Molecular Biology

Question 1

importance of carbon

Answer 1

• the most important element to life
• basic building block that can be used to make a wide range of different molecules
• forms covalent compounds

Question 2

importance of hydrogen

Answer 2

• forms part of water
• forms hydrogen bonds, which gives water many of its properties
• bonds to carbon to form hydrocarbons

Question 3

importance of nitrogen

Answer 3

• aids in digestion and growth

- necessary for foetus development

Question 4

importance of Sulfur

Answer 4

• makes up some amino acids
• protects cells from environmental hazards (e.g. pollution, radiation)
• helps liver to function properly
• important in forming blood clots
• keeps skin supple and elastic

Question 5

importance of calcium

Answer 5

• bone and teeth formation
• muscle growth
• electrical impulses in the brain
• aids in blood clotting
• helps maintain blood pressure

Question 6

importance of iron

Answer 6

• component of haemoglobin
• aids in tendon and ligament formation
• needed to maintain a healthy immune system

Question 7

importance of sodium

Answer 7

• needed for nerve impulses to be sent
• important part of blood plasma
• maintains the proper amount of water in our blood

Question 8

importance of phosphorus

Answer 8

• found in membrane structures
• needed for healthy formation of bones and teeth
• central part of energy storage system
• aids in cell growth and repair

Question 9

characteristics of water

Answer 9

polar molecule due to oxygen-hydrogen dipole

Question 10

thermal properties of water

Answer 10

• high specific heat capacity
• high latent heat of vaporisation
• high boiling point but can evaporate below boiling point
• bc of the strong hydrogen bonds
• this makes water an effective coolant

Question 11

cohesive properties of water

Answer 11

• water molecules stick to each other

- due to hydrogen bonds forming between them

Question 12

solvent properties of water

Answer 12

• many substances can dissolve in water

- due to water’s polarity

Question 13

organic compounds

Answer 13

based on carbon and can be found in living things

e.g. lipids, proteins, carbohydrates

Question 14

inorganic compounds

Answer 14

anything that isn’t organic

Question 15

properties of amino acids

Answer 15

• monomers that combine to form polypeptides, which in turn form proteins
• they are all soluble and have the same structure (except the R group)

Question 16

carbohydrates

Answer 16

• monosaccharides
• disaccharides
• polysaccharides

Question 17

monosaccharide

Answer 17

• carbohydrates with relatively small molecules
• soluble in water
• taste sweet

Question 18

significance of glucose

Answer 18

• all cells use glucose to respire

- building block for a lot of larger molecules

Question 19

ribose

Answer 19

• a pentose (5-carbon sugar)

- deoxyribose is a modified version, used in DNA as the sugar phosphate backbone

Question 20

fatty acids

Answer 20

• the basis of triglycerides and many other lipids
• the basis of phospholipids
• hydrophobic

Question 21

structural characteristics of fatty acids

Answer 21

• mostly made up of 16-18 C atoms but can be anywhere from 14-22
• the carboxyl end (you can tell by the C=O double bond) is hydrophilic
• forms spheres called micelles in water (imagine a round phospholipid bilayer, sans proteins and double tail)

Question 22

examples of monosaccharides

Answer 22

• glucose
• galactose
• fructose

Question 23

examples of disaccharides

Answer 23

• lactose: glucose + galactose
• sucrose: glucose + glucose
• maltose: glucose + fructose

Question 24

examples of polysaccharides

Answer 24

• glycogen
• cellulose
• starch

Question 25

most common elements in biological organisms

Answer 25

• carbon
• hydrogen
• oxygen

Question 26

triglycerides

Answer 26

simple lipids

e.g. fats, oils

Question 27

functions of lipids

Answer 27

• energy store: lipids transfer twice as much energy as carbohydrates
• metabolic water source: when fats are used in respiration, both energy and water are released
• thermal insulation
• buoyancy: fat isn’t as dense as muscle/bone
• electrical insulation: lipids form myelin sheaths around nerve cells
• hormone: steroids can act as hormones
• cell receptors: glycolipids’ role in phospholipid bilayer
• structure: e.g. phospholipid bilayer

Question 28

DNA nucleotide components

Answer 28

• pentose sugar (ribose for RNA, deoxyribose for DNA)
• phosphate
• nitrogen base

Question 29

types of nitrogen bases

Answer 29

• cytosine (C)
• guanine (G)
• adenine (A)
• thymine (T)
• uracil (U)

Question 30

DNA structure:

Answer 30

• 2 anti-parallel polynucleotide chains
• double helix spiral structure
• held together by hydrogen bonds
• sugar-phosphate backbone
• complementary base pairing: A to T, G to C
• base order: G C T A

Question 31

DNA replication process

Answer 31

catalyst: DNA polymerase
1. DNA double helix unwinds, catalysed by helicase, which causes breaking of hydrogen bonds between the base pairs (the structure is called a replication fork)
2. free nucleotides begin to attach to their complementary base pairs on the parent strands, which are still anti-parallel
3. the hydrogen bonds reform, and the sugar and phosphate on the free nucleotides condense to form the backbone on the new DNA molecules

Question 32

significance of complementary base pairing

Answer 32

• makes sure the new DNA strands are perfect copies of the original
• the complete genome would be successfully copied, ensuring all genes remain intact
• opposite pairs are attracted, and the structure allows DNA polymerase to check for mistakes

Question 33

explain the semi-conservative nature of DNA replication

Answer 33

• one of the strands always come from the parent chromosome
• the other strand is newly synthesised during replication from free nucleotides
• so half the original molecule is always conserved

Question 34

RNA structure

Answer 34

• relatively short compared to DNA
• base order: G C U A
• complimentary base pairing: A to T, U to C
• made up of a single strand that can form mRNA, tRNA, or rRNA

Question 35

DNA transcription process

Answer 35

catalyst: RNA polymerase
1. the DNA double helix is unwound by DNA helicase, breaking the hydrogen bonds
2. the DNA opens at the transcription site, and free nucleotides pair with DNA nucleotides. the main difference is that U replaces T, so it’s A to T, U to C instead
3. RNA polymerase forms phosphodiester bonds to make the backbone of the mRNA molecule
4. the mRNA detaches and leaves the nucleus via nuclear pores in the membrane, and enters the cytoplasm to travel to the ribosome

Question 36

transcription site

Answer 36

position of gene that needs to be copied

Question 37

sense strand

Answer 37

• coding strand

- template for the mRNA

Question 38

anti-sense strand

Answer 38

• where the mRNA is built on

- has same pattern as sense strand due to complimentary base pairing

Question 39

codon

Answer 39

• each sequence of 3 bases provides a code for one amino acid
• also called triplet code
• some codons are start/stop codons denoting where to begin/end the sequence

Question 40

translation process

Answer 40

active process using ATP

1. amino acids are activated by combining with tRNA in cytoplasm
2. each tRNA binds to the anticodon and to the amino acid (this binding is catalysed)
3. once the mRNA molecule is transcribed, it’s sent to the ribosome for translation
4. the ribosomes move along the mRNA to “read” the code, beginning at the start codon
5. the tRNA molecules, with their amino acids, find their complimentary codon on the mRNA chain
6. the tRNA separates from the amino acid and the mRNA and goes back to find more amino acids
7. the process continues until a stop codon is reached and the polypeptide chain is released

Question 41

anticodon

Answer 41

the complimentary codon for the mRNA