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Biology🧬 > Biological molecules: nucleic acids > Flashcards

Biological molecules: nucleic acids Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What does a nucleotide contain?

A
  • A phosphate group
  • A pentose sugar
  • A nitrogen-containing base
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2
Q

What does a DNA nucleotide contain?

A
  • A DEOXYRIBOSE sugar
  • A phosphate group
  • A nitrogen-containing base
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3
Q

What is the pentose sugar in RNA called?

A

Ribose

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4
Q

What are purines?

A

(nitrogenous base)

  • Adenine
  • Guanine

They have a double ring

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5
Q

What are pyrimidines?

A

(nitrogenous bases)

  • Thymine
  • Cytosine
  • Uracil (RNA)

They have a single ring

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6
Q

What is the bond between the phosphate group and the sugar?

A

Phosphodiester bond

  • joins the monomers to make the polymer DNA
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7
Q

What is the reaction the makes the phosphodiester bond?

A

Condensation reaction

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8
Q

What are complementary base pairs held together by?

A

Hydrogen bonds

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9
Q

What base pairs have 3 hydrogen bonds?

A
  • Cytosine
  • Guanine
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10
Q

What base pairs have 2 hydrogen bonds?

A
  • Adenine
  • Thymine
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11
Q

What is DNA used for in our body?

A

(deoxyribonucleic acid) is the store of genetic information that codes for proteins to help us grow and develop.

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12
Q

What is the function of RNA?

A

(ribonucleic acid) comes in the form of transfer (tRNA) or messenger (mRNA), or ribosomal (rRNA).

It transfers genetic information of the DNA to ribosomes to make proteins.

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13
Q

What is semi-conservative replication?

A

‘Unzipping’ DNA so that new polynucleotides can use it as a template and synthesise. This is how DNA is copied.

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14
Q

Explain the process of semi-conservative replication

A
  1. The enzyme Helicase breaks the hydrogen bonds between the 2 polynucleotide strands, the point of separation is called the replication fork.
  2. The original strands act as a template, and the formation of the new strand is catalysed by DNA polymerase.
  3. The bases are read and free floating polynucleotides then bond (hydrogen) to their complementary base pair on the original strand by condensation reactions.

So each new DNA molecule now has one new and one original strand.

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15
Q

Explain why DNA polymerase works in opposite ways during semi-conservative replication

A

DNA polymerase reads the parent strand in a 3’ to 5’ direction therefore builds the Leading strand in a 5’ to 3’ direction as the strands are opposites, towards the replication fork.

Because they are opposites, that means the the other parent strand is facing the opposite way in a 5’ to 3’ direction so the Lagging strand is now built in 3’ to 5’, away from the replication fork.

The strands are antiparallel.

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16
Q

How does the lagging strand grow in semi-conservative replication?

A

Discontinuously in small sections called Okazaki fragments, e.g the middle first, then the top, which are then joined together by DNA ligase.

17
Q

What are the 3 types of replication (theories)?

A

Semi-conservative:
Parent ♥︎♥︎
Daughter cells ♥︎♡ ♥︎♡

Conservative:
Parent ♥︎♥︎
Daughter cells ♥︎♥︎ ♡♡

Dispersive:
Parent ♥︎♥︎
Daughter cells ♥︎♡ ♡♥︎
♡♥︎ ♥︎♡

^each chromatid has a bit of both

♥︎=original strand
♡=new strand

18
Q

What does semi-conservative replication mean for future generations?

A

They will have genetic continuity.

19
Q

Who proved that Watson and Crick’s theory of semi-conservative replication was valid?

A

Meselson and Stahl

20
Q

Briefly outline Meselson and Stahl’s experiment

A

1.They had 2 DNA samples, one containing heavy nitrogen (HN) and one containing light nitrogen (LN)
2. Due to density, the LN settled further to the top in the tube, whereas the HN further to the bottom.
3. HN bacteria replicates in LN broth

Conservative: the LN and the HN were separate bands in the tube

Semi-conservative: the LN and HN had combined and formed one band in the middle.

Proves DNA replication is semi-conservative in bacteria.

21
Q

Name 5 useful properties of water

A

-Metabolite
-High latent heat of vaporisation
-Temperature buffer
-Good solvent
-Strong cohesion with other H2O molecules

22
Q

Explain why water is an important metabolite

A

Many metabolic reactions need water as they involve a condensation or a hydrolysis reaction- keeps our body functioning.

e.g amino acids are joined by polypeptides with need a compensation reaction.

23
Q

Why does water having a high latent heat of vaporisation mean its useful?

A

It takes a lot of heat energy to break the hydrogen bonds between water molecules, so a lot of heat is used up when it evaporates, so we cool down when we sweat.

24
Q

How does water act as a buffer for temperature changes?

A

Water has a high specific heat capacity so it takes a lot of energy to heat up or cool down, therefore no rapid temp changes.

Water is good for habitats for this reason.

25
Q

Why is water a good solvent?

A

Water is a polar molecule, so has some positive charge and some negative charge. Ions are able to dissolve as the water will be attracted to it and surround it, getting in-between bonds.

Useful as substances can dissolve and be transported around the body.

26
Q

How is water being cohesive good?

A

As it is polar, water sticks to each other and helps it flow, like in xylem tubes. It also means it has high surface tension when it comes into contact with air, why there are pond skaters.

27
Q

What does ATP stand for?

A

Adenosine triphospahte

28
Q

What is ATP used for and why?

A

-Used as an immediate store of energy that releases quickly
-In respiration, energy released from glucose is used to make ATP

29
Q

Explain the structure of ATP

A

-A nucleotide base Adenosine
-A ribose sugar
-3 phosphate groups, with the last having the most energy

30
Q

Describe the cycle of how ATP is released and made

A

-ATP is hydrolysed to release energy: the phosphate group on the end is ‘broken off’ and becomes ADP + P. Catalysed by the enzyme ATP hydolase.

-ATP is synthesised by a condensation reaction between ADP + P during respiration, catalysed by ATP synthase.

31
Q

Name and briefly describe 4 uses of ATP

A
  1. Metabolic process: energy to build large molecules
  2. Movement: energy for muscle contraction
  3. Active Transport: energy to change shape of carrier proteins in membrane.
  4. Activation of other molecules: phosphate released from ATP hydrolysis can be used to make other compounds more reactive.
32
Q

Name the protein associated with DNA in a chromosome

A

Histone

33
Q

What is the role of DNA polymerase in semi-conservative replication?

A

Joins the nucleotides by catalysing condensation reactions and catalyses the formation of phosphodiester bonds

34
Q

DNA polymerase can only bind to…

A

3’ due to the shape of the active site

35
Q

What process is ATP synthesised in?

A

Respiration/photosynthesis

36
Q

Give two ways ATP is a good energy store for cells

A

-Instant energy store
-Small amounts released, less heat energy lost

37
Q

Give two ways ATP is used in cells

A

-To provide energy for other reactions
-The phosphate makes other reactions more reactive

Biology🧬 (11 decks)

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