Lecture 3, 4, 5: Biological Molecules Flashcards
what are the four families of biomolecules
carbohydrates, lipids, nucleic acids, and proteins
structural vs. storage carbohydrates:
- Storage Polysaccharides:
- Store sugar monomers to be broken down for energy
- Helical and branched
- Released by hydrolysis reactions - Structural Polysaccharides:
- Used in cell structure
- Straight, never branched
- Hydrogen bonds help build plant fibers
monosaccharides:
(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)
disaccharides:
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)
polysaccharides:
very long chain of monosaccharides
Fats: two main types of molecules
- Fatty acids- (16-18 long) hydrocarbon chain, ending in a carboxyl group and joined together with nonpolar C-H bonds
- Glycerol: joined via ester linkages in a dehydration reaction
The technical term for fats
triglyceride
lipids:
- 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
saturated fat vs. unsaturated fat
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
phospholipids:
- 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!
four levels of protein structure:
primary, secondary, tertiary, quartenary
Primary structure:
sequence of amino acids in the polypeptide chain
Secondary structure:
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
Tertiary structure:
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
Quaternary structure:
the stable formation of two or more polypeptides
amino acids:
20 amino acids that make up proteins, each differing by their R group
all have the same base, different R group attached
group 1 of amino acids:
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
group 2 of amino acids:
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
group 3 of amino acids:
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
amphiphilic/amphipathic:
molecules with hydrophobic and hydrophilic parts
why do phospholipids form membranes
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
