NUTR1023 Lecture Notes - Lecture 4: Blood Sugar, Small Intestine, Galactose
Module 4 - Macronutrients
Lecture 1 - Carbohydrates !
Functions of carbohydrates !
•provide energy (especially high intensity exercise)!
•Regulate fat and protein metabolism (because body will always use carbohydrates before fat
and protein)!
•Primary energy source for the nervous system !
•Synthesised into muscle and liver glycogen for storage !
•Sources: grains, fruit, vegetables, milk, sweets !
Carbohydrates in some common foods!
•40 grams - 1 can of Coke!
•15 grams - White bread!
•13 grams - Glass of milk!
•20 grams - banana !
Chemistry of carbohydrates!
Monosaccharides
•the most simplest carbohydrate unit !
•Examples are glucose, fructose, galactose!
Disaccharides
•two monosaccharides joined together!
•sucrose: glucose + fructose !
•Lactose: glucose + galactose !
•Maltose: glucose + glucose!
Condensation - links two monosaccharides together!
Hydrolysis - breaks a disaccharide into two !
Polysaccharides
Objectives
•List the functions of carbohydrates,#proteins and fats#in the body.!
•Describe how carbohydrates,#proteins and fats are digested and absorbed.!
•Describe the chemical structures and classifications of carbohydrates,#proteins and fats.!
•List some rich food sources of carbohydrates,#proteins and fats.!
•Briefly describe the effect of manipulating dietary#macronutrient#intake on body weight and
other risk factors for chronic disease.!
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•long chains of sugar units !
•Glycogen: used to store glucose and is a large branched molecule !
•Starch (amylopectin): branched molecules are absorbed and digested easily !
•Starch (amylose): unbranched and straight and so it takes longer for glucose to enter the blood!
Different types of carbohydrates have different sweetness depending on chemical structure!
!
Fibre!
•glucose molecules that we cannot digest or absorb !
•Fibre is no nutritional value but the bulk helps to move contents throughout the digestive system !
•It can bind with potential dangerous substances in the large intestine and remove them from
body!
Cellulose !
•type of fibre !
•Cellulose and starch are very similar in structure but the bonds of starch can be broken down !
Digestion of carbohydrates !
•Most of the digestion happens in the small intestine through digestive enzymes that break the
carbs down !
•Small intestine absorbs the monosaccharides !
•The monosaccharides then go to the liver !
•In the liver, fructose and galactose are converted into glucose !
•Liver releases glucose into blood stream !
•In the blood stream, the amount of glucose is regulated by two hormones secreted from the
pancreas !
•Insulin: removes glucose from the blood and puts it back into the cells !
•Glucagon: stimulates liver to release the glucose and put it into the blood stream !
It is important to regulate the level of blood glucose
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•Too low glucose in blood will not give us energy to get to the brain or the cells !
•Too high glucose in blood (especially over long time) damages blood vessels and other
tissues !
The glycemic index!
A way to rank carbohydrate foods according to how quickly the carbohydrate is digested and
absorbed and appears in our blood stream.
•the glycemic index is ranked from 0-100 !
•A glycemic index of:!
•<55 : low !
•56-69: moderate !
•>70: high !
•low GI food does not mean it is good for us !
•Many factors influence GI of the food (protein/fat/fibre in that food and also which other food we
eat it with) !
How it is measured
•the blood glucose level of a reference food (which is 50 grams of glucose) is compared to the
blood glucose level of a food containing 50 grams of carbohydrate. !
!
The area under the test food is only 40%
of the area under the reference food. !
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Document Summary
Carbohydrates in some common foods: 40 grams - 1 can of coke, 15 grams - white bread, 13 grams - glass of milk, 20 grams - banana. Monosaccharides: the most simplest carbohydrate unit, examples are glucose, fructose, galactose. Disaccharides: two monosaccharides joined together, sucrose: glucose + fructose, lactose: glucose + galactose, maltose: glucose + glucose. Di erent types of carbohydrates have di erent sweetness depending on chemical structure. Cellulose: type of bre, cellulose and starch are very similar in structure but the bonds of starch can be broken down. How it is measured: the blood glucose level of a reference food (which is 50 grams of glucose) is compared to the blood glucose level of a food containing 50 grams of carbohydrate. The area under the test food is only 40% of the area under the reference food. Protein in the body: 16% - body weight, 43% - body protein (skeletal muscle, 26% - organs, (15%)rest - skin and blood.
