1.2 Carbohydrates Flashcards
Two types of carbohydrates:
Simple carbs:
- mono,di and refined
- broken down/released quickly
- short bursts of energy
Complex carbs:
- poly, dietary fibre
- longer digestion
- provide greater energy levels
Three elements that makeup carbohydrates:
Oxygen, carbon and hydrogen.
Monosaccharides
Simple sugars
simplest forms of carbs
- cannot be broken down
sweet to taste
soluble in water
C6H1206
What are the monosaccharides?
Glucose
Fructose
- sweetest
- fruit “sugar”
Galactose
- formed from digestion of lactose
Disaccharides
Formed from 2 mono’s
Require greater digestion
soluble in water
C12H22011
Types of Disaccharides
Sucrose
Maltose
Lactose
Sucrose
Table sugar
Sucrose enzyme
glucose + fructose
Lactose
Milk sugar
Lactase enzyme
glucose + galactose
Maltose
Malt sugar
glucose x2
Hydrolysis - disaccharide digestion
- Disaccharide bond breaks
- Water molecule supplies H and OH necessary for the formation of two mono’s.
Condensation - disaccharide formation
A carbon on one mono bonds to oxygen on another, releasing a water molecule.
Most common polysaccharide types
Starch
-helps regulate & store energy
Glycogen
Cellulose
- not easily digested
- component of plants
Dietary fibre
Functions of carbohydrates
Source of energy - provide 16kJ/g of energy.
The brain and nervous system can only use glucose for energy.
Lack of glucose – headaches, fainting, nausea, constipation and inability to exercise, ketosis
How do carbohydrates release energy?
Release energy in the form of ATP via aerobic respiration within the cells.
36 ATP can be made during aerobic
Only 2 ATP are made in anaerobic
Fructose, galactose etc feed in at other points in the cellular respiration chain so aren’t converted directly to glucose, however are used in the same process.
What if carbohydrates are not available?
Stored fat is used in the cellular respiration cycle, to create energy.
The brain cannot directly use fatty acids for energy, some of these are converted to ketones, which can be used by your brain and nervous system.
Stored protein - last resort. Skeletal muscle is broken down to use as fuel. - muscle wasting.
Dietary fibre
Plays a large role in the healthy functioning of the digestive system.
Digested by bacteria in the large intestine.
Bacteria are then removed from faeces.
Less processing = ^ dietary fibre
A minimum of 25g-30g is required to be consumed daily.
Soluble and insoluble
Importance of dietary fibre
Slows down initial digestion
Allows for nutrients to be released into the body slowly, maximising their effects
Produces soft and bulky stools
Gives a feeling of fullness in the stomach
Prevents constipation, bowel cancer, haemorrhoids, diverticular disease
Reduces blood cholesterol levels
Prevents the absorption of harmful substances and aids the elimination from the body
Soluble Fibre
Soluble fibre dissolves in water to form a thick gel in your intestines, slowing digestion.
This can help stabilise blood glucose levels in people with diabetes and may help to lower LDL (bad) cholesterol levels.
Softens stools, preventing constipation.
Slows the movement of digested material, which increases absorption.
How does soluble lower BCL?
It binds to bile acids in the intestines and promotes their excretion. The liver filters cholesterol from the blood to produce bile acids, the more bile acids your body produces the lower your blood cholesterol levels are.
Soluble fibre sources
fruits and vegetables
dried beans and lentils
oats
Insoluble fibre
Cannot dissolve in water. It is the hard, scratchy outer skins and surfaces of roots, grains and seeds which are not as easily digested.
Insoluble fibre remains undigested, therefore adds bulk to your stools and helps to keep the bowels regular. It keeps the stomach fuller for longer.
Insoluble fibre attracts water, making stools softer so it can pass on with ease, preventing constipation.
Dietary fibre sources
whole grain breads and cereals
the outer skins of fruit and vegetables
nuts and seeds
raw lentil, kidney beans and chickpeas
Refined carbs (bad)
Plant based foods that have whole grain extracted during processing.
Two Types:
Sugars: sucrose, high fructose corn syrup and agave syrup.
Refined Grains: Foods that have had the fibre and most of the nutritional value of the food removed. The biggest source is white flour from refined wheat.
Digested quickly and have a high glycemic index
Artificial sweeteners
Synthetic sugar - lowering kJ
Can contribute to obesity, Type II Diabetes, Cardiovascular Disease and Cancer.
e.g. saccharin
