chapter 2 - nucleic acids Flashcards
1
Q
What does DNA do ?
A
- codes for the sequence amino acids in the primary structure of a proteins
- which determines the final 3D structure of a protein
2
Q
What are the monomers that make up DNA called ?
A
- nucleotides
3
Q
What are DNA nucleotides made up of
A
- a deoxyribose pentose sugar
- a nitrogenous base : A,T,C or G
- a phosphate group
4
Q
What are the 4 nitrogenous bases ?
A
- adenine, thymine, guanine and cytosine
5
Q
How are polynucleotides formed ?
A
- bonds forms between the phosphate group of one nucleotide and the deoxyribose sugar of another nucleotide
- by condensation reactions
- these forms phosphodiester bonds
6
Q
What properties do phosphodiester bonds that makes them suitable for holding nucleotides ?
A
- they are strong covalent bonds
- which ensure the genetic code doesn’t break down
- they help to hold the sugar phosphate backbone which is strong
7
Q
What holds DNA strands together ?
A
- hydrogen bonds
- which can only form between the complementary bases pairs
8
Q
How many hydrogen bonds form between the 2 complementary bases pairs ?
A
- 2 bonds between adenine and thymine
- 3 bonds between cytosine and guanine
9
Q
Why is the complementary base pairing in DNA important ?
A
- it helps maintain to maintain the genetic code when the DNA replicates
10
Q
How does the structure of DNA relate to its function ?
A
- sugar phosphate backbone and double helix = stable structure, protects bases
- double strand = one strand can used be as a template in replication
- weak hydrogen bonds = can easily be unzipped during replication
- large molecule = can carry a lot of info
- complementary bases paring = identical copies can be made and reduces copying errors which could lead to mutations
- double helix = molecules is compact
11
Q
What are purines an pyrimidines ?
A
- purines = larger bases with 2 carbon ring structures: adenine and guanine
- pyrimidines = smaller bases than have 1 carbons ring structures: thymine and cytosine
12
Q
What is RNA and what is its function ?
A
- a short polynucleotide made from RNA nucleotides
- used to copy and transfer genetic codes from DNA in the nucleus to ribosomes to make proteins
- can also be combines with proteins to make ribosomes
13
Q
What are RNA nucleotides made of
A
- a ribose pentose sugar
- a nitrogenous base : A,C,G or U
- a phosphate group
14
Q
What are the three types of RNA ?
A
- mRNA
- tRNA
- rRNA
15
Q
Describe mRNA
A
- messenger RNA
- a copy of one gene from the DNA
- leaves the nucleus to carry the genetic code to the ribosomes in the cytoplasm
16
Q
Describe tRNA
A
- transfer RNA
- folded in a clover leaf shape held by hydrogen bonds
- only found in cytoplasm
- its job is to transfer amino acids to the ribosome
- specific amino acids attach to specific tRNAA molecules
17
Q
Describe rRNA
A
- ribosomal RNA
- combines with proteins to make up most of the ribosomes
18
Q
What are the differences between DNA and RNA ?
A
For monomer differences :
- DNA has thymine whilst RNA has uracil
- DNA contains deoxyribose pentose sugar whilst RNA has ribose pentose sugar
For polymer differences :
- DNA is much larger with thousands of genes, RNA is shorter as its only one gene
- DNA is double stranded, RNA is single stranded
19
Q
What happens in semi conservative replication ?
A
- the DNA molecule produce will have one original parental strand and one newly synthesised daughter strand
20
Q
What 2 enzymes are involved in semi conservative replication ?
A
- DNA helicase
- DNA polymerase
21
Q
How does semi conservative DNA replication work
A
- DNA helicase breaks the hydrogen bonds between the complementary base pairs which separates the 2 strands
- each strand acts as a template to allow free nucleotides to attract to their complementary base pairs
- DNA polymerase joins (catalyses) adjacent nucleotides by condensation reactions in the 5’ to 3’ direction
- this forms phosphodiester bonds to make the sugar phosphate back bone of the daughter DNA strand
- 2 sets of daughter DNA are formed
- now there are two identical copies of DNA , each with one parental strand and one newly synthesised strand
22
Q
What makes up ATP ?
A
- adenine tripohosphate
- adenine = nitrogenous base
- ribose - pentose sugar
- 3 inorganic phosphate groups
23
Q
What is the function of ATP ?
A
- to act as an immediate source if energy for biological processes
24
Q
How does ATP release energy
A
- ATP is hydrolysed (water is added) to make ADP + Pi
- this releases energy
- uses ATP hydrolase enzyme
25
How is ATP created ?
- condensation reaction between Pi and ATP
- releases water
- requires energy
- happens during respiration
26
What is ATP used for in the body ?
- movement
- active transport
- synthesis of large molecules like DNA and proteins
- secretion of substances from cells
27
How do the properties of ATP make it good for its function ?
- hydrolysis of ATP releases small amounts of energy which mean less energy is wasted
- its small and soluble so can be transported outside of the cell
- only one bond hydrolysed in ATP ( only takes one step ), glucose has many bonds, so energy release is quick/immediate
- can transfer energy to other molecules through phosphorylation = when the inorganic phosphate binds to another molecule to make it more reactive
- ATP is rapidly re synthesised so ATP is always available
28
Why is water a dipolar molecule ?
- oxygen is more electronegative than hydrogen
- so the shared electrons are pulled towards the oxygen atom
- which gives oxygen a slight delta negative charge and hydrogen a slight delta positive charge
- so water has both positive and negative poles making it dipolar
29
How do water molecules form hydrogen bonds
- as in water oxygen is partially negative and hydrogen is partially positive
- the partially positive hydrogen on one water molecule can be attracted to the partially negative oxygen on another water molecule
- this is a hydrogen bond
30
What roles does water play in living organisms ?
It can act as :
- a solvent
- a temperature controller
- a cooling mechanism
- a habitat
- a metabolite
- a form of transport
31
How does water act as a solvent ?
- it can dissolve ionic compounds
- at the slightly negative oxygen are attracted to the positive ions adn the slightly positive hydrogens are attracted to the negative ions
- all the ion are surrounded by water so it dissolves
32
Why is water known as a universal solvent ?
- it dissolved more substances than any other liquid
- so can be uses to hold biological reactions
- and it can dissolve hydrophilic substances and transport them around the body
33
How does water act as a temperature control/buffer ?
- water has a high specific heat capacity
- meaning the hydrogen bonds can absorb a lot of energy before the bonds are broken , aka a lot f energy is needed to break the bonds and heat the water
- meaning water is resistant to rapid changes in termperature
- and as most organism are made of water , it allows he body to stay at a stable temperature
34
How does water act as a cooling mechanism ?
- water has a high latent heat of vaporisation
- so a lot of energy is needed to evaporate 1 gram of water and break the hydrogen bonds
- which means organisms can use evaporation of water as a cooling mechanism without losing to much water
- because when the water evaporated off the skin , it takes the heat energy away from the surface which cools the organism down.
35
How does water act as a habitat ?
- it has a high specific heat capacity and a high latent heat of vaporisation
- so does not change temperature or heat easily which provides a stale environment for organisms to live in
- at low temperatures the water freezes
- and in ice the water molecules are held farther apart which makes it less dense than water
- so ice will float and act as insulating layer on ponds and lakes
- meaning the water below the lakes doesn’t freeze and the organism within the water can move and survive
36
How does water act as a metabolite ?
- uses in hydrolysis reaction
- condensation reactions
- and photosynthesise where it is used as a raw material
37
How does water act as a transport medium ?
- the tendency of water molecules sticking together by hydrogen bonds is cohesion
- water molecules also have the tendency to stick to other materials and this is adhesion
- the strong cohesion dad adhesion of water helps it to low through organisms and I carried substances along with it
- also when water molecules meet air they create a high surface tension
- this creates a skin like structure on the surface of water which I strong enough to support small organisms
