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Biology > 8a. Nucleic Acids > Flashcards

8a. Nucleic Acids Flashcards

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1
Q

What does DNA stand for

A

Deoxyribonucleic acid

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2
Q

What does RNA stand for

A

Ribonucleic acid

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3
Q

What are DNA and RNA

A

Important information-carrying molceules
Nucelic acids
Found in the nucleus and in the presenc of phosphate groups.
DNA ia the molecule that stores genetic info and RNA transfers it to ribosomes
Both made of nucleotides monomers

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4
Q

What is a nucelotide made form

A

A pentose sugar
A nitro-organic base
A phosphate group

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5
Q

How do nucleotides form polynucleotides

A

The phosphate group is linked to to the sugar on the next nucleotide by strong covalent Phosphodiester bonds
Creates the sugar-phosphate backbone
Condensation reaction

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6
Q

What is a DNA nucleotide made up of

A

-Deoxyribose sugar
-N-Containing base: Adenine, Guanine, Cytosine or Thymine
-A phosphate group

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7
Q

What are the catogrories of DNA bases

A

Purines ( Adenine and Guanine)
Pyrimidines ( Thymine and Cytosine)

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8
Q

Are purines or pyrimidines longer

A

Purines a bigger than pyrimidines

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9
Q

What is the sturcture of DNA

A

2 Polynucleotide chains
One running the opposite way to the other
Twist to form a double helix
Bases are held together by H bonding

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10
Q

What is the term to discribe the pairing of bases

A

Complementary base pairing

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11
Q

How many H bonds do each bases form in DNA

A

Aenine forms 2 with Thymine
Cytosine forms 3 with Guanine

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12
Q

How does the structure of DNA relate to its function

A

-Stable molecule as its double helix with many H bonds
-Strong due to sugar-phosphate backbone
-Complementary base pairing allows DNA to replicate exactly
-Compact. Long so contain large amounts of coded information. Double helix allows it to fit in cell
-Precise genetic code determined by sequence of bases which control protein synthesis

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13
Q

How many different amino acids are there in proteins

A

20

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14
Q

What does RNA do

A

Transfers DNA from nucleus to cytoplasm.
Sections of DNA that code for polypeptides are copied onto a single standed molecule - RNA

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15
Q

What is the structure of RNA

A

Relativley short, usually single stranded polynucleotides

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16
Q

What is an RNA nucleotide made up of

A

-Ribose sugar
-N-containing organic base: Adenine, Guanine, Cytosine or Uracil
-A phosphate group

17
Q

What type of base is uracil

A

Pyrimidle

18
Q

What happens in semi-conservative replication

A

-DNA Helicase unwinds the DNA double helix by breaking weak H bonds between bases. This separates the strands
-Each exposed strand now acts as a template
-New DNA nucleotides from the nucleus are attracted to exposed bases and attach by complementary base pairing
-New H bonds form between bases
-DNA polymerase joins the adjacent nucleotides together by forming phosphodiester bonds via condenstation reactions

19
Q

Where does the name semi-conservative come from

A

Hlaf of the orginional DNA molecule is conserved in each new molecule

20
Q

What evidence is there for semi-conservative replication

A

In an experiment using E.Coli grown in a medium containing a heavy isotope.
Culture was then transffered to a medium containing normal light isotope
After time, samples taken and DNA extracted and centrifuged
With each successive generation the proportion of hybrid DNA halves and all the remaining DNA is ‘light’.

21
Q

What does ATP stand for

A

Adenosine triphosphate

22
Q

What is ATP

A

The immediate source of energy used by cells to drive their metabolic reactions

23
Q

What does an ATP molcules consist of

A

They are derived from nucleotides.
-Ribose sugar
-Organic base Adenine
-3 Phosphate groups (ions)

24
Q

How is ATP Synthesised

A

By the addition of ADP to an inorganic phosphate
Condensation reaction catalysed by ATP Synthase.
Addition of a phosphate molecule is Phosphorylation
Requires an input of energy from a metabolic process and occurs during respiration (or photosynthesis)

25
Q

Where is energy stored in an ATP molecule and how is ATP broken down

A

In the Phosphate-Phosphate bond between 2nd and 3rd phosphate
Covalent link is unstable and easily broken by ATP Hydrolase in a hydrolysis reaction
Inorganic phosphate group is removed, energy released
ATP becomes ADP

26
Q

What is the role of ATP

A

Large number of roles in the metabolism of the cell
Energy released when hydrolysed is used for active processes

27
Q

How is ATP used in Active transport

A

Required to move substances against a conc gradient using carrier proteins
Protein pumps are also ATP hydrolase enzymes
They catalyse the splitting of ATP to ADP and Pi
Use the energy to change shape and pump the molecule

28
Q

How does exocytosis require ATP

A

To make vesicles which are synthesised by the Golgi body and package large molecules prior to secretion
Energy also required for reverse process (endocytosis)

29
Q

How is ATP needed for the synthesis of substances (biosynthesis)

A

Required to make large molecules from smaller ones (monomers to polymers)

30
Q

How is ATP needed for movement

A

Energy required for muscle contraction

31
Q

How is ATP needed for activation of other molecules

A

ATP can transfer its phosphate group to other molecules, phosphorylating them and making them more reactive

32
Q

Whats ATP like as a source of energy

A

-Not a good long term energy store due to the instability of its phosphate bonds
-Cells can maintain only a few seconds supply
-Good immediate energy source, ATP is rapidly reformed from ADP and Pi.
Reaction is reversible

33
Q

What is the ATP Cycle

A

ATP – Hydrolysis –> ADP+Pi (+ energy released for use in cells)
ADP + Pi –Condensation (+energy input) –> ATP

34
Q

Why is ATP more useful than glucose as an immediate energy source

A

-Breakdown of ATP to ADP is a single reaction, energy is immediatley avaliable.
Breakdown of glucose is complex several stage reaction
-ATP is soluble and easily moved around in cells but cant pass through membranes
-Breakdown of ATP released a small amount of energy
Breakdown of glucose release more energy than is required - inefficient as lots of energy would be wasted as heat

Biology (23 decks)

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