Understanding The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gut The pancreas secretes enzymes into the lumen of the small intestine ID: 777728
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Slide1
6.1 Digestion and Absorption
Understanding:The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gutThe pancreas secretes enzymes into the lumen of the small intestineEnzymes digest most macromolecules in food into monomers in the small intestineVilli increase the surface area of epithelium over which absorption is carried outVilli absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Applications:Processes occurring in the small intestine that result in the digestion of starch and the transport of the products of digestion to the liver
Skills:Production of an annotated diagram of the digestive systemIdentification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph
Nature of science:
Use models as representations
of
the real world: dialysis tubing can be used to model absorption in the intestine
Slide2The Digestive System
How do we get from this…
…to this?
Slide3Key stages
Ingestion – Eat the foodDigestion – Food converted into smaller molecular formAbsorption – Small molecular forms absorbed through cells of digestive system and pass into blood system Transport – Circulatory system delivers small molecular nutrients to body cellsElimination – Undigested material/waste leaves body
Slide4You are moving house…
Digestion – why?
Slide5You are moving house…
Digestion – why?
Slide6Break down larger molecules that cannot be absorbed into smaller molecules that can
Copy and complete the table:Molecule ingestedMolecular form after digestion
ProteinsLipids (triglycerides)Carbohydrates (polysaccharides and disaccharides)Nucleic acids (DNA and RNA)Digestion – why?
Slide7Break down larger molecules that cannot be absorbed into smaller molecules that can
Copy and complete the table:Digestion – why?
Molecule IngestedMolecular form after digestionProteinsAmino acidsLipids (triglycerides)Glycerol and fatty acidsCarbohydrates (polysaccharides and disaccharides)MonosaccharidesNucleic acids (DNA and RNA)Nucleotides
Slide8Create an annotated diagram of the digestive system:
Role of the digestive systemOrgans MouthEsophagusStomachSmall intestinePancreasLiverGall bladderLarge intestineAnusWhat does each organ do?
The process of peristalsisStructure of digestive system
Skills:Production of an annotated diagram of the digestive systemBiodigital human
Slide9The Digestive System
The mouth contains teeth.
These chew the food and break it into smaller pieces.The tongue pushes food to the back of the mouth so you can swallow it.Enzyme (amylase) in saliva
Slide10The Digestive System
The oesophagus, or food pipe, joins the mouth and the stomach.
Food is squeezed along this tube into the stomach: peristalsis
Slide11The Digestive System
The stomach is a bag
of acid.The hydorchloric acid in the stomach, and enzymes break down the food even more.Bacteria and other pathogens killed
Slide12The Digestive System
Pancreas secretes lipase, amylase and protease (enzymes)
Slide13The Digestive System
Liver secretes bile
Creates optimum pH for enzymesHelps to break up lipidsGall bladder stores the bile
Slide14The Digestive System
In the small intestine, the broken down food gets absorbed into the blood so the body can use it.
Main area for digestion
Slide15The Digestive System
The large intestine is about 1.5 metres long.
In the large intestine, the body absorbs a lot of water back from the digested food.
Slide16The Digestive System
At the end of the digestive system, the left overs that the body can’t use leaves the body through the anus when you go to the toilet.
Faeces is held in the rectum before.
Slide17Can you swallow if you are upside down?
Slide18Peristalsis
Food does not move through your digestive system using gravityMuscles control the movement of your food throughout your digestive systemOesophagus, stomach and intestines(Autonomic nervous system – you are unaware)
Understanding:
The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gut
Slide19Small Intestine
Draw the diagram:Label the:LumenCircular smooth muscleLongitudinal smooth muscleVilli
Understanding:
The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gut
Slide20Enzymes
Specific enzymes for specific foodsAct as catalysts for reactions (reactions require less energy when there are enzymes)Throughout digestive system – process starts in the mouthFocus on pancreas and small intestine
Understanding:The pancreas secretes enzymes into the lumen of the small intestine
Slide21Round 1: Pancreas
Understanding:
The pancreas secretes enzymes into the lumen of the small intestineEnzymeSubstrateAction
AmylaseLipasePhospholipaseProtease
Slide22Round 1: Pancreas
Understanding:
The pancreas secretes enzymes into the lumen of the small intestineEnzymeSubstrateAction
AmylaseStarchBreaks down starch to maltoseLipaseTriglyceridesBroken down to fatty acids and glycerolPhospholipasePhospholipidsBroken down to fatty acids, glycerol and phosphateProtease/endopeptidasesProteins/polypeptidesBroken down to shorter peptides Some of these products are still too big to be absorbed so need to be broken down more by different specific enzymes
Slide23Round 2: Wall of small intestine
Understanding:
Enzymes digest most macromolecules in food into monomers in the small intestineEnzymeSubstrateAction
NucleaseMaltaseLactaseSucraseExopeptidasesDipeptidases
Slide24Round 2: Wall of small intestine
Understanding:
Enzymes digest most macromolecules in food into monomers in the small intestineEnzymeSubstrateAction
NucleaseDNA/RNABreaks down into nucleotidesMaltaseMaltoseBreaks down into glucoseLactaseLactoseBreaks down to glucose and galactoseSucraseSucroseBreaks down into glucose and fructoseExopeptidasesPeptidesBreak down into single amino acids (leaves dipeptides)DipeptidasesDipeptidesBreak
down into amino acids
Slide25Super fun fact: How long is this boat?
Slide26Undigestables
Food takes hours to pass through the long small intestineMany molecules remain undigestedHuman body cannot synthesize the necessary enzymesE.g. Cellulose: passes on to large intestine as the main component of faeces
Understanding:
The pancreas secretes enzymes into the lumen of the small intestine
Slide27Four layers:
Serosa (outer coat)Muscle layers Sub-mucosa (blood and lymph vessels)Mucosa (Lining of small intestine)1
234Small Intestine
Skills:Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph
Slide28Small Intestine
Draw a cross section of an intestinal villus.Label each part and describe the functionEpitheliumMicrovilliCapillariesLactealGoblet cells
Understanding:
Villi increase the surface area of epithelium over which absorption is carried out
Slide29Villi summary
Key points:Epithelium is one cell thickMany villi with microvilli = large surface areaGood blood supplyLarge amounts of mitochondria
Understanding:
Villi increase the surface area of epithelium over which absorption is carried out
Slide30Surface Areas
A small intestine that is 5m long and 2.5cm diameter. Surface area:No villi= 0.5m2With villi = 200m2
Understanding:Villi increase the surface area of epithelium over which absorption is carried out
Slide31Spot the Difference
Coeliac small intestineSome villi are lost, so the individual cannot absorb the products of digestion properly
Why could this make a coeliac thin?
Slide32Passive
Simple diffusionFollow concentration gradientSmall molecules/non-polar molecules
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide33Passive
Facilitated diffusionDown concentration gradientProtein also used due to size/polarity
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide34Active
Active transportUses membrane pumpsMove against concentration gradientUse ATP
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide35Active
Endo/exocytosisMolecules trapped in an infolding of the membranePass through to the other side as a vesicleRequires ATP
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide36Absorption in the villi
PASSIVE (No ATP):Simple diffusionFacilitated diffusionACITVE (ATP used):Active transportExocytosis
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitamins
Different methods of membrane transport are required to absorb different nutrients
Slide37Triglycerides
INTO VILLUS MEMBRANESimple diffusion (Passive)Facilitated diffusion (Passive)OUT OF VILLUS MEMBRANEExocytosis (Active)
Methods of absorption
Slide38Triglycerides
Must be digested before being absorbedProduces fatty acids and a monoglyceride
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide39Triglycerides
3. Can be absorbed by simple diffusion as they can pass between phospholipids in plasma membrane
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide40Triglycerides
4. Fatty acids also absorbed by facilitated diffusion using fatty acid transporters (proteins in membrane of microvilli)
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide41Triglycerides
5. Once through the membrane and inside the epithelium cells, fatty acids are combined with monoglycerides to produce triglycerides, which cannot diffuse back again
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide42Triglycerides
6. These triglycerides join with cholesterol to form droplets. 7. These then become coated in phospholipids and protein
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide43Triglycerides
8. These lipoproteins are released from epithelial cells into either the capillary or lacteal by exocytosis
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide44Triglycerides
INTO VILLUS MEMBRANESimple diffusion (Passive)Facilitated diffusion (Passive)OUT OF VILLUS MEMBRANEExocytosis (Active)
Methods of absorption
Slide45Glucose
Active transport (Active)Facilitated diffusion (Passive)
Methods of absorption
Slide46Glucose
1. Glucose cannot pass through the plasma membrane by simple diffusion because it is polar (therefore hydrophilic)
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide47Glucose
2. Sodium potassium pumps pump sodium ions by active transport from the cytoplasm inside the villus to the intestinal lumen. Pumps potassium ions the other way. Sodium concentration builds up.
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide48Glucose
3. Sodium glucose co-transporter proteins transfer a sodium ion and glucose molecule together into epithelium cells. (Facilitated diffusion = passive)
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide49Glucose
4. Glucose channels allow glucose to move by facilitated diffusion into the villus and on into the blood capillaries.
Understanding:Villi absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Slide50Glucose
Active transport (Active)Facilitated diffusion (Passive)
Methods of absorption
Slide516.1 Digestion and Absorption
Understanding:The contraction of circular and longitudinal muscle layers of the small intestine mixes the food with enzymes and moves it along the gutThe pancreas secretes enzymes into the lumen of the small intestineEnzymes digest most macromolecules in food into monomers in the small intestineVilli increase the surface area of epithelium over which absorption is carried outVilli absorb monomers formed by digestion as well as mineral ions and vitaminsDifferent methods of membrane transport are required to absorb different nutrients
Applications:Processes occurring in the small intestine that result in the digestion of starch and the transport of the products of digestion to the liver
Skills:Production of an annotated diagram of the digestive systemIdentification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph
Nature of science:
Use models as representations
of
the real world: dialysis tubing can be used to model absorption in the intestine
Slide52Modelling the small intestine
Write a simple method.How can we use dialysis tubing to model absorption of digested food in the intestine?TitleHypothesisEquipmentMethodWhy is this a good model? Why could it be a bad model?
You will not complete this as an experiment
Nature of science:Use models as representations of the real world: dialysis tubing can be used to model absorption in the intestine