biological molecules

What are DNA and RNA types of?

Nucleic acids

What are nucleic acids made of?

Nucleotides

What are DNA and RNA nucleotides made of?

• Pentose sugar - deoxyribose or ribose

• Phosphate group

• Nitrogen containing base

How are nucleotides joined together?

• joined by phosphodiester bonds

• in condensation reactions

What groups do the phosphodiester bonds form between?

The deoxyribose sugar of one nucleotide and the phosphate group of another

What is the structure of a DNA molecule?

double helix

What is the structure of a RNA molecule?

Single helix/relatively short polynucleotide chain

Which bonds form between DNA bases?

Hydrogen

How many H bonds form between C and G?

3

How many H bonds form between A and T?

2

What is the chain of nucleotides, not including bases, called in a DNA molecule?

Phosphodiester backbone

what are the two polynucleotide strands of DNA described as?

Anti Parallel

Which carbons do phosphodiester bonds form between?

3 and 5

Which way is a strand with a phosphate group at the end bonded?

3 prime to 5 prime

Which way is a strand with an OH molecule on the end bonded?

5 prime to 3 prime

How does DNA replicate?

Semi conservatively

What were the other two theories for DNA replication?

Conservative, dispersive

What kind of bases are A and G?

Purine

What kind of bases are C, T and U?

Pyramidine

describe the process of DNA replication

• DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide strands

• helix unwinds to form two strands

• free nucleotides diffuse and bind to complementary exposed bases via hydrogen bonds when they happen to hit them by chance

• the sugar-phosphate backbones of the new nucleotides are joined together by DNA polymerase to form 2 new DNA molecules

• each DNA molecule is one old strand and one new strand

which direction does DNA polymerase work in?

• moves down the template strand 3’ to 5’, new strand formed is 5’ to 3’

• this is because the active site is only complementary to the 3’ end of the newly forming DNA strand

what experiment was done to prove that DNA replicates semi-conservatively?

• the most beautiful experiment in biology

• two samples of bacteria were grown on different types of nitrogen broth - 14N and 15N (light and heavy)

• this nitrogen became a part of the bacteria’s DNA

• a sample of DNA was taken from each batch of bacteria, and spun in a centrifuge tube - 14N DNA was lower than 15 N

• bacteria containing heavy nitrogen were taken out and put in a broth containing light nitrogen

• they were left for one replication of DNA and then spun in a centrifuge, then left and spun again

describe the results of the experiment that showed DNA replicated semi conservatively

• first spin: DNA will settle in one block in between where the 14N and 15N had settled previously

• 2nd spin: half of the DNA will settle in the same place, the other half will settle higher up

describe the results of the experiment IF DNA replicated conservatively

• first spin: the DNA would be in 2 distinct sections, one 14N and higher, the other 15N and lower

• 2nd spin: 75% of the DNA would be high up where the 14N was, and 25% would be low down where the 50% was

describe the results of the experiment if DNA replicated dispersively

• 1st spin: all DNA in the middle of where the 14N and 15N DNA had settled previously

• 2nd spin: all the DNA in between where the 14N and 15N had been, but skewed upwards (less 15N)

what does ATP stand for?

adenosine triphosphate

what does ADP and AMP stand for?

• ADP - adenosine diphosphate

• AMP - adenosine monophosphate

what is ATP made up of?

• ribose

• adenine

• three phosphate groups (ADP has 2, AMP 1)

how is energy released from ATP?

• ATP is hydrolysed

• this forms ADP and a phosphate molecule

• this requires the presence of water

which enzyme catalyses the process of energy release by ATP?

ATP hydrolase

how does the hydrolysis of ATP release energy?

• bonds between phosphate molecules are very unstable and have a low activation energy

• one of these bonds is broken, which is a quick process and releases a lot of energy

what can the phosphate group produced from ATP hydrolysis be used for?

• phosphorylation of other compounds

• this makes them more reactive

which process occurs to form ATP?

condensation of ADP and inorganic phosphate

when does condensation of ADP and inorganic phosphate occur?

during photosynthesis and respiration

which enzyme catalyses condensation of ADP?

ATP synthase

write an equation for hydrolysis of ATP

ATP + H2O → ADP + Pi

write an equation for condensation of ADP

ADP + Pi → ATP + H2O

why is ATP useful?

• it is an immediate source of energy and can be broken down in a single step

• releases a small, manageable quantity of energy

• doesn’t require a lot of space/need to be stored as it can be formed easily - recyclable

• phosphorylation

• small and soluble - easy to store

what properties does water have?

• polar

• metabolite

• solvent

• high specific heat capacity

• high latent heat capacity

• strong cohesion and adhesion

• strong surface tension

• different density in ice than water

why is water polar?

• it has an uneven distribution of charge within the molecule

• this gives the oxygen ends slightly negative charges and the hydrogen atoms slightly positive charges

why is water being polar beneficial?

• means it has hydrogen bonds

• this enables pretty much all of its other properties

why does water act as a solvent?

• is polar

• helps ions to dissociate in water as charges on molecule attract charged ions

• means it is a solvent

why is the property of water being a solvent important?

• allows for transport of dissolved substances around the body

• either in xylem/phloem/blood

why is the property of water being a metabolite important?

• metabolite = allows chemical reactions take place

• means it allows reactions such as condensation and hydrolysis to take place

why does water have strong surface tension?

• hydrogen bonds on the surface of the water make it very cohesive

• this means it has strong surface tension

why is water having a strong surface tension important?

• allows sweat to form droplets, which evaporate from the skin

• allows pond skaters to move on surface of water

• allows water droplets to form on leaves

why does water have a high specific heat capacity and what does it mean?

• it means a lot of energy is required to raise the temperature of water by 1K

• this is because of the collectively strong hydrogen bonds between molecules which require a lot of energy to overcome

why is water having a high specific heat capacity beneficial?

• can act as a buffer solution in cells/tissues

• helps to maintain a constant internal temperature

• also makes water a good habitat for aquatic organisms

why does water have strong cohesion/adhesion and what does this mean?

• cohesion is attraction between molecules of the same type, adhesion is of different types

• hydrogen bonds that form between molecules make this possible

why is water having strong cohesion beneficial?

• helps water to flow, making it good for transporting substances

• means water can move up columns like the xylem

why does water have a high latent heat of vaporisation and what does this mean?

• lots of energy is required to change the state of the water

• this is because of the many hydrogen bonds it contains

why is water having a high latent heat of vaporisation beneficial?

• means that lots of energy can be lost through sweating, but without using too much water

• means that it helps with temperature regulation

what are 4 types of inorganic ions?

• hydrogen ions

• iron ions

• sodium ions

• phosphate ion

what are the functions of hydrogen ions?

• concentration impacts levels of enzyme activity

• pH changes alters H+ ion concentration and so ionic bonding in tertiary structure

• this changes the shape of the active site

what are the functions of iron ions?

• found in haemoglobin and myoglobin

• these are proteins which allow molecules to hold and transport oxygen

• incorporated in some enzymes

• circulated in blood

what are the functions of sodium ions?

• required for cotransport of glucose and amino acids across membranes

• helps to regulate blood pressure and volume

• contributes to maintenance of turgidity

what are the functions of phosphate ions?

• used in essential molecules (ATP, ADP, RNA, DNA, NADP, phospholipids, phosphorylated sugars)

• part of main inorganic component of human bone (calcium phosphate)