Carbohydrate Metabolism Flashcards
Where is the secretion done?
Multiple digestive secretions in the GI tract
Explain the path of the bolus during swallowing.
Epiglottis closes over larynx, blocking entrance to lungs via the trachea
The bolus goes down the pharyx, to the esophagus, to the stomach
Explain what happens when choking.
Food lodged in the trachea blocks the passage of air
Why do J-thrusts work to get food out?
Increase intrathoracic pressure
What is dysphagia?
Difficulty swallowing on a chronic basis (epiglottis coordination)
What does GERD stand for?
Gastro-Esophageal Reflux Disease
What causes GERD?
Strong acid from the stomach goes up and damages the lining of the esophagus and creates GERD
How can we treat GERD?
Drugs, surgery
Name the 2 drugs for GERD.
Anti-acids (neutralize), proton-pump inhibitor (decrease production of HCl)
What causes ulcers?
- Acid eating away at the lining of the stomach
- H-pylori
What recent discovery about ulcers made headline news?
H-pylori found in acid environment of stomach, eats away and makes lining vulnerable –> H-pylori antibiotic= CURE
How long does food stay in the mouth? Stomach? Small intestine? Colon? Assuming 24 h transit time.
Mouth: less than a minute
Stomach: 1-2h
Small intestine: 7-8h
Colon: 12-14h
What are the recommendations for carbohydrates?
- Variety of grains, half of them whole
- Limit your sugar
What do plants make out of what during photosynthesis?
Plants make glucose out of inorganic substances
Which monosaccharides have 6 carbon atoms? Which has 5?
6: Glucose, Galactose
5: Fructose
What is sucrose made of?
Fructose-Glucose
What is maltose made of?
Glucose-Glucose
What is lactose made of?
Glucose-Galactose
Which carb is the only animal-based on?
Lactose
What is a glycosidic bond?
Joins a carbohydrate to another group (could be carb or not)
How are glycosidic bonds formed? Broken?
Formed: dehydration
Broken: hydrolysis
Which polysaccharides are alpha? Which are beta?
Alpha: starch, glycogen
Beta: cellulose
What is starch made of?
Amylose + Amylopectin
Which characteristics of polysaccharides influences the characteristics of food?
Amount of amylose and amylopectin
Which polysaccharides is plant form?
Starch
Which polysaccharides is animal form?
Glycogen
Where is glycogen stored? What is it stored with?
Liver, H2O
What is cellulose produced by?
Plants
Why can’t we digest cellulose?
Our GI tract cannot digest the beta
Describe how starch is digested in the mouth.
Saliva moistens the bond
Amylase transforms starch into maltose + polysaccharides
Describe how starch is digested in the stomach.
Acid inactivates salivary enzyme, halts starch digestion
Describe how starch is digested in the pancreas.
Produces an amylase, released pancreatic duct –> small intestine
Pancreatic amylase transforms starch into small polysaccharides and maltose
Describe how starch is digested in the small intestine.
Disaccharide enzymes on the surface of the small intestinal cells hydrolyze disaccharides into monosaccharides
Intestinal cells absorb these monosaccharides
Describe how fibre is digested in the mouth.
Mechanical action crushes fibre + moistens it
Describe how fibre is digested in the stomach.
Fibre not digested, delays gastric emptying
Describe how fibre is digested in the small intestine.
Fibre not digested, delays absorption of other nutrients
Describe how fibre is digested in the large intestine.
Most fibre passes intact through the digestive tract to the large intestine. Here, bacterial enzymes digest fibre into short-chain fatty acids and gas
Name some functions of fibre.
Holds water, regulates bowel activity, binds to substances such as bile, cholesterol, and some minerals carrying them out of the body
- Water-holding
- Ion binding
- Fermentability
Why can’t certain people digest lactose?
No lactase on their brush border
What does lactose intolerance cause?
Nausea, diarrhea, cramps, bloating, flatulance
Name some treatment options for lactose intolerance
Dilute milk, lactose predigested foods (yoghurt, cheese), lactose reduced milks, lactaid pills
What do we need to look out for if we eliminate milk products?
Calcium and vitamin D
Name the 5 glucose functions in metabolism.
1) Precursor for amino acids
2) Converted to glycogen to store energy
3) Converted to fat to store energy
4) Oxidized for energy
5) Prevent ketosis
Why is glucose homeostasis important?
Needed for brain cells, blood cells, spermatogenesis, mammary gland, fetus, etc.
What is hypoglycemia? Hyperglycemia?
Hypo: low blood sugar
Hyper: high blood sugar
What should fasting glucose levels be? What shouldn’t it pass?
5 mmol/L, 10 mmol/L
What happens to glucose after eating (fed state)?
1) Blood sugar increases
2) Which stimulates the pancreas to release insulin into the bloodstream
3) Which stimulates the uptake of glucose into cells and storage as glycogen in the liver and muscles. Also stimulates the conversion of excess glucose into fat
Which gland is both an endocrine and exocrine gland?
Pancreas
What happens to glucose after absorbing?
1) Cells use glucose, blood sugar decreases
2) Which stimulates the pancreas to release glucagon into the bloodstream
3) Which stimulates liver cells to break down glycogen and release glucose into the blood
4) Blood glucose increases
How much did diabetes rise from 1997 to 2007?
6% to over 10%
What is the official name for diabetes? What does it mean?
Diabetes Mellitus, sweet (urine is sweet)
What causes type 1 diabetes?
Pancreas stops producing insulin by B-cells (probably an autoimmune disease)
How are glucose levels for type 1?
High blood glucose
What % of cases is type I diabetes?
5-10%
What is the treatment for type 1 diabetes?
- Exogenous insulin
- Diet (low fat, low GI CHOS, and ++ fibre)
- Balance diet + exercise
Why can’t you take a pill for type 1 diabetes?
Insulin is a protein, no pill since it would just be digested
What causes type 2 diabetes?
Cells are not sensitive to insulin (exhausted pancreas)
How are plasma glucose and insulin levels?
Normal plasma glucose, high insulin
What % of cases is type 2 diabetes?
90-95%
What type of treatment for type 2 diabetes?
Low fat, low GI CHOs and fibre
Weight loss, exercise, diet (type 2 can be reversible)
What is the function of our kidneys?
Filtrate
Where does the blood go in the kidneys? What happens?
Blood flows into the glomerulus, small molecules go out, some are absorbed into the tubule
What is the second step during kidney filtration?
Reabsorption of glucose and amino acids
What is excreted during kidney filtration?
Waste material
Is there glucose in urine? Can certain conditions affect that?
Not usually
Someone with hyperglycemia (> 10mmol/L) will have glucose in urine
How do we calculate GI?
GI (%) = (glycemic response to 50 g of food/glycemic response to 50 g of glucose) x 100%
What does GI measure?
Measures blood sugar response to eating a food in relation to a standard
What does low GI mean?
Glucose digested slowly, low insulin response
What nutrient usually predict low GI?
+ Dietary fibre
Name a food group that is low GI.
Legumes
What is glycemic load?
Glycemic index and amount of CHO
Name 2 problems for the DRI summary of CHO.
- Not based on glycemic index
- No UL for sugar
How much sugar should we have daily?
6-9 tsp/day = 100-150 kcal/d
Name 2 problems associated with high sugar.
High GI
Dental cavities
High blood sugar
What does excess glucose get converted to?
Glycogen, which liver converts into saturated fat
Define a cavity.
Erosion of the enamel
Define gingivitis. What is it an indicator of?
Inflammation of the gum
Indicator of inflammatory stress in the body
How do cavities form? What do they require?
Fermentable CHO by bacteria in the mouth, which produce acids –> cavities
Fermentable sugar alcohols
How are we less susceptible to cavities?
Brushing your teeth, fluoride treatment
What is a problem of adding fluoride to water?
We’re fluoridating all other water uses
How do artificial sweeteners compare to sugar?
+++ sweet
Name two artificial sweeteners from the past.
Saccharin and Cyclamate
Can aspartame be digested?
Yes
Can splenda be digested? What happens?
No, gets eliminated through urine, effects on environment (?)
What are the downsides of aspartame?
CANNOT be heated
Warning for PKU
What is PKU? What is treatment?
- phenylalanine isn’t metabolized, increase is toxic, HAS to be limited through diet, only during development (teens)
- pregnant women too
What is another word for splenda?
sucralose
Are sugar replacers fermentable?
No
How many kcals/g for sugar replacers?
2kcal/g
Are sugar replacers slowly absorbed?
Yes
Does sugar free mean no calorie?
no
What are the 2 types of dietary fibre?
Insoluble and soluble
What makes up insoluble fibre?
Fibrous veg, wheat bran
What makes up soluble fibre?
Beans, legumes, oat bran, nuts, fruits
What does soluble fibre do in the stomach?
Viscosity
What does insoluble fibre do in the stomach?
Bulk
What do both fibres do in the stomach?
- delays gastric emptying
- fullness, sensation, satiety
What does fibre do in our small intestine?
Slows absorption
Why does fibre control glycemic?
since it slows absorption
What does insoluble fibre bind to? What does soluble bind to?
Insoluble binds to cations
Soluble binds to bile acids
Describe the enterohepatic circulation of someone with a regular diet.
bile acids reabsorped to liver, biliary secretion from liver
Describe the enterohepatic circulation of someone with a high-fibre diet.
less bile acids reabsorbed by liver since fibre bound to cholesterol and bile acids
so liver increases the synthesis of bile acids from cholesterol, LESS CHOLESTEROL
Name the 4 functions of fibre in the colon
Increases GI motility
Attracts water and bulk
Fermented by intestinal bacteria
Binds bile acids and toxins
What can attracting H2O lead to in the colon (by fibre)?
Constipation, diverticular disease, hemorrhoids
What can fermentation in the colon lead to (by fibre)?
increase in gas
How does fibre protect the colon?
Binds bile acids and toxins
Define diverticulitis
Inflammation of diverticula
Fecal contents trapped, increase in pressure, inflammation in diverticula, infection
What is the treatment for diverticulitis?
Surgery and FIBRE
What is the current fibre intake?
10-15 g/day
What is the recommendation for fibre for men? Women?
Men: 38 g/d
Women: 25 g/d
Why is there no RDA for fibre? What is used instead?
Not enough research, AI
Why is there no UL for fibre?
Not worthwhile, intake much lower than AI
Are there any calories in fibre?
1.5 to 2.5 kcalories per gram
What are the main sources of dietary fibre?
- 1/2 fruits and veg
- 1/2 grains, legumes, seeds
Which food groups pack a fibre punch?
Legumes and seeds
Name 5 positive health effects of fibre.
- Weight control
- Heart disease
- Cancer
- Diabetes
- GI Health
If the carbohydrate content of the diet is insufficient to meet the body’s need for glucose, what can be converted to glucose?
Amino Acids
Which polysaccharide is food not a significant source of?
Glycogen
Compare soluble vs. insoluble fibre.
Soluble: dissolve in water, form gels (viscous), and are easily digested by bacteria in the colon (fermentable)
Insoluble: do not dissolve in water, do not form gels (non- viscous), and are less readily fermented
Compare the health benefits of insoluble vs. soluble fibre.
Soluble: protecting against heart disease and diabetes by lowering blood cholesterol and glucose levels
Insoluble: promote bowel movements, alleviate constipation, and prevent diverticular disease.
