digestion from food to poo crash course video: pieces of food chemical

DigestionDigestionFrom food to poo Crash Course VIDEO: http://www.youtube.com/watch?v=s06XzaKqELk

Pieces of food

Chemical digestion(enzymatic hydrolysis)

Food

Nutrientmoleculesenter bodycells

Smallmolecules

Undigestedmaterial

ELIMINATIONABSORPTIONDIGESTIONINGESTION

Mechanicaldigestion

http://www.youtube.com/watch?v=s06XzaKqELk

http://www.youtube.com/watch?v=s06XzaKqELk

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

IB Learning Objective

• Explain why digestion of large food molecules is essential

The Need for Digestion

Two reasons for the digestion of food:

1. Change food into useable forms:

– Food that humans eat contain substances made by other organisms. Manu of which are not suitable for human tissue.

– Thus the must be broken down and changed into useful forms

– Example:

Proteıns amıno acıds dıfferent proteıns

The Need for DigestionTwo reasons for the digestion of food:

2. Food molecules may be too big to be absorbed:

– Food molecules are absorb by the villi in our small intestines.

– Thus food molecules must be broken down into small enough molecules that they can be absorbed by:

• Simple diffusion,

• facilitated diffusion

• or active transport.


IB LEARNING OBJECTIVE

• State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase

Three types of food molecules that must be digested

1. Starch

2. Proteins

3. Triglycerides (Fats and Oils)


Enzymes of digestion

Amylase Protease Lipase

Example of enzyme

Salivary Amylase

Pepsin Pancreatic Lipase

Source Salivary glands

Wall of stomach Pancreas

Substrate Starch Proteins Triglyerides (fats and oils)

Products Maltose Small Peptides Fatty Acid and glycerol

Optimum pH

pH 7 pH 1.5 pH 7



• Explain the need for enzymes in digestions

Enzymes essential to digestion of food molecules

• Digestions of food molecules will happen naturally at body temperature BUT very slowly

• Thus, ENZYMES are essential to speed up the process.



• Outline the reasons for cellulose not being digested in the alimentary canal.


Summary of digestion

• Some molecules cannot be digested (example: Cellulose)

• The enzyme cellulase digest cellulose, but humans lack the gene that codes for this enzyme.

• Undigested cellulose is an important part of dietary fibre, which has beneficial effects on the digestive system.



• Draw and Label a diagram of the digestive system. This diagram should include the following structures and clearly show the interconnections between these structures:

– Mouth

– Esophagus

– Stomach

– Small intestines

– Large intestines

– Anus

– Liver,

– Pancreas

– Gall bladder

Parts of the Digestive System

Mouth

Salivary glands

Stomach

Pancreas

Large intestine

Small intestine

Pharynx

Esophagus

Liver

Gallbladder

Rectum

Sequence of digestion

– Food is digested as it passes along the alimentary canal from mouth to anus.

– Food enters mouth, moves into the esophagus, the stomach, next small intestine, then large intestine, and finally anus.


Video Of Digestions

• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html

• http://www.youtube.com/watch?v=bNMsNHqxszc

• FUNNY VIDEO:

http://www.youtube.com/watch?v=jsVgi8hoFFc

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html



http://www.youtube.com/watch?v=bNMsNHqxszc

http://www.youtube.com/watch?v=jsVgi8hoFFc

Summary of digestion

• Longitudinal and circular muscle fibers along the walls of the alimentary canal contract and relax squeezing the food and breaking up large solid lumps.

• Digestive juices release by salivary glands, stomach and pancreas contain enzymes which help break food molecules

LE 41-15b

Esophagus

Stomach

Liver

Salivaryglands

Gall-bladder

Pancreas

Rectum

Anus

Largeintestines

Smallintestines

Mouth

A schematic diagram of thehuman digestive system



• Outline the function of the stomach

The Stomach Summary

• The Stomach

• Food from the esophagus empties into the stomach.

• The stomach continues mechanical and chemical digestion.

• Alternating contractions of three smooth muscle layers churn food.


Stomach

Function of Stomach Summary

– Mechanical Digestion

• The stomach contracts to churn fluids and food, gradually producing a mixture known as chyme.

• After 1–2 hours, the pyloric valve between the stomach and small intestine opens and chyme flows into the small intestine.

The Stomach Summary

– Chemical Digestion

• The stomach lining has millions of gastric glands that release substances into the stomach.

– Some glands produce mucus, which lubricates and protects the stomach wall.

– Other glands produce hydrochloric acid, which makes the stomach contents very acidic.

– Other glands produce pepsin, an enzyme that digests protein.


Interior surface of stomach

Function of Stomach

• Before food reaches the stomach, gastric juices are being secreted, as a result of a involuntary reflex action.

• When food enters the stomach more gastric juices are released.

Function of Stomach

• When food enters the stomach a hormone gastrin is released.

• Gastrin signals for the stomach to increase the amount of hydrochloric acid (HCl) in the stomach

• The pH of the stomach is about 3 (very acidic) when food enters

Function of Stomach

• Bacteria which could cause food poisoning, are most killed by acid conditions.

Enzymes released by stomach.

• Enzyme released by stomach is pepsin.

• Pepsin functions has an optimum pH of 1.5 (very acid).

• Pepsin digests proteins.

Pepsin vs. Pepsinogen

• Since pepsin digests proteins, it could be harmful to the cell of the glands that secrete them.

• They are therefore secreted as an inactive pre-cursors called Pepsinogen.

• Pepsinogen is an inactive form of pepsin.

• Pepsinogen becomes pepsin when it is released in the hydrochloric acid (HCl) of the stomach

Structure of stomachLE 41-17

Esophagus

Cardiac orifice

Pyloric sphincter

Smallintestine Folds of

epithelialtissue

Stomach

Epithelium

Pepsin(active enzyme)

Pepsinogen

HCl

Pepsinogen and HClare secreted into the lumen of the stomach.

HCl convertspepsinogen to pepsin.

Pepsin then activatesmore pepsinogen,starting a chainreaction. Pepsinbegins the chemicaldigestion of proteins.

Parietal cellChief cell

Chief cells

Mucus cells

Parietal cells

Interior surface of stomach

Gastric gland

5 µ

m



• Outline the function of the small intestine

Function of the Small Intestine

• The small intestine is the longest section of the alimentary canal

• It is the major organ of digestion and absorption

LE 41-19

Stomach

Pancreas

Liver

Gall-bladder

Duodenum ofsmall intestine

Intestinaljuice

Bile

Acid chyme

Pancreatic juice

The Small Intestine

• As chyme from the stomach is pushed through the pyloric valve, it enters the duodenum.

• The duodenum is the first of three parts of the small intestine, and is where most digestive enzymes enter the intestine.

The Small Intestine

• Accessory Structures of Digestion

Liver

Gallbladder

Duodenum

Bile duct

Pancreas

Pancreatic duct

To rest of small intestine

The Small Intestine

– Accessory Structures of Digestion

• Just behind the stomach is the pancreas.

The Small Intestine

• During digestion, the pancreas:

• produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids.


Enzymes of the Pancreas

• Amylase – completes breakdown of starches into maltose

• Protease – completes the breakdown of small polypeptides (proteins) to amino acids

• Lipase – converts fat to glycerol and fatty acids


Pancreas

• Pancreas also produces sodium bicarbonate, a base that neutralizes stomach acid so that these enzymes can be effective.

• Sodium bicarbonate is released into the duodenum of the small intestine right after chyme enters it from the stomach.


LIVER

• Assisting the pancreas is the liver, which produces bile.

• Bile dissolves and disperses droplets of fat in fatty foods. This process is called emulsification

• Emulsification increases surface area of lipid droplets

• This enables enzymes (lipase) to break down smaller fat molecules.


Liver – Bile -- Digestion of Lipids

• Bile is stored in the gallbladder.

– and released into the small intestines.

– Lipid molecules tend to bond together and are only accessible to lipase (enzyme) at the lipid–water interface/ boundary.


Parts of the small intestines

Absorption in the Small Intestine

• The small intestine is adapted for the absorption of nutrients.

• Most absorption occurs in the ileum of the small intestine



• Explain the structure of the villus is related to its role in absorption and transport of products of digestions


Absorption in the ileum of the Small Intestine

• The folded surfaces of the ileum are covered with fingerlike projections called villi.


Ileum

• The Small Intestine



Relationship between structure of villus and its function

• Villi increase surface area over view food is absorbed

• An epithelium consists of only one layer of cells, which is all that food have to pass through in order to be absorbed

• Protrusions of exposed plasma memebrance of the epithelium called microvilli, increase surface area for absorption.


• The Small Intestine


• Cell surfaces of villi have more projections called microvilli.

• These provide an enormous surface area for the absorption of nutrient molecules.

• Slow, wavelike contractions of smooth muscles move the chyme along this surface.




• Protein channels and pumps in microvilli allow for rapid absorption of food by facilitated diffusion and active transport

• A lot of mitochondria in epithelium cell need for ATP in active transport.



• Blood capillaries inside villus are very close to epithelium so the distance for diffusion of food is very small.

• A lacteal (lymph vessel) in the centre of villus carries fat away after digestion.



• There are many pinocytic vesicles near the microvilli.

• Pinocytic vesicles are formed by endocytosis

• Each vesicles are formed from plasma membrane and so contain both:

– Protein channels for facilitated diffusion

– Protein pumps for active transport

• Digested food can be absorbed from vesicles into the cytoplasm of cells


Small Intestine


Ileum of the small intestines



• Outline the function of the large intestine


Large Intestine

The Large Intestine

• The Large Intestine

• When the chyme leaves the small intestine, it enters the large intestine, or colon.

• The large intestine removes water from the chyme.

• Water is absorbed quickly, leaving undigested materials behind.

• Concentrated waste material passes through the rectum and is eliminated from the body.

• The colon houses strains of the bacterium Escherichia coli, some of which produce vitamins

digestion from food to poo crash course video: pieces of food chemical

Documents