Carbohydrates Flashcards
Equation of photosynthesis
6 carbon dioxide + 6 water —— (chlorophyll) —> glucose + 6 oxygen
Elemental composition
Carbon
Hydrogen
Oxygen
Classification
Monosaccharides
Disaccharides
Polysaccharides
Monosaccharides
Structure : simple sugar that contains 1 single sugar unit
Chemical formula : C6H12O6
Examples : glucose (fruit)
Disaccharide
Structure : 2 monosaccharide joined. Loss of water molecule
Chemical formula : C12H22O11
Examples : lactose (glucose + galactose - milk)
Polysaccharide
Structure ; : 3 or more monosaccharides joined. Condensation reaction with each new link. Straight or branched
Chemical formula: (C6H12O6)n
Example : cellulose/dietary fibre (skins of fruit + veg)
Sources of carbs
Sugar - table sugar, biscuits, jam
Starch - potatoes, pasta, flour
Cellulose - fruit and veg, brown bread, whole meal pasta
Properties of sugar - solubility
Soluble in water. Syrup forms when large amount of sugar added to small amount of water
Eg. Preservation in canned fruit
Properties of sugar - Maillard reaction
Non enzymic browning of food due to reaction between amino acids and sugars under dry heat
Eg. Roast potatoes, shortbread
Properties of sugar - caramelisation
160 sugar melts and caramelises
Above 177 caramel will burn
Eg. Caramel squares
Properties of sugar - hydrolysis
Reverse of condensation reaction. Happens naturally. Water + enzymes split disaccharides into two monosaccharides (lactose = glucose + galactose)
Properties of starch - solubility
Insoluble in cold water
Properties of sugar - dextrinisation
When dry heat added to starchy food, short - chained polysaccharides (dextrins) form. Further heating = combine to form pyrodextrins (colour change brown)
Eg. Browning of bread to make toast
Properties of starch - hydrolysis
Disaccharides—> 2 monosaccharides (lactose —> glucose + galactose)
Effects of heat - dry
Maillard reaction (sugar - roast potatoes)
Caramelisation (sugar - caramel squares)
Dextrinisation (starch - toast)
Effects of heat - moist
Syrup formation (sugar - canned fruits)
Gelatinisation (starch - white sauce)
Cellulose (non starchy - potatoes)
Pectin (non starchy - jam)
Biological function
- Heat ans energy. Energy for all activities and keeps body temp at 37
- Sufficient amount of carb intake= protein can be used for primary function (growth and repair of cells)
- Cellulose passes through intestinal tract and helps form peristalsis and speeds up food waste (prevents bowel disorders)
- Excess= glycogen and stored in liver and muscles (long term e r)
- May convert to fat stored as adipose tissue under skin (insulated body and e r )
RDA + RI
Average, adults - 260 (sugar 90)
25-35 cellulose
1g carb = 4 kcal
Too much starch - obesity, type 2 diabetes, dental cavities
Too little cellulose - bowel disorders
Digestion
Salivary glands - saliva - salivary amylase - starch - maltose
Pancreas - pancreatic juice - amylase - starch - maltose
S intestine - intestinal juice - (maltase - maltose - glucose) (sucrose - sucrose - glucose and fructose) (lactase - lactose - glucose and galactose)
Absorption and utilisation
Monosaccharides—> wall of villi—> bloodstream—> hepatic portal vein—> liver —> fructose +galactose=glucose—> oxidised (heat and energy)—> converted (stored in liver and muscles)—>
Excess=fat. Adipose tissue
Fibre tips
- Drink water
- Eat fruit
- Whole grain bread
Explain the term gelatinisation
When starch combined with liquid and heated 55-70 the grains swell and burst and absorb liquid around them increasing viscosity ans forms a sol. When mixture cools, water molecules become trapped and forms a gel. Eg roux sauce and popcorn
