Digestion And Absorption Flashcards
What are the four types of digestive processes
- Mechanical
- Chemical
- Enzymatic (luminal and mucosal)
- Microbial
What does mechanical processing involve
- mastication (chewing)
- grinding action of the gizzard (birds)
- movement of the GI tract (segmentation and peristalsis)
What does chemical processing involve
HCl or gastric acid (pH 1.5-3.5)
What is involved in enzymatic digestive processing
What kind of enzymes are used
Digestive enzymes get secreted into the digestive tract
There are both luminal and mucosal enzymes
What is microbial digestive processing similar to (is)
It is also or similar to enzymatic digestion
Generally: what exactly is absorption
It is the ability for nutrients to move from the lumen to the blood stream by moving through the gut mucosal wall
What are the 2 main routes of absorption
- Transcellular (across cells)
- Paracellular (between cells)
What are the three transport mechanisms used in absorption
- Passive transport
- Active transport
- Osmosis (only for water)
—) uses aquaporins
What kinds of diffusion can be used in passive transport
- Facilitated diffusion
- Simple diffusion
- Osmosis (only for water)
Based on concentration where does water flow
It flows from low to high concentration
—) because it tries to even out the difference in concentration
What is the gradient called that influences the passive movement of substances
The electrochemical gradient
Where in the GIT is the most water absorbed
How is water absorbed (passive or active)
The small intestine
By passive transport (water can go through or between cells)
What happens to the majority of water in the body
Most of it is reabsorbed by the small intestine
What kind of bonds does cellulose have what kind of bonds does amylose have
Cellulose (beta bonds)
Amylose (alpha bonds)
What are the three kinds of monosaccharides
What are the three kinds of disaccharides (what is their make up)
Monosaccharides
- glucose
- fructose
- galactose
Disaccharides
- sucrose (glucose + fructose)
- maltose (glucose + glucose)
- lactose (glucose + galactose)
What kind of enzymes do bacteria have that allows them to cleave B bonds
Cellulolytic enzymes
Give some examples of enzymes that break down polysaccharides
- maltase
- alpha dextrinase
- alpha amylase
What are the two phases in carb digestion
- Luminal phase
- Brush border phase
Give a few examples of brush border enzymes
- isomaltase
- maltase
- lactase
- sucrase
How is glucose transported in absorption
What if there are high glucose levels in the body, what does this
By secondary active transport
If there are high glucose levels in the body then they can be transported passively by glut 1
How is fructose absorbed
Can it go against its concentration gradient
By facilitated diffusion
No it can not go against its concentration gradient
Describe the process of carb digestion and absorption
- Starts in the mouth
- amylase breaks down starches and comes from saliva and the pancreas - 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
- 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)
What usually happens with lactase as animals age
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
What are the basic building blocks of proteins
Amino acids
What kinds of bonds link amino acids together
Peptide bonds
What form are amino acids usually consumed as
Proteins
Describe the primary, secondary, tertiary and quaternary structure of proteins
Primary: assembly (order)
Secondary: folding
Tertiary: packing
Quaternary: interaction with other proteins
—) hydrophobic interactions
What form are most ingested fat in
Most of them are in the form of triglycerides
What denatures Nucleic acids
Gastric acid
What cleaves the phosphate of Nucleic acids (where is it found)
They are broken down by pancreatic nucleases on th brush border
What catalyzes the breaking of covalent bonds between the nitrogenous base and the pentose sugar
Nucleosidase
Where are nucleotide breakdown products absorbed
In the small intestine (duodenum Jejunum and ilium)
Mainly in the Jejunum
What kind of transport do nucleotide breakdown products use to be transported
By active and secondary active transport, they can also use passive transport depending on their R group (polarity)
Where are Nucleic acids transported to?
They are transported to the liver and other tissues
What is the basic make up of a triglyceride
1 glycerol backbone
3 fatty acid chains
What do triglycerides break down into
They break down into a glycerol backbone + 1 fatty acid chain (monoglyceride)
And PUFA chains or free fatty acids
Where does lipid digestion begin
In the stomach
Describe the steps involved in lipid digestion
- Stomach (mechanical) mixes substances
- Small intestine (lipase and bile salts) Emulsification &
micelles —) micelles allow fat to get glose to mucosal surface - Monoglycerides and FFA’s in cell
First reformed then packaged into chylomicrons
What is found in a chylomicron
- proteins
- phospholipids
- cholesterol
- triglycerides
Describe the steps involved in protein digestion
- Begins in stomach (lumen)
—) acid HCl and Pepsinogen —) pepsin (activated by HCl) - Small intestine
- pancreatic enzymes
- trypsinogen —) trypsin
- chemotrypsinogen —) chymptrypsin
- proelastase etc —) elastase
Converted by enterokinase (starts on brush border) - Brush border (membrane)
- amino peptidase (cleaving amino acids off of chain)
Polarity determines how amino acids are transported (some require energy, some don’t)
