Chapter Twelve : Food and Energy Flashcards
Monosaccahrides
White crystalline solids Soluble Strong reducing agents Monomers of carbohydrates Not broken down during digestion
Disaccharides
When 2 monosaccharides join to make a carbohydrate
Maltose - 2 glucose molecules
Sucrose - 1 glucose/1 fructose
Lactose - 1 glucose/1 galactose
Polysaccharides
When more than 10 monosaccharides join together Considered complex carbs Non-crystalline Insoluble Tasteless
Bonding between monosaccharides
A condensation reaction between hydroxyl on C1 and C4 occurs giving a glycosidic link
Sweetness/GI/Energy of sugars
Sweet -Aspartame>Fructose>Sucrose>Glucose>Lactose
16.7kjg-1
GI - Glucose>Sucrose>Lactose>Fructose>Aspartame
Aspartame
White Odourless Soluble crystalline powder Dipeptide Made up of aspartic acid, phenylthaline and methanol 200x sweeter than sugar
Types of polysaccahrides
Starch
Glycogen
Cellulose
Starch
Major storage form of glucose in plants
Condensation polymer of alpha-D-glucose
Made up of amylose and amylopectin
Amylose
20% of starch Soluble Smaller than amylopectin 50-300 alpha-D-glucose Straight chain linkage C1 to C4 Spiral formation
Amylopectin
Insoluble
Loosely branched molecule
300-5000 alpha-D-glucose
Both C1 to C4 and C1 to C6 link
Glycogen
Storage form of glucose in animals in liver/muscles
Lots of branching from C1 to C6
C6H12O6 + 6O2 -> 6CO2 + 6H2O
Cellulose
Condesation polymer of beta-D-glucose
Main structural component of cell wall in plants
Humans cannot hydrolyse cellulose as we do not have the enzyme therefore it doesnt provide energy
Provides fibre
Lactose intolerance
When an individual has an insufficient amount of lactase in the body and cannot break down lactose
Glycemic Index
Shows how quickly a carbohydrate is borken down and absorbed into the bloodstream Glucose is 100 More fibre = lower GI More amylopectin = Higher GI More amylose = Lower GI
What factors affect absorption of carbs
Ripeness
bran - limits ability of enzymes to reach starch
Fibre - takes up space and slows digestion
Sugars - somesugars have lower GI
Proteins,fats and oils - Slow down stomach emptying
Food processing - Smaller particles have greater surface area
Cooking method - food swells and softens
Acidity - Slows down stomach emptying
Lipids
Fats - solid Oils - liquid Energy stores Components in cell membranes Hormone production Protection of vital organs Transport fat-soluble vitamins
Triglycerides
A fat or oil formed by condensation reactions between glycerol and 3 fatty acids
Types of fatty acids
Saturated - all single C-C bonds
Mono-unsaturated - 1 double C=C bond
Poly-unsaturated - Multiple C=C bond
Properties of fats/oils
Hydrophobic, less dense than water
Saturated fatty acids are solid and are formed from straight-chain fatty acids which have high dispersion forces, high stability
Unsaturated fatty acids have lower dispersion forces disrupting how close they pack together, they are more easily oxidised
Hydrogenation
Hydrogen is added to unsaturated fatty acids to convert them to saturated fatty acids
The amount of hydrogen added determines melting point
Iodine number
Measures degree of unsaturation
Mass of iodine that reacts with 100g of fat/oil
Iodine reacts with C=C bonds
Oxidation of food
When foods go rancid
When food reacts with oxygen
Unsaturated fats are more susceptible from the C=C bonds
Molecules react with O2, free radicals formed cause destructive chemical reactions, the ketones, aldehydes and acids produce bad smells and flavours
Preventing rancidity
Antioxidants slow down oxidation and prevent food from spoiling
They are reducing agents and therefore preferentially oxidised
Vitamin C is a natural antioxidant
Using vacuum packaging, full containers, dark and cold storage, opaque containersq
Essential fatty acids
Must come from the diet as they cannot be synthesisesd
Omega 3 fatty acid - double bond on 3rd carbon
Omega 6 fatty acids - double bond on 6th carbon
Needed for processing of inflammation and nervous system
Flaxseed oil, tuna, linseed
Liver, kidney, blood and immune system
Calorimetry
Is the measurement of the amount of heat released or absorbed in a chemical reaction,change of state or formation of a solution
Calorimeters
Insulated container with a fixed amount of liquid which the temp rise and fall is measured.
Temp cahnge is converted to energy change
Calibration factor(JC-1)
VIt/temp change
Solution calorimeter
Energy change in aqueous solution
Acid-base or dissolution
Heat loss in calorimeters
Good insulation = little heat loss, temp increases quickly, maintenence of temp when current is off
Bad insulation = lots of heat loss, temp decreases quickly, temp decreases after current is off
Bomb calorimeter
Used to determine energy changes for gases
Faster reaction than solution calorimeter
However energy content is different to what it is when consumed as the body can’t use fibre and energy can be converted to heat
Why is glucose used as a standard for GI values?
GI index is a measure of how quickly carbs are hydrolysed to glucose, glucose requires no hydrolysis so will have a high value. it is easy and available for use
What does available carbohydrate mean?
The fraction of carbohydrates that can be digested by human digestion
Why do athletes need high GI carbohydrates?
athletes have a high energy demand due to consumption of glucose in muscles
havin high gi foods will allow it to be avialble in a short period of time
Electrical calibration
kJ/temp change
Purpose of calibration
Relates the heat change to a temp change so when temp change occurs in a subsequent reaction the enthalpy change can be calculated
