Lecture 3, 4, 5: Biological Molecules

Question 1

what are the four families of biomolecules

Answer 1

carbohydrates, lipids, nucleic acids, and proteins

Question 2

structural vs. storage carbohydrates:

Answer 2

1. Storage Polysaccharides:
   - Store sugar monomers to be broken down for energy
   - Helical and branched
   - Released by hydrolysis reactions
2. Structural Polysaccharides:
   - Used in cell structure
   - Straight, never branched
   - Hydrogen bonds help build plant fibers

Question 3

monosaccharides:

Answer 3

(change form randomly): have the formula CH2O
- Can occur in a straight chain or in a ring structure
- Ring form is favoured over straight chain (open form)

Question 4

disaccharides:

Answer 4

two linked monosaccharides
- Formed by glycosidic linkages (catalysed by enzymes during a dehydration reaction)
- Alpha linkages: can be hydrolysed (broken
Beta linkages: mammals cannot break down beta linkages (ex. Lactose intolerance)

Question 5

polysaccharides:

Answer 5

very long chain of monosaccharides

Question 6

Fats: two main types of molecules

Answer 6

1. Fatty acids- (16-18 long) hydrocarbon chain, ending in a carboxyl group and joined together with nonpolar C-H bonds
2. Glycerol: joined via ester linkages in a dehydration reaction

Question 7

The technical term for fats

Answer 7

triglyceride

Question 8

lipids:

Answer 8

• Not a true polymer or big enough to be a macromolecule
• All hydrophobic
• Very few polar bonds, are associated with oxygen
• Utilise a hydrocarbon backbone

Question 9

saturated fat vs. unsaturated fat

Answer 9

Saturated fat:
- As many H as possible
- No double bonds present
- Solid at room temp, high melting temp
- Pack closely together via van der Waals interactions

Unsaturated fat:
- At least one cis double bond, resulting in kink/fold
- Has less then the full amount of H (at least two less than max)
- Usually plant or fish fats, usually oils
- Lower melting temps, less van der Waals interactions

Question 10

phospholipids:

Answer 10

• Major component of cell membranes
• Have two fatty acid tails
• The 3rd hydroxyl group of the glycerol is attached to a phosphate group (neg. charge)
• The partial charges of the phospholipid give it a unique structure: hydrocarbon tails are hydrophobic, phosphate group & polar molecules are hydrophilic (polar), important feature of phospholipid bilayers!

Question 11

four levels of protein structure:

Answer 11

primary, secondary, tertiary, quartenary

Question 12

Primary structure:

Answer 12

sequence of amino acids in the polypeptide chain

Question 13

Secondary structure:

Answer 13

the coils and folds of the protein’s overall shape
- Alpha helix: the polypeptide backbone spiral/coil
- Beta pleated sheet: lay side-by-side with H bonds in between strands

Question 14

Tertiary structure:

Answer 14

the overall 3D shape of a single polypeptide
- Folding results from hydrophobic interactions
- Disulfide bridges: really strong, hold parts of protein in place, formed when cysteine R groups covalently bond with their sulfhydryl groups

Question 15

Quaternary structure:

Answer 15

the stable formation of two or more polypeptides

Question 16

amino acids:

Answer 16

20 amino acids that make up proteins, each differing by their R group
all have the same base, different R group attached

Question 17

group 1 of amino acids:

Answer 17

glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, proline
- R groups are non-polar, therefore hydrophobic,
Tends to be in the center of proteins away from water

Question 18

group 2 of amino acids:

Answer 18

serine, threonine, cysteine, tyrosine, asparagine, glutamine
- Amino acids are polar, have polar bonds in the R-groups
- Can interact with water, form H-bonds
- Hydrophilic, tend to be on outside of proteins

Question 19

group 3 of amino acids:

Answer 19

aspartic acid, glutamic acid, lysine, arginine, histidine
- These amino acids carry a charge due to their R groups
- ‘Acidic’ amino acids have R groups with overall negative charge, carboxyl group disassociates at pH 7
- ‘Basic’ amino acids have R groups with an overall positive charge
- Hydrophilic, interacts with water

Question 20

amphiphilic/amphipathic:

Answer 20

molecules with hydrophobic and hydrophilic parts

Question 21

why do phospholipids form membranes

Answer 21

tails = hydrophobic
head = hydrophilic
when put in an aqueous solution, the tails look to escape the water, forming a lipid bilayer, where the heads are on the outside and tails are on the inside
this creates a water-proof, insoluble barrier, making membranes effective at separating the inside and outside of a cell