advanced information paper 1 Flashcards
1
Q
is most of the cell cycle growth and DNA replication or mitosis?
A
growth and DNA replication
2
Q
describe the events of the cell cycle that need to occur before mitosis can begin [2 marks]
A
the cell has to increase the amount of its subcellular structures [1 mark] and duplicate its DNA [1 mark]
3
Q
what are chromosomes? What do they contain?
A
coiled up lengths of DNA molecules. Each chromosome contains a large number of genes
4
Q
how many copies of each chromosome does the body normally have?
A
two - one from the ‘mother’ and one from the ‘father’
5
Q
how many pairs of chromosomes are there in a human cell?
A
23
6
Q
what is the cell cycle?
A
a series of stages where body cells in multicellular organisms divide to produce new cells
7
Q
what is the stage of the cell cycle when the cell divides called?
A
mitosis
8
Q
what do multicellular organisms use mitosis for?
A
to grow, or replace cells that have been damaged
9
Q
what are the two main stages of the cell cycle?
A
- Growth and DNA replication
2. Mitosis
10
Q
what are the three stages of growth and DNA replication?
A
- In a cell that’s not dividing, the DNA is all spread out in long strings
- Before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
- It then duplicates its DNA so there’s one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other
11
Q
what are the three stages of mitosis?
A
- The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell
- Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells - the nucleus has been divided
- Lastly, the cytoplasm and cell membrane divide
12
Q
what are eukaryotic cells?
A
a basic unit of life with a nucleus
13
Q
what is meristem tissue?
A
undifferentiated plant cells
14
Q
what are undifferentiated cells called?
A
stem cells
15
Q
what is differentiation?
A
the process by which a cell changes to become specialised for its job
16
Q
what are clones?
A
genetically identical cells
17
Q
what is a risk involved in using stem cells in medicine?
A
stem cells grown in the lab may become contaminated with a virus which could be passed on to the patient and so make them sicker
18
Q
why are some people against stem cell research?
A
some people feel that human embryos shouldn’t be used for experiments since each one is a potential human life. They feel that scientists should concentrate more on finding and developing other sources of stem cells, so people could be helped without having to use embryos
19
Q
where are stem cells found in plants?
A
in the meristems
20
Q
can cells in the meristem tissues (plant stem cells) differentiate into any type of plant cell throughout the plants entire life?
A
yes
21
Q
what are some uses of plant stem cells?
A
plant stem cells can be used to produce clones of whole plants quickly and cheaply.
They can be used to grow more plants of a rare species to prevent them being wiped out
they can be used to grow crops of identical plants that have desired features for farmers, for example, disease resistance
22
Q
where are stem cells found?
A
in early human embryos, and in certain places in adults, such as bone marrow
23
Q
why are embryonic stem cells exciting for doctors and medical researchers?
A
they have the potential to turn into any kind of cell at all
24
Q
what can be done with stem cells?
A
stem cells from embryos and bone marrow can be grown in a lab to produce clones and made to differentiate into specialised cells to use in medicine or research
25
give an example of how medicine already uses adult stem cells to cure disease
stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them
26
give two examples of how embryonic stem cells could be used to replace faulty cells in sick people
1. you could make insulin-producing cells for people with type 1 diabetes
2. you could make nerve cells for people paralysed by spinal injuries
27
what is therapeutic cloning?
a type of cloning where an embryo could be made to have the same genetic information as the patient
28
what is an advantage of therapeutic cloning?
the embryo has the same genetic information as the patient, so the stem cells produced from it would also contain the same genes and so wouldn't be rejected by the patients body if used to replace faulty cells
29
why do some people think stem cell research should be allowed?
they think that curing existing patients who are suffering is more important than the rights of an embryo.
30
is stem cell research banned in the UK?
no - it's allowed so long as it follows strict guidelines (it is banned in some countries)
31
how can stem cells be used to preserve rare plant species? [2 marks]
copies of the plant can be made by taking stem cells from the meristem of the plant [1 mark] and growing them into new, genetically identical plants (clones) [1 mark]
32
What are the levels of organisation?
Cell -> tissue -> organ -> organ system -> organism
33
What is a tissue? Give an example.
A group of similar cells that work together to carry out a particular function, e.g. Muscle tissue
34
give 3 examples of tissues in mammals
1. muscular tissue
2. glandular tissue
3. epithelial tissue
35
what does muscular tissue do?
contract to move whatever it's attached to
36
what does glandular tissue do?
make and secrete chemicals like enzymes and hormones
37
what does epithelial tissue do?
it covers some parts of the body, e.g. on the inside of the gut
38
what is an organ?
a group of different tissues that work together to perform a certain function
39
which three tissues is the stomach made out of? what is each of their purposes?
1. muscular tissue, which moves the stomach wall to churn up the food
2. glandular tissue, which makes digestive juices to digest food
3. epithelial tissue, which covers the inside and outside of the stomach
40
what is an organ system?
a group of organs working together to perform a particular function
41
what 5 organs is the digestive system made up of? what is the purpose of each of them?
1. glands (e.g. the pancreas and salivary glands), which produce digestive juices
2. the stomach and small intestine, which digest food
3. the liver, which produces bile
4. the small intestine, which absorbs soluble food molecules
5. the large intestine, which absorbs water from undigested food, leaving faeces
42
what do organ systems work together to make?
entire organisms
43
what is a problem with the 'lock and key' model?
it is simpler than how enzymes actually work. In reality, the active site changes shape a little as the substrate binds to it to get a tighter fit. This is called the 'induced fit' model of enzyme action
44
What is a catalyst?
A substance which increases the speed of a reaction, without being changed or used up in the reactikn
45
Are enzymes a catalyst ?
Yes
46
What are enzymes made of?
large proteins, which are made up of chains of amino acids that are folded into unique shapes, which enzymes need to do their jobs
47
What is the part of the enzyme called that the substrate binds to?
the active site
48
What happens when an enzyme denatures?
some of the bonds holding it together break, because of high temperatures or a change in pH, and this changes the shape of the active sight, so the substrate no longer fits.
49
What does amylase break down?
Starch
50
How do you calculate the rate of a reaction?
Either by using the formula: rate = 1000/time; or rate = the amount it has changed/time taken, to find how much something changed over time.
51
What are the three places amylase is made in?
The salivary glands, the pancreas and the small intestine
52
What do proteases break down, and what do they break it down into? What are the three places they are made?
They break down protein into amino acids. They are made in the stomach (pepsin), the pancreas and the small intestine
53
What does lipase break down? Where is it made?
Lipase breaks down lipids into glycerol and fatty acids. It is made in the pancreas and small intestine.
54
What does starch break down into?
Mainly maltose, but also some other sugars, e.g. dextrins
55
Where is bile produced and stored? Where does it work? What does it do?
Bile is produced in the Liver and stored in the gallbladder, before it's released into the small intestine where it neutralizes the stomach acid and emulsifies the fat.
56
what is substrate?
the substance that an enzyme acts on
57
explain why enzymes have an optimum pH [2 marks]
if the pH is too high or too low, it can interfere with the bonds holding the enzyme together. This changes the shape of the active site [1 mark] and denatures the enzyme [1 mark]
58
describe a practical to investigate the effect of pH on amylase activity
1. put a drop of iodine solution into every well of a spotting tile
2. place a bunsen burner on a heat-proof mat, and a tripod and gauze over the bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 25 degrees C (use a thermometer to measure the temperature). Try to keep the temperature of the water constant throughout the experiment
3. use a syringe to add 1 cm^3 of amylase solution and 1 cm^3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the tube into the beaker of water and wait for five minutes
4. next, use a different syringe to add 5 cm^3 of a starch solution to the boiling tube
5. immediately mix the contents of the boiling tube and start a stop clock
6. use continuous sampling to record how long it takes for the amylase to break down all of the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and put a drop into a well. When the iodine solution remains browny-orange, starch is no longer present
7. repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down (you could use a pH meter to accurately measure the pH of your solutions)
8. remember to control any variables each time (e.g. concentration and volume of amylase solution) to make it a fair test
59
why are enzymes needed?
starch, protein and fat molecules are too big to pass through the walls of the digestive system, so digestive enzymes have to break these big molecules down into smaller ones like sugars (e.g. glucose and maltose), amino acids, glycerol and fatty acids. These smaller, soluble molecules can pass easily though the walls of the digestive system, allowing them to be absorbed into the bloodstream
60
give an example of a carbohydrase
amylase
61
what do carbohydrases do?
convert carbohydrates into simple sugars
62
what happens to the products of digestion (maltose, amino acids, glycerol & fatty acids, etc.)?
they can be used to make new carbohydrates, proteins and lipids. Some of the glucose that's made is used in respiration
63
why is bile needed?
the hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly. Bile is alkaline - it neutralises the acid and makes conditions alkaline. The enzymes in the small intestine work best in these alkaline conditions
64
what does "emulsify fat" mean? Why does bile do this?
emulsify fat means to break the fat down into tiny droplets. This gives a much bigger surface area of fat for the enzyme lipase to work on - which makes digestion faster
65
Bile is a product of the liver. Describe and explain its role in digestion [4 marks]
bile is alkaline, so it neutralises the stomach acid and makes conditions in the small intestine alkaline [1 mark]. The enzymes of the small intestine work best in these alkaline conditions [1 mark]. It also emulsifies fat [1 mark]. This gives a bigger surface area of fat for the enzyme lipase to work on, making digestion faster [1 mark].
66
what are enzymes used in the digestive system produced by?
specialised cells in glands and in the gut lining
67
what role does the liver have in digestion?
it produces bile, which neutralises stomach acid and emulsifies fats
68
What does the stomach do to digest food?
1. it pummels the food with its muscular walls
2. it produces the protease enzyme, pepsin
3. it produces hydrochloric acid to:
- kill bacteria
- give the right pH for the protease enzyme to work (pH 2 - acidic)
69
what role does the gall bladder have in digestion?
it stores bile before it's released into the small intestine
70
what role does the pancreas have in digestion?
it produces protease, amylase and lipase enzymes. It releases these into the small intestine
71
what role does the large intestine have in digestion?
it absorbs excess water from the food
72
what role does the small intestine have in digestion?
1. it produces protease, amylase and lipase enzymes to complete digestion
2. it is where the digested food is absorbed out of the digestive system into the blood
73
what role does the rectum have in digestion?
it stores the faeces (made up mainly of indigestible food)
74
name the three parts of the digestive system that produce protease enzymes
stomach
pancreas
small intestine
75
What do you use to test for starch? what does the Benedict's test test for? what does the biuret test test for? what does the Sudan III test test for?
You use iodine to test for starch, the Benedict's test tests for sugars, the biuret test tests for proteins, and the Sudan III test tests for lipids.
76
what are the 4 steps to preparing a food sample?
1. get a piece of food and break it up using a pestle and mortar
2. transfer the ground up food to a beaker and add some distilled water
3. give the mixture a good stir with a glass rod to dissolve some of the food
4. filter the solution using a funnel lined with filter paper to get rid of the solid bits of food
77
what are the two types of sugar?
reducing and non-reducing
78
which type of sugars does the Benedict's test test for?
reducing sugars
79
what are the 5 steps to using the Benedict's test to test for sugars?
1. prepare a food sample and transfer 5 cm^3 to a test tube
2. prepare a water bath so that it's set to 17 degrees C
3. add some Benedict's solution to the test tube (about 10 drops) using a pipette
4. place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes. Make sure the tube is pointing away from you
5. if the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick-red, depending on how much sugar is in the food
80
what is the colour change for a positive test for reducing sugars using the Benedict's test?
a change from blue to green, yellow or brick-red, depending on how much sugar is in the food
81
how do you use iodine solution to test for starch?
1. make a food sample and transfer 5 cm^3 of your sample to the test tube
2. then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black
82
what is the colour change for a positive test for starch using iodine?
a change from browny-orange to black or blue-black
83
how do you use the Biuret test to test for proteins?
1. prepare a sample of your food and transfer 2 cm^3 of your sample to a test tube
2. add 2 cm^3 of biuret solution to the sample and mix the contents of the tube by gently shaking it. If no protein is present, the solution will stay blue
84
what must you always remember to include in the method for a practical?
control variables
85
what does chlorophyll do?
absorb light
86
is photosynthesis exothermic or endothermic?
endothermic
87
what is the word equation for photosynthesis?
carbon dioxide + water -> glucose + oxygen
88
what is the balanced symbol equation for photosynthesis?
6CO2 + 6H20 -> C6H12O6 + 6O2
89
what is the symbol for glucose?
C6H12O6
90
what is the rate of photosynthesis affected by?
intensity of light, concentration of CO2, temperature and amount of chlorophyll
91
what can the amount of chlorophyll in a plant be affected by?
disease (e.g. TMV) or environmental stress (e.g. lack of nutrients)
92
what does a plateau on a graph measuring the rate of photosynthesis against a limiting factor mean?
something else has become the limiting factor
93
why does a graph measuring the rate of photosynthesis against temperature drop off after a certain point?
the enzymes are damaged (denatured)
94
what is the inverse square law?
the light intensity is inversely proportional to the square of the distance
light intensity is proportional to 1/distance squared
95
if you halve the distance of a light source away from a sample, will the light intensity increase or decrease, and by how much?
The light intensity will get 4 times greater
96
if you third the distance of a light source away from a sample, will the light intensity increase or decrease, and by how much?
It will get 9 times greater
97
what does a.u. stand for?
arbitrary units
98
what is the symbol for glucose?
C6H12O6
99
which plant can be used to measure the effect of light intensity on the rate of photosynthesis?
Canadian pondweed
100
describe the way the equipment is set up for a practical to investigate the effect of light intensity on the rate of photosynthesis
cut a piece of Canadian pondweed and place it in a test-tube filled with water. Place a bung connected to a capillary tube filled with water on the test tube, and attach the end of the capillary tube to a syringe. Then set up a light source a set distance away from the test tube, placing a ruler next to it so you are able to vary the distance from the plant.
101
describe an experiment to measure the effect of light intensity on the rate of photosynthesis.
1. a source of white light is placed at a specific distance from the pondweed.
2. the pondweed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen released will collect in the capillary tube
3. at the end of the experiment, the syringe is used to draw the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured. This is proportional to the volume of O2 produced
4. for this experiment, any variables that could affect the results should be controlled, e.g. the temperature and time the pondweed is left to photosynthesise
5. the experiment is repeated twice with the light source at the same distance and the mean volume of O2 produced is calculate
6. then the whole experiment is repeated with the light source at different distances from the pondweed
102
describe how the experiment to investigate how light intensity affects the rate of photosynthesis (the pondweed experiment) could be modified to measure the effect of temperature or CO2 on photosynthesis.
the test tube of pondweed could be put into a water bath at a set temperature, or a measured amount of sodium hydrogencarbonate could be dissolved in the water (which gives off CO2). The experiment can then be repeated with different temperatures of water / concentrations of sodium hydrogen carbonate
