Biomolecules

Question 1

Biomolecules

Answer 1

Carbohydrates
Lipids
Nucleic acid
Proteins

Question 2

Carbohydrates

Answer 2

CnH2nOn (found in pasta, bread, rice, potatoes …)
- Monomer: Monosaccharide,
disaccharides
- Glycosidic bond
- Condensation reaction: (dehydration)
/ hydrolysis
- Carbohydrates/polysaccharides are not sweet, non crystallized, not water soluble because of their size.

Question 3

Monomers of carbohydrates

Answer 3

• Monosaccharides and disaccharides (sugars) are sweet, crystalline and water soluble.
• Equilibrium between the open and the cyclic form.
• Functional groups: many alcohol and 1 aldehyde or ketone.
• Contain chiral carbons (all monosaccharides in nature are D-type)
• Glucose (aldohexose) and fructose (ketoheptose) are monosaccharides.
• Disaccharides are made of two monosaccharides. F.Ex. Sucrose.

Question 4

Condensation reaction of carbohydrates (Exam)

Answer 4

Glucose+Fructose → Sucrose
Dehydration reaction because a molecule of water H2O is released.

The reverse reaction is called Hydrolysis.

Question 5

Two types of carbohydrates

Answer 5

Structural function (β-glycosidic bonds) : cellulose, in plants, human body does not contain enzymes able to metabolize the b glycosidic bonds.
• Energy storage function: Glycogen (α-glycosidic bonds). Glycogen is usually stored in liver and muscle cells. Whenever blood glucose levels decrease, glycogen is broken down via hydrolysis to release glucose monomers that cells can absorb and use.

Question 6

Lipids

Answer 6

• C, H, O and sometimes P (found in oils, butter…)
• Not polymers because there are no monomers.
• Almost no polar bonds.
• Hydrophobic/lipophilic
  Four types:
  1. Fatty acids
  2. Triglycerides (Fat)
  3. Phospholipids
  4. Steroids

Question 7

Main biological functions of lipids

Answer 7

• Long time energy storage*
• Signaling
• Insolation
• Structural components of cell membranes*
• Building blocks for hormones*

Question 8

Fatty acids

Answer 8

- Tail: Hydrocarbon chain (hydrophobic) 
   \+ Head: carboxylic acid (hydrophilic)
Types:
=> Saturated: No double bonds, 
     stearic acid. Pack tightly, Butter.
=> Cis-unsaturated: naturally 
     happening. Cannot pack tightly due 
     to bent double bond. Liquid, oil. 
=> Trans-unsaturated (industry), pack 
     tightly, likely to be solid. Margarine.

Question 9

Triglycerides

Answer 9

• Glycerol + 3 fatty acids
• Bond formed is an ester (condensation
  reaction (dehydration) / hydrolysis)

Question 10

Phospholipids

Answer 10

- Glycerol + 2 fatty acids + phosphate 
  group + modifier
- Building blocks of biological 
  membranes.
- Phospholipid bilayer.

Question 11

Steroids

Answer 11

• Structure of 4 fused rings.
• Cholesterol (structural component of
  cell membranes + precursor
  biosynthesis hormones, bile acid and
  vitamin D)
• Signaling hormones (cortisol).

Question 12

Nucleic acid

Answer 12

DNA (deoxyribose) and RNA (ribose)
- C, H, N, O and P (found in every food 
  coming from a living organism)
- Monomer: Nucleotides
- Phosphodiester bond
- If carbon #2 on the sugar has a H its 
  deoxyribose, if it has OH its ribose.

Question 13

Nucleotides

Answer 13

Contain:
- A (cyclic) pentose sugar: Deoxyribose
for DNA and Ribose for RNA
- A nitrogenous base in C1 of the sugar: Adenine-Thymine (DNA) or Uracil (RNA)
Guanine-Cytosine
With - a hydrogen bond.
- Between 1 and 3 phosphate group(s) in C5 of the sugar.

Question 14

Phosphodiester bond

Answer 14

The bond connecting monomers.
=> between the OH- on the C3 of the
sugar and the phosphate group of
another nucleotide.

Question 15

DNA and RNA

Answer 15

- Strands of DNA and RNA have a 
  directionality.
- The sequence of nitrogenous bases 
  are read from the 5' end (phosphate 
  group) to the 3' end (OH).
- DNA is double strand, with the 
  strands antiparallel.

Question 16

Proteins

Answer 16

Proteins (> 50 amino acids) and peptides (<50 amino acids)
- Principally of C, H, O and N, (found
especially in meat, beans, eggs, dairy)
- Essential part of organisms and
participate in virtually every process
within cells.
- Monomer: Amino acid
- Peptide bonds
- Condensation reaction
(dehydration)/hydrolysis(reverse)

Question 17

Amino acid

Answer 17

Amino acids (20 different)
Structure: 
Central carbon called carbon α bonded to: 
- Amino group
- Carboxylic acid
- Hydrogen
- R group/side chain (identifies the 
  amino acid)
• Functional groups: amino and 
  carboxylic acid

Question 18

Peptide bond

Answer 18

The bond connecting monomers.
- An amide group is formed
- Connects the carboxylic acid to the 
  amino group with condensation 
  reaction (dehydration) OH from CA 
  and H from AG.

Question 19

Do amino acids have directionality?

Answer 19

Yes.

N-terminus has an Amino group free and C-terminus has a carboxylic acid free.

Question 20

Structure of proteins

Answer 20

4 levels of structure of proteins:
• Primary structure: sequence of amino 
  acids
• Secondary structure: hydrogen bonds 
  between the amide groups (bonds)
• Tertiary structure: interaction between 
   the R- chains
• Quaternary structure: aggregation of 
   many subunits

Question 21

Denaturation of proteins

Answer 21

Sometimes irreversible.
Protein not functional.
Temperature, pH or chemicals disrupt interactions, causing the protein to lose its quaternary structure.