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Biology Model Answers Flashcards

0
Q

How does atheroma lead to an aneurysm (3)

A

Weakens artery wall (1)
So that it bursts (1)
When under high blood pressure (1)

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1
Q

Antibody (2)

A

Protein made by plasma B cells (1)

Specific to one antigen (1)

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2
Q

Antigenic variability (3)

A

Some pathogens have different strains - the antigens keep changing (1)
Shape of antigen does not correspond to antibodies formed in previous infections (1)
Therefore no appropriate memory cells to stimulate antibody production (1)
So the only means to overcoming the infection is the primary response (1)
Antigenic variation makes it difficult to develop vaccines against some pathogens e.g. Flu (1)

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3
Q

Barriers to pathogen entry (3)

A

Protective covering if the body e.g. Skin (1)
Epithelia are covered in mucus (1)
Hydrochloric acid in the stomach (1)

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4
Q

Difference between B cells and T cells (2)

A

B cells mature in bone marrow (1)

T cells mature in the thymus gland (1)

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5
Q

Effects of emphysema (6)

A

Elastin in lung tissue has been permanently stretched (1)
Lungs no longer able to force air out of alveoli (1)
Therefore lack of ventilation means concentration gradient cannot be maintained (1)
Surface area of alveoli is reduced and they sometimes burst (1)
Diffusion of gases is less efficient (1)
I.e. rate of diffusion is lower (1)

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6
Q

Differences between specific and non-specific response (4)

A

Non-specific mechanism do not distinguish between one type of pathogen and another but responds in the same way (1)
E.g. Barrier to entry of pathogens or phagocytosis (1)
Specific mechanism distinguish between different types of pathogen and provide longer lasting immunity (1)
E.g. Cell mediated response involving T lymphocytes or humoral response involving B lymphocytes (1)

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7
Q

Course of TB (6)

A

Transmitted in water droplets in the air (1)
Bacteria grow in upper regions of lungs where there is a plentiful supply of oxygen (1)
White blood cells accumulate at site of infection (1)
Bacteria are engulfed by phagocytes (1)
Bacteria become encased by tubercles (1)
Bacteria can lie dormant which means that they are not replicating (1)
Leads to inflammation and enlargement of lymph nodes (1)
Years later bacteria may reemerge to cause a second infection - they are activated when a person is immunosuppressed (1)
Bacteria can destroy lung tissue which can result it cavities and scar tissue which can led to fibrosis (1)
Damage to alveoli increases diffusion distance and decrease surfaces area (1)
Sufferers can cough up damaged tissue with blood (1)
Bacteria can enter blood and spread to other organs (1)

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8
Q

Key events of humoral immunity (7)

A

Surface antigens of invaded pathogen are taken up by macrophage (1)
Macrophage process the non self antigens and display them on their own self surface membrane ( antigen presentation ) (1)
T helper cells attach to the processed antigens on the macrophage and activate them (1)
B cells are activated to divide by mitosis to produce plasma cell clones (1)
Clone plasma cells produce antibodies complementary to antigens on pathogen surface (1)
Antibodies attach to antigens and destroy them (primary response) (1)
Some B cells develop into memory cells and can respond to future infections ( secondary response ) (1)

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9
Q

How are memory cells important in immunity by vaccination (4)

A

Memory cells are stored from previous infection (1)
So when there is contact with the same antigen (1)
There is a more rapid response with more antibodies (1)
That destroy the pathogen before it causes harm (1)
More rapid because does not have to go through the process of colonial selection and clonal expansion (1)

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10
Q

Explain why these are referred to as monoclonal (1)

A

They are antibodies that are produced from a single clone of B (plasma) cells (1)

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11
Q

Why does an antibody only react with one type of antigen (3)

A

Antibody is a binding site with a specific tertiary structure (1)
Antigen is complementary to the binding site (1)
Antigen binds to the antibody to form an antibody- antigen complex (1)

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12
Q

What is an antigen (2)

A

Protein molecule found on surface of a cell (1)

That causes T or B cell production/ antibody production (1)

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13
Q

Key events of cell mediated immunity (6)

A

Pathogens are taken in by antigen presenting cells e.g. Phagocytes (1)
Phagocyte presents antigens from the pathogen in its cell surface membrane (1)
Receptor on certain T helper cells fit exactly onto these antigens (1)
This activates other T cells to divide rapidly by mitosis and form a clone (1)
Cloned T cells can then develop into memory cells (1)
Or stimulate phagocytes to engulf pathogens by phagocytosis; simulates T cell to divide; kill infected cells (1)

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14
Q

Process of phagocytosis (6)

A

Chemical product of the pathogen acts as an attractant, causing phagocytes to move towards the pathogen (1)
Phagocytes attach themselves to the pathogen surface (1)
Phagocytes engulf pathogen to form a vesicle- phagosome (1)
Lysosomes move towards the vesicle and fuse with it (1)
Enzymes within the lysosomes break down pathogen by hydrolysis (1)
Soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocytes (1)

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15
Q

Why tests involving monoclonal antibodies are specific (3)

A

They have specific sequence of amino acid in their primary structure (1)
So this generates a specific tertiary structure (1)
Only bind to antigens that have a complementary shape (1)

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16
Q

What is a vaccine (2)

A 
A weakened (attenuated) form of a pathogen/ microorganism (1)
That stimulates the production of antibodies / plasma cells / memory cells (1)
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17
Q

Ways in which pathogens cause disease (2)

A 
Produces toxins (1)
Causes damage to cells and tissues e.g. Rupturing, breaking down, replicating (1)
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18
Q

Production of monoclonal antibodies (6)

A

Mouse is exposed to non self material (1)
B cells in mouse produce mixture and polyclonal antibodies, which are then extracted from the spleen (1)
These are mixed with cells that can rapidly divide outside the mouses body e.g. Tumour cells. This enables the B cells to divide (1)
Detergent is added to break down cell membranes and enable fusion (1)
Few cells are separated and each single cell is cultured form a clone (1)
Any clone producing the required antibodies grown on a large scale antibodies are extracted from the growth medium (1)

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19
Q

Functions if monoclonal antibodies (4)

A

Separation of a chemical from a mixture (1)
Immunoassay e.g. Pregnancy tests (1)
Cancer treatment (1)
Transplant surgery (1)

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20
Q

How smoking increases risk of developing coronary heart disease (4)

A

Smoking increases risk of clotting (1)
Nicotine causes platelets to stick together (1)
Carbon monoxide is associated with the risk of plaque formation (1)
Which reduces the elasticity of the arteries (1)
Carbon monoxide combines with haemoglobin and reduces amount of oxygen transported in the blood therefore less oxygen to the heart (1)

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21
Q

How high blood pressure affects arteries (2)

A

Muscle in artery wall becomes thicker (1)

Can lead to an aneurysm (1)

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22
Q

Roles of valves in control of blood flow (3)

A

Atrioventricular valves prevent back flow of blood when ventricular pressure exceeds atrial pressure (1)
Semi lunar valves prevent back flow when recoil action of arteries creates greater pressure than in ventricles (1)
Pocket valves in the veins ensure blood flows back to the heart when veins are squeezed e.g. During muscle contractions (1)

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23
Q

What is atheroma (2)

A

Build up of lipoproteins, white blood cells and cholesterol (1)
In artery wall under endothelial lining (1)

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24
Q

Coordinating heartbeats (7)

A

Sino atrial node (1)
Sends out a wave of electrical activity causes atria to contract (1)
Electrical activity is delayed by atrioventricular node (1)
To allow blood to move into ventricles (1)
Before they contract. Electrical activity passed down he bundle of His (1)
So ventricles contract from bottom up (1)
To ensure all blood is ejected from ventricles (1)

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25
Q

Events of the cardiac cycle (11)

A

Atria contracts (atrial systole) (1)
Increased pressure in the atria (1)
Atrioventricular valves open (when pressure in atria is higher than pressure in ventricles) (1)
Blood flows into ventricles (1)
Atrioventricular valves shut ( when pressure in the ventricles is higher than the pressure in the atria) (1)
Ventricles contract (ventricular systole) (1)
Increased pressure in ventricles ( biggest difference) (1)
Semi lunar valves open ( when pressure in the ventricles is greater than the pressure in the arteries ) (1)
Blood moves into the arteries fast at first ( rapid ejection) and then more slowly (1)
Semi lunar valves close ( when pressure in the arteries is higher than the pressure in the ventricles ) (1)
Diastole ( heart relaxes and atria accepts more blood from the veins) (1)

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26
Q

Why may atheroma lead to blood clots (2)

A 
Narrows arteries (1)
Causes uneven blood flow (1)
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27
Q

Increased temperature and reaction rate (4)

A

Particles have more kinetic energy (1)
Therefore they move more (1)
So there are more collisions (1)
So more enzyme-substrate complexes form (1)

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28
Q

How high blood cholesterol increases the risk of devolving coronary heart disease (4)

A

Fatty deposits on wall of arteries (1)
Damages endothelium (1)
Narrows lumen (1)
Can lead to blood clots (1)

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29
Q

How atheroma is caused and how it may lead in myocardial infarction (6)

A

Antheroma forms in artery wall (Ldl’s, white blood cells, cholesterol under endothelial lining) (1)
Antheroma may narrow lumen of artery (1)
Antheroma promotes clotting and increase blood pressure (1)
Blood clot may lodge in coronary artery (1)
There is a reduced blood supply to heart muscle (1)
Reduced oxygen or glucose supply leads to cells death due to cells inability to respire aerobically (1)

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30
Q

Explanation of the symptoms of pulmonary fibrosis (4)

A

Shortness of breath due to a considerable volume of lungs being occupied by fibrous tissues (thickened epithelium means diffusion pathway is increased) (1)
Chronic dry cough because fibrous tissue creates an obstruction in the airways (1)
Pain and discomfort in chest are the consequence of pressure and scarring due to coughing (1)
Weakness and fatigue result from reduced intake of oxygen in the blood (1)

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31
Q

Explain how ventilation maintains a concentration gradient (3)

A

Air high in oxygen is continuously entering the alveoli (1)
Air low in oxygen is continuously being removed from the alveoli (1)
Blood high in oxygen is removed (1)

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32
Q

Explain how paralysis of diaphragm leads to breathing difficulties (2)

A

Diaphragm will not flatten (1)

So lung volume will not increase (1)

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33
Q

Expiration (5)

A 
Intercostal muscles relax (1)
Ribs move down and in (1)
Diaphragm returns to dome shape (1)
Volume decreases (1)
Pressure increases relative to atmospheric pressure so air moves out (1)
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34
Q

Adaptations of human lungs in relation to Fick’s law (6)

A

Small diffusion pathway (1)
Caused by thin squamous epithelial cells (1)
Large concentration gradient (1)
Caused by constant removal of oxygen by the blood and constant renewal of oxygen in the alveoli (1)
Large surface area (1)
Caused by numerous, small alveoli (1)

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35
Q

Explanation of symptoms of emphysema (3)

A

Shortness of breath resulting from difficulty in inhaling due to loss of elasticity in the lungs (1)
Chronic cough due to body’s effort to remove damaged tissue (1)
Bluish skin coloration is due to low levels of oxygen in blood as a result of poor gas exchange (1)

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36
Q

Explain why during and asthma attack less oxygen diffuses into the blood (4)

A

Bronchioles restricted (1)
Air in alveoli is not replaced so less oxygen (1)
Concentration gradient is not maintained (1)
Rate of oxygen diffusion is lower (1)

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37
Q

Describe the pathway of oxygen from an alveolus to the blood (3)

A

Diffuses (1)
Through the alveolar epithelium (1)
Into blood via the capillary endothelium (1)

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38
Q

Effects of allergies in asthma (6)

A

Allergens cause white blood cells lining the bronchioles to release histamines (1)
Lining of airways become inflamed (1)
Cells of epithelial lining secretes large quantities of mucus (1)
Fluid leaves capillaries and enters airways (1)
Muscles surrounding bronchioles contract and constrict airways (1)
Therefore lack of ventilation means concentration gradient for the diffusion of oxygen is not removed (1)

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39
Q

Explanation if symptoms of asthma (4)

A

Difficulty in breathing due to constriction of bronchioles (1)
Wheezing sound caused by air passing through restricted bronchioles (1)
Tight feeling in the chest is a consequence of not being able to ventilate the lungs adequately (1)
Coughing is a reflex response to obstructed bronchioles (1)

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40
Q

Effects of pulmonary fibrosis (4)

A 
Elastin may be destroyed so lungs no longer able to force air out of alveoli (1)
Therefore lack of ventilation mans the concentration gradient cannot be maintained (1)
Scar tissue (1)
Increases length of diffusion pathway (1)
41
Q

Test for starch (2)

A

Add iodine in potassium iodide solution (1)

Colour from brown to blue-black (1)

42
Q

Inspiration (5)

A

Intercostal muscles contract (1)
Ribs move up and out (1)
Diaphragm muscles contract and the diaphragm flattens (1)
Volume increase (1)
Pressure decreases relative to atmospheric pressure so air moves in (1)

43
Q

How lactose intolerance causes diarrhoea (3)

A 
Undigested lactose in small intestines causes water potential to become more negative (1)
Water moves from epithelial cells into lumen (1)
By osmosis (1)
44
Q

Activation energy (2)

A

The minimum amount of energy required to bring particles in close contact (1)
So that they will collide and react (1)

45
Q

Test for non-reducing sugars (3)

A

Heat with Benedicts reagent and no colour change (1)
Boil with dilute HCl and then neutralise with NaHCO3 (1)
Reheat with Benedicts reagent and colour change from blue to brick-red (1)

46
Q

Competitive enzyme inhibitor (4)

A

Inhibitor has a similar shape to the substrate (1)
Binds competitively for the active site (1)
As it has a complementary shape (1)
Therefore enzyme-substrate complexes can no longer form (1)

47
Q

Induced fit model (2)

A

The substrate has a complementary shape to the active site of the enzyme (1)
Upon binding the active site of the enzyme moulds around the substrate (1)

48
Q

Protein structure (6)

A

Amino acids join together as primary structure (1)
By a condensation reaction (1)
Forming peptide bonds; specific structures form during secondary folding - alpha helix and beta pleated sheet (1)
Hydrogen bonds form between O and H atoms (1)
Secondary structure further folds to form tertiary structure held together by ionic and disulphides bonds (1)
Quaternary structure is where more than one polypeptide chain folds together e.g. Haemoglobin (1)

49
Q

Explain why people with lung disease may get easily tired (5)

A 
Slow rate of oxygen diffusion (1)
Less oxygen in blood (1)
Less delivered to cells for respiration (1)
Less ATP is produced (1)
Less muscles contractions (1)
50
Q

Test for reducing sugars (2)

A

Heat with Bendicts reagent (1)

Colour change from blue to brick-red (1)

51
Q

Adaptions of micro villi for efficient diffusion (4)

A

Increase surface area (1)
Thin walled therefore reduce length of diffusion pathway (1)
Able to move and so maintain a concentration gradient (1)
Well supplied with blood vessels to maintain a concentration gradient (circulation of blood) (1)

52
Q

Enzyme Denaturation (5)

A

Heat above the optimum to break hydrogen bonds (1)
This causes the tertiary structure to unfold (1)
Active site is distorted/ changes shape (1)
Substrate can no longer bind to active site (1)
Fewer enzyme-substrate complexes form (1)

53
Q

Lock and key theory (3)

A

Enzyme have an active site of specific shape (1)
The substrate that is a complementary shape (1)
Binds to the active site (1)

54
Q

Non-competitive enzyme inhibitor (4)

A

Inhibitor binds to regulatory region as it does not have a complementary shape to the active site (1)
This causes a conformational change in the shape of the active site (1)
Meaning the substrate can no longer bind (1)
Therefore enzyme-substrate complexes can no longer form (1)

55
Q

Calculating the size of organelles when given magnification (2)

A

Measure the organelle in mm and convert to micrometers or nm (1)
Divide by the magnification (1)

56
Q

Test for protein (2)

A

Add biuret reagent to the sampe and add NaOH and CuOH to neutralise (1)
Colour change to form a lilac band (1)

57
Q

Co-transport of glucose (7)

A

Na+ ions actively pumped out of epithelial cells by sodium - potassium pump (1)
Into blood (1)
Maintaining a low concentration of sodium in the cell (1)
Glucose moves into cell with sodium (1)
Via membrane protein- this is co-transport (1)
Glucose moves from cells into blood (1)
By facilitated diffusion (1)

58
Q

Emulsion test for lipids (2)

A

Add ethanol and shake (1)

Add water and goes milky (1)

59
Q

Effects of changes on pH on enzyme activity (4)

A

Ionic bonds holding the tertiary structure break (1)
Active site distorts and substrate no longer binds to active site (1)
Charges in amino acids in active site affected (1)
Fewer enzyme-substrate complexes form (1)

60
Q

Oral rehydration therapy (2)

A

Contains water to rehydrate the tissues (1)

Electrolytes to rebalance the osmotic potential (1)

61
Q

Explain why ORT replaces water lost (4)

A

Encourages cells to uptake sodium and glucose (1)
Water potential in cells becomes more negative (1)
Water moves from small intestines back into cell (1)
By osmosis (1)

62
Q

What is the purpose of a control experiment? (1)

A

To ensure that any change in the results is due to the changing (independent) variable and nothing else. (1)

63
Q

Why some cells may have lots of mitochondria (3)

A

Mitochondria produce ATP (1)
By respiration (1)
Energy release is used for muscle contractions, active transport and nerve impulse (1)

64
Q

Use of ice cole, isotonic, buffer solution in cell fractionation (3)

A

Ice cold to slow down enzyme activity or prevent self digestion by enzymes in lysosomes (1)
Isotonic to prevent water movement by osmosis (1)
Buffer solution to prevent changes in pH that may affect protein structure (1)

65
Q

How cholera causes diarrhoea (3)

A 
Water potential in lumen is more negative (1)
Water moves from epithelial calls into lumen (1)
By osmosis (1)
66
Q

Fick’s law (2)

A

The rate if diffusion is proportional to surface area x concentration gradient (1)
Divided by thickness (1)

67
Q

Mechanisms of cholera infection (6)

A

Bacteria enters body via contaminated water, some bacteria may survive the acidic conditions of stomach (1)
Bacterium propels through the lining of small intestine using flagellum (1)
Bacterium secretes a protein that binds to receptors on surface of epithelial cells (1)
Bacterium also secretes a toxic protein that interferes with chloride channels (1)
Chloride ions flood lumen making the water potential more negative (1)
Water moves from epithelial cells to lumen via osmosis causing diarrhoea (1)

68
Q

Osmosis (4)

A

Movement of water (1)
From an area of less negative water potential to an area of more negative water potential (1)
Across a selectively permeable membrane (1)
Down a concentration gradient (1)

69
Q

Pros and cons of transmission microscopes (7)

A 
Small objects can be seen (1)
High resolution (1)
As wavelengths of electrons are short (1)
Living cells cannot be seen (1)
Carried out in a vacuum (1)
Specimen has to be very thin (1)
Artefacts may be produced (1)
70
Q

How to set up a control experiment (2)

A

Remove the factor that is being changed e.g. Placebo drug or for an enzyme reaction either a denature enzyme or distilled water should be used. (1)
Keep everything else the same. (1)

71
Q

What is an exotoxins (1)

A

A toxic protein secreted by bacteria (1)

72
Q

Not being able to see small organelles with optical microscope (2)

A

Resolution is too poor (1)

Wavelength of light is too long (1)

73
Q

How starch digestion occurs in the human body (6)

A 
Salivary amylase (1)
Breaks down starch to maltose (1)
Maltase (1)
Breaks down maltose to glucose (1)
This is hydrolysed (1)
Enzymes catalyse the breakdown of the glycosidic bond (1)
74
Q

How to find water potential the same value as the tissue used (2)

A

Plot a graph of results and draw a line of best fit (1)

Find the concentration where the ratio is one or there is no change in mass (1)

75
Q

Estimating the size of a cell/ organelle when given no figures (2)

A

Measure length with eyepiece scale (1)
Calibrated against something of known and uniform length (1)
E.g. Red blood cell

76
Q

Calculating magnification with a given scale bar (2)

A

Measure the scale bar in mm and convert to micrometers or nm (1)
Divide by the given number on the scale bar (1)

77
Q

Explain why isotonic solution is used (2)

A

Prevents net movement of water in or out of the organelle by osmosis (1)
So organelle does not shrivel or burst (1)

78
Q

Why is tissue homogenised? (1)

A

To release cell contents (1)

79
Q

Why cholera protein binds receptors on small intestine (2)

A

Protein is a complementary shape (1)

To the specific tertiary structure of the receptor protein (1)

80
Q

Describe how prokaryotes are different from eukaryotes (9)

A 
Prokaryotes have a loop of DNA (no nucleus) (1)
No mitochondria (1)
No Golgi (1)
No endoplasmic reticulum  (1)
Have smaller 70 s ribosomes (1)
Have capsule (1) 
Have flagellum (1) 
Have plasmids (1) 
Have a cell wall made of murein (1)
81
Q

Deference between types of diffusion and active transport (3)

A

Diffusion is net movement of solutes from high to low concentration (1)
Facilitated diffusion is transport of large or charged particles through membrane protein (1)
Active transport is net movement of molecules against a concentration gradient that requires energy in the form of ATP and carrier proteins (1)

82
Q

Why electron microscope are better for viewing small objects (2)

A

Resolution is higher (1)

As electrons have shorter wavelengths (1)

83
Q

Mitochondria

A

Double membrane which controls entering and exit
Cristae - which is the inner membrane providing large surface area for attachment of enzymes involved in respiration
Matrix - semi rigid material contains enzymes involved in respiration

84
Q

Molecules of transport (3)

A

Ions are transport by channel proteins (1)
Big molecules are transported by carrier protein (1)
Active transport uses only carrier protein (1)

85
Q

Advantage of expressing results as a ratio (2)

A

Allows comparison. (1)

As they have different starting values. (1)

86
Q

Points to consider for evaluation questions (how science works) (6)

A

Sample size- may not be representative. (1)
Repeats- identifying anomalies may be hard. (1)
Scientists may have vested interest to present results in a biased way. (1)
Results may not have been peer reviewed by other scientists. (1)
Experiment relating to human disease may have not been carried out on humans. (1)
A control experiment may not have been carried out. (1)

87
Q

Calculating percentage decrease (1)

A

((Original value➖new value) ➗ original value) ✖100

88
Q

What is correlation? (1)

A

When a change in one or two variable is reflected by a change in the other variable. (1)

89
Q

Standard deviation (2)

A

The biggest value plus or minus mean, the greater the standard deviation so the more variation there is in the data. (1)
The smaller the value plus or minus mean, the lower the standard deviation so the less variation there is in the data. (1)

90
Q

Critically analysing data on disease e.g. Drinking excessive alcohol CAUSES breast cancer… (2)

A

An established correlation is not the same as a causal link (1)
Other factors may be involved e.g. Temperature (1)

91
Q

Calculating percentage increase (1)

A

((Original value➖new value) ➗new value)✖100

92
Q

Suggest why certain protein/enzyme dugs cannot be taken orally (1)

A

Proteins may be digested/ broken down by enzymes (1)

Protein may be denatured by the stomach acid (1)

93
Q

How to improve reliability of results. (2)

A

Allows anomalies to be identified (1)

Allows calculation of a more reliable mean. (1)

94
Q

Define risk in terms of health (1)

A

A measure of the probability that damage to health will occur as a result of a given hazard. (1)

95
Q

How taking additional readings can improve a graph. (2)

A

Line of best fit may be more reliable. (1)
Point where the line crosses may be more reliable. (1)
Error bars could be plotted. (1)
To show variability about the mean. (1)

96
Q

What is in the nucleus and functions

A

Nuclear envelope - controls entry and exit of materials in or out the nucleus and contains reactions taken place within them
Nuclear pore - allows passage of large molecules like copies of DNA
Nucleoplasm - granular jelly like material which makes up the bulk of the nucleus
Chromatin - DNA found within the nucleoplasm
Nucleolus - manufactures ribosomal RNA and assembles the ribosomes

97
Q

Roles of lipids

A

Water proofing
Source of energy
Insulation
Source of protection

98
Q

Pulmonary ventilation is

A

Pulmonary ventilation ( dm^3 min^-1 )= tidal volume ( dm^3 ) ✖ ventilation rate (min^-1)

99
Q

Calculating cardiac output

A

Cardiac output ( dm^3 min ^-1) = stroke volume ✖ heart rate

100
Q

Diet cause heat disease because (well not cause but you know what is meant)

A

High level of salt - raise blood pressure

High saturated fats – increase LDL and increase loos cholesterol concentration

All Subjects (30 decks)

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