T1: Nucleic Acids (DNA,RNA)

Question 1

function of DNA

Answer 1

holds genetic information

Question 2

function of RNA

Answer 2

transfers genetic information (from DNA –> ribosomes)

Question 3

function of ribosomes

Answer 3

made of DNA + proteins
read RNA in translation

Question 4

structure of DNA and RNA
similarities

Answer 4

both contain a phosphate group and a nitrogenous base

both contain a pentose sugar

both have A,C,G bases

both are polynucleotides

Question 5

DNA and RNA differences

Answer 5

DNA - deoxyribose sugar
RNA - ribose sugar

DNA has a thymine base that pairs with adenine, RNA has uracil

DNA - double helix structure with anti-parallel strands
RNA - short single chain

DNA replicates by semi-conservative replication

Question 6

formation of a polynucleotide

Answer 6

condensation reaction (releases h2o)
many nucleotides join at the phosphate group to create a polynucleotide and a phosphodiester bond

Question 7

describe the process of DNA replication

Answer 7

DNA helicase unzips the two strands
Both strands act as template strands
Free nucleotides attach by complementary base pairing (AT.CG)
DNA polymerase joins nucleotides on the new strand
Each new DNA molecule contains a template strand and a new strand (semi-conservative)

Question 8

describe the structure of DNA (5)

Answer 8

A polynucleotide
Each nucleotide is formed from deoxyribose sugar, phosphate group an nitrogenous base
Phosphodiester bonds between nucleotides
2 strands held together in a double helix shape with hydrogen bonds between CBP’s

Question 9

Give two features of DNA and explain how each one is useful in the semi-conservative replication of DNA

Answer 9

weak hydrogen bonds SO the two strands can be unzipped
complementary base pairing allows accurate replication

Question 10

describe the function of DNA helicase

Answer 10

unwinds DNA and breaks hydrogen bonds between bases

Question 11

describe the function of DNA polymerase

Answer 11

joins free nucleotides on the new strand forming phosphodiester bonds

Question 12

explain how the structure of DNA is related to its functions (6)

Answer 12

sugar phosphate backbone protects hydrogen bonds between bases

long molecule SO can store lots of information

helix shape SO compact

the base sequence codes for amino acids

weak hydrogen bonds for unzipping and replication

complementary base pairing SO identical copies can be made

Question 13

describe how the separation of DNA strands occurs

Answer 13

the enzyme DNA helicase binds and breaks the hydrogen bonds between complementary base pairs

Question 14

explain why the replication of DNA is described as semi conservative

Answer 14

each strand acts a template strand
the daughter DNA has 1 new strand and 1original strand

Question 15

function of ATP

Answer 15

energy carrying molecule produced during photosynthesis and respiration

releases energy when hydrolysed to ADP and inorganic phosphate (catalysed by ATP hydrolase)

Question 16

describe the structure of ATP

Answer 16

adenine
a ribose sugar
3 phosphate groups

Question 17

structure and function of ATP

Answer 17

ATP hydrolysis releases energy in small manageable amounts SO little energy is wasted when used in the cell

ATP can be rapidly synthesised after use SO a continual supply is available to the cell

ATP can transfer energy to the other molecules by phosphorylation SO it can make molecules more reactive

ATP cannot cross the cell surface membrane SO it ensures that it is always available inside the cell

Only one bond is broken to release energy during ATP hydrolysis to ADP SO immediate energy release

ATP is small and soluble so can easily diffuse through the cytoplasm and provide energy for different chemical reactions