Carbohydrate Digestion And Absorption

Front 1

Digestion

Back 1

Chewing stimulates saliva production and mixes salivary amylase w/ food.

When carbs enter stomach, acidity of stomach juices halts the action of salivary amylase by denaturing it. Certain fibers, such as pectin, provide feeling of fullness and delay digestive activity by slowing down stomach emptying.

Most carb digestion takes place in small digestion. Pancreas secretes pancreatic amylase into small intestine, continuing digestion of starch.

Digestive enzymes break disaccharides into monosaccharides to be absorbed.

Humans lack digestive enzymes needed to break down oligosaccharides raffinose and stachyose.

In large intestine, some carbs remain intact as it enters. Bacteria ferment undigested carbs and produce gas plus a few short-chain fatty acids. Fatty acids might reduce risk of developing cancers.

Some fibers pass through large intestine unchanged and produce little gas. Fibers add to the stool weight and water content, making it easier to pass.

Front 2

Absorption

Back 2

Monosaccharides are absorbed in mucosal cells lining the small intestine.

Fructose is absorbed slower than glucose or galactose. In the villi, absorbed monosaccharides pass through the intestinal mucosal cells and enter bloodstream, which gets sent to liver by the portal vein, where galactose and fructose are converted into glucose or used for energy.

Liver stores and releases glucose as needed to maintain constant blood glucose levels.

Front 3

Normal Use of Glucose

Back 3

Major role: supply energy for the body.

Most cells can also burn fat for energy, however body needs some glucose to burn fat efficiently.

We store excess glucose as glycogen in liver and muscles.

Front 4

Using Glucose for Energy

Back 4

Glucose is primary fuel for most cells in body and the preferred fuel for the brain, red blood cells, nervous system, fetus, and placenta.

Small amount of glucose is needed even when fat is burned for energy.

Once glucose enters cells, metabolic reactions break it down into CO2 and water, releasing energy in a form that body can use.

Front 5

Storing Glucose as Glycogen

Back 5

Body assembles glucose into the long, branched chains of glycogen. Glycogen can be broken down quickly.

Muscle glycogen stores are used to fuel muscle activity and account for about 2/3 of the body's total glycogen stores.

Body can store about 2-24 hours, depending on activity level.

Front 6

Sparing Body Protein

Back 6

With no carbs, both proteins and fats can be used for energy.

If glycogen stores are depleted and glucose is not provided in the diet, the body must make its own glucose from protein to maintain blood levels and supply glucose to brain.

Front 7

Preventing Ketosis

Back 7

When no carbs are available, liver can't break down fat completely. Body then produces small compounds of ketone bodies. Most cells can use them for energy.

If ketone bodies are made more quickly than body uses them, can cause build up in blood and cause ketosis.

As concentration of ketone bodies increase, blood becomes too acidic. Body loses water as it excretes excess ketones in urine, and can cause dehydration.

Body needs 5-100 grams of carbs daily to avoid ketosis

Front 8

Regulating Blood Glucose Levels

Back 8

Body regulates blood glucose levels to maintain adequate supply of glucose for cells.

Low glucose levels: Person becomes shaky & weak.

High glucose levels: Person becomes sluggish and confused and have difficulty breathing.

When blood glucose levels rise after meal, insulin is released in blood. Insulin acts like a key, unlocking cells of the body and allowing glucose to enter and fuel them. As glucose enters cells to deliver energy or be stored as glycogen, blood glucose levels return to normal.

Front 9

Glucagon

Back 9

Hormone released when blood glucose level drops. It stimulates breakdown of glycogen stores to release glucose into blood.

Front 10

Epinephrine

Back 10

Hormone released in response to stress or sudden danger. It raises blood glucose levels to ready the body for fight or flight.

AKA adrenaline

Front 11

Glycemic Index

Back 11

Measure of the effect food on blood glucose levels.

It is ratio of blood glucose value after eating a food to the value after eating the same amount of white bread or glucose.

Front 12

Diabetes Mellitus

Back 12

Disease in which uptake of blood glucose by body cells is impaired, resulting in high glucose levels in blood and urine.

Type 1: caused by decreased pancreatic release of insulin.

Type 2: Target cells (such as fat and muscle cells) lose ability to respond normally to insulin.