Digestive System Notes Unit 1: Biochemistry and Digestion Digestive System Notes Biochemistry and Digestion

Unit 1: Biochemistry and Digestion Food processing Ingestion Digestion (Mechanical vs. Chemical) Absorption Elimination

Unit 1: Biochemistry and Digestion Food processing OBJ 31/32 Ingestion Digestion Mechanical vs. Chemical

Unit 1: Biochemistry and Digestion A molecule (like starch) An enzyme

Unit 1: Biochemistry and Digestion Why digest food? It needs to be absorbed into your blood stream… Ingested molecules are too big! If they aren’t absorbed, they are eliminated We use the smaller parts to build new molecules

Digestive System Overview Unit 1: Biochemistry and Digestion Digestive System Overview

Unit 1: Biochemistry and Digestion Digestive Tract vs. Digestive System

Unit 1: Biochemistry and Digestion Mouth Teeth Mechanical digestion Saliva Wets food Salivary amylase (enzyme that breaks down starch) Kills bacteria Tongue Taste buds Moves food around

Unit 1: Biochemistry and Digestion Esophagus Muscular tube Moves food through peristalsis (wave-like muscle contractions) Demo Epiglottis prevents food from entering the trachea (to the lungs)

Unit 1: Biochemistry and Digestion Stomach Storage (2-3 hours) Muscular walls Churn stomach contents to liquify food (Mechanical Digestion) Gastric juice HCl – breaks down food, activates pepsin (pH 1-2) Pepsin - enzyme that breaks apart proteins (only works at low pH)

Pancreas (NOT digestive tract) Unit 1: Biochemistry and Digestion Pancreas (NOT digestive tract) Pancreatic Juice Pancreatic amylase is an enzyme that breaks down starch Other enzymes break down the other 3 organic macromolecules (what are they??) Fig 21.10A

Unit 1: Biochemistry and Digestion Pancreas OBJ 33 Pancreas also Produces insulin to lower blood glucose Produces glucagon to raise blood glucose

Liver and Gallbladder (NOT digestive tract) Unit 1: Biochemistry and Digestion Liver and Gallbladder (NOT digestive tract) Liver makes bile Gallbladder stores bile Increases lipid surface area by mechanical digestion Fig 21.10A

The party’s in the small intestine! Unit 1: Biochemistry and Digestion The party’s in the small intestine!

Unit 1: Biochemistry and Digestion Small Intestine More than 6 m long and 2.5 cm in diameter Pushes food through Duodenum 1st section (25 cm or so) Where hydrolysis finishes Receives substances from liver/gallbladder, pancreas, and cells of the small intestine

Small Intestine - Duodenum Unit 1: Biochemistry and Digestion Small Intestine - Duodenum OBJ 33 From liver via gallbladder – bile (breaks up lipids) From pancreas – Pancreatic juice (breaks down starch, proteins, nucleic acids, and lipids) PLUS – the small intestine makes its OWN enzymes! Fig 21.10A

Small Intestine - Absorption Unit 1: Biochemistry and Digestion Small Intestine - Absorption Absorption occurs here Huge surface area (300 m2) Lots of folds, villi, and microvilli

Small Intestine - Absorption OBJ 33 Cell 1 Cell 2 Villi Microvilli

Absorption in the small intestine Unit 1: Biochemistry and Digestion Absorption in the small intestine Where do nutrients go from the small intestine? How do they get into the blood stream? Where do they go once they are in the blood stream?

Large Intestine or Colon Unit 1: Biochemistry and Digestion Large Intestine or Colon What’s left? Water Cellulose (fiber) Other nondigestible material About 1.5 m long, 5 cm diameter Absorbs water E. coli live symbiotically and produce vitamins (vitamin K) Feces stored in rectum

Where different types of chemicals are broken down chemically: MOLECULES: Carbohydrates Proteins Lipids WHERE DIGESTED: Mouth, small intestine Stomach, small intestine Small intestine

Gross Facts Bacteria love the stuff we can’t break down…and gas & flatulence are caused by bacteria metabolizing these nutrients 99% of these gases are odorless People actually study these gases to find out the 1% of these gases that cause the odors (great job!) Feces is 1/2 bacteria by weight Newborns don’t pass gas because they have no bacteria in their intestines yet Beano breaks down some molecules the bacteria like Lactaid breaks down lactose Gas-X reduces the surface tension of gas bubbles, which makes you feel better….but the gas is still there Passing gas in public in ancient Rome was against the law

Unit 1: Biochemistry and Digestion The End

Unit 1: Biochemistry and Digestion Essential Amino Acids

Unit 1: Biochemistry and Digestion The breakdown… Molecules Where chemically digested Carbohydrates Mouth (to disaccharides) Small Intestine (to disaccharides and monosaccharides) Proteins Stomach (to smaller proteins) Small Intestine (to smaller proteins and amino acids) Lipids Small Intestine (to smaller lipids, then to glycerol and fatty acids) Nucleic Acids Small Intestine (to nucleotides)

Unit 1: Biochemistry and Digestion Why digest food? Too big Small enough Polysaccharides (starch, etc) Disaccharides (sucrose, etc) Triglycerides Proteins and polypeptides Monosaccharides (glucose, fructose, etc) Fatty acids Glycerol Amino acids Water

Stomach – gastric ulcers Unit 1: Biochemistry and Digestion Stomach – gastric ulcers OBJ 35

Unit 1: Biochemistry and Digestion Cellulose digestion OBJ 35

Where foods are broken down with enzymes Unit 1: Biochemistry and Digestion Where foods are broken down with enzymes OBJ 36, 37

Questions to consider… Unit 1: Biochemistry and Digestion Questions to consider… What is heartburn and why does it hurt? What causes diarrhea? Constipation? What prevents the stomach from being overly acidic? In your house or apartment, what keeps the furnace from overheating the building? Here, what characteristic of life pertains?

Think about the function of each food… Unit 1: Biochemistry and Digestion Think about the function of each food… What would happen if you didn’t eat enough carbs? Carbs are primarily used for what? You would feel tired… You would lose weight because your body is using stored reserves of energy… Slow down digestion because of lack of fiber… What would happen if you didn’t eat enough fat? Some vitamins are fats... Blood clotting, vision, bone growth would be affected… Nervous system function would be impaired…

Think about the function of each food… Unit 1: Biochemistry and Digestion Think about the function of each food… What would happen if you didn’t each enough protein? Every body function would be affected… (No enzymes!!) You might feel tired because you can’t produce enough hemoglobin…

Structure and Function in Digestion Unit 1: Biochemistry and Digestion Structure and Function in Digestion OBJ 38 Mouth Teeth – canines vs. molars Esophagus Tough, elastic connective tissue to stretch Layers of smooth muscle for peristalsis Stomach Muscular walls for churning Mucus lining to protect from acid and protease Small Intestine Long and folded, with villi for lots of absorption Large Intestine Size of cecum depends on diet