Carbohydrates Flashcards
Name three the most abundant carbohydrates? what is the difference between them?
Glucose and galactose are hexoses (5 carbon and oxygen in the ring+ 1 hanging) . Fructose are a pentose (4 carbons in the ring and oxygen +2 carbons hanging)
Name 3 different disaccharides and the composition of each.
- Lactose( glucose+galactose)
- Sucrose(fructose+glucose)
- Maltose(glucose-glucose)
Fructose is the sugar in…
Honey and fruits
In what products sucrose, maltose and lactose can be found?
Sucrose- table sugar( from sugar beet and cane)
Maltose ( beer,scotch)
Lactose ( milk)
What is glycosidic bond, explain different types
It is the bond , connecting 2 monosaccharides in disaccharides.
There are two types of them: alfa and beta.
Alfa is the 1 to 4 connection, in the same plain. We have the enzymes to digest them.
Beta- 1 to 4 connection, but the monosaccharides are in different plain. Only cows and other ruminants have the enzymes to digest them.
Where does the hydrolysis of disaccharides happen and the name of the enzymes.
On the brush border of the intestinal cells. Lactose-lactase, maltose-maltase,sucrose-sucrase.
Where are starches digested ?
In the mouth and in duodenum(in the lumen)
Name the types of polysaccharides and the difference
- Starch ( amylose:unbrached(1-4 bonds); Amylopectin:branched(1-4 and 1-6 bonds))
- Glycogen( like amylopectin ,but more branched)
- Cellulose
Why does the cooking time of vegetable vary?
The different proportion of amylopectin and amylose.
What is the fiber for humans?
Cellulose
Where is glycogen stored and why it is an inefficient source of energy? How do we use glycogen?
Glycogen stored in muscles and liver in animals.
Glycogen is hydrofillic and to store it , a lot of water is required. As a consequence, it becomes bulky and heavy.
It is the source of energy when we are fasting or when we need energy for the brain, muscle for fight response
Explain the digestion of polysaccharides(starch) in human body
In the mouth pH is 6.5. Salivary amylase starts to break the glycosidic bonds.
In the stomach pH is 2. Salivary amylase stops functioning. No starch digestion
In the duodenum pH is 7.5. In the pancreatic juice there is pancreatic amylase.Digesting of polysaccharides in disaccharides in the lumen.
Disaccharides are digested to monosaccharides on the brush border with the specific enzymes. Absorbed with the help of special carriers in the bloodstream.
Digestion of fiber in human body.Overview.
In mouth- mechanical digestion, mixes with saliva to moisten.
Stomach- not digested. Delays gastric emptying.
Small intestine- not digested. Delays absorption of other nutrients.
Large intestine- Most fiber intact.Bacterial enzymes digest fiber to short-chain fatty acids with gas(CH4,H2,CO2). Intestinal cells can use short-chain fatty acids as a source of energy. Fiber holds water.Regulates bowel activity. Binds bile,cholesterol and some minerals carrying them out of the body.
What happens to galactose and fructose in the liver?
They are converted to glucose.
Why lactose is not digested? Is it an allergy?
Lack of production of lactase on the brush border due to aging or disease. NOT an allergy. Majority people in the world have ;lactose intolerance.
What happens to undigested lactose?
It goes to the colon and the bacteria start fermenting it.As a result, gas formation -bloating,flatulence, lactic acid which irritant to the colon,hold water in the colon-cramps,diarrhea.
Why the lactose-free milk is sweeter?
Because the lactose is bitter, when it is already hydrolised, it gives a sweeter taste to the milk
Why soy beverages are the closest to the cow milk in nutritional facts. What is done to soy beverages in Canada?
The have practically the same content of protein, The must be fortified with substances ,found in cow milk(D,calcium,B12)
Glucose functions in metabolism
- Precursor for amino acids
- Converted to glycogen to store energy
- Converted to fat to store energy (more favorable)
- Oxidized for energy
- Prevent ketosis
What is the glucose level when we are fasting and after the meal?
5 mmol/l and 10mmol/l
What is the concentration of glucose in the brain?
2/3 of that in blood, for example when fasting 3 mmol/l
Why glucose is needed?
- Brain cells
- Blood cells
- Spermatogenesis
- Mammary gland
- Fetus
What can prolong hyperglycemia cause?
Damage to the organs
Explain the mechanism of homeostasis.
When we eat (postprandial or after meal state), there is a rise in blood glucose level. As a response, insulin is secreted by the pancreas. It stimulates the uptake of glucose in cells and glycogen storage in liver and muscle. Also, it encourages the excess glucose to be converted into fat.
Postabsorptive state(short-term fasting). Blood glucose decline. Low concentration of glucose stimulates the secretion of glucagon by the pancreas. Insulin stops secreting (negative feedback). Glucagon stimulates liver cells to break down glycogen and release glucose into the blood.
There is always a mixture of insulin and glucagon.
How much the percentage of diabetic people grew in 10 years in the US?
5% in 1997 to 8-10% in 2007
What is the forecast for diabetes mellitus and children born in 2000?
30% of American-born children born in 2000 forecast to develop Type 2 Diabetes (T2DM)
Explain what happens in T1DM(overview)
Insulin is no longer secreted, because the pancreas B cells are not functioning any more. ? Maybe it is due to the viral infection,which caused the autoimmune response. As the insulin is not secreted, glucose is not uptaken by the cells and the glucose level in the blood is very high
Explain what happens in T2DM(overview)
The problem in T2DM is peripheral cells. Muscles and cells stop paying attention to the glucose in the blood.the glucose is not up taken and its level remains high. More insulin secreted, but with no vain. Pancreas may stop functioning, because it worked too hard. Due to high blood level, organs are damaged (especially, eye tissue)
-Insulin binds to the receptor of the cell, but the inner response is very slow, so glucose ids not up taken
Why it is important to measure glucose and insulin level together?
Because the glucose level can be normal,but the insulin level very high. The first sign of diabetes.
Treatment to T1DM
Insulin shots (not pills, because a hormone-works in the blood+ the pH in the stomach will destroy the hormone)
- Low fat, low GI and fiber for slow glucose absorption.
- Balance the diet and exercise
Treatment to T2DM
- Low fat, low GI and fiber
- Weight loss, exercise, diet
Can T2DM be treated?
The wight loss.If the person loses 10% of his weight , the cells are more likely to absorb glucose
Older names for T1DM
Juvenile-onset diabetes
Insulin dependent diabetes mellitus (IDDM)
Older names for T2DM
Adult-onset diabetes
Non-insulin-dependent diabetes mellitus (NIDDM)
Associated conditions of T1DM and T2DM
T1DM- autoimmune disease,viral infections,inherited factors
T2DM-insulin resistance,insulin deficiency (relative to needs)
What is the proportion of T1DM to T2DM
5-10% T1DM and 90-95% T2DM
Explain in detail what happens in T1DM
As there is no insulin, cells have no glucose for energy. There are starting to oxidize proteins and lipids. As a result, lack of proteins to perform anabolic functions. Fat is converted to acetyl-CoA. Acetyl CoA enters TCA cycle (citric acid cycle). But TCA cycle requires carbohydrates as well, so it gets stuck. 3 acetyl-CoA form ketone bodies. Ketones can nourish the brain, but they accumulate fast and they are acids.-> ketoacidoses, which is potentially fatal
- Ketones in the breath( acetone breath)
- Ketones in blood (ketonemia) and ketones in urea (ketonuria)
- Hunger is not major thing in T1DM
Explain in details what happens in T2DM
The glucose does not go into the cell-> hyperglycemia. Damage of the cells due to high concentration of glucose.(kidney,eye and nerve damage). in T2DM some glucose enters the cells( and a consequence, we do not have high concentration of ketoses). But hunger signals are more dominant in T2DM than in T1DM . Overeating->problems with losing weight
Explain what happens in kidneys in T1DM and T2DM
25% of cardiac output. Nephrons filter the blood from the waste.
Normally: Blood goes to glomerulus and some of the fluid with dissolved substances(amino acids,glucose,waste) enters the tubule. Then the fluid and the substances needed returned back to the blood.
When the blood glucose is very high, glucose transporters cannot manage to bring all the glucose back->glucose leaks into the urine.
As the glucose is a highly hydrophobic molecule, it will take more fluid with itself-> people with hyperglycemia need to pee more-> constantly,thirsty-> hyperosmoral state, because they drink too much
The major complications of diabetes
Cardiovascular disease with increased risk of atherosclerosis
In Diabetes glucose level is always high. True or false?
False. Diabetes is the mix of sugar too low and sugar too high. Glucose does not know where to go.
The difference between glycemic index and glycemic load.
Glycemic index- the difference between fasting level of glucose and glucose level every hour after taking a serving size(50g) for three hours
Glycemic load combines glycemic index and amount of CHO (an adjustment to serving sizes)
The difference in response to high and low glycemic food
High GI-> high insulin secretion -> rapid uptake of glucose-> becoming hungry faster ( a chance of undershoot-fatigue)
Low GI->slowly digested (feeling of fullness for longer)->slow;y absorbed->low increase of glucose level in plasma-> “higher for longer”
What is the best and the worst food before the exam?
Low GI food (legumes and nuts) and foods containing fiber
High GI good (white bread, potatoes)
What is the recommended energy intake by CHO
45-65%( 1/2 to 2/3 of all energy)
Why there is no recommendations on glycemic index and UL sugar
No sufficient data
What is the suggestion for sugar intake?
6-9 tsp/day( 100-150 kcal/d) 5% of daily calories
The problem of excessive simple sugars intake
- Empty calories(4kcal/gram)
- High GI
- Excessive glucose is converted to saturated fat in adipose tissue
- Dental cavities( glucose is a substrate for bacteria, producing acids-> erosion of the enamel)
How the gingivitus and the cardiovascular disease connected?
Inflammation of the gums(gingivitus) is the window for the inflammation in the body-> risk to cardiovascular disease
Why water is enriched with fluoride ?
It makes the enamel more resistant to cavities
Artificial sweeteners- explain the concept
The taste buds sense the chemicals as sweet, but they do not have calories, because they are not digested. They are much sweeter than sugar, so you need less
Aspartame
- Many time sweeter (200x)
- Metabolized to aspartate,phenylalanine,CO2 through methanol
- Warning for PKU(amino acid metabolism disease)
- Limited self-life(6 month) and heat labile
Neotame
- Improved version of aspartame
- More stable than aspartame
- Not metabolized to phenylalanine
Acesulfame-K
- More sweet (200x)
- Heat stable, long shelf life
- Synergistic (can work with others). As a result, less sweetener could be needed
Splenda
- More sweet (800x)
- Instead of three OH groups in glucose- 3Cl ( receptors recognize it as sweet, but it is not a substrate to sucrase, so it is not absorbed
- Not digested, not absorbed
- Heat stable
RebA
- From stevia
- 200 x sweeter
Sugar alcohols: names, advantages
- Xylitol,mannitol,sorbitol
- Not fermentable (bacteria cannot digest it, so they are used in the gum)
- Slowly absorbed
- About 2 kcal/g
Does sugar-free means without calories?
No
Where can you find insoluble fiber?
- Cell walls (structure)
- Cellulose(lignin hemicellulose)
- Fibrous veggies (celery), wheat bran
Where can you find soluble fiber?
- Cement,glue of plants (thickening agent)
- Pectin,gums,mucilages
- Beans, legumes,nuts,fruits(especially, strawberries and apples),oats(whole oats,whole gran cheerios),barley (ячмень)
- Additives- carageenan (from sea weed), guar gum (emalsifier), pectin in jams
The action of fiber in the stomach
- Soluble (s) (viscosity)- make the chyme thicker-> distribute the food more equally in the stomach
- Insoluble(I) -bulk- ( hold water)
These two characteristics delay gastric emptying, fullness sensation,satiety
The action of fiber in the small intestine
- Not digested by our enzymes
- Slows absorption-better glycemic index
Soluble-binds yo bile acids and as the result enterohepatic circulatio goes down, fat,cholesterol and fat soluble vitamins absorption reduces, cholesterol level decreases
Insoluble- binds cations
Phytes (anion that bins the cation) decreases, Fe, Ca,Zn are not absorbed
Why you cannot eat meat with wheat bread
Iron will not b absorbed , because of insoluble fiber
Explain how soluble fiber interferes in enterohepathic circulation?
Usually, bile is recycled after being used.( with the special carriers in epithelial intestinal walls). Bile acids are digested a little bit and they can be dangerous for the colon.
Bile is bound to soluble fiber, so bile is not reabsorbed , but excreted. Liver has to produce more bile and it uses the cholesterol.( the only way to use the cholesterol in the body). It reduces the risk of cardiovascular disease
Action of fiber in the colon
-The fiber increases GI motility (peristalsis) and speeds up transit
-Fiber attracts water, so the bulk will become softer
-All the soluble fiber is the substrate for colon bacteria.. Bacteria can digest the fiber. As the result - production of gas( CH4,CO2,H2), short chain fatty acids(acetate-2 carbon, proponate-3,butyrate-4). Energy for colonocytes. Protection of mucus layer by lowering pH
Protects colon by binding bile acids and toxins
Does the fiber has no nutritional value?
It is not strictly true, because the bacteria make short chain fatty acids.Colon cells can use them for energy.
Perhaps, if CHO has 4 kcal/g, so fiber has 2 kcal/g
What is the recommendation for fiber?
- 38 g for men and 25 g for women ( current intake 10-15g)
- Eat ore whole foods, but not the juices
- There is no UL, because it depends on person and you will set up the amount needed, by increasing gradually the amount of fiber( flaturence, etc.)
Health effects of low GI food and Fibre
- Weight control (low fat,satiety,bulk)
- Heart disease (low in saturated fat, high in phytochemicals,lower cholesterol)
- Cancer (lower colon cancer risk-diluting,transit time,binding toxins, lower pH phytochemicals,vitamins)
- Diabetes (glycemic control,weight control)
- GI health
