W6 : Carbohydrates Flashcards
(32 cards)
What are the 3 main types of carbohydrates and how many calories per gram do they contain?
1) SImple sugars (mono/dissacharides)
- 4 cal/g
2) Complex carbs (polysaccharide – amylose in starch)
- 4 cal/g
3) Dietary fibre (polysaccharide – cellulose)
- 2 cal/g
Which simple sugar is the sweetest among all simple sugars?
Fructose
Name the 3 disscharides and name the monosaccharides they are made up of
- Maltose = glucose + glucose
- Sucrose = glucose + fructose
- Lactose = glucose + galactose
What are the 3 main polysaccharides that serves as storage / structural components in humans and plants?
- glycogen : storage form of glucose in muscle and liver cells
- Starch (amylose + amylopectin) : storage form of glucose in plants
- Cellulose: structural polysaccharide that gives strength to** plant cell walls**
What is meant by dietary fibres?
Part of plant material in the diet that resists enzymatic digestion, cannot be digested by humans.
What kinds of bonds are found in dietary fibre, such as cellulose?
β 1,4-glycosidic bonds which humans cannot digest since humans only have enzymes to hydrolyse α 1,4-glycosidic bonds
What are the 2 kinds of fibre and what are their functions?
- Soluble fibre – substrates for gut microbiome
- Insoluble fibre – absorbs remaining water and salts to add bulk to stool.
What are oligosacchardes and what is their function?
Sugars with** more than 2 **but < 10 monosaccharides linked together.
- oligosacchardes stimulate gut flora as they are food/substrates for gut microbes
What 2 kinds of sugars are used as substrates (food) for gut microflora?
- Soluble fibre
- Oligosaccharides
What are polysaccharides? List 3 examples.
- Sugars with many monosaccharides linked together
- Starch, glycogen, fibre
What is the definition of glycemic index?
A measure of how much blood glucose is raised by a 50g portion of carbohydrate containing food, compared to 50g of glucose or white bread.
- It is a number ranging from 0 to 100, with pure glucose given an arbitary value of 100
What is glycemic response?
How much blood glucose levels rise after consumption of a food (composite food) pr mea. (not restricted to only carbs)
What is the difference between glycemic index and glycemic response?
- Amount of carbs – glycemic index requires 50g of available carbs (same amount), while glycemic response does not care about how much carbs are available
- Macronutrient – glycemic index is concerned with how much blood glucose rise by with 50g of avail carbs, while glycemic response measures how much blood glucose rises after a meal , may include other macronutrients like protein and fat
What do high GI foods do to the blood glucose levels and hunger?
It causes a huge spike in blood glucose, and the response of insulin to the spike in glucose levels causes the blood glucose to decrease to more than baseline level of glucose
- this can increase hunger and increase snacking.
What values are :
1. Low glycemic index
2. Moderate glycemic index
3. High glycemic index
- Low GI : <= 55
- Moderate GI: 56-69
- High GI : >=70
After digestion in the small intestine, how are monosaccharides absorbed and where do they travel to?
- Monosaccharides enter the capillaries of intestinal villi
- Monosaccharides travel to liver via portal veinor to muscle cells for utilisation or storage of glucose as glycogen
why is glucose metabolism/homeostatis important?
Glucose is used as a key source of energy for certain cells – esp brain, nerve cells, red blood cells which only use glucose as source of energy and cannot use fat/protein as a source of energy, unlike muscle cells
Decribe carbohydrate digestion in the :
1. Mouth
2. Stomach
3. Small intestine
4. Large intestine
1) Mouth : where amylase breaks down starch
2) Stomach : Little carb digestion, but presence of fibre slows down digestion, extending the feeling of fullness
3) Small intestine : Most carb digestion takes place here
- Pancreatic amylase, specific disaccharide enzymes (lactase, sucrase,maltase)
- All carbs broken down into simple sugars
4) Large intestine : Soluble fibre digested by gut microbes
Is a high or low glycemic response desired?
Low glycemic response is desired as this means spike and drop in blood glucose may not be as sharp (so energy levels are maintained throughout the day)
What are 2 main differences between glycemic response of a person and glycemic index of a food?
- Glycemic index measures the relative change in blood glucose with a fixed portion of available carbohydrates (50g), while glycemic response measures the relative change in blood glucose in a person without specifying the amount of available carbohydrates.
- Measurement of GI is confined to carbohydrate containing food only, while glycemic response is not confined to only carbohydrate containing food.(can be a meal or composite food containing proteins etc)
What is meant gluconeogenesis?
Synthesis of glucose from non-carbohydrate sources
What are the 2 main hormones in glucose metabolism and their functions?
- Insulin : stimulates glucose absorption into cells and conversion to glycogen in liver and muscle cells when glucose concentration is high
- Glucagon : stimulates breakdown of glycogen (glycogenesis) in liver into glucose, releasing into bloodstream when blood glucose is low
What is the difference between glucose storage in the liver and in the muscles?
- Liver storage : glucose condenses to form glycogen and glucose is hydrolysed and transported to the rest of the body when needed
- Muscle storage : glucose is released for muscle use only
Glucose is stored in the ____ and ____ as ____
Liver, muscles, glycogen
