Topic 8-

Question 1

What do DNA and RNA stand for?

Answer 1

Deoxyribonucleic acid
Ribonucleic Acid

Question 2

What is the function of DNA?

Answer 2

Stores genetic information

Question 3

What is the function of RNA?

Answer 3

Copies and transfers genetic information from DNA to ribosomes

Question 4

What is DNA and RNA made out of?

Answer 4

Monomers called nucleotides

Question 5

What is a nucleotide made up of?

Answer 5

A pentose sugar- 5 Cs
A nitrogen-containing organic base
A phosphate group

Question 6

What are the components of DNA?

Answer 6

Deoxyribose
Nitrogen-containing base: Adenine, Guanine, Cytosine, Thymine
Phosphate group

Question 7

How do nucleotides join and what are the bonds called?

Answer 7

Condensation reactions
Between phosphate group of one nucleotide and sugar of another
Phosphodiester bonds

Question 8

What bases are pyrimidines and purines

Answer 8

pYrimidines- cYtosine and thYmine
purines- adenine and guanine

Question 9

How many strands does DNA have?

Answer 9

2
Run opposite to each other in anti-parallel twisting to form a double helix

Question 10

What holds the bases in each strand of DNA together?

Answer 10

Hydrogen bonding

Question 11

Complimentary base pairing

Answer 11

Adenine and Thymine
Guanine and Cytosine

Question 12

How many hydrogen bonds does adenine form with thymine?

Answer 12

2

Question 13

How many hydrogen bonds does cytosine form with guanine?

Answer 13

3

Question 14

How is DNA a stable molecule?

Answer 14

1) Stable molecule- many H bonds, covalent bonds (phosphodiester bonds) in sugar-phosphate backbone

Question 15

How is DNA a compact molecule?

Answer 15

Long- contain large amounts of coded information
Double helix- allows DNA to fit inside nucleus of cell

Question 16

How does the structure of DNA relate to its function?

Answer 16

Complementary base pairing- allows identical copies as DNA replicates itself due to the weak H bonds separating
Precise genetic code- sequence of bases controls protein synthesis
Stable- bonds
Compact- long + double helix (large amounts of coded information is stored)

Question 17

Structure of RNA

Answer 17

Ribose sugar
Phosphate group
Base- adenine, guanine, cytosine, uracil (THYMINE NOT PRESENT)

Question 18

Define semi-conservative replication

Answer 18

One strand is from the parental DNA
One has been synthesised from free-floating nucleotides

Question 19

Describe semi-conservative replication

Answer 19

1) DNA helicase unwinds DNA double helix by breaking H bonds holding complementary bases to form 2 single strands to act as a template
2) Free nucleotides join onto complementary bases via complementary base pairing via H bonds
3) DNA polymerase joins nucleotides together to form a new polynucleotide strand
4) Phosphodiester bonds form between the sugar + phosphate group to form a sugar-phosphate backbone

Question 20

Describe the structure of ATP

Answer 20

Adenine
Ribose
Three phosphate groups

Question 21

What is ATP?

Answer 21

An immediate source of energy for metabolic reactions

Question 22

How is ATP synthesised?

Answer 22

Condensation reactions
Between ADP and phosphate ion
ATP synthase
Requires an input of energy from a metabolic process

Question 23

How is ATP broken down?

Answer 23

Hydrolysis reaction
Between 2nd and 3rd phosphate group
ATP hydrolyse
Inorganic phosphate group is removed
Energy is released
ATP becomes ADP

Question 24

What are the 5 roles of ATP?

Answer 24

Active Transport
Exocytosis
Biosynthesis
Movement
Phosphorylation

Question 25

How is ATP used in active transport?

Answer 25

Energy is required for active transport as it moves substances across a concentration gradient Protein pumps are also ATP hydrolase enzymes = catalyse breakdown of ATP into ADP and Pi = release energy that is used to change shape of molecule

Question 26

How is ATP used in biosynthesis?

Answer 26

Energy is needed to make large molecules (polymers) from small molecules (monomers)

Question 27

How is ATP used in phosphorylation?

Answer 27

ATP can transfer its phosphate group to other molecules to make them more reactive (lower activation energy)

Question 28

How is ATP used in exocytosis?

Answer 28

Energy is required to make vesicles synthesised by the Golgi body

Question 29

How is ATP used in movement?

Answer 29

Energy is required for muscle contraction

Question 30

Why is ATP a more useful immediate energy source?

Answer 30

ATP can be quickly hydrolysed into ADP and Pi/ Breakdown of glucose is complex and requires many steps ATP is soluble = move around cell but cannot exit cell Breakdown of ATP releases a small amount of energy/ Glucose releases more energy than required which can go to waste

Question 31

How many pairs of chromosomes are in a human cell?

Answer 31

23 homologous pairs

Question 32

Define diploid

Answer 32

The total number of chromosomes in a normal body cell

Question 33

What are chromatids?

Answer 33

One of the two threads of a chromosome

Question 34

What are chromosomes?

Answer 34

Linear structures consisting of DNA wrapped around a histone protein

Question 35

How do chromatids become chromosomes?

Answer 35

Chromatids held together at the centromere (not visible) Chromosomes condense as DNA coils around histone proteins (visible)

Question 36

What are the stages of the cell cycle?

Answer 36

Interphase Prophase Metaphase Anaphase Telophase

Question 37

What are the 3 stages of interphase?

Answer 37

G1 S G2

Question 38

What happens during G1?

Answer 38

Cell prepares for DNA replication Protein synthesis Respiration

Question 39

What happens during S phase?

Answer 39

DNA/ Semi- conservative replication

Question 40

What happens during G2?

Answer 40

Checks DNA for errors (cell suicide)

Question 41

What happens during Prophase?

Answer 41

Chromatids condense as DNA wraps around histone proteins and become visible Nuclear membrane breaks down

Question 42

What happens during Prophase?

Answer 42

Nuclear membrane breaks down DNA is free in nucleus Chromosomes condense and become shorter Centrioles divide and move to opposite poles of the cell Spindle fibres form across the cell

Question 43

What happens during Metaphase?

Answer 43

Chromosomes move to the centre of the cell Centromeres attach to the spindle fibres

Question 44

What happens during Anaphase?

Answer 44

Spindle fibres contract separating sister chromatids to opposite poles of the cell

Question 45

What happens during Telophase and Cytokinesis?

Answer 45

Nuclear membrane forms around each group of chromosomes Chromosomes unwind and decondense (no longer visible) Cytoplasm splits to form two identical daughter cells

Question 46

Formula for mitotic index

Answer 46

(number of cells in mitosis/ total number of cells) x 100

Question 47

How do prokaryotic cells divide?

Answer 47

Binary fission

Question 48

Describe binary fission

Answer 48

Replication of circular DNA and plasmids Cell membrane grows between the two DNA loops Cytoplasm divides A new cell wall forms Forms two identical daughter cells

Question 49

Why don't viruses undergo cell division?

Answer 49

They are non-living

Question 50

How do viruses replicate?

Answer 50

Attach onto receptor site of host cell using attachment protein Inject nucleic acid into host cell Causes for production of viral components that are assembled into new viruses

Question 51

What is cancer?

Answer 51

Uncontrollable growth and division of cells

Question 52

Why isn't cancer detected?

Answer 52

Mutation of the p53 gene= no p53 protein made = p53 causes cell death = cell completes cell division

Question 53

What are the possible treatments for cancer?

Answer 53

Preventing DNA replication (using drugs) Preventing spindle fibre formation (disrupt mitosis)