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BMAT Biology Flashcards

1
Q

What happens as you look at distant objects? (accommodation)

A
  1. Ciliary muscles relax
  2. Suspensory ligaments pull tight
  3. Lens goes thin (less curved)
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2
Q

What happens as you look at near objects? (accommodation)

A
  1. Ciliary muscles contract
  2. Suspensory ligaments slack
  3. Less becomes fat (more curved)
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3
Q

What is the iris reflex in bright light?

A
  1. Pupil smaller
  2. Circular mussels contract
  3. Allows less light in
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4
Q

What is the iris reflex in dim light?

A
  1. Pupil larger
  2. Radial muscles contract
  3. Allows more light in
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5
Q

What is in an animal cell?

A
  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Mitochondrion
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6
Q

What is the function of the nucleus?

A
  • Surrounded by its own membrane

- Contains genetic material

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7
Q

What is the function of the cell membrane?

A
  • Forms outer surface of the cell

- Controls the substances that go in and out

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8
Q

What is the function of the cytoplasm?

A
  • Gel-like substance
  • Where most the cell’s chemical reactions happen
  • Contains enzymes which control these reactions
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9
Q

What is the function of the mitochondrion?

A

Produce energy for the cell (ATP), through respiration and regulate cellular metabolism

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10
Q

What is in a plant cell?

A
  • Cell membrane
  • Cytoplasm
  • Nucleus
  • Cell wall
  • Chloroplast
  • Mitochondrion
  • Vacuole
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11
Q

What is the function of the cell wall?

A
  • A rigid structure of cellulose
  • Surrounds cell membrane
  • Supports the cell and strengthens it
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12
Q

What is the function of the vacuole?

A
  • Large organelle that contains cell sap (week solution of sugars and salts)
  • Helps to support the cell
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13
Q

What is the function of chloroplasts?

A
  • Photosynthesis, which makes food for the plant happens hear
  • Contain chlorophyll which is used in photosynthesis
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14
Q

Describe the structure of a bacterial cell

A
  • Cell membrane
  • Cytoplasm
  • Cell Wall
  • Chromosomal DNA/ no ‘true’ nucleus (no nucleus just circular chromosome of DNA)
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15
Q

What are the levels of organisation?

A

Cells (Specialised to carry out a particular function), tissues (group fo similar cells working together to carry out a particular function e.g. xylem tissue), organs (a group of different tissues that work together to perform a function), (organ systems)

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16
Q

What is the definition and example of diffusion?

A
  • Net movement of particles from an area of higher concentration to an area of lower concentration
  • Carbon dioxide diffusing in and out of a leaf
  • Oxygen through alveoli from lungs to blood stream
  • Urea diffuses from a high concentration in liver cells to a lower concentration in the bloodstream
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17
Q

What is the definition and example of osmosis?

A
  • Net movement of water molecules across a partially permeable membrane from a region of higher water concentration of a region of lower water concentration
  • Red blood cells with water
  • Plant cells in soil (draw in water by osmosis)
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18
Q

What is the definition and example of active transport?

A
  • The movement of particles against a concentration gradient (from an area of lower concentration to an area of higher concentration), using energy related during respiration
  • In digestion, glucose absorbed bya stive transport int the villi , to be passed into the bloodstream and be taken around the body
  • Sodium potassium pump is an active transport pump
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19
Q

What is the definition of mitosis?

A

Cell division that produces TWO DAUGHTER CELLS that have the SAME NUMBER of chromosomes, so are GENETICALLY IDENTICAL

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20
Q

What is the role of mitosis?

A
  • Growth and repair

- Replacement

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21
Q

What is the definition of meiosis?

A

Cell division that produces FOUR DAUGHTER CELLS, known as GAMETES which have a SINGLE SET OF CHROMOSOMES (ARE HAPLOID), each with DIFFERENT COMBINATION of parent cell’s DNA

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22
Q

What is the role of meiosis?

A

Reducing the chromosomes number, so that the full chromosome complement is restored at fertilisation

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23
Q

What does asexual reproduction involve?

A
  • One parent

- Offspring are genetically identical

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24
Q

What does asexual reproduction produce?

A

clones

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25
Q

What does sexual reproduction involve?

A
  • Two parents

- Offspring are genetically different, leading to (increased) variation

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26
Q

In most mammals what are females and males?

A
  • Females: XX

- Males: XY

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27
Q

What is the nucleus the site of?

A

genetic material/chromosomes/genes in plant and animal cells

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28
Q

What is a gene?

A

A length of DNA that codes for a particle protein or polypeptide

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29
Q

What is an allele?

A

A particular variety of a gene

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30
Q

What does dominant mean?

A

A dominant allele is one whose effect on the phenotype of a heterozygote is identical to its effect in a homozygote

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31
Q

What does recessive mean?

A

A recessive allele is one that is only express when no dominant allele is present

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32
Q

What does genotype mean?

A

The alleles possessd by an organism

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33
Q

What does genotype mean?

A

The alleles possessed by an organism

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34
Q

What do chromosomes contain?

A

DNA

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35
Q

Describe the structure of DNA

A
  • Made up of nucleotides
  • Nucleotides consist of:
    1. Phosphate Group
    2. Sugar Group
    3. Nitrogen Base (adenine, thymine, guanine, cytosine)
  • Order of these bases determines genetic code
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36
Q

Describe the structure of DNA

A
  • Made up of nucleotides
  • Nucleotides consist of:
    1. Phosphate Group
    2. Deoxyribose Sugar Group
    3. Nitrogen Base (adenine, thymine, guanine, cytosine)
  • Order of these bases determines genetic code
  • Double helix held together by complementary base pairs
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37
Q

Outline protein synthesis

A
  1. Genes carry the code for proteins
  2. The genetic code is read as triplet and each triplet codes for an amino acid
  3. Protein synthesis involves the production of proteins from amino acids
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38
Q

What is a genetic mutation?

A
  • A random, change in the gene/DNA
  • Change in the sequence of the DNA bases and this could stop the production of a protein or it might mean a different protein is produced instead
  • This can lead to new characteristics increasing variation
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39
Q

Describe the process of genetic modification

A
  1. Take a copt of a gene from (DNA/Chromosomes of) one organisms
  2. Insertion of that gene into eh DNA of another organism
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40
Q

What are examples of genetic modification in different cell types?

A
  • Cloning
  • Pesticide resistant rape-seed plant
  • Bacterial cells modified to produce human insulin
  • Golden rice
  • Hope for cystic fibrosis and Huntington’s disease
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41
Q

What are examples of genetic modification in different cell types?

A
  • Cloning
  • Pesticide resistant rape-seed plant
  • Bacterial cells modified to produce human insulin
  • Golden rice (add gene so that wild rice appears golden and produces Beta carotene which is needed by humans to make vitamin A, for places with Vitamin A deficiency (as need VitA for good for vision)
  • Hope for cystic fibrosis and Huntington’s disease
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42
Q

What is a stem cell?

A
  • Stem Cells are cells that have not yet undergone differentiation and is a cell that can divide an unlimited number of times by mitosis
  • When it divides each new cell has the potential to remain a stem cell or to develop (differentiate) into a specialised cell such as a blood cell or muscle cell
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43
Q

What can embryonic stem cells do?

A
  • Give rise to any cell type

- Can differentiate into any cell type

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44
Q

What happens to stem cells as an animal mature?

A

Cells lose the ability to differentiate into anything as an animal matures

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45
Q

What re the different types of stem cells?

A
  • Adult stem cells: e.g. in brain, eyes and blood

- Embryonic stem cells.

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46
Q

What is the sequence of natural selection and evolution?

A
  1. Variation
  2. Leads to different survival
  3. As those best adapted survive
  4. These can repdocut and
  5. Pass on genes/alleles/characteristics to the next generation
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47
Q

What is antibiotic resistance/ MRSA an example of?

A

Evolution through nature selection

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48
Q

What are the two different types of variation?

A
  • Variation can be genetic/inherited

- Variation can be environmental

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49
Q

What is extinction and when does it happen?

A
  • Extinction cna occur if organisms cannot adapt quick enough
  • Individuals that are poorly adapted to their environment are less likely to survive and reproduce than those that are well adapted. Similarly, it is possible that a species that is poorly adapted to its environment will not survive at all, and will become extinct.
  • Some of the factors that can cause a species to become extinct:
    1. changes to the environment, such as a change in climate
    2. new diseases
    3. new predators
    4. new competitors
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50
Q

What are enzymes and what does this term mean?

A
  • Enzymes are biological catalysts
  • Biological catalyst means that it speeds up the rate of a reaction, without being used up itself and does not change the equilibrium
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51
Q

How does temperature affect enzyme action?

A
  • As temperature rises the enzyme and vibrate molecules move faster
  • Collisions happen more frequently so that substrate molecules enter the active site more often
  • When they do collide they also collie with more energy
  • Easier for bonds to be formed or brown
  • However at a certain temperature the structure of the enzyme molecule vibrates so energetically that some of the bonds holding the enzyme molecule begins to lose its shape and activity and is said to be denatured
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52
Q

How does pH affect enzyme action?

A
  • Hydrogen ions can interact with R groups of amino acids, e.g. by affecting their ionisation of the groups
  • This affects the ionic bonding between the groups which in turn affects the 3D arrangement of the enzyme molecule
  • The shape fi the active site may change and therefore reduce the chances of the substrate cutting to it
  • A pH which is very different from the optimum pH can cause denaturation of an enzyme
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53
Q

What is the role of amylase in digestion?

A

Breaks down starch into maltose (maltase converts maltose into glucose)

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54
Q

What is the role of protease in digestion?

A

Breaks down proteins into amino acids

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55
Q

What is the role of lipase in digestion?

A

Breaks down lipid into glycerol and fatty acids

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56
Q

What is genetic modification? What is recombinant DNA? What is a transgenic organism?

A
  1. In genetic modification (also known as genetic engineering), a gene from one organism is cut out and added to the DNA of another organism, often of a different species
  2. The DNA from two different organisms combined that results from genetic modification is known as recombinant DNA
  3. An organism that receives a new gene from a different species is known as a transgenic organism, or sometimes as a genetically modified (GM) organism
57
Q

What does the transgenic organism do? An example?

A
  1. The transgenic organism will manufacture the protein coded for by its new gene, so it will be able to make a new and different protein
    E.G Transgenic bacteria that have had a human insulin gene added to their DNA can make human insulin, which can be used to treat people with diabetes
58
Q

What are restriction enzymes? What are ligase enzymes?

A
  1. The enzymes used to cut out the gene from one organism are called restriction enzymes, they cut DNA at specific sites (restriction enzymes recognise specific sequences of DNA and cut the DNA at these point)
  2. The enzymes used to stick the gene into the DNA of another organism are called ligase enzymes, they join pieces of DNA together (ligase enzymes are used to join two pieces of DNA together) (Two different pieces of DNA stuck together are known as recombinant DNA)
59
Q

What are vectors? How do plasmids and viruses act as vectors?

A
  1. A vector is something that is used to transfer DNA into a cell and there are two sorts, plasmids and viruses
    - They take up pieces of DNA, then insert this recombinant DNA into other cells
    - Plasmids are small circular molecules of DNA that can be transferred between bacteria
    - Viruses insert DNA into the organisms they infect
60
Q

How are vectors used to insert DNA into other organisms?

A
  1. The DNA you want to insert (e.g. the gene for human insulin) is cut out with a restriction enzyme. The vector DNA is then cut open using the same restriction enzyme
  2. The vector DNA and the DNA you are inserting are mixed together with ligase enzymes
  3. The ligases join the two pieces of DNA together to produce recombinant DNA
  4. The recombinant DNA (i.e. the vector containing new DNA) is inserted into other cells e.g. bacteria
  5. These cells can now use the gene you inserted to make the protein you want.
61
Q

What does transgenic mean?

A

The term transgenic means the transfer of genetic material from one species to a different species

62
Q

How can large amounts of human insulin be manufactured?

A
  1. Genetically modified bacteria containing the gene for human insulin can be grown in huge numbers in a fermenter to produce insulin for people with diabetes
  2. Bacteria that contain the gene for human insulin are transgenic - this means that they contain genes transferred from another species. You can get transgenic animals and plants too
63
Q

How can genetically modified plants improve food production?

A
  1. Crops can be genetically manufactured to increase food production in lots of different ways, one is to make them resistant to insects, another is to make them resistant to herbicides (chemicals that kill plants)
  2. Making crops insect-resistant means famers:
    - Do not have to spray as many pesticides, so wildlife that does not eat the crop is not harmed
    - It also increases crop yield, making more food
  3. Making crops herbicide-resistant means farmers:
    - Can spray their crops to kill weeds, without affecting the crop itself
    - This can also increase crop yield
64
Q

What are the concerns of growing genetically modified crops?

A
  1. One is that transplanted genes may get out into the environment, for example, a herbicide resistance gene may be picked up by weeds, creating a new ‘superweed’ variety
  2. Another concern is that genetically modified crops could adversely affect food chains, or even human health
  3. Some people are against genetic engineering altogether as they worry that changing an organism’s genes might create unforeseen problems, which could then get passed on to future generations
65
Q

What can variation in a species be?

A

Genetic, environmental, or a combination of both

66
Q

Describe variation

A
  1. Most variation in animals is caused by a mixture of genetic and environmental factors
  2. Almost every single aspect of a human (or other animal) is affected by our environment is some way, however small
67
Q

What are some examples of variation not due to environmental factors?

A
  1. Eye colour e.g. genotype for blue eyes, your eyes will be blue, if you have genes increasing you levels of HGH you will grow taller than you otherwise would
  2. Hair colour (in most animals, not if someone dyes their hair)
  3. Inherited disorders e.g. haemophilia and cystic fibrosis
  4. Blood group
68
Q

What are some examples of variation that are affected by environmental factors?

A
  1. Environment can have a large affect on human growth even before some is born, for example a baby’s weight at brith can be affected by the mother’s diet
  2. And having a poor diet, whilst you are growing can stunt your growth, another environmental variation
  3. E.G. limited protein supply in your habitat you will grow quite short
  4. If you live somewhere with high levels of sunshine you skin will tan
69
Q

What are some examples of variation which are affected by both genetic and environmental factors?

A
  1. Health: some people are more likely to get certain diseases (e.g. cancer and heart diseases) because of their genes. But lifestyle also affects the risk, e.g. if you smoke or only eat junk food
  2. Intelligence: one theory is that although your maximum IQ might be determined by your genes, whether you get to it depends on your environment e.g. upbringing and school life
  3. Sporting ability: again genes probably determine your potential, but training is important too
70
Q

What does natural selection mean?

A
  • “survival of the fittest’ (explanation of how natural selection works)
    1. Living things show variation and there are not all the same
    2. The resources living things needed to survive are limited. Individuals must compete for these resources to survive, only some of the individuals will survive
    3. Some of the varieties of a particular species will have a better chance of survival
    4. Those varieties will then have an increased chance of breeding and passing on their genes
    5. This means that a greater proportion of individuals in the next generation will have the better alleles, and so the characteristics, that help survival
    6. Over many generations, the species becomes better and better able to survive
    7. The ‘best’ features are naturally selected and the species becomes more and more adapted to its environment
71
Q

What is an example of natural selection?

A
  1. Bunnies with short ears, then big ear bunny, better as hear more and so get away from predator faster. Eventually only big eared rabbits left because the rest died as did not hear trouble quick enough :(
  2. This is how populations adapt to survive better in their environment (an organism does not actually change when it is alive, changes only occur from generation to generation
  3. Over many generations the characteristic that increases survival becomes more common in the population. If member of a species are separated somehow, and evolve in different ways to adapt to different conditions, then over tome you can end up with two totally different species
  4. Another example is dark form of peppered moth was then better in industrial UK as then hide in soot as tree covered with soot
72
Q

Why do the best genes for a particular environment tend to survive?

A
  1. The individuals who are less suited to an environment are less likely to survive than those that are better suited, and so have less chance of passing their alleles on. Gradually, over time, this results in a population which is extremely well suited to the environment in which it lives
  2. REMEMBER: Variations that are caused by the environment itself (e.g. accidentally losing a finger) are not involved in natural selection. Variations in species can have either environmental or genetic causes, but only the genetic ones are passed on to the next generation and influence the evolution of the species
73
Q

What is a mutation?

A
  1. A mutation is a rare, random change in genetic material that can be inherited
  2. Mutations change the sequence of the DNA bases. This could stop the production of a protein, or it might means a different protein is produced instead
  3. This can lead to new characteristics increasing variation
  4. A mutation must happen in the gamete rather than in a somatic cell for it to be passed on to offspring
74
Q

What are mutations usually?

A
  • Harmful
    1. If a mutation occurs in reproductive cells, the offspring might develop abnormally or die
    2. If a mutation occurs in body cells, the mutant cells might start to multiply in an uncontrolled way and invade other parts of the body (which is cancer)
75
Q

What are mutations when they are not harmful?

A
  1. Some mutations have no effect at all, for example, if they occur in an unimportant part of the DNA, these mutations are said to be NEUTRAL
  2. Very occasionally mutations are BENEFICIAL and give and organism a survival advantage, so it can live in condition where the others die. This is natural selection at work
    - E.G. A mutation in a bacterium might make it resistant to antibiotics. If this mutant gene is passed on, you might get a resistant “strain” of bacteria, which antibiotics can’t kill
76
Q

Describe how bacteria can evolve and become antibiotic resistant?

A
  1. Like all organisms, bacteria sometimes develop random mutations in their DNA
  2. These can lead to changes in the bacteria’s characteristics
  3. Sometimes, they mean that a bacterium is less affected by a particular antibiotic
  4. For the bacterium, this ability to resist antibiotics s a big advantage. It is better able to survive, even in a host who is being treated to get rid of the infection, and so it lives for longer and reproduces many more time
  5. This leads to the gene for resistance being passed on to lots of offspring, it is just natural selection. This is how it spreads and becomes more common in a population of bacteria over time
    - Therefore resistance to antibiotics can increase in bacterial populations
    - Organisms can become resistant to pesticides and other chemicals in the same way
77
Q

Why is antibiotic resistance bad for people who become infected?

A
  1. This is a problem for people who become infected with these bacteria, because you can’t easily get rid of them with antibiotics
  2. Sometimes drug companies can come up with a new antibiotic that is effective, but ‘superbugs’ that are resistant to most known antibiotics (e.g. MRSA) are becoming more common
78
Q

How can antibiotic resistance be helped?

A
  1. If you are prescribed antibiotics, it is important to finish the whole course, this helps to prevent the spread of antibiotic resistance
  2. Doctors only prescribing antibiotics when they are really needed helps too
79
Q

Why do mutations happen?

A
  • Mutations can happen spontaneously, when a chromosome does not quite copy itself properly
  • However, the chance of mutation is increased by exposing yourself to:
    1. Ionising radiation, e.g. X-rays, gamma rays or ultraviolet light
    2. Chemicals called mutagen e.g. chemicals in tobacco
  • If the mutations can lead to cancer then the chemicals are called carcinogens
80
Q

What is genetic variation caused by?

A
  1. Sexual reproduction

2. Mutations in genes

81
Q

Describe the stages of natural selection

A
  1. There is variation in a population
  2. Conditions in a changing environment (a selection pressure) favours certain forms with certain adaptations (a selective advantage)
  3. The frequency of the favoured form increase (survival of the fittest)
  4. The frequency of the rest decreases, they are selected against
  5. The population looks more like those with the advantageous adaptation
82
Q

Why do antibiotic evolve very quickly?

A
  1. Very short generation time (a little as 20mins)
  2. Limited/no mutation checking
  3. Transfer of plasmids
83
Q

What does the central nervous system comprise of?

A

The brain and spinal cord

84
Q

What is the effect of drugs on synapses?

A
  • Some drugs and toxins affect how impulses pass from one neutron to the next across a synapse
    1. Some drugs stop the impulse from passing across the synapse
    2. Drugs such as curare (the South American plant toxin used in arrow poison) do this
    3. They cause complete paralysis, and even stop the person from breathing
    4. Other drugs stimulate the synapse so that once an impulse crosses the gap the impulse is repeated over and over again
  • Drugs such as strychnine do this
    5. They cause all the mussels in the body to go into a continuous spams of constriction
  • This also stops the person from breathing
85
Q

What is the effect of serotonin on synapses?

A
  1. Serotonin is a chemical that is released into synapses in the brain
  2. An increase in serotonin levels in the synapses makes us feel happier
  3. However, serotonin is normally absorbed by receptor molecules on the other side of the synapse
  4. This prevents the levels of serotonin from increasing
86
Q

What is the effect of ecstasy (also called MDMA) on synapses?

A
  1. Ecstasy is a drug that blocks the serotonin receptor sites in the synapses in the brain
  2. This prevents the serotonin from being absorbed by the receptor molecules
  3. As a result the level of serotonin in the synapse increases and this produces a feeling of wellbeing
  4. However there is evidence to suggest that the use of Ecstasy reduces memory
  5. Ecstasy can also cause severe dehydration which can result in death
87
Q

What is the structure of the thorax?

A
  • Thorax: top part of the body from the neck to the abdomen
  • Ribcage: protects the lungs
  • Inter-coastal muscles: In between the ribs, which help the lungs ventilate by changing the volume fo the ribcage
  • Diaphragm: separates the lungs from the abdomen, and moves up and down whole ventilating
  • Pleural Membranes: allows the lungs to move easily during ventilation
88
Q

Describe the internal and external structure of the mammalian heart

A

Internal:

  1. The heart has four chambers, right and left atria and right an left ventricles
  2. The right side of the heart is divided from the left by a wall of muscle tissue called the septum
  3. The atria and ventricles have valves between them, which are known as atrioventricular valves
  4. The one on the left is the mitral or bicuspid valve and the one on the right is the tricuspid valve
89
Q

What is the difference in thickness of the walls of the different chambers?

A
  1. The atrial muscular walls are thin and do not exert much pressure when they contract, but it is enough to force the blood in the atria down through the atrioventricular valves into the ventricles: the semilunar valves prevent back flow
  2. Thick, muscular walls of the ventricle increase pressure and push it out of heart and around the body.
    - The walls are much thicker than the walls of the atria because the ventricles need to develop much more force when they contract and their contraction has to push the blood out of the heart and around the body
90
Q

What happens in atrial systole?

A
  1. Both atria contract
  2. Blood flows from the atria into the ventricles
  3. Back flow of blood into the veins is prevented by closure of the valves in the veins (semi lunar valves prevent back flow)
91
Q

What happens in ventricular systole?

A
  1. Both ventricles contract
  2. The atrioventricular valves are pushed shut by the pressurised blood in the ventricles
  3. The semi-lunar valves in the aorta and pulmonary artery are pushed open
  4. Blood flows from ventricles into the arteries
92
Q

What happens in ventricular diastole?

A
  1. Atria and ventricles relax
  2. The semilunar valves in the aorta and pulmonary artery air pushed shut
  3. Blood flows from the veins through the atria and into the ventricles
93
Q

Which ventricle has a thicker muscular wall and why?

A
  1. The force produced in right side has to be smaller as blood only goes to lungs which are close to heart
  2. The left ventricle has to develop sufficient force to supply blood to all the rest of the body organs
94
Q

Why is cardiac muscle different?

A

It is myogenic so it naturally contacts and relaxes as it does nor need to receive impulses from a nerve to make it contract

95
Q

Why can individual hear muscle cells not be allowed to contract on their own?

A

Parts of the heart would contract out of sequence with other parts and so the cardiac cycle would become disorder and the heart would stop working as a pump

96
Q

How is the cardiac cycle initiated?

A
  1. In the sinoatrial node (SAN or pacemaker) in the wall of the right atrium
  2. Each time muscles of SAN contract, they set up a wave of electrical acitivity which spreads out rapidly over the whole of the atrial walls
  3. The cardiac muscle in the atrial walls responds to this excitation wave by contracting, at the same rhythm as the SAN and so all the muscle in both atria contacts almost simultaneously
97
Q

How is it that the muscles of the ventricles do not contract until after the muscles of the atria?

A
  1. This delay is caused by a feature path hear that briefly delays the excitation wave in its passage from the atria to the ventricles
  2. There is a band of fibres between the atria and ventricles which does not conduct the excitation wave
  3. As a result as the wave spreads out from the SAN over the atrial walls, it cannot pass through the ventricle walls
  4. The only route through is via a patch of conducting fibres in the septum, known as the atrioventricular node (AVN)
98
Q

How does the AVN work?

A
  1. The AVN picks up the excitation wave as it spreads across the atria and, after a delay of about 0.1 seconds passes it onto a bunch of conducting fibres called the Purkyne tissues which runs down the septum between the ventricles
  2. This transmits the excitation wave very rapidly down to the base of the septum, from where it spreads outwards and upwards though the ventricle walls
  3. As it does so, it causes the cardiac muscle in these walls to contract, from the bottom up, so squeezing blood upwards and into the arteries
99
Q

What is fibrillation?

A
  • When the excitation wave becomes chaotic, passing through the ventricular muscle in all directions, feeding back on itself and restimulating areas it has just left
  • Small sections the cardiac muscle contract while other sections are relaxing
  • The result is fibrillation, in which the heart wall simply flutters rather than contracting as a whole and then relaxing as a whole
100
Q

What is an ECG?

A
  • Electrocardiogram (ECG) machines are used to measure the spread of electricity across the heart during each beat
  • A characteristic shape is seen, and changes in these electrical waves (‘action potentials’) can indicate heart problems
  • Artificial pace makers can be fitted to people whose hearts have difficulty creating action potentials
101
Q

What is the bases of the heart?

A
  1. The heart is a major organ in the circulatory system and it is called a ‘double pump’ because blood travels through it twice in one circuit around the body: once to the lungs to revive oxygen and remove carbon dioxide and water and once again to be pumped around the body
102
Q

Why are ECGs important?

A
  • Our heart beats - or contract - approximately 70 times a minute
    1. Each contraction is tarred by a small group of cells that creates a wave of electricity
    2. This spreads out across our heart and causes the muscle fibres to contract
    3. An electrical discharge that spreads across any membrane Is called an action potential
    4. Doctors can use an ECG machine to measure the action potentials that spread across the heart muscle
103
Q

What are the three main electrical potentials?

A
  1. P wave: depolarisation fo the atria
  2. QRS wave: depolarisation the ventricles
  3. T wave: repolarisation of the ventricles
    - Heart problems such as damaged muscles or blockages are easily diagnosed using an ECG
104
Q

What are the different blood groups?

A
  • Unsuccessful blood transfusions can lead to Agglutination
    1. RBCs carry antigens, Antigen A and Antigen B are two major blood group antigens
  • The AB blood cells carry both antigens, and O blood cells do not carry either antigen
105
Q

What are agglutinins?

A
  • Agglutinins are substances that can react with a particular antigen and cause agglutination or ‘blood clumping’
  • Blood plasma may contain antibodies that can act as agglutinins with RBCs
  • People with blood group AB have neither antibody and those with blood group O have both antibodies
106
Q

Describe blood groups and blood transfusions

A
  • A blood transfusion will fail if the recipient has antibodies that will agglutinate the RBCs in the donated blood
    1. Someone can recieve blood of their own blood group
    2. Someone with blood group O can donate to anyone because their RBCs do not carry A or B antigens (they ar e’universal’ donors)
    3. Group AB patients can receive any type of blood because they do not have anti-A or anti-B antibodies, they are known as ‘universal recipients’
107
Q

What is negative feedback?

A
  • A negative feedback mechanism is an important type of control that is found in homeostasis
  • It responds when conditions change from the ideal or set point and returns conditions to this set point
  • There is a continuous cycle of events in negative feedback
    1. If the level of something rises, control systems reduce is again
    2. If the level of something falls, control systems raise is again
108
Q

What is an example of negative feedback?

A
  • Temperature
    1. Body temperature is controlled by the hypothalamus in the brain
    2. If the hypothalamus detects that the body begins to sweat to try and reduce the temperature back to the correct level
    3. Once the body temperature is back to the correct level sweating will stop
    4. If in the opposite way, the hypothalamus detects that the body is too cold then the response is that the body begins to shiver to try and raise the temperature back to the correct level
    5. Once the body temperature is back to the correct level the shivering will stop
109
Q

How is blood glucose level controlled?

A

-Insulin is a hormone produced by the pancreas that regulates glucose concentrations in the blood

110
Q

What happens if the blood glucose level is too high?

A
  1. Pancreas: Insulin is secreted into the blood
  2. Liver: Convert glucose into glycogen
  3. Decreases blood glucose levels
111
Q

What happens if blood glucose level is too low?

A
  1. Pancreas: Insulin not secreted into blood (glucagon secreted)
  2. Liver: Does not convert glucose into glycogen (glycogen into glucose and released into blood)
  3. Blood glucose levels increases
112
Q

What is the function of a white blood cell?

A

-Produce antibodies and engulfing/ingesting pathogen

113
Q

What is a pyramid of biomass?

A
  • Shows the total mass of the organisms in each trophic level, irrespective of their numbers
  • Represent the total biomass of organisms at each trophic level in a food chain
114
Q

What is biomass?

A
  • Is the total amount of living material in an organism

- Is the mass of biological material that makes up an organism

115
Q

Why are pyramids of biomass always pyramid shape?

A
  1. Some parts of the producer are not eaten (e.g. Roots), 2. Some parts are not digested, but egested and so are not absorbed,
  2. Some of the materials absorbed form excretory products
  3. Many of the materials are respired to release energy, with the loss of carbon dioxide and water.
116
Q

Why is only 10% of energy transferred from one trophic level to the next?

A
  1. Respiration
  2. Biological processes
  3. Some parts are not eaten by the next trophic level (e.g. Roots/bones)
  4. Some parts are indigestible (e.g. Fibre) so are not absorbed instead egested (so the energy is NOT taken in)!
  5. Most of energy is eventually lost to the surroundings as heat
    - Only 10% of the total energy available becomes biomass, i.e it is stored or used for growth
117
Q

What does a food chain show? How is it organised?

A
  1. Food chains show what is eaten by what in an ecosystem
  2. Food chains always start with a producer e.g. a plant
  3. Producers make (produce) their own food using energy from the Sun
  4. Producers are eaten by primary consumers, primary consumers are then eaten by secondary consumers and secondary consumers are then eaten by tertiary consumers
  5. All these organisms eventually die and get eaten by decomposers e.g. bacteria
  6. Decomposers break down (decompose) dead material and waste
  7. Each stage is called a trophic level
118
Q

Describe the carbon cycle

A
  1. (Only one arrow going down) The whole thing is ‘powered’ by photosynthesis as green plants use the carbon from carbon dioxide in the air to make carbohydrates, fats and proteins. Photosynthesis fixes carbon atoms from atmospheric carbon dioxide into organic molecules
  2. Feeding and assimilation pass carbon atoms already in organic compounds along food chains
  3. Respiration produces inorganic carbon dioxide from organic compounds (mainly carbohydrates) as they are broken down to release energy
  4. Fossilisation is when sometimes living things do not decay fully when they die due to the conditions in the soil, as decay is prevented if it is too acidic and fossil fuels are formed e.g. coal, oil, natural gas, peat
    - When plants and animals decompose they are broken down by bacteria and fungi, and these decomposers release CO2 back into the air by respiration, as they break down the material
  5. Combustion releases carbon dioxide into the atmosphere when fossil fuels are burned
119
Q

Why does the biomass of organisms get less at each level?

A
  1. Some parts of the organism are not eaten e.g. plant roots, animal bones
  2. The food cannot all be digested and absorbed, some is passed out as faeces
  3. Some of the food eaten is broken down and excreted as waste e.g. urea
  4. Some of the food is respired and used to release energy for the cells of the body
  5. Only a small part of the food is used to produce growth and new body mass
120
Q

Describe pyramids of energy transfer

A

Pyramids of energy transfer are always pyramid shape and they show the energy transferred to each trophic level in a food chain

121
Q

Why are pyramids of energy transfer always pyramid shape?

A
  1. The interactions between organisms in an ecosystem can be shown as a transfer of energy along a food chain
  2. Light energy is fixed into food molecules by plants during photosynthesis
  3. Energy is released during respiration and used for movement, growth, reproduction etc.
  4. Energy that is used for growth can be passed on to the next trophic level or the decomposers
  5. Energy used for any other process will eventually be transferred to the environment as heat
  6. Only about 10% of the energy is passed on at each level of a food chain
  7. This limits the number of trophic levels in a food chain, because eventually there is not enough energy left
122
Q

Describe the nitrogen cycle

A
  1. Feeding and assimilation pass nitrogen atoms already in organic compounds along food chains
  2. Decomposition by decomposers produces ammonia from the nitrogen in compounds like proteins, DNA and vitamins
  3. The ammonia is oxidised first to nitrite and then to nitrate by nitrifying bacteria. The overall process is called nitrification
  4. Plant roots can absorb the nitrates. They are combined with carbohydrates (from photosynthesis) to from amino acids and then proteins, as wells as other nitrogen-containing compounds
  5. Also denitrifying bacteria use nitrates as an energy source and convert them into nitrogen gas. Denitrification reduces the amount of nitrate in the soil
  6. Free-living nitrogen-fixing bacteria in soil convert nitrogen gas into ammonia, This is used by the bacteria to make amino acids and proteins, When the bacteria diem these proteins decompose, releasing ammonia back to the soil
  7. Nitrogen fixing bacteria in root nodules also make ammonia but this is converted by the plant into amino acids and other organic nitrogen compounds. Death and decomposition of the plant returns the nitrogen to the soil as ammonia
    - Lightening converts nitrogen gas in the air into various oxides of nitrogen. These dissolve in rainwater and enter the soil to be converted into nitrates by nitrifying bacteria
123
Q

What is a population and what can it do?

A
  • Is all the organisms of a particular species found in an ecosystem at any one time
  • A population cna change in size
124
Q

What are the different interactions between organisms?

A

Feeding among the organisms, competition, interaction between organisms and the environment

125
Q

What is the carbon cycle?

A
  1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
  2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
  3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide formed during respiration. The animals and plants eventually die.
  4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.
126
Q

What does the carbon cycle include?

A
  1. Photosynthesis
  2. Respiration
  3. Combustion
  4. Decomposition
127
Q

What does the nitrogen cycle include?

A
  1. Bacteria are involved
  2. Process of nitrification
  3. Process of decomposition
  4. Nitrogen fixation
  5. Denitrification
128
Q

What is nitrogen fixation?

A
  • The process of turning N2 from the air into nitrogen compounds in the soil which plants can use:
    1. Lightning: there is so much energy in a bolt of lighting that it is enough to make nitrogen react with oxygen in the air to give nitrates
    2. Nitrogen fixing bacteria in roots and soil
129
Q

Describe nitrogen fixing and where this happens

A
  1. Turns nitrogen in the atmosphere (N2), into nitrogen containing compounds e.g. NH4+
    - This can happen by lightning, but not a massive amount
    - Nitrogen fixing bacteria do this in the soil or in the roots of certain plants such as legumes
    - This is because the roots have a symbiotic relationship with the Rhizobium in root nodules, (Nitrogen Fixing Bacteria), as the plants get nitrates and the bacteria get glucose from the plant
    - The plants can use the NH4+ (ammonia) to make amino acids etc.
130
Q

Where does nitrogen come from and why is it important?

A
  1. The atmosphere contains about 78% nitrogen gas, this is very unreactive and so it cannot be used directly by plants or animals
  2. Nitrogen is needed for making proteins for growth, so living organisms have to get it somehow
131
Q

What are the 5 key stages of the nitrogen cycle?

A
  1. Nitrogen fixing
  2. Nitrification
  3. Assimilation
  4. Decomposition / Ammonification
  5. Denitrifying
132
Q

Why can plants and animals not use atmospheric nitrogen as their source of nitrogen?

A

It is a triple bonded molecule, which requires too much energy to break a part

133
Q

Why do living organisms require nitrogen?

A
  1. To make proteins (amino acids)

2. DNA (+RNA), parts of DNA have nitrogen inside

134
Q

Describe nitrification and where this happens

A
  1. It turns toxic NH4+ into useful, nitrogen oxide and then nitrates
    - Nitrifying bacteria oxidise the ammonia to nitrites and hen to nitrates
  2. NH4+ is poisonous so nitrifying bacteria turn
    - NH4+–>NO2–>NO3- (done by different nitrifying bacteria)
135
Q

Describe assimilation and where this happens

A
  1. The tree will absorb the NO3- and turn it into DNA and amino acids
  2. NO3- is not triple bonded and not particularly toxic
136
Q

Describe decomposition and ammonification and where this happens

A
  1. Living matter is broke down
  2. Denitrifying bacteria turn NO3- into N2 (and they make a living out of this, as they use nitrates as an energy source and break them down into nitrogen gas)
  3. The giraffe will eat the leaves (containing proteins) and excrete nitrogenous waste
  4. When the plants and animals die they will be broken down by decomposers by ammonification and release ammonia into the soil
137
Q

How do farmers cope with the nitrogen cycle?

A
  1. They use fertiliser, however sometime eutrophication which is bad
  2. Farmers grow bean every 3 years (crop rotation) to return some nitrogen to soil and plowing in
138
Q

What is the nitrogen cycle?

A
  1. Nitrogen gas is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules. Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil.
  2. Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.
  3. Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia.
  4. Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.
  5. In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile.

Z University (5 decks)

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