond formed between?
3rd Carbon of the pentose sugar, and the phosphate group
Where can bases be added to?
Only a free 3’ end (therefore, nucleic acids are built 5’ to 3’)
Why are DNA strands antiparallel?
Only way for complementary base pairs to hydrogen bond / be next to each othe
What are the implications of directionality on translation?
At ribosomes, codons are read 5’ to 3’
What are the implications of directionality on transcription?
Only one strand of mRNA is build (from 5’ to 3’)
The 3’ to 5’ is the template strand
What are the implications of directionality on replication?
Leading strand is 3’ to 5’, as it is easy to build 5’ to 3’
Lagging strand is 5’ to 3’ as if it is difficult to build 3’ to 5’ (requires a lot more effort)
What is a bacteriophage?
Virus that invades and infects bacteria.
What are radioisotopes?
Radioactive form of an element, which release particles during their decay to allow for detection
What happens when a bacteriophage invades a bacterial cell?
Bacteriophage inserts DNA into bacteria, which then starts to use viral DNA to make viral parts
What is the supernatant in the Hershey and Chase experiment?
Leftover viral shells after their invasion of bacteria (lighter)
What is the pellet in the Hershey and Chase experiment?
bacterial cells that have been invaded (heavier)
Where is phosphorus found in the bacteriophage?
Inside its DNA core
Where is the sulfur found in the bacteriophage?
Its protein code
What is the tetranucleotide hypothesis?
Idea that structure of DNA contained repeating sequences of four bases, so there were equal numbers of each base
What was the debate that the Hershey and Chase experiment was attempting to resolve?
Whether genetic material was DNA or proteins themselves
What is an example of technological developments opening new possibilities for experiments?
Hershey Chase experiment was possible when radioisotopes were made available as research tools
What were the findings of the Hershey Chase experiment?
DNA is genetic material
What was the knowledge about bacteriophages and viruses that the Hershey Chase experiment relied upon?
Protein (sulfur) was the capsid of the bacteriophage. DNA (phosphorus) is in its core. Both are radiolabelled. When the virus infects the e. coli, genetic material is inserted so that the bacteria begins making the viruses
What are the four steps of the Hershey Chase experiment?
- Expose E. coli to a solution that includes the virus
- Bacteriophage will insert its genetic material only into E. Coli
- Centrifuge it (spin fast to separate by weight)
- Check where each isotope is
What were the results of the Hershey Chase experiment?
Sulfur was higher in the supernatant, where the empty virus parts were.
There was more phosphorus in the pellet, indicating this is the location of the genetic material (therefore, DNA is the genetic material)
What was the Chargraff experiment?
Paper chromatography was used to separate four bases and determine the % of each. Findings were that there were not the same % of each base, which falsified the tetranucleotide hypothesis.
Theory of complementary base pairing was discovered.
What theory did Chargraff’s experiment falsify?
Tetranucleotide hypothesis
What experiment discovered the theory of complementary base pairing?
Chargraff’s. He found that Adenine and Thymine have the same %, and Guanine and Cytosine have the same %
