Lecture 5 - The Carbohydrates: Sugars, Starches and Fibres Flashcards
Why are carbs important?
Good (and main) source of energy, especially for our nerve cells
What are the 3 Carbohydrates family?
Monosaccharides
Disaccharides
Polysaccharides
What are monosaccharides ?
Single sugars
-Glucose, Fructose, Galactose
What are Disaccharides?
Pairs of monosaccharides
-Maltose, Sucrose and lactose
What are Polysaccharides?
Large chains of monosaccharides
-Usually glucose molecules stuck together
What is the body prime source of energy?
Glucose which is a monosaccharide
-also the most abundant sugar we consume
What is the difference between Glucose, Fructose and Galactose?
They are all formed of the same items but all differ in their molecular conformations
What is the sweetest monosaccharide?
Fructose
-what makes honey sweet
Where would you find galactose?
It is not found naturally on its own, it is bound to lactose
-usually called milk sugar
How does galactose split into lactose?
Lactase splits the bond between glucose and galactose so you are ingesting both but separately
Where would you find the disaccharide maltose?
It is not found in nature, but we do consume products that have been malted.
-it is usually a byproduct of starch digestion
What is the disaccharide sucrose normally referred to as?
Table sugar
What 2 monosaccharides make up the 3 disaccharides?
Lactose: Glucose + Galactose
Maltose: Glucose + Glucose
Sucrose: Glucose + Fructose
How are disaccharides formed and broken down?
Formed through condensation reactions
Broken down through hydrolysis reactions
What are the 3 main polysaccharides of carbs?
Glycogen
Stach
Fibre
Which of the 3 polysaccharides are similar?
Glycogen and Starch
- glycogen is the storage form go glucose in animals
- Starch is the storage form of glucose in plants
Where is glycogen stored?
In the liver and in muscle cells as energy reserves
Chemically what does glycogen look like?
They are highly branched chains of glucose
Chemically what does starch look like?
Long, branched (not as branched as glycogen), and unbranched chains
Where do we find most starches in our diet?
Grains, legumes and root crops
What is starch broken down into?
Glucose
Chemically what does fibre look like?
Since it is the structural component of plants, their chains of glucose are arranged in stackable rows in a complex way that our body doesn’t have the machinery to break it down
What are the 2 forms of fibre?
Soluble and Insoluble
What can breakdown fibre in our bodies?
Gut bacteria
What are resistant starches?
Starches that act as fibres in which they have a hard time being broken down
What is amylose?
A straight chain of glucose stuck together
-can be broken down into glucose
What is amylopectin?
Is a chain of glucose branched out
-can be broken down into glucose
Where does the digestion of carbs start?
In the mouth with an enzyme
What is dietary fibre?
The non digestible part of plants (the outsides of plants, nuts seeds and husks)
What is functional fibre?
Carbohydrates with known health effects, which is extracted from plants and added to foods
What is pectin?
A functional fibre that comes naturally from fruit.
It absorbed water and makes it jelly
What is Psyllium
Also a functional fibre that is soluble and turns it into jelly as well
What is total fibre?
Functional + Dietary Fibre
What is it meant by soluble fibres?
Easily digested by gut bacteria
-Fibres are dissolved in water. Water is absorbed into the fibre forming this gel around it
Where would we find soluble fibres?
Citrus fruit, berries, oats and beans
Why is it important to have soluble fibres in your diet?
Reduces risk for type 2 diabetes, cardiovascular disease
Lowers blood cholesterol and glucose levels
What happens when soluble fibres are fermented?
They can produce short chain fatty acids
What are insoluble fibres?
Still absorb water, but do not form the gel around it
Where would we find insoluble fibres in our diet?
Whole grains, husk of grains and many veggies
Why is having insoluble fibres in our body good?
They are able to pull water into the digestive tract in order to soften faces
How much energy does fibre give us?
Not a lot of energy but it is extremely important for our gut health
What is something you have to be cautious about when consuming fibre?
You must stay hydrated because it is pulling water out of your body
Why do we need carbs?
fuel daily activity, exercise Helps preserve (spare) protein for other uses
What substance in our body relies solely on carbs as its energy source?
Red blood cells rely only on glucose for their energy supply
How much energy to you get from carbohydrates?
4kcal/ 1 gram
What activity requires carbs at more than 2/3 as its source of energy?
Intesene exercise, carbs will supply 2/3 or more of the total energy needed
Why do we need a sufficient intake of carbohydrates?
To prevent the production of ketones and an alternative energy source
Why are ketone bodies bad?
Excessive ketones can result in high blood acidity and ketoacidosis
- low pH damages tissue
- makes you feel sick and not want to eat
What does higher fibre foods do to the rate of digestion?
High fibre carbs slow down digestion and make you feel full longer
-carbs alone wont keep you full
How may fibre decrease blood cholesterol levels?
The liver makes bile using cholesterol. Bile is stored in the gallbladder. Bile is secreted into the intestine to air in the digestion of fat.
- in high fibre diets, the fibre (with gel) binds to bile and is excreted in feces. Results in less cholesterol being reabsorbed from the remaining bile
- in low fibre diets, less fibre is present to get rid of the bile. More cholesterol is remains which can be reabsorbed into the blood
Why is a high fibre diet important in terms of bowls?
Not enough fibre= more solid bowls which puts pressure on large intestinal walls which can cause pockets (diverticulosis).
High fibre draws in more water, making feces softer, decreasing pressure on the intestinal walls.
What is diverticulitis?
When the pockets caused by increased pressure in the large intestinal wall get inflamed
-get inflamed when feces is trapped in the pockets
How does digestion of carbohydrates start?
Mechanically in the mouth by chewing of food
Chemically in the mouth by the enzyme salivary amylase
Is there digestion of carbohydrates in the stomach?
No, there are no gastric enzymes to work on digesting the carbs
-too acidic for carb enzymes
How are carbs digested in the intestines?
In the duodenum,, the pancreas releases pancreatic amylase enzymes to break down carbs
-enzymes keep breaking down carbs into smaller carbs
Where are monosaccharides and disaccharides digested in the small intestine?
Enzymes secreted by the mucosal cells that line the small intestine
-maltase, sucrase, lactase
What is the fate of monosaccharides after they have been absorbed by the small intestinal cells?
Monosaccharides are absorbed and then enter the blood stream, to the liver to be converted into glucose to provide immediate energy
Where is excess glucose stored?
glucose is converted to glycogen and stored in the liver and muscles
What adds bulk to stool?
When excess fibre passes thought the small intestine undigested and enters the colon, which adds bulk to stools and is extreeted
What is lactose intolerance?
When you can not absorb the lactose disaccharide.
-Need help to digest and absorb the lactose
What is primary lactose intolerance?
When you stop making the enzyme that breaks down lactose
- this is linked to a gene
- as you get older your body stops making lactase (enzyme)
What is secondary lactose intolerance
Celiac Disease
- The lining of the intestines gets destroyed
- The lining is where the lactase enzyme is made
What are symptoms of lactose intolerance?
Bloating
Abdominal discomfort
Diarrhea
What are some of the causes of lactose intolerance?
Some foods Medication can cause the destruction of the lining Disease affected intestinal villi Prolonged diarrhea Malnutrition Genetics
What happens when we don’t frequently consume milk as adults?
We stop making lots of the lactase enzyme
-usually when you stop consuming dairy, you will stop making the enzyme
How do you treat lactose intolerance?
Lactose free products
Yogurts with bacteria
Hard cheese treated with bacteria
What happens when sell don’t need carbs (energy)?
If cells don’t need glucose, it is turned into glycogen and stored in the liver and muscles
How would you get glucose stored in the liver out?
Glycogen stores in the liver would have to be broken down into glucose via hydrolysis in order for glucose to be released into the blood.
How would you get glucose stored in muscle out?
Protein likes to keep their glucose for itself. Glycogen is broken down in the muscle via hydrolysis so that the glucose can be used by the muscle only.
How do you make glucose form protein?
Amino acids have to be deaminated. The backbone is used to produce glucose
-this would be classifies as gluconeogenesis
How are ketone bodies made from fat?
Fat can be a source of fuel when fat fragments join to form ketone bodies. Which is another energy source for the body, but not its favourite
-Ketone bodies cant be an energy source for brain and blood cells
What is insulin?
Hormones secreted into the blood by the pancreas to help regulate blood glucose levels
-stimulates liver to take up glucose and convert it into glycogen
What is glucagon?
Hormone secreted by the pancreas to signal the breakdown of glycogen to glucose for cells to take up
-also stimulates gluconeogenesis
What is the role of epinephrin and norepinephrine in blood glucose regulation?
Secreted by adrenal glands and nerve endings when blood glucose is low
- this increases glycogen breakdown by liver
- increases gluconeogenesis
What is the role of cortisol and growth hormone in blood glucose regulation?
Both secreted by the adrenal gland to act on liver, muscles and adipose tissue
- cortisol increases gluconeogenesis and decreases use of glucose by other organs
- growth hormone decreases glucose uptake by muscles and increases mobilization and use of fatty acids, increases livers output of glucose
How do we maintain constance blood glucose levels?
Having balanced meals at regular intervals and to have proper levels of hormones within the body
What is hypoglycaemia?
When blood sugar levels are too low
What is hyperglycaemia?
When blood sugar levels are too high
-results in type 1 and 2 diabetes
What is the difference between type 1 and type 2 diabetes?
T1: Autoimmune disease in younger people. Insulin is not produced
T2: chronic and developed over time. Usually poor diet choices and not enough exercise
What are the symptoms of Type 1 diabetes?
Frequent urination Unusual thirst Extreme hunger Unusual weightless extreme fatigue Irritability
What are the symptoms of Type 2 diabetes?
Any of type 1 + Frequent infection Blurred vision Cuts/bruises slow to heal Numbness in hands and feet
Which type of diabetes accounts for about 10% of all cases?
Type 1
-% decreasing because of the number of people getting type 2 now
What is the glycemic index?
Food classification based on glycemic response
-only looking at carbs
What is the glycemic response?
The speed of glucose absorption, blood glucose levels increasing and speed of return to normal levels
What can cause a lower glycemic index?
When you consume carbs with something else which causes a slower rise in blood sugar
Different processing of foods
What is a low glycemic diet good for?
Better for people with type 2
Higher in fibre
may reduce risk of heart disease, colon and prostate cancer
