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3_Nutrition and Digestive
Nutrition and Digestive
58
Biology
Graduate
01/31/2010

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Term

Digestive System (4 step process) ? 

 

Definition

Indigestion, Digestion, Absorption, Elimination (egestion) 


  1. Ingestion: placing food into the mouth 
  2. Digestion (Mechanical and chemical breakdown) mastication + mix bolus with water, acidsbile and enzymes in the stomach and intestine to break down complex molecules into simple structures,
  3. Absorption: of nutrients from the digestive system to the circulatory and lymphatic capillaries through osmosisactive transport, and diffusion, and
  4. Egestion: Removal of undigested materials from the digestive tract through defecation.

 

the cephalic phase - saliva is produced in the mouth and digestive enzymesare produced in the stomach.

Mechanical and chemical digestion begin in the mouth where food is chewed, and mixed with saliva to begin enzymatic processing of starches. The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. 

Absorption occurs in the stomach and gastrointestinal tract, and the process finishes withdefecation.[1]

Term
Path of Food when being digested (top to bottom)?
Definition

Think about food: Cephalic 

Food in mouth: Gastric 

In stomach: intestinal 

 

Oral Cavity:  chew > salivary amylase >  bolus > swallowing 

 

Pharynx:   larynx moves up  > epiglottis close over trachea (windpipe) > bolus goes down esophagus via perstalisis > stomach 

 

Stomach: bolus > cardiac orfice > gastrin stimulate secretion of pepsinogen, gastric acid, HCl(parietal cell) >  mix > break proteins + kill organism > chyme 

 

Small Intestine: chyme > pyloric sphincter > duodenum > 

*acidity of chyme stimulate secretin  >  pancreatic juice (bicarbonate) + bile creation from liver > pH becomes more basic > stimuate other hormone and enzyme

AND / or

*carb in chyme stimulate pancreas > produce maltase, lactase and sucrase) 

*protein in chyme stimulate CCK >  trypsin, chymotrypsi

*fat in chyme stimuate CCK > bile released from gallbladder

and entergasterone > blocks gastrin > decrease amount of acid > slow stomach churning 

 > 1 or 2 

 

1. absorbed by microvilli >   lymphatic system or circulatory > circuatory:  blood carries nutrients away to liver by hepatic portal vein 

2.  peristalsis >jejunum and illeum > undigested to large intestine 

 

Large intestine (cecum, colon, rectum),: undigestable food >  cecum > breaks down cellulose and minor defense > colon> enteric bacteria system: rest ferments in gut bacteria  > bacteria consumes things we do not eat >  absorb some nutrients like vitamin A, B through villi > produce H2S and methane> absorb mostly fluid > rectum > store shit > anal sphincter > anus

 

 

 

Term

Enzymes needed for Carbohydrate digestion?

Chemical Pathway of Carb digestion? 

Definition

need amylase and dissaccharidases

 

starch -> broken down to small units ->broken down to sugar outside-> into cell-> sugar absorb by cell -> blood supply

  1. Salivary amylase (phyalin) (mouth) 
  2. pancreatic amylase (pancreas)
    • product: usually maltose- glucose + glucose dimer   

disaccharidases (breaks the dimers)

  1. maltase (brush border enzyme)  (disaccharidases)
  2. sucrase (disaccharidases)
  3. lactase (disaccharidases)

 

Term
pancreatic amylase
Definition

 

  • made in : pancreas 
  • used in: small intestine 
  • breaks: starch -> maltose

 

Term
salivary amylase
Definition

 

  • made in : salivary glands 
  • used in: mouth 
  • breaks: starch -> maltose
  • more or less to protect our teeth. 

 

Term
maltase
Definition

 

  • made in: intestinal glands 
  • used in: small intestine 
  • breaks: disaccharide maltose -> 2 glucose 
  • brush border enzyme

 

Term
lactase
Definition

 

  • made in: intestinal gland 
  • used in: small intestine 
  • breaks: lactose -> glucose and galactose

misc: as a child, the brush border will make lactase. This enzyme is no longer active, lactase, as a teen for some. Then you are lactose enzyme. You cannot absorb lactose so it goes thorugh.

 

Term
disaccharidases
Definition

 enzymes that break down disaccharides into monosaccharides.

example:

  • Lactase (breaks down lactose into glucose and galactose)
  • Maltase (breaks down maltose into 2 glucoses)

 

 

Term
maltose
Definition

 

  •  disaccharide = two units of glucose joined with an α(1→4) linkage. 
  • Saliva contains salivary amylase
    • hydrolyzes starch and glycogen into smaller polysaccharides and the disaccharide maltose.

 

Term

Enzymes needed for protein digestion?

Chemical Pathway of Protein digestion? 

Definition

amino acids are broken down by proteases

 

protein --> hormone CCK --> enterokinase enzyme -> activate zymogens 


large complex linear polymer (meat) --> small pieces (chew) --> bits --> bits into surface by diffusion--> protein broken down to individual amino acids on the surface of the cells -> transport into cell (liver)-> transport out of cell ->to submucosa and picked up by capillaries. 

 

 

amino acids are broken down by proteases

 (separated bc don't want them to be digested 

 

  1. pepsinogen ->  pepsin (stomach) (attack from middle)
  2. trypsinogen ->  trypsin (pancrease)(attack from middle)
  3. chymotrysinogen -> chymotrypsin(pancrease)(attack from middle)
  4. procrboxypeptidase ->  carboxypeptidase (pancrease) (attack from end)
  5. proamino peptidases >  aminopeptidase (pancreas) (attack from end)
  6. dipeptidase (generic amino acid) (attack from middle)
  7. enterokinase (small intestine) 


Term
pepsin
Definition

made in: gastric glands (chief cells) 

used in: stomach 

function: hydrolyze specific peptide bond (which subsequently will go into small intestine)

Term
trypsin
Definition

 

  • made in: pancreas 
  • used in: small intestine 
  • function: 
    • breaks: specific peptide bonds left over after the stomach enzyme pepsin breaks down protein.
    • converts chymotypsinogen to chymotrypsin
  • impt bc: necessary for the uptake of protein in the food as though peptides are smaller than proteins, they are still too big to be absorbed through the lining of the ileum. 

 

Term
chymotrypsin
Definition

 

  • made in: pancreas 
    • by chymotrypsinogen that is enzymatically inactive -> cleavage by trypsin into two part --> active chymotrypsin
  • used in: small intestine 
  • function: hydrolyze specific peptide bonds (perform proteolysis)

 

Term
carboxypeptidase
Definition

 

  • made in: pancreas - carboxypeptidases are initially produced in an inactive form;
    • ex) the inactive zymogen form, (pro-carboxypeptidase A), is converted to its active form - carboxypeptidase A, by enterkinase 
    • why? mechanism ensures that the cells wherein pro-carboxypeptidase A is produced are not themselves digested.
  • used in: small intestine 
  • function: hydrolyze terminal peptide at carboxyl terminal
    •  involved in catabolism; they help to mature proteins or regulate biological processes

 

 

Term
aminopeptidase
Definition

 

  • made in: intestinal glands 
  • used in: small intestine 
  • function: hydrolyze peptide bond at amino terminal size
  •  a zinc-dependent enzyme .

 

 

Term
dipeptidase
Definition

 

  • made in: intestinal glands
  • secreted by: enterocytes onto the brush border of the villi
  • used in: small intestine 
  • function: hydrolyze PAIRS of amino acids (dipeptides)


Enterocytes, or intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon


 

 

Term
enterokinase (aka Enteropeptidase)
Definition

 

  • made in: intestinal glands (cells in the duodenum wall)
  • used in: small intestine 
  • function: converts trypsinogen (zymogen) to trypsin and indirectly activating a number of pancreaticdigestive enzymes and itself and cutsarginine and lysine.
  • secreted from duodenum's glands whenever ingested food enters the duodenum from the stomach.
  • part of the Chymotrypsin-clan of serine proteases, and is structurally similar to these proteins.

 

 

Term

What's needed for Lipid digestion? 

Chemical Pathway for Lipid digestion? 

Definition

fat: 3 C backbone attached to three fatty acids

      food and building block 

 

mix fat with water and bile and lipases -> attack and cut out two fatty acids à monoglyeride and two fatty acids à get them in cellà reassembled to trigycerlide -> chylo micron -> lymph villi (vessel called lacteal)--> blood supply -> break down to monoglycerid and fatty acide --> adipose, liver or acetyl CoA (cellular respiration ) 


 


1) chyme --> duodenum secretes CCK into the blood --> stimulate secretion of pancreatic enzyme and bile

2) bile-->NOT enzyme, made in liver, emulsify fat in small intestine

3) lipase -->  IS enzyme, made in pancreas, hydrolyze lipids in small intestine



 

Term
Enzymes needed for Nucleic Acid Digestion
Definition

same concept as proteins. 

 

  1. 5’ or 3’ exonucleases  (chew from opposite ends of RNA or DNA)
  2. endonuclease (just break the million long polymer into smaller short polymers).

 

Term

all enzymes in digestive systems are... 

Definition

water based.

(Problem: fats. Fats don’t want to mix with water. So need help from other secreion)

Term

GI Tract

What is it?

Goal? 

Definition

 

  • tube from mouth to anus 
  • anything inside the tube is essentially outside the body 

goal: take complex bio-molecules and break it down to constituent parts. 

 

Term
Features of Mechanical Breakdown
Definition


 

  1. Chewing: to give surface area for enzymes to work
  2. Churning: stomach breaking down food
  3. Segmentation: in small intestine, like kneading. 

 

 

Term
chyme
Definition

 

  1. begins in the stomach as a recently swallowed meal --> nutrient-rich broth known 
  2. result of mixing and enzyme action
  3. occasional backflow of acid chyme from the stomach into the lower esophagus causes heartburn.

 

 

 

Term
small intestine
Definition

 

(digestive system: indigestion, digestion, absorption, elimination)
  1. major organ of digestion and absorption (5-6 hours). 

  • enzymatic hydrolysis of food macromolecules
  •  most of the absorption of nutrients into the blood
2. first 25 cm (duodenum), acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gall bladder, and gland cells of the intestinal wall.

3. jejunum and ileum, function mainly in the absorption of nutrients and water.

4. longest section of the alimentary canal. (6m in humans)

 

 

Term
pancreas
Definition

Exocrine and endocrine (hormone)

  1. exocrine: produces several hydrolytic enzymes and an alkaline solution rich in bicarbonate that buffers the acidity of the chyme from the stomach.
  2. exocrine: accessory glands include the salivary glands, the pancreas, the liver, and the gallbladder.

 

 

 

Term
rectum
Definition

The terminal portion of the colon is called the rectum, where feces are stored until they can be eliminated.

  • Between the rectum and the anus are two sphincters, one involuntary and one voluntary.
  • Once or more each day, strong contractions of the colon create an urge to defecate.
Term
bolus
Definition

The tongue tastes food, manipulates it during chewing, and helps shape the food into a ball called a bolus.

 

During swallowing, the tongue pushes a bolus back into the oral cavity and into the pharynx.

 

 

Term

layers of stomach wall*

surface of stomach wall?* 

Definition

first three three layers are perendicular and oblique  

  1. mucosa
  2. submucosa
  3. muscularis 
  4. serosa (simple cubodial ephithelial) 
surface: a lot of gastic pits / exocrine glands- produce materials that come out the pit – gastric juice.

 

Term
pharynx
Definition

The oral cavity, pharynx, and esophagus initiate food processing.

 

The pharynx, also called the throat, is a junction that opens to both the esophagus and the trachea (windpipe).

 

The esophagus conducts food from the pharynx down to the stomach by peristalsis.

Term
epiglottis
Definition

When we swallow, the top of the windpipe moves up so that its opening, the glottis, is blocked by a cartilaginous flap, the epiglottis.

 

When not swallowing, the esophageal sphincter muscles are contracted, the epiglottis is up, and the glottis is open, allowing airflow to the lungs.

 

When a food bolus reaches the pharynx, the larynx moves upward and the epiglottis tips over the glottis, closing off the trachea.

 

 

Term
esophagus
Definition

The oral cavity, pharynx, and esophagus initiate food processing.

 

After chewing and swallowing, it takes 5 to 10 seconds for food to pass down the esophagus to the stomach, where it spends 2 to 6 hours being partially digested.

 

The esophagus conducts food from the pharynx down to the stomach by peristalsis.

  • The muscles at the very top of the esophagus are striated and, therefore, under voluntary control.
  • Involuntary waves of contraction by smooth muscles in the rest of the esophagus then take over.

 

 

 

Term
Microvilli (singular: microvillus)
Definition
  • villi: fingerlike projections on large circular folds in the lining [of the small intestines] 
  •  epithelial cell of a villus has many microscopic appendages called microvilli 
  • basis of the term “brush border” for the intestinal epithelium.
Term
myogenic*
Definition
if you stretch it, smooth muscle of esphogaus will contract. 
Term
proteases*
Definition

proteases – enzymes that help break down protein. Body produce these in an inactive form: zymogen. “–OGEN” à notate inactive form. 

Term
why is bicarbonate impt?
Definition

§  bicarbonate is brought by pancreas to increase the chyme and neutralize it and make the pH at 8. 

 

Term

bulk of bulk of feces ...

 

Definition
is bacteria, bit of cellulose,
Term
portal circulation* vs normal circulation
Definition

 

heart pump blood to arteries à capillaries à veins à to another system organ/tissue and then à back to heart 

 

instead of normal circulation:

heart pump blood to arteries à capillaries à veinsà back to heart.

 

Term
lymph system*
Definition
lymph system: takes excess liquid from body and dumps to the subclaveral veins. when this is blocked, you sweel. 
Term
mucosa* 
Definition

mucosa – a simple columnar ephitelial. These cells are specialized it the small intestine with microvilli. This covers from mouth to anus. This invaginates a lot of glands. Will secrete mucus 

Term
submuscosa*
Definition
submucosa: aread of connective tissue, a lot of aredar tissue; blood supply; lymph and nerves. 
Term

muscularis* 

Definition

a region of muscle in many organs in the vertebrate body

 

 

most organs have  smooth system (2 layers) 

stomach 3 layers are perpendicular and oblique (need three for the mechanical griding- contract in three direction)

 

Term
rugae*  
Definition
stomach is empty -> wrinkle and folded up
Term
types of cells in gastric pit* 
Definition

1) goblet cells 

  • functon: produce mucus - basic that allows it to protect cells from the acidity.
  • where: in the epithelial 

 

2) parietal cells

 

  • function: make HCl

 

3) chief cells

 

  • function: produce pepsinogen 
    • (pepsinogen is inactive until it reaches the lumen of the stomach).
    •  Activates when the pH is low but also activates itself when pH is low.

 

** everything above is used to go OUTSIDE the body - mucos, HCL, pepsongin

 


 

4) enteroendocrine cells: "within the body" hormones- used inside the body

 

  • function: make hormones 
  • function is in the CNS, not in the stomach ex) what tells you if you're hungry

 

 

Term
Gastrin, Glarelin, obestatin*
Definition

impt hormone made in gastric pit by enteroendocrine

 

gastrin – stimulate gastric juice.

  • protein enters, > lower pH >release gastrin -> release HCl 
  • Gastrin stimulates itself- positive feed back system.
  • When acidity gets too high, it shuts down.
  • (happens during gastrin phase)

 

glarelin – important for growing –stimulate feeding.

obestatin – stop eating 

 

obestatin and glarelin are made by same protein- cut one protein into two. You can produce one without the other. You can use one without the other. 

 

 

 

Term
Cephalic Phase, Gastric Phase, Intestinal Phase*
Definition

Cephalic phase: sight, smell and etc (pavolian). Intestine gets ready, saliva and enzyme gets ready

 

gastric phase: change in acidity by the actual food itself

 

intestinal phase: continue the stimulatory cycle but also the regulator to slow everything down. 

Term
crypt*
Definition

Crypt/ intestinal gland: intestinal juice (mucous where produced)

A lot of mitosis taking place here.

Make the cells that will replace the dying ones 

Term
ducts
Definition
Term

Secretin 

CCK

Enterogaston 

Nueropeptide Y 

Peptide YY

Leptin

Definition

Impt Hormones in Small Intestine 

 

1) secretin 

signal: low pH 

product: bicarbonate

 

2) CCK 

signal: lipid and peptides

product: target pancrease of enzyme  and ask gall bladder for bile

 

3) enterogaston 

signal: lipid

product: slow down stomach

 


4) neuropeptide Y

product: Hunger stimulant

where: in in central nervous system but produced in small intestine. Hunger stimulant

 

5) peptide YY:

product: inhibits hunger. 

where: in in central nervous system but produced in small intestine. Hunger stimulant

 

6) Leptin: made by fat cells. release when fat cells are full of fat. Ex) works in mice but not work in humans.

 

Term

bilireubin* 

Definition

pathway to get rid of waste


ex) bruise / hemoglobin: when it starts to break down, pigement gets green/yellow. this color represents bilireubin. liver gets rid of this and puts it in the bile. If this builds up, you get jaunice.

 

 

Term
bile 
Definition

 

  • made in liver
  • made up of phospholipids (cholesterol), neutral fats, billireubin
  • act as an emulsfier to break fat up to small droplets 

 

Term
digestion system of child vs. adult? 
Definition

  • rarely a whole protein will be engulfed to an adult but can happen in an infant.
  • breast milk is supposed to come through the epithetlium and enter the blood and work in the bloodstream (immune) 

Term
chylo micron 
Definition
can't move trigylceride in water (cell) so package them in protein so it's water soluble
Term
HDL and LDL 
Definition

  • basket of protein that carry cholestrol.
  • One has more protein than lilpid (HDL),
  • HDL is a good form of cholesterol
  • HDL cleans

  • one has more lipid than protein (LDL- low density).
  • LDL deposts

  • no such thing of good or bad choletsterol. depends on how it's carried to the liver. 

 

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