Why do we eat? Biology 11

Why do we eat? Cellular Respiration (how we get energy) This energy comes from the nutrients we get from eating Including: Proteins Carbohydrates Fats Vitamins Minerals

Proteins

Proteins Defined Key “worker molecules” are required in nearly every function that your body completes. Made up of amino acids in a chain (50 to 2000!)

Amino Acids Contains Nitrogen (N) Required for life

Amino Acids There are 20 amino acids required by the human body 10 essential amino acids Our bodies cannot produce them. We must get them from our foods. 10 non-essential amino acids Our bodies can produce them

Protein Structure Proteins= chains of amino acids Broken down by enzymes

Carbohydrates

Carbohydrates Used by your body to generate glucose (sugar) to provide you with energy to do stuff Two types: Simple Sugars no modifications needed Complex Sugars: Starch and Dietary Fiber Must be broken down before they can be used

Simple sugar structure =

Complex Sugars Chains of simple sugars Broken down by enzymes

Fats (Lipids)

Purpose of Fats (Lipids) Heat insulation Energy Storage Provides production of reproductive organs in women

Types of lipids = Cis fats = good fats = Trans fats = bad fats

Types of lipids Cholesterol and other steroids are also lipids

Breakdown of fats Fats must first be broken down into smaller droplets emulsification of fats Due to their polar nature. Not soluble in water Secondly, digested by enzymes

Enzymes break down these componets

A closer look at the chemistry The Digestive System A closer look at the chemistry

What is the point of digestion? To break down protein, carbohydrates, and fats such that they can pass through cell walls by diffusion, and be absorbed into the body.

The Digestive Track

Parts of the digestive system: The Mouth

Parts of the Mouth Teeth – a variety of teeth for consuming different foods Tongue- detects taste Hard palette – the front of the roof of the mouth Soft palette- the back of the roof of the mouth Uvula- soft tissue that hangs from the soft palette; blocks of nose during ingestion Salivary Glands- secrete saliva

Mouth Function Two types of digestion: Mechanical: Chemical: Requires chewing with your teeth Chemical: Requires the use of enzymes secreted by salivary glands

Mouth Function Continued Two purposes of saliva: To lubricate food, Allowing it to be swallowed easily Dissolving food particles = taste To break down starches (complex carbohydrates) Amylase enzymes

Mouth Function Continued Preventative Measures... Uvula: Attached to the soft palettes of your mouth roof. Blocks food from entering the nasal cavity during swallowing Epiglottis: Covers the wind pipe during swallowing to prevent food from entering

The Pharynx The “throat” area of the digestive tract The esophagus and trachea both branch off of it Receives food from the mouth Directs the food down the esophagus

The Esophagus= Food Pipe Pathway of food from mouth to stomach Diameter of a quarter Peristalsis Waves of rhythmic contractions of smooth muscles caused by the stretching of the esophagus by bolus Bolus=moistened lump of food Involuntary (happens automatically)

Ingestion Food is moved to the back of mouth by tongue Involuntary reflex is triggered to close off wind pipe Peristalsis quickly takes the food down the esophagus

Don’t let it come back up! The esophagus contains two values: The upper esophageal sphincter Allows food to enter the digestive track The lower esophageal sphincter Prevents stomach contents from “coming back up”

Into the Pit :The Stomach Bolus enters the stomach from the esophagus Muscular walls contract Churning and mixing the bolus with gastric fluids

The Stomach: Gastric Fluids Mucus –protects stomach lining from its own acid Hydrochloric Acid (HCl): (pH 1 – 3) Kills bacteria and Converts an enzyme called pepsinogen into pepsin Pepsin digests proteins

Mechanical Digestion in the stomach As the stomach churns, it mechanically breaks down molecules of Proteins Carbohydrates & fats Into more easily digested molecules. Fats require the most mechanical digestion at this stage

Exiting the Stomach Chyme = mixture of food and gastric fluids After 2 to 3 hours: foods are at a highly soluble level and a hydrogen ion concentration of a certain level is present. The pyloric sphincter opens and chyme is released into the small intestine

What leaves when? Fluids empty quicker then carbohydrates Carbohydrates empty quicker then proteins Proteins empty quicker then fats

Test your knowledge! Food enters the mouth What are the two types of digestion? Mechanical digestion by teeth Chemical digestion by salivary amylase (digests starches) Once food is swallowed it is called: Bolus It travels down the esophagus due to involuntary muscular contractions known as: peristalsis Food enters the stomach and is mixed with gastric fluids for 2 to 3 hours. What is digested here? Proteins Other materials are made more _________ in the stomach: Soluble At this point, the digesting food is called: Chyme and exits to the small intestine via the ? Pyloric sphincter

Enter the Small Intestine

Small Intestine Long (7 meters) and narrow (2.5 cm diameter) Villi increase its surface area Most digestion occurs here Most digestion occurs in the first 30 cm, called the duodenum, Pancreas, liver, and gall bladder release secretions (juices/enzymes) into this area for digestion (chemical)

Signal to the accessory organs Stomach acid entering the duodenum causes prosecretin to become the hormone: secretin Secretin travels through the bloodstream and signals: The pancreases to release pancreatic juices The gallbladder and liver to release bile

Pancreatic Juices and Bile Pancreatic juices and bile are both alkaline solutions (Bicarbonate) The release of these basic solutions, cause the pH of the small intestine to rise from 2.0 to 9.0. This inactivates the stomach acids H+ + OH- H2O

Pancreatic Juices- Proteins The pancreatic juices contain trypsinogen, an enzyme In the small intestine enterokinase converts trypsinogen to trypsin. Trypsin further breaks down proteins The pancreas also releases erepsins erepsins complete the digestion of proteins into amino acids (which the body can use!)

Pancreatic Juices -Carbohydrates The pancreatic juices also contain amylase enzymes: Pancreatic amylase converts starch into maltose (a type of sugar) Maltase (an enzyme) is released from the intestinal cell walls. Converts maltose into glucose (the smallest sugar)

Pancreatic Juices- Lipids Finally, the pancreatic juices contain lipases (enzymes) Lipases break down lipids (fats) into fatty acids and glycerol

Recap the duodenum Upon entry of acidic juices: From the pancreas: Prosecretinsecretin Secretin goes to the pancreas Pancreas, liver and gall bladder release basic solutions which neutralize the small intestine From the pancreas: Enzyme Conversion trypsin ProteinPeptides erepsin PeptidesAmino Acids Pancreatic amylases Starchmaltose Lipase Fatglycerol + fatty acids

The liver and gall bladder The liver has two main functions: To filter and separate waste from nutrients Store glucose and other nutirents To produce bile Bile=Water, bile salts, fats, cholesterol Bile is stored and concentrated in the gall bladder. Moved from the liver to gall bladder through bile ducts Bile is released into the stomach to turn fats into fatty acids during digestion.

The Small Intestine Continued Three Sections: Duodenum Digestion of foods Jejunum Absorption of carbohydrates and proteins by diffusion Ileum Absorption of fats, vitamins, minerals, and other nutrients by diffusion Absorption of enzymes to be “recycled” by diffusion

Absorption in the small intestine =Villi Small intestine covered in villi throughout Coating of capillary beds allows for easy absorption & quick transport of nutrients to the liver

Into the large intestine

What goes into the large intestine.... Waste contains lots of water. Water needs to be absorbed back into the body The ascending colon and transverse colon removes most of this moisture The descending colon stores faeces until their excretion

....Must come out! The rectum The anus Last 5 cm of the large intestine BREIFLY stores faeces The anus A ring of muscles (sphincter) at the end of the digestive track, forming the external opening through which waste is expelled Peristaltic contractions throughout the colon and contraction of abdominal muscles cause defecation

Test your knowledge Starch

Test your knowledge Villi

Test your knowledge lipases

Test your knowledge

Test your knowledge Pancreatic amylases

Fatglycerol + fatty acids Test your knowledge Fatglycerol + fatty acids

Test your knowledge Jejunum

Test your knowledge Bile

Test your knowledge Peristalsis

Test your knowledge Mechanical Digestion

Test your knowledge Descending Colon

Test your knowledge Gall Bladder

Test your knowledge Uvula

Test your knowledge Amino Acids

Test your knowledge Maltase

Test your knowledge Secretin

Test your knowledge Fats