Digestive System (Extended Response) Flashcards
Outline the process of digestion and absorption of starch. (4 marks)
-Salivary amylase in the mouth or pancreatic amylase in the small intestine break down starch
-Product is disaccharides/ maltose
-Maltase digests disaccharides into monosaccharides
-Monosaccharides/ glucose is absorbed in the small intestine
-Villi increase surface area of intestinal epithelium for greater absorption.
-Monosaccharides are absorbed by co-transport/ active transport into intestinal cell or by facilitated diffusion into the blood from the intestinal cell
Explain the adaptations of the small intestine to its function. (7 marks)
-small intestine is where nutrients are absorbed into the bloodstream
-very long to maximize absorption
-lined with (smooth) muscle to allow for the mixing/ and moving of digested food
-muscles are circular and longitudinal that perform peristalsis
-pancreas and gall bladder secrete substances into the small intestine to aid digestion
-contain villi, to increase surface area
-villi have microvilli to increase surface area even more;
-villi absorb products of digestion/mineral ions/vitamins/glucose;
-dense capillary network rapidly transports absorbed products
-lacteal absorbs lipids from the intestine (into the lymphatic system)
-most of the chemical digestion (into monomers) occurs in small intestine
Describe the structure of starch. (5 marks)
-starch is a carbohydrate
-formed by carbon, hydrogen and oxygen
-it is a polymer/chain/polysaccharide formed from monosaccharides/simple sugars/glucose
-linked together by condensation/dehydration
-consists of amylose and amylopectin
-amylose is a long chain/unbranched
-amylopectin is branched
Describe how amino acids could reach the liver from the moment a person takes a bite. (7 marks)
-food is mechanically/physically digested in the mouth through chewing
-mixed with saliva (to form the bolus) in mouth
-moved through esophagus/peristalsis
-proteins digested in the stomach (pepsin)
-pancreas secretes enzymes into lumen of small intestine
OR
(endo)peptidases/trypsin) are secreted by pancreas
-enzymes digest macromolecules to monomers
OR
endopeptidases digest polypeptides to peptides/amino acids
-villi of small intestine absorb amino acids
-amino acids carried to blood capillaries
-blood (capillaries) carry amino acids to (hepatic portal) vein/blood vessel going to liver
-amino acids absorbed by active transport/protein pumps in the villi
Outline how proteins are digested and the products of protein digestion absorbed in humans. (4 marks)
-digested by peptidases/proteases
pepsin/pepsinogen/endopeptidase secreted by stomach (lining)/digests proteins in stomach
-pancreas secretes/pancreatic juice contains endopeptidase/trypsin/peptidase
-endopeptidase digest proteins/polypeptides to shorter chains of amino acids/shorter peptides
-amino acids absorbed by active uptake/transport in small intestine
-villi increase the surface area for absorption
-absorbed into bloodstream/into capillaries
Outline the role of amylase in digestion in humans.
(4 marks)
-amylase is an enzyme secreted by salivary glands/pancreas
-active/released into the mouth/small intestine
-acts on starch/polysaccharides
-breaks «glycosidic» bond by hydrolysis/adding water
-converts insoluble/large molecule to soluble/small molecules
-product is maltose/disaccharide/sugar molecule
Explain the action of enzymes in digestion and the different roles of at least two named enzymes that are produced in the pancreas. (8 marks)
-enzymes catalyse/speed up chemical reactions/lower the energy needed
-have specific active sites to which specific substrates bind
-enzyme catalysis involves molecular motion and the collision of substrates with the active site
-enzymes break macromolecules into monomers/smaller molecules indigestion
-smaller molecules/monomers more readily absorbed
-«pancreas» secretes enzymes into the «lumen of» small intestine
-small intestine has an alkaline pH
-enzymes have maximum action at specific pHs
or enzymes can be denatured at other pHs
-amylase breaks down starch into sugars/disaccharides
-lipase breaks lipids/triglycerides into monoglycerides/fatty acids and glycerol
-endopeptidase/protease breaks «peptide» bonds in proteins/polypeptides
-accept any other valid pancreatic enzyme, substrate and product
Explain how the timing of secretion is controlled, with reference to the content of the gastric juice. (4 marks)
-nervous and hormonal control
-impulses from sight/smell of food stimulates brain to send nerve impulses
-impulses cause cells in stomach lining/ parietal cells to secrete acid/gastric juice
-food entering the stomach stimulates the chemoreceptors/stretch receptors
-chemoreceptors/stretch receptors send impulses to the brain
-vagus nerve/brain sends a nervous impulse to endocrine cells in wall of stomach
-endocrine cells release gastrin into the blood
-gastrin induces the release of gastric juice to digest proteins
-secretin/somatostatin decrease gastrin secretion
Describe the processes involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine. (4 marks)
-«simple» diffusion of nutrients along/down a concentration gradient
-example of simple diffusion: fatty acids
-facilitated diffusion of nutrients involves movement through channel proteins
-example of nutrient for facilitated diffusion: fructose
-active transport of nutrients against a concentration gradient / involving protein pumps
-examples of active transport: iron ions/glucose/amino acids -endocytosis/ by means of vesicles
-example of nutrient for endocytosis: cholesterol in lipoprotein particles
Discuss the causes and consequences of malnutrition in humans. (4 marks)
Causes:
-deficiency in an essential nutrient
-excess of a nutrient
-may be due to social/socioeconomic/political factors
-unbalanced diet can result from malfunction of the hypothalamus
Consequences:
-starvation can lead to breakdown of body tissues
-obesity can lead to other health problems/diabetes/CHD
-anorexia can lead to organ failure/serious health problems
-consequence of a named excess/deficiency
Explain the stages involved in the recycling of erythrocytes by the liver. (4 marks)
-phagocytosis of erythrocytes by Kupffer cells
-hemoglobin is split into globin and heme group
-globin is hydrolysed to amino acids
-amino acids used in protein synthesis
-heme group broken down into iron and bilirubin
-iron is (carried back to the bone marrow to be) used for production of new erythrocytes
-bilirubin is secreted into bile
Explain how the small intestine moves, digests and absorbs food. (8 marks)
-contraction of muscle «layers»/peristalsis helps move food
-peristalsis/muscle contractions mix food with intestinal enzymes
-enzymes digest macromolecules into monomers
-pancreatic enzymes/amylase/lipase/endopeptidase «chemically» digest food in«lumen of» small intestine
-«pancreatic» amylase digests starch
-lipases digest lipids/fats/triglycerides
-endopeptidases/dipeptidases digest proteins/polypeptides
-bile/bicarbonate secreted into the small intestine creates favorable pH for enzymes or
bile emulsifies fat
-some final digestion into monomers is associated with epithelial cells/epithelium «of small intestine»
-mucosa layer/inside surface/lining of small intestine contains villi/finger-like projections
-villi/microvilli increase surface area for better absorption
-villi absorb products of digestion/monomers/mineral «ions»/vitamins
-glucose/amino acids enter blood «capillaries»
-absorption involves active transport/diffusion/facilitated diffusion
-different nutrients are absorbed by different transport mechanisms
Outline how leptin controls appetite. (3 marks)
-leptin suppresses/inhibits appetite
-is secreted by adipose tissue/fat «storage» tissue
-level is controlled by amount of adipose tissue/«ongoing» food intake
-leptin targets cells in hypothalamus/appetite control centre in brain
-causes hypothalamus/control centre in brain to inhibit appetite
-if amount of adipose tissue increases, blood leptin concentration rises
Explain the process of erythrocyte and hemoglobin breakdown in the liver.
(6 marks)
-erythrocytes rupture when they reach the end of their life span / after 120 days
-«erythrocytes» absorbed by phagocytosis
-Kupffer cells ingest/take in erythrocytes
-Kupffer cells in sinusoids in the liver
-hemoglobin split into globin and heme groups
-amino acids from the globin are recycled
-heme group is further broken down into iron and bilirubin / bile pigment
-iron stored in liver / transported to bone marrow/spleen
-bilirubin released into alimentary canal/becomes part of bile
