Carbohydrates in Nutrition Flashcards
Are carbohydrates essential in the diet?
No
What is the average persons carbohydrate consumption composed of?
Monosaccharides = glucose and fructose Disaccharides = sucrose and lactose Polysaccharides = starch and glycogen
What is sucrose composed of?
Glucose and fructose
What is lactose composed of?
Glucose and galactose
What is maltose composed of?
Glucose and glucose
What is the average daily intake of carbohydrates?
300g
What is the largest carbohydrate component of the diet?
Starch
What two forms is starch found in?
Amylose and amylopection
What is the structure of amylose?
Glucose monomers joined by alpha 1,4 glycosidic bonds
Can amylose be tightly packed?
Yes
Is amylose readily digested?
No
What is the structure of amylopectin?
Glucose monomers joined by alpha 1,4 and alpha 1,6 glycosidic bonds
Can amylopectin be tightly packed?
No
Is amylopectin readily digested and why?
Yes - because enzymes can permeate the molecule easily due to it not being tightly packed
What other molecule is the amylopectin structurally similar to?
Glycogen
What does the digestion of a carbohydrate by alpha amylase produce?
Short chains of glucose NOT glucose monomers
What enzyme is found in the mouth and where is it secreted from?
Amylase
Secreted in saliva from salivary glands
What enzyme is found in the duodenum and where is it secreted from?
Secondary alpha amylase
Secreted from the pancrease due to stimulation from absorbed glucose
What enzymes are found in the intestine and what do they produce?
Maltase
Sucrase
Lactase
Produce single glucose monomers which can be absorbed into the blood
What does maltase break down?
Maltose into glucose and glucose
What does sucrase break down?
Sucrose into glucose and fructose
What does lactase break down?
Lactose into glucose and galactose
Why might a person be intolerant to a certain sugar?
If they do not possess the enzyme required to break down that sugar
What sugars can a human body not break down?
Stachyose
Raffinose
What is dietary fibre?
The edible part of plants that are not broken down in the small intestine
What is crude fibre?
Residues of plant food left after extraction by dilute acid and alkalis
What happens when food reaches the colon?
We cannot use it however the bacteria in our colon metabolise it and we can use the byproducts = symbiotic relationship
How is glucose transported into our cells?
Sodium glucose linked transporter I
- transports sodium and glucose into cells
- driven by the high concentration of sodium outside cells (as a result of sodium potassium pumps)
How is fructose transported into our cells?
Via facilitated diffusion through the Glut - 5 transporter
What molecules does Glut - 2 transport and where does it transport them?
Glucose
Galactose
Fructose
Out of the cell and into the blood
What is the glycemic index?
A method of ranking foods based on their predicted blood glucose response compared to the same gram weight of pure glucose
How is the glycemic index produced?
Subjects are tested 5 times
- Subjects are given 50g of pure glucose three times
- Subjects are given 50g of the food containing available carbohydrates twice
- Repeated with 10 subjects for every food
Why is the glycemic index not definitively correct?
- Foods are tested on their own (other foods in a meal will affect how readily individual foods are digested)
- Subjects are always tested in the morning (digestion varies depending on time and a persons fasting state)
- Fructose does not count
- Other macronutrients are not taken into account
- All subjects are young, white, healthy individuals
What does a high GI value indicate?
A rapid glucose peak and a high insulin peak
How do you calculate glycemic load?
(amount of food carbohydrate x GI) / 100
What are the advantages of using the glycemic load?
Takes into account portion size and carbohydrate content
