Lecture 6: Sugars and Lipids Flashcards
1
Q
Sugar Functions
A
- storage (ex. starch)
- structure (ex. cellulose; plant cell wall)
- modifies proteins (They modify the part of the membrane protein that face outwards of the cell)
2
Q
Types of Carbohydrates
A
Monosaccharides: monomer of glucose
Disaccharides: consist of two monosaccharides
Polysaccharides: are composed of hundreds to hundreds of thousands of monosaccharides
3
Q
General formula for carbohydrate monomer
A
- multiples of CH2O, e.g. glucose C6H12O6
- always have same amount of C and O
• A monomer can be either:
1. An aldose: Carbonyl group at
end of carbon chain
2. A Ketose: Carbonyl group in
middle of carbon chain
4
Q
Isomers
A
- In many isomers a group is attached to different carbon atoms.
- In Optical isomers (aka stereoisomers) a group is attached in different ways to the same carbon atom. Optical isomers are mirror images of each other.
- Optical isomers occur whenever a carbon has four different atoms or groups attached to it.
5
Q
Glucose vs. Galactose
A
- 2^4 = 16 possible stereoisomer combinations
6
Q
Linear glucose vs. ring form
A
- sugars can also be in ring form when in water (Oxygen from the 5-C bonds to the 1-C, resulting in a ring structure)
- Can form 2 stereoisomers, alpha and beta.
7
Q
Glycosidic linkage
A
- Happens between C#1 and OH group
- Lots of combinations (11)
- Only two are important
- B1-4 linkage and A1-4 linkage
8
Q
Alpha 1,4 Linkage
A
- Creates Maltose
- Not easily broken (stable)
- The swiggle bond denotes that it can still open and close (denotes unknown or unspecified orientation)
- free OH on C#1 allows conversion to aldehyde
- BELOW SEA LEVEL
- results in starch: moderately branched, amylopectin in plants
highly branched, glycogen in animals (used for energy storage in animal cells)
9
Q
Beta 1,4 Linkage
A
- ABOVE SEA LEVEL
- Makes cellobiose, which gives rise to cellulose (always unbranched)
- In reality you have to flip second molecule around 180 so that HO-CH2 is pointing down, and the covalent bond is straight.
- The flipping of the second glucose molecule gives rise to different property (symmetrical), then the molecules is very linear and stable structure (lots of H-bonds)
- Found in plant cell walls, and wood
10
Q
Lipids
A
• Insoluble in water •Roles for lipids in organisms include: - Energy storage (fats and oils) - Cell membranes (phospholipids) - Capture of light energy (carotenoids) - Hormones and vitamins (steroids and modified fatty acids) - Thermal insulation - Electrical insulation of nerves - Water repellency (waxes and oils)
11
Q
Beta- Carotene
A
- found in carrots, split into vitamin A (important for eyesight)
12
Q
Steroids
A
- Vitamin A and D are added to milk because they are lipid soluble (only take up vitamins with the fat)
13
Q
Fatty Acid
A
- has carboxyl group
- has hydrocarbon chain
- depending on how long the chain is, determines how water soluble it is
14
Q
Fats from via..
A
- dehydration reactions: Glycerol molecule + three fatty acids which form 3 ester linkages
15
Q
Phospholipids
A
- have two hydrophobic fatty acids (tails) and one hydrophilic head group attached to glycerol
- consist of choline & phosphate group (hydrophilic)
- Fatty Acid (2) (hydrophobic)
