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A Level Biology Paper 1 > DNA, ATP & Water > Flashcards

DNA, ATP & Water Flashcards

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1
Q

What are the monomers for DNA?

A

DNA nucleotides

Deoxyribonucleic Acid is the polymer

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2
Q

What are the monomers for RNA

A

RNA nucleotides

Ribonucleic Acid is the polymer

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3
Q

What is DNA

A

Deoxyribonucleic Acid
A biological molecule that’s a polymer of DNA nucleotides
A unit of hereditary present in all living organisms
Holds genetic information that codes for a specific sequence of amino acids to produce proteins

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4
Q

Structure of DNA nucleotides

A

Pentose sugar: Deoxyribose
Attached to a phosphate group
Attached to a nitrogenous, organic base (A, T, C, G)

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5
Q

Structure of RNA nucleotides

A

Pentose sugar: Ribose
Attached to a phosphate group
Attached to a nitrogenous, organic base (A, T, C, G)

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6
Q

Which bases are found in DNA

A

Adenine + Thymine

Cytosine + Guanine

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7
Q

Which bases are found in RNA

A

Adenine + Uracil

Cytosine + Guanine

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8
Q

Why is DNA ‘deoxy-‘

A

Missing an oxygen atom on the carbon 2 of the pentonse sugar so its just H not OH

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9
Q

Which bases are purine?

A

Adenine
Guanine

2 ringed bases

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10
Q

What bases are pyrimidine

A

Thymine
Cytosine
Uracil

1 ringed base

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11
Q

What bonds are present in DNA

A

Weak hydrogen bonds between complementary base pairs
2 between Adenine and Thymine
3 between Cytosine and Guanine

Phosphodiester bonds between the phosphate group of one nucleotide and the 3rd carbon on the pentose sugars adjacent nucleotide

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12
Q

What is DNAs structure

A

Double helix
Consisting of 2 polynucleotide chains of DNA nucleotides
Wound together and held in place by weak hydrogen bonds between complementary base pairs
Antiparallel strands

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13
Q

What is a sugar-phosphate backbone

A

Structural component of DNA consisting of phosphodiester bonds
Between the phosphate group of one nucleotide and the 3rd Carbon on the adjacent one
Makes nucleic acid very strong and stable

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14
Q

What is mRNA

A

A relatively short polynucleotide chain
A single stranded molecule
Used to transfer genetic information from DNA to ribosomes

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15
Q

Explain antiparallel

A

2 strands of DNA running in opposite directions

Both have a 5’ and 3’ end but in opposite directions

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16
Q

Explain the ends of DNA

A

5’ (5 prime end): end that has a phosphate group attached to the Carbon 5 on the deoxyribose sugar

3’ (3 prime end): end that has a hydroxyl group attached to the Carbon 3 on the deoxyribose sugar

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17
Q

Why are the ends of DNA important

A

Important when making proteins because it ensures only one strand is read to make it
Important in DNA replication because DNA polymerase is only complementary by its active site to the 5’ end (phosphate group)

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18
Q

How does DNA structure allow it to function

7

A

Sugar phosphate backbone and double helix structure

  • provides strength and stability
  • protects bases in the code
  • protects hydrogen bonding between bases

Long/large molecule
-stores lots of information

Helical/coiled structure
-compact

Base sequence
-codes for amino acids for protein

Double stranded
-semi conservative replication, both templates

Complementary base pairing
-allows for accurate replication

Hydrogen bonding

  • collectively strong makes it a stable molecule
  • weak so easily separated for semi conservative replication
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19
Q

What are the 3 types of replication

A

Semi conservative
Conservative
Dispersive

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20
Q

Outline semi conservative replication

A

Each new DNA molecule contains one original template strand and one new synthesised strand, making it identical to the original
Each strand acts as a template

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21
Q

What is dispersive replication

A

Original strands break and recombine
New strand is synthesised in between the fragments
Leaving a hybrid of new and old strands
Parents DNA dispersed throughout both strands

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22
Q

What is conservative replication

A

Parent strands separate to act as templates and when two new strands are synthesised the new ones join up and the parents join back up
1 molecule 100% original
1 molecule 100% new

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23
Q

Explain semi conservative replication

A

DNA helicase unwinds the double helix, separating the strands
By breaking the weak hydrogen bonds between complementary base pairs
Both strands act as templates
Free DNA nucleotides are attracted to their complementary base pairs
(A to T and C to G)
DNA polymerase binds to 3’ of template strand and had an active sight complementary to the 5’ of free nucleotides
Joins adjacent nucleotides together by phosphodiester bonds
Synthesising DNA in a 5’ to 3’ direction
Leaving 2 DNA molecules, both identical and with one original and one new strand

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24
Q

How does DNA polymerase work

Study These Flashcards
A

A complementary binding site to the 3’ end of template strand
A complementary active site to the 5’ end of free nucleotides
Synthesises in a 5’ to 3’ direction only
Strands are antiparallel

25
Explain Messelson and Stahls experiment
Grew ecoli DNA in N15 because nitrogenous bases used nitrogen Isolated a DNA molecule Spun it in a centrifuge Removed DNA and grew it in N14 for one replication round Spun again Repeated 4 times
26
Explain Messelson and Stahls results
Generation 0: N15N15=1 molecule 100% N15 Generation 1: N14N15=2 molecules 50% N15 Generation 2: N14N14/N14N15=2 molecules 50% N15, 2 molecules 100% N14 Generation 3: N14N14/N14N15=2 molecules 50% N15, 6 molecules 100% N14
27
How did the results prove semiconservative replication
After 1 generation semi conservative would give a band in the middle because half is N14 half is N14 SEE NOTES?????
28
DNA polymerase function in DNA replication
Synthesises phosphpdiester bonds Between adjacent nucleotides Via condensation reaction
29
What is ATP
Adenosine Triphosphate Nucleotide derivative Consisting of a ribose sugar, 3 phosphate groups and a nitrogenous base adenine Produced in the mitochondria in respiration or photosynthesis
30
Explain the hydrolysis of ATP
ATP is hydrolysed into Pi and ADP Via ATP hydrolase Releasing small manageable packets of energy It is the terminal high energy bond between the 2nd and 3rd phosphate group that's broken Via a hydrolysis reaction Releasing small manageable packets of energy Pi can phosphorylate other compounds to make them more reactive
31
Explain the resynthesis of ATP
ADP and Pi (phosphorylation) Catalysed by ATP synthase in a condensation reaction Requires energy to add the phosphate group to ADP to form ATP, creating a high energy bond Occurs in photosynthesis and respiration
32
Why is ATP useful/how is ATP a sustainable energy source
Releases small manageable packets of energy: little lost as heat energy Releases energy instantaneously: efficient Pi can be used to phosphorylate other compounds: more reactive Can be rapidly resynthesised: continous energy source Does not leave the cell Soluble: most active processes occur in aqueous solutions
33
Where does ATP synthesis occur
Photosynthesis | Respiration
34
ATP vs DNA nucleotide
ATP has 3 phosphate groups/DNA nucleotide only one ATP has a ribose sugar/DNA nucleotide have deoxyribose sugar ATP base is always adenine/DNA nucleotide can be 4 different ones (including adenine) (ATCG)
35
How is the hydrolysis of ATP used in cells
Phosphorylate other compounds and make them more reactive Releases energy for other processes such as protein synthesis, active transport, muscle contraction, semi-conservative replication
36
What is water
A dipole molecule consisting of 1 oxygen and 2 hydrogen Major component of the cytoplasm Slightly negative on oxygen because more protons so pulls electrons closer to its nucleus and since electrons are negative it makes it more negative Slightly positive on both hydrogens because electrons pulled away from it and closer to oxygen Unequal sharing of electrons
37
Why is oxygen a polar molecule
Charged | Unequal sharing of electrons
38
How does water act as a solvent
Dipole molecule So polar molecules can dissolve in it Universal solvent because can dissolved more molecules than any other liquid Major component of the cytoplasm because allows chemicals and enzymes to dissolve So essential for chemical reactions to occur
39
Why is water considered a universal solvent
Can dissolve more molecules than any other liquid
40
Explain waters cohesion
Dipole molecule Slightly negative oxygen of one water molecule attracted to the slightly positive hydrogen of another Forming a hydrogen bond Individually weak (compared to covalent bonds) But in large numbers very strong When hydrogen bonds form between two water molecules
41
Explain waters adhesion
When hydrogen bonds form between water and another type of molecule Dipole molecule Slightly negative oxygen of one water molecule attracted to the slightly positive hydrogen of another molecule or vice versa Forming a hydrogen bond Individually weak (compared to covalent bonds) But in large numbers very strong
42
Why can some insects walk on water
Surface tension created due to waters cohesion | Insects are light enough jot to break the hydrogen bonds between water molecules
43
Ways that water acts as a metabolite
Hydrolysis and photosynthesis use water Condensation and respiration produce water Chemical reactions taking place in aqueous mediums Enzymes and substrates can diasolve in water and react
44
Explain waters specific heat capacity
Large/high Requires a lot of heat energy to heat it up Because it has lots of hydrogen bonds Provides a habitat in water because can resist temperature fluctuations Organisms have optimum temperature to function Organisms mostly water (70%) so protects them against sudden temperature changes
45
Explain waters latent heat of vaporisation
Large/high Takes a lot of heat energy to break hydrogen bonds in water Hydrogen bonds increase the energy required to evapourate water Lots of body heat is required to evaporate water in small volumes (sweat) So lowers internal body temperature of organism
46
Explain waters cohesion in plants
Surface tension allows water to be pulled up xylem vessels in continuous columns Water also pulled back into a body rather than escaping it
47
What can water dissolve
Gases: O2 can be transported from the lungs to respiring tissue, CO2 can be transported from respiring tissue to lungs Waste: Ammonia and urea made in cells to be transported to kidneys and excreted Inorganic ions, amino acids, ATP, monosaccharided Enzymes and globular proteins
48
Benefits of water being transparent
Plants under water can photosynthesise | Light can pass through the eyeball
49
Benefits of water being hard to compress
Turgor (support) in plants | Hydroskeleton in worms
50
Benefits of ice being less dense than water
Habitats for animals Insulates the water below and stops it all freezing Allows nutrients to be cycled
51
Why is water denser than ice
Ice has the same mass as water But takes up a bigger volume Because molecules for crystalline structures Density = mass/volume So same mass but greater volume means ice has a lower density
52
List 8 inorganic ions
``` Hydrogen (H+) Hydroxide (OH-) Iron (Fe²+ / Fe³+) Sodium (Na+) Phosphate (PO4³-) Nitrites (NO2-) Nitrates (NO3-) Chloride (Cl-) ```
53
Use of hydrogen ions
Affects acidity of solutions (pH) | Used in respiration and photosynthesis to provide energy to make ATP
54
Uses of hydroxide ions
Affects acidity of solutions (pH)
55
Uses of Iron ions
Structural component of haemoglobin | Binds to oxygen to allow transport of it to respiring cells
56
Uses of sodium ions
Used in contransport of glucose and amino acids from lumen of small intestines into intestinal epithelial cells Changes water potential of immediate area Used in nervous conduction
57
Uses of phosphate ions
Components of phospholipids (cells and organelles membranes) DNA RNA ATP
58
Uses of nitrate ions and nitrate ions
Taken up from soil by plant roots then used to make amino acids
59
Uses of chloride ions
Uses in regulating the water potential or the small intestine

A Level Biology Paper 1 (16 decks)

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