A.S Biology Unit 1.2 Summary Questions

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Question Answer
State one way in which the stomach is adapted to a.churn food and prevent the enzymes it produces from digesting the surface of the stomach.a.By having a muscular wall secreting mucus
What is hydrolysis?The breakdown of molecules by the addition of water to the bonds that hold these molecules together
Which two structures produce amylase?Salivary glands, pancreas
Suggest a reason why the stomach does not have villi or microvilli.Villi and microvilli increase surface area to speed up the absorption of soluble molecules. As the food in the stomach has not yet been broken down into soluble molecules they cannot be absorbed and so villi and microvilli are unnecessary.
Large molecules often contain carbon. Why is this?Carbon atoms readily link to one another to form a chain
What is the general name for a molecule that is made up of many similar repeating units?polymer
Why does Benedict's reagent turn red when heated with a reducing sugar?Sugar donates electrons that reduce blue copper (II) sulphate to orange copper (I) oxide
Which one, or more, monomer units make up starch?glucose
To hydrolyse a disaccharide it can be boiled with hydrochloric acid but if hydrolysis is carried out by an enzyme a much lower temperature (40degrees) is used. Why is this?Enzymes are denatured at higher temperatures and this prevents them functioning/ enzymes lower the activation energy required
What is the final product of starch digestion in the gut?alpha glucose
Name 3 enzymes produced by the epithelium of the small intestinemaltase, sucrase, lactase
In lactose intolerant people, microorganisms in the large intestine convert the undigested lactose into gas. By which process do microorganisms probably produce this gas? Suggest a reason why the gas is unlikely to be carbon dioxide.Respiration. Carbon dioxide forms as a result of aerobic respiration. Conditions in the large intestine are anaerobic.
What type of bond links amino acids together? Peptide bond
What type of reaction is involved in linking amino acids together?Condensation reaction
What four different components make up an amino acid?Amino group, carboxyl group, hydrogen atom, r group
What is a catalyst?A substance that alters the rate of a chemical reaction without undergoing permanent change
Why are enzymes effective in tiny quantities?They are not used up in the reaction so can be used repeatedly
Explain why changing one of the amino acids that makes up the active site could prevent the enzyme from functioning.The changed amino acid may no longer bind to the substrate, which will then not be positioned correctly, if at all, in the active site
Why might changing certain amino acids that are not part of the active site also prevent the enzyme from functioning?The changed amino acid may be one that forms hydrogen bonds with other amino acids. If the new amino acid does not form hydrogen bonds the tertiary structure of the enzyme will change, including the active site, so that the substrate may no longer fit.
Explain why enzymes function less well at lower temperatures.To function enzymes must physically collide with their substrate. Lower temperatures decrease the kinetic energy of both enzyme and substrate molecules, which then move around less quickly. They hence collide less often and therefore react less frequently.
Explain how high temperatures may completely prevent enzymes from functioningThe heat causes hydrogen and other bonds in the enzyme molecule to break. The tertiary structure of the enzyme molecule changes, as does the active site.
Enzymes produced by micro organisms are responsible for spoiling food. Using this fact and your knowledge of enzymes, can you suggest a reason why a.Food is heated to a high temperature before being canned. b.Some foods, such as onions, are preserved in vinegar.a. High temperatures denature the enzymes and so they cannot spoil the food. b.Vinegar is very acidic and the low pH will denature the enzymes and so preserve the food
An enzyme controlled reaction is inhibited by substance X. Suggest a simple way in which you could tell whether substance X is acting as a competitive or a non-competitive inhibitorIncrease the substrate concentration. If the degree of inhibition is reduced it is a competitive inhibitor, if it stays the same, it is a non competitive inhibitor.