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Biology A1 & A2 > 1B: More Biological molecules > Flashcards

1B: More Biological molecules Flashcards

1
Q

What are nucleic acids needed for?

A

It is needed to make proteins, which in turn make all other molecules.

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2
Q

What is a nucleic acid?

A

A nucleic acid is a complex organic substance present in living cells, especially DNA or RNA, whose molecules consist of many nucleotides linked in a long chain.

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3
Q

What are nucleic acids composed of?

A

Long chains of smaller molecules called nucleotides

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4
Q

What are nucleotides composed of? (3)

A

-A pentose sugar (5 carbon atoms)
- A phosphate group
And…
- One of 5 possible nitrogenous bases:
Adenine, Cytosine, Guanine and Uracil (only in RNA) or
Thymine (only in DNA)

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5
Q

Describe the nucleotide structure

A
  • The pentose sugar, phosphate group + organic base all form bonds through condensation reactions.
  • Two (mono)nucleotides bond together into a dinucleotide and many bond to form a polynucleotide.
  • The bond between them is a phosphodiester bond
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6
Q

What is the bond between dinucleotides/ polynucleotides called?

A

A phosphodiester bond

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7
Q

What does RNA stand for?

A

Ribonucleic Acid

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8
Q

Describe RNA

A
  • A relatively short single stranded polynucleotide chain
  • The pentose sugar is ALWAYS Ribose
  • Bases: Adenine, Uracil, Guanine, cytosine
  • 3 forms: mRNA, rRNA, tRNA
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9
Q

What are the 3 forms of RNA called?

A
  • Transfer/ tRNA
  • Messenger/ mRNA
  • Ribosomal/ rRNA
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10
Q

What does DNA stand for?

A

Deoxyribonucleic Acid

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11
Q

Describe DNA

A
  • A double helix with two extremely long polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.
  • The pentose sugar is ALWAYS Deoxyribose
  • Bases: Adenine, Guanine, Cytosine, Thymine
  • Two strands of DNA are bonded together by H bonds between complementary pairs
  • Phosphodiester backbone (relatively unreactive) protects the more reactive bases
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12
Q

What are the complementary bases in DNA? acronym?

A

Adenine + Thymine
Guanine + Cytosine
Take Action, Go Crazy!

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13
Q

What structure do the two strands in DNA form?

A

A double helix structure

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14
Q

What is ‘phosphodiester backbone’ the same as?

A

Phosphodiester backbone = Sugar Phosphate backbone

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15
Q

Compare DNA and RNA

A 
DNA:
- More stable because of double helix with unreactive phosphodiester backbone 
- One of its bases is Thymine 
- Pentose sugar is Deoxyribose 
RNA:
- Less stable because its single strand leaves its (reactive) bases unprotected
- One of its bases is Uracil
- Pentose sugar is Ribose
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16
Q

What does a condensation reaction between two nucleotides form?

A

Forms a phosphodiester bond

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17
Q

What did the simplicity of DNA lead scientists to doubt?

A

The relative simplicity of DNA led many scientists to doubt that it carried the genetic code.

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18
Q

What does semi-conservative DNA replication ensure?

A

The semi-conservative replication of DNA ensures genetic continuity between generations of cells

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19
Q

What is the process of (semi-conservative) DNA replication? (6 stages)

A
  1. Enzyme DNA helicase breaks hydrogen bonds linking complementary base pairs
  2. Double helix separates into 2 strands + unwinds
  3. Each polynucleotide chain acts as a template to which free nucleotides attach by complementary base pairing
  4. Nucleotides attach by a condensation reaction, catalysed by the enzyme DNA polymerase, forming phosphodiester bonds
  5. This forms the missing strand on each polynucleotide chain
  6. Produces two identical DNA molecules, each containing one strand of the original DNA, hence “semi-conservative”
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20
Q

What did Watson and Crick discover in 1953 about DNA? how were they helped?

A

In 1953, Watson and Crick discovered the structure of DNA with the aid of Rosalind Franklin’s X-Ray diffraction studies.

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21
Q

Draw ATP

A 
Phosphate 
(adenine) !
                 !
                 Pentose ---P---P---P 
                 (ribose)
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22
Q

What does ATP consist of?

A
  • Adenine- nitrogenous
  • Ribose- pentose sugar (backbone)
  • Phosphates- chain of 3 phosphate groups
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23
Q

What happens to ATP after it is produced in the mitochondria?

A

It diffuses out to the rest of the cell to power other cellular processes.

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24
Q

What does ATP stand for?

A

Adenosine triphosphate

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25
Q

What is ATP a derivative of?

A

ATP is a nucleotide derivative

26
Q

What is the equation for the hydrolysis of ATP?

A

ATP + H2O —> ADP + Pi + E

27
Q

What does ADP stand for? Why is it called this?

A

Adenosine Diphosphate -because one of the phosphates has been broken off
TRI (3) —> DI (2)

28
Q

Where is the energy in ATP stored? how is it released?

A
  • The available energy in the molecule is stored in the bonds between the phosphate groups. These bonds are unstable and so have a low activation energy.
  • When they are broken (through hydrolysis) they release a substantial amount of energy
  • Normally just the end (1) phosphate is removed
29
Q

What can the hydrolysis of ATP be ‘coupled’ to? What does this mean?

A

What can the hydrolysis of ATP be ‘coupled’ to energy-requiring reactions (endothermic) in the cell
- Means that instead of the energy being lost as heat it can power another reaction

30
Q

What can the inorganic phosphate (Pi) released during hydrolysis of ATP be used for?

A

The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, often making them more reactive.

31
Q

When and how is ATP resynthesised?

A

ATP is resynthesised by the condensation of ADP and Pi.

This reaction is catalysed by the enzyme ATP synthase during photosynthesis or during respiration.

32
Q

Which enzyme catalyses the hydrolysis of ATP?

A

ATP hydrolase

33
Q

Which enzyme catalyses the synthesis of ADP and ATP?

A

ATP synthase

34
Q

Where is ATP synthesised?

A

In the mitochondria and chloroplasts

35
Q

Compare ATP to glucose.

A

ATP:
- Releases less energy
- Energy is released in smaller more manageable quantities
- The hydrolysis of ATP to ADP is a single reaction that releases immediate energy
Glucose:
- Releases more energy
- E is released in larger less manageable quantities
- The breakdown of glucose is a long series of reactions + therefore energy takes longer

36
Q

Why is ATP continuously made (in the mitochondria/ chloroplasts)?

A

Because ATP cannot be stored and it is an immediate source of energy

37
Q

How is ATP used in metabolic processes?

A

ATP provides the energy needed to build up macromolecules from their basic units. E.g Making starch from glucose / polypeptides from amino acids.

38
Q

How is ATP used in movement?

A
  • ATP provides the energy for muscle contraction.
    In muscle contraction, ATP provides the energy for the filaments of muscle to slide past one another and therefore shorten the overall length of muscle fibre.
39
Q

How is ATP used in active transport?

A
  • ATP provides the energy to change the shape of carrier proteins in plasma membranes.
    This allows molecules/ ions to move against the conc. gradient.
40
Q

How is ATP used in secretion?

A

ATP is needed to form the lysosomes necessary for the secretion of cell products

41
Q

How is ATP used in the activation of molecules?

Give example

A

The Pi released in the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, thus lowering the activation energy in enzyme catalysed reactions.
E.g the addition of phosphate to glucose molecules at the start of glycolysis.

42
Q

Water is a major component of cells. What % of a cell’s mass does it make up?

A

On average water makes up 70% of a cells mass

43
Q

In what 2 type of reactions is water a metabolite?

A

It is a metabolite in many metabolic reactions e.g. condensation and hydrolysis reactions

44
Q

Why is water an important solvent?

A

It is an important solvent in which metabolic reactions occur

45
Q

Why is water a polar molecule?

A

Because of their bent shape

46
Q

Why are water molecules ‘sticky’ and why is water a good environment for life?

A

They can form (up to 4) hydrogen bonds with each other:

  • Because of this water requires more energy to boil that would be expected
  • Water has a high specific heat capacity
  • This acts as a buffer against rapid temp changes = making aqueous environments relatively stable (perfect for life)
47
Q

Give an example of how water is an excellent substance for cooling.

A

Sweating!

- The high latent heat required to evaporate water allows it to be an excellent substance for cooling off by sweating.

48
Q

How does water have strong cohesion?

A

Water has strong cohesion between molecules (h bonds); this supports columns of water in xylem and phloem of plants and produces surface tension where water meets air.

49
Q

What is the most amount of (hydrogen) bonds one water molecule can form?

A

Up to 4

50
Q

Water is a dipolar molecule, explain this.

A

This means that water molecules have charges at both ends. E.g + hydrogen side and the - oxygen

51
Q

Which part of a phospholipid lacks charge? Which part has a charge?

What does this mean?

A

The fatty acid tails are not charged - hydrophobic
The phosphate heads are charged, they ‘drive’ the molecule

This means that phospholipids are polar molecules.

52
Q

Where in organisms are inorganic molecules found?

A

Inorganic ions occur in solution in the cytoplasm and body fluids of organisms, some in high concentrations and others in very low concentrations.

53
Q

Each type of ion has a specific ___, depending on its _____.

A

Each type of ion has a specific role, depending on its properties.

54
Q

What is the endosymbiotic theory?

A

The theory that the mitochondria are actually unicellular organisms that live inside the cells of eukaryotes. The mitochondria even have their own membrane and DNA!

55
Q

Which inorganic ion is in haemoglobin?

A

Iron (Fe2+)

56
Q

What is the role of iron ions as a component of

haemoglobin?

A

The Fe+ part of the haemoglobin that bonds to the oxygen

- When the O is bound the ion temporarily becomes Fe 3+

57
Q

What is the role of hydrogen ions (H+) in pH?

A

H+ ions are sometimes concentrated to facilitate certain enzyme reactions

58
Q

What is the pH scale?

How is it calculated?

A

The pH scale is the measure of how acidic/ basic a substance is.

It is calculated by the conc. of H+ or OH- ions present

59
Q

What is the role of sodium (Na+) ions in the co-transport of glucose and amino acids?

A

Large molecules e.g glucose and amino acids, need to be transported across cell membranes

Na+ ions can travel through relatively easily and can take the larger molecules with them - called cotransport

60
Q

What is the role of phosphate ions as components of DNA and of ATP?

A

Whenever a phosphate ion is attached to a molecule it is called a phosphate group.

DNA, RNA and ATP contain phosphate groups

Biology A1 & A2 (19 decks)

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