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AS Biology > PPQs > Flashcards

PPQs Flashcards

1
Q

Explain why antibiotics do not affect viruses

A
  1. Only work on bacteria
  2. Act on cell structures viruses do not have (cell surface membrane/cell wall)
  3. Out of reach as viruses live in host cells
  4. Can only work on living cells
  5. Cannot act on protein coat/capsid/capsomere
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2
Q

Outline how a monoclonal antibody is produced

A
  1. Inject mouse with antigen
  2. Leave mouse for a few weeks to allow an immune response to occur
  3. Extract B lymphocytes
  4. Fuse B lymphocyte with myeloma cell using fusogen
  5. Hybridoma cell produced
  6. Screening to select hybridoma cells that are secreting the correct antibody
  7. Large scale production (fermenter)
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3
Q

Explain why a particular amino acid needs to be linked to a specific tRNA molecule

A
  1. Translation
  2. Amino acid carried by tRNA to ribosome
  3. Anticodon binds to codon
  4. tRNA brings amino acids next to each other
  5. Peptide bond forms
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4
Q

Explain how the structure of an enzyme would be affected by pH when it is too acidic

A
  1. Hydrogen/ionic bonds broken
  2. Change tertiary structure
  3. Shape of active site altered
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5
Q

Explain the induced fit mechanism

A
  1. Active site of enzyme and substrate are not fully complementary
  2. Substrate enters the active site
  3. Active site is partially flexible
  4. Enzyme provides better fit by active site moulding around substrate
  5. Allows for interaction of R groups of active site with substrate
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6
Q

Describe/explain transpiration

A
  1. Stomata opens for diffusion of carbon dioxide into the plant
  2. Carbon dioxide is required for photosynthesis
  3. Water vapour evaporates and diffuses out of plant
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7
Q

Explain how hydrogen bonding is involved in the movement of water in the xylem

A
  1. Adhesion- binding of water molecules to cellulose of cell wall
  2. Hydrophilic property of cellulose fibres allows for binding
  3. Cohesion- binding of water molecules to each other
  4. Allows for continuous water column to be produced without breaking
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8
Q

Describe the roles of spindle fibres during mitosis

A
  1. Attach to kinetochores/centromeres during prophase
  2. Attach to centrioles
  3. Arrange chromosomes at equator
  4. Contract to pull daughter chromatids to opposite poles
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9
Q

Explain why it is necessary for athletes to increase the concentration of haemoglobin in their blood when acclimatising to high altitude

A
  1. At high altitude there is a low partial pressure of oxygen
  2. Less oxygen in inhaled air
  3. Haemoglobin has a lower affinity for oxygen, lower oxygen saturation
  4. Compensation required- increased number of RBCs so that the same volume of oxygen can be transported in the blood as at sea level
  5. Volume of oxygen transported in the blood is less
  6. Lack of oxygen reduces aerobic respiration and increases anaerobic respiration
  7. Could lead to fatigue, altitude sickness
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10
Q

State what is meant by the term fluid mosaic

A

Fluid- phospholipids and proteins are able to move
Mosaic- proteins and glycoproteins are scattered within the bilayer

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11
Q

Explain what is meant be closed double circulation

A
  1. Closed- blood is contained within the blood vessels
  2. Double circulation- systemic and pulmonary circulation
  3. Double circulation- blood passes through the heart twice in one circulation
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12
Q

Describe the process of gas exchange between the alveolus and the blood

A
  1. Carbon dioxide diffuses from blood to alveolus, oxygen diffuses from alveolus to blood
  2. Diffusion- net movement of oxygen from an area of high concentration to an area of low concentration, down the concentration gradient
  3. Across squamous epithelial cells of alveolar wall and endothelial cells of capillary wall
  4. Oxygen diffuses into RBC
  5. Steep concentration gradient is maintained by ventilation
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13
Q

Outline the features of facilitated diffusion of glucose molecules

A
  1. Carrier protein
  2. Specific protein with specific binding site
  3. Glucose binds to binding site causing a conformational change
  4. Passive process, no ATP is required
  5. Movement occurs down concentration gradient
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14
Q

Describe the structure of the chromosome in late prophase

A
  1. Two identical sister chromatids joined by centromere
  2. DNA complexed with protein
  3. Histone proteins
  4. Telomeres at the end of chromatids
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15
Q

Suggest how cytokinin acts as a cell signalling molecule

A
  1. Cytokinin acts as a target cell
  2. Binds to receptor, receptor is specific and complementary to cytokinin
  3. Receptor is located in cell surface membrane
  4. Sets off response in the cell (eg enzyme activated, triggers secondary messenger
  5. Acts extracellularly
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16
Q

Explain what is meant by a gene

A

A section of DNA that codes or a polypeptide (sequence of amino acids)

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17
Q

Outline how a mutation leads to the formation of an altered polypeptide where one amino acid is replaced by a different amino acid

A
  1. Base sequence altered
  2. Base substitution
  3. mRNA synthesised during transcription
  4. Mutation leads to altered mRNA
  5. Only one mRNA codon is changed
  6. tRNA has a different anticodon
  7. tRNA brings a different amino acid to ribosome
  8. Complementary anticodon binds to codon
18
Q

State two differences between the chromosomes at metaphase and the chromosome at late anaphase

A

Metaphase- singular chromosome of two sister chromatids
Anaphase- two separated chromatids

Metaphase- two DNA molecules
Anaphase- One DNA molecule

Metaphase- chromatids are joined at the centromere
Anaphase- chromatids are separated

19
Q

Describe the appearance of the lining of the bronchus in a long term smoker

A
  1. Shorter, fewer cilia present
  2. Undifferentiated cells
  3. Flattened epithelium/squamous cells
  4. Scar tissue forms
  5. Enlarged goblet cells
  6. Excess mucus secreted
  7. Tar deposits
  8. Phagocytes
  9. Inflammation of bronchial lining
20
Q

Explain what is meant by the term non self antigens

A

Non self- foreign, not from the person’s own body —> causes immune response
Antigen- protein/glycoprotein that is complementary to the antibody

21
Q

Describe the function of phloem sieve tubes

A

Transport of assimilates from source to sink via translocation/mass flow

22
Q

Explain how the structure of the walls of xylem vessel elements are adapted to their functions

A
  1. Lignin for waterproofing
  2. Lignin for support to prevent inward collapse
  3. Cellulose/hydrophilic regions of lignin allow for the adhesion of water (h bonds)
  4. Pits for lateral movement of water
  5. Rings/spirals for extension/growth
23
Q

Suggest why multicellular animals require transport systems

A
  1. Diffusion occurs too slowly, cannot satisfy needs
  2. Longer distances to reach some cells
  3. Takes minerals closer to cells
24
Q

Describe how TB is transmitted

A
  1. Uninfected person inhales airborne droplets produced by infected person
  2. Eg, from sneezing/coughing
  3. M.tuberculosis is present in airborne droplets
25
Q

Outline how antibiotic resistance has occured

A
  1. Incomplete treatment, course not completed
  2. Not all bacteria has been killed, some have survived (bacteria reservoirs)
  3. Mutation
  4. Resistant bacteria selected for
  5. Resistant bacteria reproduce through vertical transmission
  6. Death of non resistant bacteria
  7. Horizontal transmission
26
Q

Explain what is meant by transcription

A

Production of mRNA from a sequence of nucleotides

27
Q

Outline the steps that can be taken to reduce the impact of drug resistance in bacteria

A
  1. Take antibiotics only when necessary
  2. Ensure that the effective antibiotic is prescribed
  3. Complete course
  4. Use antibacterials
  5. Break transmission cycle
  6. Develop new antibiotics
  7. Reduce the use of antibiotics in agriculture
28
Q

Explain the difference in thickness between muscle walls of the right and left ventricles

A
  1. Left ventricle is thicker
  2. Systemic circulation, pumps blood around the body
  3. Requires higher pressure to overcome resistance
  4. Higher pressure requires more muscular force
  5. Right ventricle transports blood to the lungs
  6. Needs to be of low pressure to prevent pulmonary capillaries from bursting
  7. High pressure unnecessary due to lower resistance in the lungs
29
Q

Describe the roles of centrioles in mitosis

A
  1. Organises microtubules
  2. Forms spindle fibres
  3. Contraction of spindle fibres at anaphase to separate sister chromatids
  4. Make microtubules
30
Q

Explain why sodium ions do not cross cell surface membrane by simple diffusion

A
  1. Sodium ions are charged/hydrophilic
  2. Unable to pass through hydrophobic core of phospholipid bilayer
  3. Must pass through transport proteins (carrier and channel)
  4. Active transport only way to move sodium ions against concentration gradient
31
Q

Define transpiration

A

Loss of water vapour from the leaves

32
Q

State and explain two experimental factors that affect the rate of transpiration

A

Factor: temperature
Explanation: high temperature increases the rate of evaporation from spongy mesophyll cell surfaces and diffusion of water vapour from the stomata

Factor: humidity
Explanation: high humidity will decrease the rate of transpiration due to a less steep water potential gradient

Factor: wind speed
Explanation: high wind speed with increase the rate of transpiration due to a steeper water potential gradient

Factor: water availability
Explanation: reduced water available will cause the stomata to close so reduced rate of diffusion/ more water available will create a steeper concentration gradient between roots and leaves

Factor: light intensity
Explanation: higher light intensity will increase the rate of transpiration as the stomata will open more widely

33
Q

Explain how hydrogen bonding is involved in the movement of water through the xylem

A

Transpiration stream/pull:
Cohesion- water molecules can bind to each other to create a continuous column of water

Adhesion- water molecules can bind to the cellulose fibres and hydrophilic regions of the xylem

34
Q

Explain the mode of action of an enzyme that uses the induced fit mechanism

A
  1. Substrate and active site are not fully complementary
  2. The active site is partially flexible
  3. The active site moulds around the substrate when binding occurs
  4. So that the active site and substrate are now complementary
  5. Allows the formation of an enzyme substrate complex
35
Q

Describe how cholera is transmitted from an infected person to an uninfected person

A
  1. Faecal-oral route
  2. Infected person defalcates
  3. Faeces containing V.cholerae contaminates food supply/water supply
  4. Uninfected person consumes contaminated food supply/drinks unsanitised water
36
Q

Explain how a substitution mutation could result in a change in the amino acid sequence of a polypeptide

A
  1. Different mRNA codon formed during transcription
  2. Different tRNA with different amino acid binds to ribosome
  3. Each codon specifies a particular amino acid
37
Q

Suggest how a change in the amino acid sequence of an enzyme results in antibiotic resistance

A
  1. Change in tertiary and quaternary structure
  2. Enzyme binding site for antibiotic changes shape
  3. Antibiotic cannot bind so the enzyme remains active
38
Q

Suggest how the binding of as monoclonal antibody to the diseased cells causes their destruction by cells of the person’s immune system

A
  1. The monoclonal antibody is recognised as non self/foreign
  2. Triggers and immune response
  3. Macrophages engulf the diseases cells with monoclonal antibody attached
  4. APC activates B lymphocytes and T lymphocytes
  5. Clonal selection and clonal expansion
  6. Differentiation of B lymphocytes into plasma cells and memory cells
  7. Plasma cells secrete antibodies that are complementary to the monoclonal antibody
  8. Antibody binds to monoclonal antibody to lead to cell destruction
  9. T helper cells activate T killer cells
  10. T killer cells secrete perforin/hydrogen peroxide which punch holes in the cell wall
39
Q

Explain the term autoimmune disease

A

Failure to distinguish between self and non self antigens

40
Q

Describe and explain how smoking can lead to an increased risk of bacterial infection

A
  1. Fewer cilia
  2. Scar tissue replaces ciliated epithelial cells
  3. Goblet cells enlarged
  4. More mucus secreted, mucus traps bacteria
  5. Mucus is not removed by cilia action so the trapped bacteria remain for longer
  6. Bacteria multiply/increased bacterial population growth
  7. Increased chance of infection
41
Q

Describe what causes oxygen to be released from oxyhaemoglobin as blood flows through respiring tissues

A
  1. Oxygen is used up during aerobic respiration in the tissues
  2. Lower partial pressure of oxygen
  3. Allosteric mechanism
  4. Small decrease in partial pressure leads to a larger dissociation of oxygen
  5. Decrease in haemoglobin affinity or oxygen so oxygen is released
  6. Higher partial pressure of CO2
  7. H+ combines with haemoglobin to cause oxygen release
42
Q

Explain why red blood cells are in the blood but not in the tissue fluid

A

Too large to pass through endothelial pores or capillary walls

AS Biology (5 decks)

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