Human Systems Chapter 8 - Digestion

Human Systems Unit D Chapter 8 - pgs 240 - 276 Chapter 9 Chapter 10 Chapter 11 Chapter 12

General Knowledge Outcome #1 • Students will: explain how the human digestive system and respiratory exchange energy and matter with the environment 20 - D1.2k 20 - D1.3k 20 - D1.4k 20 - D1.5k

Nutrients, Enzymes & Digestion • Digestive system – Responsible for converting parts of our diet into molecules – Molecules can be taken up & used by cells – Supply body with energy sources

What Do you Know Already? Nutrient

Undergoes Digestion? Yes

Components after Digested

Used by the Body to …

No

Protein

Build structure

Vitamins

Coenzymes; assist enzymes, bind to substrate molecules

Fats Polysaccharides Water

Fatty acid + glycerol

What Do you Know Already? • Make a list of essential nutrients that must be included in every diet • Make a list of the digestive organs that you know of already

Essential Nutrients ( Sec. 8.1 ) • Living things are composed of non-living chemicals • Foods classified into 3 major groups of nutrients: carbohydrates, proteins & lipids • Vitamins & minerals make up smaller amount required • Water is essential though not considered a nutrient

Essential Nutrients ( Sec. 8.1 ) Lipids (Fats)

Nucleic Acids

Proteins Chemicals of Life

Carbohydrates

Vitamins & Minerals

Carbohydrates • A molecule composed of sugar subunits – Contains carbon, hydrogen & oxygen in a 1:2:1 ratio

• Provide fast source of energy – Make up largest component in most diets

Carbohydrates • Human body cannot make carbohydrates – Rely on plants as the source of carbohydrates – Plants convert solar energy to chemical energy • Sound familiar?? • 6CO2 + 6H2O + light energy Æ C6H12O6 + 6O2 • Process known as photosynthesis!!

Carbohydrate Chemistry • Can be single sugar units or polymers of many sugar units – Is a polymer when three or more subunits are linked

• Recall the 1:2:1 ratio and glucose C6H12O6 – Is a hexose sugar Æ six-carbon sugar chain – Also have triose sugars (three-carbon sugar chain) and pentose (five-carbon sugar chain)

• Identify a sugar by the -ose suffix

Carbohydrate Chemistry • Classified according to number of sugar subunits – Monosaccharide - single sugar unit – Disaccharide - joining of 2 sugar subunits – Polysaccharide - carbohydrate composed of >2 sugar subunits

Carbohydrate Chemistry • Disaccharides are formed by dehydration synthesis – Water molecule is removed from two monosaccharide sugars

• Hydrolysis breaks apart one larger molecule into smaller molecules – Water is added and breaks the bond

Dehydration Synthesis

Carbohydrate Chemistry • Plants store carbohydrates as a polysaccharide of multiple glucose subunits – Starch, stored in a helix shape • Amylose - contains up to 1000 or more glucose subunits – 1st carbon in one molecule linked to 4th carbon in next molecule

• Amylopectin - contains between 1000 - 6000 glucose subunits – Has short branching chains between 24-36 unit long, extending from main branch

Carbohydrate Chemistry • Animals store carbohydrates as a polysaccharide called glycogen – Similar to amylopectin, but branched chains only 16-24 glucose subunits long • Excess quantities of carbohydrates stored as fat – Excess intake of carbohydrates under normal circumstances not a good idea

Lipids • Non-polar molecules, insoluble in polar solvents such as water – Think of washing dishes … does oil dissolve in the water?

• Composed of two structural units – Glycerol – Fatty acids • Can be combined by dehydration synthesis

Lipids • Important function is storage of energy – Limited glycogen supplies in most mammals – Once glycogen stores are built up, carbohydrate is converted into fats

Lipids • Also serve as: – – – – –

Key components in cell membranes Cushions for delicate organs in the body Carriers for vitamins A, D, E and K Raw materials for synthesis of hormones Insulation against cold

Lipids - Triglycerides • Formed by union of glycerol and 3 fatty acids – Those solid at room temperature are fats • Saturated Æ only single bonds exist between carbon atoms (most of the animal fats)

– Those liquid at room temperature are oils • Unsaturated Æ double bonds exist between carbon atoms (most of the plant fats) – If one double bond, monounsaturated – If two or more double bonds, polyunsaturated

Lipids - Phospholipids • Phosphate group bonded to glycerol backbone • Negatively charged phosphate group - polar – Polar end soluble in water, non-polar end is nonsoluble

Lipids - Waxes • Long-chain fatty acids joined with long-chain alcohols or to carbon rings – Insoluble in water – Well-suited for waterproof coating on plant leaves, animal feathers and fur

Liposome Technology • Lipids assemble into double-layered spheres approx. the size of a cell – Liposomes

• Can fuse with a cell & deliver contents – Used with cancer fighting drugs

Cholesterol Case Study pg 248 • • •

Low-Density Lipoproteins (LDL) High-Density Lipoproteins (HDL) Trans Fats 1. Why should fat consumption be limited? 2. Differentiate between “good” and “bad” cholesterol 3. What are trans fats? Why are they concerning?

Proteins •

These are not primarily energy compounds, although they can do it

–

•

Different than lipids or carbohydrates

Whenever cells are damaged & need repair, proteins are manufactured –

Also builds structures for new cells

Proteins •

What is composed of protein? – – – –

Cytoplasmic organelles Æ mitochondria, ribosomes Major part of muscles, nerves, skin, and hair Antibodies Enzymes

Proteins •

Composed of building blocks Æ amino acids (20 different kinds) –

A chemical that contains nitrogen - can be linked together – NH2 group - amino group – COOH group - carboxyl group – R group - differentiates one amino acid from another

Proteins • •

Limited number of carbohydrates and lipids Array of proteins is almost infinite – –

•

A small protein may contain only a few amino acids A large protein may have more than 250,000 amino acids

Order and number of amino acids determines the type of proteins

Proteins •

•

Protein eaten is digested, absorbed, and individual amino acids are delivered to the cells Cell rearranges the amino acids as dictated by your genes – –

Joined by a peptide bond between a carboxyl group of one amino acid and the amino group of a second Chain of amino acids (≥3 amino acids) is called a polypeptide

Proteins • •

Body is capable of making most amino acids However must obtain 8 from diet – –

Essential amino acids Æ cannot be synthesized in the body Lack of these leads to specific protein deficiencies and diseases

Structure of Proteins •

Polypeptides folded into three-dimensional shapes – –

Shape or structure determines its function Structure is determined by amino acid sequence •

Change of one amino acid can change entire protein structure

Structure of Proteins •

Four levels of protein structure 1. 2. 3. 4.

Primary Secondary Tertiary Quaternary

Primary Structure •

Unique sequence of amino acids in the chain

Secondary Structure • •

Determined by primary structure Folds & coils occur along chain –

Hydrogen binding pulls chain into coils and pleated sheets

Tertiary Structure • •

Additional folding of the polypeptide chain Occurs due to interactions between R groups

Quaternary Structure • •

Large, globular proteins from 2 or more polypeptides ex. Hemoglobin - contains 4 individual polypeptide chains which combine to form the functional model

Denaturation & Coagulation •

Exposing protein to excess heat, radiation or pH changes will alter its shape – –

•

Physical or chemical factors disrupt bonds and cause changes in configuration May uncoil or assume new shape

Changes physical properties and biological activity - temporary - when removed the proteins return to original state (denaturation)

Denaturation & Coagulation •

Coagulation refers to permanent change in protein shape –

ex. cooking an egg •

Coagulation occurs because no matter how long the egg cools, it never returns to its previous state

Work Check Questions Fill in the following table using your notes and textbook On page 253 answer questions 2, 4, & 5 Work Check Tomorrow

Nutrient Carbohydrates

Lipids

Proteins

Sources

Function in Humans

Enzymes (sec. 8.2) Pages 254 - 258

Reactions in the Cells •

Within cells reactions must occur at relatively low temperatures –

Heat is dangerous, destructive

Reactions in the Cells •

A catalyst is a chemical that increases the rate of chemical reactions without altering the products, or being altered itself

What is an Enzyme? •

A protein catalyst which permits a chemical reaction to proceed at low temperatures –

Regulates reactions occurring in living things

What is an Enzyme? •

•

Lowers activation energy required for reaction to occur Permits reactions to occur at lower temperatures

What is an Enzyme? •

Molecules which enzymes work on are called substrates –

Combines with specific enzymes •

–

•

Lock & Key Model

Are changed during the reactions

Some enzymes need assistance to bind with the substrate –

Cofactors •

–

Inorganic ions

Coenzymes Æ this word should ring a bell; CoA? •

Organic molecules

What is an Enzyme? •

Identified by suffix “-ase” added to name of substrate bonded to – – –

Carbohydrases Proteases Lipases

Factors Affecting Enzymes pH •

Enzymes function best within certain pH ranges –

Example: PEPSIN • •

–

Located in the stomach Functions optimally in areas of low pH

Example: TRYPSIN • •

Located in the small intestine Functions optimally in areas of higher pH (~9)

Factors Affecting Enzymes pH •

Within the digestive tract there are optimal pHs for the enzymes located throughout

Factors Affecting Enzymes Concentration •

• •

Increase number of substrate molecules, increases number of collisions Greater reaction rate Will plateau over time - level off

Factors Affecting Enzymes Temperature

Factors Affecting Enzymes Temperature •

Increasing temperature increases rate of reactions – –

When energy is added, molecules move faster Faster molecules creates greater rate of collision

Factors Affecting Enzymes Temperature •

In humans, peaks at ~37°C –

•

WHY??

Recall denaturation & coagulation conversation – – –

At higher temperatures, proteins change chapes Changes the active site Greater temperature change, greater change in active site = less effective enzyme

Factors Affecting Enzymes Competitive Inhibition • • •

Have similar shape to substrate Compete with substrate for binding site As long as competitor remains bound, substrate cannot bind and the enzyme does not function properly

Regulation of Enzyme Activity •

Metabolic pathways follow particular steps –

•

One step in the chain initiates the next step and so on

Must have a way to regulate the steps –

Called feedback

Regulation of Enzyme Activity •

Feedback inhibition Æ the inhibition of an enzyme in the metabolic pathway by the final product of that pathway

Regulation of Enzyme Activity •

Precursor activity Æ the activation of the last enzyme in a metabolic pathway by the initial substrate

Regulation of Enzyme Activity •

Allosteric activity Æ a change in an enzyme caused by the binding of a molecule

Work Check Questions Page 258

#s 1, 2, 3, 12, 13 These will be taken up tomorrow for marks

Ingestion (Sec 8.3) Pages 259 - 263

The Digestive Process •

Four parts to the digestive process – – – –

Ingestion - taking in of nutrients Digestion - breakdown of complex organic molecules into smaller components; done via enzymes Absorption - transport of nutrients through the body to the cells Egestion - removal of waste from the body

The point of digestive tract… Hydrolyze macromolecules to molecules that are small enough to be absorbed through the gut wall into the blood stream Examples: • Proteins • Carbohydrates • Lipids • Nucleic Acids • Vitamins and minerals small enough to be absorbed directly Adapted by A deBeaudrap from S Ferbey

Evolutionary development of the modern gut

Adapted by A deBeaudrap from S Ferbey

Cnidarians (Hydra) • Gastrovascular cavity – one opening. • Gastrodermis lining of cavity – secretes dig. enzymes for extracell.digestion – have flagellae that mix food and enzymes - have pseudopods that engulf food particles – absorption of digested particles

Adapted by A deBeaudrap from S Ferbey

Adapted by A deBeaudrap from S Ferbey

Earthworm (Lumbricus terrestris) Long straight tube open at both ends. Eats its way through the dirt. • mouth • esophagus • crop (storage) • gizzard: grit filled muscular walled chamber grinds food • intestine – chemical (enzymatic) hydrolysis and absorption into blood. • absorption improved by typhlosole fold increasing surface area • anus Adapted by A deBeaudrap from S Ferbey

Adapted by A deBeaudrap from S Ferbey

Grasshopper • 2 ended long tube • Crop (storage) • Gizzard made of chitin plates for grinding • Specialized mouth parts (modified appendages) for tasting, biting, crushing • Removes nitrogenous waste (uric acid) from animal Adapted by A deBeaudrap from S Ferbey

Grasshopper mouthparts

Adapted by A deBeaudrap from S Ferbey

Grasshopper Digestive Tract

Adapted by A deBeaudrap from S Ferbey

Human digestion • Long highly coiled gut to increase time for digestion/absorption • Outpocketings (glands) off main tube for secretion of enzymes,etc • Part of external environment

Adapted by A deBeaudrap from S Ferbey

Salivary Glands •

Amylase enzymes to break down starches into simpler carbohydrates –

• •

Recall amylose and amylopectin

Lubricates food so it can be swallowed Starch Æ maltose (2 glucose units)

•

Salivary Glands

Detect flavor when: –

Food particles dissolved in saliva penetrate taste buds

Teeth •

Important for physical digestion MASTICATION –

– – –

Incisors specialized for cutting Canines Æ tearing Premolars Æ ginding Molars Æ crushing

In-Class Assignment: 1.Design an experiment to determine if the starch in a chewed cracker has been hydrolyzed to maltose 2.Pencil draw and label the gut from top to bottom: NO TRACING!

Adapted by A deBeaudrap from S Ferbey

Swallowing

• Bolus to pharynx. • Epiglottis – flap which covers the trachea • Soft palate - stops food from entering nasal cavity http://people.eku.edu/ritchisong/epiglottis.gif

Adapted by A deBeaudrap from S Ferbey

Esophagus •

Food must travel from the mouth to the stomach via the esophagus –

Peristalsis Æ rhythmic, wavelike contractions of muscle that move food along the gastrointestinal tract

The initial act of swallowing is a voluntary process, however the movement afterwards is involuntary and controlled by nerves

Stomach

Stomach • Site of food storage and initial protein digestion • Contains 3 layers of muscle – Run in different directions • Allows for churning of food

Stomach • Control of food movement done by sphincters – Allows food to enter but keeps food and acid from being regurgitated – Moves food into the small intestine

Layers of the gut • Mucosa: protective, mucus-secreting cells and glands that secrete digestive enzymes • Submucosa – contains nerve and blood and lymph vessels • Muscularis externa – smooth muslce • Serosa – covers outer surfaces of the digestive tract organs (fibrous) Adapted by A deBeaudrap from S Ferbey

Adapted by A deBeaudrap from S Ferbey

Stomach - Ruminants 4-chambers

ENZYMATIC DIGESTION by gastric juice from gastric pits in stomach wall. GASTRIC JUICE: 1. HCl from parietal cellsÆ denatures protein. Stomach ph = 1-3 is antiseptic 2. Pepsinogen = inactive enzyme from Chief cells: HCl activates pepsinogen into pepsin enzyme – Pepsin enzyme. Æ hydrolyzes proteins into polypeptides 3. Mucus from neck cellsÆ protects stomach wall from pepsin and acid Adapted by A deBeaudrap from S Ferbey

Stomach Lining

Gastric pit cells containing -mucous neck cells (mucus) -parietal cells (HCl) -chief cells (pepsinogen) Adapted by A deBeaudrap from S Ferbey

Pepsin - an Enzyme

Steps to protein digestion pepsin Gastric juice HCl Gastric juice 3-D globular protein

Denatured protein Polypeptide chain

dipeptidase Amino acids Adapted by A deBeaudrap from S Ferbey

Small peptides

Carboxypeptidase, trypsin, aminopeptidase, chymotrypsinm,

Draw a graph showing the effect of pH on pepsin activity • The effect of pH on pepsin activity Pepsin activity (% yield amino acids)

0

Adapted by A deBeaudrap from S Ferbey

pH

7

14

ULCER commonly due to Heliobacter pylori bacteria

Adapted by A deBeaudrap from S Ferbey

Summary: STOMACH FUNCTION? • MECHANICAL BREAKDOWN OF FOOD • DENATURATION OF PROTEINS • HYDROLYSIS OF PROTEINS TO SHORTER PEPTIDES • Stomach stores food What would be the effects of the removal of the stomach and explain why for each effect?

Adapted by A deBeaudrap from S Ferbey

In-Class Assignment: 1.Design an experiment to determine if the starch in a chewed cracker has been hydrolyzed to maltose 2.Pencil draw and label the gut from top to bottom: NO TRACING!

Adapted by A deBeaudrap from S Ferbey

Digestion (Sec 8.4) Pages 264 - 270

Small Intestine •

•

Pyloric sphincter allows passage of food from stomach into the duodenum

Most responsible for absorption of nutrients into bloodstream

Small Intestine • Is ~ 2.5 cm x 6 m in length • Consists of three main segments – Duodenum (pH ~6) – Jejunum (pH ~7-8) – Ileum (pH ~7-8)

Small Intestine • Surface is covered with millions of projects called villi - problems here relates to Celiac disease

Absorption of digested end products • Small intestine is lined with villi which have microvilli to increase surface area for absorption Adapted by A deBeaudrap from S Ferbey

Microvilli on Villi

Small Intestine

Blood Vessels of the Small Intestine

Pancreas • •

Endocrine and exocrine roles Exocrine involved in digestion –

Production of digestive enzymes

Pancreatic Secretions • Trypsin, erepsin, pancreatic lipase & pancreatic amylase

• Bicarbonate- and salt-rich solution secreted into small intestine

Liver & Gallbladder • • •

•

Helps manufacture proteins Synthesizes, stores and metabolizes fats Stores and metabolizes carbohydrates Forms and secretes bile

Liver & Gallbladder •

Bile drains into common bile duct –

•

Joins with cystic duct from gall bladder

Bile drains into the duodenum or is temporarily stored in cystic duct of gall bladder

Liver & Gallbladder • • •

•

Helps manufacture proteins Synthesizes, stores and metabolizes fats Stores and metabolizes carbohydrates Forms and secretes bile

Liver & Gallbladder

Liver & Gallbladder - Problems

Liver & Gallbladder - Problems

• Common bile duct carries secretions from liver and pancreas into small intestine. • So, small intestine contains a. intestinal juice from intestine wall b. bile from liver c. pancreatic juice from pancreas d. food SI is BASIC due to sodium bicarbonate from pancreas Adapted by A deBeaudrap from S Ferbey

Small intestine

Absorption into blood stream By the end of the small intestine, digestion complete: • carbohydrates Æ monosaccarides • fats Æ fatty acids and glycerol • proteins Æ amino acids Now end-products are ready for absorption through the wall of the small intestine into the bloodstream

Adapted by A deBeaudrap from S Ferbey

Absorption of the End Products from the Villi in the Small Intestine Lacteal • takes in partially digested fat droplets, FATTY ACIDS AND GLYCEROL and fat soluble vitamins by endocytosis – into lymph ducts – lymph nodes for screening – returned to general blood circ.

Capillary • Water soluble end products (glu, aa, nucleotides) diffuse through villus epithelium into blood capillary Rich blood from villi Æ hepatic portal veinÆ liver for screening: • excess glucoseÆ into liver glycogen. • excess amino acids Æ deaminated (– NH2 portion becomes urea) remainder becomes fat. Adapted by A deBeaudrap from S Ferbey

Summary of small intestine • Almost all digestion and all absorption of nutrients into the blood is finished by end of S.I. • Remainder entering large intestine is: cellulose, water, dissolved minerals, vitamins, undigestible matter

Adapted by A deBeaudrap from S Ferbey

Large Intestine aka Colon

Large Intestine • Last part of digestive system in vertebrates • Functions to remove water from remaining indigestible food matter – Pass this waste from the body

• Takes 12-25 hours to complete digestion • Can house over 700 species of bacteria

• Cecum and appendix contain cellulose digesting microbes • Vestigal organs in humans - they have no function

Large Intestine

Function of Colon: . • Absorbs water and dissolved minerals into the bloodstream • Constipation – too long in the colon (no fibre or water) • Diarrhea – not enough time in the colon.

Adapted by A deBeaudrap from S Ferbey

Egestion • Rectum: very muscular, last 10 cm, 2 inner and 2 outer sphincters. • Stretch reflex (fibre, water) in the large intestine causes peristaltic wave Æegestion (defecation)

Adapted by A deBeaudrap from S Ferbey

Coprophagy • In animals which do not have a complex ruminant system like cattle and sheep • First round - soft fecal pellets of partially digested food • Second round - harder, very little nutrient content

HORMONAL control of digestion: Enzyme release is controlled by hormones HORMONE

The STIMULUS for production of the hormone is

GASTRIN

PROTEIN IN STOMACH WALL STOMACH ; Stretching stomach muscles

GASTRIC JUICE FROM gastric PITS

SECRETIN

PRESENCE OF ACID IN DUODENUM

DUODENAL WALL

Stimulates secretion of PANCREATIC JUICE from pancreas

CHOLECYSTO KININ (CCK)

FAT IN SMALL INTESTINE

DUODENAL WALL

STIMULATES GALL BLADDER TO RELEASE BILE

Adapted by A deBeaudrap from S Ferbey

SITE OF PRODUCTION of hormone

Hormone causes this effect…

Human Systems Unit D Chapter 8 Chapter 9 - pages 280 - 309 Chapter 10 Chapter 11 Chapter 12