6.1 Test Study Guide Flashcards
- Humans ingest food which provides energy and nutrients to carry out life processes.
a) Outline how starch in the diet is modified for absorption in humans. (3 marks)
Starch’s glycosidic bonds are broken down by the enzyme amylase which is secreted by salivary glands in the mouth. Stomach acids break down starch even further. In the Small intestine pancreatic amylase continues to break down starch into maltose and maltase breaks it down into glucose.
- b) Describe how the small intestine is adapted for efficient absorption of nutrients (5 marks)
The small intestine is a long tube where nutrients enter the bloodstream of lymph. Villi and Microvilli in the small intestine walls absorb molecules through a two-step process. First substances move into epithelial villi and then amino acids and sugars move into capillaries while certain fats enter lacteals. The process uses active transport done by mitochondria in the intestinal cells and is aided by channel protein. The villi in the small intestine enhance absorption by increasing surface are and the thinner walls speed up diffusion for quicker nutrient uptake.
- a) Humans rely on carbohydrates for much of their energy. Outline the process of digestion and absorption of starch in the human digestive system. (4 marks)
During digestion, salivary amylase in the mouth and pancreatic amylase in the small intestine break down starch into maltose and eventually glucose. Enzymes allow polymers to break down into monomers as starch breaks down into maltose and eventually glucose. In the small intestine villi allow for more absolution by increasing the surface area and aiding in the uptake of monosaccharides like glucose. Monosaccharides are absorbed into the blood stream through active transport or facilitated diffusion.
- Substances can move into and out of cells through the cell membrane.
a) Explain the adaptations of the small intestine to its function (7 marks)
The small intestine is where nutrients are absorbed into the bloodstream. It takes a very long time to maximize absorption in the small intestine because of the surface area increase by the villi which slows down the process because it takes time for all nutrients to pass through and be absorbed thoroughly. The small intestine is lined with smooth muscles that perform peristalsis. Circular muscles which incircle the intestine and constrict allowing for churning and moving and Logitudinal muscles which run parallel and propel digested food. The pancreas secretes enzymes into the lumen that break down starch, proteins and lipase while the Gall bladder stores bile and releases it into the small intestine in order to aid digestion. In the small intestine, the villi increase the surface area and each villi has microvilli which continue to increase the surface area allowing for more absorption. The villi absorb the end products of digestion including glucose, fatty acids, glycerol, and phosphates.
- Pastry cream or confectioners’ custard is made with a combination of milk (rich in casein and lactose), egg yolks, sugar, starch and a flavouring such as vanilla.
a) Describe the structure of starch. (5 marks)
Starch is a polysaccharide, a complex carbohydrate composed of long chains of glucose molecules linked together. Starch consists of amylose and amylopectin. Amylose consists of linear chains of glucose units connected by glycosidic bonds while Amylopectin consists of branched chains of glucose molecules linked by two types of glycosidic bonds. Branching gives starch its overall compact structure which makes it a storage form in plants.
- b) Explain how amino acids in casein could reach the liver, starting from the moment when the person takes a bite of pastry cream pie. (7 marks)
The digestive process begins in the mouth where mechanical/physical digestion begin to break down food. Next, it is mixed with saliva to form the bolus in the mouth and is moved through the esophagus through peristalsis. Pepsin proteins are then digested in the stomach, while in the small intestine, the pancreas secretes enzymes into lumen. These amino acids digest macromolecules into monomers and are absorbed by the villi on the walls of the small intestine. After being carried into the bloodstream in capillaries, they are carried through veins into the liver.
- Proteins are an important group of chemicals found in all living organisms.
a) Outline how proteins are digested and the products of protein digestion absorbed in humans.
Protein and digested by peptidase and protease at different stages of the digestive system/. In the stomach enzymes like pepsin, pepsinogen, and endopeptidase start breaking down proties, In the pancreas endopeptidase, trypsin, and peptidase continue breakdown. In the small intestine endoppeptidase continue to digest protein and polypeptides. Finally amino acids are absorbed into the bloodstream.
- a) 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 are proteins that catalyze a chemical reaction by offering an alternate pathway with a lower activation energy. The active sites on an enzyme are specific to certain substrates. Enzymes have the ability to break down macromolecules into smaller fragments and monomers, allowing these compounds to be readily absorbed. The pancreas secretes several enzymes, such as amylase and lipase, into the lumen of the small intestine. The small intestine has an alkaline pH which caters to certain enzymes, as enzymes require a specific pH to avoid denaturing. Amylase breaks down starch into sugar and disaccharides. Lipase can break down lipids and triglycerides into fatty acids and glycerol.
- Every cell is surrounded by a cell surface membrane which regulates the movement of materials into and out of the cell.
Describe the process involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine. (4 marks)
One process of absorption is simple diffusion where the nutrients, for example fatty acids, flow down the concentration gradient and freely cross the membrane. Another process of absorption is facilitated diffusion where nutrients like fructose and glucose flow down the concentration gradient with the aid of protein channels. Active transport is the movement of nutrients like mineral ions and amino acids against the concentration gradient which requires ATP. Endocytosis is when vesicles form around fluid containing nutrients, for example cholesterol, and draw the nutrients in.
