3.1 carbohydrate
TRANSCRIPT
CHAPTER OUTCOMES
At the end of this chapter, students should be able to:-
a) Explain briefly about classification, function, digestion of carbohydrate
b) Describe recommeded intake and related diseases for carbohydrate
Carbohydrates are primary fuel source for certaincells such as nervous system, red blood cells andbrain cells.
1 gram of carbohydrates yields about 4kcal of energy
We obtain about 50% - 60% of our energy intake fromcarbohydrates (maybe higher % in the developingworld)
COMPOSITION Composed of carbon, hydrogen, oxygen in the ratio
1:2:1 respectively: (CH2O)
Plants use CO2, H2O and energy (from the sun) toproduce the CH2O we eat.
The process is called photosynthesis
MONOSACCHARIDE
Also known as simple carbohydrates / simple sugars
Consist of 3 monosaccharide (single sugar) such as:
a) Glucose
b) Fructose
c) Galactose
1. GLUCOSE
Major monosaccharides in body
Also known as dextrose and blood sugar
Essential energy source for all body activities
Glucose in the body exist in ring form
2. FRUCTOSE
Major monosaccharides in diet
Also known as levulose
Sweetest among the sugars
Same chemical formula with glucose but differentstructure
Arrangement of the atoms stimulates the taste buds
Abundant in fruit, honey, corn syrup
Used in the production of soft drinks, confectionaries,frozen foods
3. GALACTOSE
Not found free in nature
Always combines with glucose to form lactose
Available in milk and dairy products
DISACCHARIDE Double sugars formed by chemical bonding of two
monosaccharide
2 types of bonding:a) alpha glycosidic bond: can be digested by human
intestinal enzymesb) beta glycosidic bond: cannot be digested by human
intestinal enzymes
3 types of disaccharidesa) Maltose = glucose + glucoseb) Sucrose = glucose + fructosec) Lactose = glucose + galactose
1. MALTOSE Mixture of: Glucose + Glucose
Link by alpha glycosidic bond
Situation where starch breakdown into maltose:
a) CH2O digestion
b) Fermentation process -> alcohol
Source: Grains
2. SUCROSE Mixture of: Glucose + Fructose
Link by alpha glycosidic bond
Also known as table sugar
Sucrose refine from juice of sugarcane or sugar beet
Sources: from plant only – honey, maple syrup,sugarcane
3. LACTOSE Mixture of: Glucose + Galactose
Link by Beta glycosidic bond
Also known as milk sugar
Source: milk, milk products
POLYSACCHARIDE Also known as complex carbohydrate
Mainly consist of:
a) Starch
b) Glycogen
c) Fibers (indigestible polysaccharide)
1. STARCH
Storage form of energy in plants
Long, branch (amylopectin) andunbranch (amylose) chain of glucosemolecules
All starchy food derives from plant
Source: rice, corn, barley, oats, legumesand tubers
2. GLYCOGEN Storage form of energy in animal body– temporary storage in muscle andliver
Glucose molecules in glycogenstructure linked in highly branchedchains that permits rapid hydrolysis
More branches – more sites forenzyme reaction quickly brokendown when needed
Limited sources in food becauseanimal muscles rapidly hydrolyze afterslaughter
3. FIBERS(INDIGESTABLE POLYSACCHARIDES)
Provide structure in stem, trunks, roots, leaves and skin of plants
Polysaccharide cannot be broken down by digestive enzyme
a) Lignin – woody parts in carrot, seeds in strawberry
b) Cellulose – primary constituents of plant cell wall
c) Hemicelluloses – main constituents of cereal fibers
d) Pectin – commonly found in vegetables and fruits, forms gelin water, control texture and consistency, thicken jelly
e) Gums – used as additives
f) Mucilage – used as stabilisers
1. Yielding energy
2. Sparing protein from use as an energysource
3. Preventing ketosis (pronounce : kitousis)
4. Imparting flavor and sweetness to foods
5. Maintaining health of large intestine
Storing glucose as glycogen
a) Muscle glycogen – fuel muscle activity
b) Liver glycogen – to maintain blood glucose
c) Glycogen can be quickly release for energy as needed
d) Glycogen will last from a few hours to one day depending on activity level
Using glucose for energy
a) primary fuel for brain, RBC, nervous system, fetus and placenta
b) Need to metabolize fat completely
c) Glucose in blood used by body cell (undergo metabolic reaction) - produce energy
HORMONES RELEASE FROM PANCREASE Insulin
a) Produced by beta cell in pancreas
b) Functions during the rising glucose level in blood after ameal
i. Promote the storage of glucose as glycogen in liver andmuscle
ii. Stimulate protein synthesis and increase lipid synthesis
iii. Remove glucose from the blood so decreasing bloodglucose levels to the normal stage
Glucagon
a) Made in alpha cell in pancreas
b) Stimulates the breakdown of liver glycogen so glucosewere released to the bloodstream
c) It also help restore blood glucose to normal concentration
BLOOD GLUCOSE LEVEL Normal condition
Blood glucose level is about 70 – 110mg/dl (<6.1 mmol/l )
Hyperglycemia
Blood glucose level is exceeds 170mg/dl (>7 mmol/l )
Having high blood glucose
Begin to spill over into the urine
Hypoglycemia
Blood glucose level falls below 40 – 50mg/dl (<4 mmol/l )
Having low blood glucose
Symptom: nervous, hungry, headache
RECOMMENDED INTAKE OF CARBOHYDRATE
No Recommended Daily Allowance (RDA)
Recommended nutriens intake (RNI)
a) Total CHO: 55 – 70% of daily calories
b) Sugars: <10% of total energy
c) Dietary fibre: 20-30g per day
2000kcal = daily CHO intake ~ 275 to 300g
SOURCE OF CARBOHYDRATE
Sugar, honey, jam, jellies, fruits, baked potato: greatest % of kcal from CHO
Rice, bread, corn flakes, noodles: 75% of kcal/energy as CHO
Peas, broccoli, oatmeal, dry beans, legumes, fries, skim milk: moderate
Chocolate, whole milk: 30% - 40% of kcal as CHO (more fat)
Essentially no CHO: beef, chicken, fish, vegetable oil, butter, margarine.
LACTOSE INTOLERANCE
A condition that results from inability to digest the milk sugar lactose.
It can normally occur when (to normal people):-
a) Large amount of lactose is consumed more than the available lactase can handle
b) Lactose molecule remain in the intestine undigested
c) Undigested lactose becomes food for intestinal bacteria
d) Bacteria multiply and produce irritating acid and gas
e) It cause bloating, abdominal discomfort and diarrhea.
Natural causes:
a) Lactase activity commonly declines with age
b) Lactase deficiency may also develop when theintestinal villi are damaged by disease, certainmedicine, prolonged diarrhea or malnutrition.
c) Lactose malabsorption may be temporary orpermanent.
d) An infant is born with a lactase deficiency
Overcome lactose intolerance:
a) Remove all milk products from the diet – but it canlead to nutrient deficiencies (calcium, vitamin Dand riboflavin).
b) Read labels and avoid foods that include milk, milksolid, whey (milk liquid) and casein (milk protein).
c) Need to check all medications - because 20percent of prescription drugs contain lactose as afiller
d) Increase intake of milk product gradually
e) Consume fermented milk products such as yogurt
f) Consume commercially prepared milk productsthat have been treated with an enzyme that breaksdown the lactose.
DIABETES
Definition:
a) A metabolic disorder characterized by:-
i. Elevated blood glucose
ii. Altered energy metabolism
b) It is caused by:-
i. Defective insulin action
ii. Defective insulin secretion
iii. Both combination
Types of diabetesa) Type 1
i. Failure of insulin production
ii. Dependent on insulin injection because insulinnot produce by pancreas
iii. Usually happen to children and adolescent
b) Type 2
i. Not dependent on insulin injection
ii. Insufficient/inactivate insulin produced by thepancreas
iii. Usually happens to people 40 years and above,heredity and obese is the main contributor
PAUSE TO PONDER…
a) Please explain briefly about classification, function,digestion of carbohydrate
b) Try to describe recommeded intake and relateddiseases for carbohydrate