2.3 Carbohydrates and Lipids Flashcards
Why is C important?
organic compounds contain C
each C forms 4 covalent bonds, allowing a great diversity of compounds to exist
additional groups added to the C-C molecule gives the organic compound its properties
covalent bonds are strong so molecules are stable
What is the Theory of Vitalism?
it was once thopught that living organisms were composed of organic molecules that could only be produced by a vital force
this theory was falsified by discoveries in biochemistry and the structure of DNA
the chemical synthesis of Urea also falsified this theory:
- found in human urine
- in 1828 Fredrich Wohler synthesised it artificially
- using silver isocyanate and ammonium chloride
What is metabolism?
web of all enzyme catalysed reactions in a cell or organism
What is anabolism?
synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions
e.g. sugar from CO2
What is catabolism?
the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers
e.g. respiration
What are carbohydrates?
made of C, H and O
(CH2O)n
used to store energy
Monosaccharides
are monomers (single sugar) also known as reducing sugars are small enough to pass through a cell membrane e.g. glucose (C6H12O6) - photosynthesis and respiration, ribose (C5H10O5) - component of RNA, fructose - made by plants found in fruits, galactose - breakdown of lactose, deoxyribose
Forms of glucose
D glucose - living things
L glucose - not in living things
alpha D glucose - makes up starch and glycogen polymers
beta D glucose - makes up cellulose polymer
Disaccharides
produced by combining monosaccharides
sucrose: table sugar - glucose and fructose - condensation reaction in plants
lactose: milk sugar - glucose and galactose
maltose: malt sugar - two glucose
relationship between mono and disaccharides
condensation reaction joins two monosaccharides to form a disaccharide by removing a water molecule and forming a glycosidic bond
hydrolysis reaction splits a disaccharide by providing a water molecule and breaking the glycosidic bond to form two monosaccharides
Polysaccharides
many sugar units
e.g. starch, glycogen, cellulose
Starch
can be long branched (amylopectin) or unbranched (amylose)
chains of alpha D glucose
the way that plants store their carbohydrates
if amylose: helical chains, circle type ring
if amylopectin: branches every approx 20 subunits
Glycogen
long branched chains of alpha D glucose the way that animals store their glucose insoluble so large amounts can be stores very very long chains
Cellulose
unbranched beta D glucose plant cell walls humans and most vertebrates are unable to digest cellulose because enzymes that break down the linkages are not found in vertebrates linear chains
What are lipids?
C compounds
mostly or entirely hydrophobic
fats and waxes are solid at room temp
insoluble in water
important energy storage compounds - greatest energy per gram of all food types
3 main types: triglycerides, phospholipids and steroids
Triglyerides
most common
three fatty acids + glycerol
formed during a condensation reaction between three fatty acids and one glycerol
Type of fatty acids
saturated: max number of H atoms, animal origin, single covalent bonds
unsaturated: one or more double bonds, plant origin
mono-unsaturated: one double bond
poly-unsaturated: two or more double bonds
cis unsaturated: H atoms bonded to the same side of the double bond
trans unsaturated: H atoms bonded to opposite sides (coronary heart disease)
Phospholipids
two fatty acids + one glycerol
phosphate group rather than third fatty acid
partly hydrophobic - amphipathic
Steroids
17 C atoms in 4 rings
e. g. cholesterol, testosterone, estrogen, cortisol and Vitamin D
* Vit D has one broken ring
Energy storage (carb vs lipid)
carbs: 100 g = 1760 kJ (but 1g of glycogen is associated with 2g water)
protein: 100g = 1510 kJ
lipid: 100g = 4000 kJ
lipid energy per gram is double
lipids can be stored and utilised without water and so, therefore, is 6x more effective than carbs
