macromolecules

Question 1

nucleic acids

Answer 1

large information-carrying
biomolecules that enable protein synthesis and determine inherited characteristics, e.g. DNA, RNA

Question 2

Nucleotides

Answer 2

building blocks of DNA and RNA
A nucleotide in simple terms equates to a nitrogenous base + pentose sugar + phosphate

Question 3

4 bases found in DNA

Answer 3

ATCG

Question 4

4 bases found in RNA

Answer 4

UTCG

Question 5

purines and pyrimidines

Answer 5

adenine and guanine
cytosine, thymine and uracil

Question 6

Nucleoside

Answer 6

base and a sugar without a phosphate group

Question 7

DNA

Answer 7

found by James Watson and Francis Crick in 1953
bases are found in the centre of the helix with the negatively charged sugar-phosphate backbone on the exterior
10 base pairs per turn

Question 8

characteristics of DNA

Answer 8

Double stranded: DNA has 2 strands.
Polarity: this arises due to the phosphodiester bond which offers directionality/ polarity of the molecule.
Complementary: the bases fit into each other in a particular combination with the help of hydrogen bonding. A pairs with T/U and G pairs with C.
Antiparallel/directionality: The 2 strands have the same chemical components but in opposite directions (5’ to 3’ direction).
Contains a deoxy-ribose sugar which has hydrogen instead of an ‘OH’ group at the
2’-position.

Question 9

RNA

Answer 9

single stranded molecule thus
does not adopt the helical structure of
DNA.
They can have helical structures in some regions where parts of the RNA chain complement each other.
bonds in these regions are
intramolecular hydrogen bonding which may result in hairpin and stem loop structures

Question 10

tRNA/mRNA

Answer 10

mRNA carries the information for protein synthesis and tRNA is an adapter molecule that carries a complementary codon to that on the mRNA in order to elongate a polypeptide chain

Question 11

Difference between DNA and RNA

Answer 11

1. Contains deoxyribose sugar Contains ribose sugar
2. Contains thymine
   Thymine is replaced with uracil
3. Right-handed double helix structure Single stranded (may form hairpin and
   stem loop structures)
   Localised in nucleus Localised in cytoplasm
4. Undergoes transcription Undergoes translation
5. Types include: nuclear DNA,
   mitochondrial DNA
   Types include: messenger RNA (mRNA), micro RNA (miRNA), tRNA, siRNA.
6. Can self-replicate
   N/A
   7.Copier enzyme is DNA polymerase
   Copier enzyme is RNA polymerase
7. Stable (long life)
   Less stable (short life)

Question 12

Chromosomes

Answer 12

structures that hold
an organism’s genes and are found in the nucleus of a cell. These structures are
composed of chromatids and chromatids are made of solenoids which are composed of nucleosomes.

Question 13

Nucleosomes

Answer 13

structures resulting from
DNA wrapping around histone proteins.
Humans have 23 pairs of chromosomes, 22 pairs of autosomes and a pair of sex chromosomes, therefore 46 in total

Question 14

Carbohydrates

Answer 14

carbon, hydrogen and oxygen atom
2 forms of carbohydrates: simple and complex
Simple carbohydrates: monosaccharides (sugars) like glucose, fructose.
Complex carbohydrates: potatoes, rice and pasta

Question 15

lactose

Answer 15

glucose + galactose

Question 16

sucrose

Answer 16

glucose + fructose

Question 17

maltose

Answer 17

2 glucose

Question 18

Glycogen

Answer 18

made of alpha-glucose linked with glycosidic bonds and main energy storage molecule in animals and humans whilst starch is a long linear polymer of alpha glucose and main energy storage molecule in plants

Question 19

test for starch

Answer 19

iodine test

Question 20

Transcription

Answer 20

first step of gene expression where DNA is copied into RNA, consists of initiation, elongation and termination

Question 21

Translation

Answer 21

protein synthesis that takes place on ribosomes

Question 22

Proteins

Answer 22

composed of amino acids, there are 20 different amino acids. Each amino acid consists of a chiral carbon atom linked with hydrogen, amino group, carboxyl group and a variable “R” group. These different groups provide amino acids with their special physical and chemical properties.
Amino acids form a peptide bond which is a covalent bond between the amino and carboxyl groups of 2 different amino acids.
Amino acids behave as zwitterions in aqueous solutions (dipolar ions) where they behave as both acids and bases (amphoteric).

Question 23

Globular proteins

Answer 23

enzymes, haemoglobin which have functional activities whilst fibrous proteins are structural proteins with high axial strength such as keratin, collagen, fibrin etc.

Question 24

Primary structure

Answer 24

Amino acids are linked by peptide bonds

Question 25

Secondary structure

Answer 25

carboxyl and amino groups of amino acids are highly
polar thus giving a C-N bond a slight double bond character allowing the formation
of hydrogen bonds. polypeptide chain folds into
certain structures such as alpha-helix and beta-sheets due to hydrogen bonding.
Collagen is a fibrous protein with a triple helix (intertwining of three polypeptide
chains)
Tertiary structure: secondary structures folding into three dimensional shapes
due to their side chains, where hydrophobic amino acids face interiorly and the
hydrophilic amino acids are placed on the exterior ensuring stability of a protein.
The non-covalent bonds involved in the tertiary structure of proteins include:
van der Waals, hydrogen bond etc. Heat or extreme pH lead to the denaturation of
protein which is a disruption of the secondary and tertiary structure of the protein
and this leads to a random coil configuration.
Quaternary structure: these are protein structures made of 2 more polypeptide
chains forming oligomers (few subunits), subunits may be the same (homomers) or
different (heteromers). For example, haemoglobin has two alpha-globin and 2 beta-
globin chains.

Question 26

Enzymes

Answer 26

proteins are involved in the catalysis of most
biological reactions, they are known to boost the rate of reaction. The reaction site
of certain enzymes binds substrates via non-covalent bonds such as van der Waals,
hydrogen bonding etc. Enzymes ensure specificity with some enzymes possibly
binding only one type of substrate in their active site

Question 27

protein functions

Answer 27

Transport: protein structures such as transferrin and haemoglobin transport oxygen and iron respectively. Lipoproteins in the blood carry dietary fats. Albumin is one of major protein carrier molecules in the blood, they bind to drugs, allergens etc.
Signalling: signalling molecules such as cytokines and hormones (insulin and growth hormone) are proteins, also protein structures such as receptors on the cell surface
bind
Structure and movement: collagen and fibrin are proteins that play a critical role in wound healing and hemostasias respectively. Myosin and actin are protein filaments which are integral to muscle movement.
Immunity: antibodies are proteins which can bind microbes (bacteria) and antigen.
Antigens are also proteins that can be self or non-self. Complements are also proteins
Regulation: transcription factors that assist in DNA transcription are also proteins.
Nutrition: proteins are also found in milk such as casein.