1
Q
What are the 3 major nutrients that we need in large quantities?
A
-carbohydrates
-proteins
-lipids
2
Q
What happens when we eat carbohydrates, proteins and lipids?
A
-they are first broken down
-and then reassembled into our own carbohydrates, proteins and lipids
3
Q
Why are carbohydrates, proteins and lipids broken down after being eaten before then being reassembled?
A
-most of the molecules in food are too large to pass through the absorbing surface of the gut wall
-the carbohydrates, proteins and lipids are reassembled in the form required, rather than other animal or plant versions
4
Q
What is the major function of carbohydrates?
A
-source of energy
> glucose is the main respiratory substrate
5
Q
What is the major function of proteins?
A
-growth and repair
6
Q
What is the major function of lipids?
A
-energy
-make up part of cell membranes so essentials for normal growth
7
Q
What are the major sources of carbohydrates?
A
-starch: potatoes, rice and wheat products, bread, cereals and pasta
-sugars: fruit, smoothies, fizzy drinks, chocolate and sweets
8
Q
What are the major sources of proteins?
A
-meat
-eggs
-cheese
-beans
-nuts
-seeds
9
Q
What are the major sources of lipids?
A
-butter and margarine
-meat
-plant oils
-oily fish,
-nuts
-seeds
10
Q
Why can we absorb the glucose molecule directly through the walls of the digestive system?
A
-it is small enough
11
Q
Why can we not absorb starch directly through the walls of the digestive system but we can with the glucose molecule?
A
-glucose molecule is much smaller (small enough to be absorbed)
-starch is a polymer of glucose and large to pass through the gut
> must be broken down into glucose molecules
12
Q
What is cellulose made up of?
A
-glucose molecules
13
Q
Why is cellulose an important part of our diet?
A
-it is made up of glucose molecules which we need for energy
14
Q
How does our digestive system handle cellulose?
A
-it cannot be broken down by the digestive system
> egested from the gut
15
Q
What do glucose molecules do once absorbed by the body?
A
-they are transported to cells and are:
> used for respiration
> reassembled into the storage form of carbohydrates in animals - glycogen
16
Q
What is the glucose produced by photosynthesis in a plant metabolism converted into?
A
-starch for storage
-cellulose for cell wall synthesis
-energy through respiration
17
Q
Is glycogen converted into starch in animals?
A
no
18
Q
Where is glucose stored in animals?
A
glycogen
19
Q
What are proteins made up of?
A
amino acids
20
Q
Why are proteins broken down and what are they broken down into?
A
-the molecules are too large to pass through the gut wall
-must be first broken down into amino acids
21
Q
What happens once the amino acids are inside the body?
A
-they are reassembled into the proteins the individual requires
22
Q
Where are excess amino acids broken down?
A
-in the liver
23
Q
Lipids are esters of…
A
…fatty acids and glycerol.
24
Q
Why must lipid molecules be digested before passing through the gut wall?
A
-they are too large to pass through the gut wall
25
What is an example of one of the lipids the body's cells needs?
-lipids for the cell membrane
26
What does qualitative mean?
-describes results that are not expressed as numbers or numerical data
27
What is the test for reducing sugars (e.g. glucose) ?
-add Benedict's solution to food
-heat in a water bath
-if reducing sugars are present, they will give a red-brown precipitate with Benedict's solution
28
What are reducing sugars?
-sugars that act as reducing agents, e.g. glucose, fructose, lactose, maltose
-sucrose is non-reducing
29
Why might Benedict's solution be green or yellow?
-if there's not much glucose present
-orange if there's a little more
30
What are the precautions of the Benedict's solution test?
-wear safety goggles
-avoid contact with eyes
> as Benedict's solution is an irritant
31
What is the test for starch?
-add iodine solution to the food being tested
-if starch is present, food will turn blue-black colour
32
How can the iodine test also be used with a microscope?
-in order to stain starch grains in plant cells
33
What is the test for proteins?
-add 1 cm3 of biuret solution A to the food solution
-mix the liquids
-add 1 cm3 of biuret solution B and shake
-if protein is present it will turn purple/ there will be a purple ring between the layers
34
What are the hazards of the test for proteins?
-biuret solution A is corrosive
-biuret solution B is an irritant
35
What are the safety precautions of the test for proteins?
-wear safety goggles
-avoid contact with skin and eyes
36
What is the Sudan III lipids test?
-add equal amounts of water and food to a test tube
-add drops of Sudan III and shake the test tube
-a red-stained layer forms on the surface of the water
37
What are the hazards of Sudan III solution?
-it is flammable as it is dissolved in alcohol
38
What are the precautions of the emulsion test?
-wear safety goggles
-avoid contact with skin and eyes
39
What are the precautions of the Sudan III test?
-wear safety goggles
-avoid contact with skin and eyes
40
Why is ethanol a hazard in the emulsion test?
-it is flammable
41
What is the emulsions test?
-add ethanol to a test tube of crushed food
-pour the liquid into a second test tube of water, leaving any residue behind
-a cloudy liquid (or emulsion) indicates the presence of lipid in the food
42
What are the two functions of the human digestive system?
-breaks down complex food substances into smaller molecules
-provides the very large surface area for maximum absorption of food
43
What is the function of the mouth?
-begins the digestion of carbohydrates
44
What is the function of the stomach?
-begins the digestion of protein; small molecules such as alcohol absorbed
45
What is the function of the
small intestine (duodenum)?
-continues the digestion of carbohydrate and protein; begins the digestion of lipids
46
What is the function of the small intestine (ileum) ?
-completes the digestion of carbohydrates and proteins into simple sugars and amino acids; absorption of simple sugars, amino acids and fatty acids and glycerol
47
What is the function of the large intestine?
-absorption of water; egestion of undigested food
48
How is the small intestine adapted to maximise absorption?
-surface of the small intestine wall is folded, and has projections called
villi, increasing the surface area
49
What is the function of digestive enzymes?
-catalyse the breakdown of food molecules in order for them to br broken down and easily absorbed in the gut
50
How do the epithelial cells that cover each villus in the small intestine increase surface area?
-they each have projections called microvilli
51
The epithelial cells that cover each villus themselves have projections called...
...microvilli.
52
Where does most of our digested food pass through?
Where do lipids pass through?
-passes through the epithelial cells of the gut wall and is carried by blood to the liter
-digested lipids pass through the gut wall and enter the lacteals
53
What is the active site of an enzyme?
-part of the enzyme to which a specific substrate can attach or fit on to
54
Are enzymes 2D?
-no they have a complex 3D shape
55
Why do we need enzymes in our body?
-chemical reactions required to break food down would be too slow
-and so we need enzymes to catalyse these reactions to speed them up
56
What is an enzyme?
-biological catalyst
-protein which catalyses chemical reactions in living things
57
Where do the chemical reactions ,that enzymes are required for, occur?
-in the breakdown of chemical molecules, which we see in the digestive system
58
What is the substrate?
-a substance on which enzymes act and is complementary to the active site of an enzyme
59
Describe what happens when the substrate collides with an active site of an enzyme
-substrate collides with active site of enzyme and becomes attached
-enzyme catalyses breakdown of substrate
-broken-down products are released from the active site
60
Why is the enzyme and substrate referred to as the 'lock in key'?
-active site has a complementary shape exclusively to the substrate, just like the lock in key
61
What is the fit between the enzyme and substrate called?
-lock and key
62
How is the active site of an enzyme adapted to its function?
-it has a complementary shape to the substrate molecule
63
What are the factors affecting enzyme action?
-temperature
-pH
64
Why is enzyme activity lower at low temperatures?
-they have less kinetic energy, so molecular movement decreases
-number of successful collisions between enzyme and substrate is reduced
-rate of reaction is slow
65
What is the optimum temperature for enzymes in the human body?
37 degrees celsius
66
Why is enzyme activity reduced at temperatures higher than 37 degrees?
-temperatures higher than the optimum temperature (37 degrees) disrupt the active site's shape
-substrate can no longer fit in it which will reduce its activity or prevent it from working
> will become denatured
67
What does it mean when an enzyme is denatured?
-when the shape of its active site changed, e.g. due to high temperatures/extremes of pH
-and the substrate can no longer bind properly to it
-and so the enzyme becomes ineffective/completely inactive (denatured)
68
What are proteins chains of?
-chains of amino acids joined end to end, in twists and folds
69
What is the structure of an enzyme held together by?
-weak forces between the amino acid molecules in the protein chain
70
Explain how high temperatures denature enzymes
-break the weak forces between the amino acid molecules in the protein
-changing active site's shape so the substrate cna no longer properly bind to the enzyme
-so rate of reaction is reduced or stopped altogether
71
What do amino acids in an enzyme molecule carry?
-a charge
> positively charged and negatively charged amino acids will attract
72
How does pH affect enzyme activity?
-a change in pH affects the charges on amino acids molecules
-amino acids that attracted each other may no longer
>changes enzyme's shape along with active site
-substrate no longer fits , enzyme is denatured, enzyme activity stops
73
What is the optimum pH for:
a) salivary amylase
b) stomach protease (pepsin)
c) pancreatic protease (trypsin)
a) 6.8
b) 1.5 - 2.0
c) 7.5 - 8.0
74
What conditions are there in the stomach?
-acidic conditions (low pH)
75
What does carbohydrase break down?
-breaks down carbohydrates into simple sugars
76
What is starch broken down into and what by?
-broken down into maltose
-broken down by amylase
77
What does protease break down?
-breaks down protein into amino acids
78
What do lipases break down?
-break down lipids into fatty acids and glycerol
79
What enzymes does the mouth have?
-salivary amylase
80
Where is salivary amylase produced and found?
Where is pancreatic amylase produced and found?
-produced salivary glands, found in mouth
-produced in pancreas, found in duodenum (small intestine)
81
What is maltose broken down into and what is it broken down by?
-broken down into glucose
-broken down by maltase
82
Where is maltase produced and found?
-produced in the wall of ileum
-found in the ileum (small intestine)
83
1) Where is pepsin produced and found?
2) Where is trypsin produced and found?
3) Where is peptidase produced and found?
1) produced in gastric glands in stomach, found in the stomach
2) produced in pancreas, found in duodenum
3) produced in the wall of ileum, found in ileum
84
What does pepsin do?
What does trypsin do?
What does peptidase do?
-pepsin begins the breakdown of proteins into amino acids
-trypsin continues the breakdown of proteins into amino acids
-peptidase completes the breakdown of peptides (short chain of amino acids) into amino acids
85
Where is lipase produced and found?
-produced in the pancreas and found in the duodenum
86
What is the method to determine the rate of the amylase activity at different pHs?
-set up 4 different test tubes
-keep temperature the same using water bath
-put 1cm3 of pH 2 into one test tube, 1cm3 of pH 5 into another, 1cm3 of pH 7 into one test tube, 1cm3 of pH 11 into the next test tube
-add 1cm3 of starch to each test tube
-add 1cm3 of amylase to each test tube
-use iodine test to make qualitative observations of the colour change at each pH, the more blue-black it is the more starch is present, and the less has been broken down
-do repeats at each pH
87
What are the hazards of the amylase activity pH experiment?
-amylase solution may cause allergic reactions
-iodine solution is irritant
88
What are the precautions of the amylase pH experiment?
-wear safety goggles
-avoid contact with skin and eyes
89
What is the time taken for the disappearance of the starch inverse to?
-the rate of the reaction
90
How do you find the rate of the reaction from the time taken to reach completion?
1/time taken
91
Why might you monitor the breakdown of lipid by lipase in a different way to the way you would monitor the breakdown of starch by amylase?
-they have different products
-amylase produces sugars from starch and so you would use the iodine solution to monitor how much starch is left each time
-lipids produces fatty acids and glycerol, so you would monitor pH change (pH decreases due to the release of fatty acids)
92
Does the liver secrete enzymes?
no
93
What are 2 important roles of the liver?
-plays an important role in digestion
-and then processing food molecules that have been absorbed
94
What does the liver produce?
-bile
95
What is bile?
-substance produced in the liver, which emulsifies fats into tiny droplets with a larger surface area to prepare them for digestion of them by lipase
96
Where is bile produced and where is it stored?
-produced in the liver
-stored and concentrated in the gallbladder
97
What are the two ways bile increases the rate of digestion?
-emulsifies lipids, which physically breaks them up into tiny droplets with a larger surface area, over which lipases can work much faster
-contains the alkali sodium hydrogencarbonate
>neutralises the stomach acid and produces the optimum pH
for pancreatic enzymes to work at a faster rate
98
What does enzyme activity depend on?
-the number of collisions between the enzyme and substrate
99
What is the order of digestion?
-mouth (salivary glands)
-oesophagus
-stomach
-duodenum > ileum (small intestine)
-rectum
100
What is mechanical digestion in the mouth?
-chewing of food and churning of food in your stomach helps break it up into smaller pieces, increasing the surface area of the food, so enzymes can work on it at a much faster rate
101
Why does the stomach have strong muscular walls?
in order to churn food, and break it up into smaller pieces, increasing its surface area, over which enzymes can work on faster via mechanical digestion
102
What does hydrochloric acid in the stomach do?
-kills bacteria in food
-creates optimum pH for protease enzyme
103
How is the small intestine adapted to its function?
-villi increases surface area to maximise absorption (ileum)
-20-25 feet long, so it provides ample time for digestion
-secretes enzymes for the breakdown of food molecules (duodenum)
-secretes bile for emulsification of fats into large globules, giving them a larger surface area and neutralises pH for lipase to work at its fastest rate (duodenum)
-thin walls, decreases diffusion distance, for maximum absorption (ileum)
-muscular walls for peristalsis to help move digested food through the small intestine
104
Describe how the action of the mouth, oesophagus and stomach contributes towards the digestion of food.
-salivary glands in mouth produce saliva that contains the enzyme amylase, which starts to break carbohydrates down into simple sugars
-food is then swallowed and pushed down towards the stomach by the oesophagus using peristaltic contractions of the muscles
-contraction of muscles in the stomach churns and physically breaks down the food into smaller pieces with a larger surface area for enzymes to act on
-protease in the stomach breaks down protein
105
A student tested foods for different biological molecules. Suggest why the student recorded the results of the Sudan III solution with steak with a question mark
-positive test result is a red stained layer
-steak is already red so presence of a red layer is hard to see
106
Explain the pH obtained by the student at 0 C for the enzyme activity of lipase
-lipase activity is low at 0 degrees
-as the enzyme and substrate molecules have less kinetic energy and so there are less collisions between them
-lipase activity breaks down fats into fatty acids and glycerol, but since the lipase activity is low, the pH will not be lowered by the fatty acids
107
How does a smaller volume of a reaction container, shorter reaction time and cooler temperature reduce production costs of an enzyme?
-smaller volume and cooler temperature means it costs less to heat
-shorter reaction time reduces running costs (e.g. heating/stirring)
108
A high active life of isomerase enzyme is important in lowering the production costs of
syrup.
Explain why.
-means enzyme can be used for longer
-less money is spent on the enzyme
Biology
flashcards
Decks in class (15)
# Cards
-
Yr 8 Variation Test28
-
End of Year 8 plant test27
-
Yr 9 Diet and Bodily Functions52
-
Adaptations, interdependence and competition84
-
Biomass19
-
Sampling20
-
Decomposition29
-
Cell structure105
-
Cell division60
-
Transport in cells42
-
Gas exchange surfaces45
-
Digestion108
-
Transport Systems130
-
Plant Organisation79
-
Non-communicable diseases35
