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IB Biology Unit 6.1: Digestion + Old Questions
Terms in this set (21)
What is the structure of the digestive system? Draw and label a diagram of the human digestive system
Ensure that there is t-junction connection with the pancreatic duct and common bile duct joining the duodenum;
You must be able to trace a continuous path all the way through from the mouth to the anus
What is the structure of the wall of the small intestine like? What tissues is it composed of?
Made up of serosa - an outer coat;
muscle layers - longitudinal muscle and inside it circular muscle;
sub-mucosa - a tissue layer containing blood
and lymph vessels;
mucosa - the lining of the small intestine,
with the epithelium that absorbs nutrients on
its inner surface; (has villi on its surface)
What is peristalsis (in digestion) and how does it occur? What is it controlled by?
-the contraction of circular and longitudinal muscle layers of the small intestine mixes the semi-digested food with enzymes; and moves it along the gut (speeds up digestive process)
-controlled by the enteric nervous system
What is the function of the pancreas in digestion?
-The pancreas secretes two types of things.
1) The hormones insulin and glucagon to regulate blood sugar
2) Digestive enzymes which are released into the small intestine (pancreatic juice)
What does pancreatic juice contain and for what?
- enzyme amylase to digest starch (product: maltose)
-lipases to digest triglycerides and phospholipids (product: fatty acids and glycerol)
-proteases to digest proteins and peptides (product: polypeptides)
Why is digestion of large food molecules necessary?
Most food molecules are large polymers and insoluble;
e.g. carb, proteins, fats, nucleic acids, proteins;
They must first be digested to smaller soluble molecules before they can be absorbed into the blood (monomers);
in the small intestine
What are the monomers (nutrients) that can be absorbed by the small intestine ?
-monosaccharides (eg glucose and fructose)
-fatty acids & glycerol
what are the "digestive products" that can be absorbed by villi?
-monomers (-monosaccharides eg glucose and fructose
-fatty acids & glycerol
Why are enzymes needed in digestion?
Enzymes are biological catalysts that increase the rate of reaction;
Digestive enzymes are secreted into the lumen of the gut;
Digestive enzyme increase the rate of reaction of the hydrolysis of insoluble food molecules to soluble end products;
Digestive enzymes increase the rate of reaction at body temperature;
which would otherwise be too slow for effective digestion;
Digestive enzymes digest most macromolecules in food into monomers in small intestine
What are the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase?
What is the function of the stomach? small intestine and large intestine
Stomach: digests proteins, and mixes food by churning
Small intestine: absorbs nutrients (-fatty acids & glycerol
Large intestine: water and dissolved minerals (i.e. ions) are absorbed
What is the function of the small intestine? What aids this?
it is where usable food substances (e.g. nutrients--monosaccharides, amino acids, fatty acids, vitamins) are absorbed into the bloodstream by diffusion, active transport and facilitated diffusion;
the small intestine is lined with villi, to increase surface area and optimise the rate of absorption;
Microvilli on villi to further increase SA:Vol.
How is the structure of the villus is related to its role in absorption and transport of products of digestion?
Learn the mnemonic - MRSLIM for villus features and functions:
Microvilli: Ruffling of epithelial membrane ,greatly increase the surface area of the villus, allowing for a greater rate of absorption;
Rich capillary networks: Help to maintain a concentration gradient for faster absorption by rapidly transporting absorbed products away in the blood;
Single epithelial layer: Ensures minimal diffusion distance between the intestinal lumen and capillary network for faster absorption;
Lacteals: Absorb lipids from the intestine into the lymphatic system (which are later reabsorbed back into normal circulation)
Intestinal crypts: Located between villi and release juices that act as a carrier fluid for nutrients;
Membrane proteins and mitochondria: High amounts to enable active transport into cells (contents then passively diffuse into bloodstream) for molecules like glucose;
What is the function of the large intestine?
absorbs water and dissolved minerals;
Distinguish between absorption and assimilation
Absorption: The movement of a fluid or dissolved substances across a membrane
Assimilation: The conversion of nutrients into fluid or solid parts of an organism in cells (when tissues take them up and use them)
Hint: Absorption is taking it into something, assimilation is making it a part of something
How is starch digested? Where are products transported to after absorption?
Starch is made up of amylose;
which is unbranched and linked by 1-4 bonds;
amylase breaks down amylose;
maltose is broken down by maltase;
which is in the membranes of villi;
absorbed via co-transport into blood;
transported to the liver;
what structure of the small intestine transports most fats
where in the digestive system is the most water absorbed from?
What processes occur during assimilation and absorption of lipids?
-assimilation: lipids are incorporated into new membranes
absorption: lipids pass into the lacteal
What are the different methods of absorption in the small intestine? what does each method absorb? where do they all go?
-each method of absorption in the small intestine absorbs different nutrients
Active transport: glucose &amino acids
Facilitated Diffusion: glucose&fructose
Simple diffusion: glycerol/lipids/triglycerides
-they are all transported to capillaries
what is the digestion of starch initiated and continues by? (enzyme-wise)
The digestion of starch is initiated by salivary amylase in the mouth and continued by pancreatic amylase in the intestines
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