Biomolecules Flashcards
Biomolecules
Carbohydrates
Lipids
Nucleic acid
Proteins
Carbohydrates
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.
Monomers of carbohydrates
- 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.
Condensation reaction of carbohydrates (Exam)
Glucose+Fructose → Sucrose
Dehydration reaction because a molecule of water H2O is released.
The reverse reaction is called Hydrolysis.
Two types of carbohydrates
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.
Lipids
- 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
Main biological functions of lipids
- Long time energy storage*
- Signaling
- Insolation
- Structural components of cell membranes*
- Building blocks for hormones*
Fatty acids
- 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.Triglycerides
- Glycerol + 3 fatty acids
- Bond formed is an ester (condensation
reaction (dehydration) / hydrolysis)
Phospholipids
- Glycerol + 2 fatty acids + phosphate group + modifier - Building blocks of biological membranes. - Phospholipid bilayer.
Steroids
- Structure of 4 fused rings.
- Cholesterol (structural component of
cell membranes + precursor
biosynthesis hormones, bile acid and
vitamin D) - Signaling hormones (cortisol).
Nucleic acid
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.
Nucleotides
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.
Phosphodiester bond
The bond connecting monomers.
=> between the OH- on the C3 of the
sugar and the phosphate group of
another nucleotide.
DNA and RNA
- 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.
Proteins
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)
Amino acid
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
Peptide bond
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.
Do amino acids have directionality?
Yes.
N-terminus has an Amino group free and C-terminus has a carboxylic acid free.
Structure of proteins
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
Denaturation of proteins
Sometimes irreversible.
Protein not functional.
Temperature, pH or chemicals disrupt interactions, causing the protein to lose its quaternary structure.
