Enzymes and digestion Flashcards
(54 cards)
1
Q
What is the test for starch?
A
Iodine solution
2
Q
What is a positive result for the starch test?
A
Colour change from BROWN TO BLUE/BLACK
3
Q
What is the test for simple sugars?
A
Benedict’s solution + heat
4
Q
What is a positive result for the test for simple sugars?
A
Colour change from BLUE TO GREEN/YELLOW/ORANGE/BRICK RED depending on how much is present
5
Q
What is the test for protein?
A
Biuret solution
6
Q
What is a positive results for the test for protein?
A
Colour change from BLUE TO PURPLE
7
Q
What is the test for lipids?
A
Ethanol
8
Q
What is the positive result for the test for lipids?
A
Colour change from CLEAR TO CLOUDY WHITE EMULSION
9
Q
What is the alternative test for lipids?
A
Sudan III stain
10
Q
What is the positive result of the Sudan III stain test?
A
Red oily layer will form on the top of the liquid, as the powder has dissolved into the lipid
11
Q
Define enzyme
A
A protein that works as a biological catalyst in metabolic reactions
12
Q
Why are enzymes important?
A
Without enzymes, metabolic reactions would occur too slowly for us to live
13
Q
How do enzymes work?
A
- substrate will bind to enzyme’s active site to form the enzyme-substrate complex
- the reaction occurs and the enzyme breaks down the substrate into its products
- as its a catalyst, the enzyme’s active site remains unchanged at the end of the reaction
14
Q
Define active site
A
The space on the enzyme where the substrate binds to
15
Q
Define substrate
A
A molecule that an enzyme acts on
16
Q
Define enzyme-substrate complex
A
The enzyme and substrate bound together
17
Q
What is the effect of temperature on enzyme function
A
- as temperature increases, so does the kinetic energy of the substrate
- this means that more frequent collisions occur between the active site and substrate, increasing RoR
- after a while, the temperature reaches OPTIMUM TEMPERATURE, where rate of reaction will be the highest
- above optimum, the shape of the enzyme’s active site changes, until the substrate will no longer fit in it, becoming denatured
- this causes RoR to decrease to 0
18
Q
What is the effect of pH on enzyme function?
A
- different enzymes have different optimum pH, and are often found in areas of the body which have a similar/same pH to this
- pH’s more acidic or alkaline than the optimum cause the shape of the active site to change slightly so the substrate can’t fit into it as effectively, so ROR decreases
- at optimum pH, the enzyme’s active site fits onto the substrate best as possible so RoR is at highest and fastest
- if pH is too different to optimum, then the active site will change so much that the substrate no longer fits into it, and becomes denatured. Here ROR becomes 0
19
Q
Describe how to set up and do the enzyme and pH experiment
A
- add: 5cm3 hydrogen peroxide, 10cm3 pH buffer, 5 drops of universal indicator + 2 drops fairy liquid to a measuring cylinder and swirl it gently to combine
- add 2 pipettes of mashed potato suspension to start the reaction
- place test tube in water bath of optimum temperature (e.g 30°C) to maintain a constant controlled temperature
- record height/volume of foam in 120s
- repeat for pH 4, 7, 10
20
Q
What is the function of pH buffer?
A
pH buffers are solutions of salts that resist changes in pH. Different pH buffers can be used to maintain different pH
21
Q
What was the colour of the indicator at pH four?
A
Yellow
22
Q
What was the colour of the indicator at pH 7?
A
Light green
23
Q
What is the colour of the indicator at pH 10?
A
Blue/navy blue
24
Q
What were the variables in the pH experiment?
A
- Control = temperature, type/age of potato, type of enzyme
- independent = pH
- dependent = rate of reaction by measuring volume of oxygen produced in 30s/1 min
25
describe and setup the experiment that observes the effect of temperature on enzyme activity
- add 5cm3 of starch solution to a test tube and heat to a set temperature with a water bath
- add a drop of iodine to each of the wells in the spotting tile
- use a pipette to add 2cm3 amylase to the starch solution and mix well
- every minute transfer a droplet of solution to a new well of iodine solution (which should turn blue-black)
- repeat this transfer process until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
- record the time taken for the reaction to be completed
- repeat the investigation for a range of temperatures (from 20°C to 60°C)
26
Explain each part of CORMMSS
C = Change - what values will u change and how u will change them
O = organism - give details on how organisms will be standardised (e.g same mass)
R = repeats - repeat whole experiment 3 times
M = measure 1
M =measure 2
S = same 1
S = same 2
27
what is digestion? where does it occur?
- the physical and chemical breakdown of food so that large, insoluble molecules convert into smaller soluble ones for absorption into the blood
- the digestive system = an organ system that manages digestion
28
what is the name of the path that food travels through during digestion?
alimentary canal
29
what is the name of the type of organs that are near the alimentary canal and are used in digestion but don't actually have food pass through them?
accessory organs - they produce substances needed for digestion to occur (e.g the liver and pancreas)
30
describe the structure and function of the mouth for digestion
- teeth chew food to physically break it into smaller pieces (increasing its SA:V) = mechanical digestion
- salivary glands produce the carbohydrase enzyme amylase and the complex carbohydrate starch is digested into the simple sugar maltose = chemical digestion
- food is lubricated into a bolus by saliva so that it can easily swallowed
31
describe the structure and function of the oesophagus for digestion
- muscular tube that connects the mouth to the stomach
- neither chemical or physical digestion occur here
- wave like contractions push the bolus down without gravity
32
describe the structure and function of the stomach for digestion
- contracts its muscular walls to mix the food and push it onto the small intestine
- produces the protease enzyme pepsin to break down proteins into peptides
- produces HCl to maintain the optimum pH of pepsin (2) so it can work most efficiently
- HCl also kills any bacteria that we may have ingested in our food
33
what is the name for partly digested food with gastric juices in it?
chyme
34
when does chyme leave the stomach?
- chewed food leaves the stomach as chyme to go to the small intestine after a few hours of entering it
- the sphincter muscle at the bottom of the stomach relaxes, allowing the chyme to leave the stomach to enter the duodenum
35
what happens to chyme when it enters the duodenum?
- pancreatic juices enters duodenum from pancreas
- gall bladder releases bile into duodenum
36
how does bile enter the duodenum? how do pancreatic juices enter the duodenum?
- bile = produced by liver, stored in gall bladder and enters duodenum by bile duct
- pancreatic juices = produced and stored in the pancreas, enters duodenum by pancreas duct
37
what is the function of the pancreatic juices?
- several enzymes produced by the pancreas are released e.g:
- protease trypsin = breaks down proteins into peptides
- lipases = break down lipids into fatty acids and glycerol to be absorbed into the bloodstream at the ileum
- amylase = breaks down starch into maltose
- maltase = breaks maltose down into glucose to be absorbed into the bloodstream at the ileum
38
what is the function of bile and how does it aid digestion?
- produced by the liver + stored in the gall bladder
- enters the duodenum by the bile duct
- emulsifies large fat globules into smaller fat droplets to increase SA for lipases to work on = speeds up rate of digestion
39
why are both bile and pancreatic juices alkaline?
- neutralises the acidic chyme
- makes chyme neutral - slightly alkaline to create optimum pH for enzymes in small intestine to work in
- prevents the acidic chyme from damaging the lining of the small intestine
40
what enzymes does the pancreas produce?
- proteases = trypsin (found in small intestine and produced in the pancreas)
- lipases
- carbohydrases = amylase (found in mouth and small intestine and produced by salivary glands and pancreas)
41
where are nutrients absorbed into the bloodstream from in the alimentary canal?
walls of the small intestine - specifically the ileum
42
describe the structure and function of the duodenum for digestion
- the first part of the small intestine that receives acidic chyme from the stomach
- c-shaped section after the sphincter of the stomach
- where pancreatic juices and bile are secreted to neutralise chyme + provide optimum pH for enzymes in small intestine + prevent damage of alimentary canal from acidic chyme + emulsify large fat globules for easier digestion in the ileum
43
describe the structure and function of the ileum for digestion
- trypsin, peptidase, amylase, maltase and lipases are secreted into the small intestine and break down nutrients for absorption into the bloodstream
- small intestine has many folds that increase its surface area so that more nutrients can be absorbed into the bloodstream at any one time
- lined with finger-like projections called villi (increasing SA) which have walls of only one cell thick = short diffusion distance for nutrients into blood
- villi also have a good blood supply that maintains high concentration for diffusion of substances into the blood
- each villus is lined with hundreds of microvilli (increasing SA for diffusion + absorption)
- each villus also contains a lacteal which absorbs fat into the lymphatic system
44
what enzymes are present in the ileum? what do they break down?
- trypsin, peptidase, amylase, maltase and lipases
- trypsin breaks down proteins into peptides and peptidases break down peptides into amino acids - amino acids can now be absorbed into the bloodstream by the lining of the small intestine
- amylase breaks down starch into maltose and maltase breaks down maltose into glucose - glucose can now be absorbed into the bloodstream by the lining of the small intestine
- lipases break down lipids into fatty acids and glycerol- fatty acids and glycerol can now be absorbed into the bloodstream by the lining of the small intestine
45
describe the structure and function of the large intestine for digestion
- made out of the colon and the rectum
- colon absorbs excess water and electrolytes from the remaining food to make faeces
- faeces are stored in the rectum and exit the alimentary canal by the anus
46
describe the structure and function of the pancreas for digestion
- produces all three types of digestive enzymes: amylase, trypsin and lipase
- secretes enzymes in an alkaline fluid into the duodenum for digestion - this raises the pH of fluid coming out of the stomach to provide optimum pH for enzymes in small intestine and prevent damage of the alimentary canal by the acidity of the chyme
47
what two types of muscle are the walls of the alimentary canal made out of?
- all of the alimentary canal is made out of smooth muscle
- smooth muscle consists of two muscle types - circular and longitudinal muscle
- circular muscle has fibres arranged in rings around the gut
- longitudinal muscle has fibres arranged along the length of the gut
48
what does circular and longitudinal muscle do when they each contract?
- when circular muscle contracts, it reduces the diameter of that section of the alimentary canal
- when longitudinal muscle contracts, it reduces the length of that section of the alimentary canal
49
what is peristalsis?
waves of muscular contraction that push food along the alimentary canal
50
what aids peristalsis?
- mucus is produced to continually lubricate the food mass and reduce friction
- dietary fibre provides the roughage required for the muscles to push against during peristalsis
51
how does peristalsis work?
- when the circular muscle contracts, the longitudinal muscle relaxes = makes the gut narrower in diameter in that section
- when the longitudinal muscle contracts, the circular muscle relaxes = shortens the length of the gut
- this combined action of the antagonistic muscle pair propels the food forward through the alimentary canal
52
how is starch broken down into glucose?
- starch is broken down by amylase into maltose
- maltose is broken down by maltase into glucose
- glucose is absorbed into the bloodstream from the small intestine to where it is transported to respiring cells
53
how are proteins broken down into amino acids?
- proteases such as pepsin, trypsin and peptidases break down proteins into amino acids
- pepsin and trypsin break down proteins into peptides
- peptidase breaks down peptides into amino acids
- amino acids are absorbed into the bloodstream from the small intestine to where it is required in the body
54
how are lipids broken down into the three fatty acids and glycerol?
lipases break down lipids into fatty acids and glycerol
