Chapter 2: carbohydrates Flashcards
What is a carbohydrate molecules made up of?
A carbohydrate molecule is made up:
• carbon (C)
• hydrogen (H)
• oxygen (O)
• In plants, glucose is formed when carbon dioxide and water react during
photosynthesis in the presence of chlorophyll and sunlight.
What are the end products of carbohydrates?
End products are glucose, fructose & galactose.
What are monosaccharides?
• simplest form of sugar molecules • known as single sugar • dissolve easily in water to form colourless, sweet solutions • types: — glucose — fructose — galactose
What are Disaccharides?
known as double sugars
- made up of two monosaccharide molecules
- white crystalline solids which are sweet and water-soluble
- types:
— sucrose
— lactose
— maltose
What are Polysaccharides?
complex carbohydrates which are made up of many monosaccharide molecules • not sweet, not water-soluble • types: — starch — cellulose (substances in cell walls of plants) — pectin (soluble dietary fibre) — glycogen
What is fructose? (Monnosaccharides)
Fructose or fruit sugar is the sweetest natural sugar. It can be found in honey, fruit and certain vegetables (eg cabbage and french beans)
What is galactose?(Monnosaccharide)
galactose does not exist alone in food.
It bonds with glucose to form lactose, a disaccharide found in milk
What is glucose?(Monosaccharide)
Glucose is the most important monnosaccharide as it serves as a main source of energy.
Fruit, certain vegetables and honey are good sources of glucose
What is lactose? (Disaccharide)
A molecule of lactose consist of a glucose molecule bonded to a galactose molecule. Lactose is found naturally in dairy milk.
What is Maltose? (Disaccharide)
A molecule of maltose consist of two bonded glucose molecules. Maltose is found naturally in sugar molasses, germinating barley and cooked sweet potato
What is sucrose? (Disaccharide)
A molecule of sucrose consist of a glucose molecule bonded to a fructose molecule.
Sucrose is found naturally in sugar cane, honey, sugar beet, fruit and certain vegetables (eg cabbage and carrot)
What is starch? (Polysaccharide)
Starch consists of hundreds of gluctose molecules joined together into a chain-like molecular structure. It is abundant in cereals (eg white rice) and tubers (eg potato)
What is Cellulose? (Polysaccharide)
Cellulose is an insoluble component fo cell walls that provides support to plants. Fruit (eg apple and orange), vegetables (eg carrot and chye sim) whole grains (eg brownrice) and beans (eg red beans) are good sourvces of cellulose
What is Pectin? (Polysaccharide)
Pectin is a soluble component found in the cell walls of certain plants. Apple, apricot citrus fruit (eg lemon and grapefruit) and plum are good sources of pectin.
What are examples of sources of simple carbohydrates?
Simple carbohydrates are food which is naturally rich is simple sugars - gluctose, fructose, lactose and maltose.
What are examples of sources of complex carbohydrates?
complex carbohydrates are food that are high in polysaccharides - starch, cellulose and pectin.
Starchy vegetables, cereals, fruit, pulses, proccessed food.
What are the functions of carbohydrates>
- Provides a source of energy
2. Aids the digestion of food
Explain the first function of carbohydrates?
• Carbohydrates which are consumed are
broken down into glucose to provide energy.
• Glucose which is not needed immediately is
converted into glycogen (a polysaccharide
stored in the muscles & liver in limited
amounts).
• Glycogen acts as short-term energy reserve in
the body when the blood is low in glucose.
Explain the second function of carbohydrates?
• A type of carbohydrates - Non-starch polysaccharides (NSP) or dietary fibre helps to
eliminate waste materials from our body and prevent constipation.
What are the Benefits of Non-Starch Polysaccharides (NSP)?
• more nutrients such as: — B-group vitamins — vitamin E — iron — magnesium • good source of insoluble dietary fibre • lower Glycemic Index (GI) compared to refined food — food with high GI causes the blood sugar level to rise
What are some ways to reduce sugar intake?
• Replace sweetened drinks e.g. soda and coke with plain water
• Choose fruit juices without added sugar.
• Reduce sugar in cake recipes (& bubble tea!)
• Choose food labelled as ‘no added sugar’ or ‘unsweetened’
,
‘less’ or
‘reduced sugar’
,
‘low in sugar’ or ‘sugar free’.
• Reduce spreads such as jam, kaya or marmalade on bread.
• Reduce intake of glazed doughnuts, chocolate, ice-cream and
candies.
What are the Effects of insufficient
carbohydrate intake?
Disruptions to our
normal body
functions
Extreme
tiredness
Loss of
concentration
Weight loss (in the long run)
What are the effects of excessive
carbohydrate intake?
Tooth decay and gum diseases Diabetes mellitus Weight gain
