biological molecules Flashcards
What are the four biological molecules and what elements do they contain?
Carbohydrates: C, H and O
Lipids: C, H,O
Proteins: C, H , N, O , S
Nucleic acids: C, H, O, N, P
Why is water polar?
Water contains O-H bonds where the electrons are unequally shared creating separate regions of positivity and negativity,
What are the key characteristic of water and why does it have these characterisitics?
- Water has a relatively high BP as it has h-bonding which requires a lot of energy for H2O to evaporate
- Water is more dense in a solid state (as ice) as the h-bonds will position the polar molecules slightly further apart creating an open structure that is less dense than liquid.
- Water has cohesive and adhesive properties as it can form h-bonds with other water molecules and other materials
How do the key characteristics of water help life?
- Acts as a solvent where many solutes can dissolve , acting as a medium for chemical reactions and transporting dissolved compounds.
- Acts as a transport medium with the action of cohesion and adhesion it exhibits capillary action such as water travelling up the xylem.
- Acts as a coolant to buffer temperature changes and maintaining constant temperature in environments
- Water is stable and will not change temperature making a good environment for aquatic creatures to live in. Dense ice can act as an insulating layer
- Surface tension due to cohesive properties act as a habitat for small creatures like pond skaters
What is a monosaccharide, disaccharide and polysaccharide? Give examples.
MS: a single sugar unit/monomer such as glucose, fructose and ribose
DS: When two MS link together, for example lactose and sucrose
PS: A polymer made up of MS such as glycogen, cellulose and starch
What is the structure of glucose and what is the difference between a beta and alpha glucose?
Glucose is a hexose monosaccharide with 6 carbons with chemical formulae C6H12O6
a-glucose has a hydrogen above the OH on the first and second carbon
b-glucose will have a OH group above the H on the first carbon
What is a glycosidic bond? What types of glycosidic bonds are there?
A glycosidic bond is formed between two glucose molecules via a condensation reaction where the two OH- groups will react.
Straight chained molecules will have 1,4 glycosidic bonds whereas branched will have 1,4 and 1,6 glycosidic bonds.
What is starch, what polysaccharides are in starch and what are their structures? Why do they have these structures?
Starch is a chemical energy store found in plants made up of amylopectin and amylose.
Amylose: Made up of alpha glucose joined together via 1-4 glycosidic bonds and twists to form a helix. This makes it more compact and less soluble.
Amylopectin: Is branched so it has both types of glycosidic bonds making it more accessible to be broken off by enzymes and converted to glucose for energy use.
What is glycogen, its structure and purpose?
Glycogen is the energy store equivalent of starch found in animals and fungi which is more branched than amylopectin making it compact, ideal for storage. Branched = more accessible and insoluble.
What is a hydrolysis reaction?
Hydrolysis reactions are the addition of H2O molecules which reverse the effect of condensation reactions.
What is a triglyceride?
A lipid that consists of a glycerol molecule connected to three fatty acid tails.
How does glycerol form a bond with fatty acids?
Via esterification when the two -OH bonds interact and form an ester bond.
This is a condensation reaction
What is the difference between a saturated and an unsaturated fatty acid?
Saturated: Presence of no double c=c bonds , they do not kink and are solid fats which are more unhealthy.
Unsaturated: Presence of double c=c bonds, they kink and occur as oils which are more healthy in the human diet
What are phospholipids?
Similar to triglycerides but one of the fatty acids are replaced by a phosphate group.
They have hydrophobic tails but hydrophilic heads .
They can create a bilayer arrangement important in the formation of cell membranes.
What are sterols and what is cholestral?
Sterols are complex alcoholic molecules that are a type of lipid which also have dual hydrophilic and hydrophobic traits.
Choestral is a sterol which are positioned in-between phospholipids by adding stability to membranes and regulating their fluidity.
