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A-LEVEL BIO > Nucleic acids > Flashcards

Nucleic acids Flashcards

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1
Q

Structure of nucleotide

A
  • pentose sugar (5 carbons), a phosphate group and a nitrogen containing organic base.
  • joined together by condensation reaction
  • bases either A,T,C,G OR U
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2
Q

Describe the structure of RNA

A
  • single stranded, relatively short polymer of nucleotides joined by phosphodiester bonds.
  • pentose sugar is always a ribose sugar
  • bases = G,C, A, U
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3
Q

Describe DNA structure

A
  • polymer of nucleotides joined by phosphodiester bonds
  • pentose sugar is deoxyribose
  • organic bases = A,T,G ,C
    -Made up of 2 strands of nucleotides (polynucleotides). Each of the 2 strands is very long and are joined together by H bonds formed between bases
    -double strand twists into a double helix
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4
Q

Describe the events which take place during DNA replication.

A

1.Strands separate / H-bonds break
2.DNA helicase (involved)
3.Each strand acts as ) template
4.Free nucleotides attach;
5. Complementary base pairing
6.DNA polymerase joins nucleotides
7.H-bonds reform
8. Semi-conservative replication

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5
Q

name the type of reaction that joins two nucleotides together.

A

condensation reaction

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6
Q

state the location of the new chemical bond that is formed when two nucleotides are joined together.

A

between the phosphate group of one nucleotide and the sugar of another

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7
Q

name the bond formed when two nucleotides are joined together.

A

phosphodiester bond

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8
Q

the chain for sugar and phosphates in a polynucleotide is collectively known as what?

A

sugar-phosphate backbone

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9
Q

what is the advantage of DNA being a helix shape?

A

DNA is a very long molecule, the helix shape (twisting) allows a lot of genetic information to be stored in a small space - nucleus

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10
Q

the two polynucleotide strands in a DNA molecule are antiparallel. what does this mean?

A

they run in opposite directions.

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11
Q

if in a section of DNA, 33% of the bases were A, what % of the bases are T? explain your answer

A

33% are T because number of A is equal to the number of T

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12
Q

if in a section of DNA 33% of the bases were A, what % of the bases are G?

A

A=T, so 33+33 = 66% of base are A&T. 100-66=34. so 34% of the bases are G and C. so %G = 34/2 = 17%

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13
Q

what is the role of DNA helicase in DNA replication?

A

breaks the hydrogen bonds between bases causing the strands to separate.

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14
Q

what happens once the DNA double helix has separated into two separate strands?

A

each strand acts as a template strand. free floating DNA nucleotides match up using complementary base pairing.

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15
Q

What is the role of DNA polymerase?

A

to catalyse the joining together of adjacent nucleotides on the new strand by condensation reactions, resulting in the formation of a phosphodiester bond.

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16
Q

why is DNA polymerase only complementary to the 3’ end of a DNA strand?

A

DNA polymerase is an enzyme. enzymes are specific to one substrate. DNA polymerase has an active site with a specific shape that is only complementary in shape to the 3’ end of a DNA strand.

17
Q

Events that take place during DNA replication

A

-unwinding of DNA’s double helix structure through DNA helices breaking H bonds between base pairs
-free nucleotides bind to complementary bases
-DNA polymerase builds the polynucleotide by forming phosphodiester bonds by a condensation reaction

18
Q

Describe the formation of a new polynucleotide strand.

A

A new polynucleotide strand is formed when DNA polymerase forms phosphodiester bonds between the phosphate on one nucleotide and the sugar on another

19
Q

How is DNA adapted to carry out it’s functions

A

-Stable due to many H bonds between bases and these being protected by sugar phosphate backbone
-H bonds between strands > easy to seperate from replication molecule
- large molecule > carry huge amount of info
-base pairing > DNA can transfer information as RNA

20
Q

Describe complementary base pairing

A
  • Adenine always pairs with thymine
  • Guanine always pairs with cytosine
  • H bonds between the bases
  • 3 H bonds between C and G/2 H bonds between A and T
21
Q

Explain semi-conservative process of DNA replication

A

-DNA helices breaks H bonds between base pairs, causing double helix structure to unwind
-free nucleotides bind to complementary bases on the exposed polynucleotide
-DNA polymerase builds up the polynucleotide by forming phosphodiester bonds (condensation reaction)
-2 new polynucleotide chains are formed. Each strand has half the original genetic material

22
Q

Explain the semi conservative process of DNA replication.

A

DNA replication is semi conservative because each of the new strands contains one of the original strands

23
Q

Explain why the process of DNA replication is described as semi-conservative

A

replicated DNA has 1 original strand and 1 new strand

24
Q

If and inhibitor of DNA polymerase were introduced into a cell, explain what the effect would be on DNA replication

A

-regardless on type of inhibitor, enzyme substrate complex wouldn’t form
-so condensation reaction needed to bind nucleotides together wouldn’t occur
-so DNA replication wouldn’t happen

25
Q

Define what energy is
and why organisms need
it

A
  • Energy is the ability to do work.
  • Organisms need energy to live - to carry out metabolic processes, move, maintain temperature etc.
  • The energy in organisms originally comes from the sun and is converted to organic molecules by photosynthetic organisms
26
Q

Explain how ATP stores
energy

A
  • ATP is a nucleotide + consists of an adenine base, ribose sugar and 3 phosphate molecules
  • bonds between phosphate groups are unstable > low a.e. so when they’re broken they release energy
  • ATP hydrolase catalyses the removal of the terminal phosphate group for ADP by hydrolysis
27
Q

Describe how ATP is synthesised

A
  • ATP synthase catalyses the reaction to add an inorganic phosphate group to ADP to produce ATP
  • condensation reaction
28
Q

Describe the role of ATP
in biological processes.

A

ATP is an immediate energy source, that cannot be stored in large quantities, it is formed when required mainly in mitochondria. ATP is required for:
- metabolic processes > builds macromolecules from their basic units
- movement > muscle contraction > provide energy for filaments of muscle to slide past one another > shorten overall length of muscle fibre
- active transport > change shape of carrier proteins in plasma membranes >molecules could be moved against a conc gradient
- secretion > from lysosomes necessary for secretion of cells
- activation of molecules >phosphorylate other compounds to make them more reactive

29
Q

ATP formula

A

ATP + H20 > ADP + Pi + E

30
Q

Describe the structure of water

A
  • Water consists of two atoms of hydrogen and one of oxygen.
  • It is dipolar - no overall charge but oxygen is slightly negative and hydrogen slightly positive (the charge is unevenly distributed)
31
Q

State the properties of water

A
  • H bonds > negative pole of one molecule is attracted to the positive pole of another
  • high specific heat capacity > due to hydrogen bonding more energy is required to heat water. Water acts as a buffer against sudden temperature variations
  • latent heat of vaporisation > due to hydrogen bonding it takes a lot of energy to evaporate water. effective means of cooling as body heat i8s used to evaporate water
  • cohesion > due to hydrogen bonding water molecules stick together.
    surface tension, water surface acts like skin and is strong enough to to support small organisms
32
Q

Explain the importance of the
water molecule to living
organisms.

A

Metabolism - hydrolysis and condensation reactions/ reactions take
place in an aqueous medium/ raw material for photosynthesis
Solvent - water dissolves other substances eg gases oxygen, carbon
dioxide/ waste eg ammonia and urea/ inorganic ions and small
hydrophilic molecules eg amino acids, monosaccharides, ATP/enzyme
reactions take place in solution)

Other – evaporation cools organisms/ provides support as not easily
compressed/transparent so aquatic plants can photosynthesise

33
Q

Describe inorganic ions and their roles.

A

-An inorganic ion is a charged atom that does not contain carbon
Roles:
Iron ions - Haemoglobin, oxygen transport
Phosphate ions - DNA, structural. ATP, energy store.
Hydrogen ions - pH and therefore enzyme function.
Sodium ions - glucose and amino acid transport across membranes. Nerve impulses

A-LEVEL BIO (20 decks)

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