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S2 Flashcards > Biology Unit 2 And 3b > Flashcards

Biology Unit 2 And 3b Flashcards

1
Q

Define “osmosis”

A
  • The diffusion of water
  • from a dilute solution to a concentrated solution
  • through a selectively permeable membrane
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2
Q

Describe “turgor”

A
  • Occurs when the solution outside of a cell is more dilute than the solution inside
  • water enters a plant cell through the cell membrane by osmosis and the vacuole increases in size
  • this pushes the cell membrane against the cell wall, increasing the pressure inside the cell, making it turgid
  • turgor pressure prevents cells absorbing too much water and lysing
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3
Q

Why is turgor necessary for non-woody plants?

A
  • Turgor pressure is essential in providing support for plant cells, and allows plants to stand upright
  • The importance of turgor for non-woody plants is highlighted during periods of drought. When water is in short supply, and plants do not get enough water they wilt, become flaccid and die
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4
Q

Why do animal cells not become turgid?

A

-Animal cells have no cell wall to exert turgor pressure on, and so they continue to absorb water by osmosis through the cell membrane
- until they become too full and eventually lyse

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5
Q

Describe “plasmolysis”

A
  • Occurs when the solution inside a cell is more dilute than the solution outside
  • meaning water diffuses out through the cell membrane by osmosis
  • if the plant loses too much water this way a condition called plasmolysis occurs where the vacuole of a cell shrinks, pulling the cell membrane away from the cell wall, causing it to wilt and die
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6
Q

Differences in structure between a turgid cell and a plasmolysed cell

A

Turgid:
- vacuole is full
- cell membrane pushes against cell wall causing it to stretch
- the cell is able to stand upright
- cell is firm

Plasmolysed:
- vacuole is less full
- cell membrane shrinks and detracts from the cell wall as a result of this
- cell is not supported, and begins to wilt
- cell is flaccid

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7
Q

Prescribed Practical 2.1a: investigate the process of osmosis by measuring the change in mass of plant tissue

A

Procedure:
1. You will be given a range of sucrose solutions of different concentrations (i.e. 5%, 10%, 15% and 20%)
2. Set up and label a number of beakers, one with each solution, and one containing pure water.
3. Using a cork borer cut five potato cylinders
4. Weigh each cylinder and place one in each solution
5. Leave the beakers for at least an hour
6. Pat dry and reweigh each cylinder
7. Record the results in a table with the headings “% concentration of sucrose in beaker” “initial mass” “final mass” “change” “% change”
8. Draw a line of best-fit graph of % change in mass against concentration of sucrose
9. Describe and explain the results

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8
Q

Prescribed practical 2.1b: Investigating osmosis by investigating the change in mass of simulated cells using Visking tubing

A

Procedure:
1. Add 5% sucrose solution to a section of Visking tubing, ensuring it is tied securely at each end
2. Dry the outside of the tubing if necessary and weigh it and it’s contents
3. Add the Visking tubing to a beaker of water and leave for one hour
4. Dry the outside of the tubing and reweigh
5. Describe and explain the results obtained

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9
Q

Define “transpiration”

A

1 mark definition:
Evaporation of water from mesophyll cells followed by diffusion of water vapour through air spaces and stomata

3 mark:
- osmosis of water from the xylem to the spongy mesophyll cells through the cell membrane
- evaporation of water from the surface of the mesophyll cells into the intercellular air spaces
- diffusion of water from the air spaces into the atmosphere through the stomata

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10
Q

List the uses of water in a plant (SPAT)

A
  • Turgor support
  • Photosynthesis
  • Active transport - The movement of water in order to transport minerals from the roots of plants to the leaves and stem
  • Transpiration
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11
Q

How to measure rate of water uptake using a bubble potometer

A
  • Uses a leafy shoot to measure the rate of water uptake in a plant
  • as water evaporates through the stomata of the shoot it will suck up more water through the potometer.
  • the distance travelled by the bubble in a given time period is the rate of water uptake.
  • the reservoir is used to reset the apparatus so that replicate results, or results under different environmental factors may be recorded.
  • air leaks will hinder the investigation so it is necessary that the apparatus is properly sealed.
  • to help minimise unwanted air in the water column start by assembling the apparatus under water initially
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12
Q

List the environmental factors that affect transpiration, how they affect transpiration and how this is simulated using a bubble potometer

A

Wind speed - faster wind speed equals faster rate of transpiration
- can be simulated by placing a fan at various distances from the shoot

Temperature - higher temperature equals faster rate of transpiration
- can be simulated using a lamp at various distances from the shoot

Humidity - high humidity equals low rate of transpiration
- can be simulated by placing a clear polythene bag over the shoot

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13
Q

How does leaf surface area affect the rate of transpiration?

A
  • Not an environmental factor, however it will also affect the rate of transpiration
  • larger leaves have more stomata for water to evaporate and diffuse through
  • transpiration can occur more frequently in the same period of time
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14
Q

Prescribed Practical 2.2a)i): use a potometer to investigate the factors affecting the rate of water uptake by a plant

A

Procedure (bubble potometer):
1. Set up a bubble potometer by attaching the shoot of a plant to the neck of the apparatus. Take the necessary precautions to minimise air leaks
2. Calculate the rate of water uptake for a particular environmental factor, i.e. still air
3. Repeat to obtain a more reliable result
4. Reset the apparatus and adjust the EF being measured, i.e. add a fan to simulate windy conditions
5. Repeat steps 2 and 3
6. Record the results in a table with the headings “Environmental condition”, “position of bubble/mm”, “at start”, “at end”, “difference in bubble position/mm”, “time/min” and “rate/ mm/min”

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15
Q

Prescribed Practical 2.2a)ii): use a potometer to investigate the factors affecting the rate of water uptake by a plant

A

Procedure (mass potometer):
1. Set up a mass potometer by putting the shoot of a plant in the neck of a conical flask, filled with water. Take the necessary precautions to minimise air leaks
2. Calculate the rate of water uptake for a particular environmental factor, i.e. still air
3. Repeat to obtain a more reliable result
4. Reset the apparatus and adjust the EF being measured, i.e. add a fan to simulate windy conditions
5. Repeat steps 2 and 3
6. Record the results in a table with the headings “Environmental condition”, “mass of flask and shoot/g”, “at start”, “at end”, “difference in mass/g”, “time/hours” and “rate/g/hr”

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16
Q

Prescribed Practical 2.2b): use the washing line method to investigate the factors affecting the rate of water loss from plant leaves

A

Procedure:
1. Detach six leaves from a tree
2. Smear petroleum jelly over the cut stalks to seal and waterproof them
3. Measure the mass of each leaf, and then using paperclips, hang them on a line of string suspended between two retort stands
4. Suspend half the leaves from a line that is at a high temperature (30 degrees Celsius)
5. After 24 hours reweigh the leaves and calculate the average loss of mass for each environmental condition
6. Describe and explain the results

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17
Q

State three components of the circulatory system, and describe its functions

A

Components:
- Blood vessels;
- Blood components; and
- The heart

The two main functions of the circulatory system are to transport blood components and other substances in the blood (hormones, products of digestion/respiration, etc.), and to protect against disease (white blood cells)

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18
Q

Describe the structure of red blood cells, state their purpose and describe how they are adapted for this function

A
  • ovular, bi-concave, and have no nucleus
  • designed to carry oxygen around the body
  • they are adapted for this purpose thusly:
    1. Contain iron rich haemoglobin which carries oxygen
    2. No nucleus allows for more volume inside, and more space for haemoglobin
    3. Bi-concave structure allows for greater surface area for diffusion of oxygen
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19
Q

State the function of white blood cells, and describe the two types

A
  • White blood cells are designed to protect against disease
  • there are two types which serve different functions
  1. lymphocytes are produced in the lymph nodes, and produce complimentary antibodies for specific antigen
  2. phagocytes surround, engulf, and digest foreign microorganisms through phagocytosis
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20
Q

Describe the structure and function of platelets

A
  • They are very small
  • they assist in blood clotting and scab formation
  • they function by converting the rote in fibrinogen into fibrin
  • the fibrin forms a mesh network around other blood components, preventing them from escaping
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21
Q

Describe the structure and function of plasma

A
  • Plasma is the liquid component of the blood
  • it is responsible for the transport of the blood cells, platelets, absorbed products of digestion (i.e. glucose and amino acids), hormones, CO2, and urea
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22
Q

Describe the effect of placing red blood cells in water (cell lysis)

How is this prevented in the plasma?

A
  • when red blood cells are placed in water they absorb water by osmosis through the cell membrane
  • but red blood cells do not have a cell wall to exert turgor pressure on so continue to absorb water until they burst
  • this is called cell lysis
  • lysis is prevented in the plasma through the presence of salts and other chemicals to regulate the concentration of the solution
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23
Q

Describe the structure and function of the arteries and how these adaptations relate to their function

A

Structure and function:
- Carries oxygenated blood away from the heart under high pressure
- has a thick wall of smooth muscle and elastic tissue, and a relatively narrow lumen
- does not have valves

How this relates to function:
- have thick walls of smooth muscle and elastic tissue to smooth the flow of blood at constant high pressures
- muscles relax and elastic fibres become taut when blood is pulsed through; then the muscles contract and elastic fibres recoil after the pulse to maintain high pressure
- the elastic fibres provide strength to prevent bursting

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24
Q

Describe the structure and function of the veins and how these adaptations relate to their function

A

Structure and function:
- Carries deoxygenated blood to the heart under low pressure
- relatively thin wall of smooth muscle and elastic tissue and a large, irregular lumen
- has valves

How this relates to its function:
- By the time the blood reaches the veins there is no pulse so the wall of smooth muscle and elastic tissue does not need to be as thick
- valves maintain unidirectional flow of blood and prevent back flow due to low pressure
- large and irregular lumen also decreases friction and further aids flow of blood

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25
Q

Describe the structure and function of the capillaries and how these adaptations relate to its function

A

Structure and function:
- Carries blood from arteries to veins under low pressure
- wall is only one-cell thick
- has no valves

How this relates to its function:
- One-cell thick wall is permeable, and allows for more efficient diffusion of products between capillaries and body cells, or vice versa
- low pressure slows the flow of blood and allows more time for diffusion to occur

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26
Q

List and describe the 4 blood vessels inside the heart, including the location the blood flows to/from

A

Pulmonary vein - carries oxygenated blood from the lungs to the heart
Aorta - largest artery in the body, all other arteries are subsidiaries of the aorta (excl. pulmonary artery)
- carries oxygenated blood from heart to body cells
Pulmonary artery - carries deoxygenated blood from the heart to the lungs
Vena Cava - largest vein in the body, all other veins converge into the vena cava (excl. pulmonary vein)
- carries deoxygenated blood from body cells to the heart

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27
Q

Name and describe the directions and locations of the 3 blood vessels in the liver

A

Hepatic artery - carries oxygenated blood and glucose to the liver
Hepatic portal vein - carries absorbed products of digestion from the ileum to the liver
Hepatic vein - carries glucose and amino acids from liver to the body cells; as well as returning deoxygenated blood to the heart

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28
Q

Name and describe the directions and locations of blood flow in the 2 blood vessels in the kidneys

A

Renal artery - carries urea rich blood from body cells to kidneys for excretion
Renal vein - carries purified, deoxygenated blood from kidneys to the heart

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29
Q

Describe what is meant by the terms “double-circulatory system” and “cardiac output”

A
  • one circulation goes to and from the heart and lungs
  • the other goes between the heart and body cells
  • cardiac output is the volume of blood that leaves the heart every minute
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30
Q

Describe the structure and function of the 4 chambers of the heart

A

Left atrium - blood is delivered here via the pulmonary vein
- blood flows from left atrium to left ventricle; backflow is prevented by the bicuspid valve, forcing unidirectional flow of blood
- very thin wall of muscle
Left ventricle - blood is delivered here from the left atrium
- blood leaves through the aorta
- has a very thick muscular wall to pump blood around the whole body and under high pressure

Right atrium - blood is delivered here via the vena cava
- blood flows from the right atrium to the right ventricle; backflow is prevented by the tricuspid valve, forcing unidirectional flow of blood
- very thin wall of muscle
Right ventricle - blood is delivered here from the right atrium
- blood leaves through the pulmonary artery
- has a thick muscular wall to pump blood to the lungs; however not as thick as the left ventricle as blood does not have to travel as far or as under as high pressure

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31
Q

Describe the short term effects of exercise on pulse rate

A
  • as we exercise muscles are contracting more vigorously and more frequently, so need more energy
  • so blood pressure and cardiac output increase in order to supply the cells with more oxygen and glucose
  • in order for respiration to occur, supplying cells with the energy they need to continue exercising
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32
Q

Describe and explain the effects of regular exercise on the heart

A
  • resting heart/pulse rate will be lower
  • lower resting blood pressure and higher resting cardiac output
  • lower peak blood pressure and higher peak cardiac output while exercising
  • quicker recovery rate after exercising
  • because the heart muscle is stronger, and can pump more blood per beat
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33
Q

Define “chromosome”

A
  • A long strand of DNA
  • found in the nucleus of a cell
  • occur in functional pairs in all cells, with the exception of gametes and bacteria
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34
Q

Define “gene” and “allele”

A

Gene - short strands of DNA
- found on chromosomes
- code for a particular characteristic/protein

Alleles - alternate forms of the same gene
- can be dominant or recessive

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35
Q

Describe the structure of deoxyribonucleic acid (DNA)

A
  • Two antiparallel polynucleotide strands with interlinking bases form a double helix
  • each mononucleotide consists of a deoxyribose sugar, and a phosphate group which form the backbone of the DNA
  • each mononucleotide also has one of 4 possible bases, which each have a complimentary pair they join to
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36
Q

Describe the base triplet hypothesis

A
  • The bases along the coding strand of the DNA molecule form the genetic code
  • a sequence of 3 bases codes for a specific amino acid
  • this triad of bases is known as a base triplet
  • a sequence of specific amino acids codes for a particular protein, so it is important the bases are in the correct order so that the correct protein can be produced
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37
Q

Define “mitosis” and describe the process by which mitosis occurs

A

Definition - cell division
- where the exact duplication of chromosomes takes place
- producing 2 daughter cells that are genetically identical to the parent cell, and each other

Process:
- each chromosome duplicates lengthwise, duplicating all genetic material, into 2 identical chromatids held together by a centromere
- the new chromosomes line up along the equator of the cell
- mitoric spindle fibres attach to the centromere of the chromosome and pull the 2 chromatids to opposite poles of the cell, dividing it in two
- both daughter cells produced contain all of the same chromosomes as the other as well as the parent cell

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38
Q

Define “meiosis” and describe the process by which meiosis occurs

A

Definition - type of cell division known as reduction division
- where one chromosome from each pair passes into each daughter cell
- only takes place in the sex organs to produce 4 genetically different gametes (sperm/egg cells)

Process:
- All chromosomes duplicate, forming two new chromosomes, each with a pair of sister chromatids joined by a centromere
- chromosomes are arranged in homologous pairs
- homologous pairs randomly align along the equator of the cell, this is independent assortment
- mitoric spindle fibres attach to the centromere pulling entire chromosomes to opposite poles
- each cell divides again so that one chromatid from each chromosome is present in the new daughter cell
- prior to this they sister chromatids overlap, so that when they are pulled apart they swap genes, this is genetic crossover
- 4 genetically different, haploid daughter cells are produced

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39
Q

Define “dominant” and “recessive” alleles

A

Dominant - will be expressed as the phenotype in both the homozygous and heterozygous forms

Recessive - will only be expressed as the phenotype in the homozygous form

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40
Q

Define “homozygous” and “heterozygous”

A

Homozygous - when the two alleles carried for a specific trait are the same

Heterozygous - when the two alleles carried for a specific trait are different

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41
Q

Define “genotype” and “phenotype”

A

Genotype - the genetic makeup of an organism for a given trait
- influenced solely by genetics, expressed as letters (i.e. Tt, HH, aa)

Phenotype - the version of a trait that is outwardly expressed
- influenced by genetics and environmental factors

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42
Q

Define “gamete” and give the number of possible gamete combinations in the form of

A

Gamete - haploid (23 chromosomes) sex cell
- fuse with another gamete to form a zygote (new life)
- sperm or eggs

There are 223 possible combinations

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43
Q

Describe the purpose of a Punnett square, and explain how one is used

A
  • A Punnett square is used to calculate the frequency of a particular genotype in offspring based on the genotypes of the parents, for a particular trait
  • The genotype of one parent is written along the top of a 2x2 box, and the genotype of the other parent is written down the side
  • the possible genotypes of the offspring are written in the spaces in the box
  • this is then used to calculate the probability of each of the possible genotypes for the particular trait
44
Q

Describe the ratio of outcomes if two F1 generation (purebred) parents are bred

A

t t
T Tt Tt
T Tt Tt

0: 4: 0
Homo.dom: hetero: homo.rec

100% dominant phenotype

45
Q

Describe the ratio of outcomes if an F1 generation parent and F2 generation parent are bred

A

T T 2: 2: 0
T TT TT Homo.dom: hetero: homo.rec
t Tt Tt 100% dominant phenotype

Or

  t    t                       0: 2: 2 T   Tt  Tt                     Homo.dom: hetero: homo.rec t    tt   tt                     50% dominant phenotype
                               50% recessive phenotype
46
Q

Describe the ratio of outcomes if two F2 generation parents are bred

A

T t
T TT Tt
t Tt tt

1: 2: 1
Homo.dom: hetero: homo.rec

75% dominant phenotype
25% recessive phenotype

47
Q

Describe the purpose of a test cross and how to use one

A
  • A test cross is used to find the unknown genotype of an animal with a dominant phenotype by breeding it with a purebred animal with a recessive phenotype
  • you start by procuring both animals and breeding them out
  • if any of the offspring display the recessive phenotype we can conclude that the unknown genotype is heterozygous
  • if all of the offspring display the dominant phenotype we can conclude the unknown genotype is homozygous dominant
48
Q

Describe the purpose of a pedigree tree, and how one is used

A
  • A pedigree tree/diagram is used to show how genetic conditions are inherited
  • squares represent males, circles represent females, and they are colour-coded to differentiate between sufferers and those who are normal
  • if a shape has both colours, the person is a carrier
  • you can use it by looking at who is a sufferer of a disease, and go backwards, up the tree to find out where they inherited it from
49
Q

Describe how recessive inherited conditions are inherited, use an example

A
  • in order to suffer from a recessive inherited condition, such as cystic fibrosis, you must carry both alleles (ff)
  • it is possible to be a carrier if one is heterozygous for the trait, as in this form it is overpowered by the dominant allele (Ff)
50
Q

Describe how dominant inherited conditions are inherited, use an example

A
  • In order to suffer from a dominant inherited condition, such as Huntington’s Chorea, you only need one allele for the trait (HH or Hh)
  • this means if you carry any information for the trait you will be a sufferer and cannot be a carrier (hh is normal)
51
Q

Describe how sex-linked inherited conditions are inherited, use an example

A
  • Sex linked diseases, such as haemophilia, are caused by a gene mutation on the X sex chromosome
  • this means your chances of contracting the disease are dependent on sex
  • females need both recessive X chromosomes for the disease in order to be a sufferer, so they are less likely to contract the disease, and are able to be carriers
  • males however only need one recessive X chromosome to be a sufferer, and as the other sex chromosomes in males is a Y, they are unable to be carriers
52
Q

Describe how Down’s syndrome is caused, and how test for it using genetic screening

A
  • Down’s syndrome is caused by a chromosomal mutation causing the presence of an extra chromosome on the 21st pair
  • the mutation occurs in the egg cell, causing it to have to 24 chromosomes instead of 23, and the child to have 47 chromosomes instead of 46,
  • it is not genetically inherited
  • mutated eggs occur more in older women as they are older, and the egg cells have more time to mutate
  • Down’s syndrome can be tested for using a type of genetic screening called amniocentesis where amniotic fluid containing foetal cells is extracted from the amniotic sac using a needle, which can then be cured and tested for genetic abnormalities
53
Q

Discuss the moral implications of amniocentesis

A
  • Who should make the decision to screen people?
  • Also, if the screening comes back with a positive result, how should the parents proceed, is abortion the best option?

Arguments for yes - prevents a child growing up with a poor quality of life
- more time may need to be spent caring for the child with the abnormality, making the parents’ other children potentially feel neglected

Arguments for no - the child does not have a say in the matter
- everyone has a right to life, and it is ethically wrong to ‘kill’ the foetus
- it is banned in many religions, and some countries

54
Q

Should the results of genetic screening be shared with potential employers or insurers

A
  • if the screening finds that someone is at increased risk for a disease that may lower their life expectancy it may have implications on their wider life
  • they may find it harder to get certain jobs
  • and insurance companies may not insure them, or charge a higher premium if they thought they would die sooner
55
Q

Define “genetic engineering”

A

The modification of the genome of an organism to introduce desirable characteristics

56
Q

How is genetic engineering used to produce insulin

A
  • human insulin gene is cut using a restriction enzyme to produce sticky ends
  • bacterial plasmid is cut using the same restriction enzyme to produce complimentary sticky ends
  • the human insulin gene is joined to the plasmid using complimentary base pairings
  • the modified bacterium is then put in a fermenter to reproduce, producing millions of bacteria with the modified plasmid
  • then the bacteria is extracted from the fermenter, the insulin is extracted from the bacteria, purified and packaged, ready for use
  • this process is called downstreaming
57
Q

Advantages of genetic engineering compared to traditional methods of extraction

A
  • animals such as pigs and cattle don’t have to be culled
  • the extraction process was expensive, time consuming, and limited by the number of animals sent to the abattoir
  • less chance of infection or body rejecting the insulin
  • using animal insulin raises ethical issues for some people
  • human and animal insulin have different structures, so animal insulin isn’t as effective for humans
58
Q

Identify the 2 types of variation

A

Continuous and discontinuous

59
Q

How are these graphed? Give 2 examples of each type of variation

A

Continuous - histogram
- height and hand span

Discontinuous - bar chart
- tongue rolling and hand dominance

60
Q

What are the two causes of variation, discuss both

A

Genetic variation - a result of mutations in chromosomes or genes
- also a result of independent assortment and genetic crossover during meiosis

Environmental variation/factors - caused by level of exercise, quality of nutrition, etc

61
Q

Define “evolution”, “extinction”, and “endangered”

A

Evolution - gradual change in the phenotype of a population
- in response to a change in the environment
- and can result in the formation of a new species
- is an ongoing process over many generations

Extinction - a species which has no living examples left
- that died out over many generations
- existence only confirmed due to fossilised remains

Endangered - a species that is close to extinction

62
Q

Describe the process of natural selection, and explain how this can impact evolution

A
  • There is variation in the phenotypes of an organism
  • there is competition for resources, ensuring that only the best adapted thrive (survival of the fittest)
  • as a result, the better adapted organisms will survive and reproduce, passing on their advantageous traits
  • often at the expense of the less adapted organisms.
  • This means that the less adapted organisms die off, and more of the population possess the advantageous trait
  • they will continue to thrive and reproduce, until the entire population evolves to have the better adapted phenotype; or even form a new species
  • and the less adapted phenotypes will all go extinct as a result of not being able to respond to a change in the environment
63
Q

Give and describe an example of natural selection in bacteria

A
  • Anti-biotic resistance
  • bacteria reproduce and one cell mutates to be resistant to anti-biotics
  • the bacteria are then treated with anti-biotics
  • mutated bacteria survive and multiply, passing on the gene for ABR, ensuring all future generations possess the trait
  • the bacteria evolves into a superbug
64
Q

Define “fossil” and explain how they are used to prove that evolution has taken place

A
  • the remains of a decaying organism that have been preserved in rock for millions of years
  • the remains can be carbon dated to determine when the fossil was formed
  • the fossil is then compared to the modern animal
  • the differences in the remains of an animal today, and that animal millions of years ago are proof of evolution
65
Q

Describe the process of artificial selection, or selective breeding

A
  • human intervention in the evolution of an organism
  • the organism is selected for its desirable phenotypes, i.e. yield (meat, milk, crop), appearance, disease resistance and shelf life
  • these are bred with other organisms with other desirable traits
  • this is done over many generations until all offspring show the desired characteristic
66
Q

State the name and describe the function of the male reproductive organs

A

Penis - to be inserted into the vagina
Testes - produce sperm
Sperm duct - transports sperm from the testes to the urethra
Urethra - tube that carries sperm out of the penis
Scrotum - holds and protects the testes at a lower than body temperature
Prostate - gland that produces a fluid to nourish sperm

67
Q

State the name and describe the function of the female reproductive organs

A

Vagina - opening that the penis is inserted into, and the place that sperm is placed
Cervix - the opening between the uterus and the vagina
- widens during birth
Ovary - produces ova (eggs)
Oviduct - carries ova from the ovary to the uterus
- the site of fertilisation
Uterus - will nourish the foetus if fertilisation and implantation are successful

68
Q

Describe the parts of a sperm cell and how they are adapted for their function

A

Flagellum - allows the sperm to swim to the egg
Mitochondria - produce energy for swimming
Streamlined head - allows for more ease of motion
- contains an enzyme that allows the sperm to decompose the cell membrane of the ovum, so that the nuclei can fuse
Haploid nucleus - allows the sperm to fuse with the egg to produce a diploid zygote

69
Q

Describe the processes of fertilisation and implantation

A
  • fertilisation takes place in the oviducts
  • it occurs when the haploid nuclei of the sperm and egg fuse together to form a diploid zygote
  • as the zygote begins to divide by mitosis it becomes and embryo, and is nourished by the cytoplasm of the ovum
  • the embryo moves from the oviduct into the uterus as it divides, until it reaches the 8-16 cell stage, where it implants in the uterus lining
  • the embryo then begins to differentiate into a variety of cell types and organs, including the placenta
  • as the foetus develops a protective sheath called the amnion forms around it
  • this is filled with amniotic fluid which nourishes and cushions the foetus as it develops and differentiates
70
Q

Describe the structure and function of the placenta and the umbilical cord

A
  • the placenta has a large surface area for diffusion of oxygen, nutrients, carbon dioxide and urea between the mother and the foetus
  • the villi between the placenta and uterine wall further increases surface area for diffusion
  • the umbilical cord also forms, this contains the umbilical vein and umbilical artery
  • the umbilical vein carries oxygen and nutrients to the foetus from the mother, and the umbilical artery carries carbon dioxide and waste products from the foetus to the mother
71
Q

State the sex hormones for both males and females, and where they are produced; list the secondary sexual characteristics caused as a result

A

Males:
- testosterone, produced in the testes
- body, facial, and pubic hair develop
- the sexual organs get larger
- muscles get larger and shoulders widen
- larynx gets larger and lowers down, voice deepens
- sexual awareness and drive increase

Female:
- oestrogen, produced in the ovaries
- pubic and underarm hair growth
- the sexual organs and breasts get larger
- pelvis and hips widen
- menstruation begins
- sexual awareness and drive increase

72
Q

Describe the purpose and stages of the menstrual cycle, the average length of time for each stage, and when fertilisation is most likely to occur

A
  • the purpose of the menstrual cycle is to prepare the female reproductive system for pregnancy,
  • by controlling the monthly release of an egg and renewal of the uterus lining
  • Day 1-5; menstruation: the uterus lining is shed out through the vagina
  • Day 6-12: the uterus lining begins to be rebuilt
  • Day 13-15; ovulation: an egg is released from the ovaries and is wafted to the oviducts for fertilisation
  • Day 16-28: the uterus lining is kept thick in the hopes of implantation, but if this does not occur the cycle continues as normal
  • fertilisation is most likely to occur between days 11 and 17 (days immediately pre/proceeding ovulation) as sperm can survive up to 3 days in most cases
73
Q

State the two primary female sex hormones and their effects on the menstrual cycle

A
  • the menstrual cycle is controlled primarily by the female sex hormones oestrogen and progesterone
  • oestrogen concentration rises as the cycle progresses and stimulates the rebuilding of the uterus lining
  • when concentration is high enough, it triggers the release of an egg, after this oestrogen concentration begins to fall again
  • when this happens, progesterone concentration rises and keeps the uterus lining thick, concentration begins to decrease if implantation does not occur
  • this causes the uterus lining to be shed out through the vagina
74
Q

Explain some of the causes of infertility

A
  • failure to produce eggs
  • sperm ducts/oviducts may be blocked or twisted due to infection
  • complications due to an STI
  • uterus lining is not thick enough for implantation
  • vagina may be a hostile environment to sperm (too hot/acidic or lining too thick)
  • males may not produce a lot of sperm, or sperm produced are deformed due to smoking or excess drinking
75
Q

Explain some methods used to overcome infertility

A

Fertility drugs (hormones)
- woman is given hormone supplements to stimulate release of multiple eggs
- can help in cases of low egg production but other issues may require other treatments, such as IVF

In-Vitro Fertilisation (IVF):
- the woman is given fertility drugs to stimulate the release of multiple eggs, which are then collected surgically
- these are fused with the sperm of either the partner or donor in a Petri dish, forming multiple embryos
- a few of the embryos are then placed in the mother’s uterus artificially in the hope that one will implant successfully, but minimise the chance of multiple births

76
Q

Describe the three common methods of contraception and give two examples of each
Provide one alternative method of contraception

A

Mechanical - provides a physical barrier between the penis and vagina
- examples of this include the male condom and the female condom

Chemical - use of drugs or hormones to alter the woman’s menstrual cycle
- examples include the contraceptive pill and the contraceptive implant

Surgical - surgically altering the reproductive system of a man or woman to prevent a pregnancy
- examples include vasectomy (cutting of sperm ducts) and female sterilisation (cutting of oviducts)

Natural family planning/rhythm method - some people are opposed to contraception for ethical or religious reasons but still want to reduce the likelihood of becoming pregnant
- so they use this method which involves tracking the woman’s menstrual cycle and only having sex when they are likely not to get pregnant
- this is not very reliable however as the menstrual cycle is irregular in most women so it is hard to pinpoint exactly when ovulation occurs

77
Q

State the advantages and disadvantages of each method of contraception

A

condom (male and female);
Adv:
- easily obtainable
- also protects against transmission of STIs
Disadv:
- unreliable if used incorrectly

Contraceptive pill;
Adv:
- very reliable if used regularly and correctly (21 consecutive days per cycle)
Disadv:
- can increase risk of weight gain, mood swings, and blot clots

Contraceptive implant;
Adv:
- very reliable
- can work for up to three years
Disadv:
- does not protect against STIs
- can prevent menstruation taking place

Sterilisation (female and vasectomy);
Adv:
- virtually 100% reliable
Disadv:
- difficult to reverse

78
Q

Define ‘health’ and describe the economic impact of treating disease on society

A

Health - freedom from communicable and non-communicable disease

  • Treatment of diseases is incredibly costly to society
  • unhealthy people cannot work and need to be cared for
  • billions of pounds each year are spent funding the NHS to care for and treat unhealthy people
79
Q

Define ‘communicable disease’ and describe and explain how they are caused

A

Communicable disease - a disease that can be passed from one organism to another

  • communicable diseases are caused by pathogens, which are microorganisms with the capacity to do harm
  • this includes bacteria, viruses, fungi
  • these cause diseases such as Tuberculosis, salmonella, chlamydia (bacterium), Athlete’s foot, potato blight (fungus), HIV (leading to AIDS), HPV and the Flu (virus)
80
Q

Describe some aseptic techniques and how they are used to grow colonies of bacteria in an agar (nutrient) plate

A
  • When working with microbes it is important to ensure that no unwanted or pathogenic microorganisms are cultured and can spread
  • so to avoid contamination precautions must be taken. These are called aseptic techniques and include:
  • no eating or drinking in the laboratory
  • wiping down lab benches with disinfectant
  • not culturing microorganisms at body temperature
  • using sterile, or plastic inoculating loops for transferring cultures bacteria
  • flaming the necks of culture bottles with a Bunsen Burner to prevent contamination
  • wash hands thoroughly after each step
  • clean surfaces, and apparatus using alcohol, and dispose of bacterial cultures safely by autoclaving
  • Keep Petri dish partially covered when inoculating
  • to avoid growth of pathogens, incubate at a maximum temperature of 25OC
  • incubate Petri dishes upside down to prevent condensation dripping onto cultures
81
Q

Describe some of the body’s first lines of defence against disease and explain how they do this

A

Skin - acts as a physical barrier, preventing infection of pathogens in the first place
Blood clotting - prevents infection of microorganisms through open/healing wounds
Mucous membranes - mucous in the nose and mouth traps bacteria and wafts it to the back of the throat to be coughed, sneezed, or swallowed
Stomach acid - hydrochloric acid in our stomachs is incredibly strong and is able to kill pathogens if swallowed

82
Q

Describe the body’s second line of defence against disease and the process of phagocytosis (primary immune response)

A

Lymphocytes - a type of white blood cell that recognises any pathogens as foreign and stimulates the defence mechanism
- this involves production of antibodies that are complimentary and specific to the antigens (protein markers) of the pathogen, in response to the pathogen entering the body
- these antibodies clump the pathogens together, immobilising them, and marking them for phagocytosis

Phagocytes - another type of white blood cell, involved in the second part of the body’s primary immune response
- phagocytes move to the immobilised pathogens and surround engulf and digest them in order to destroy them
- this process is known as phagocytosis
- if the person is being exposed to the pathogen for the first time it will take a few days in order for antibodies to rise to the level required for immunity: this is the primary response

83
Q

Describe what happens during the secondary immune response

A
  • memory lymphocytes are produced during the primary immune response
  • these remain in the blood for a many years in the case of a secondary infection of the same pathogen
  • they allow antibodies to be produced at a much higher level much faster, meaning the pathogen is less likely to cause a disease
84
Q

State and describe the two types of immunity

A

Active - the body produces the antibodies used to combat the pathogen
- slow acting, but lasts for a long time

Passive - when antibodies from an external source are injected into the body
- these are fast acting but only last for a short while

85
Q

Describe the structural and chemical defence mechanisms in plants against pathogens

A

Structural:
Waxy cuticle - prevents entry of microorganisms entering the plant
Thick cellulose cell wall - prevents entry of microorganisms into cells

Chemical:
- many plants produce anti-microbial chemicals to defend against pathogens
- for example mint has been shown to have this property property, as well as foxgloves, which produce a chemical called digitalis, which is poisonous to predators and destroys microbes

86
Q

Demonstrate knowledge of how Alexander Fleming discovered penicillin, and how its medical applications were developed by Florey and Chain

A
  • Penicillin was the first antibiotic to be developed
  • it was discovered in 1928 by Alexander Fleming
  • he first noticed it while culturing bacteria
  • he noticed that the culture had been contaminated by fungus, and interestingly there was little bacterial growth around the fungus
  • he concluded that the fungus was producing a substance that prevented bacteria growing, and since the fungus was called penicillium he called the substance penicillin, and the first antibiotic began development
  • Fleming began testing the penicillin on animals, but to little avail, as he was unable to synthesise a pure form of the substance
  • in the 1940s two other scientists named Howard Floret and Ernst Chain were able to purify it, and its large scale production began
87
Q

Describe how penicillin and other drugs are produced using a fermenter

A
  • the fungi are allowed to grow in a large biodigester/fermenter, where the conditions are maintained at the optimum level for fungal growth
  • then downstreaming occurs, and the antibiotic is extracted, purified and packaged for use
88
Q

Define ‘preclinical’ and ‘clinical’ trials, and give a brief description of each, including examples

A

When you new drugs are developed they have to be put through a series of tests

Preclinical - the stages before a drug is used on people
- tested on tissue samples in test tubes (in-vitro testing) as well as on animals
- used to assess the harmful side effects and the efficacy of the drug

Clinical trials - the stages where the drug is tested on humans
- once the drug is determined safe to use after the preclinical trials it is tested on human patients and other healthy volunteers
- this is done to find the optimum dosage of the drug, as underdosing can reduce the drug’s efficacy and overdosing can lead to other harmful effects and even death

89
Q

Describe the process of peer reviewing and why it is necessary

A
  • involves research papers and new discoveries being scrutinised by experts of at least equal standing to those who made the discovery
  • they then return feedback and suggest refinements wherever necessary
  • this is done to ensure the validity of the investigation and research, and also that the process of investigation is correct and thorough
90
Q

Define ‘antibiotic’ and describe how it functions, as well as how it varies to and antibody

A

Antibiotic - a chemical produced by a fungus that kill bacteria, or reduce their growth; used to fight bacterial infections

  • antibiotics combat bacteria specifically, whereas antibodies can be produced for any type of antigen
  • antibiotics are also not specific to one type of antigen and often work against a range of bacteria
  • antibiotics also do not all act in the same way, so a doctor may prescribe a different antibiotic based on the infection
91
Q

Define ‘antibiotic resistance’ and describe how it occurs, including how superbugs develop as a result

A

Antibiotic resistance - when a bacteria develops resistance to a specific, or a range of antibiotics

  • it is usually caused by overuse of antibiotics
  • this allows bacteria to mutate and become resistant to the main antibiotics
  • this results in the development of superbugs, such as MRSA, which are responsible for many serious medical conditions, and are extremely hard to treat due to their increased resistance
  • they are extremely common in hospitals, as patients often have weak immune systems, and lots of wounds for microbes to enter through
  • hospitals are also antibiotic rich environments ensuring that any bacteria that are not resistant are killed, leaving only those that are resistant, and they can reproduce
  • hospitals have thus brought in new methods in an attempt to slow down the spread of superbugs, and hopefully eradicate them, including: wearing gloves, immediate cleaning of spillages of bodily fluids, and more careful administration of antibiotics
  • patients who contract superbugs are also isolated from other patients
92
Q

Describe how vaccines work and how they reduce the risk of contracting a disease

A
  • vaccines contain dead or attenuated forms of a pathogen, which are then injected into the body
  • the attenuated pathogens still have their antigens which stimulate a primary immune response
  • eventually antibodies will be at a high enough level to provide immunity and memory lymphocytes will be produced, meaning the immune response will be a lot faster in the case of secondary infection
  • sometimes a further vaccination is needed to ensure that immunity is achieved for a reasonable amount of time; this is called the ‘booster’
93
Q

Define ‘non-communicable disease’ and describe some causes

A

Non-communicable disease - a disease that cannot be passed from one organism to another

  • can be caused by any one, or combination of, a variety of factors:
    Lifestyle;
    - poor diet — excess sugar and fat intake
    - lack of exercise — energy used in exercise being lower energy intake is what causes obesity
    - overexposure to UV radiation — causes mutation of skin cells leading to skin cancer
    - misuse of drugs;
    - alcohol - binge drinking causes liver disease and foetal alcohol syndrome if pregnant
    - tar - tar in cigarettes can cause bronchitis, emphysema and lung cancer
    - nicotine - incredibly addictive and leads to narrowing of arteries
    - carbon monoxide - has a higher affinity for haemoglobin than oxygen so takes its place in RBCs, affecting the oxygen carrying capacity of the blood and respiration

Inherited;
- genetics - some people are genetically predisposed to some cancers
- people can also be born with genetic inherited conditions, such as haemophilia

94
Q

Describe the interactions between obesity, cardiovascular disease, and Type 2 diabetes

A
  • obesity is a result of energy intake being higher than energy output
  • this is usually a result of a high sugar/fat diet
  • a high fat diet causes cholesterol to build up in the arteries, causing CHD, and other CVDs
  • a high sugar diet can also cause Type 2 diabetes
95
Q

Describe how a build up of fat in coronary arteries can lead to a cardiac arrest

A
  • a build up of cholesterol and fatty substances in the coronary artery causes a blockage (clot)
  • less oxygen and glucose can pass through and reach the heart cells
  • heart cells cannot respire and some die due to a lack of energy
  • the heart muscle has to work harder, and may begin to beat irregularly, or stop beating altogether
  • resulting in a heart attack, and possibly death
96
Q

Explain how a build up of fat in the carotid arteries can lead to a stroke

A
  • a build up of cholesterol and fatty substances in the carotid artery causes a blockage (clot)
  • less oxygen and glucose can pass through and reach the brain cells
  • brain cells cannot respire and some die due to a lack of energy
  • results in a loss of function depending on the severity of the stroke and the area of effect
  • resulting in a stroke, and possibly death
97
Q

Explain how an angioplasty is used to treat CVD

A
  • arteries that have become narrowed by cholesterol clotting can be widened using an angioplasty (balloon) attached to a stent (wire mesh)
  • the angioplasty is inflated, opening the mesh. The balloon is then deflated and extracted, but the mesh remains open
  • this keeps the lumen wide and increases blood flow to the heart cells
98
Q

State two types of heart medication and how they function in treating CVD

A

Statins - reduces blood-cholesterol levels, slowing down the rate at which arteries can become clogged
Aspirin - thins blood by making platelets less sticky, making it easier for blood to flow past blockages

99
Q

State 4 factors that increase the risk of developing CVD, and how these can be countered

A
  • lack of exercise
  • high fat diet
  • smoking
  • stress

These can be mitigated by being more active and quitting smoking

100
Q

Define ‘cancer’ and briefly describe the two types

A

Cancer - uncontrolled cell division
- leading to the development of tumours

Benign tumour - the cancer cells are encapsulated and cannot spread to a secondary location in the body

Malignant tumour - the cancer cells are in encapsulated and capable of spreading throughout the body, leading to the growth of secondary tumours
- they are much more dangerous and harder to treat than benign tumours

101
Q

Describe how lifestyle factors can affect the risk of developing certain types of cancer. Use 3 examples

A

Lung cancer - tar in cigarettes can cause lung cancer
- quitting smoking greatly reduces the risk of developing lung cancer

Skin cancer - overexposure to UV radiation can cause skin cells to mutate and cause skin cancer
- wearing sun cream when UV is high, and not staying out in the sun for prolonged periods of time can greatly reduce the risk of getting skin cancer

Cervical - cervical cancer is caused by a virus called the human papilloma virus (HPV)
- getting vaccinated against HPV will greatly reduce the risk of getting cervical cancer

102
Q

Describe two structural differences between normal cells and cancer cells

A
  • cancer cells have thicker cell membranes than normal cells
  • cancer cells have larger, more irregular nuclei than normal cells
103
Q

Describe why early detection is important in improving survival rates

A
  • early detection is important as it means the tumour:
  • it will be smaller
  • will have had less time to cause damage to the body
  • will be easier, and safer to remove
104
Q

Describe 2 common methods of early detection

A

Screening - offered commonly to older women for breast and cervical cancer
- everyone between the ages of 60 and 74 is also offered a free screening for bowel cancer

Self-examination - used to check for types of cancer outside of the body, such as:
- testicular cancer; and
- skin cancer

105
Q

Assess the advantages and disadvantages of the 4 types of cancer treatments, give a brief description of each

A

Surgery - involves removing cancer cells from the body

Adv - extremely effective against benign tumours
Disadv - ineffective if the tumour has spread, or is in an inaccessible part of the body

Radiotherapy - X-rays are used to kill cancer cells

Adv - can very accurately target small tumours anywhere in the body
Disadv - other, normal tissues may be damaged, as X-rays have to pass through them to reach the tumour

Chemotherapy - uses injection of a drug, or a range of drugs to kill cancer cells

Adv - can kill cancer anywhere in the body
Disadv - kills other fast dividing cells, leading to hair loss, and affects other types of tissue

Immunotherapy - use of lab engineered antibodies to mark cancer cells for phagocytosis, allowing the body’s immune system to take care of it

Adv - provides a targeted and specific treatment for the patient, with much less negative side effects than alternative treatments
Disadv - extremely expensive

S2 Flashcards (6 decks)

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