Human Systems Chapter 8 - Digestion

Human Systems

Unit DChapter 8 - pgs 240 - 276

Chapter 9Chapter 10Chapter 11Chapter 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 - D1.3k20 - 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?

Water

Polysaccharides

Fatty acid + glycerolFats

Coenzymes; assist enzymes, bind to

substrate molecules

Vitamins

Build structureProtein

NoYes

Used by the Body to …Components after Digested

Undergoes Digestion?Nutrient

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 )

Proteins

Carbohydrates Vitamins & Minerals

NucleicAcids

Lipids (Fats)

Chemicalsof Life

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

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 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


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

subunits


• 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


• 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


• 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 only single bonds exist between carbon atoms (most of the animal fats)

– Those liquid at room temperature are oils• Unsaturated 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 non-soluble

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” cholesterol3. 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 mitochondria, ribosomes– Major part of muscles, nerves, skin, and hair– Antibodies– Enzymes

Proteins• Composed of building blocks 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 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. Primary2. Secondary3. Tertiary4. 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 polypeptidechains which combineto form the functionalmodel

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 QuestionsFill in the following table using your notes and textbook

On page 253 answer questions 2, 4, & 5

Work Check Tomorrow Proteins

Lipids

Carbohydrates

Function in Humans

SourcesNutrient

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 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)


pH

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


Concentration• Increase number of

substrate molecules, increases number of collisions

• Greater reaction rate• Will plateau over time

- level off


Temperature


Temperature• Increasing temperature increases rate of reactions

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


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


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


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


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


• Allosteric activity 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


• 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

Cnidarians (Hydra)



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



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


Grasshopper mouthparts


Grasshopper Digestive Tract


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


Salivary Glands• Amylase enzymes to

break down starches into simpler carbohydrates

– Recall amylose and amylopectin

• Lubricates food so it can be swallowed

• Starch 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 tearing

– Premolars ginding

– Molars crushing

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!


In-Class Assignment:

Swallowing

http://people.eku.edu/ritchisong/epiglottis.gif

• Bolus to pharynx.• Epiglottis – flap which covers the

trachea• Soft palate - stops food from entering

nasal cavity


Esophagus

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

– Peristalsis 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 churningof 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)



Stomach - Ruminants

4-chambers

ENZYMATIC DIGESTION by gastric juice

from gastric pits in stomach wall.

GASTRIC JUICE:1. HCl from parietal cells denatures

protein. Stomach ph = 1-3 is antiseptic

2. Pepsinogen = inactive enzyme from Chief cells: HCl activates pepsinogen into pepsin enzyme

– Pepsin enzyme. hydrolyzes proteins into polypeptides

3. Mucus from neck cells protects stomach wall from pepsin and acid


Stomach Lining

Gastric pit cells containing

-mucous neck cells (mucus)

-parietal cells (HCl)

-chief cells (pepsinogen)


Pepsin - an Enzyme

Steps to protein digestion

3-D globular protein Denatured protein

Polypeptide chain

Small peptidesAmino acids

HCl

pepsin

Gastric juice

Gastric juice

Carboxypeptidase, trypsin, aminopeptidase, chymotrypsinm,

dipeptidase


Draw a graph showing the effect of pH on

pepsin activity

• The effect of pH on pepsin activity

pH

Pepsin activity

(% yield amino acids)

0 7 14


ULCERcommonly due to

Heliobacterpylori bacteria


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?


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!


In-Class Assignment:

Digestion (Sec 8.4)

Pages 264 - 270

Small Intestine• Most responsible for

absorption of nutrients into bloodstream

• Pyloric sphincter allows passage of food from stomach into the duodenum

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


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 containsa. intestinal juice from intestine wallb. bile from liverc. pancreatic juice from pancreasd. food

Small intestine

SI is BASIC due to sodium bicarbonate from pancreas


Absorption into blood stream

By the end of the small intestine, digestion complete:• carbohydrates monosaccarides• fats fatty acids and glycerol• proteins amino acids

Now end-products are ready for absorption through the wall of the small intestine into the bloodstream


Absorption of the End Products from the Villi in

the Small IntestineLacteal• 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 hepatic portal vein liver for screening:

• excess glucose into liver glycogen. • excess amino acids 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, un-digestible matter


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.


Egestion• Rectum: very muscular, last 10 cm, 2 inner and 2

outer sphincters.• Stretch reflex (fibre, water) in the large intestine

causes peristaltic wave egestion (defecation)


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

STIMULATES GALL BLADDER TO RELEASE BILE

DUODENAL WALLFAT IN SMALL INTESTINE

CHOLECYSTOKININ (CCK)

Stimulates secretion of PANCREATIC JUICE from pancreas

DUODENAL WALLPRESENCE OF ACID IN DUODENUM

SECRETIN

GASTRIC JUICE FROM gastric PITS

STOMACH WALLPROTEIN IN STOMACH ; Stretching stomach muscles

GASTRIN

Hormone causes this effect…

SITE OF PRODUCTION of hormone

The STIMULUS for production of the hormone is

HORMONE


Human Systems

Unit DChapter 8

Chapter 9 - pages 280 - 309Chapter 10Chapter 11Chapter 12

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Human Systems Chapter 8 - Digestion