biological molecules

Question 1

what is the composition of the cell

Answer 1

Water – 70%
Inorganic ions- 1%
Small organic molecules -3%
Macromolecules-26%

Question 2

what are the functions of carbohydrates?

Answer 2

energy storage, fuel, metabolite, and structural element

Question 3

what configuration does glucose have ?

Answer 3

d configuration - this is when the asymmetric C-atom most distant from the aldehyde/ketone group

Question 4

give examples of disaccharides

Answer 4

Maltose (alpha-glucose and alpha-glucose), Sucrose (α-D-glucose with β-D-fructose)
 and lactose ( β-D-galactose with α-D-glucose)

Question 5

give examples of polysaccharides

Answer 5

Starch, amylase (α-1-4 glycosidic bond), glycogen (α-1-4 glycosidic bond and-1-6 glycosidic bond), cellulose (β-1-4 glycosidic bond).

Question 6

which two polysaccharides are used for storage and why. are we able to break them down

Answer 6

starch and glycogen. we can break then down because the OH groups on the glycosidic bonds have the same orientation.

Question 7

why are we able to break some ps and not others?

Answer 7

due to the differences in the location of the glycosidic bond.

Question 8

explain the blood groups.

Answer 8

Group A : antibodies in plasma – Anti-B, antigens in red blood cell : A antigen
Group B: antibodies in plasma – Anti -A, antigens in red blood cell: Anti -A
Group AB : antibodies in plasma – none, antigens : A and B antigens.
Group 0 : antibodies : anti-A and anti-B, antigens: none.
o is the universal donor.

Question 9

how are proteins formed? and where and when does it happen

Answer 9

• Made of amino acids, form dipeptides/polypeptides in the ribosome during translation .
• Condensation reactions form peptide bonds, releasing water. The peptide bond is formed between the carboxylic acid of amino acid 1 and amine group of amino acid 3.

Question 10

what gives the polypetide chain structural orientation and polarity

Answer 10

the joining of the adjacent amino acids means the amino and carboxyl terminus gives a structural orientation and polarity to the polypeptide chain

Question 11

what are the functions of proteins

Answer 11

-Carrier functions (trafficking oxygen), metabolic functions (enzymes/energy)
-Cellular machinery (splicosomes/ribosomes), structural scaffold (microtubules, conveyor belts/nucleosomes, histoneDNA complex).
Sensing molecules (receptors and ligands)

Question 12

what denotes the variation between the amino acids and the overall protein

Answer 12

the R group

Question 13

what are the functions of amino acids ( including on their own)?

Answer 13

• building blocks for amino acid
• precursors to drugs/hormones such as: tyrosine-adrenaline (glycogenolysis; triggers glycogen breakdown in fight or flight) and histidine-histamine (vasodilator- an immune response to allergic reactions). .

Question 14

what kind of arrangement do amino acids have ?

Answer 14

tetrahedral except glycine which has two hydrogens. it has an assymetric arrangement.

Question 15

amino acids can form what in equilibrium, in a high ph and low ph? give an explanation ?

Answer 15

Can form zwitterion at neutral pH. the carboxyl and amine group readily ionises so the carboxyl group loses H+ and amine group gains H+. At low pH, AA acts as a base and accepts protons ( amine group gains a hydrogen and becomes +) , at high pH, acts as an acid and loses proton. ( carboxyl group donates a hydrogen and becomes – charged).

Question 16

In amino acids, where are the L and D isomers found.

Answer 16

L form more common as all amino acids incorporated into proteins by living organisms are in the L form.. D residues comprise bacterial cell walls and therapeutics.

Question 17

what conformation are R groups usually in? and which is more energetically favourable?

Answer 17

usually trans arrangement/conformation. Only 0.1% peptide has CIS so less energetically favourable.

Question 18

what is the difference between tertiary and quaternary structures?

Answer 18

intra-chain and inter-chain covalent bonds. Quaternary has cofactor enzymes. Tertiary is a combination of secondary secondary structures

Question 19

what does the loss of water in dna facilitate ?

Answer 19

sugar phosphate binding

Question 20

the loss of which molecule makes dna more stable than rna ?

Answer 20

the loss of oxygen in the sugar makes dna more stable.

Question 21

what are the functions of nucleotides >

Answer 21

Nucleotides not only act as building blocks for dna and rna , but they also have functions individually .

• Energy unit, eg ATP, where cleavage of the phosphate group adp produces energy .
• Second messenger , eg cAMP.
• Involved in RNA synthesis, eg AMP.

Question 22

what kind of bonds do lipids form ?

Answer 22

ester bonds

Question 23

why can cholesterol intercalate into the membrane?

Answer 23

1) OH group interact with the polar lipid heads.

2) Its steroid scaffold interavt with the fatty acids.

Question 24

what are the functions of cholesterol

Answer 24

1) Cholesterol intercalates into the membrane, making it less fluid and more flexible.
2) Oh group interaction with polar heads and steroid scaffold with fatty acids makes them closer together. This decreases permeability of soluable molecules.
- Cholesterol acts as a hormone building block for aldosterone, cortisol, testosterone and progesterone.

Question 25

list 3 single molecule diseases

Answer 25

• Insulin-dependant diabetes: absence of insulin failure to regulate blood glucose.
• Sickle Cell disease: One amino acid mutation in globin chain causes haemoglobin to aggregate into polymers, causing change in shape/less efficient.
• Cystic fibrosis: Absence of Cl transporting membrane protein leads to altered properties of secretions. E.g. Mucus.

Question 26

give 2 functions of body fats.

Answer 26

• The energy released from one molecule of fat > the energy released from one molecule of glucose so is used as food stores.
• Also lubrication between joints and insulation

Question 27

give three structure and protein relationships.

Answer 27

• Proteins that denature( loss of structure) or are mutated ( changed structure) affect function.
• Starch and glycogen are major energy sources for humans, whereas we cannot digest cellulose (different glucose polymer). This is due to the differences between the glycocidc bonds.
• Single oxygen difference makes DNA much more stable than RNA