Biology 2b Flashcards
0
Q
What are enzymes?
A
Biological catalysts produced by living things
1
Q
Living things have chemical reactions going on inside of them, why do they need to be carefully controlled?
A
To make sure that they produce the right amounts of substances
2
Q
Why is raising the temperature not a good way to make a reaction happen quicker?
A
Because they make the useful reactions AND the unwanted ones quicker, also there’s a limit to how high the temperature can be raised in living creatures before it’s cells become damaged
3
Q
What is the definition of a catalyst?
A
A catalyst is a substance which increases the speed of a reaction, without being changed or used up in the reaction
4
Q
What are enzymes made up of?
A
They are proteins and all proteins consist of chains of amino acids which are folded into unique shapes that enzymes need to do their job
5
Q
As well as being a catalyst, what else do proteins do?
A
They act as structural components of tissues (eg muscles), hormones and antibodies
6
Q
Why do enzymes have unique shapes?
A
Their unique shape only fits onto the substance involved in a reaction so they can catalyse their reaction. Each enzyme can only catalyse one reaction
7
Q
Why can enzymes only catalyse one reaction?
A
Because the substance has to fit the enzymes special shape, if the substance doesn’t match with the enzyme, the reaction won’t be catalysed
8
Q
What is the process of an enzyme catalysing a reaction?
A
A specific enzyme and matching substance join together. The enzyme becomes uncharged after the reaction and the substance is split up
9
Q
What temperature do human enzymes work best at?
A
Around 37 degrees C
10
Q
What is an optimum pH?
A
Enzymes have an optimum pH and it is the pH that they work best at, often it is neutral pH7. If the pH is too high or too low, the bonds holding the enzyme together are changed and the enzyme changed shape and is denatured
11
Q
What is an example of an enzyme that’s optimum pH isn’t neutral pH7?
A
Pepsin (used to break down proteins in the stomach) works best at pH2. It is well suited to the acidic conditions
12
Q
What do digestive enzymes do?
A
Break down big molecules into smaller ones
13
Q
What molecules need to be broken down?
A
Starch, proteins and fats because they are too big to pass through the walls of the digestive system
14
Q
What molecules don’t need to be broken down?
A
Sugars, amino acids, glycerol and fatty acids because they are much smaller and can pass through the walls of the digestive system
15
Q
What do amylase do?
A
They convert starch into sugars
16
Q
What is the equation for amylase breaking down starch?
A
Starch -(protease/enzymes)-> Maltose etc
17
Q
Where are amylase made?
A
The salivary glands, the pancreas and the small intestine
18
Q
What do protease do?
A
Convert proteins into amino acids
19
Q
What is the equation for protease breaking down proteins?
A
Proteins -(protease/enzymes)-> Amino aicds
20
Q
Where are protease made?
A
The stomach (called pepsin in the stomach), the pancreas and the small intestine
21
Q
What do lipase do?
A
Covert lipids into glycerol and fatty acids
22
Q
What is the equation for lipase breaking down lipids?
A
Lipid -(lipase/enzymes)-> glycerol + fatty acids
23
Q
Where are lipase made?
A
The pancreas and the small intestine
24
What does bile do?
It neutralises the stomach acid and emulsifies fats
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Where is bile produced?
In the liver
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Where is bile stored?
In the gall bladder
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Where is bile released into?
The small intestine
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Why does bile neutralise the stomach acid?
Because the hydrochloric acid in the stomach makes the pH too acidic for the enzymes to work properly. Once the conditions are more alkaline, the enzymes can work
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Why does bile emulsify fats?
It breaks the fats into tiny droplets, giving it a much bigger surface area for the enzyme lipase to work on. This makes digestion faster
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Where are the enzymes used in the digestive system produced?
By specialised cells in glands and in the gut lining
31
What is the order of the digestive system?
Salivary glands, oesophagus, stomach, small intestine, large intestine...
32
What happens at the salivary glands?
Amylase enzymes are produced in the saliva
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What happens in the stomach?
Food is churned up by the muscular walls, the protease enzyme pepsin is produced. Hydrochloric acid is also produced to kill bacterial and give the right pH for the protease enzyme to work (pH2-acidic)
34
What happens at the liver?
Bile is produced to neutralise the stomach acid and emulsify fats
35
What happens in the gall bladder?
Bile is stored here before it is released
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What happens in the pacreas?
Protease, amylase and lipase enzymes are produced here and then released into the small intestine
37
What happens in the small intestine?
Protease, amylase and lipase enzymes are produced to complete digestion and the digestive food is absorbed out of the digestive system into the blood here
38
What happens in the large intestine?
Excess water is absorbed from the food
39
Respiration is catalysed by enzymes, why is this reaction really important?
Because it releases energy that the cells need to do anything
40
What is respiration?
The process of releasing energy from the breakdown of glucose and it happens in every cell in the body
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What is the most efficient type of respiration?
Aerobic respiration because it uses oxygen
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Does aerobic respiration happen in plants or humans?
Both, it happens in animals and plants all the time
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Where do most of the reactions for aerobic respiration take place?
In the mitochondria
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What is the word equation for aerobic respiration?
Glucose + oxygen -> carbon dioxide + water + energy
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What are the four examples of what the energy released by aerobic respiration is used for?
To build up larger molecules from smaller one (proteins from amino acids), In animals to allow the muscles to contract so we can move about, In mammals and birds to keep their body temperature steady and in plants to build sugars, nitrates and other nutrients into amino acids which are then built up into proteins
46
Why does blood have to flow at a faster rate if you exercise?
An increase of muscle activity requires more glucose and oxygen to be supplied to the muscle cells. Extra carbon dioxide is needs to be removed from the muscle cells, for this to happen the blood has to flow at a faster rate
47
What does physical activity do to you?
KILL YOU LOL I HATE PE! But anyways, it increases your breathing rate and makes you breathe more deeply to meet the demand for extra oxygen. Also it increases the speed at which the heart pumps
48
What is glycogen?
It is used during exercise, some glucose from food is stored as glycogen
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Where is glycogen stored?
Mainly in the liver but each muscle has its own store
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How is glycogen used?
During vigorous exercise muscles use glucose rapidly so more of the stored glycogen is converted back to glucose to provide more energy
51
When is anaerobic respiration used?
If there's not enough oxygen
52
What is anaerobic respiration?
It is the incomplete breakdown of glucose which produces lactic acid
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What is the equation for anaerobic respiration?
Glucose->Energy+Lactic Acid
54
Why is anaerobic NOT the best way to convert glucose into energy?
Because lactic acid builds up in the muscles which gets painful and causes muscle fatigue, the muscles get tired and stop contracting efficiently.
55
What is an advantage/disadvantage of anaerobic respiration?
It doesn't release as much energy but you can carry on using your muscles for a bit longer (useful in emergencies)
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What does anaerobic respiration lead to?
Oxygen debt
57
What happens if you get an oxygen debt?
You have to repay the oxygen that you didn't get to your muscles in time because your lungs, heart and blood couldn't keep up with the demand earlier on
58
How do you repay an oxygen debt?
You have to keep breathing hard for a while after you stop exercising to get more oxygen into your blood. Blood flows through your muscles to remove the lactic acid by oxidising it to harmless co2 and water
59
How are enzymes used as biological detergents?
They're mainly protein-digesting enzymes and fat-digesting enzymes (proteases and lipases) because the enzymes break down animal and plant matter, they're ideal for removing stains like food or blood. They are more effective at working at low temperatures
60
How are enzymes used to change foods?
The proteins in some baby foods are pre-digested so the baby can digest them easier using proteases. Carbohydrases can be used to turn starch syrup into sugar syrup. Also glucose syrup can be turned into fructose syrup using an isomerase enzyme (fructose is sweeter so you can use less of it-good for slimming foods/drinks)
61
Why are enzymes useful in industry?
Because they speed up reactions without the need for high temperature and pressure
62
What are the advantages of using enzymes in industry?
They are specific so they only catalyse the reaction you want them to. Using lower temperatures and lower pressure saves money as it saves energy. Enzymes work for a long time so after the initial cost of buying them, you can continue using them and they are biodegradable and therefore cause less environmental pollution
63
What are the disadvantages if using enzymes in industry?
Some people can develop allergies to the enzymes used in eg biological washing powders. Enzymes can be denatured by even a small increase in temperature, they're susceptible to poisons and changes in pH so their conditions must be tightly controlled. Enzymes can be expensive to produce and contamination of the enzyme with other substances can affect the reaction
64
What are chromosomes?
Really long molecules of DNA
65
What does DNA stand for?
Deoxyribonucleic acid
66
What does DNA contain?
All the instructions to put the organism together and make it work
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Where is DNA found?
In the nucleus of animal and plant cells in really long molecules (chromosomes)
68
What is a gene?
A section of DNA that codes for a specific protein
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How do cells make proteins?
By stringing amino acids together in a particular order
70
How many amino acids are there?
Only 20 but they make up thousands of different proteins. Genes tell the cells the order to put the amino acids in
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What else does DNA determine?
What proteins the cell produces eg haemoglobin, keratin-this determines what type of cell it is eg blood cell, skin cell
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Everyone has unique DNA, except for who?
Twins and clones
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What is DNA fingerprinting?
A way of cutting up a persons DNA into small sections and then separating them. Everyones genetic fingerprint is different so you can tell people apart by comparing DNA samples
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Where is DNA fingerprinting used?
In forensic science and paternity testing
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How is DNA fingerprinting used in forensic science?
DNA taken from a crime scene is compared with DNA taken from the suspect
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How is DNA fingerprinting used in paternity testing?
To see if a man is the father of a particular child
77
Why do some people think there should be a national genetic database?
To make is simple and easy to solve crimes as everyone's DNA is readily accessible to be compared with DNA from the crime scene
78
Why do some people disagree with there being a national genetic database?
They think it is an invasion of privacy and they worry about how safe the data would be/what else it could be used for. Also the scientific problems are that false positives can occur if errors are made in the procedure or if the data is misinterpreted.
79
What is mitosis used for?
To make new cells for growth and repair
80
Why do body cells usually have two copies of each chromosome?
One from the organisms mother and one from its father
81
How many pairs of chromosomes do human cells have?
23 pairs (46 individual chromosomes)
82
What needs to happen when a body cell divides?
It needs to produce identical cells to the original cell with the same number or chromosomes. This is mitosis
83
What is the actual definition of mitosis?
Mitosis is when a cell reproduces itself by splitting to form two identical offspring
84
What is the process of mitosis?
Non dividing cell has DNA spread out in long strings. If cell is told to divide, it must duplicate the DNA so theres one copy for each new cell. DNA is copied-forming x shaped chromosomes. Each arm of the chromosome is an exact duplicate of the other. The chromosomes line up at centre of cell and cell fibres pull them apart, the two arms go to opposite ends of the cell. Membranes form around each of the sets of chromosomes-becomes the nuclei of the two new cells. Lastly the cytoplasm divides and you have two new identical cells
85
What else uses mitosis?
Asexual reproduction-some organisms reproduce by mitosis eg strawberry plants. The offspring have exactly the same genes as the parents so theres no variation
86
How many chromosomes to gametes have?
They have half the usual number of chromosomes so that when they join up, they have the right amount. They only have one copy of each chromosome. This is how sexual reproduction produces variation
87
When does meiosis happen?
During sexual reproduction, two cells (gametes) combine to form a new individual that will have a mixture of two sets of chromosomes so it will inherit features from both parents.
88
Mitosis has one division, how many divisions are involved in meiosis?
Meiosis involves two divisions
89
What is the actual definition of meiosis?
Meiosis produces new cells which have half the normal number of chromosomes
90
What is the process of meiosis?
DNA is duplicated-one arm of each chromosome is an exact copy of the other arm. First division-the chromosome pairs line up in centre of cell. Pairs are pulled apart so each new cell has one copy of each chromosome(some from each parent goes into the new cell). Second division-chromosomes line up in centre again, arms of chromosomes are pulled apart and you get four gametes with only a single set of chromosomes in it. (After two gametes join at fertilisation, the cell grows by mitosis)
91
What is special about embryonic stem cells?
They can turn into any type of cell.
92
How can stem cells turn into any type of cell?
They are undifferentiated-they didn't change to become specialised for a job so they can become different types of cells depending on what instructions they're given.
93
Where are stem cells found?
In early human embryos-Adults have stem cells but only found in certain places like bone marrow but they aren't as versatile-they can't turn into any cell, only certain cells
94
Stem cells may be able to cure diseases, what is an example of this today?
People with some blood diseases eg sickle cell anaemia can be treated by bone marrow transplants. Bone marrow contains stem cells that can turn into new blood cells to replace the bad ones. Usually adult stem cells however scientists can extract and grow stem cells from early human embryos
95
What are some things stem cells may be able to do in the future?
They could make beating heart muscle cells for people with heart disease, insulin-producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries etc.
96
How are researchers trying to get cultures of one specific type of cell?
By trying to control the differentiation of the stem cells by changing the environment they're growing in
97
Why are some people against stem cell research?
Human embryos shouldn't be used for experiments (Potential human life). Scientists should concentrate on finding/developing other sources of stem cells. In some countries stem cell research is banned but it's allowed in the uk as long as it follows strict guidelines
99
What are peoples arguments that agree with stem cell research?
Treating people who are already alive and suffering is more important than the rights of embryos. The embryos used are generally unwanted from fertility clinics which would have just been destroyed.
100
What is the 23rd pair of chromosomes?
They are labelled XX or XY, they determine whether you are male or female
101
What chromosomes do males have?
All men have an X and a Y chromosome. The Y chromosome causes male characteristics
102
What chromosomes do women have?
All women have two X chromosomes. The XX combination allows female characteristics to develop
103
What do genetic diagrams show?
They show the possible combinations of gametes
104
What would the result of a genetic diagram show for whether a child will be a girl or a boy?
They would show a 50% chance of a girl and 50% chance for a boy, this is a 50% chance at each pregnancy e.g. someone could have four children that are all girls
105
Who is Mendel?
He did genetic experiments with pea plants. He noticed that characteristics in plants were passed on from one generation to the next. His research results became the foundation of modern genetics
106
What was Mendel's results?
Mendel had shown that the height characteristics in pea plants was determined by separately inherited "hereditary units" passed on from each parent. The ratios of tall and dwarf plants in the offspring showed that the unit for tall plants, I, was dominant over the unit for dwarf plants, t
107
What were mender's three important conclusions?
Characteristics in plants are determined by "hereditary units", Hereditary units are passed on from both parents (one unit from each parent" and hereditary units can be dominant or recessive
108
What are "hereditary units" known as today?
Genes
109
What is an allele?
Alleles are different versions of the same gene
110
What do letters represent in genetic diagram?
The letters represent alleles
111
What does homozygous mean?
If an organism has two alleles for a particular gene the same.
112
What does heterozygous mean?
If an organism has two alleles for a particular gene that are different
113
What happens if there is a dominant and recessive allele for one gene?
The dominant one is shown (dominant alleles overrule the recessive alleles)
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How can a recessive allele be shown?
If both alleles are the recessive one
115
What sort of allele causes cystic fibrosis?
A recessive allele
116
What is cystic fibrosis?
A genetic disorder of the cell membranes, it results in the body producing a lot of thick sticky mucus in the air passages and in the pancreas
117
What recessive allele causes cystic fibrosis?
f, carried by out 1 person in 25
118
Because it caused a recessive allele, what happens when someone has only one copy of the allele?
The won't have the disease because you need two recessive alleles for it to be displayed so they are called carriers
119
How can a child be born with cystic fibrosis?
Both parents must either carriers or suffers
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What sort of allele causes polydactyly?
A dominant allele
121
What is polydactyly?
A genetic disorder where a baby's born with extra fingers or toes, it doesn't usually cause any other problems so isn't life-threatening
122
What dominant allele causes polydactyly?
D and can be inherited if just one parent carries the defective allele
123
How can a child be polydactyly?
As it is a dominant gene, there are no carriers, so there is a 50% chance of a child having the disorder is one parent has the D allele
124
What is embryonic screening?
It is a way to test embryos for genetic disorders. Its possible to remove a cell from each embryo and analyse its genes before implanting them in the mother
125
Why are some people against embryonic screening?
Because it could lead to people wanting to choose how they want their baby to look/be like. The rejected embryos are destroyed even though they could have developed into humans. It implies that people with genetic problems are 'undesirable' -leading to prejudice and screening is expensive especially it for things like polydactyly where isn't affecting you
126
Why are some people for embryonic screening?
It will stop people from suffering in the future, There are laws to stop it going too far, parents cant select the gender unless its for health reasons. During IVF most of the embryos are destroyed, screening just picks the healthy one and treating the disorders costs the Government a lot of money
127
What are fossils?
Remains of plants and animals from many years ago
128
What three ways that fossils form in rocks?
Gradual replacement by minerals(most fossils are formed this way), from casts and impressions and from preservation in places where no decay for happens
129
How are fossils formed gradual replacement by minerals?
Things like teeth, shells and bones don't decay easily and can lost a long when buried, eventually they're replaced by minerals as they decay forming rock-like substances shaped like the original hard part. The surrounding sediments also turn to rock but the fossil stays distinct inside the rock and eventually someone digs it up
130
How are fossils formed from casts and impressions?
Sometimes fossils are formed when an organisms is buried in a soft material like clay the clay later hardens around it and the organism decays leaving a cast of itself, and animals burrow or plants roots can be preserved as roots. Things like footprints can be pressed into these materials when sold, leaving an impression when it hardens
131
How are fossils formed from preservation in places where no decay happens?
In amber and tar pits there's no oxygen or moisture so decay microbes can't survive. In glaciers it's too cold for the decay microbes to work and Peat bogs are too acidic for decay microbes
132
What do fossils tell us?
How many todays's species have evolved but they don't tell us where the first living thing came from
133
Why cant any of the hypotheses about how the first lis started be supported or disproved?
Because there's a lack of valid and reliable evidence because many scientists believe that many early organisms were soft-bodied so they would decay away completely. And old fossils could have been destroyed. The fossil record is incomplete
134
When does extinction occur?
When something cant evolve quick enough
135
What are the reasons why a species may become extinct?
Environment changing too quickly(destruction of habitat), A new predator, A new disease, Cant compete with new species for food, A catastrophic even (natural disasters) A new species develops (speciation)
136
What is an example of a species that became extinct
Dodos
137
What is speciation?
The development of a new species
138
What is a species?
A group of similar organisms that can reproduce to give fertile offspring
139
When does is speciation occur?
When populations of the same species become so different that they can no longer breed together to produce fertile offspring
140
What causes speciation?
Isolation and natural selection
141
What is isolation?
When populations of a species are separated. This can happen due to a physical barrier e.g. floods and earthquakes can cause barriers that geographically isolate some individuals from the main population. Conditions on either side of the barrier slight e.g. different climates. Different characteristics will become more common in each population either side due to natural selection
142
What is natural selection?
Each population shows variation they have a wide range of alleles. Their characteristics adapt to fit their environment and increase chance of survival. The alleles that control the beneficial characteristics are more likely to be passed to the next generation
143
What happens as a result of isolation and natural selection?
The individuals form the different populations will have changed so much that they won't be able to breed with each other and produce fertile offspring, the two groups will have become separate species
