Objectives: 1.Label the gross structure of the digestive system 2.List the basic units produced by the digestion of the three macromolecules 3. State the four stages of digestion. 4.Describe in detail the digestion of one macromolecule including the specific enzymes involved

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Stages of digestion Ingestion Digestion Absorption Egestion

Digestion: breaking down large molecules Physical Chemical Chewing Peristalsis Churning Hydrolysis reactions Enzymes Substances

Digestive juices: Saliva Gastric Pancreatic Intestinal All contain enzymes

Carbohydrate Digestion Two Stages Starch to Maltose Maltose to Glucose

Carbohydrate : Starch Digestion starts in the mouth Physical: Teeth / chewing Tongue Chemical Salivary Amylase Starch Amylase Maltose Mucus

Carbohydrate : Starch 2 Oesophagus Physical Peristalsis Chemical Mucus

Figure 14.3A Slide 14.4 Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Peristalsis

Carbohydrate : Starch 3 Stomach Physical Churning

Carbohydrate : Starch 4 Small intestine Physical Peristalsis

Carbohydrate : Starch 5 Small intestine Chemical Pancreatic juice Pancreatic amylase Starch Amylase Maltose Enzymes in cell wall Maltase Maltose Maltase Glucose

Objectives: 1.Label the gross structure of the digestive system 2.List the basic units produced by the digestion of the three macromolecules 3. State the four stages of digestion. 4.Describe in detail the digestion of one macromolecule including the specific enzymes involved

Structure of digestive system Basic structure alimentary canal Specific Structure Organs Accessory glands

Figure 14.2 Slide 14.2A Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Gastrointestinal (GI) Tract Wall

Alimentary canal Four common layers throughout the system: Mucosa: innermost layer : secretion/ absorption, (folded, glands) Submucosa: connective tissue, lymph, blood vessels, glands and nerves Muscularis: two layers of smooth muscle, responsible for peristalsis Serosa: outermost layer, connective tissue connects to abdomen Slide 14.2B General Structure of the Alimentary Canal

Stomach Muscular sac (4 litres) Sphincter muscles Mucosa: Walls contain many folds Gastric glands Muscularis: Extra muscle layer (3)

Figure 14.7 Slide 14.9A Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Structure of the Stomach Wall

Small Intestine (Duodenum) Small intestine = 6.5 meters long (approx) Duodenum (first 25cm) Includes bile and pancreatic duct Most digestion is completed in duodenum Mucosa: Few villi Enzymes in the plasma membrane Submucosa Blood / lymph vessels, glands, nerves

Small Intestines (ileum) Jejunum (2m) and ileum (4m) 95% nutrient absorption How would you would expect the structure of the ileum to be?

Mucosa Greatly folded Villi (large structures in mucosa) Microvilli (brush borders) Glands Enzymes in the plasma membrane

Small Intestines (ileum) Submucosa Good blood supply Lymph vessel supply (lacteals) Glands Nerves

villi

microvilli

Absorption Small soluble molecules are absorbed through the microvilli lining by: Diffusion Facilitated diffusion Active transport

Glucose Active transport (gut to epithelial cell) Linked to sodium ions Actively pumped out Facilitated diffusion (epithelial cell to capillaries)

Amino Acids Facilitated diffusion (gut to epithelial cell) AA = different carrier Linked to sodium ion Actively pumped out Facilitated diffusion (epithelial cell to capillaries)

Lipid digestion

Lipid Absorption Mucosal cell Lacteal Monoglycerides Fatty Acids Diffusion Bile salts

What’s left? Large Intestine (colon) Undigested food Bacteria (mutual benefit) Water and vitamins reabsorbed Large, folded walls. Rectum Anus

Name the small soluble food molecule resulting from protein, lipid and carbohydrate digestion. Amino acids, fatty acids + glycerol and glucose. Amino acids, fatty acids + glycerol and glucose. Name 3 other molecules which the body needs in a balanced diet. Vitamins, minerals and water. Vitamins, minerals and water. Where in the alimentary canal are these 3 absorbed? The large intestine. The large intestine.

Which blood vessel takes small food molecules away from the small intestine. Where are they taken to first? Hepatic portal vein. The liver. Hepatic portal vein. The liver. What happens to excess glucose? I.e. glucose not needed immediately for respiration. It’s converted into glycogen and stored in the liver or muscle cells It’s converted into glycogen and stored in the liver or muscle cells What happens to excess amino acids taken into the liver? Amino acids can’t be stored so they are deaminated by the liver cells producing glucose and a waste product calledurea Amino acids can’t be stored so they are deaminated by the liver cells producing glucose and a waste product called urea

Villi

How do cells assimilate the big nutrients? a) Glucose provides energy by cell respiration resultion in A.T.P to enable the cell to do work eg muscle cell contraction. b) Amino acids build into new human protein eg enzymes, plasma proteins, hormones and are used in growth and repair. b) Amino acids build into new human protein eg enzymes, plasma proteins, hormones and are used in growth and repair. c) Fatty acids and glycerol are used to build cell membranes and for cell respiration. c) Fatty acids and glycerol are used to build cell membranes and for cell respiration.

Ficks law Large SA Concentration gradient Thickness of membrane

Lipids Combine with bile salts Monoglycerides, fatty acids = glycerol Micelles travel to epithelial cell membrane MG,FA and G dissolve in phospholid bilayer (Diffusion) Bile salts left behind Triglycerides combine with proteins form chymomicrons Diffuse into lacteals

Proteins Dipeptides Facilitated diffusion (gut to epithelial cell) Cytoplasmic enzymes Proteins Pinocytosis (maternal antibodies)