Bio > 2. Nucleic Acids > Flashcards

2. Nucleic Acids Flashcards

(42 cards)

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1
Q

What are the 2 types of nucleic acid?

A
  • RiboNucleic Acid (RNA)
  • DeoxyriboNucleic Acid (DNA)
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2
Q

What are the monomers of DNA/RNA?

A

Nucleotides

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3
Q

What makes up a nucleotide?

A
  • A pentose sugar (5 carbon)
  • Phosphate group
  • Nitrogen-containing organic base (Adenine, Thymine, Cytosine, Guanine, Uracil)
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4
Q

How are the components of a nucleotide formed into a nucleotide?

A

Condensation reactions

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5
Q

Where on the nucleotide do bonds form to connect them together?
What is the bond called?

A

Between the deoxyribose sugar and the phosphate group
A phosphodiester bond

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6
Q

Describe the physical structure of RNA:
What is the pentose sugar called?
What organic bases are found in RNA?

A

Single, relatively short polynucleotide chain
Ribose
Adenine, Guanine, Cytosine, Uracil

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7
Q

Describe the physical structure of DNA:

A

Made up of 2 strands of polynucleotides, both are extremely long, and are joined together by hydrogen bonds between certain bases

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8
Q

How do the bases on the 2 strands of DNA attach to each other?

A

By hydrogen bonds

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9
Q

What are the base pairings?

A

Adenine - Thymine
Cytosine - Guanine

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10
Q

Which part of the nucleotide acts as the backbone in the double helix?

A

The phosphate and deoxyribose sugar

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11
Q

Why is DNA a stable molecule? (2)

A
  • The phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
  • Hydrogen bonds form between the bases, 3 between C and G, and 2 between A and T. Therefore the more C-G pairs, the stronger the molecule
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12
Q

How is DNA adapted to carry out its function of holding genetic information? (5)

A
  • Stable structure which rarely mutates
  • 2 separate strands that are joined only by hydrogen bonds, meaning they can separate during DNA replication and protein synthesis
  • Extremely large molecule so can carry a lot of genetic information
  • By having the deoxyribose-phosphate backbone on the outside, the genetic information held in the bases are protected from being corrupted
  • Base pairing leads to DNA being able to replicate and to transfer information as mRNA
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13
Q

How are the 2 strands of DNA arranged?

A

Antiparallel to each other (run in opposite directions)
From 5’ -> 3’ and 3’ -> 5’

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14
Q

What ‘ carbons does the phosphodiester bonds connect to?

A

The 5’ and 3’ carbons

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15
Q

What are connected to the 5’ and 3’ carbons?

A

5’ carbon connects to the phosphate group
3’ carbon connects to a hydroxyl group

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16
Q

What are the 2 main stages of cell division?

A
  • Nuclear division
  • Cytokinesis
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17
Q

What is nuclear division?
What are the types of nuclear division? (2)

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A

The process by which the nucleus divides.
Mitosis and meiosis

18
Q

What is the process of DNA replication called?

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A

Semi-conservative replication

19
Q

What are the 4 requirements for semi-conservative replication to take place?

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A
  • The four types of nucleotide (ATCG) must be present
  • Both strands of the DNA molecule act as a template for the attachment of these nucleotides
  • DNA polymerase must be present
  • A source of chemical energy to drive the process
20
Q

What is the process of semi-conservative replication? (5)

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A
  • DNA helicase breaks the hydrogen bonds between the base pairs
  • This causes the double helix to unwind and separate into 2 strands
  • Each exposed polynucleotide strand then acts as a template to which complementary free nucleotides bind by specific base pairings
  • Nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase to form the missing polynucleotide strand on each of the 2 original polynucleotide strands
  • Each of the new DNA molecules contain one of the original DNA strands and a copy of the original opposite strand
21
Q

What is the importance of the 3’ and 5’ carbons in the reformation of a DNA strand?

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A

DNA polymerase can only add nucleotides to the 3’ carbon so the new strands are made 5’ to 3’

22
Q

What is the evidence for semi-conservative replication? (4)

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A
  • Meselsohn and Stahl
  • Used bacteria grown on a medium of 14N (light) and 15N (heavy). They transferred a bacteria grown on 15N to a 14N environment and allowed it to replicate once.
  • They then centrifuged the bacteria in a special solution to extract the DNA and separate it out into different types
    The lighter the DNA, the nearer the top of the centrifuge it collected.
  • They found that bacteria grown on the heavier 15N were further down the centrifuge, and the 14N bacteria were near the top
  • They found that the bacteria that had been allowed to replicate on the 14N environment were in the middle, showing that one strand was 15N and the other newer strand was 14N, so the older strand binds to a new strand
23
Q

What are the components of ATP?

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A
  • Adenine
  • Ribose
  • Phosphates
24
Q

How does ATP store energy?

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A

The bonds between the ribose sugar and the 3 phosphates are unstable so have a low activation energy
When they are broken, they release a considerable amount of energy

25
What is formed after ATP is hydrolysed?
ADP + Pi
26
Which phosphate usually only gets removed during the hydrolysis of ATP?
The terminal (furthest one from the ribose) phosphate
27
What enzyme catalyses the hydrolysis of ATP?
ATP hydrolase
28
What enzyme catalyses the reformation of ATP from ADP?
ATP synthase
29
What reaction reforms the ATP molecule from ADP + Pi?
Condensation reaction
30
In what ways does the synthesis of ATP from ADP + Pi occur? (3)
- In chlorophyll-containing plant cells during photosynthesis (photophosphorylation) - In plant and animal cells during respiration (oxidative phosphorylation) - In plant and animal cells when phosphate groups are transferred from donor molecules to ADP (substrate-level phosphorylation)
31
Why is ATP not a suitable long-term energy source? How much ATP is stored? What are some good long-term energy stores?
Due to the instability of its phosphate bonds Only a few seconds' worth Fats, and carbohydrates such as glycogen
32
How is ATP a better immediate energy source than glucose? (2)
- Each ATP molecule releases less energy than each glucose molecule, making it more manageable to use in reactions - The hydrolysis of ATP to ADP is a single reaction that releases immediate energy. The breakdown of glucose is a long series of reactions and therefore the energy release takes longer
33
Name 5 energy-requiring processes that use ATP:
- Metabolic processes e.g. making starch from glucose - Movement (muscle contraction) - Active transport (changes the shape of carrier proteins in plasma membranes so molecules/ions can be moved against a concentration gradient) - Secretion (forming lysosomes to secrete cell products) - Activation of molecules (Pi produced can be used to make other compounds more reactive) e.g. addition of phosphate to glucose molecule in glycolysis
34
What are the 5 properties of water?
- Dipolar - Hydrogen bonding - Specific heat capacity - Latent heat of vaporisation - Cohesion
35
How is water dipolar?
The oxygen atom has a slight negative charge, and the hydrogen atoms have a slight positive charge
36
How can water form hydrogen bonds?
As the positive pole of one molecule will attract the negative pole of another and vice versa. Many hydrogen bonds can form, giving water its unusual properties
37
Why does water have a high specific heat capacity of water? Why is this important? (2)
- As lots of hydrogen bonds form between water molecules, the boiling point is high. - This means that water acts as a buffer against sudden temperature variations in organisms and in the environment
38
Why does water have a high latent heat of vaporisation? Why is this important? (2)
- The presence of hydrogen bonds between molecules means it takes a lot of energy to evaporate 1 gram of water. - This means it is effective in dissipating heat (e.g. sweating), as it takes a lot of energy to do so
39
Why does water cause cohesion?
The hydrogen bonds mean water has large cohesive forces, so can be pulled up through a tube e.g. xylem vessel
40
Why is water important to living organisms?
It is the main constituent of all organisms (around 65% in mammals)
41
Why is water important in metabolism? (3)
- It is used to break down many complex molecules by hydrolysis - Chemical reactions take place in an aqueous medium - Water is a major raw material in photosynthesis
42
Why is water important as a solvent? (4)
It readily dissolves other substances such as: - Oxygen and carbon dioxide - Wastes such as ammonia and urea - Inorganic ions and small hydrophilic molecules such as amino acids, monosaccharides and ATP - Enzymes
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