Chapter 5 - Structure and Function of Large Biological Molecules Flashcards
How are polymers synthesised
- The reaction which connects monomer to monomer is a Condensation reaction: a reaction which connects a monomer to another monomer with a covalent bond through the loss of a small molecule
- If a water molecule is lost in the process then its called a Dehydration Reaction: a condensation reaction if it’s a water molecule that is lost
How Polymers are broken down
- Polymers are disassembled to monomers through Hydrolysis(reverse of dehydration)
- The bonds are broken by the addition of a water molecule
○ A hydrogen from water joining to one monomer while the remaining hydroxyl group joins the other monomer
- The bonds are broken by the addition of a water molecule
Carbohydrates:
includes sugar and polymers of sugar
- Monosaccharides: single sugars - Disaccharides: double sugars - Polysaccharides: polymers of sugar
Monosaccharides
- have generally formulas made up of the same molecular unit CH2O
- diversify based on the way their parts are spatially arranged around asymmetric carbons(a carbon attached to 4 different atoms)
- are major nutrients for cells and serve as fuel for cellular respiration
Classifications of Monosaccharides
- The location of the carbonyl group determines whether a monosaccharide is an aldose or a ketose
○ Glucose is the Aldose because carbonyl group is at the end - Fructose, an isomer, is ketose because carbonyl group is in the middle
Disaccharides
Consists of two monosaccharides joined together by a glycosidic linkage, which is a covalent bond formed through dehydration between two monosaccharides
E.g. - Lactose, Maltose, Sucrose
need to be broken down into monosaccharides before being used as an energy source by an organism
Lactose Intolerance
a condition where lactase, an enzyme which breaks down lactose is missing, and instead lactose is broken down by intestinal bacteria, causing gas and cramping
Polysaccharides Function
- Serve either as storage material which is hydrolyzed when needed or as building materials for the cell
- The function is determined by the monosaccharides and its position of glycosidic linkages
Storage Polysaccharides in plants:
- Plants store starch as granules within plastids
- This stored starch can then be hydrolyzed into glucose for a fuel source
- Starch is composed of glucose monomers being joined by 1-4 glycosidic linkages(linkages at the 1st and 4th carbon)
Storage Polysaccharides in Animals:
- Animals store glycogen mainly in liver and muscle cells
- This can be broken down to create glucose for a fuel source
Glucose levels can be depleted if not enough carbohydrates are eaten to replenish
- This can be broken down to create glucose for a fuel source
Structural Polysaccharides in Plants
- In plants, cellulose is a major component of cell walls
- Similar to starch with 1-4 linkages however as the glucose monomers in cellulose form rings in the ‘beta’ configuration(upside down compared to its neighbor)
- This difference gives cellulose a distinct straight 3d shape allowing it to bond lying parallel to other cellulose molecules, giving cell wall structure
- Due to ‘beta’ configuration also, enzymes are unable to hydrolyze the linkages
Structural Polysaccharides in ANimals
- Chitin is also important and used by arthropods(spiders, crustaceans) to build exoskeletons
- Similar to cellulose with ‘beta’ linkages except the glucose monomer of chitin has a nitrogen containing attachment
- Humans and most animals are unable to digest cellulose due to enzymes being unable to hydrolyze its glycosidic linkages
- As a result it passes through our digestive tract, and stimulates the release of mucus to aid the smooth passage of food through
Fats:
- Fats are not polymers, but are composed of many smaller molecules joined by dehydration reactions
- Composed of a glycerol molecule joined to three fatty acid tails by an ester linkage
- Water separates from fat because its hydrophobic
- Major function of fats are as energy stores due to hydrocarbon chains being rich in energy
Lipids
any of a large group of biomacromolecules which are hydrophobic due to their molecular structure
Fatty Acid
- Has a long carbon skeleton usually 16-18 carbons long
- At one end is a carboxyl group(C=O-OH / Acid)
- Rest of the skeleton is a hydrocarbon chain which has relatively non-polar C-H bonds making it hydrophobic
- Each fatty acid is joined to a glycerol through dehydration reaction
Different Types of Fats: Saturated Fat
- Saturated Fat: all carbons in the hydrocarbon tail are connected by single bond, maximizing the number of hydrogen atoms that can attach
○ At room temperature it can solidify due to molecules being able to pack close together
○ E.g. lard, butter
Different Types of Fat: Unsaturated Fat:
has one or more double bonds between carbons in the hydrocarbon tail, reducing the number of hydrogen atoms which can attach
○ These double bonds are cis double bonds, causing kinks in the chains
○ This makes it liquid at room temperature
○ E.g. oils,
Hydrogenated Vegetable Oils
means hydrogens have been added to unsaturated fat foods like peanut butter to prevent lipids from separating out into liquid form by converting it to saturated fat
Adipose Cells
- Humans and mammals stock their long term food reserves in adipose cells which swell and shrink as fat is deposited and withdrawn
- Adipose tissues also cushion vital organs and insulate the skin
Phospholipids
similar to a fat molecule but only has two fatty acid chains attached to the glycerol head while the third is attached on top to a phospholipid, creating an negative charge
- Essential for cells as they make up the majority of cell membranes - Typically has a smaller charged or polar molecule attached
How Phospholipids arrange themselves into a bilayer
- Has a hydrophilic head, due to the polar nature of the phosphate group and extra molecule, and hydrophobic tail
- Because the head is polar, and has an affinity for water, the phospholipid orients itself with the tails shielded from water