BIOL125 - Feeding and Digestion

  • Created by: Katherine
  • Created on: 19-05-16 12:12
What do process of life require?
Energy and raw material
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What is an autotroph?
Something that can subsit on inorganic nutrients alone (self sustaining) whereas heterotrophs require complex organic compounds in their diet.
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What do heterotrophs require?
They require complex organic compounds from other organisms.
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What are the types of nutrient required?
Carbohydrates, Lipids, Proteins, Vitamins, Inorganic salts and water
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Why do we need lipids?
We need them to make cell membranes.
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Why we need proteins?
For structural components like collagen and elastin.
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Why do we need vitamins?
They are co-factors for enzymes
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Why do we need water?
It is a solvent
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What are the different functions of water?
To act as a solvent for transportation, for hydrostatic support, for evaporative cooling, and as a cleaning agent.
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How many essential amino acids are there, and what are they?
8 - Trp, Met, Val, Thr, Phe, Leu, Ile, Lys - These must be obtained in the diet as we can't make them
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How many calories can a heavy manual working man have?
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How many calories can a moderately worknig man have?
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How many calories can a light working man have?
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What are the four basic digestive processes?
Digestion, absorption, motility and secretion
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What is digestion?
It is the physical and chemical breakdown of food
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What is absorption?
Transport of digestive end products in to bloodstream
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What is motility?
It is peristaltic activity of muscle propelling food along GI tract. We have accessory glands which secrete things into the lumen of the GI tract
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What is secreton?
Transport of digestive fluids into the GI tract
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What are the accessory glands?
Salivary glands, pancrease and liver and gallbladder
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What is the function of the Pharynx?
Conduction of food to esophagus
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What is the function of the stomach?
Mechanical breakdown of food;secretion of acid, pepsiongen and intrinsic factor; initiation of chemical digestion of proteins by pepsin; secretion of gastrin into blood stream; transforamtion of food into chyme
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What is the function of the small intestine?
Chemical digestion of all nutrient classes by pancreatic enzymes and membrane bound enzymes; absorption of digestive end products, water, ions and vitamins; secretion of enterogastrones into blood stream. Secretion of bicarbonate rich fluid
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What is the function of the colon?
Absorption of ions and water; transformation of chyme into feces; storage of feces.
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What is the function of the rectum?
Storage of feces prior to elimination
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What is the function of the anus?
Control of defecation
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What is the function of the salivary glands?
Secretion of saliva (contains amylase, bicarbonate, and lysozyme)
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What is the function of the pancreas?
Secretion of pancreatic juicss (contains digestive enzymes and bicarbonate)
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What is the function of the liver?
Secretion of ble (contains bile salts and bicarbonate); processing of absorbed nutrients
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What is the function of the gall bladder?
Storage and concentration of bile
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What does the general structure of the GI tract consist of?
Duct of accessory gland, lumen, mucosa, submucosa, muscularis, serosa, Nerve plexus
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What does the mucosa consist of?
Mucuous membrane, lamina propria (connective tissue, capillaries, nerves, lymphoid tissue) and muscularis mucosae
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What type of cells make up the mucous membrane?
Epithelial cells or enterocytes which include absorptive cells, exocrine cells, goblet cells (secret mucus) and endocrine cells
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What is saliva secreted by?
It is secreted by salivary glands
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What does saliva contain?
Salivary amylase (digests glycogen and starch) and lingual lipase
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What are the other functions of saliva?
Lubrication (mucus), buffering and diluting noxious substances, antibiotic action (lysozyme, lactoferrin), taste, cleans teeth, fluoride/calciium uptake into teeth.
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What does the Oesphagus do?
It is a muscular tube the connects the pharynx to the stomach.
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The upper and lower esophageal sphincters are usually closed, but back flow can occur, what does this result in?
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The upper 1/3 has what type of muscle?
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The lower 2/3 has what type of muscle?
Smooth muscle
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The stomach can exand from 50mls to what?
1-2 litres
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The stomach gastric glands (mucosa) contain what type of cells?
Parietal cells and chief cells
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What do parietal cells do?
They secrete hcl
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What do chief cells do?
They secrete pepsiongen.
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How much HCL can the stomach secrete each day?
2 litres
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If pepsinogen is an inactive zymogen, what is its active form?
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What is also secreted from the stomach?
Mucus and gastric lipase
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Parietal cells are an intrinsic factor required for absorption of what?
Vitamin B
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Wht coagulates milk?
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What is the mechanism of gastic acid secretion?
H+ ions, made from CO2 and water by carbonic anyhdrase, are actively transported into the lumen in exchange for K+ ions. Bicarbonate ions are exchanged for chloride ions which diffuse into lumen.
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What is the nett result of this?
The accumulaton of HCL in the lumen?
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How can you tell if something is a zymogen?
If it ends in "inogen"
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Why are zymogens a thing?
They a better in the inactive form so they only start digesting things when they're released into the lumen of the digestive tract.
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How is chymotrypsinogen activated?
The zymogen is cleaved between the 15 and 16th amino acids by trypsin. This forms 3 chains (ABC) which are linked by interchain disulphide bonds
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When is pepsinogen activated?
When it comes into contact with HCL in the stomach.
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Once activated, Pepsin can activate what?
More pepsinogen
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What does the pepsin then do?
It starts to degrade proteins into smaller polypeptides.
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How long is the small intentsine?
2.5-5 m long
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What are the names of the 3 sections of the small intestine?
Duodenum, jejenum and ileum
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What does the duodenum do?
It receives chyme from stomach, enzymes from pancreas and bile from liver and gall bladder.
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Which section if responsible for digestion?
The duodenum
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Which section is responsible for absorption?
All 3 sections - absorption of nutrients, water, vitamins and minerals.
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The crypts of Liberkuhn do what?
Secrete copious amounts of bicarbonate rich fluid.
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The epithelial wall of the mucosa are covered in what?
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Each cell has numerous...
Microvilli = brush border
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The villi have...
Capillaries and lymphatic vessels
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The total surface area available for absorption and digestion is
300m ^2
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The brush border has associated enzymes, which include...
Lactase, maltase, sucrase and nucleases, peptidases
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How long is the pancrease?
It is about 20cm long, weighs 100g
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What type of cells make digestive enzymes
Acinaar cells (exocrine cells) - they release digestive enzymes into duodenum via the secretory duct.
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In the pancreas, waht else is made?
Chymotrpypsin, trypsin, carboxylpeptidase, elastase, made as zymogens.
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What else is made?
Pancreastic amylase, lipase, proteases, DNAse, RNase
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What else do Acinar cells make?
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What do Islets of Langerhans (endocrine cells) make?
Hormones which are secreted into the blood.
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What do B cells make?
Insulin - stimulates glucose - glycogen
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What do A cells make?
Glucagon - stimulates glycogen - glucose
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What do d cells make ?
Somatostatin - regulates digestion, absorption and release of other hormonse
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What is type one diabetes?
It is early onset, insulin dependent - an autoimmune disease caused by loss of insulin secretion from the islets of Langerhans. Treated with insulin administration
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What is type two diabetes?
It is late on set diabetes, it is non insulin dependent - it is associated with obestity, sedentary lifestyle, and is due initially to loss of responsivness to insulin.
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How can type 2 diabetes be avoided?
Through diet and exercise, but may require insulin in advanced stages.
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What do both types of diabetes cause?
Evelation in blood glucose
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Monosaccarides and amino acids are transported into what...
Blood capillaries of villi, then to the liver via the hapatic portal vein.
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Fats are emulsidied into fat droplets by the action of ...
Bile salts, they are then susceptible to digestion by pancreatic lipase.
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Resulting fatty acids and monglycerides are converted into...
chylomicrons (small particles) which enter the lymphatic capillary system.
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How do monosaccharides, amino acids, electrolytes, water, absrobed from the intestine travel to the liver?
Via mesenteric veins and the hepatic portal vein. They can then enter the general cirulation via the hepatic vein
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What does the liver do?
It makes bile pigments (waste products of red blood cells) and bile salts
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Where are bile salts stored?
In the gall bladder
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What does the liver do?
It detoxifies absorbed materials and regulates blood composition, produces many proteins found in blood plasma, regulates blood glucose levels 9stored as glycogen), conversion of glucose to glycogen stimulated bt insulin - reverse of glucagon
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What type of structures are bile saltes?
They are amphipathic structures - so cholesterol derivatives
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Do bile salts digest fats?
No, they act as detergents to break them down into small droplets or micelles.
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What are the droplets then able to do?
They are then amenable to digestion by lipases
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Are bile salts destroyed after use?
No, they are recirculated
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How are chylomicrons formed?
Fatty acids and monoglycerides from fat digestion are absorbed and synthesised into trigylcerides, which are then packed into chylomicrons
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What happens to the chylomicrons after exocytosis?
They enter the lacteals and into the lymphatic ststem
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What is the colon?
It is the last metre of the GI tract
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What is the colon composed of?
Ascending, transverse, descending and sigmoid colons
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Is there digestion and absorption of nutrients in the colon?
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Which 3 segments absorb water and inorganic ions?
The first 3
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The sigmoid colon is the...
Strorage depot
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What happens to ***** matter?
It is ejected through rectum and anus
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What is the souce of main digestive enzymes?
Stomach enzmes (pepsin) are optimally active at very acidic pH, whereas those found in the small intestine are active at slightly alkaline pH.
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What is enterokinase?
It is a protease that converts trypsinogen into trypsin.
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What are the names of the phases responsible for regulation of gastric secretion?
Cephalic or Reflex phase (a few mins) and gastric phase (A few hours), Intestinal phase
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What is the cephalic or reflex phase?
The nervous system stimulates salivary and sastric secretions (olfactory receptors, taste buds -brain)(hypothalamus - vagus nerves) in response to aroma, taste, sight or thought of food.
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What is the Gastric phaes?
Involves acetylcholine, histamine and gastrin (polypeptide hormone made by stomach G cells) which together stimulate secretion of HCL and pepsinogen.
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What controls the gastric phase?
It is controlled by stomach distension and rising pH, as proteins in food ' mop up' H+ ions.
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What is the intestinal phase?
Release of chyme from stomach into duodenum briefly stimulates gastric activity via release of intestinal gastrin.
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What does continued release of chyme do?
It inhibits gastric activity due to secretion by duodenum of gastric inhibitory peptide (GIP), vasoactive intestinal peptide (VIP), cholecytostokinin (CCK), and secretin
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What are the major GI hormones?
Gastrin, Chyme, GIP, Secretin, CCK, VIP,
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Other cards in this set

Card 2


What is an autotroph?


Something that can subsit on inorganic nutrients alone (self sustaining) whereas heterotrophs require complex organic compounds in their diet.

Card 3


What do heterotrophs require?


Preview of the front of card 3

Card 4


What are the types of nutrient required?


Preview of the front of card 4

Card 5


Why do we need lipids?


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