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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

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
Q

Explain Messelson and Stahls experiment

A

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
Q

Explain Messelson and Stahls results

A

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
Q

How did the results prove semiconservative replication

A

After 1 generation semi conservative would give a band in the middle because half is N14 half is N14
SEE NOTES?????

28
Q

DNA polymerase function in DNA replication

A

Synthesises phosphpdiester bonds
Between adjacent nucleotides
Via condensation reaction

29
Q

What is ATP

A

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
Q

Explain the hydrolysis of ATP

A

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
Q

Explain the resynthesis of ATP

A

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
Q

Why is ATP useful/how is ATP a sustainable energy source

A

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
Q

Where does ATP synthesis occur

A

Photosynthesis

Respiration

34
Q

ATP vs DNA nucleotide

A

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
Q

How is the hydrolysis of ATP used in cells

A

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
Q

What is water

A

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
Q

Why is oxygen a polar molecule

A

Charged

Unequal sharing of electrons

38
Q

How does water act as a solvent

A

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
Q

Why is water considered a universal solvent

A

Can dissolve more molecules than any other liquid

40
Q

Explain waters cohesion

A

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
Q

Explain waters adhesion

A

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
Q

Why can some insects walk on water

A

Surface tension created due to waters cohesion

Insects are light enough jot to break the hydrogen bonds between water molecules

43
Q

Ways that water acts as a metabolite

A

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
Q

Explain waters specific heat capacity

A

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
Q

Explain waters latent heat of vaporisation

A

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
Q

Explain waters cohesion in plants

A

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
Q

What can water dissolve

A

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
Q

Benefits of water being transparent

A

Plants under water can photosynthesise

Light can pass through the eyeball

49
Q

Benefits of water being hard to compress

A

Turgor (support) in plants

Hydroskeleton in worms

50
Q

Benefits of ice being less dense than water

A

Habitats for animals
Insulates the water below and stops it all freezing
Allows nutrients to be cycled

51
Q

Why is water denser than ice

A

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
Q

List 8 inorganic ions

A 
Hydrogen (H+)
Hydroxide (OH-)
Iron (Fe²+ / Fe³+)
Sodium (Na+)
Phosphate (PO4³-)
Nitrites (NO2-)
Nitrates (NO3-)
Chloride (Cl-)
53
Q

Use of hydrogen ions

A

Affects acidity of solutions (pH)

Used in respiration and photosynthesis to provide energy to make ATP

54
Q

Uses of hydroxide ions

A

Affects acidity of solutions (pH)

55
Q

Uses of Iron ions

A

Structural component of haemoglobin

Binds to oxygen to allow transport of it to respiring cells

56
Q

Uses of sodium ions

A

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
Q

Uses of phosphate ions

A

Components of phospholipids (cells and organelles membranes)
DNA
RNA
ATP

58
Q

Uses of nitrate ions and nitrate ions

A

Taken up from soil by plant roots then used to make amino acids

59
Q

Uses of chloride ions

A

Uses in regulating the water potential or the small intestine

A Level Biology Paper 1 (16 decks)

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