Digestion of Carbohydrates

Question 1

Metabolism

Answer 1

Anabolism + catabolism

Question 2

Digestion is a process that breaks down large food molecules, such as __, ___, and ___ into smaller ones, __, __, and __.

Answer 2

Carbohydrates, proteins, and lipids

Monosaccharides, amino acids, and fatty acids

Question 3

Digestive tract pathway

Answer 3

Mouth
Esophagus
Stomach
Small intestine
Large intestine (colon) 
Rectum

Accessory organs include the liver, pancreas, and gallbladder

Question 4

The process by which our body synthesizes glucose?

Answer 4

Gluconeogenesis

Question 5

What 3 precursors can be used to produce glucose through gluconeogenesis?

Answer 5

Pyruvate, lactate, and amino acids

Question 6

Classification of carbohydrates-

3 examples of monosaccharides
3 examples of disaccharides
4 examples of polysaccharides

Answer 6

Glucose, galactose, and fructose
Lactose, maltose, sucrose
Glycogen, starch, cellulose, and GAGs

Question 7

Carbohydrate digestion in the mouth

Answer 7

This is where carbohydrate digestion begins.

Saliva contains salivary amylase, which hydrolyzes(breaks using water) 5% of starch(a polysaccharide) in the mouth.

Question 8

Carbohydrate digestion in the stomach

Answer 8

Minimal carbohydrate digestion occurs here. The salivary amylase is inactivated by the acidity of the stomach.

Question 9

Carbohydrate digestion in the lumen of the small intestine

Answer 9

Overall- stuff entering the small intestine is neutralized and broken down into monosaccharides.

Bicarbonate (HCO3-) and amylase are secreted from the pancreas into the small intestine. Bicarbonate is a conjugate base buffer that neutralizes acidic stomach contents so it is safe for the intestine walls.

The pancreatic amylase hydrolyzes disaccharides and complex carbs into monosaccharides.

Question 10

What does the pancreas release to aid in the digestion of carbohydrates in the small intestine

Answer 10

Bicarbonate and pancreatic amylase

Question 11

At the end of carbohydrate digestion in the small intestine, ___% of monosaccharides are glucose

Answer 11

~80%

Question 12

At the end of the small intestine, where are monosaccharides absorbed into

Answer 12

Into enterocytes, which are cells that line the small intestine, and then they are able to reach the blood capillaries. Substances cannot pass BETWEEN epithelial cells because these cells are bound by tight junctions.

Question 13

Monosaccharides (mostly glucose) can enter enterocytes by 2 methods

Answer 13

1. Facilitated diffusion- the movement of substances from an area of higher to an area of lower concentration using a carrier protein in the cell membrane.
2. Co-Transport- Uses movement of 1 molecule through the cell membrane from higher to lower concentration to power the movement of another from lower to higher.

Cannot travel through the membrane without help since it is hydrophilic.

Question 14

Enterocytes

Answer 14

Cells that line small intestine wall. Bound by tight junctions.

Question 15

Goal of carb digestion

Answer 15

Break down large carbs into glucose

Question 16

After monosaccharides enter enterocytes, where does it go?

Answer 16

Enterocytes- capillaries- venules- hepatic vein- liver

Question 17

In the liver

1. galactose is primary converted to:
2. Fructose is primarily converted to:
3. Glucose is stored as:

Answer 17

1. Glucose
2. Glucose and lactate
3. Glycogen

Question 18

What is the role of glycogen in the liver?

Answer 18

It is stored to maintain blood glucose levels at 70-100mg/dL.

If levels drop below 70mg/dL, liver will break down glycogen into glucose and release it.

Question 19

When liver cells and peripheral tissues are saturated with glycogen, excess glucose is converted into

Answer 19

Fatty acids

Question 20

Difference between soluble and insoluble fiber

Answer 20

Insoluble- Passes through digestive tract relatively untouched. This speeds up digestion and adds bulk to stool so it can pass easier.

Soluble- Forms a gel when mixed with water in the digestive tract. This slows down digestion and absorption of glucose, thereby preventing blood glucose spikes. The soluble fiber is then fermented by colon bacteria into short-chain fatty acids and gases.

Question 21

Type 1 diabetics

Answer 21

Insulin hormone is not produced, which is genetic.
If insulin cannot instruct peripheral cells to take up glucose, glucose will remain in the blood and pool at the capillaries.

Glucose at the capillaries causes damage, leaking of blood, and insufficient nutrition transfer.

Results in capillary dropout and ischemia (reduced blood flow). Tissues will begin to die.

Question 22

Role of insulin

Answer 22

Insulin is a hormone messenger that binds cells and tells them to allow glucose into the cell, thereby reducing blood glucose levels.