Digestion And Absorption

Question 1

What are the four types of digestive processes

Answer 1

1. Mechanical
2. Chemical
3. Enzymatic (luminal and mucosal)
4. Microbial

Question 2

What does mechanical processing involve

Answer 2

• mastication (chewing)
• grinding action of the gizzard (birds)
• movement of the GI tract (segmentation and peristalsis)

Question 3

What does chemical processing involve

Answer 3

HCl or gastric acid (pH 1.5-3.5)

Question 4

What is involved in enzymatic digestive processing
What kind of enzymes are used

Answer 4

Digestive enzymes get secreted into the digestive tract
There are both luminal and mucosal enzymes

Question 5

What is microbial digestive processing similar to (is)

Answer 5

It is also or similar to enzymatic digestion

Question 6

Generally: what exactly is absorption

Answer 6

It is the ability for nutrients to move from the lumen to the blood stream by moving through the gut mucosal wall

Question 7

What are the 2 main routes of absorption

Answer 7

1. Transcellular (across cells)
2. Paracellular (between cells)

Question 8

What are the three transport mechanisms used in absorption

Answer 8

1. Passive transport
2. Active transport
3. Osmosis (only for water)
   —) uses aquaporins

Question 9

What kinds of diffusion can be used in passive transport

Answer 9

1. Facilitated diffusion
2. Simple diffusion
3. Osmosis (only for water)

Question 10

Based on concentration where does water flow

Answer 10

It flows from low to high concentration
—) because it tries to even out the difference in concentration

Question 11

What is the gradient called that influences the passive movement of substances

Answer 11

The electrochemical gradient

Question 12

Where in the GIT is the most water absorbed
How is water absorbed (passive or active)

Answer 12

The small intestine
By passive transport (water can go through or between cells)

Question 13

What happens to the majority of water in the body

Answer 13

Most of it is reabsorbed by the small intestine

Question 14

What kind of bonds does cellulose have what kind of bonds does amylose have

Answer 14

Cellulose (beta bonds)
Amylose (alpha bonds)

Question 15

What are the three kinds of monosaccharides
What are the three kinds of disaccharides (what is their make up)

Answer 15

Monosaccharides
- glucose
- fructose
- galactose

Disaccharides
- sucrose (glucose + fructose)
- maltose (glucose + glucose)
- lactose (glucose + galactose)

Question 16

What kind of enzymes do bacteria have that allows them to cleave B bonds

Answer 16

Cellulolytic enzymes

Question 17

Give some examples of enzymes that break down polysaccharides

Answer 17

• maltase
• alpha dextrinase
• alpha amylase

Question 18

What are the two phases in carb digestion

Answer 18

1. Luminal phase
2. Brush border phase

Question 19

Give a few examples of brush border enzymes

Answer 19

• isomaltase
• maltase
• lactase
• sucrase

Question 20

How is glucose transported in absorption
What if there are high glucose levels in the body, what does this

Answer 20

By secondary active transport
If there are high glucose levels in the body then they can be transported passively by glut 1

Question 21

How is fructose absorbed
Can it go against its concentration gradient

Answer 21

By facilitated diffusion
No it can not go against its concentration gradient

Question 22

Describe the process of carb digestion and absorption

Answer 22

1. Starts in the mouth
   - amylase breaks down starches and comes from saliva and the pancreas
2. Breakdown of oligosaccharides trisaccharides and disaccharides in the small intestine (ileum Jejunum and duodenum) by enzymes at the brush border or by the mucosa

Enzyme examples: lactase, maltase, sucrase

3. Absorption
   - can only absorb monosaccharides
   - can be absorbed by diffusion along conc. Gradient or by facilitated active transport
   - glalactose and fructose can be turned into glucose and can go to the liver or it can be turned into fat to store energy (liver does this)

Question 23

What usually happens with lactase as animals age

Answer 23

The activity of lactase decreases because animals usually no longer need to break down lactose because they stop drinking milk

This also causes lactose intolerance in people

Question 24

What are the basic building blocks of proteins

Answer 24

Amino acids

Question 25

What kinds of bonds link amino acids together

Answer 25

Peptide bonds

Question 26

What form are amino acids usually consumed as

Answer 26

Proteins

Question 27

Describe the primary, secondary, tertiary and quaternary structure of proteins

Answer 27

Primary: assembly (order) Secondary: folding Tertiary: packing Quaternary: interaction with other proteins —) hydrophobic interactions

Question 28

What form are most ingested fat in

Answer 28

Most of them are in the form of triglycerides

Question 29

What denatures Nucleic acids

Answer 29

Gastric acid

Question 30

What cleaves the phosphate of Nucleic acids (where is it found)

Answer 30

They are broken down by pancreatic nucleases on th brush border

Question 31

What catalyzes the breaking of covalent bonds between the nitrogenous base and the pentose sugar

Answer 31

Nucleosidase

Question 32

Where are nucleotide breakdown products absorbed

Answer 32

In the small intestine (duodenum Jejunum and ilium) Mainly in the Jejunum

Question 33

What kind of transport do nucleotide breakdown products use to be transported

Answer 33

By active and secondary active transport, they can also use passive transport depending on their R group (polarity)

Question 34

Where are Nucleic acids transported to?

Answer 34

They are transported to the liver and other tissues

Question 35

What is the basic make up of a triglyceride

Answer 35

1 glycerol backbone 3 fatty acid chains

Question 36

What do triglycerides break down into

Answer 36

They break down into a glycerol backbone + 1 fatty acid chain (monoglyceride) And PUFA chains or free fatty acids

Question 37

Where does lipid digestion begin

Answer 37

In the stomach

Question 38

Describe the steps involved in lipid digestion

Answer 38

1. Stomach (mechanical) mixes substances 2. Small intestine (lipase and bile salts) Emulsification & micelles —) micelles allow fat to get glose to mucosal surface 4. Monoglycerides and FFA’s in cell First reformed then packaged into chylomicrons

Question 39

What is found in a chylomicron

Answer 39

- proteins - phospholipids - cholesterol - triglycerides

Question 40

Describe the steps involved in protein digestion

Answer 40

1. Begins in stomach (lumen) —) acid HCl and Pepsinogen —) pepsin (activated by HCl) 2. Small intestine - pancreatic enzymes - trypsinogen —) trypsin - chemotrypsinogen —) chymptrypsin - proelastase etc —) elastase Converted by enterokinase (starts on brush border) 3. Brush border (membrane) - amino peptidase (cleaving amino acids off of chain) Polarity determines how amino acids are transported (some require energy, some don’t)