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TOPIC 1 - CH 2 Flashcards

Nucleic acids (67 cards)

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1
Q

What are the monomers of nucleic acids?

A

Nucleotides

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2
Q

Which 3 components make up a nucleotide?

A
  1. pentose sugar
  2. nitrogenous base
  3. phosphate group
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3
Q

Describe how nucleotides join together

A

-condensation reactions
-involves loss of water
-forms phosphodiester bonds
-between sugar and phosphate

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4
Q

Which sugar and nitrogenous bases do DNA nucleotides contain?

A

Sugar deoxyribose
Bases:
- Adenine
- Thymine
- Cytosine
- Guanine

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5
Q

What is the difference between a purine and a pyrimidine, and which DNA bases belong to each group?

A

Purines are larger and have 2 carbon ring structures (A &G)
Pyrimidines are smaller and only have 1 carbon ring structure (T & C)

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6
Q

Which type of bond forms between complementary base pairs in DNA?

A

Hydrogen bonds

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7
Q

Which DNA base is complementary to adenine, and how many hydrogen bonds for between them in a molecule of DNA?

A

Thymine
2 hydrogen bonds

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8
Q

Which DNA base is complementary to cytosine, and how many hydrogen binds form between them in a molecule of DNA?

A

Guanine
3 hydrogen bonds

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9
Q

Which sugar and nitrogenous bases do RNA nucleotides contain?

A

Ribose
Bases:
- Adenine
- Uracil
- Cytosine
- Guanine

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10
Q

Which RNA base forms a complementary pair with adenine?

A

Uracil

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11
Q

What is the general structure of an RNA molecule?

A
  • single-stranded
  • one polynucleotide strand
  • ribose sugar
  • organic bases - adenine, guanine, cytosine, uracil
  • phosphate group
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12
Q

What are the similarities between DNA and RNA?

A

-Both made up if nucleotides
-Both contain phosphodiester binds
-Both contain pentose sugar, phosphate, nitrogenous bases
-Both contain bases C, G, and A

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13
Q

What are the differences between DNA and RNA?

A

-DNA is longer than RNA
-DNA is double-stranded, RNA is single-stranded
-DNA contains thymine, RNA contains uracil
-DNA contains deoxyribose, RNA contains ribose

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14
Q

What is semi-conservative replication?

A

Each of the newly synthesised DNA molecules is made up of one original DNA stand and one new DNA strand

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15
Q

What is the role of DNA helicase in DNA replication?

A

DNA helicase breaks bonds between complementary bases to unwind the double helix and separate the strand

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16
Q

What is the role of ATP?

A

To act as an energy source

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17
Q

Which class of biological molecules does ATP belong to?

A

Nucleotides

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18
Q

How many phosphate groups does ATP contain?

A

3

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19
Q

What is the name of the sugar in ATP?

A

Ribose

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20
Q

Which nitrogenous base does ATP contain?

A

Adenine

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21
Q

Which product of ATP hydrolysis makes other compounds more reactive?

A

inorganic phosphate

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22
Q

How does adding an inorganic phosphate to another compound affect its reactivity?

A

Makes it more reactive

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23
Q

Is ATP broken down via hydrolysis or condensation reaction and how?

A

Hydrolysis
which breaks ATP into ADP + inorganic phospahte

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24
Q

Name the two products of ATP hydrolysis

A
  1. ADP (adenosine diphosphate)
  2. Pi (inorganic phosphate)
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25
Which enzyme is responsible for synthesising ATP?
ATP synthase via condensation reaction
26
Which feature if ATP means that little energy is lost as heat?
It releases a small amount of energy
27
Which elements does a water molecule contain?
- Hydrogen - Oxygen
28
How many hydrogen atoms does a water molecule contain?
2
29
How does DNA and RNA differ in function?
DNA holds genetic information RNA transfers genetic information from DNA to ribosomes
30
What are ribosomes formed from?
RNA and proteins
31
What is the structure of DNA?
- two strands of polynucleotides - joined togethere by hydrogen bonds between certain bases - phosphate and deoxyribose alternate to to form sugar-phosphate backbone - forms a double helix
32
What are phosphodiester bonds and how are they helpful?
strong covalent bonds ensure the genetic code is not broken down between sugar and phosphate group
33
What 2 things make DNA stable?
- phosphodiester backbone protects thee moree chemically reactive organic bases inside the double helix - C-G pairings have 3 hydrogen bonds between them so a higher proportion of this pairings makes DNA more stable
34
Why is complementary base pairing important?
helps maintain the order of the genetic code when DNA replicates
35
How is DNA adapted to carry out its functions (5)?
- stable structure due to phosphodiester bonds and double helix = persistent mutations rare - double-stranded so replication can occur using both strands as a template - large molecule to carry lots of information - weak hydrogen bonds for easy unzipping of the two strands during replication - complementary base pairings allows identical copies to replicated and transfered as mRNA
36
Why must DNA be replicated before a nucleus divides?
to ensure all daughter cells have the same genetic information to produce the enzymes and proteins needed
37
What are the 4 requirements for semi-conservative replication to take place?
- 4 types of nucleotides with their bases present - both strands of DNA act as template - enzyme DNA polymerase - source of energy
38
Describe the process of semi-conservativee replication
1. DNA helicase breaks the hydrogen bonds between complementary base pairs, unwinding the double helix 2. Exposed DNA nucleotides on template strand are attactred to free nucleotides and bind by base pairings 3. DNA polymerase joins adjacemt nucleotides forming a phosphodiester bond via a condensation reaction 4. New DNA molecule contains one of the original DNA strands 2 identical DNA molecules created
39
Who discovered the structure of DNA?
Watson and Crick helped by Franklin
40
Wo determined that DNA replication is semi-conservative?
Meselson and Stahl
41
What 3 facts did Meselson and Stahl base their work on?
- all bases in DNA contain nitogen - there is lighter nitrogen, 14N and heavier nitrogen, 15N - bacteria will incorporate nitrogen from their growing meedium into any new DNA that they make
42
What is the evidence for semi-conservative replication?
Meselson and Stahl - grew bacteria on medium of 15N then 14N for a single generation to allow it to replicate once - found one heavy and one light strand giving mixed DNA molecule did this by extracting DNA, suspending it in solution, centrifuged it to see if DNA was light or heavy
43
What is the structure of ATP?
- ribose - adenine - 3 phosphate groups
44
What is the role of ATP?
immediate source of energy for biological processes metabolic reactions in cells must have a constant steady supply of ATP
45
What catalyses the hydrolysis reaction of ATP to ADP?
ATP hydrolase
46
Why are the bonds between the 3 phosphate groups in ATP easily broken and why is this useful?
they are unstable so have a low activation energy when they break they release lots of energy usually only the terminal phosphate is removed
47
What is the reversible equation for ATP/ADP?
ATP + H20 -> ADP +Pi +E
48
When is the resynthesis of ATP catalysed?
during -photosynthesis -respiration
49
The synthesis of ATP from ADP involves the addition of what?
a phosphate molecule to ADP
50
What ar the 3 ways in which the synthesis of ATP can occur?
- photophosphorylation - chlorophyll containing plant cells during photosynthesis - oxidative phosphorylation - in plant and animal cells during respiration - substrate-level phosphorylation - in plant and animal cells when phosphate groups are transferred from donor molecules to ADP
51
The inorganic phosphate can be used to phosphorylate other compounds. What is meant by this?
makes compounds more reactive
52
How is ATP a better immediate energy source than glucose (2)?
- energy released in smaller, more manageable quantities - hydrolysis of ATP to ADP is a singlee reaction, shorter than breakdown of glucos
53
Why does ATP need to b continuously made in the mitochondria?
ATP cannot be stored
54
What 5 processes is ATP required in?
- metabolic - building macromolecules - movement - muscle contraction as filaments of muscle slide past one another - active transport - change shape of carrier proteins for molecules to move against conc gradient - secretion - form lysosomes - activation of molecules - phosphorylation = lowers activation energy in enzyme-catalysed reactions
55
Describe the dipolar nature of water
2 hydrogen, 1 oxygen oxygen slightly negative, hydrogen slightly positive overnall no charge
56
How do hydrogen bonds form between watre molecules?
positive pole (hydrogen) attracted to negative pole (oxygen) although each bond is fairly weak but molecules stick together
57
What are the 5 key properties of water?
1 - metabolite hydrolysis and condensation reactions 2 - solvent dissolves other substances for metabolic reactions to occur 3 - high heat capacity buffer temperature changes hydrogen bonds = takes more heat 4 - large latent heat of vaporisation provides a cooling effect with loss of water through evaporation hydrogen bonds = takes more energy 5 - strong cohesion supports water columns and provides surface tension where water meets air due to hydrogen bonding
58
What is the benefit of water being tranparent?
aquatic plants can photosynthesise and light rays penetrate fluid in eye to reach retina
59
Where are inorganic ions found?
in solution in the cytoplasm and body fluids
60
Suggest why the base pairings of adenine with cytosine and guanine with thymine do not occur.
the bases are linkd by hydrogen bonds the molecular structures could be such that hydrogen bonds do not form between adnine and cytosine etc.
61
Assess the advantages of scientists questioning the validity of a current theory rather than automatically accepting it
alternative theories can be explored and investigated new facts may emerge and a new theory is made or an existing one is modified = scientific progress
62
Define hypothesis
a suggested explanation of something based on some logical scientific reasoning or idea
63
Explain why DNA polymerase can only attach nucleotides to the hydroxyl group on the 3 carbon molecule
enzymes are very specific they have active sites the shape of th 3' end of the molcule with its hydroxyl group fits the active site of DNA polymerase whereas th shape of the 5' end does not
64
If an inhibitor of DNA polymerase were introduced into a cell, explain what the effect would be on DNA replication?
the linking together of the new nucleotides could not take place while the nucleotides would match, they would not join together to form a new strand
65
Explain why ATP is referred to an immediate energy source.
- releases energy rapidly - single-step - transferred directly to the reaction requiring it - too unstable to be a long term store
66
Explain how ATP can make an enzyme-catalysed reaction take place more readily
ATP provides a phosphate that can attach to another molecule making it more reactive = lowering activation energy less work = function more readily
67
Summarise water
A water molecule is said to be dipolar because it has a positive and a negative pole as a result of the uneven distribution of electrons within it. This creates attractive forces called hydrogen bonds between water molecules, causing them to stick together. This stickness of water means that its molecules are pulled inwards at its surface. This force is called surface tension. Water is able to split large molecules into smaller ones by a process known as hydrolysis. Water is the raw material for the process of photosynthesis in green plants.
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