Chapter 2: Nucleic Acids Flashcards

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1
Q

What are nucleic acids?

A

Nucleic acids are a group of important molecules, most commonly DNA and RNA. They are information carrying molecules.

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2
Q

What are ribosomes made from and where are they found?

A

Ribosomes are molecules made from RNA and proteins which transfer information from DNA to ribosomes.

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3
Q

What are the 3 components of a nucleotide?

A

1) A pentose sugar
2) A phosphate group
3) A nitrogen-containing organic base

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4
Q

What is the reaction which forms nucleotides?

A

Condensation reaction

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5
Q

What is the bond which forms between two nucleotides joined to each other?

A

Phosphodiester bond

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6
Q

What are the 4 DNA organic bases? Why do they pair together?

A

Adenine Thymine Cytosine Guanine The base pairs are complementary

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7
Q

What are the 4 RNA organic bases?

A

Adenine Guanine Cytosine Uracil

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8
Q

Describe the structure of DNA:

A
  • Two DNA strands curled in a double helix formation. - Sugar and phosphate form a ‘sugar-phosphate backbone’. - Opposite bases are joined by hydrogen bonds.
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9
Q

Who worked out the structure of DNA?

A

James Watson Francis Crick (Following the work of Rosalind Franklin)

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10
Q

What is the function of DNA and where is it found?

A

DNA is a hereditary material which is responsible for passing genetic information between cells and generations.

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11
Q

How is DNA adapted to carry out its function?

A
  • Very stable structure
  • 2 seperate strands joined by hydrogen bonds (so they can separate during replication)
  • Extremely large molecule
  • Base pairs ‘protected’ by helica cylinder
  • Base pairing makes DNA replicatin and transfer of information easier and more efficient
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12
Q

Define nuclear division:

A

The process by which he nucleus divides. This includes mitosis and meiossis.

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13
Q

Define cytokinesis:

A

The process following nuclear division in which the whole cell divides.

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14
Q

What is semi-conservative DNA replication?

A

Repliation of a double stranded molecule of nucleic acid, separating into single strands which serve as a replicaion template for the formation of another complementary strand onto each original strand.

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15
Q

What are the four requirements for semi-conservative replication?

A
  • Four types of nucleotide (A,T,C,G)
  • Both strands of the DNA molecule act as a template
  • The enzyme DNA polymerase
  • A source of chemical energy
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16
Q

Outline the process of semi-conservative replication:

A

1) The enzme DNA helicase breaks hydrogen bonds between base pairs
2) Double helix separates
3) Each exposed polynuleotide strand acts as a template for the complementary nucleotide
4) The enzyme DNA polymerase joins nucleotides together in a condensation reaction.
5) Each new DNA molecule contains one new and one old strand.

It is called semi-conservative replication as only half of the original DNA has ben saved.

17
Q

What is ATP?

A

A phosphorylated macromolecule which is the main energy source in both animal and plant cells.

18
Q

What are the three parts of an ATP moleule?

A
  • Adenine: Nitrogen containing organic base
  • Ribose: A sugar moleule with a pentose sugar which acts as a backbone
  • Phosphates: A chain of three phosphate groups
19
Q

What is the equation for the release of energy via the hydrolysis of ATP?

A

ATP + (H2O) —–> ADP + Pi + (energy)

20
Q

What features of ATP make it a suitable source of energy for living organisms?

A
  • It has a low activation energy so is easily broken down
  • It is unstable so is easily broken down
  • It releases energy in small, manageable amounts
  • It releases energy in a single, simple reaction
  • It is an immediate energy source (isn’t stored)
  • It is soluble so can be used in cells
21
Q

What reacton takes place to break down ATP?

A

Hyrolysis catalysed by ATP hydrolase

22
Q

What reaction takes place to synthesise ATP?

A

Condensation with the enzyme ATP synthase

23
Q

Where does ATP synthesis occur?

A
  • In chlorophyll-containing plant cells durng photosynthesis (phosphorylation)
  • In plant and animal cells during respiration (oxidative phosphorylation)
  • In plant and animal cells during the transfer of phosphate groups between cells (substrate-level phosphorylation)
24
Q

Name and describe 5 energy-requiring processes where ATP is used:

A

1) Metabolic processes: building of marcromolecules
2) Movement: energy for muscle contraction (i.e. filaments sliding across each other)
3) Active transport: energy changes shape of carrier protiens and allows molecules to move against concentration gradient
4) Secretion: ATP forms lysosomes which secrete cell products
5) Activation of molecules: Pi can phosphorylate other compounds and lower their activation energy. Pi is released during the hydrolysis of ATP

25
Q

What is water?

A

Water is a major component of cells, a metabolite and a solvent for many metabolic reactions

26
Q

Why is water described as dipolar?

A

Oxygen has a slight negative charge while hydrogen has a slight positive charge

27
Q

How do different water molecules bond to each other?

A

The positive pole of one binds to the negative pole of another forming a hydrogen bond. It is a fairly weak bond but appears srong when there are many of them

28
Q

Describe the specific heat capacity of water:

A

The SHC of water is relatively high since the water molecules stick together. This means it takes a lot of energy to raise the temperature of it. This is due to the hydrogn bonds.

Water, therefore, acts as a buffer against suden temperature change in an aquatic habitat and inside organisms

29
Q

Describe the latent heat of vaporisation of water:

A

The LHV of water is also relatively large as lots of energy is required to evaporate a gram of water. This means that mammals can sweat to provide a cooling effect without the issue of evaporation.

30
Q

Define cohesion:

A

The tedency of molecules to stick to one another (e.g. water)

31
Q

Why is water so cohesive?

A

Many hydrogen bonds

32
Q

Give an example of the cohesion of water:

A

Xylem vessels

33
Q

Define surface tension:

A

A force on the surfae film of a quid caused by the attraction of the particles

34
Q

Give an example of a use for the high surface tension of water:

A

Habitat fo small organisms such as pond skaters

35
Q

Why is water important to livng organisms?

A

It is the main constituent of all organisms

36
Q

How is water used in reactions (metabolism)

A
  • It is used in molecule break down and building (hydrolysis and condensation)
  • Many chemicl reactions take place in it
  • It is a raw material for photosynthesis
37
Q

Give 2 examples of water as a solvent:

A

1) Removal of waste products such as ammonia and urea
2) Gases such as oxygen and carbon dioxide dissolve in water

38
Q

Why is water useful in photosynthesis (other than being a raw material)?

A

It is transparent so aquatic plants can photosynthesise in it

39
Q

Inorganic ions ocur in a range of concentrations in a water-based solution. Give 5 examples of functions of inorganic ions:

A

Iron ions in haemoglobin- oxygen transportation

Phosphate ions- structural role in DNA molecules and store energy in ATP

Hydrogen ions- pH

Sodium ions- co transport

Sodium and potassium ions- action potential (nerve impulse)