Biological Molecules 1.5-1.8

Question 1

RNA Full Name

Answer 1

Ribonucleic acid

Question 2

DNA full name

Answer 2

Deoxyribonucleic acid

Question 3

What are nucleic acids

Answer 3

Polymers made from Nucleotides (2 types = DNA and RNA)

Question 4

What is DNA

Answer 4

− DeoxyriboNucleic Acid
− found in all organisms (animals, plants, microorganisms)
− carries genes
− genes = section of DNA that codes for a protein
− all organisms are built of proteins

Question 5

Nucleotide structure

Answer 5

A pentose sugar
A phosphate group
A nitrogen – containing organic base. These are cytosine, thymine, uracil, Adenine and guanine

The pentose sugar, phosphate group and organic base are joined as a result of condensation reactions, to form a single nucleotide

Question 6

Dinucleotide formation

Answer 6

Two mononucleotides may be joined as a result of a condensation reaction between the deoxyribose sugar of one mononucleotide and the phosphate group of another. The bond formed between them is called a phosphodiester bond
The new structure is called a dinucleotide

Question 7

Name all bases

Answer 7

Adenine
Guanine
Cytosine
Thymine
Uracil

Question 8

Ribonucleic acid structure

Answer 8

It is a polymer made up of nucleotides
It is a single, relatively short, polynucleotide chain in which the pentose sugar is always ribose and the organic bases are AUCG
One type of RNA transfers genetic information from DNA to the ribosomes. The ribosomes themselves are made up of proteins and another type of RNA
A third type of RNA is involved in protein synthesis

Question 9

DNA structure

Answer 9

The pentose sugar is deoxyribose and the organic bases are ATGC
DNA is made up of two strands of nucleotides (polynucleotides)
Each of the two strands is extremely long, and they are joined together by hydrogen bonds formed between certain bases
In a simplified form, DNA can be thought of as a ladder in which the phosphate and deoxyribose molecules alternate to form the uprights and the organic bases pair together to form the runs

Question 10

Base pairings

Answer 10

adenine always pairs with thymine
Guanine always pairs with cytosine
Complementary bases

Question 11

Stability of DNA

Answer 11

It’s a stable molecule because:
The phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
Hydrogen bonds link the organic base pairs forming bridges between the phosphodiester uprights. As there are three hydrogen bonds between C and G, the higher the proportion of C-G pairing is, the more stable the DNA molecule

Question 12

Function of DNA

Answer 12

DNA is the hereditary material responsible for passing genetic information from cell to cell and generation to generation
There is almost an infinite variety of sequences of bases along the length of the DNA molecule. It is this variety that provides genetic diversity within living organisms

Question 13

DNA molecule adaptations to carry out its functions

Answer 13

Very stable structure
It’s two separate strands are joint only with hydrogen bonds, which allows them separate during DNA replication and protein synthesis
It’s an extremely large molecule and therefore carries an immense amount of genetic information
By having the base pairs within the helical cylinder of the deoxyribose – phosphate backbone, the genetic information is to some extent protected from being corrupted by outside chemical and physical forces
Facepaints lead to DNA being able to replicate and to transfer information as mRNA

Question 14

DNAs double strand

Answer 14

Antiparallel

One strand runs 5‘ to 3‘ while the other runs 3‘ to 5‘

Question 15

What two main stages of the cell division occur in

Answer 15

Nuclear division

Cytokinesis

Question 16

Nuclear division

Answer 16

Process by which the nucleus divides

There are two types of nuclear division, mitosis and meiosis

Question 17

Cytokinesis

Answer 17

Follows nuclear division and is the process by which the whole cell divides

Question 18

Semiconservative replication requirements

Answer 18

The four types of nucleotides, each with the bases of AGC or T must be present
Both strands of the DNA molecules act as a template for the attachment of his nucleotides
The enzyme DNA polymerase and DNA helicase
A source of chemical energy is required to drive the process

Question 19

Semiconservative replication process

Answer 19

The enzyme DNA Helicase breaks the hydrogen bonds linking the base pairs of DNA
As a result the double helix separates into its two strands and unwinds
Each exposed polynucleotide strand then acts as a template to which complimentary free nucleotides bind by specific base pairings
Nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase to form the missing polynucleotide strands on each of the two original polynucleotide strands of DNA
Each of the new DNA molecules contains one of the original DNA strands, that is, half the original DNA has been saved and built into each of the new DNA molecules.

Question 20

The conservative model of dna replication

Answer 20

Suggests that the original dna molecule remains intact and that a separate daughter dna copy was built up from new molecules of deoxyribose, phosphate and organic bases
Of the two molecules produced, one would be made of entirely new while the other would be entirely original material

Question 21

Semi conservative model of dna replication

Answer 21

Proposes that the original dna molecule splits into two separate strands, each of which then replicated its mirror image
Each of the two new molecules would therefore have one strand of new material and one strand of original material

Question 22

Evidence for SCR

Answer 22

Replicating Bacterial DNA in 2 types of Nitrogen Isotopes, 15N and 14N
− 15N = heavy isotope
− 14N = light isotope
− Nitrogen found in nitrogenous bases of DNA
− Bacterial DNA made from 15N will have a Heavy Density
− Bacterial DNA made from 14N will have a Light Density
− Experiment = Bacterial DNA made of 15N is replicated in an environment of 14N – produces DNA molecules with half 15/half 14 (semi-conservative replication, original strand = 15N & new strand = 14N), therefore, DNA molecule has medium density

Question 23

ATP

Answer 23

Adenosine Triphosphate (Energy Carrier Molecule – delivers energy for life ​ processes)

Question 24

Structure of atp

Answer 24

− Adenosine Triphosphate

− made from 1 adenosine and 3 phosphates

Question 25

Synthesis of atp

Answer 25

-formation: ADP + Pi (+ energy used) = ATP +h2o
− condensation reaction using ATP Synthase
− carries energy in its bonds
− breakdown: ATP + h2o= ADP + Pi (+ energy released)
− hydrolysis reaction using ATP Hydrolase
− releases energy from its bonds

Question 26

What makes atp a good deliverer of energy

Answer 26

− immediate source = need to only break one bond (plus bond is weak)
− manageable source = releases small amount of energy

Question 27

Uses for atp

Answer 27

− protein synthesis
− organelle synthesis
− DNA replication
− cell division (mitosis)
− active transport
− metabolic reactions
− movement
− maintaining body temperature

Question 28

Role of water in biology

Answer 28

− found in living organisms = cytoplasm (all organisms), xylem/phloem (in plants), tissue fluid and blood (in animals)
− also acts as habitats for living organisms

Question 29

Properties of water

Answer 29

− Water Molecules (H20) are dipolar
− Hydrogen has slightly +ve charge and Oxygen has slightly -ve charge
− therefore H20 molecules can form hydrogen bonds with each other

Question 30

Latent heat of vaporisation

Answer 30

Hydrogen bonding between h2o molecules means that is required a lot of energy to evaporate 1g of water

Question 31

Cohesion and surface tension

Answer 31

Tendency of molecules to stick together

With H bonds, h2o large cohesive forces, these allow it to be pulled up e.g. xylem vessels

Question 32

Specific heat capacity water

Answer 32

H2O molecules stick together, takes more energy to separate them
Without hydrogen bonding water would be a gas
Takes more energy to heat a given mass of water

Question 33

Surface tension

Answer 33

Water molecules meet air they tend to be pulled back into body rather than escaping
Surface acts as a skin

Question 34

Features of water

Answer 34

Evaporation- cools and allows them to control their temp
Not easily compressed and therefore provides support
Transparent- aquatic plants can photosynthesise.

Question 35

Inorganic ions

Answer 35

Found in organisms

Solution in cytoplasm of cells and body fluids

Question 36

Inorganic ions functions

Answer 36

Iron ions- found in haemoglobin where they transport oxygen
Phosphate ions- form a structural role in dna and store energy in atp
Hydrogen ion- pH of solution and functioning of enzymes
Sodium ions- transport of glucose and amino acid across plasma membrane

Question 37

Eukaryotic vs prokaryotic dna

Answer 37

In eukaryotes, DNA is found mainly in the nucleus but there is also some in chloroplasts and mitochondria.
In prokaryotes, the DNA is not enclosed in a membranous envelope.

Question 38

Watson and Crick

Answer 38

In 1953, two scientists called Watson and Crick found that specific base pairing was involved in a way of copying sequences of genetic information.
They thought that each strand acts as a template from which the new complementary strand is copied.
But they didn’t know how replication took place.
They proposed three models of replication including conservative replication.

Question 39

Meselson and Stahl

Answer 39

Meselson and Stahl were interested in understanding how DNA replicates.
They grew E. coli for several generations in one medium containing a “heavy” isotope of nitrogen (15N) and another medium containing a ‘light’ isotope of nitrogen (14N).
During replication, the nitrogen gets included into nitrogenous bases, and eventually into the DNA.