Topic 1 - More Biological molecules Flashcards
1
Q
what does DNA stand for
Nucleic Acid
A
deoxyribonucleic acid
2
Q
what’s DNA’s function ?
Nucleic Acid
A
it’s used to store genetic information - all the information needed for an organism to grow and develop from a fertilised egg to a fully grown adult
3
Q
what does RNA stand for
Nucleic Acid
A
ribonucleic acid
4
Q
what is the function of RNA ?
Nucleic Acid
A
to transfer genetic information from the DNA to the ribosomes.
5
Q
what type of molecules are DNA and RNA
Nucleic Acid
A
nucleic acid
6
Q
what are RNA and DNA polymers of ?
Nucleic Acid
A
nucleotides
7
Q
what’s the structure of a nucleotide ? Draw it
Nucleic Acid
A
a phosphate group joined to a pentose sugar which is joined to a nitrogen containing organic base
8
Q
what’s the pentose sugar in RNA ?
Nucleic Acid
A
ribose
9
Q
what are the four possible bases in DNA
Nucleic Acid
A
Adenine and thymine. cytosine and guanine
10
Q
what are the four bases in RNA
Nucleic Acid
A
adenine and uracil. guanine and cytosine
11
Q
what’s a polynucleotide
Nucleic Acid
A
polymer of nucleotides
12
Q
how are polynucleotides formed
Nucleic Acid
A
- a condensation recruit between the phosphate group of one nucleotide and the pentose sugar of another.
- this forms a phosphodiester bond.
- Catalysed by DNA polymerase.
13
Q
What’s the structure of DNA ?
Nucleic Acid
A
- DNA is made of two polynucleotide strands in a double helix structures.
- two dna polynucleotide strands consist of nucleotides joined together by phosphodiester bonds.
- nucleotides consist of a phosphate group a pentose sugar (deoxyribose) and a nitrogen containing base. the polynucleotide strands join together by hydrogen bonding between the bases.
- each base can only join with one particular base this is called complimentary base pairing( adenine and thymine have 2 hydrogen bonds and cytosine and guanine have 3).
- the two anti parallel polynucleotide strands twist to form the dna double helix
14
Q
Who discovered the DNA double helix ?
Nucleic Acid
A
Crick and watson
15
Q
what’s the structure of RNA
Nucleic Acid
A
a relatively short polynucleotide chain (not a double helix) it’s much shorter than most DNA polynucleotides
16
Q
What does semi conservative replication allow for
Nucleic Acid
A
genetic continuity throughout generations of cells
17
Q
Explain the process of semi conservative replication
Nucleic Acid
A
- the enzyme DNA helicase breaks down the hydrogen bonds between the bases on the two polynucleotide DNA strands. this causes the helix to unwind to form two single strands.
- each original strand acts as a template for a new strand. complimentary base pairing means that free floating dna nucleotides are attracted to their complimentary exposed bars on each original template strand- A to T and C to G.
- Condensation reactions join the nucleotides together of the new strand to form phosphodiester binds making a polynucleotide chain this is catalysed by the enzyme dna polymerase. hydrogen bonds form between the bases on the original and new strands.
- each new dna molecules contains one strand from the original molecule and one new strand.
18
Q
what does semi conservative replication mean ?
Nucleic Acid
A
each new dna molecule has a strand from the original dna molecule and a new strand.
19
Q
what end is the active side of DNA polymerase complimentary to ? What does this result in ?
Nucleic Acid
A
- DNA polymerase is complimentary to the 3’ end of the template strand, so enzymes can only add nucleotides to the new strand at the 3’ end.
- This means that the new strand is made in a 5’ to 3’ direction as DNA polymerase moves down the template strand in a 3’ to 5’ direcion and the 2 strands are antiparallel.
20
Q
Who came up with the theory of semi conservative replication ?
Nucleic Acid
A
Crick and Watson.
21
Q
Explain the experiment that Meleson and Stahl carried out to prove semi conservative replication.
Nucleic Acid
A
- Two samples of bacteria were grown, one in a nutrient broth containing light nitrogen, and another in heavy nitrogen. As the bacteria replicated.they took up nitrogen from the nutrient broth to make nucleotides for the new DNA strand - the nitrogen became apart of the bacteria’s DNA.
- A some of DNA was taken from each batch and was spun in a centrifuge. The DNA from heavy nitrogen settled lower compared to the DNA from light nitrogen which settled higher up as its lighter.
- Then the heavy nitrogen bacteria sample was put into a nutrient broth solution containing light nitrogen. The bacteria were left for one round of DNA replication and then a sample was taken and spun in a centrifuge.
- If replication was conservative, the original heavy DNA would settle at the bottom and the light at the top. If replication was semi conservative the new DNA sample would contain one original heavy nitrogen strand and one new light nitrogen strand. So the DNA would settle in the middle of the light and heavy nitrogen samples.
- The DNA settled in the middle proving it contained both heavy and light nitrogen. The bacteria replicated semi conservatively in the light nitrogen.
22
Q
What atoms to water contain ?
Water
A
Two hydrogen atoms and one oxygen atom (H2O).
23
Q
How is a single water joined together ?
Water
A
By shared electrons between the 2 hydrogen atoms and the oxygen atom.
24
Q
Explain why Water molecules are a polar molecule ?
Water
A
- Because the shared negative hydrogen electrons are pulled towards the oxygen atom, the other side of the hydrogen atom is left with a slightly positive charge.
- The unshared negative electrons on the oxygen atom give in a slight negative charge.
- This makes water a polar molecule
25
How are water molecules attracted to each over ?
## Footnote
Water
* The slightly negatively charged side of the oxygen atoms is attracted to the slightly positively side of the hydrogen atoms of other water molecules.
* This attraction is hydrogen bonding.
26
Explain why water is a useful metabolite ?
## Footnote
Water
* Many metabolic reactions involve condensation and hydrolysis reactions
* A hydrolysis reaction requires a water molecule to break bonds and a condensation reaction releases a water molecule as a new bond is formed.
27
Explain what large latent heat of vapourisation is and why it’s a useful property of water.
## Footnote
Water
* It takes a lot of heat energy to break the hydrogen bonds between water molecules so water has a high latent heat of vaporisation
* a lot of energy is used up when water vaporises (evaporates).
* This is useful for living organisms because it means that they can use water loss through evaporation to fool town (e.g. sweat) without loosing too much water.
28
What is high specific heat capacity and why is it a useful property of water ?
## Footnote
Water
* The hydrogen bonds between the water molecules can absorb alot of energy.
* So water has a high specific heat capacity; it takes alot of energy to raise 1g of water by 1°c.
* This is useful for living organism because it means that water doesn’t change temperature rapidly, making water a good habitat because temperature underwater is more likely to be stable than on land.
* Also, the water inside organisms remains at a fairly stable temperature, helping them to maintain a constant body internal temperature.
* It can resist changes in temperature.
29
Why is water being a solvent a good property ?
## Footnote
Water
* A lot of important substances in metabolic reactions are ionic (e.g. salt) .
* This means they’re make by one positively charged atom or molecule and a negatively charged atom or molecule. Because water is polar, the positive end of a water molecule will be attracted to the negative ion and the negative end of a water molecule will be attracted to the positive ion.
* This means that the ions will get totally surrounded by water molecules meaning they’ll dissolve.
30
What’s cohesion and why is it a good property of water ?
## Footnote
Water
* Cohesion is the attraction of molecules of the same type (e.g. 2 water molecules).
* Water molecules are very cohesive (stick together) because they’re polar.
* Strong cohesion helps water to flow, making it great for transporting substances (e.g. water moving in columns in xylem).
* Strong cohesion also means that water has a high surface tension when it comes to contact with air.
* This is why sweat forms in droplets on the skin which evaporates to cool the organism also it’s why some animals can walk on ponds.
31
How much of the cells contents is made up of water ?
## Footnote
Water
80%.
32
What does ATP stand for ?
## Footnote
ATP
Adenosine triphosphate.
33
Why is ATP made ?
## Footnote
ATP
* Plants and animal cells release energy from glucose, this is called respiration, a cell can’t get its energy directly from glucose.
* So in respiration, the energy released from glucose is used to make ATP.
34
What is ATP made from ? Draw it.
## Footnote
ATP
A nucleotide base adenine, combined with a ribose sugar and three phosphate groups.
35
Why’s ATP known as a nucleotide derivative ?
## Footnote
ATP
It’s a modified form of a nucleotide.
36
What happens to ATP once it’s made ? And how is the energy released ?
## Footnote
ATP
* Once made, ATP diffuses to the part of the cell that needs energy.
* The energy in ATP is stored in high energy bonds between the phosphate groups and is realises via a hydrolysis reaction.
37
How is energy released from ATP ?
## Footnote
ATP
* ATP is broken down into ADP (adenosine diphosphate) and Pi (inorganic phosphate).
* This is a hydrolysis reaction.
* A bond between the phosphate groups is broken and energy is released. The reaction is catalysed by ATP hydrolase.
* ATP hydrolysis can be coupled to other energy requiring reactions in the cell- meaning the energy can be used to make the coupled reaction happen.
38
How can the inorganic phosphate be put to good use ?
## Footnote
ATP
It can be added to another compound this is phosphorylation and often makes the compound more reactive.
39
what ways is ATP hydrolysis used in cells.
## Footnote
ATP
* To phosphorylate other compounds to make them more reactive.
* To provide energy for other reactions.
40
How can ATP be res-synthesised ? And when does this happen ?
## Footnote
ATP
* In a condensation reaction between ADP and a phosphate group (Pi).
* This happens during both respiration and photosynthesis.
* Its catalysed by the enzyme ATP synthase.
41
Why is ATP a good source of energy in cells ?
## Footnote
ATP
* It releases little heat energy less danger of thermal death.
* it releases energy instantaneously.
* it phosphorylates other compounds, making them more reactive.
* can be rapidly re synthesised.
* Does not leave cells.
42
What’s an ion ?
## Footnote
Inorganic Ions
An atom or a group of atoms with an electric charge.
43
What’s an ion with a positive charge ?
## Footnote
Inorganic Ions
A cation.
44
What’s an ion with a negative charge ?
## Footnote
Inorganic Ions
An anion.
45
What’s an inorganic ion ?
## Footnote
Inorganic Ions
An ion that doesn’t contain carbon.
46
What’s the function of Iron ion ?
## Footnote
Inorganic Ions
* Haemoglobin is a large protein that carries oxygen around the body, in red blood cells.
* It’s made up of 4 polypeptide chains each with an iron ion (Fe2+) in the centre.
* Its the iron ion that binds oxygen to haemoglobin. when oxygen is bound the iron ion temporarily turns into a Fe3+until oxygen is released.
47
What’s the function of hydrogen ions ?
## Footnote
Inorganic Ions
* pH is calculated based on the concentration of hydrogen ions (H+) in the environment.
* The more hydrogen ions present the lower the pH is (the more acidic the solution is).
48
What’s the function if sodium ions ?
## Footnote
Inorganic Ions
* Glucose and amino acids need help crossing membranes.
* A molecule of glucose or an amino acid can be transported into a cell along side sodium ions this is called co-transport.
* Creates a sodium concetration/diffusion gradient. Affects osmosis/water potential.
49
What’s the function of phosphate ions ?
## Footnote
Inorganic Ions
* Phosphorylates other compounds.
* Used to produce ATP.
* The phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides.
* affects water potential/osmosis.
