Unit 2.3 Carbohydrates And Lipids Flashcards
Essential idea carbs and lipids
Compounds of carbon, hydrogen and oxygen are used to supply and store energy
3 categories of carbohydrates
- monosaccharides
- disaccharides
- polysaccharides
Monosaccharides
- simplest form of carbohydrate
- 2 to 7 atoms
- carbons joined to a hydroxyl group (-OH)
- e.g ribose, glucose, fructose, galactose
- act as a monomer
- linked by condensation reaction to form a glycosidic bond to produce a disaccharide
Glucose
-monosaccharide that exists in two forms D-glucose and L-glucose
With the same chemical formula but a different arrangement
- 2 forms of D-glucose alpha-d-glucose and beta-d-glucose
Difference between alpha-D glucose and beta-D glucose
Differ in placement go -OH group on carbon 1
Alpha d glucose = -OH below -H
Beta D glucose = -OH above -H
Polysaccharides
Large molecules made of multiple monosaccharides e.g cellulose, starch and glycogen
Function of polysaccharides
- polysaccharides play an important role in energy storage
- starch used to store energy in plants
- glycogen used to store energy in animals
- ## can also be a structural component, cellulose in plants creates cell wall and prevents bursting
Disaccharides
- polar and water soluble
- maltose, lactose, sucrose
Starch in industry
- amylopectin found in starch gives it stickiness and is useful in food industry or to create adhesives or lubricants
Lipids
Diverse group of organic compounds, all which have little to no affinity for water
Triglycerides
Formed by condensation reactions between one glycerol and three fatty acids, creating fats (solid at room temp) and oils (liquor at room temp)
Fatty acids
Fatty acids are carboxylic acids (possess a carboxyl group) attached to the head of a long hydrocarbon chain. Can be saturated and unsaturated
Saturated fatty acid
No double bonds between any of the carbon atoms in the hydrocarbon chain of
Unsaturated fatty acid
Can be monounsaturated with one double bond or polyunsaturated with many double bonds. Can be trans or cis depending on position of the two hydrogen atoms (trans = bent, cis = straight)
Cis-isomers
- commonly occur in nature
- two hydrogen atoms attached to same side of two carbon atoms
- lower melting points and are generally liquid at room temperature
- healthier, promote good cholesterol
Trans-isomers
- artificially produced when lipids formed by polyunsaturated fatty acids from plants are partially hydrogenated chemically
- makes fatty acids behave like solids with higher melting points
- dangerous for cardiovascular system
Phospholipids
- One fatty acid in a triglyceride is replaced by a phosphate group (-PO4)
- major component in membrane
Lipids and energy stored
- lipids have a higher energy content than carbohydrates
- lipids also act as thermal insulators
- 1 gram of lipid has twice the energy as 1 gram of glycogen
- each gram of glycogen is associated with 2 grams of water, bulking up organisms which is bad for mobility
Lipids and health
- high energy content may contribute to obesity when consumed in excess
- hypothesis = trans fats and saturated fats contribute to the formation of atherosclerotic plaques in the arteries which lead to heart attacks
- positive correlation examined, but no direct causal link found
- exceptions = Mediterranean diet and Maasai of Kenya
