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Flashcards by ashiana121, updated more than 1 year ago
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Created by ashiana121
almost 9 years ago
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| Question | Answer |
| What are the seven main parts of the digestive system? (inc. 2 glands) | Oesophagus, stomach, small intestine, large intestine, rectum - glands: salivary glands, pancreas |
| Is the oesophagus adapted for digestion or for transport? | Transport |
| What is the role of the stomach? | To store and digest food |
| What does the inner layer of the stomach produce? | Enzymes |
| What other substance does the stomach produce? | Mucus |
| What do each of these substances do? | Enzymes - break down proteins Mucus - prevents the enzymes from breaking down the stomach |
| What are the inner walls of the small intestine folded into? | Villi |
| What does this give them? | A large surface area |
| How is the surface area of the small intestine further increased? | Microvilli on the surface of the villi |
| What does the large intestine absorb? | Water |
| What is the name of the process through which digested food is removed via the anus? | Egestation |
| Where are the salivary glands? | The mouth |
| Which enzyme is in the secretions of the salivary glands and what does it do? | Salivary amylase - hydrolyses starch into maltose |
| Where is the pancreas situated? | Below the stomach |
| The pancreas secretes pancreatic juice. What type of enzymes are in the pancreatic juice and what do they do? (3) | Proteases to digest proteins; lipases to digest lipids; amylase to digest starch |
| What are the two stages of digestion? | Chemical digestion and physical breakdown |
| Which two features physically break down food so that the surface area is increased? | The teeth, the muscles in the stomach |
| What is the definition of chemical digestion? | Breaking down large, insoluble molecules into smaller, soluble ones |
| What carries out chemical digestion? | Enzymes |
| All digestive enzymes function by _________ | Hydrolysis |
| Which are the three main types of digestive enzymes? | Carbohydrases, lipases and proteases |
| What do carbohydrases break down and into what? | Carbohydrates, ultimately into monosaccharides |
| What do lipases break down and into what? | Lipids into glycerol and fatty acids |
| What do proteases break down and into what? | Proteins, ultimately into amino acids |
| What is absorption? | Taking soluble molecules into the body |
| What is assimilation? | Incorporating the absorbed molecules of digestion into the body tissues |
| Carbohydrates are carbon molecules combined with what? | Water |
| What do carbon atoms readily make bonds with? | Other carbon atoms |
| What name is given to a single unit (that makes up a chain)? | Monomer |
| What name is given to many monomers joined together in a chain? | Polymers |
| What is the monomer unit of a carbohydrate? | A saccharide |
| What is a single monomer therefore called? | A monosaccharide |
| What name is given to a pair of monosaccharides? | Disaccharides |
| What name is given to large number of monosaccharides joined together? | Polysacchardides |
| What is the general formula for monosaccharides and what are two features of them? | (CH2O)n - sweet tasting and soluble |
| What is the name of the test used to test for reducing sugars? | Benedicts test |
| What is reduction? | A chemical reaction involving the gain of electrons |
| Therefore, what is a reducing sugar? | A sugar that can donate electrons (reduce) another chemical |
| What are the steps for the Benedicts test? | 1. Food sample dissolved in water 2. Equal volume of Benedicts reagent added 3. Heat mixture gently on a water bath for 5 minutes |
| If a reducing sugar is present in the sample, what is the result of the test? | An insoluble red/orange/brown precipitate (copper oxide) |
| What are the three disaccharides? | Maltose, sucrose and lactose |
| What two monosaccharides form maltose? | Glucose and glucose |
| What two monosaccharides form sucrose? | Glucose and fructose |
| What two monosaccharides form lactose? | Glucose and galactose |
| By what reaction do monosaccharides join together? | A condensation reaction |
| What does this involve? | The removal of a water molecule |
| What is the name given to the bond that is formed? | A glycosidic bond |
| By what process are disaccharides broken down into their constituent monosaccharides? | Hydrolysis |
| What does this involve? | The addition of water |
| Give an example of a disaccharide that is a reducing sugar | Maltose |
| Other disaccharides, such as sucrose, are non-reducing sugars. From the results of a Benedicts test, how do we know this? | The colour of the sample and the Benedicts reagent do not change colour when heated |
| What is the first part of the test that can be done to test for non-reducing sugars? (after the initial Bdicts test in which the solution remained blue) | Add another 2cm3 of the sample to 2cm3 of dilute HCl - heat in water bath for 5 mins |
| What does the HCl do? | Hydrolyses any disaccharide present into their constituent monosaccharides |
| What substance is then added to the solution to neutralise the HCl? | Sodium hydrogen carbonate (NaHCO3) |
| Why is this necessary? | Benedict's reagent doesn't work in acidic conditions |
| What can we use to check that the solution is alkaline? | pH paper (universal indicator paper) |
| What is added to this solution and how long is it heated in a water bath for? | Benedict's reagent - heated for 5 mins |
| If a non-reducing sugar was present in the original sample, what colour will the solution now go? | Orange-brown |
| Why is this? | Due to the reducing sugars that were produced from the hydrolysis of the non-reducing sugar |
| Many monosaccharides join to form polysacchairdes under what reaction? | Condensation reaction |
| Being very large, polysaccharides are ___________ | Insoluble |
| What does this feature make them suitable for? | Storage |
| When hydrolysed, what do polysaccharides break down into? | Monosaccharides and disaccharides |
| Give an example of a polysaccharide that is not used for storage but for structural support (and in what) | Cellulose - structural support in cell walls |
| Starch is also a polysaccharide. What monosaccharides link together to form starch? | Alpha glucose |
| What substance do we use to test for starch? | Iodine solution |
| When iodine solution is dropped on to/in to the sample being tested for starch content, what colour will it go? | Blue-black |
| Why does it often take more than one enzyme to completely break down a large molecule? | Enzymes are specific; one enzyme breaks down a molecule into smaller sections and other enzymes break down these smaller sections |
| What is the name given to the individual units that the enzymes are broken down into? | Monomers |
| In starch digestion, what is the first enzyme called and where it is produced? | Amylase - by the salivary glands and by the pancrease |
| What does amylase hydrolyse? | The alternate glycosidic bonds of the starch molecules |
| What does this produce? | The disaccharide maltose |
| Which enzyme hydrolysed maltose into alpha glucose? | Maltase |
| Where is maltase produced? | The lining of the intestine |
| Food is taken into the mouth and chewed by the teeth. This breaks the food into small pieces, giving it a what? | Large surface area |
| Where is saliva secreted from? | The salivary glands |
| Which of the enzymes is in saliva? | Salivary amylase |
| What else is in saliva that helps amylase to work? | Mineral salts to maintain pH at around neutral - optimum for amylase for work |
| What does the HCl in the stomach do? | Denatures salivary amylase and so prevents further hydrolysis of starch |
| What secretion is the food mixed with as it passes from the stomach to the small intestine? | Pancreatic juices |
| What enzyme is in the pancreatic juice? | Pancreatic amylase |
| What does pancreatic amylase do? | Hydrolyses the remaining starch into maltose |
| What else is in pancreatic juice? | Mineral salts - again to maintain pH at neutral so amylase can function |
| What do muscles in the intestine wall do? | Move food along down the small intestine |
| Which enzyme does the epithelial lining of the small intestine produce? | Maltase |
| Maltase hydrolyses maltose into _______ | Alpha glucose |
| Where is the enzyme that breaks down sucrose secreted? | The small intestine epithelial lining |
| What is this enzyme called? | Sucrase |
| Why is it essential for foods containing sucrose to be broken down by the teeth? | Because sucrose is usually contained within the cells |
| What does sucrase hydrolyse? | The single glycosidic bond between glucose and fructose |
| In what products is lactose found? | Dairy |
| Where is lactose digested and by what enzyme? | Small intestine - lactase |
| What two monomers are joined by a single gylcosidic bond that make up lactose? | Glucose and galactose |
| Why do babies have large amounts of the lactase enzyme? | Milk is the only food they eat |
| As milk becomes a smaller part of our diet in adults, what happens to the production of lactase during childhood? | It naturally diminishes |
| However what can happen? | The reduction is so great some people produce little or no lactase at all |
| Because there is no lactase to break down the lactose when it reaches the small intestine, what breaks it down instead? | Microorganisms |
| What do the microorganisms release in large volumes? | Gas |
| What does this result in? | Bloating, nausea, diarrhoea and cramps |
| How can this be avoided? | By avoiding products containing lactose |
| What is the main problem this causes? | Calcium deficiency |
| How can this be solved? | Eating calcium rich foods or adding lactase to products containing lactose before eating it |
| What are enzymes made from? | Proteins |
| What are the monomer units that make up polypeptides? | Amino acids |
| What can polypeptides be combined to form? | Proteins |
| How many amino acids naturally occur in proteins? | 20 |
| Name the parts of an amino acid | Amino group, carboxyl group, hydrogen atom, R group, central carbon atom |
| What is the formula of the carboxyl and amino groups? | Carboxyl -COOH Amino -NH2 |
| Two amino acids joined together is known as a __________ | Dipeptide |
| What reaction occurs when two amino acids join together? | Condensation reaction |
| This involves the removal of a water molecule. Where does this water molecule come from? | An -OH from the carboxyl group of one amino acid and a -H from the amino group of another amino acids |
| A proteins shape is ______ to its function | Specific |
| In the secondary structure of proteins, the polypeptides can be twisted into a 3D shape. What is a name given to this 3D shape, and what bonds make the long polypeptide chain twist? | Alpha helix - hydrogen bonds |
| What happens to the alpha helices of the secondary structure for it to form the tertiary structure of a protein? | Twisted and folded more |
| A number of different bonds hold together this tertiary structure. What are the names of these bonds? (3) | Ionic bonds, hydrogen bonds and disulphide bonds |
| Which are the strongest bonds and which are the weakest? | Strongest - disulphide Medium - ionic Weakest - hydrogen |
| What is the quaternary structure of a protein? | Numerous polypeptide chains combined. May be prosthetic groups associated e.g haemoglobin |
| What test do we use to test for proteins? | Biuret test |
| What does Biurets reagents detect? | Peptide bonds |
| What colour will the solution go if peptide bonds (therefore a protein) are present? | Purple |
| What happens if there is no peptide bonds, and therefore no protein? | The solution remains blue |
| Which part of an enzyme does the reaction take place in? | The active site |
| What is the molecule called that binds to the active site? | The substrate |
| What does the 'lock and key' model state? | The active site of an enzyme is complementary to the substrate - they fit exactly like a lock and key |
| What does the 'induced fit' model state? | The active site is flexible and can change shape - substrate and active site are not completely complementary - the active site changes shape when the substrate binds to fit it in |
| Enzymes are biological catalysts that lower the what? | Activation energy of a reaction |
| What 5 factors can affect enzyme action? | Temperature - pH - substrate concentration - enzyme concentration - inhibitors |
| What is the approx. optimum temperature for human enzymes? | 40 degrees celcius |
| What happens if the temperature is increased beyond this? | Shape of active site changes (heat breaks h-bonds) and enzyme does not function/becomes denatured |
| What does a change in pH change about the enzyme? | The shape of the active site |
| What does this mean? | The substrate can no longer fit & reaction can no longer be catalysed |
| What happens to the rate of reaction as the enzyme concentration increases? | It increases |
| What happens to the rate of reaction when the concentration of the substrate is increased and why? | It increases - more substrate molecules can collide with enzymes |
| However what happens at higher substrate concentrations? | The enzyme active sites become saturated with substrate so there are few enzymes - the rate levels off |
| What are the two types of inhibitor? | Competitive and non-competitive |
| Which inhibitor molecules have a shape similar to that of the substrate molecules? | Competitive |
| What do competitive inhibitors compete with and what for? | Compete with substrate molecules for the active site |
| Why don't non-competitive inhibitors bind to the active site of an enzyme? | The shape of non-competitive inhibitors is not similar to that of the substrate |
| Where do non-competitive inhibitors bind to? | A site that is NOT the active site |
| What does this do? | Changes the shape of the active site - so that the substrate no longer fits |
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